阅读说明：本技术 一种用于高速轧制大盘重Ti-6Al-4V合金盘条的方坯及其制备方法 (Square billet for rolling large-coil-weight Ti-6Al-4V alloy wire rod at high speed and preparation method thereof ) 是由 钟海 黄海广 李金刚 肖永江 姜浩 杨超 黄晓慧 张浩泽 余堃 高荣 于 2020-11-16 设计创作，主要内容包括：本发明涉及一种用于高速轧制大盘重Ti-6Al-4V合金盘条的方坯及其制备方法,属于冶金技术领域。该方法包括包合金包、电极压制、焊接一次电极、一次装炉及抽真空、一次炉内焊接及抽真空、一次引弧熔炼及冷却、清洗平头、焊接二次电极、二次装炉及抽真空、二次炉内焊接及抽真空、二次引弧熔炼及冷却、扒皮、加热及锻造等十数个步骤。本发明方法生产的合金方坯为锻态,内部晶粒经锻造后在一定程度上得以细化,组织性能也得以优化,且成材率高达95%,生产效率也得以提高,轧制出的钛合金盘条表面缺陷较少,整体性能优于原来采用机加工方法所生产的盘条性能。(The invention relates to a square billet for rolling a Ti-6Al-4V alloy wire rod with a large coil weight at a high speed and a preparation method thereof, belonging to the technical field of metallurgy. The method comprises the ten steps of alloy cladding, electrode pressing, welding of a primary electrode, primary furnace charging and vacuumizing, welding and vacuumizing in the primary furnace, primary arc striking smelting and cooling, flat head cleaning, welding of a secondary electrode, secondary furnace charging and vacuumizing, secondary furnace welding and vacuumizing, secondary arc striking smelting and cooling, peeling, heating and forging and the like. The alloy square billet produced by the method is in a forging state, internal crystal grains are refined to a certain extent after forging, the structure performance is optimized, the yield is up to 95%, the production efficiency is improved, the surface defects of the rolled titanium alloy wire rod are fewer, and the overall performance is superior to that of the original wire rod produced by a machining method.)

1. A preparation method of a square billet for rolling a large-coil-weight Ti-6Al-4V alloy wire rod at a high speed is characterized by comprising the following steps:

step (1), alloy coating: nominal chemical composition of TC4 alloy preparation raw materials; wherein, the mass percent of Al element is calculated by 6.1-6.5 wt%;

step (2), pressing an electrode: equally dividing the titanium sponge in the raw material in the step (1) into N parts, dividing the raw materials except the titanium sponge into N-1 parts of alloy bags, then placing one part of alloy bag between every two parts of titanium sponge from top to bottom in a mould for paving, and then pressing to form an electrode block;

step (3), welding a primary electrode: drying the pressed electrode block in the step (2), and then welding the electrode block after drying; when the electrode blocks are welded, 6-7 electrode blocks are welded into a long electrode in an external plasma argon arc welding mode to serve as a primary consumable electrode;

step (4), furnace charging and vacuumizing for one time: putting the primary consumable electrode obtained in the step (3) into a vacuum consumable furnace, wherein the clearance between the primary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing granular titanium sponge as an arc starting material on the top end plane of the primary consumable electrode, sealing the furnace after the electrode is installed, and respectively starting vacuumizing until the vacuum degree in the furnace is lower than 6.7Pa after the furnace is sealed;

step (5), welding and vacuumizing in a furnace for one time: welding the primary consumable electrode and the auxiliary electrode at the connecting part of the electrode rod firmly; welding technological parameters are as follows: the arc voltage is 25-35V, the arc current is 3.0-5.0 kA, and the welding time is 30-50 s; cooling after welding, and then carrying out furnace internal gas release; adjusting the lifting of the electrode rod to enable the bottom surface of the primary consumable electrode to be 200mm above the plane of the flange; placing titanium sponge on the bottom plane of the crucible as an arc striking material, then sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (6), primary arc striking smelting and cooling: after arcing, controlling the titanium liquid to occupy the whole molten pool within 5-8 min, wherein the arc current in the arc striking period is only 25-60% of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 30-33V, and the smelting arc current is 7.0-8.0 KA; after the normal smelting period is finished, filling argon for cooling, discharging to obtain a primary VAR ingot;

step (7), cleaning flat heads: cleaning dirt and impurities on the surface of the primary VAR cast ingot, then performing flat head treatment on the cleaned primary VAR cast ingot, and turning two ends of the primary VAR cast ingot flat;

step (8), welding a secondary electrode: welding 3 primary VAR cast ingots together by adopting a welding mode of plasma argon arc welding outside the furnace to form a long electrode serving as a secondary consumable electrode;

step (9), secondary furnace charging and vacuumizing: putting the secondary consumable electrode obtained in the step (8) into a vacuum consumable furnace, wherein the clearance between the secondary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing titanium sponge as an arc striking material in the center of the upper plane, sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (10), welding and vacuumizing in a secondary furnace: welding the secondary consumable electrode with an auxiliary electrode connected with the electrode rod firmly; welding technological parameters are as follows: the welding voltage is 20-30V, the welding current is 2.0-5.0 kA, and the welding time is 60-90 s; after welding, argon is filled for cooling, and then furnace internal gas release is carried out; adjusting the lifting of the electrode rod to enable the bottom surface of the secondary consumable electrode to be 200mm above the plane of the flange; placing titanium sponge as an arc striking material on the bottom plane of the crucible, then sealing the furnace, and evacuating until the vacuum degree in the furnace is lower than 3 Pa;

step (11), secondary arc striking smelting and cooling: after arcing, controlling the titanium liquid to occupy the whole molten pool within 3-6 min, wherein the arc current in the arc striking period is 25-60% of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 32-34V, and the smelting arc current is 9.0-10.0 KA; feeding after the normal smelting period is finished until the tail of the cast ingot is flat and smooth; 3-5 min after the completion of the feeding, filling argon, cooling, and discharging to obtain a secondary VAR ingot;

step (12), peeling: naturally cooling the secondary VAR cast ingot to room temperature, and then removing oxide skin and defects on the surface layer of the cast ingot to obtain a TC4 titanium alloy round light ingot;

step (13), heating: firstly, placing a TC4 titanium alloy round polished ingot in a heating furnace for heating, gradually heating from room temperature to 1000-1200 ℃ at the heating rate of 6.4 ℃/min during heating, enabling the maximum allowable heat preservation time at the heating temperature to be less than 4h, and lifting and forging the hot polished ingot blank after the required heat preservation time is reached to obtain a square blank for rolling a large-disc-weight Ti-6Al-4V alloy wire rod at a high speed.

2. The method for preparing the square billet for rolling the large-disc-weight Ti-6Al-4V alloy wire rod at the high speed according to the claim 1, wherein in the step (1), the raw materials comprise an aluminum-vanadium intermediate alloy, titanium sponge, aluminum beans and aluminum foil.

3. The method for preparing a square billet for rolling a large-coil-weight Ti-6Al-4V alloy wire rod at a high speed according to claim 1, wherein in the step (2), the titanium sponge in the raw material in the step (1) is divided into 3 parts, the raw materials except the titanium sponge are divided into 2 parts of alloy bags, and then the titanium sponge, the alloy bags, the titanium sponge, the alloy bags and the titanium sponge are paved in a die from bottom to top in the order of titanium sponge, alloy bags, titanium sponge and then pressed to form the electrode block; and in the pressing process, the unit pressure is increased from 0 to 18MPa, and the pressure is maintained for 15-20 s under the unit pressure of 18MPa and then is released.

4. The production method of a billet for high-speed rolling of a large coil weight Ti-6Al-4V alloy wire rod according to claim 1, wherein in the step (5), the post-welding cooling time is 10 min; in the step (6), the cooling time is 3 h; in the step (10), the cooling time after welding is 10 min; in the step (11), the cooling time is 4 h.

5. The method for preparing a square billet for rolling a large-coil-weight Ti-6Al-4V alloy wire rod at a high speed according to claim 1, wherein in the step (5) and the step (10), the welding area is more than 75%; in the step (4) and the step (9), the using amount of the arcing material is 20 g; in the step (5) and the step (10), the amount of the arcing material is 2000 g.

6. The method for preparing the square billet for rolling the Ti-6Al-4V alloy wire rod with the large disk weight at the high speed according to the claim 1, wherein in the step (12), the peeling treatment is turning for 1-3 mm, and the surface roughness after turning is less than 12.5 μm.

7. The preparation method of the square billet for rolling the Ti-6Al-4V alloy wire rod with the large coil weight at the high speed according to the claim 1, wherein in the step (13), when the TC4 titanium alloy round light ingot is heated, the placing position of the TC4 titanium alloy round light ingot is 50-70 mm away from the resistance wire and more than 200mm away from the thermocouple; forging by using a 3t air hammer; and coating an anti-oxidation coating on the surface of the square billet after forging.

8. The method for preparing the square billet for rolling the Ti-6Al-4V alloy wire rod with the large disc weight at the high speed according to the claim 1, wherein in the step (11), the current is reduced by 0.5KA every 5min during feeding until the current is reduced to be lower than 4KA, and the feeding is stopped, wherein the whole feeding process needs 30-50 min.

9. The method for preparing a square billet for rolling a Ti-6Al-4V alloy wire rod with a large disc weight at a high speed according to claim 1, wherein in the step (13), after the deformation exceeds 20 percent in the forging process, the square billet is subjected to heavy hammer forging according to the normal deformation, the deformation in the blank cogging forging stage is controlled to be 50-75 percent, when the deformation is difficult or the temperature is low at the finish forging temperature of not less than 850 ℃, the blank after cogging forging is required to be hung back into a furnace to be heated for 150-200 min to carry out secondary forging until 150 square billets are forged, and the forging finish temperature in the stage is higher than 750 ℃.

10. The Ti-6Al-4V alloy wire rod billet produced by the method for producing a large coil weight Ti-6Al-4V alloy wire rod billet for high-speed rolling according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to a square billet for rolling a large-coil-weight Ti-6Al-4V alloy wire rod at a high speed and a preparation method thereof.

Background

The Ti-6Al-4V alloy (hereinafter referred to as TC4 alloy) has a series of excellent characteristics of good high temperature resistance and corrosion resistance, good biocompatibility, high specific strength, self-non-magnetism and the like, and is widely applied to the industries of aerospace, ship manufacturing, petrochemical industry, weapons, metallurgy, electric power and the like. The TC4 alloy wire rod is used as an intermediate product, the production process is continuously optimized and improved, and the product performance and the quality are greatly improved. The TC4 alloy square billet is used for rolling the titanium alloy wire rod, the TC4 titanium alloy has higher strength, and the processing equipment capability is limited, so the original method for producing the TC4 square billet is to prepare 150 square billets in an as-cast state by machining (using a lathe or a sawing machine) a TC4 alloy round cast ingot, and the specification of the 150 square billets is 150 multiplied by L (W multiplied by H multiplied by L) mm. The method for producing the square billet needs to use a special YG8 hard alloy cutter and an alloy saw blade, so that the cost is higher, the yield is less than 80 percent, the production efficiency is low, the produced square billet is in an as-cast state, the difference of the internal microstructure is large, the surface quality defects of the rolled product are more, and the product performance is obviously influenced by the defects. Therefore, how to overcome the defects of the prior art is a problem which needs to be solved urgently in the technical field of metallurgy at present.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a square billet for rolling a Ti-6Al-4V alloy wire rod with large coil weight at a high speed and a preparation method thereof. According to the method, a TC4 round cast ingot is heated and then forged twice by a 3t air hammer to prepare a 150 square billet with the specification of 150 multiplied by L (W multiplied by H multiplied by L). The TC4 alloy square billet produced by the method is in a forging state, internal crystal grains are refined to a certain degree after forging, the structure performance is optimized, the yield is as high as 95%, the production efficiency is improved, the surface defects of the rolled titanium alloy wire rod are fewer, and the overall performance is superior to that of the wire rod produced by the original machining method.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method of a square billet for rolling a large-coil-weight Ti-6Al-4V alloy wire rod at a high speed comprises the following steps:

step (1), alloy coating: nominal chemical composition of TC4 alloy preparation raw materials; wherein, the mass percent of Al element is calculated by 6.1-6.5 wt%;

step (2), pressing an electrode: equally dividing the titanium sponge in the raw material in the step (1) into N parts, dividing the raw materials except the titanium sponge into N-1 parts of alloy bags, then placing one part of alloy bag between every two parts of titanium sponge from top to bottom in a mould for paving, and then pressing to form an electrode block;

step (3), welding a primary electrode: drying the pressed electrode block in the step (2), and then welding the electrode block after drying; when the electrode blocks are welded, 6-7 electrode blocks are welded into a long electrode in an external plasma argon arc welding mode to serve as a primary consumable electrode;

step (4), furnace charging and vacuumizing for one time: putting the primary consumable electrode obtained in the step (3) into a vacuum consumable furnace, wherein the clearance between the primary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing granular titanium sponge as an arc starting material on the top end plane of the primary consumable electrode, sealing the furnace after the electrode is installed, and respectively starting vacuumizing until the vacuum degree in the furnace is lower than 6.7Pa after the furnace is sealed;

step (5), welding and vacuumizing in a furnace for one time: welding the primary consumable electrode and the auxiliary electrode at the connecting part of the electrode rod firmly; welding technological parameters are as follows: the arc voltage is 25-35V, the arc current is 3.0-5.0 kA, and the welding time is 30-50 s; cooling after welding, then performing furnace internal gas release and disassembling the furnace to check the welding quality condition; adjusting the lifting of the electrode rod to enable the bottom surface of the primary consumable electrode to be 200mm above the plane of the flange, and taking the distance from the plane of the flange to the bottom surface of the primary consumable electrode as an arcing gap; placing titanium sponge on the bottom plane of the crucible as an arc striking material, then sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (6), primary arc striking smelting and cooling: after arcing, controlling the titanium liquid to occupy the whole molten pool within 5-8 min, wherein the arc current in the arc striking period is only 25-60% of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 30-33V, and the smelting arc current is 7.0-8.0 KA; after the normal smelting period is finished, filling argon for cooling, discharging to obtain a primary VAR ingot;

step (7), cleaning flat heads: cleaning dirt and impurities on the surface of the primary VAR cast ingot, then performing flat head treatment on the cleaned primary VAR cast ingot, and turning two ends of the primary VAR cast ingot flat;

step (8), welding a secondary electrode: welding 3 primary VAR cast ingots together by adopting a welding mode of plasma argon arc welding outside the furnace to form a long electrode serving as a secondary consumable electrode;

step (9), secondary furnace charging and vacuumizing: putting the secondary consumable electrode obtained in the step (8) into a vacuum consumable furnace, wherein the clearance between the secondary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing titanium sponge as an arc striking material in the center of the upper plane, sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (10), welding and vacuumizing in a secondary furnace: welding the secondary consumable electrode with an auxiliary electrode connected with the electrode rod firmly; welding technological parameters are as follows: the welding voltage is 20-30V, the welding current is 2.0-5.0 kA, and the welding time is 60-90 s; after welding, argon is injected for cooling, then furnace internal gas release is carried out, and the furnace is opened to check the welding quality condition; adjusting the lifting of the electrode rod to enable the bottom surface of the secondary consumable electrode to be 200mm above the plane of the flange, and taking the distance from the plane of the flange to the bottom surface of the secondary consumable electrode as an arcing gap; placing titanium sponge as an arc striking material on the bottom plane of the crucible, then sealing the furnace, and evacuating until the vacuum degree in the furnace is lower than 3 Pa;

step (11), secondary arc striking smelting and cooling: after arcing, controlling the titanium liquid to occupy the whole molten pool within 3-6 min, wherein the arc current in the arc striking period is 25-60% of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 32-34V, and the smelting arc current is 9.0-10.0 KA; feeding after the normal smelting period is finished until the tail of the cast ingot is flat and smooth; 3-5 min after the completion of the feeding, filling argon, cooling, and discharging to obtain a secondary VAR ingot;

step (12), peeling: naturally cooling the secondary VAR cast ingot to room temperature, and then removing oxide skin and defects on the surface layer of the cast ingot to obtain a TC4 titanium alloy round light ingot;

step (13), heating: firstly, placing a TC4 titanium alloy round polished ingot in a heating furnace for heating, gradually heating from room temperature to 1000-1200 ℃ at the heating rate of 6.4 ℃/min during heating, enabling the maximum allowable heat preservation time at the heating temperature to be less than 4h, and lifting and forging the hot polished ingot blank after the required heat preservation time is reached to obtain a square blank for rolling a large-disc-weight Ti-6Al-4V alloy wire rod at a high speed.

Further, in the step (1), the raw materials preferably include an aluminum vanadium master alloy, titanium sponge, aluminum beans and aluminum foil.

Further, preferably, in the step (2), the titanium sponge in the raw material in the step (1) is equally divided into 3 parts, the other raw materials except the titanium sponge are divided into 2 parts of alloy bags, then the titanium sponge, the alloy bags, the titanium sponge, the alloy bags and the titanium sponge are paved in a die from bottom to top in sequence, and then the electrode block is formed by pressing; and in the pressing process, the unit pressure is increased from 0 to 18MPa, and the pressure is maintained for 15-20 s under the unit pressure of 18MPa and then is released.

Further, it is preferable that, in the step (5), the cooling time after welding is 10 min; in the step (6), the cooling time is 3 h; in the step (10), the cooling time after welding is 10 min; in the step (11), the cooling time is 4 h.

Further, it is preferable that in the step (5) and the step (10), the welding area should be 75% or more; in the step (4) and the step (9), the using amount of the arcing material is 20 g; in the step (5) and the step (10), the amount of the arcing material is 2000 g.

Further, in the step (12), preferably, the peeling treatment is turning for 1-3 mm, and the surface roughness after turning should be less than 12.5 μm.

Further, preferably, in the step (13), when the TC4 titanium alloy round light ingot is heated, the placing position of the TC4 titanium alloy round light ingot should be 50-70 mm away from the resistance wire and more than 200mm away from the thermocouple; forging by using a 3t air hammer; and coating an anti-oxidation coating on the surface of the square billet after forging.

Further, in the step (11), the current is preferably reduced by 0.5KA every 5min during feeding until the current is reduced to less than 4KA, and feeding is stopped, wherein the whole feeding process needs 30-50 min.

Further, it is preferable that, in the step (13), the ingot is cogging forged: the heated smooth ingot blank was lifted out on a 3t air hammer for free cogging forging. The principle of small deformation, light weight, quick beating and frequent overturning is followed in the initial cogging stage, when the deformation exceeds 20 percent in the forging process, heavy weight forging is carried out according to the normal deformation, the deformation in the blank cogging forging stage is controlled to be 50-75 percent, and the final forging temperature is not lower than 850 ℃. When the deformation is substantially complete or the temperature is low, the amount of deformation should be gradually reduced to avoid cracking. When the deformation is difficult or the temperature is low, the blank after cogging forging needs to be lifted back into the furnace to be heated for 150-200 min for secondary forging until 150 square blanks are forged, and the finish forging temperature at the stage is higher than 750 ℃.

The invention also provides a square billet of the Ti-6Al-4V alloy wire rod prepared by the preparation method for rolling the square billet of the Ti-6Al-4V alloy wire rod with large coil weight at high speed.

Compared with the prior art, the invention has the beneficial effects that:

the TC4 alloy square billet produced by the method is in a forged state, internal crystal grains are refined to a certain degree after forging, the structure performance is optimized, the yield is as high as 95%, the production efficiency is improved, the surface defects of the rolled titanium alloy wire rod are fewer, and the overall performance is superior to that of the wire rod produced by the original machining method. For the expensive titanium alloy material, the forging forming method is selected, so that the internal quality of the material can be improved, and the material can be saved. The invention adopts a free forging method to produce the Ti-6Al-4V titanium alloy square billet, and the method has the advantages of short production preparation period, low requirement on equipment capacity, wide applicability, no need of a special die and low production cost.

Detailed Description

The present invention will be described in further detail with reference to examples.

It will be appreciated by those skilled in the art that the following examples are illustrative of the invention only and should not be taken as limiting the scope of the invention. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The materials or equipment used are not indicated by manufacturers, and all are conventional products available by purchase.

The process route of the invention is as follows: alloy-coated bag → electrode pressing → welding primary electrode → furnace charging and evacuation → furnace welding → vacuum pumping → arc ignition → smelting → cooling and discharging → primary ingot cleaning and flat head → welding secondary electrode → furnace charging and evacuation → furnace welding → smelting → feeding → cooling and discharging → peeling → inspection → heating → forging to obtain 150 square billet finished product.

Alloy coating: the nominal chemical composition of the TC4 alloy is Ti-6Al-4V, and in the actual production process, the mass percent of Al element is calculated by 6.1-6.5 wt% considering the burning loss of the Al element during smelting, and the mass percent of other elements is calculated according to the nominal chemical composition. The proportioning condition of the required raw materials is calculated according to the method, the required amount of intermediate aluminum-vanadium alloy and aluminum beans (aluminum foils) are weighed according to the proportioning of the raw materials, and the intermediate aluminum-vanadium alloy and the aluminum beans (aluminum foils) are uniformly mixed and packaged into an alloy bag.

And (3) electrode pressing: the residual titanium sponge on the hydraulic briquetting machine is cleaned, and the cleaning of a briquetting station is ensured. And (3) lowering the pressing die to a working position, placing the pressing head right above the pressing die and keeping the pressing head stationary, dividing the pressing head into three equal parts according to the amount of the sponge titanium required in the raw material proportion, then respectively weighing each equal part of the sponge titanium, and marking the equal parts as a first equal part, a second equal part and a third equal part, and reserving the equal parts as pressing electrode blocks after weighing. When the titanium sponge and the alloy package are pressed together to form the electrode block, the weighed materials are dried, the accurate weight of each raw material is ensured during weighing, otherwise, the problem of uneven components can occur, and the performance requirement of the final product is difficult to ensure. Pouring the weighed first-part titanium sponge into a mold, flatly paving the mold, flatly placing an alloy bag in the center of the mold, pouring the second-part titanium sponge, flatly paving the poured second-part titanium sponge, putting the second-part alloy bag in the center of the mold, finally pouring the third-part titanium sponge and flatly paving the third-part titanium sponge, and finishing material distribution; then slowly descending a pressure head of the hydraulic press to start pressing an electrode block, buckling the end heads of the two steel ropes on a pressing die while the pressure head descends slowly, gradually increasing the unit pressure from 0 to 18MPa when the pressure head begins to contact the titanium sponge, maintaining the pressure for 15-20 s under the unit pressure of 18MPa, releasing the pressure after the required pressure maintaining time is reached, slowly lifting the pressing die and the pressure head together under the action of the steel wire rope after a pointer on a pressure gauge returns to zero, pushing a cushion block to the position right below the pressing die after the pressing die and the pressure head are lifted to a certain height, and descending the pressing die to enable the pressing die to just fall on the cushion block; then manually pushing the cart to a position right below the pressure head, lowering the pressure head to press the pressed electrode block out of the pressing die and drop the electrode block into the cart, then withdrawing the cart, taking out the electrode block, weighing and recording; and then appropriately lifting the pressing die to conveniently and smoothly withdraw the cushion block, lowering the pressing die to a station after withdrawing the cushion block, taking the two ends of the steel rope from the pressing die, and continuing the operation to press a next electrode block, wherein the specification of the pressed single electrode block is phi 150 multiplied by 350mm, and the weight of the pressed single electrode block is 25 kg.

Welding a primary electrode: and drying the pressed electrode block, and then welding. When welding the electrode blocks, 6-7 electrode blocks are welded into a long electrode (primary electrode) by adopting a welding mode of plasma argon arc welding outside the furnace. During welding, the strength of the consumable electrode (namely the primary consumable electrode) is ensured to be high enough, the consumable electrode cannot break and fall off in the lifting process under the self weight condition of the primary consumable electrode, and the primary consumable electrode can not be overheated under the condition of passing large current, so that the fusible component is prevented from being melted early to damage alloy components. Inspecting the appearance size and shape, the quality of a welding seam, whether the surface is oxidized and the like of the prepared consumable electrode; before charging, preparing a titanium sponge material for arc striking, an auxiliary electrode connector and a crystallizer with the same model as the technological requirement. After the inspection is correct, the consumable electrode and the auxiliary electrode are determined to have the same mark, and the electrodes which are qualified and meet the requirements can be charged.

Charging and evacuating: clamping the consumable electrode at the center of a crucible base by using an ingot supporting trolley, starting the lifting trolley to support the electrode to ascend into a crucible, loosening a clamp of the ingot supporting trolley, ensuring that the electrode does not incline when the clamp is loosened, avoiding scratching the crucible, aligning the center position of the electrode after the lifting trolley is in place, ensuring that the gap between the electrode and the crucible is not less than 30mm, and fixing the electrode by using a wood wedge after alignment; then putting arc starting materials, chip materials or small sponge titanium particles with the same mark on the top plane of the consumable electrode; after the electrode is determined to be installed and checked to be correct, the furnace can be sealed. After the furnace is sealed, vacuumizing operation is started, and before vacuumizing, whether water, electricity, instruments and meters, high-pressure air and compressed air are normal or not is checked. The vacuum pump body can be started up through checking, when the vacuum degree reaches 1000Pa, the small Roots pump is started up, when the furnace body is pumped to 400Pa, the large Roots pump is started up, when the vacuum degree of the furnace body reaches 133Pa, the oil booster pump can be preheated, the oil temperature can reach 240-250 ℃, and the oil booster pump can enter a working state.

Welding in a furnace: when the vacuum degree in the furnace is lower than 6.7Pa and the air leakage rate is less than 2Pa/min, the welding in the furnace can be carried out. Furnace welding technological parameters: the arc voltage is 25-35V, the arc current is 3.0-5.0 kA, the welding time is 30-50 s, and the cooling time is 15 min. And (3) after welding, deflating the furnace, taking out the wooden wedge for fixing the consumable electrode, disassembling the furnace to check the welding quality, wherein the welding area is more than 75%, otherwise, repairing welding, removing the welding beading and cleaning.

Vacuumizing: after the furnace is sealed, a mechanical pump is started to vacuumize the furnace body, when the vacuum degree reaches 1000Pa, a small roots pump is started, when the vacuum degree reaches 400Pa, a large roots pump is started, when the vacuum degree of the furnace body reaches 133Pa, an oil booster pump can be preheated, the pump is kept started for 60-90 min, the oil temperature can reach 240-250 ℃, the oil booster pump can enter a working state, and at the moment, the vacuum degree in the furnace is lower than 3 Pa. And (5) detecting the leakage of the furnace body, wherein the leakage rate is less than 0.6 Pa/min.

Arc striking: after the arc is started, the whole molten pool is occupied by the transition time of 5-8 min, the arc starting period is as short as possible, the molten pool is quickly formed, and the impact of the arc on the crucible bottom is reduced; the power supply system in the arc striking period is much smaller than the power of normal smelting, and the arc current in the arc striking period is only 25-60% of that in the normal smelting.

Smelting: and entering a normal smelting period required by the process after arc striking is finished, wherein the smelting voltage in the smelting period is 31-33V, and the smelting current is 7.0-8.0 KA. The smelting period can remove gas, metallic inclusions and various harmful impurities, homogenize alloy components, improve the crystal structure and eliminate various defects.

Cooling and discharging: and after the normal smelting period is finished, the ingot is required to be filled with argon for cooling for 3 hours. When argon is filled, the valve is closed, the oil booster pump and the roots pump stop running, and the mechanical pump is in a normal running state. In order to prevent the oil of the booster pump from being oxidized, the mechanical pump can be stopped after the oil booster pump is cooled for 90 minutes; and after the specified cooling time is reached, deflating, disassembling the furnace, lowering the crucible base, lifting out the ingot, and marking information such as the brand, the ingot number, the weight, the specification and the like of the ingot on the feeding end face of the VAR ingot.

Cleaning flat heads of primary ingots: cleaning dirt and impurities on the surface of the VAR ingot by using an ingot cleaning machine, and brushing the oxide on the surface of the ingot by using a steel wire wheel for surface oxides which cannot be cleaned by the ingot cleaning machine; in order to weld the secondary electrode conveniently, the flat head treatment needs to be carried out on the smelted primary VAR ingot, the two ends of the ingot are turned to be flat, the burrs are cut off by a sawing machine or a lathe, and the end face of the head of the primary VAR ingot after the flat head treatment is 4-6 mm higher than the feeding end face. When in sawing, the inclination of the saw cut is less than 2 mm.

Welding a secondary electrode: after cleaning and flatting the smelted primary VAR ingots, 3 primary VAR ingots are welded together by adopting a welding mode of plasma argon arc welding outside the furnace to form a long electrode (secondary electrode) which is used as a consumable electrode for smelting secondary VAR ingots. Welding by adopting plasma argon arc welding outside the furnace, wherein the welding seam position is required not to be oxidized, and the oxidized part is required to be polished and removed; the bending degree of the electrode is controlled within 3 mm/m; the smaller the gap, the better when two VAR ingots are butt welded once.

Charging: selecting a crucible specification meeting the process requirement, and cleaning; after the crucible is prepared, clamping the secondary electrode by an ingot supporting trolley, vertically placing the secondary electrode at the central position of the crucible base, adjusting the center, lifting the trolley, finding the central position of the electrode in the crucible, ensuring that the gap between the electrode and the crucible is more than 30mm, and fixing the electrode by a wood wedge; 20g of sponge titanium is placed in the center of the upper plane of the consumable electrode to be used as an arc striking material, and the consumable electrode can be sealed and vacuumized after being installed.

Vacuumizing: checking water, electricity, instruments, compressed air and the like, sending electricity of a control system after checking the water, electricity, instruments, compressed air and the like to be normal, starting pumps and valves of a vacuum system to begin evacuation, starting a pumping body of a mechanical pump, starting a small roots pump when the vacuum degree of the furnace body reaches 1000Pa, starting a large roots pump when the furnace body is pumped to 400Pa, preheating an oil booster pump when the vacuum degree of the furnace body reaches 133Pa, maintaining the pump to be started for 60-90 min, enabling the oil temperature to reach 240-250 ℃, enabling the oil booster pump to enter a working state, enabling the vacuum degree in the furnace to be lower than 3Pa at the moment, testing the gas leakage rate to be not more than 0.6Pa/min, and carrying out furnace welding: the welding voltage is 20-30V, the welding current is 2.0-5.0 kA, the welding time is 60-90 s, and the cooling time is 20 min. After cooling, deflating the furnace, and preparing for opening the furnace; checking the welding condition, wherein the welding area is more than 75%, otherwise, the welding can be started due to the overheating of large current, plasma argon arc welding repair welding is adopted, the oxide generated needs to be cleaned, the nubs welded in the furnace are cleaned, otherwise, the side arc is easy to generate, and the crucible is punctured. Cleaning titanium particles, splashed objects and dust on a crucible flange and a sealing ring; lifting the electrode rod to a certain height, putting a proper amount of sponge titanium on the bottom of the crucible as an arc striking material, and measuring the distance between the bottom surface of the consumable electrode (secondary electrode) and the bottom plane of the crucible to be more than 100mm to be used as an arc striking gap; then sealing the furnace and evacuating. After the furnace is sealed, a mechanical pump is started to vacuumize the furnace body, when the vacuum degree reaches 1000Pa, a small roots pump is started, when the vacuum degree reaches 400Pa, a large roots pump is started, when the vacuum degree of the furnace body reaches 133Pa, an oil booster pump can be preheated, the pump is kept started for 60-90 min, the oil temperature can reach 240-250 ℃, the oil booster pump can enter a working state, and at the moment, the vacuum degree in the furnace is lower than 3 Pa. And (4) detecting the leakage of the furnace body, wherein the leakage rate is not more than 0.6Pa/min, and the high pressure can be distributed.

Smelting: slowly lowering the electrode rod to short circuit arc starting, slightly lifting the electrode rod, controlling the arc pressure, keeping the arc length, filling the whole molten pool with the transition time of 3-6 min, quickly forming the molten pool and reducing the impact of the electric arc on the crucible bottom; the power supply system in the arc striking period is much smaller than the power of normal smelting, and the arc current in the arc striking period is only 25-60% of that in the normal smelting. And entering a normal smelting period required by the process after arc striking is finished, wherein the smelting voltage in the smelting period is 32-34V, and the smelting current is 9.0-10.0 KA.

Feeding: after the normal smelting period is finished, feeding is carried out, and the tail of the cast ingot is leveled.

Cooling and discharging: and 3-5 min after the completion of the feeding, closing the valve, and filling argon into the cast ingot for cooling for 4 h. When argon is filled, the valve is closed, the oil booster pump and the roots pump stop running, and the mechanical pump is in a normal running state. In order to prevent the oil of the booster pump from being oxidized, the mechanical pump can be stopped after the oil booster pump is cooled for 90 min; and after the specified cooling time is reached, deflating, disassembling the furnace, lowering the crucible base, lifting out the ingot, and marking information such as the brand, the ingot number, the weight, the specification and the like of the ingot on the feeding end face of the secondary VAR ingot.

Peeling: after the secondary VAR cast ingot is lifted out of the vacuum consumable furnace, residual temperature still remains, the secondary VAR cast ingot needs to be slowly cooled to room temperature in an air cooling mode, the cooled secondary VAR rough ingot needs to be turned and scalped, generally 1-3 mm turning can be carried out to remove oxide skin and defects on the surface layer of the cast ingot, a round polished ingot of TC4 titanium alloy is obtained after scalping, and the specification of the round polished ingot after scalping is phi 380 multiplied by 2000 mm.

And (4) checking: the surface processing quality of the TC4 titanium alloy round polished ingot after peeling needs to be checked, and the surface roughness of the round ingot after turning is less than 12.5 mu m.

Heating: the peeled round light ingot needs to be heated in a heating furnace, the heating furnace used in the invention is a box type heating furnace, and the technical parameter range is as follows: rated power 180KW, maximum working temperature 1250 deg.C, common working temperature 1200 deg.C, furnace temperature uniformity 1200 deg.C (+ -7 deg.C), room temperature raising to 1200 deg.C for 180min, 2 temperature control regions, hearth size 2000 x 1000 x 600mm (L x W x H), temperature control accuracy + -1 deg.C, and maximum charging amount 3000 kg.

Before the heating furnace is used, whether the heating belt or the resistance wire is abnormal or not is firstly confirmed, the oxide skin falling off during the last heating in the hearth is removed, and then a power main switch is switched on. The TC4 alloy light ingot is placed in an RX-180-12 box type heating furnace by using a special fixture matched with a travelling crane for heating, materials are placed at the correct position during charging, the total weight of the charging cannot exceed 3000kg, the placing position of the materials is 50-70 mm away from a resistance wire and is more than 200mm away from a thermocouple. After the materials are placed, starting the electric furnace, adjusting the temperature of the temperature control instrument to 1150 ℃, switching on a heating switch, gradually heating the electric furnace from room temperature to 1150 ℃ at the speed of 6.4 ℃/min, wherein the maximum allowable heat preservation time at the heating temperature is less than 4h, and lifting the hot ingot blank out for forging after the required heat preservation time is reached; when discharging, the heating power supply is cut off first and then discharging operation is carried out. When the materials are lifted out, the labor protection article needs to be worn to prevent the materials from being scalded. When the furnace temperature is higher than 400 ℃, the furnace door is not allowed to be opened for cooling, the highest service temperature is not higher than the rated temperature, the electric elements are prevented from being collided and the bottom plate of the furnace is prevented from being smashed by throwing forcibly during charging, when the circuit is heated, an operator does not need to be far away from the electric furnace, the operator constantly pays attention to whether the temperature displayed by the instrument is normal or not, whether the electric furnace works normally or not, if the abnormality is found, the heating is immediately stopped, and the fault is eliminated. When the abnormal phenomenon of the equipment is found in the working process, the equipment must be stopped immediately and the maintenance personnel can be informed to repair the equipment in time.

The forging equipment mainly comprises an air compressor, a 3t air hammer (forging machine) and an operating machine (turnover machine). The method uses a 3L-10/8 type air compressor, the rotating speed is 480r/min, the volume flow is 20 m/min, the shaft power is 118KW, and the exhaust pressure is 0.8 Pa. Before the air compressor is used, checking and confirming that lubricating oil in an oil pool is kept in a scale range, wherein the mark number of the lubricating oil meets the requirement, and the oil amount in the oil ejector is not lower than a scale mark; before starting up, the manual wheel is rotated to inject oil into the cylinder, and uniform and sufficient oil drops can be seen from the oil viewer; checking whether the exhaust pipeline is unblocked and whether the air release valve is opened, and closing the load reduction valve or opening the oil-water blow-off valve to ensure that the exhaust pipeline is in a non-pressure state in order to reduce the load during starting; and when each cooling water valve is opened, water flow is smooth and no air bubbles exist. Then, switching on current to enable the air compressor to run in an idle state; after the no-load operation is normal, the load reducing valve is gradually opened, the oil-water blow-off valve of each stage of cooler is closed, and the air compressor is enabled to operate under the load state. When in operation, cooling water is smooth, uniform, non-intermittent and bubble-free, and the water temperature is not more than 40 ℃; the exhaust temperature is not more than 160 ℃, the temperature after water cooling is not more than 40 ℃, the current, the voltage and the temperature of the motor are normal, the air suction valve cover does not heat, and the sound of the valve is normal. And (3) opening each stage of oil-water blow-off valve to blow off every 2 hours of operation, and discharging the oil-water in the gas storage tank 3-5 times every day. After the forging is finished, closing the load reducing valve, and opening the coolers and the oil-water blow-off valve at each stage; turning off the power supply to stop the machine; closing a cooling water inlet valve, and discharging residual water in the cylinder sleeve, the oil-water separator of each stage of cooler and the gas storage tank; discharging compressed air at each stage of exhaust pipe; the power supply should be restored to the pre-fluctuation state after being turned off. The nominal weight of a falling part of a 3t air hammer (forging machine) used in the invention is 3000kg, the actual weight of the falling part is 3695kg, the striking energy is not less than 124KJ, the maximum stroke is 1450mm, the diameter of an air cylinder is 550mm, the diameter of a hammer rod is 180mm, the air inlet pressure is 0.6-0.8 MPa, and the total height of the forging hammer is 8687 mm. The maximum clamping nominal weight of the manipulator (the tilter) used by the invention is 1500kg, the common clamping weight is 1000kg, the maximum walking stroke is 8000mm, the diameter of the cylinder is phi 400mm, and the air inlet pressure is 0.6-0.8 MPa. Before the operation machine is used, a power supply main switch is turned on, and an air compressor is started to keep the air inlet pressure at 0.6-0.8 Mpa. A left handle on the front platform of the cab is controlled to reciprocate in the front half stroke, and the control vehicle moves forwards; the left handle is controlled to do reciprocating motion in the second half stroke, the control vehicle moves backwards, the operation of the control vehicle stops once in each stroke, and the operation stopping action must be matched with the hammering frequency of the forging hammer. The left handle on the front stage of the cab is controlled to reciprocate in the front half stroke, the clamp position of the operating vehicle is increased, the right handle is controlled to reciprocate in the rear half stroke, the clamp height of the operating vehicle is reduced, and each stroke of the clamp is lifted or lowered once. When forging, the clamp head material must be kept horizontal and kept parallel between the anvils of the forging hammer to ensure the forging quality. In the forging process, if the clamp needs to be rotated, a pedal plate below a cab is treaded, the left pedal controls the clamp to rotate leftwards, the right pedal controls the clamp to rotate rightwards, and the pedal returns to the position, so that the rotation is stopped. The rotation and stop of the clamp can be controlled by coordinating the forging hammer according to the requirement of the forging process. After the clamping operation is finished, the control vehicle is driven to a parking space, and the electric door is closed after the control handles and the pedal plates return to the zero position. In the forging process, the square billet size measurement is carried out while forging, and the size of the forged square billet is ensured to meet the process requirement. When the temperature of a workshop is lower, the forging hammer, the anvil, the die and the tool clamp are preheated to about 100 ℃ before forging. Before the air hammer works, condensed water in the cylinder must be drained, whether the air pipe and the valve leak air or not is checked, the machine base, the anvil block, the anvil, the hammer head, the guide rail plate, the hammer rod and the like are checked to be intact without cracks, the wedge iron is firmly fastened, and bolts at all parts do not loosen. No large dislocation is generated when the hammer head and the anvil are aligned, and the gap between the upright post guide rail plate and the hammer head is in accordance with the specification.

The hammer is tested before forging, and the blank hammer is not required to be hammered during test hammering, so that a wood board or a heated forging piece must be placed to prevent the hammer anvil from breaking. The hammer must be controlled by the palm pliers, and the operator is not allowed to hammer during the operation and displacement process. In the forging process, the pad iron is strictly prevented from being plugged on the anvil surface or the measurement operation is carried out, and the operation can be carried out after the hammer head is stably lifted. When the workpiece is loaded and unloaded, the hammer is fixed well, and the drop distance is small when the hammering starts. The forging machine must be placed in the center of the anvil to forge the workpiece without being misaligned. The quick, slow, light, heavy, start and stop of the forging hammer operation must be accurately carried out according to the indication signal of a commander. During the re-striking, special attention is paid to control the stroke length of the operating rod. The clamp is required to be matched with the size and shape of a workpiece, the workpiece is required to be clamped, fingers of a user holding the clamp cannot be placed between the clamp handles, and the clamp handles are placed on the side face of the body and are not aligned to the abdomen and the chest. And oxide skin attached to the surface of the forging piece is removed in time in the forging process. When the forged workpiece is thrown, attention must be paid to the presence of a person or an obstacle around the workpiece. When the material is cut off, the mincing knife should be laid flat and aligned, and people are not aligned on the front side of the incision. In operation, if cracks are found in the machine base, the anvil block, the anvil, the hammer head, the guide rail and the hammer rod, the operation should be stopped immediately. During operation, if the down time is long, the hammer head should be tied on the anvil to close the air inlet valve and the air throttle valve.

(1) After cooling the forged square billet, sawing off the head and tail cracking parts, chamfering the edges by 20mm multiplied by 45 degrees, and polishing the edges formed after chamfering into transition fillets by using an abrasive machine. All defects on the surface of the square billet need to be polished and eliminated, and the aspect ratio is 1: more than 20.

(2) The head of the square billet is chamfered by 15-20 mm multiplied by 30 degrees, so that the square billet is convenient to roll and bite.

(3) Before rolling, the blank is coated with a self-made anti-oxidation coating, wherein the coating comprises the following components in percentage by weight: gluing: water = 1: 2: 3, mixing, fully stirring, and then coating on the blank with a clean surface, wherein the coating is generally coated for three times, and the coating coated for the former time is dried completely and then coated for the latter time.

(4) The TC4 titanium alloy square billet prepared by the method can be used for rolling large-coil heavy titanium alloy wire rods at high speed.

The weight of the Ti-6Al-4V titanium alloy square billet produced by the method can reach more than 500kg, the weight of the titanium alloy wire rod rolled at high speed can reach more than 500kg, and the weight of a single wire rod of the TC4 titanium alloy wire rod is far higher than that of the titanium alloy wire rod on the current market.

Example 1

A preparation method of a square billet for rolling a large-coil-weight Ti-6Al-4V alloy wire rod at a high speed comprises the following steps:

step (1), alloy coating: nominal chemical composition of TC4 alloy preparation raw materials; wherein the mass percent of the Al element is calculated as 6.1 wt%;

step (2), pressing an electrode: equally dividing the titanium sponge in the raw material in the step (1) into N parts, dividing the raw materials except the titanium sponge into N-1 parts of alloy bags, then placing one part of alloy bag between every two parts of titanium sponge from top to bottom in a mould for paving, and then pressing to form an electrode block;

step (3), welding a primary electrode: drying the pressed electrode block in the step (2), and then welding the electrode block after drying; when the electrode blocks are welded, 6 electrode blocks are welded into a long electrode in a welding mode of plasma argon arc welding outside the furnace to be used as a one-time consumable electrode;

step (4), furnace charging and vacuumizing for one time: putting the primary consumable electrode obtained in the step (3) into a vacuum consumable furnace, wherein the clearance between the primary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing granular titanium sponge as an arc starting material on the top end plane of the primary consumable electrode, sealing the furnace after the electrode is installed, and respectively starting vacuumizing until the vacuum degree in the furnace is lower than 6.7Pa after the furnace is sealed;

step (5), welding and vacuumizing in a furnace for one time: welding the primary consumable electrode and the auxiliary electrode at the connecting part of the electrode rod firmly; welding technological parameters are as follows: the arc voltage is 25V, the arc current is 3.0kA, and the welding time is 30 s; cooling after welding, and then carrying out furnace internal gas release; adjusting the lifting of the electrode rod to enable the bottom surface of the primary consumable electrode to be 200mm above the plane of the flange; placing titanium sponge on the bottom plane of the crucible as an arc striking material, then sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (6), primary arc striking smelting and cooling: after the arc is started, controlling the titanium liquid to occupy the whole molten pool within 5min, wherein the arc current in the arc striking period is only 25 percent of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 30V, and the smelting arc current is 7.0 KA; after the normal smelting period is finished, filling argon for cooling, discharging to obtain a primary VAR ingot;

step (7), cleaning flat heads: cleaning dirt and impurities on the surface of the primary VAR cast ingot, then performing flat head treatment on the cleaned primary VAR cast ingot, and turning two ends of the primary VAR cast ingot flat;

step (8), welding a secondary electrode: welding 3 primary VAR cast ingots together by adopting a welding mode of plasma argon arc welding outside the furnace to form a long electrode serving as a secondary consumable electrode;

step (9), secondary furnace charging and vacuumizing: putting the secondary consumable electrode obtained in the step (8) into a vacuum consumable furnace, wherein the clearance between the secondary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing titanium sponge as an arc striking material in the center of the upper plane, sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (10), welding and vacuumizing in a secondary furnace: welding the secondary consumable electrode with an auxiliary electrode connected with the electrode rod firmly; welding technological parameters are as follows: the welding voltage is 20V, the welding current is 2.0kA, and the welding time is 60 s; after welding, argon is filled for cooling, and then furnace internal gas release is carried out; adjusting the lifting of the electrode rod to enable the bottom surface of the secondary consumable electrode to be 200mm above the plane of the flange; placing titanium sponge as an arc striking material on the bottom plane of the crucible, then sealing the furnace, and evacuating until the vacuum degree in the furnace is lower than 3 Pa;

step (11), secondary arc striking smelting and cooling: after arcing, controlling the titanium liquid to occupy the whole molten pool within 3min, wherein the arc current in the arc striking period is 25% of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 3V, and the smelting arc current is 9.0 KA; feeding after the normal smelting period is finished until the tail of the cast ingot is flat and smooth; 3min after the completion of the feeding, filling argon, cooling and discharging to obtain a secondary VAR ingot;

step (12), peeling: naturally cooling the secondary VAR cast ingot to room temperature, and then removing oxide skin and defects on the surface layer of the cast ingot to obtain a TC4 titanium alloy round light ingot;

step (13), heating: firstly, putting a TC4 titanium alloy round polished ingot into a heating furnace for heating, gradually heating from room temperature to 1000 ℃ at the heating rate of 6.4 ℃/min during heating, enabling the maximum allowable heat preservation time at the heating temperature to be less than 4h, and lifting and forging the hot polished ingot blank after the required heat preservation time is reached to obtain a square blank for rolling a large-disc-weight Ti-6Al-4V alloy wire rod at a high speed.

Example 2

A preparation method of a square billet for rolling a large-coil-weight Ti-6Al-4V alloy wire rod at a high speed comprises the following steps:

step (1), alloy coating: nominal chemical composition of TC4 alloy preparation raw materials; wherein the mass percent of the Al element is calculated as 6.1 wt%;

step (2), pressing an electrode: equally dividing the titanium sponge in the raw material in the step (1) into N parts, dividing the raw materials except the titanium sponge into N-1 parts of alloy bags, then placing one part of alloy bag between every two parts of titanium sponge from top to bottom in a mould for paving, and then pressing to form an electrode block;

step (3), welding a primary electrode: drying the pressed electrode block in the step (2), and then welding the electrode block after drying; when the electrode blocks are welded, 6 electrode blocks are welded into a long electrode in a welding mode of plasma argon arc welding outside the furnace to be used as a one-time consumable electrode;

step (4), furnace charging and vacuumizing for one time: putting the primary consumable electrode obtained in the step (3) into a vacuum consumable furnace, wherein the clearance between the primary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing granular titanium sponge as an arc starting material on the top end plane of the primary consumable electrode, sealing the furnace after the electrode is installed, and respectively starting vacuumizing until the vacuum degree in the furnace is lower than 6.7Pa after the furnace is sealed;

step (5), welding and vacuumizing in a furnace for one time: welding the primary consumable electrode and the auxiliary electrode at the connecting part of the electrode rod firmly; welding technological parameters are as follows: the arc voltage is 25V, the arc current is 3.0kA, and the welding time is 30 s; cooling after welding, and then carrying out furnace internal gas release; adjusting the lifting of the electrode rod to enable the bottom surface of the primary consumable electrode to be 200mm above the plane of the flange; placing titanium sponge on the bottom plane of the crucible as an arc striking material, then sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (6), primary arc striking smelting and cooling: after the arc is started, controlling the titanium liquid to occupy the whole molten pool within 5min, wherein the arc current in the arc striking period is only 25 percent of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 30V, and the smelting arc current is 7.0 KA; after the normal smelting period is finished, filling argon for cooling, discharging to obtain a primary VAR ingot;

step (7), cleaning flat heads: cleaning dirt and impurities on the surface of the primary VAR cast ingot, then performing flat head treatment on the cleaned primary VAR cast ingot, and turning two ends of the primary VAR cast ingot flat;

step (8), welding a secondary electrode: welding 3 primary VAR cast ingots together by adopting a welding mode of plasma argon arc welding outside the furnace to form a long electrode serving as a secondary consumable electrode;

step (9), secondary furnace charging and vacuumizing: putting the secondary consumable electrode obtained in the step (8) into a vacuum consumable furnace, wherein the clearance between the secondary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing titanium sponge as an arc striking material in the center of the upper plane, sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (10), welding and vacuumizing in a secondary furnace: welding the secondary consumable electrode with an auxiliary electrode connected with the electrode rod firmly; welding technological parameters are as follows: the welding voltage is 20V, the welding current is 2.0kA, and the welding time is 60 s; after welding, argon is filled for cooling, and then furnace internal gas release is carried out; adjusting the lifting of the electrode rod to enable the bottom surface of the secondary consumable electrode to be 200mm above the plane of the flange; placing titanium sponge as an arc striking material on the bottom plane of the crucible, then sealing the furnace, and evacuating until the vacuum degree in the furnace is lower than 3 Pa;

step (11), secondary arc striking smelting and cooling: after arcing, controlling the titanium liquid to occupy the whole molten pool within 3min, wherein the arc current in the arc striking period is 25% of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 3V, and the smelting arc current is 9.0 KA; feeding after the normal smelting period is finished until the tail of the cast ingot is flat and smooth; 3min after the completion of the feeding, filling argon, cooling for 4h, and discharging to obtain a secondary VAR ingot;

step (12), peeling: naturally cooling the secondary VAR cast ingot to room temperature, and then removing oxide skin and defects on the surface layer of the cast ingot to obtain a TC4 titanium alloy round light ingot;

step (13), heating: firstly, putting a TC4 titanium alloy round polished ingot into a heating furnace for heating, gradually heating from room temperature to 1000 ℃ at the heating rate of 6.4 ℃/min during heating, enabling the maximum allowable heat preservation time at the heating temperature to be less than 4h, and lifting and forging the hot polished ingot blank after the required heat preservation time is reached to obtain a square blank for rolling a large-disc-weight Ti-6Al-4V alloy wire rod at a high speed.

In the step (1), the raw materials comprise an aluminum-vanadium intermediate alloy, titanium sponge, aluminum beans and aluminum foil.

In the step (2), the titanium sponge in the raw material in the step (1) is uniformly divided into 3 parts, the other raw materials except the titanium sponge are divided into 2 parts of alloy bags, then the titanium sponge, the alloy bags, the titanium sponge, the alloy bags and the titanium sponge are paved in a die from bottom to top in sequence, and then the electrode block is formed by pressing; during the pressing process, the unit pressure is increased from 0 to 18MPa, and the pressure is maintained for 15s under the unit pressure of 18MPa and then the pressure is released.

In the step (5), the cooling time after welding is 10 min; in the step (6), the cooling time is 3 h; in the step (10), the cooling time after welding is 10 min.

In the step (5) and the step (10), the welding area is more than 75%; in the step (4) and the step (9), the using amount of the arcing material is 20 g; in the step (5) and the step (10), the amount of the arcing material is 2000 g.

In the step (12), the peeling treatment is turning for 1mm, and the surface roughness after turning is less than 12.5 μm.

In the step (13), when the TC4 titanium alloy round light ingot is heated, the placing position of the TC4 titanium alloy round light ingot is 50mm away from the resistance wire and more than 200mm away from the thermocouple; forging by using a 3t air hammer; and coating an anti-oxidation coating on the surface of the square billet after forging.

In the step (11), the current is reduced by 0.5KA every 5min during feeding until the current is reduced to be below 4KA, feeding is stopped, and the whole feeding process needs 30 min.

In the step (13), in the forging process, after the deformation exceeds 20%, heavy punch forging is carried out according to the normal deformation, the deformation in the blank cogging forging stage is controlled to be 50%, the finish forging temperature is not lower than 850 ℃, when the deformation is difficult or the temperature is lower, the blank after cogging forging is required to be hung back into a furnace to be heated for 150min to carry out secondary forging until 150 square blanks are forged, and the finish forging temperature in the stage is higher than 750 ℃.

Example 3

A preparation method of a square billet for rolling a large-coil-weight Ti-6Al-4V alloy wire rod at a high speed comprises the following steps:

step (1), alloy coating: nominal chemical composition of TC4 alloy preparation raw materials; wherein the mass percent of the Al element is calculated as 6.5 wt%;

step (2), pressing an electrode: equally dividing the titanium sponge in the raw material in the step (1) into N parts, dividing the raw materials except the titanium sponge into N-1 parts of alloy bags, then placing one part of alloy bag between every two parts of titanium sponge from top to bottom in a mould for paving, and then pressing to form an electrode block;

step (3), welding a primary electrode: drying the pressed electrode block in the step (2), and then welding the electrode block after drying; when the electrode blocks are welded, 7 electrode blocks are welded into a long electrode in a welding mode of plasma argon arc welding outside the furnace to be used as a one-time consumable electrode;

step (4), furnace charging and vacuumizing for one time: putting the primary consumable electrode obtained in the step (3) into a vacuum consumable furnace, wherein the clearance between the primary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing granular titanium sponge as an arc starting material on the top end plane of the primary consumable electrode, sealing the furnace after the electrode is installed, and respectively starting vacuumizing until the vacuum degree in the furnace is lower than 6.7Pa after the furnace is sealed;

step (5), welding and vacuumizing in a furnace for one time: welding the primary consumable electrode and the auxiliary electrode at the connecting part of the electrode rod firmly; welding technological parameters are as follows: the arc voltage is 35V, the arc current is 5.0kA, and the welding time is 50 s; cooling after welding, and then carrying out furnace internal gas release; adjusting the lifting of the electrode rod to enable the bottom surface of the primary consumable electrode to be 200mm above the plane of the flange; placing titanium sponge on the bottom plane of the crucible as an arc striking material, then sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (6), primary arc striking smelting and cooling: after the arc is started, controlling the titanium liquid to occupy the whole molten pool within 8min, wherein the arc current in the arc striking period is only 60% of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 33V, and the smelting arc current is 78.0 KA; after the normal smelting period is finished, filling argon for cooling, discharging to obtain a primary VAR ingot;

step (7), cleaning flat heads: cleaning dirt and impurities on the surface of the primary VAR cast ingot, then performing flat head treatment on the cleaned primary VAR cast ingot, and turning two ends of the primary VAR cast ingot flat;

step (8), welding a secondary electrode: welding 3 primary VAR cast ingots together by adopting a welding mode of plasma argon arc welding outside the furnace to form a long electrode serving as a secondary consumable electrode;

step (9), secondary furnace charging and vacuumizing: putting the secondary consumable electrode obtained in the step (8) into a vacuum consumable furnace, wherein the clearance between the secondary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing titanium sponge as an arc striking material in the center of the upper plane, sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (10), welding and vacuumizing in a secondary furnace: welding the secondary consumable electrode with an auxiliary electrode connected with the electrode rod firmly; welding technological parameters are as follows: the welding voltage is 30V, the welding current is 5.0kA, and the welding time is 90 s; after welding, argon is filled for cooling, and then furnace internal gas release is carried out; adjusting the lifting of the electrode rod to enable the bottom surface of the secondary consumable electrode to be 200mm above the plane of the flange; placing titanium sponge as an arc striking material on the bottom plane of the crucible, then sealing the furnace, and evacuating until the vacuum degree in the furnace is lower than 3 Pa;

step (11), secondary arc striking smelting and cooling: after arcing, controlling the titanium liquid to occupy the whole molten pool within 6min, wherein the arc current in the arc striking period is 60% of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 34V, and the smelting arc current is 10.0 KA; feeding after the normal smelting period is finished until the tail of the cast ingot is flat and smooth; 5min after the completion of the feeding, filling argon, cooling for 4h, and discharging to obtain a secondary VAR ingot;

step (12), peeling: naturally cooling the secondary VAR cast ingot to room temperature, and then removing oxide skin and defects on the surface layer of the cast ingot to obtain a TC4 titanium alloy round light ingot;

step (13), heating: firstly, putting a TC4 titanium alloy round polished ingot into a heating furnace for heating, gradually heating from room temperature to 1200 ℃ at the heating rate of 6.4 ℃/min during heating, enabling the allowed maximum heat preservation time at the heating temperature to be less than 4h, and lifting and forging the hot polished ingot blank after the required heat preservation time is reached to obtain a square blank for rolling a large-disc-weight Ti-6Al-4V alloy wire rod at a high speed.

In the step (1), the raw materials comprise an aluminum-vanadium intermediate alloy, titanium sponge, aluminum beans and aluminum foil.

In the step (2), the titanium sponge in the raw material in the step (1) is uniformly divided into 3 parts, the other raw materials except the titanium sponge are divided into 2 parts of alloy bags, then the titanium sponge, the alloy bags, the titanium sponge, the alloy bags and the titanium sponge are paved in a die from bottom to top in sequence, and then the electrode block is formed by pressing; during the pressing process, the unit pressure is increased from 0 to 18MPa, and the pressure is maintained for 20s under the unit pressure of 18MPa and then the pressure is released.

In the step (5), the cooling time after welding is 10 min; in the step (6), the cooling time is 3 h; in the step (10), the cooling time after welding is 10 min.

In the step (5) and the step (10), the welding area is more than 75%; in the step (4) and the step (9), the using amount of the arcing material is 20 g; in the step (5) and the step (10), the amount of the arcing material is 2000 g.

In the step (12), the peeling treatment is turning for 3mm, and the surface roughness after turning is less than 12.5 μm.

In the step (13), when the TC4 titanium alloy round light ingot is heated, the placing position of the TC4 titanium alloy round light ingot is 70mm away from the resistance wire and more than 200mm away from the thermocouple; forging by using a 3t air hammer; and coating an anti-oxidation coating on the surface of the square billet after forging.

In the step (11), the current is reduced by 0.5KA every 5min during feeding until the current is reduced to be below 4KA, feeding is stopped, and the whole feeding process needs 50 min.

In the step (13), in the forging process, after the deformation exceeds 20%, heavy punch forging is carried out according to the normal deformation, the deformation in the blank cogging forging stage is controlled to be 75%, the finish forging temperature is not lower than 850 ℃, when the deformation is difficult or the temperature is lower, the blank after cogging forging is required to be hung back into a furnace to be heated for 200min to carry out secondary forging until 150 square billets are forged, and the finish forging temperature in the stage is higher than 750 ℃.

Example 4

A preparation method of a square billet for rolling a large-coil-weight Ti-6Al-4V alloy wire rod at a high speed comprises the following steps:

step (1), alloy coating: nominal chemical composition of TC4 alloy preparation raw materials; wherein the mass percent of the Al element is calculated as 6.35 wt%;

step (2), pressing an electrode: equally dividing the titanium sponge in the raw material in the step (1) into N parts, dividing the raw materials except the titanium sponge into N-1 parts of alloy bags, then placing one part of alloy bag between every two parts of titanium sponge from top to bottom in a mould for paving, and then pressing to form an electrode block;

step (3), welding a primary electrode: drying the pressed electrode block in the step (2), and then welding the electrode block after drying; when the electrode blocks are welded, 6 electrode blocks are welded into a long electrode in a welding mode of plasma argon arc welding outside the furnace to be used as a one-time consumable electrode;

step (4), furnace charging and vacuumizing for one time: putting the primary consumable electrode obtained in the step (3) into a vacuum consumable furnace, wherein the clearance between the primary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing granular titanium sponge as an arc starting material on the top end plane of the primary consumable electrode, sealing the furnace after the electrode is installed, and respectively starting vacuumizing until the vacuum degree in the furnace is lower than 6.7Pa after the furnace is sealed;

step (5), welding and vacuumizing in a furnace for one time: welding the primary consumable electrode and the auxiliary electrode at the connecting part of the electrode rod firmly; welding technological parameters are as follows: the arc voltage is 30V, the arc current is 4.0kA, and the welding time is 40 s; cooling after welding, and then carrying out furnace internal gas release; adjusting the lifting of the electrode rod to enable the bottom surface of the primary consumable electrode to be 200mm above the plane of the flange; placing titanium sponge on the bottom plane of the crucible as an arc striking material, then sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (6), primary arc striking smelting and cooling: after the arc is started, controlling the titanium liquid to occupy the whole molten pool within 6min, wherein the arc current in the arc striking period is only 40% of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 32V, and the smelting arc current is 7.5 KA; after the normal smelting period is finished, filling argon for cooling, discharging to obtain a primary VAR ingot;

step (7), cleaning flat heads: cleaning dirt and impurities on the surface of the primary VAR cast ingot, then performing flat head treatment on the cleaned primary VAR cast ingot, and turning two ends of the primary VAR cast ingot flat;

step (8), welding a secondary electrode: welding 3 primary VAR cast ingots together by adopting a welding mode of plasma argon arc welding outside the furnace to form a long electrode serving as a secondary consumable electrode;

step (9), secondary furnace charging and vacuumizing: putting the secondary consumable electrode obtained in the step (8) into a vacuum consumable furnace, wherein the clearance between the secondary consumable electrode and a crucible in the vacuum consumable furnace is not less than 30 mm; placing titanium sponge as an arc striking material in the center of the upper plane, sealing the furnace, and vacuumizing until the vacuum degree in the furnace is lower than 3 Pa;

step (10), welding and vacuumizing in a secondary furnace: welding the secondary consumable electrode with an auxiliary electrode connected with the electrode rod firmly; welding technological parameters are as follows: the welding voltage is 25V, the welding current is 3.0kA, and the welding time is 70 s; after welding, argon is filled for cooling, and then furnace internal gas release is carried out; adjusting the lifting of the electrode rod to enable the bottom surface of the secondary consumable electrode to be 200mm above the plane of the flange; placing titanium sponge as an arc striking material on the bottom plane of the crucible, then sealing the furnace, and evacuating until the vacuum degree in the furnace is lower than 3 Pa;

step (11), secondary arc striking smelting and cooling: after the arc is started, controlling the titanium liquid to occupy the whole molten pool within 4min, wherein the arc current in the arc striking period is 40% of that in normal smelting; entering a normal smelting period after arc striking is finished, wherein the smelting voltage in the normal smelting period is 33V, and the smelting arc current is 9.5 KA; feeding after the normal smelting period is finished until the tail of the cast ingot is flat and smooth; 4min after the completion of the feeding, filling argon, cooling for 4h, and discharging to obtain a secondary VAR ingot;

step (12), peeling: naturally cooling the secondary VAR cast ingot to room temperature, and then removing oxide skin and defects on the surface layer of the cast ingot to obtain a TC4 titanium alloy round light ingot;

step (13), heating: firstly, putting a TC4 titanium alloy round polished ingot into a heating furnace for heating, gradually heating from room temperature to 1100 ℃ at the heating rate of 6.4 ℃/min during heating, enabling the maximum allowable heat preservation time at the heating temperature to be less than 4h, and lifting and forging the hot polished ingot blank after the required heat preservation time is reached to obtain a square blank for rolling a large-disc-weight Ti-6Al-4V alloy wire rod at a high speed.

In the step (1), the raw materials comprise an aluminum-vanadium intermediate alloy, titanium sponge, aluminum beans and aluminum foil.

In the step (2), the titanium sponge in the raw material in the step (1) is uniformly divided into 3 parts, the other raw materials except the titanium sponge are divided into 2 parts of alloy bags, then the titanium sponge, the alloy bags, the titanium sponge, the alloy bags and the titanium sponge are paved in a die from bottom to top in sequence, and then the electrode block is formed by pressing; during the pressing process, the unit pressure is increased from 0 to 18MPa, and the pressure is maintained for 18s under the unit pressure of 18MPa and then the pressure is released.

In the step (5), the cooling time after welding is 10 min; in the step (6), the cooling time is 3 h; in the step (10), the cooling time after welding is 10 min.

In the step (5) and the step (10), the welding area is more than 75%; in the step (4) and the step (9), the using amount of the arcing material is 20 g; in the step (5) and the step (10), the amount of the arcing material is 2000 g.

In the step (12), the peeling treatment is turning for 2mm, and the surface roughness after turning is less than 12.5 μm.

In the step (13), when the TC4 titanium alloy round light ingot is heated, the placing position of the TC4 titanium alloy round light ingot is 60mm away from the resistance wire and more than 200mm away from the thermocouple; forging by using a 3t air hammer; and coating an anti-oxidation coating on the surface of the square billet after forging.

In the step (11), the current is reduced by 0.5KA every 5min during feeding until the current is reduced to be below 4KA, feeding is stopped, and the whole feeding process needs 40 min.

In the step (13), in the forging process, after the deformation exceeds 20%, heavy punch forging is carried out according to the normal deformation, the deformation in the blank cogging forging stage is controlled to be 65%, the finish forging temperature is not lower than 850 ℃, when the deformation is difficult or the temperature is lower, the blank after cogging forging is required to be hung back into a furnace to be heated for 180min to carry out secondary forging until 150 square billets are forged, and the finish forging temperature in the stage is higher than 750 ℃.

Examples of the applications

In this example, a 500kg grade 150X 5050mm (width X thickness X length) titanium alloy square billet with a mark TC4 (Ti-6 Al-4V) is taken as an example:

(1) taking the intermediate value of Al element and V element required by TC4 titanium alloy national standard as a reference value, namely Al: 6.125%, V: 4.0 percent;

(2) the actual value of the Al element is higher than the reference value by 0.075 percent, and the actual value of the V element is calculated as the same as the reference value and is taken as a nominal component;

(3) proportioning according to the established nominal chemical composition Ti-6.2Al-4.0V, calculating the weight of the sponge titanium, the aluminum-vanadium alloy and the aluminum bean (aluminum foil) which need to be weighed respectively according to the composition, uniformly mixing the intermediate aluminum-vanadium alloy and the aluminum bean (aluminum foil), and packaging into an alloy bag.

(4) And dividing the raw materials into three equal parts according to the required sponge titanium amount in the raw material proportion, then respectively weighing each equal part of the sponge titanium, marking the equal parts as a first equal part, a second equal part and a third equal part, and reserving the equal parts as pressed electrode blocks after weighing. Pouring the weighed first-part titanium sponge into a mold, flatly paving the mold, flatly placing an alloy bag in the center of the mold, pouring the second-part titanium sponge, flatly paving the poured second-part titanium sponge, putting the second-part alloy bag in the center of the mold, finally pouring the third-part titanium sponge and flatly paving the third-part titanium sponge, and finishing material distribution; then slowly descending a pressure head of the hydraulic press to start pressing an electrode block, buckling the end heads of the two steel ropes on a pressing die while the pressure head descends slowly, gradually increasing the unit pressure from 0 to 18MPa when the pressure head begins to contact the titanium sponge, maintaining the pressure for 15-20 s under the unit pressure of 18MPa, releasing the pressure after the required pressure maintaining time is reached, slowly lifting the pressing die and the pressure head together under the action of the steel wire rope after a pointer on a pressure gauge returns to zero, pushing a cushion block to the position right below the pressing die after the pressing die and the pressure head are lifted to a certain height, and descending the pressing die to enable the pressing die to just fall on the cushion block; then manually pushing the cart to a position right below the pressure head, lowering the pressure head to press the pressed electrode block out of the pressing die and drop the electrode block into the cart, then withdrawing the cart, taking out the electrode block, weighing and recording; and then appropriately lifting the pressing die to conveniently and smoothly withdraw the cushion block, lowering the pressing die to a station after withdrawing the cushion block, taking the two ends of the steel rope from the pressing die, and continuing the operation to press a next electrode block, wherein the specification of the pressed single electrode block is phi 150 multiplied by 350mm, and the weight of the pressed single electrode block is 25 kg.

(5) And drying the pressed electrode block, and then welding. When welding electrode blocks, 6 electrode blocks are welded into a long electrode (primary electrode) by adopting a welding mode of plasma argon arc welding outside the furnace.

(6) And (3) charging the welded primary electrode, sealing the furnace after charging, and vacuumizing to check whether water, electricity, instruments and meters, high-pressure air and compressed air are normal or not before vacuumizing. The vacuum pump body can be started up through checking, when the vacuum degree reaches 1000Pa, the small Roots pump is started up, when the furnace body is pumped to 400Pa, the large Roots pump is started up, when the vacuum degree of the furnace body reaches 133Pa, the oil booster pump can be preheated, the oil temperature can reach 240-250 ℃, and the oil booster pump can enter a working state.

(7) When the vacuum degree in the furnace is lower than 6.7Pa and the air leakage rate is less than 2Pa/min, the welding in the furnace can be carried out. Furnace welding technological parameters: the welding voltage is 29-35V, the welding current is 4.0-5.0 kA, the welding time is 30-50 s, and the cooling time is 15 min.

(8) After the furnace is sealed, a mechanical pump is started to evacuate the furnace body, when the vacuum degree reaches 1000Pa, a small Roots pump is started, when the vacuum degree reaches 400Pa, a large Roots pump is started, when the vacuum degree of the furnace body reaches 133Pa, an oil booster pump can be preheated, the pump is kept started for 60-90 min, the oil temperature can reach 240-250 ℃, the oil booster pump can enter a working state, and at the moment, the vacuum degree in the furnace is lower than 3 Pa. And (5) detecting the leakage of the furnace body, wherein the leakage rate is less than 0.6 Pa/min.

(9) After the arc is started, the full molten pool is filled up by using the transition time of 5-8 min, the power supply system in the arc striking period is much lower than the power of normal smelting, and the arc current in the arc striking period is only 25% -60% of the normal smelting.

(10) And entering a normal smelting period required by the process after arc striking is finished, wherein the smelting voltage in the smelting period is 31-33V, and the smelting current is 7.0-8.0 KA. The smelting period can remove gas, metallic inclusions and various harmful impurities, homogenize alloy components, improve the crystal structure and eliminate various defects.

(11) And after the normal smelting period is finished, the ingot is required to be filled with argon for cooling for 3 hours. When argon is filled, the valve is closed, the oil booster pump and the roots pump are stopped to operate, and the mechanical pump is still in a normal operation state. In order to prevent the oil of the booster pump from being oxidized, the mechanical pump can be stopped after the oil booster pump is cooled for 90 minutes; and after the specified cooling time is reached, deflating, disassembling the furnace, lowering the crucible base, lifting out the ingot, and marking information such as the brand, the ingot number, the weight, the specification and the like of the ingot on the feeding end face of the VAR ingot.

(12) Cleaning dirt and impurities on the surface of the VAR ingot by using an ingot cleaning machine, and brushing the oxide on the surface of the ingot by using a steel wire wheel for surface oxides which cannot be cleaned by the ingot cleaning machine; in order to weld the secondary electrode conveniently, the flat head treatment needs to be carried out on the smelted primary VAR ingot, the two ends of the ingot are turned to be flat, the burrs are cut off by a sawing machine or a lathe, and the end face of the head of the primary VAR ingot after the flat head treatment is 4-6 mm higher than the feeding end face. When in sawing, the inclination of the saw cut is less than 2 mm.

(13) After cleaning and flatting the smelted primary VAR ingots, 3 primary VAR ingots are welded together by adopting a welding mode of plasma argon arc welding outside the furnace to form a long electrode (secondary electrode) which is used as a consumable electrode for smelting secondary VAR ingots. Welding by adopting plasma argon arc welding outside the furnace, wherein the welding seam position is required not to be oxidized, and the oxidized part is required to be polished and removed; the bending degree of the electrode is controlled within 3 mm/m; the smaller the gap, the better when two VAR ingots are butt welded once.

(14) Selecting a crucible specification meeting the process requirement, and cleaning; after the crucible is prepared, clamping the secondary electrode by an ingot supporting trolley, vertically placing the secondary electrode at the central position of the crucible base, adjusting the center, lifting the trolley, finding the central position of the electrode in the crucible, ensuring that the gap between the electrode and the crucible is more than 30mm, and fixing the electrode by a wood wedge; 20g of sponge titanium is placed in the center of the upper plane of the consumable electrode to be used as an arc striking material, and the consumable electrode can be sealed and vacuumized after being installed.

(15) Checking water, electricity, instruments, compressed air and the like, sending electricity of a control system after checking the water, electricity, instruments, compressed air and the like to be normal, starting pumps and valves of a vacuum system to begin evacuation, starting a pumping body of a mechanical pump, starting a small roots pump when the vacuum degree of the furnace body reaches 1000Pa, starting a large roots pump when the furnace body is pumped to 400Pa, preheating an oil booster pump when the vacuum degree of the furnace body reaches 133Pa, maintaining the pump to be started for 60-90 min, enabling the oil temperature to reach 240-250 ℃, enabling the oil booster pump to enter a working state, enabling the vacuum degree in the furnace to be lower than 3Pa at the moment, testing the gas leakage rate to be not more than 0.6Pa/min, and carrying out furnace welding: the welding voltage is 23-25V, the welding current is 2.0-5.0 kA, the welding time is 60-90 s, and the cooling time is 20 min. After cooling, deflating the furnace, and preparing for opening the furnace; checking the welding condition, wherein the welding area is more than 75%, otherwise, the welding can be started due to the overheating of large current, plasma argon arc welding repair welding is adopted, the oxide generated needs to be cleaned, the nubs welded in the furnace are cleaned, otherwise, the side arc is easy to generate, and the crucible is punctured. Cleaning titanium particles, splashed objects and dust on a crucible flange and a sealing ring; lifting the electrode rod to a certain height, putting a proper amount of sponge titanium on the bottom of the crucible as an arc striking material, and measuring the distance between the bottom surface of the consumable electrode (secondary electrode) and the bottom plane of the crucible to be more than 100mm to be used as an arc striking gap; then sealing the furnace and evacuating. After the furnace is sealed, a mechanical pump is started to vacuumize the furnace body, when the vacuum degree reaches 1000Pa, a small roots pump is started, when the vacuum degree reaches 400Pa, a large roots pump is started, when the vacuum degree of the furnace body reaches 133Pa, an oil booster pump can be preheated, the pump is kept started for 60-90 min, the oil temperature can reach 240-250 ℃, the oil booster pump can enter a working state, and at the moment, the vacuum degree in the furnace is lower than 3 Pa. And (4) detecting the leakage of the furnace body, wherein the leakage rate is not more than 0.6Pa/min, and the high pressure can be distributed.

(16) Slowly lowering the electrode rod to short circuit arc starting, slightly lifting the electrode rod, controlling the arc pressure, keeping the arc length, filling the whole molten pool with the transition time of 3-6 min, quickly forming the molten pool and reducing the impact of the electric arc on the crucible bottom; the power supply system in the arc striking period is much smaller than the power of normal smelting, and the arc current in the arc striking period is only 25-60% of that in the normal smelting. And entering a normal smelting period required by the process after arc striking is finished, wherein the smelting voltage in the smelting period is 32-34V, and the smelting current is 9.0-10.0 KA.

(17) After the normal smelting period is finished, feeding is carried out, and the tail of the cast ingot is leveled.

(18) And 3-5 min after the completion of the feeding, closing the valve, and filling argon into the cast ingot for cooling for 4 h. When argon is filled, the valve is closed, the oil booster pump and the roots pump stop running, and the mechanical pump is in a normal running state. In order to prevent the oil of the booster pump from being oxidized, the mechanical pump can be stopped after the oil booster pump is cooled for 90 min; and after the specified cooling time is reached, deflating, disassembling the furnace, lowering the crucible base, lifting out the ingot, and marking information such as the brand, the ingot number, the weight, the specification and the like of the ingot on the feeding end face of the secondary VAR ingot.

(19) After the secondary VAR cast ingot is lifted out of the vacuum consumable furnace, residual temperature still remains, the secondary VAR cast ingot needs to be slowly cooled to room temperature in an air cooling mode, the cooled secondary VAR rough ingot needs to be turned and scalped, generally 1-3 mm turning can be carried out to remove oxide skin and defects on the surface layer of the cast ingot, a round polished ingot of TC4 titanium alloy is obtained after scalping, and the specification of the round polished ingot after scalping is phi 380 multiplied by 2000 mm.

(20) The surface processing quality of the TC4 titanium alloy round polished ingot after peeling needs to be checked, and the surface roughness of the round ingot after turning is less than 12.5 mu m.

(21) Firstly, placing a TC4 titanium alloy round light ingot in a heating furnace for heating, gradually heating from room temperature to 1000-1200 ℃ at the heating rate of 6.4 ℃/min, wherein the allowable maximum heat preservation time at the heating temperature is less than 4h, and lifting and forging the hot light ingot blank after the required heat preservation time is reached;

(22) the heated smooth ingot blank was lifted out on a 3t air hammer for free cogging forging. The principle of small deformation, light weight, quick beating and frequent overturning is followed in the initial cogging stage, when the deformation exceeds 20%, heavy weight forging can be carried out according to the normal deformation, the deformation in the blank cogging forging stage is controlled to be 50-75%, and the final forging temperature is not lower than 850 ℃. When the deformation is substantially complete or the temperature is low, the amount of deformation should be gradually reduced to avoid cracking.

(23) When the deformation is difficult or the temperature is low, the cogging forged blank needs to be lifted back into a furnace to be heated for 150-200 min for secondary forging until a Ti-6Al-4V titanium alloy square billet with the width of 150mm, the thickness of 150mm and the length of Lmm (L is larger than 5000 mm) is forged, the weight of a single titanium alloy square billet is larger than 500kg, and the Ti-6Al-4V titanium alloy wire rod with large coil weight can be obtained after the square billet is rolled at high speed.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.