阅读说明：本技术 一种高碳当量特厚复合坯真空电子束组坯焊接工艺 (vacuum electron beam assembly welding process for high-carbon equivalent extra-thick composite blank ) 是由 马成 金百刚 刘文飞 李超 苏小利 韩旭 范刘群 王若钢 鲁强 于 2019-09-06 设计创作，主要内容包括：本发明涉及一种高碳当量特厚复合坯真空电子束组坯焊接工艺,高碳当量特厚复合坯的碳当量≥0.5％,成品钢板厚度为150～450mm；复合坯真空电子束组坯焊接工艺包括：1)复合坯料选择；2)复合坯料加工；3)复合坯预热；4)表面二次清理；5)保温及均匀化；6)复合坯焊接：7)焊后入炉加热；本发明针对高碳当量特厚复合坯焊接过程中易出现焊接微裂纹的技术难题,结合炼钢厂现场生产工艺流程,提供了一种高碳当量特厚复合坯真空电子束组坯焊接工艺,能够有效避免焊接微裂纹的产生,实现了高碳当量特厚复合板的低成本稳定生产。(The invention relates to a vacuum electron beam assembly welding process for a high-carbon-equivalent super-thick composite blank, wherein the carbon equivalent of the high-carbon-equivalent super-thick composite blank is more than or equal to 0.5 percent, and the thickness of a finished steel plate is 150-450 mm; the composite blank vacuum electron beam assembly welding process comprises the following steps: 1) selecting a composite blank; 2) processing a composite blank; 3) preheating the composite blank; 4) secondary cleaning of the surface; 5) preserving heat and homogenizing; 6) welding the composite blank: 7) heating in a furnace after welding; the invention provides a vacuum electron beam assembly welding process for a high-carbon equivalent extra-thick composite blank, which aims at the technical problem that welding microcracks are easy to appear in the welding process of the high-carbon equivalent extra-thick composite blank and combines with the field production process flow of a steel plant, can effectively avoid the generation of the welding microcracks, and realizes the low-cost stable production of the high-carbon equivalent extra-thick composite plate.)

1. A vacuum electron beam assembly welding process for a high-carbon-equivalent super-thick composite blank is characterized in that the carbon equivalent of the high-carbon-equivalent super-thick composite blank is more than or equal to 0.5%, and the thickness of a finished steel plate is 150-450 mm; the composite blank vacuum electron beam assembly welding process comprises the following steps:

1) selecting a composite blank: selecting continuous casting billets with length difference and width difference not greater than 10mm as blanks to be compounded, and stacking and slowly cooling the continuous casting billets after the continuous casting billets are offline, wherein the stacking temperature is greater than or equal to 500 ℃, and the stacking time is not less than 48 h;

2) Processing a composite blank: milling the surface to be compounded and four side surfaces of the continuous casting billet to remove an oxide layer and a corrosion layer, wherein the diagonal size deviation of the continuous casting billet after milling is less than or equal to 5mm, the plate surface flatness is less than or equal to 1mm/m, and the assembly gap is less than or equal to 0.5 mm; the surface roughness Ra is less than or equal to 12.5 mu m;

3) Preheating a composite blank: transporting the finished continuous casting blank assembly to a continuous casting blank stack just off line for baking and preheating, wherein the placing sequence from bottom to top is as follows: red blank-composite blank-red blank; baking for 2-4 hours, and ensuring the central temperature of the preheated plate blank to be 300-400 ℃;

4) Secondary cleaning of the surface; after the composite blank is preheated to reach the required temperature, respectively hoisting the continuous casting blanks forming the composite blank to a centering machine, carrying out secondary grinding on a composite surface and a side surface, and purging after grinding;

5) Preserving heat and homogenizing; covering asbestos on the surface of the continuous casting billet and preserving heat; assembling the blank again, observing a joint to be welded after assembling the blank, and setting slow cooling time according to the deformation degree of the joint to be welded, wherein the deformation of the joint to be welded is more than 2mm, and the slow cooling time is 2-3 hours; slowly cooling the to-be-welded joint for 1-2 hours, wherein the deformation of the to-be-welded joint is 1-2 mm; the deformation of the to-be-welded joint is less than or equal to 1mm, and slow cooling is not needed;

6) Welding the composite blank: performing vacuum electron beam spot welding operation on the composite blank; adopting a mode of firstly spot welding and then continuously welding; the welding current of the spot welding operation is 100-200 mA, and the welding speed is 8-12 mm/s; the continuous welding current is 300-500 mA, the welding speed is 5-8 mm/s, and the focusing current is 500-530 mA; welding in a symmetrical welding sequence;

7) putting the welded blank into a furnace for heating: and after welding, slowly cooling the composite blank in a vacuum chamber, taking out after stress is fully released, hoisting the composite blank to a chamber furnace, heating and rolling.

2. The vacuum electron beam assembly welding process for the high-carbon-equivalent extra-thick composite blank according to claim 1, characterized in that the depth of cut of the last milling process of the milling surface of the continuous casting blank in the step 1) is less than or equal to 2mm, and the milling speed is less than or equal to 100 mm/min.

3. the vacuum electron beam assembly welding process for the high-carbon-equivalent extra-thick composite blank according to claim 1, wherein the red blank positioned on the upper layer and the red blank positioned on the lower layer in the step 3) are all multiple.

Technical Field

the invention relates to the technical field of metal composite plate production, in particular to a vacuum electron beam assembly welding process for a high-carbon equivalent super-thick composite blank.

Background

the die steel has a very large quenching tendency, and the metallographic structure has high-carbon martensite and is very sensitive to the formation of cold cracks. Meanwhile, the martensite structure formed in the welding heat affected zone causes the metal material to have hard and brittle properties, and the plasticity and toughness of the joint are greatly reduced. Therefore, the die steel has extremely poor welding performance, and is likely to cause hot cracking and cold cracking during welding.

the vacuum composite rolling technology is a novel method for producing an extra-thick steel plate, compared with the traditional ingot casting, the method greatly improves the internal structure and performance of a rolled product, solves the problem of thickness limitation of the extra-thick steel plate due to the thickness limitation and the reduction ratio restriction of a continuous casting billet, is wide in rolled blank, is beneficial to mass production, and can greatly improve the yield.

at present, steel mills in China can manufacture high-quality ordinary low-carbon steel (such as Q235) and low-strength-grade alloy steel (such as Q345) super-thick steel plates by a vacuum composite rolling technology. However, in the process of producing the extra-thick steel plate with high carbon content and alloy content such as 1.2311 and the like by using the vacuum composite technology, due to the high crack sensitivity of the joint seam to be welded, the joint seam to be welded is easy to crack, even a base blank is easy to crack, subsequent rolling and compounding cannot be carried out, and finally the yield of the extra-thick plate with high carbon equivalent is extremely low.

Chinese patent publication No. CN102896466A discloses a method for producing 150-inch steel plates for 400mm thick plastic molds, which comprises using continuous casting slabs as raw materials, forming large-thickness blanks by gas shielded welding, submerged arc welding and vacuum electron beam combined welding process or full vacuum electron beam welding, and then heating, rolling, slowly cooling and heat treating, wherein the ultrasonic flaw detection qualification rate of the produced steel plates for plastic molds reaches more than 98%, the hardness distribution is uniform, and the steel plates have excellent processability, wear resistance and polishing property, and are suitable for manufacturing various plastic molds. However, the gas shielded welding process is very easy to generate surface oxidation, the welding effect is affected, the surface treatment is needed, and in addition, the groove processing is carried out on two or even a plurality of blanks, and the lifting, the alignment and the processing are very difficult for a single 10-20 ton steel blank. The method adopts a mode of combining three kinds of welding, has complex process and difficult operation, and accumulates welding stress, structural stress, thermal stress and the like which are larger and are easy to crack because of repeated welding on three sides of gas shielded welding, submerged arc welding and vacuum composite welding.

Chinese patent publication No. CN101590596A discloses a method for manufacturing extra-thick slabs by using an accumulative lap-rolling welding process, which is to lap continuous casting slabs of the same size made of the same material together, weld and seal gaps at the periphery under vacuum, and then perform the processes of heating, forging, rolling and the like to obtain extra-thick slabs with the thickness of up to 200 mm. But the process is complex, and the thickness specification can not meet the requirement of the ultra-thick steel plate.

chinese patent publication No. CN102240894A discloses a "composite manufacturing method of extra thick steel plate", which adopts a "high-temperature hydrogen reduction + hot rolling" method to produce extra thick steel plate, because the operation of the high-temperature hydrogen reduction process is complex, it has certain danger, reduces the operability of the process, and increases the manufacturing cost of the extra thick steel plate.

Chinese patent publication No. CN103692166A discloses "a method for producing a super-thick alloy steel sheet", which provides a method for producing a super-thick alloy steel sheet: two continuous alloy steel casting slabs with the length and the width matched with each other are subjected to surface treatment, then are subjected to assembly and welding to obtain an ultra-thick alloy steel plate blank, but two welding guns are required, and special assembly equipment is arranged, so that the development cost is increased. Chinese patent with publication number CN103028897A discloses a method for producing super-thick steel plates with high cold crack sensitivity, which also needs a double electron beam gun arrangement mode for preheating casting blanks to solve the problem of welding crack sensitivity of alloy steel.

Chinese patent publication No. CN 105252237a discloses "a method for producing a CrMnNiMo-series extra-thick die composite blank", which attempts to prevent welding cracks by fixing the composite blank by a symmetrical spot welding method, and cannot fundamentally solve the problem of welding cracks caused by internal stress and thermal stress of medium-carbon high-alloy die steel, and the actual effect is poor.

The welding of thick high-carbon equivalent steel is a technical subject to be overcome at home and abroad, and the technical problem of solving the vacuum hybrid welding rolling process is of great significance.

Disclosure of Invention

the invention provides a vacuum electron beam assembly welding process for a high-carbon equivalent extra-thick composite blank, which aims at the technical problem that welding microcracks are easy to appear in the welding process of the high-carbon equivalent extra-thick composite blank and combines with the field production process flow of a steel plant, can effectively avoid the generation of the welding microcracks, and realizes the low-cost stable production of the high-carbon equivalent extra-thick composite plate.

In order to achieve the purpose, the invention adopts the following technical scheme:

A vacuum electron beam assembly welding process for a high-carbon-equivalent super-thick composite blank is characterized in that the carbon equivalent of the high-carbon-equivalent super-thick composite blank is more than or equal to 0.5%, and the thickness of a finished steel plate is 150-450 mm; the composite blank vacuum electron beam assembly welding process comprises the following steps:

1) Selecting a composite blank; selecting continuous casting billets with length difference and width difference not greater than 10mm as blanks to be compounded, and stacking and slowly cooling the continuous casting billets after the continuous casting billets are offline, wherein the stacking temperature is greater than or equal to 500 ℃, and the stacking time is not less than 48 h;

2) Processing a composite blank; milling the surface to be compounded and four side surfaces of the continuous casting billet to remove an oxide layer and a corrosion layer, wherein the diagonal size deviation of the continuous casting billet after milling is less than or equal to 5mm, the plate surface flatness is less than or equal to 1mm/m, and the assembly gap is less than or equal to 0.5 mm; the surface roughness Ra is less than or equal to 12.5 mu m;

3) Preheating the composite blank; transporting the finished continuous casting blank assembly to a continuous casting blank stack just off line for baking and preheating, wherein the placing sequence from bottom to top is as follows: red blank-composite blank-red blank; baking for 2-4 hours, and ensuring the central temperature of the preheated plate blank to be 300-400 ℃;

4) Secondary cleaning of the surface; after the composite blank is preheated to reach the required temperature, respectively hoisting the continuous casting blanks forming the composite blank to a centering machine, carrying out secondary grinding on a composite surface and a side surface, and purging after grinding;

5) Preserving heat and homogenizing; covering asbestos on the surface of the continuous casting billet and preserving heat; assembling the blank again, observing a joint to be welded after assembling the blank, and setting slow cooling time according to the deformation degree of the joint to be welded, wherein the deformation of the joint to be welded is more than 2mm, and the slow cooling time is 2-3 hours; slowly cooling the to-be-welded joint for 1-2 hours, wherein the deformation of the to-be-welded joint is 1-2 mm; the deformation of the to-be-welded joint is less than or equal to 1mm, and slow cooling is not needed;

6) Welding the composite blank; performing vacuum electron beam spot welding operation on the composite blank; adopting a mode of firstly spot welding and then continuously welding; the welding current of the spot welding operation is 100-200 mA, and the welding speed is 8-12 mm/s; the continuous welding current is 300-500 mA, the welding speed is 5-8 mm/s, and the focusing current is 500-530 mA; welding in a symmetrical welding sequence;

7) Putting the welded blank into a furnace for heating: and after welding, slowly cooling the composite blank in a vacuum chamber, taking out after stress is fully released, hoisting the composite blank to a chamber furnace, heating and rolling.

the depth of cut of the last milling processing of the milling surface of the continuous casting blank in the step 1) is less than or equal to 2mm, and the milling speed is less than or equal to 100 mm/min.

The red blanks on the upper layer and the red blanks on the lower layer in the step 3) are all multiple.

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

1) The invention realizes the continuous and stable production of the high-carbon equivalent extra-thick composite plate blank; a series of problems of overlarge joint seam to be welded, cracking of welding meat in the welding process, expansion of the joint seam to be welded and the like are effectively controlled in the vacuum composite continuous welding process;

2) the process has strong operability and lower production cost, and realizes the composite production of the 150-mm extra-thick high-carbon equivalent steel plate by adopting the continuous casting billet on the premise of ensuring the yield, the flaw detection qualification rate and the performance qualification rate of the steel plate.

Detailed Description

According to the vacuum electron beam assembly welding process for the high-carbon-equivalent super-thick composite blank, the carbon equivalent of the high-carbon-equivalent super-thick composite blank is more than or equal to 0.5%, and the thickness of a finished steel plate is 150-450 mm; the vacuum electron beam assembly welding process for the high-carbon equivalent super-thick composite blank comprises the following steps of:

1) selecting a composite blank; selecting continuous casting billets with length difference and width difference not greater than 10mm as blanks to be compounded, and stacking and slowly cooling the continuous casting billets after the continuous casting billets are offline, wherein the stacking temperature is greater than or equal to 500 ℃, and the stacking time is not less than 48 h;

2) processing a composite blank; milling the surface to be compounded and four side surfaces of the continuous casting billet to remove an oxide layer and a corrosion layer, wherein the diagonal size deviation of the continuous casting billet after milling is less than or equal to 5mm, the plate surface flatness is less than or equal to 1mm/m, and the assembly gap is less than or equal to 0.5 mm; the surface roughness Ra is less than or equal to 12.5 mu m;

3) preheating the composite blank; transporting the finished continuous casting blank assembly to a continuous casting blank stack just off line for baking and preheating, wherein the placing sequence from bottom to top is as follows: red blank-composite blank-red blank; baking for 2-4 hours, and ensuring the central temperature of the preheated plate blank to be 300-400 ℃;

4) Secondary cleaning of the surface; after the composite blank is preheated to reach the required temperature, respectively hoisting the continuous casting blanks forming the composite blank to a centering machine, carrying out secondary grinding on a composite surface and a side surface, and purging after grinding;

5) preserving heat and homogenizing; covering asbestos on the surface of the continuous casting billet and preserving heat; assembling the blank again, observing a joint to be welded after assembling the blank, and setting slow cooling time according to the deformation degree of the joint to be welded, wherein the deformation of the joint to be welded is more than 2mm, and the slow cooling time is 2-3 hours; slowly cooling for 1h when the deformation of the joint seam to be welded is 1-2 mm; the deformation of the to-be-welded joint is less than or equal to 1mm, and slow cooling is not needed;

6) welding the composite blank; performing vacuum electron beam spot welding operation on the composite blank; adopting a mode of firstly spot welding and then continuously welding; the welding current of the spot welding operation is 100-200 mA, and the welding speed is 8-12 mm/s; the continuous welding current is 300-500 mA, the welding speed is 5-8 mm/s, and the focusing current is 500-530 mA; welding in a symmetrical welding sequence;

7) Putting the welded blank into a furnace for heating: and after welding, slowly cooling the composite blank in a vacuum chamber, taking out after stress is fully released, hoisting the composite blank to a chamber furnace, heating and rolling.

the depth of cut of the last milling processing of the milling surface of the continuous casting blank in the step 1) is less than or equal to 2mm, and the milling speed is less than or equal to 100 mm/min.

The red blanks on the upper layer and the red blanks on the lower layer in the step 3) are all multiple.

The following examples are carried out on the premise of the technical scheme of the invention, and detailed embodiments and specific operation processes are given, but the scope of the invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

[ example 1 ]

In this embodiment, the material of the high carbon equivalent extra thick composite blank is 1.2311, the size of the composite blank is 600mm (thickness) × 2000mm (width) × 4200mm (length), and the thickness of the finished product plate is 300 mm; the assembly welding process comprises the following steps:

1. Surface processing; the processing quality of the surface of the blank is strictly controlled, the depth of cut of the milling surface for the last milling processing is 2mm, the milling speed is 100mm/min, and the quality of the milled joint surface is effectively ensured.

2. Preheating a plate blank; conveying the combined composite blank into a continuous casting blank stack which is just off-line for baking and preheating, placing 4 red blanks on the lower part of the continuous casting blank stack, placing the composite blank, and pressing 4 red blanks on the upper part of the composite blank stack; baking for 3 hours, wherein the central temperature of the preheated plate blank is 350 ℃.

3. secondary cleaning of the surface; after the composite blank is preheated, the blank is lifted to a centering machine through a cross car, the composite surface and the side surface are polished for the second time, and the composite blank is swept after polishing, so that the surface is ensured to be free of oxides, oil stains, dust and the like.

4. Preserving heat and homogenizing; covering asbestos on the surface of the continuous casting billet and preserving heat; assembling the blank again, observing a joint to be welded after assembling the blank, and setting slow cooling time according to the deformation degree of the joint to be welded, wherein the deformation of the joint to be welded is more than 2mm, and the slow cooling time is 2-3 hours; slowly cooling for 1h when the deformation of the joint seam to be welded is 1-2 mm; the deformation of the joint seam to be welded is less than or equal to 1mm, and slow cooling is not needed.

5. welding the composite blank; and carrying out vacuum electron beam spot welding operation on the composite blank. The mode of spot welding and continuous welding is adopted, the welding current of spot welding operation is 150mA, and the welding speed is 8 mm/s. The continuous welding current is 500mA, the welding speed is 5mm/s, and the focusing current is 530 mA. Welding in a symmetrical welding sequence.

6. Putting the welded blank into a furnace for heating: and after welding, slowly cooling the composite blank in a vacuum chamber, taking out after stress is fully released, hoisting the composite blank to a chamber furnace, heating the composite blank, and rolling the composite blank to the thickness of 300mm of a finished product.

[ example 2 ]

In this embodiment, the material of the high carbon equivalent extra thick composite blank is AGMJ 50: the thickness of the composite blank is 600mm multiplied by 2200mm multiplied by 3800mm, and the thickness of the finished plate is 350 mm. The assembly welding process comprises the following steps:

1. surface processing; the depth of cut of the milling surface for the last milling processing is 1mm, and the milling speed is 70 mm/min.

2. Preheating a plate blank; conveying the combined composite blank into a continuous casting blank stack which is just off-line for baking and preheating, placing 4 red blanks on the lower part of the continuous casting blank stack, then placing the composite blank, and pressing 3 red blanks on the upper part of the composite blank stack; baking for 4 hours, wherein the central temperature of the preheated composite blank is 320 ℃.

3. secondary cleaning of the surface; after the composite blank is preheated, the continuous casting materials forming the composite blank are respectively hoisted to a centering machine through a cross car, the composite surface and the side surface are secondarily polished, and the composite blank is swept after polishing, so that the surface is ensured to be free of oxides, oil stains, dust and the like.

4. preserving heat and homogenizing; covering asbestos on the surface of the continuous casting billet and preserving heat; assembling the blank again, observing a joint to be welded after assembling the blank, and setting slow cooling time according to the deformation degree of the joint to be welded, wherein the deformation of the joint to be welded is more than 2mm, and the slow cooling time is 2-3 hours; slowly cooling for 1h when the deformation of the joint seam to be welded is 1-2 mm; the deformation of the joint seam to be welded is less than or equal to 1mm, and slow cooling is not needed.

5. Welding the composite blank; the welding current of spot welding is 150mA, and the welding speed is 10 mm/s. 5 narrow side points, 6 wide side points, spot welding sequence, symmetrical welding, welding current of 350mA for continuous welding, welding speed of 6mm/s and focusing current of 520 mA. And (4) welding sequence, and symmetrically welding.

6. Heating in a furnace after welding; and after welding, slowly cooling the composite blank in a vacuum chamber, taking out after stress is fully released, hoisting the composite blank to a chamber furnace, heating the composite blank, and rolling the composite blank to the thickness of 400mm of a finished product.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.