阅读说明：本技术 一种用真空自耗电弧炉回收重熔钛或钛合金残料的方法 (Method for recycling remelting titanium or titanium alloy scraps by using vacuum consumable electrode arc furnace ) 是由 孙建月 杨国庆 李萍 陈妍 于 2020-10-29 设计创作，主要内容包括：一种用真空自耗电弧炉回收重熔钛或钛合金残料的方法,包括如下步骤：1)将钛或钛合金残料进行回收；2)对所述钛或钛合金残料进行表面清洁,得可重熔残料；3)利用氩气保护的等离子弧焊接方式,将所述可重熔残料焊接成自耗电极,焊接的过程中,使用设有焊点保护区的焊接保护罩进行焊接,保证焊点为银白色或浅黄色；4)将所述自耗电极装入真空自耗电弧炉中进行熔炼。本发明可将钛及钛合金残料进行100％回收利用,生产出成分均一性良好,洁净度高的合格铸锭。实现钛及钛合金残料的循环再利用,减少资源浪费并提高经济效益。(A method for recovering remelting titanium or titanium alloy scraps by using a vacuum consumable electric arc furnace comprises the following steps: 1) recovering titanium or titanium alloy residue; 2) cleaning the surface of the titanium or titanium alloy residue to obtain a remelting residue; 3) welding the remelting residues into a consumable electrode by using a plasma arc welding mode under the protection of argon, and welding by using a welding protective cover provided with a welding spot protective area in the welding process to ensure that the welding spot is silvery white or light yellow; 4) and putting the consumable electrode into a vacuum consumable electric arc furnace for smelting. The invention can recycle 100% of titanium and titanium alloy residue, and produce qualified cast ingots with good component uniformity and high cleanliness. Realizes the recycling of titanium and titanium alloy scraps, reduces resource waste and improves economic benefits.)

1. A method for recycling remelting titanium or titanium alloy scraps by using a vacuum consumable electrode arc furnace is characterized by comprising the following steps:

1) recovering titanium or titanium alloy residue;

2) cleaning the surface of the titanium or titanium alloy residue to obtain a remelting residue;

3) welding the remelting residues into a consumable electrode by using a plasma arc welding mode under the protection of argon, and welding by using a welding protective cover provided with a welding spot protective area in the welding process to ensure that the welding spot is silvery white or light yellow;

4) putting the consumable electrode into a vacuum consumable electric arc furnace for smelting;

the welding protection cover with welding spot protected area's structure does, be equipped with welding spot protected area, argon gas entry and argon gas export on the welding protection cover, the welding spot protected area is for locating the recess on protection cover surface, the argon gas export is located in the recess.

2. The method of claim 1, wherein the number of times of melting is not less than 2, the degree of vacuum of each melting is kept below 6.7Pa, and the gas leakage rate is less than 1.8 Pa/min.

3. The method for recycling remelting titanium and titanium alloy scraps by using a vacuum consumable electrode arc furnace according to claim 1 or 2, wherein during the smelting in the vacuum consumable electrode arc furnace, the arc starting voltage is controlled to be 20-30V, and the arc starting current is controlled to be 3-6 KA; and controlling the voltage to be 25-35V in the smelting process.

4. The method of claim 3, wherein the scrap material is a titanium alloy scrap material,

for TA1, the diameter of an electrode is 310-330 mm during primary ingot smelting, and the smelting current is 7-10 KA; the diameter of an electrode is 370-390 mm during secondary ingot smelting, the current is 12-15 KA, the diameter of the electrode is 430-450 mm during tertiary ingot smelting, and the current is 16-19 KA;

or, aiming at TC4, the diameter of an electrode is 310-330 mm during primary ingot smelting, and the smelting current is 6-9 KA; the diameter of the electrode is 370-390 mm during secondary ingot smelting, the current is 10-14 KA, the diameter of the electrode is 430-450 mm during tertiary ingot smelting, and the current is 15-18 KA.

5. The method of claim 1 or 4, wherein the feeding operation during smelting in the consumable electrode vacuum arc furnace is: feeding ingots with the diameter of 440mm and ingots with the diameter of 520mm when the weight of the reference residual electrode is 100-150 kg; reducing the current to 6-8 KA within 10-30 minutes by 0.5-1 KA each time, and then increasing the melting time each time the current is reduced; the feeding process of the ingot with the diameter of 440mm is finished within 1.5-2.0 hours, and the feeding process of the ingot with the diameter of 520mm is finished within 2-2.5 hours.

6. The method for recycling the remelting titanium and titanium alloy scraps by using the vacuum consumable electrode arc furnace as claimed in claim 1, wherein in the welding process by using the argon protection plasma arc welding mode, the voltage of the welding machine is controlled to be 35-40V, the current is controlled to be 300-350A, and the argon flow is controlled to be 4-15L/min.

7. The method of claim 1, wherein the protective enclosure is a hollow shell and the argon inlet is located on an outer wall of the shell.

8. The method of claim 1, wherein the trough is rectangular and the argon outlets are distributed on the side wall and the bottom of the trough.

9. The method for recycling remelting titanium or titanium alloy scraps by using a vacuum consumable electric arc furnace as claimed in claim 1, wherein the specific operation of recycling titanium or titanium alloy scraps is as follows: and classifying and recycling according to different brands, furnace numbers and sources of the residual materials.

10. The method for recycling and remelting titanium or titanium alloy scraps by using a vacuum consumable electric arc furnace as claimed in claim 1, wherein the specific operation of surface cleaning the titanium or titanium alloy scraps is to immerse the scraps to be remelted in an acidic or alkaline solution, remove oxide scales on the surfaces of the scraps, and remove residual oxides on the surfaces of the scraps by polishing, sand blasting and ball blasting; then the residue material after the oxide treatment is placed in clean water or a cleaning agent solution with a certain concentration for cleaning, and oil stains or other foreign matters on the surface are removed; and finally, placing the cleaned residual materials in a dryer for drying or naturally airing.

Technical Field

The invention belongs to the technical field of metal smelting, and particularly relates to a method for recycling remelting titanium or titanium alloy scraps by using a vacuum consumable electrode arc furnace.

Background

Titanium and titanium alloy have excellent properties such as high specific strength, corrosion resistance and the like, and are widely applied to the fields of aviation, aerospace, ships, weapons, chemical engineering, medical treatment and the like. Due to the particularity of the titanium material, the yield of parts is only 50-60%, and a large amount of titanium and titanium alloy residues are generated, so that the research on the recycling method of the titanium and titanium alloy residues has great social and economic benefits.

The production of titanium and titanium alloy ingots by a vacuum consumable electrode arc furnace (VAR) is a production method which has the widest industrial application range and the largest scale at present. The furnace has a crystallizer which is housed in a water-cooled jacket and connected to the positive pole of a smelting power supply. The negative pole of the power supply is connected to a piston, i.e., a "draw bar," which is introduced into the furnace by a sliding vacuum seal. The electrode to be melted is clamped on the base of the control piston and, after the evacuation of the hearth, the descending electrode is arc-struck with a metal pad of the same material at the bottom of the crystallizer. When the electrode melts as a result of the manual power supply, the piston can be lowered by means of a hydraulic control system in order to keep the distance between the electrode and the molten bath formed thereby constant. As melting continues, a new ingot is gradually formed in the crystallizer. The smelting method can effectively remove volatile impurities and gases, and titanium alloy ingots with uniform components and high purity can be obtained by 2-3 times of smelting.

The titanium and titanium alloy residual materials mainly come from a dead head of ingot sawing, a head, a tail and a trimming edge of a semi-finished blank and unqualified products generated in each process, and the residual materials are different in size and shape. The conventional method for manufacturing the electrode in a binding mode has unsafe factors such as block falling and the like in the smelting process, the method for pressing the electrode by mixing the residual material and the sponge titanium through the mold has long production process, the mold manufacturing cost is high, and the requirement of large-scale production cannot be met.

Disclosure of Invention

Aiming at the problems in the prior art in recovering remelted titanium alloy, the invention provides a method for recovering remelted titanium or titanium alloy scraps by using a vacuum consumable electrode electric arc furnace, which comprises the following steps:

1) recovering titanium or titanium alloy residue;

2) cleaning the surface of the titanium or titanium alloy residue to obtain a remelting residue;

3) welding the remelting residues into a consumable electrode by using a plasma arc welding mode under the protection of argon, and welding by using a welding protective cover provided with a welding spot protective area in the welding process to ensure that the welding spot is silvery white or light yellow;

4) putting the consumable electrode into a vacuum consumable electric arc furnace for smelting;

the welding protection cover with welding spot protected area's structure does, be equipped with welding spot protected area, argon gas entry and argon gas export on the welding protection cover, the welding spot protected area is for locating the recess on protection cover surface, the argon gas export is located in the recess.

The main technical problem in the process of recycling and remelting titanium or titanium alloy is that recycled titanium scraps which are reused are different in size and shape, various defects exist in the process of pressing electrodes by a mould in a binding mode or the mode of mixing the scraps and titanium sponge in the prior art, the remelting scraps are prepared into consumable electrodes in an argon protection plasma arc welding mode, welding spots are easy to oxidize in the welding process, and therefore the uniform and ideal materials cannot be obtained after subsequent remelting.

Preferably, in the process of smelting in the vacuum consumable electrode arc furnace, the smelting times are not less than 2 times, the vacuum degree of each smelting is kept below 6.7Pa, and the air leakage rate is less than 1.8 Pa/min. The parameters of the vacuum degree and the air leakage rate can ensure the good vacuum degree in the furnace and ensure that the components of the smelted cast ingot meet the national standard requirements.

Preferably, in the process of smelting in the vacuum consumable electrode arc furnace, the arcing voltage is controlled to be 20-30V, and the arcing current is controlled to be 3-6 KA; and controlling the voltage to be 25-35V in the smelting process. The parameter can ensure the stability of the inner part of a molten pool in the arc starting stage, reduce the bottom defect caused by chilling and ensure the operation safety to the maximum extent.

Preferably, for TA1, the diameter of an electrode is 310-330 mm during primary ingot smelting, and the smelting current is 7-10 KA; the diameter of an electrode is 370-390 mm during secondary ingot smelting, the current is 12-15 KA, the diameter of the electrode is 430-450 mm during tertiary ingot smelting, and the current is 16-19 KA;

preferably, for TC4, the diameter of an electrode is 310-330 mm during primary ingot smelting, and the smelting current is 6-9 KA; the diameter of the electrode is 370-390 mm during secondary ingot smelting, the current is 10-14 KA, the diameter of the electrode is 430-450 mm during tertiary ingot smelting, and the current is 15-18 KA. The ingot components obtained by ingot smelting by using the parameters have good uniformity and higher purity degree.

The specific smelting process parameters of the two metals are shown in the table 1:

TABLE 1 melting Process parameters

Preferably, the feeding operation in the process of smelting in the vacuum consumable electrode arc furnace is: feeding ingots with the diameter of 440mm and ingots with the diameter of 520mm when the weight of the reference residual electrode is 100-150 kg; reducing the current to 6-8 KA within 10-30 minutes by 0.5-1 KA each time, and then increasing the melting time each time the current is reduced; the feeding process of the ingot with the diameter of 440mm is finished within 1.5-2.0 hours, and the feeding process of the ingot with the diameter of 520mm is finished within 2-2.5 hours. In the final stage of finished product smelting, feeding operation is carried out by using the parameters, so that the shrinkage cavity depth of the cast ingot can be reduced, and the yield of the cast ingot is improved.

Preferably, in the process of welding by a plasma arc welding mode under the protection of argon, the voltage of a welding machine is controlled to be 35-40V, the current is controlled to be 300-350A, and the flow of argon is controlled to be 4-15L/min. The electrode welding by using the parameters can ensure that the welding spot presents white and light yellow in the welding process, and reduce the risk of oxide inclusion brought into the ingot casting by welding spot oxidation.

Preferably, the protective cover is a hollow shell, and the argon inlet is formed in the outer wall of the shell.

Preferably, the groove is a cuboid, and the argon outlets are distributed on the side wall and the bottom surface of the groove. The structure is favorable for providing comprehensive argon protection for welding points.

Preferably, the specific operation of recovering the titanium or titanium alloy residue is as follows: and classifying and recycling according to different brands, furnace numbers and sources of the residual materials.

Preferably, the specific operation of cleaning the surface of the titanium or titanium alloy residue is to soak the residue to be remelted in an acidic or alkaline solution to remove oxide skin on the surface of the residue, and then remove the residual oxide on the surface of the residue by polishing, sand blasting and shot blasting; then the residue material after the oxide treatment is placed in clean water or a cleaning agent solution with a certain concentration for cleaning, and oil stains or other foreign matters on the surface are removed; and finally, placing the cleaned residual materials in a dryer for drying or naturally airing.

The invention has the following beneficial effects:

1) the method can recycle 100% of titanium and titanium alloy residues, and produce qualified cast ingots with good component uniformity and high cleanliness by VAR. Realizes the recycling of titanium and titanium alloy scraps, reduces resource waste and improves economic benefits.

2) The method of the invention has simple operation and low cost, and is beneficial to large-scale industrial popularization and application.

Drawings

FIG. 1 is a consumable electrode prepared from processed and qualified scrap by plasma arc welding under argon shield;

FIG. 2 is a finished ingot with good surface quality obtained by smelting with the method of the invention;

FIG. 3 is a schematic view of a weld enclosure according to the present invention;

FIG. 4 is a metallographic view of an ingot casting forging produced without the use of a modified shield welding electrode;

FIG. 5 is a metallographic picture of an ingot casting billet produced using a modified shield welding electrode.

Detailed Description

The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

The following two grades of ingots have specific smelting process parameters shown in table 1:

TABLE 1 melting Process parameters

Example 1

The embodiment relates to a method for preparing phi 440mm-1080Kg cast ingots by remelting TA1 residual materials:

carrying out acid and alkali cleaning, sand blasting, shot blasting and cleaning on alloy ingot casting risers, blank material heads, unqualified bars and the like of the same mark to obtain clean residual materials, stacking the clean residual materials in a fixed tool, welding the residual materials into consumable electrodes with the diameter of about 320mm by using a plasma arc welding mode under argon protection, and carrying out two-time smelting by using VAR according to the process parameters in the table 1 to obtain the 440-1080 Kg ingot casting, wherein the parameters specifically comprise that the arc starting voltage is 25V, the arc starting current is 4.5KA, the voltage in the smelting process is 28-29V, and the current in one-time smelting is 8 KA. The current of the secondary smelting is 13 KA.

Feeding when the residual 110Kg of the electrode at the last stage of secondary smelting is performed, wherein each time the KA is reduced by 0.6KA, the current is reduced to 6-8 KA in 20 minutes, and then the melting time is increased by 10min when the current is reduced each time; the feeding operation was completed for 105 minutes.

After remelting is finished, chemical components at the head, the middle and the tail of the ingot are detected, and the comparison result with the component range required in the national standard is shown in table 2, and the result shows that the ingot obtained by using the method meets the standard requirement and has more uniform components.

TABLE 2 comparison of New ingot composition with national Standard Range

As can be seen from the above table, the components of the ingot obtained by the invention can meet the requirements of national standards, even far better than the national standards, and can be directly reused.

Example 2

The TC4(Ti-6Al-4V) residue remelting method for preparing phi 520mm-1550Kg cast ingots: and (2) carrying out acid-base washing, sand blasting, shot blasting and cleaning on alloy ingot casting risers, blank stubs, unqualified bars and the like of the same mark to obtain clean residual materials, stacking the clean residual materials in a fixed tool, welding the residual materials into consumable electrodes with the diameter of about 320mm by using a plasma arc welding mode under argon protection, and carrying out three times of smelting according to the process parameters in the table 1 to obtain the ingots with the diameter of 520-1550 Kg. The arc starting voltage is 25V, the arc starting current is 4.5KA, the voltage in the smelting process is 28-29V, and the current in primary smelting is 7.5 KA. The current of the secondary smelting is 12 KA. The tertiary smelting current is 14 KA.

The feeding is specifically carried out when 110Kg of electrode remains at the end of three times of smelting, each time the KA is reduced by 0.8KA, the current is reduced to 6KA in 25 minutes, and then the melting time is increased by 10 minutes when the current is reduced each time; the feeding operation was completed for 155 minutes.

The comparison result of the chemical components at the head part, the middle part and the tail part of the ingot with the nominal components is shown in table 3, and the result shows that the ingot obtained by the method meets the standard requirements and has more uniform components.

TABLE 3 comparison of New ingot composition with national Standard Range

As can be seen from the above table, the components of the ingot obtained by the invention can meet the requirements of national standards, even far better than the national standards, and can be directly reused.

Comparative example 1

Compared with the embodiment, the method has the difference that an improved protective cover is not used in the welding process, the welding point is oxidized and blued, even white powdery substances appear on the welding point to cause severe oxidation, and oxides enter a molten pool after the electrode is smelted in a furnace, so that the risk of low-density inclusion of the cast ingot is increased. As shown in fig. 4 and 5 below. FIG. 4 is a phase diagram of an ingot casting forged blank produced without using the modified shield welding electrode, and FIG. 5 is a phase diagram of an ingot casting forged blank produced using the modified shield welding electrode.

Comparative example 2

Compared with the embodiment 1, the remelting process has different process parameters, specifically, the arc starting voltage is 25V, the arc starting current is 4.5KA, the voltage in the melting process is 28-29V, and the current in one-time melting is 6 KA. The current of the secondary smelting is 11 KA.

Feeding when the electrode is remained with 103Kg at the last stage of secondary smelting, wherein the feeding process parameters are different, the feeding is carried out when the electrode is remained with 0.6KA in each time, the current is reduced to 6-8 KA in 20 minutes, and then the melting time is increased by 10min when the current is reduced in each time; the feeding operation was completed for 108 minutes.

The comparison result of the chemical components at the head, the middle and the tail of the ingot with the nominal components is shown in table 4, and the result shows that the ingot components obtained by the process parameters meet the standard requirements but have poor component uniformity.

TABLE 4 comparison of New ingot composition with national Standard Range

Comparative example 3

Compared with the embodiment 1, the process parameters in the remelting process are different, specifically, the process parameters in the remelting process are that the arcing voltage is 25V, the arcing current is 4.5KA, the voltage in the smelting process is 28-29V, and the current in one-time smelting is 11 KA. The current of the secondary smelting is 16 KA.

Feeding when the electrode is left with 100Kg in the last stage of secondary smelting, wherein feeding process parameters are different, feeding is carried out when the electrode is left with 100Kg in the last stage of secondary smelting, the current is reduced to 6-8 KA in 20 minutes, and then the melting time is increased by 10min when the current is reduced; the feeding operation was completed for 110 minutes. The comparison result of the chemical components at the head, the middle and the tail of the ingot with the nominal components is shown in table 5, and the result shows that the ingot components obtained by the process parameters meet the standard requirements but have poor component uniformity.

TABLE 5 comparison of New ingot composition with national Standard Range

Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.