Manufacturing method of duplex stainless steel and carbon steel asymmetrically rolled composite plate

Abstract

The invention relates to a manufacturing method of a duplex stainless steel and carbon steel asymmetrically rolled composite plate. Stainless steel is any one of duplex stainless steel. The medium carbon steel is any one of plain carbon steel, low-carbon steel and alloy steel. The manufacturing method of the asymmetric composite blank of the duplex stainless steel and the carbon steel comprises the following steps: 1, preparing raw materials for assembling the blank; 2, pretreating the stainless steel middle plate; and 3, surface treatment of the assembly raw material. And 4, cleaning. And 5, assembling. And 6, vacuum chamber electron beam seal welding. And 7, composite blank welding seam detection. And 8, heating the composite blank. And 9, rolling the composite plate. And 10, laminar cooling. And 11, the composite blank has no cracking phenomenon in the heating and rolling processes, the interface shear strength tau after hot rolling is larger than or equal to 280 MPa, the interface bonding rate is 100%, the bonding performance is good, and the proportion of dual-phase steel ferrite is 40-60%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite plate manufacturing, in particular to a manufacturing method of duplex stainless steel and carbon steel asymmetric rolling composite plate. BACKGROUND

[0002] Stainless steel + carbon steel composite plate is a layered composite material combined by carbon steel base layer and stainless steel composite layer through specific process (such as explosion composite, rolling composite or surfacing composite). It has both properties, can meet higher strength, has excellent corrosion resistance and wear resistance, greatly reduces the use amount of stainless steel, saves the use amount of precious metals such as chromium and nickel, is a new type of material with higher cost performance, higher efficiency, low carbon and environmental protection, and has wide application prospect.

[0003] Composite production technology includes mechanical composite, explosion composite and rolling composite and other process approaches. Among them, explosion and rolling composite can directly produce composite steel plate, or further produce thinner hot-rolled and cold-rolled composite steel plate / coil. Explosion composite technology is relatively backward, sensitive to environmental factors, and relatively difficult to produce ≤8mm thick steel plate. The rolling composite materials at home and abroad are mostly hot-rolled steel plates, but they have the common shortcomings of low production efficiency and low yield, and generally use ABA or AB+isolating agent+BA symmetric blanking mode for production. But the yield is low, and the single weight is small. And the realization of (A+B) type asymmetric blanking rolling composite steel plate is the research focus in recent two years.

[0004] Due to the difference in material properties, asymmetric metal composite rolling will cause rolling difficulty. Rolling composite involves full-process preparation technology, from welding blanking to asymmetric heating rolling. Not only is the quality of the weld seam required to be high, but the rolling requirement is also very high. Therefore, a full-process manufacturing method of duplex stainless steel and carbon steel asymmetric composite blank blanking and heating rolling is proposed, which realizes the asymmetric blanking of stainless steel and carbon steel, the composite blank does not crack during the heating rolling process, and the composite plate with excellent performance is obtained.

[0005] The stainless steel composite plate product market has broad prospects, high technical requirements, and high requirements for the integrated system control of the process and equipment of the production line.

[0006] The present application is a manufacturing method of duplex stainless steel and carbon steel asymmetric rolling composite plate, and the purpose is also to provide a duplex stainless steel and carbon steel asymmetric composite blank and composite plate, and the bonding performance and corrosion resistance of the produced composite plate are excellent. SUMMARY

[0007] The purpose of the present application is to provide a manufacturing method of duplex stainless steel and carbon steel asymmetric rolling composite plate.

[0008] The application aims to achieve the following: a manufacturing method of duplex stainless steel and carbon steel asymmetric rolling composite plate, comprising the following steps: step one: blank preparation: carbon steel is continuously cast into a casting blank after converter smelting and secondary refining, the thickness of the carbon steel casting blank is 200-280 mm, the carbon steel casting blank is stored for stack cooling for not less than 3 days after being discharged, 1 carbon steel casting blank is placed at the bottom, the carbon steel casting blank for composite blank is placed in the middle of the stack, and 2 carbon steel casting blanks are placed at the top, so as to ensure that the unevenness of the carbon steel casting blank for composite blank is less than or equal to 5 mm; the material for the base layer of the composite plate is rolled into a stainless steel medium plate, the thickness of the stainless steel medium plate is 10-67 mm, the material for the composite layer of the composite plate, and the thickness ratio of the base layer and the composite layer is (3-28):1; step two: stainless steel medium plate pretreatment: the stainless steel medium plate for the composite layer of the composite plate is first subjected to solid solution treatment, the solid solution treatment temperature is controlled at 950-1100 DEG C, the holding time is controlled at 1.5 min / mm, and the stainless steel medium plate is water-cooled to room temperature; then the stainless steel medium plate after solid solution treatment is subjected to pickling, the surface oxide scale of the stainless steel medium plate is removed clean, and passivation treatment is performed; after pickling, straightening treatment is performed, so that the unevenness of the stainless steel medium plate is less than or equal to 7 mm; step three: surface treatment of blank preparation material: ①the composite surface of the carbon steel casting blank is subjected to single-sided milling to remove surface iron oxide scale, cracks and slag, and to process a metallic color; ②the composite surface of the stainless steel medium plate is subjected to 80-mesh automatic grinding by a thousand-blade wheel grinder to remove the passivation layer and process a metallic color; ③the composite surface of the carbon steel casting blank after milling and the composite surface of the stainless steel medium plate after automatic grinding are both subjected to manual grinding by a grinding wheel machine, a 100-120-mesh grinding wheel sheet is used, and the roughness of the surface treatment reaches Ra2.0-4.0 μm; step four: cleaning: the composite surface is first blown by compressed air without water vapor to blow away surface dust or iron dust, and then the dust particles that cannot be blown away are cleaned by acetone or volatile alkaline cleaning agent; the cleaning time is required to be 3-5 min / m 2 ; step five: blank preparation: the carbon steel casting blank is first placed at the bottom with the ground surface upward, the stainless steel medium plate is turned over with the ground surface downward, the stainless steel medium plate is hoisted and aligned with the carbon steel casting blank at the bottom, the stainless steel medium plate is pressed by a flattening machine to ensure that the combined gap between the composite surfaces is less than or equal to 1 mm, and the four edges are spot-welded with a spot-welding length of 40-60 mm and a spot-welding interval distance of 300-500 mm, so that the blank becomes a composite blank, and the composite blank is sent into a vacuum chamber with the carbon steel casting blank on top; step six: vacuum chamber electron beam sealing: ①the vacuum chamber is evacuated to a vacuum degree of less than or equal to 7.5 x 10 -2Pa; ② the composite blank is spot-welded again at four edges with a distance of 200-300mm; ③ the position of the electron beam gun: the stainless steel middle plate is directly welded with the carbon steel cast blank in the assembling mode, and the electron beam gun is directly opposite the middle position of the weld; ④ the welding sequence is to weld the two long edges first, and then weld the two short edges; ⑤ the sealing welding process adopts a welding beam current of 140-200mA, a welding voltage of 65-75KV, and a welding speed of 100-150mm / min; step seven: the weld of the composite blank is detected: the carbon steel cast blank on the upper part is removed after the sealing welding is completed, and the weld is detected by ultrasonic detection to ensure that there is no crack and pore, and the penetration depth is 35-50mm; step eight: the composite blank is heated: a carbon steel pad blank is placed at the lowermost part before the composite blank is heated in the ingot furnace, the composite blank is placed on the pad blank with the stainless steel facing downward, the length and width of the pad blank are not less than those of the composite blank, the composite blank is ensured to be placed at the middle part of the pad blank and pressed at four edges to inhibit the deformation of the weld; secondly, a two-stage heating process is adopted in the ingot furnace, the furnace is loaded when the temperature is 500-600℃, the first stage has a temperature rising speed of 70-90℃ / h, the temperature is raised to 1000-1100℃ and kept for 4-6h, the second stage has a temperature rising speed of 50-70℃ / h, the temperature is raised to 1200-1230℃ and kept for 4-6h; step nine: the composite plate is rolled: two-stage rolling is adopted, the first stage has a rolling temperature of 1000-1080℃, the second stage has a rolling temperature of ≤930℃, the intermediate thickness is 2-4 times the thickness of the finished product, and the final rolling temperature is controlled to be 830±20℃; step ten: laminar cooling: ACC laminar cooling is adopted, the water inlet temperature is controlled to be 780±20℃, and the final cooling temperature is controlled to be 600±20℃.

[0009] The concentration of the acid pickling in step two is HNO3: 120-300g / L, and HF: 15-50g / L, and the acid pickling speed is 2-8m / min.

[0010] The beneficial effects of the present application are: the present application provides a manufacturing method of the duplex stainless steel and carbon steel asymmetric rolling composite plate according to the characteristics that the duplex stainless steel and carbon steel are difficult to assemble and heat and roll, the method has low cost, improves the success rate of assembly and rolling, and can obtain the duplex stainless steel and carbon steel asymmetric rolling composite plate with excellent quality. BRIEF DESCRIPTION OF DRAWINGS

[0011] The present application will be further described below with reference to the drawings.

[0012] Figure 1 It is the heating mode diagram of the composite blank ingot furnace of the present application. 1 is the base layer carbon steel of the composite blank, 2 is the composite layer stainless steel of the composite blank, and 3 is the carbon steel pad blank. DETAILED DESCRIPTION

[0013] The application is a manufacturing method of duplex stainless steel and carbon steel asymmetric rolling composite plate, the stainless steel is any one of duplex stainless steel, and the carbon steel is any one of plain carbon steel, low carbon steel and alloy steel. The method comprises the following steps: blank preparation, stainless steel plate pretreatment, blank surface treatment, cleaning, blank assembly, vacuum chamber electron beam sealing, composite blank weld detection, composite blank heating, composite plate rolling and laminar cooling.

[0014] The stainless steel used for the composite plate is any one of duplex stainless steel, and the thickness of the stainless steel plate is 10-67 mm; the carbon steel used for the base layer of the composite plate is any one of plain carbon steel, low carbon steel and alloy steel, and the thickness of the carbon steel casting blank is 200-280 mm, and the unevenness of the carbon steel casting blank used for composite blank preparation is ≤5 mm. The thickness ratio of the base layer and the composite layer is (3-28):1.

[0015] The stainless steel plate used for the composite plate is subjected to solid solution treatment, the solid solution treatment temperature is controlled at 950-1100℃, the holding time is controlled at 1.5 min / mm, and the stainless steel plate is water-cooled to room temperature. The stainless steel plate after solid solution treatment is subjected to straightening treatment, and the unevenness of the stainless steel plate is ≤7 mm.

[0016] The stainless steel plate is subjected to automatic grinding with an 80-mesh diamond wheel, instead of milling process, so that the processing efficiency is greatly improved, and the surface roughness Ra is 4.0-6.0 μm.

[0017] The carbon steel surface to be compounded after manual grinding and milling and the surface of the stainless steel plate after automatic grinding are subjected to grinding, and the surface roughness Ra of the carbon steel casting blank and the stainless steel plate after surface treatment is 2.0-4.0 μm.

[0018] The carbon steel casting blank is placed at the lower layer with the ground surface upward, and the stainless steel plate is placed at the upper layer with the ground surface downward, after the blank assembly, the combined gap between the composite surfaces is ≤1 mm.

[0019] The sealing vacuum degree is ≤7.5×10-2 Pa, the composite blank is spot-welded at four edges with a distance of 200-300 mm, and the electron beam gun is directly opposite to the middle position of the weld. The welding sequence is to weld the two long edges first, and then weld the two short edges. The welding beam current is 140-200 mA, the welding voltage is 65-75 KV, and the welding speed is 100-150 mm / min.

[0020] The composite blank is loaded into the steel ingot furnace at 500℃, a carbon steel blank is placed at the lowermost position, the composite blank is placed on the blank, the stainless steel surface faces downward, the size of the blank is not less than that of the composite blank, and the composite blank is placed at the middle position of the blank and pressed at four edges. A two-stage heating process is adopted in the steel ingot furnace, the first stage is to heat at a speed of 70-90℃ / h to 1050℃ and keep for 4 h, and the second stage is to heat at a speed of 50-70℃ / h to 1200-1230℃ and keep for 4 h.

[0021] The differential rolling is adopted in the whole rolling process of the clad plate, and the rolling speed of the stainless steel surface is 10-15% faster than that of the carbon steel surface. The controlled rolling adopts two-stage rolling, the first-stage rolling temperature is 1000-1080 DEG C, the second-stage rolling temperature is less than or equal to 930 DEG C, the intermediate thickness is 2-4 times of the thickness of the finished product, and the final rolling temperature is controlled to be 830 DEG C ± 20 DEG C.

[0022] The ACC laminar cooling is adopted, the water inlet temperature is 780 DEG C ± 20 DEG C, and the final cooling temperature is controlled to be 600 DEG C ± 20 DEG C, in order to quickly pass through the harmful phase precipitation interval.

[0023] The melting depth of the clad blank is greater than or equal to 35 mm. The asymmetric clad blank of the duplex stainless steel and the carbon steel is obtained through hot rolling. The interface shear strength of the stainless steel and the carbon steel clad plate is greater than or equal to 280 MPa, the interface bonding rate is 100%, the bonding performance is good, and the ferrite phase of the stainless steel complex layer meets the proportion requirement of 40-60%.

[0024] The technical scheme adopted in the present application is: 1, blank preparation. The carbon steel is smelted by converter and refined outside the furnace (LF), and then is continuously cast into a cast blank. The thickness of the carbon steel cast blank is 200-280 mm. After the cast blank is discharged, it is stacked and stored for at least 3 days of stack cooling. One cast blank is placed at the bottom, the carbon steel cast blank for composite blanking is placed in the middle of the stack, and two cast blanks are placed at the top to ensure that the unevenness of the carbon steel cast blank for composite blanking is less than or equal to 5 mm, which is used as the base material for the clad plate. The stainless steel cast blank (blank thickness 200 mm) is rolled into a stainless steel medium plate, and the thickness of the stainless steel medium plate is 10-67 mm, which is used as the complex layer material for the clad plate. The thickness ratio of the base layer and the complex layer is (3-28):1.

[0025] 2, stainless steel medium plate pretreatment. First, the stainless steel medium plate used as the complex layer material for the clad plate is subjected to solid solution treatment, the solid solution treatment temperature is controlled to be 950-1100 DEG C, the holding time is controlled according to 1.5 min / mm, and water cooling is performed to room temperature. Reasonable solid solution process can make the duplex stainless steel organization soften uniformly, improve the internal stress, reduce the welding deformation degree of the duplex stainless steel, effectively reduce the cracking rate in the subsequent heating and rolling process, and enhance the composite effect. Then, the solid-solution-treated stainless steel medium plate is subjected to pickling and straightening treatment, so that the unevenness of the stainless steel medium plate is less than or equal to 7 mm.

[0026] 3. Surface treatment of the billet. ① The surface of the carbon steel billet to be compounded is milled to remove surface scale, cracks, slag and other defects, and to produce a metallic color. ② The surface of the stainless steel to be compounded is polished by an 80-mesh automatic polishing machine to remove the passivation layer and produce a metallic color. This process replaces the stainless steel milling process and greatly improves the processing efficiency. ③ The surfaces of the carbon steel billet after milling and the stainless steel plate after automatic polishing are polished by a manual grinder using 100-120 mesh abrasive wheels. The roughness of the treated surface is Ra 2.0-4.0 μm, which can effectively remove the surface scale and form a hardened layer. The hard and brittle hardened layer is beneficial to realize rolling compounding and improve the interface bonding strength of the clad plate.

[0027] 4. Cleaning. First, the surface is blown off with compressed air to remove floating dust or iron dust. Then, the surface is cleaned with acetone or volatile alkaline cleaning agent to remove dust particles that cannot be blown away.

[0028] 5. Assembling the billet. First, the carbon steel billet is placed on the lower layer with the polished surface facing up. Then, the stainless steel plate is turned over so that the polished surface of the stainless steel faces down. The stainless steel is hoisted and slowly aligned with the lower layer billet. The stainless steel is pressed by a pressing machine to ensure that the gap between the compounded surfaces is ≤1 mm. The four edges are spot welded with a length of 40-60 mm and a spacing distance of 300-500 mm. After assembling the billet, the carbon steel billet is pressed and sent into the vacuum chamber.

[0029] 6. Vacuum chamber electron beam sealing. ① The vacuum chamber is evacuated to a vacuum degree of ≤7.5 x 10 -2Pa. With the increase of vacuum, the composite effect is enhanced, more conducive to the slab composite. ② The composite slab is spot welded on four sides with a spacing distance of 200-300mm. ③ The position of the electron beam gun. The group of blanks is directly welded between stainless steel and carbon steel. When welding dissimilar metals, the thermoelectric effect may generate a magnetic field, causing the electron beam to deviate to the side with strong magnetic field, resulting in welding deviation problem. Since duplex stainless steel exhibits weak magnetism, and it has been demonstrated through testing that no offset compensation is needed during the sealing process. Therefore, the electron beam gun should be directly opposite the center of the weld, so that the fusion position of the weld is located in the middle of the weld, which can effectively ensure the strength of the weld. ④ The welding sequence is to weld the two long sides first, and then weld the two short sides, which can effectively reduce the stress concentration at the sealing joint and improve the reliability of the sealing joint. In addition, the spot welding of the stainless steel medium plate and the standby carbon steel casting blank can effectively reduce the degree of welding deformation of the stainless steel and reduce the generation of micro-cracks in the weld. Under the action of the two, not only can the welding efficiency be improved, but also the vacuum effectiveness of the bonding surface can be maintained during the subsequent heating and rolling process of the composite blank, and the composite effect is enhanced. ⑤ Since the composite layer is duplex stainless steel, duplex stainless steel is sensitive to heat input. When the heat input is too large, the grains in the welding heat affected zone are easy to grow, which causes the plastic toughness of the welding heat affected zone to decrease. Therefore, the sealing process needs to be controlled specifically to ensure the depth of the weld while enhancing the strength of the weld. The sealing process adopts a welding beam current of 140-200mA. When the beam current is small, the heat input is too low, resulting in incomplete penetration. When the beam current is too large, the plastic toughness of the welding heat affected zone will decrease due to excessive heat input. The welding voltage is 65-75KV. Too small voltage will result in insufficient weld penetration, and too large voltage will cause the weld to be too wide. The welding speed is 100-150mm / min. Too fast welding speed will result in incomplete penetration, and too slow welding speed will cause weld depression.

[0030] 7. Weld seam detection of the composite blank. After the sealing of the composite blank, the upper carbon steel casting blank is removed, and the weld is inspected for cracks, pores and other defects by ultrasonic testing to ensure that the penetration is ≥35mm.

[0031] 8、Composite blank heating. The weld is sensitive to heating, and if the heating speed is too fast, the thermal expansion coefficient difference is large due to the difference in material between the upper and lower materials, especially the large thermal deformation difference between the bi-directional stainless steel and the carbon steel, which is easy to cause large stress at the weld, and even weld cracking. Therefore, before heating in the ingot furnace, a carbon steel pad blank is placed at the bottom, the composite blank is placed on the pad blank, the stainless steel face is downward, the pad blank size is not less than the composite blank, and the composite blank is placed in the middle of the pad blank, and the four sides are pressed to suppress the deformation of the weld. Secondly, two-stage heating process is adopted in the ingot furnace, the furnace temperature is 500℃, the first stage heating speed is 70-90℃ / h, the temperature is raised to 1050℃ and kept for 4h, the second stage heating speed is 50-70℃ / h, the temperature is raised to 1200-1230℃ and kept for 4h, so as to slow down the stress on the weld and reduce the cracking rate of the weld.

[0032] 9、Composite plate rolling. Due to the inconsistent deformation of duplex steel and carbon steel, differential rolling is adopted throughout the rolling of the composite plate, and the rolling speed of the stainless steel surface is 10-15% faster than that of the carbon steel surface. And in order to obtain ideal organization performance, two-stage rolling is adopted, the first stage rolling temperature is 1000-1080℃, the second stage rolling temperature is ≤930℃, the intermediate thickness is 2-4 times the finished product thickness, and the final rolling temperature is controlled at 830±20℃.

[0033] 10、Laminar cooling. ACC laminar cooling is adopted, the water inlet temperature is controlled at 780±20℃, and in order to quickly pass through the harmful phase precipitation zone of bi-directional stainless steel, the final cooling temperature is controlled at 600±20℃.

[0034] 11、The composite plate obtained by the above manufacturing method has a rolling success rate of more than 95%, the interface shear strength τ is ≥280MPa, the interface bonding rate is 100%, the bonding performance is good, and the ferrite phase proportion of duplex stainless steel is 40-60%.

[0035] The manufacturing method of the duplex stainless steel and carbon steel asymmetric rolling composite plate has the characteristics that, in the step 1 of the preparation of the blank raw material, the piling and cooling process of the carbon steel casting blank can ensure the unevenness of the casting blank, which is beneficial to the subsequent welding of the blank; in the step 2 of the pretreatment of the stainless steel middle plate, the reasonable solid solution process can make the duplex stainless steel organization soften uniformly, improve the internal stress, reduce the welding deformation degree of the duplex stainless steel, effectively reduce the cracking rate in the subsequent heating and rolling process, and enhance the composite effect; in the step 3 of the surface treatment of the blank raw material, the stainless steel middle plate is ground by using an automatic grinding machine, instead of the traditional milling process, so that the processing efficiency is improved, the plate shape deformation of the stainless steel in the milling process is effectively inhibited, the surface processing is uniform and fast, the requirements of the blank are met, the reasonable surface treatment process can effectively remove the surface iron oxide scale and form a surface hardening layer, and the hard and brittle hardening layer is beneficial to the realization of the rolling composite and the improvement of the interface bonding strength of the composite plate; in the step 6 of the vacuum electron beam sealing welding, the reasonable welding sequence can effectively reduce the stress concentration at the sealing joint and improve the reliability of the sealing joint; the spot welding combination of the stainless steel middle plate and the carbon steel casting blank and the upper pressing of the standby casting blank can effectively reduce the welding deformation degree of the stainless steel and reduce the generation of the welding micro-cracks; the reduction of the stress concentration and the welding deformation degree not only can improve the welding efficiency, but also can make the composite blank maintain the vacuum effectiveness of the bonding surface in the subsequent heating and rolling process, and enhance the composite effect; the reasonable sealing process not only is simple in operation, but also has high welding efficiency, and can effectively ensure the quality of the composite blank sealing; in the step 8 of the heating of the composite blank, the reasonable furnace charging mode and the reasonable heating process can effectively reduce the stress concentration and the heating cracking rate of the welding seam; in the step 9 of the rolling of the composite plate, the reasonable rolling process can obtain the composite plate with excellent plate shape, and can prevent the welding seam from cracking due to the inconsistent deformation of the upper and lower surfaces; the reasonable controlled rolling temperature and the intermediate thickness can obtain good performance and organization; in the step 10 of the laminar cooling, the reasonable cooling speed and the final cooling temperature can prevent the precipitation of the harmful phase of the duplex steel and ensure the corrosion resistance of the stainless steel surface.

[0036] The duplex stainless steel and carbon steel asymmetric rolling composite plate is obtained through the processes of the preparation of the blank raw material, the pretreatment of the stainless steel middle plate, the surface treatment of the blank raw material, cleaning, blanking, vacuum chamber electron beam sealing welding, composite blank welding seam detection, composite blank heating, composite plate rolling and laminar cooling.

[0037] The specific embodiments of the present application will be described in detail below in combination with the examples, but the specific embodiments of the present application are not limited to the following examples. Example 1

[0038] The stainless steel used in the example is duplex stainless steel S22053, and the carbon steel used is Q235B. The thickness of the stainless steel composite layer is 5 mm, and the thickness of the carbon steel base layer is 20 mm.

[0039] 1. Preparation of the blank. Carbon steel is smelted in a converter and refined outside the furnace (LF) and then cast into a slab. The thickness of the carbon steel slab is 230 mm. The slab is stored and cooled by stacking after being discharged from the continuous casting machine. One slab is placed at the bottom, the carbon steel slab for the composite blank is placed in the middle of the stack, and three slabs are placed at the top. The unevenness of the carbon steel slab for the composite blank is 5 mm and is used as the base layer of the clad plate. The stainless steel slab (200 mm thick) is rolled into a stainless steel medium plate, which is used as the clad layer of the clad plate. The thickness ratio of the base layer to the clad layer is 4:1.

[0040] 2. Pretreatment of the stainless steel medium plate. The stainless steel medium plate for the clad layer is first subjected to solid solution treatment at a temperature of 1040-1100°C for 1.5 min / mm and then water-cooled to room temperature. The stainless steel medium plate is then straightened to make the unevenness of the stainless steel medium plate 7 mm.

[0041] 3. Surface treatment of the blank. ① The surface of the carbon steel slab to be combined is milled to remove surface scale, cracks, slag and other defects and to process the metal color. ② The surface of the stainless steel medium plate to be combined is polished to remove the passivation layer and to process the metal color. ③ The surfaces of the carbon steel slab and the stainless steel medium plate to be combined are polished by a hand grinder using a 100 mesh grinding wheel. The roughness of the carbon steel surface after treatment is Ra 3.8 μm, and the roughness of the stainless steel surface after treatment is Ra 4.0 μm.

[0042] 4. Cleaning. The surface is first blown with compressed air containing no moisture to blow away floating dust or iron dust. Then, the surface is cleaned with acetone or volatile alkaline cleaning agent to remove dust particles that cannot be blown away.

[0043] 5. Assembly of the blank. The carbon steel slab is placed on the bottom with the polished surface facing up. The stainless steel medium plate is placed on top with the polished surface facing down. The two slabs are slowly aligned with a gap of 0.9 mm between the combined surfaces. After assembly, the slabs are lifted and sent into the vacuum chamber.

[0044] 6. Electron beam sealing in the vacuum chamber. ① The vacuum chamber is evacuated to a vacuum degree of 6.5 x 10 -2 Pa. ② The four edges of the combined slab are spot-welded with a distance of 200 mm. ③ The electron beam gun is directed at the center of the weld. ④ The welding sequence is to weld the two long edges first and then the two short edges. ⑤ The welding beam current is 185 mA, the welding voltage is 70 KV, and the welding speed is 120 mm / min.

[0045] 7. Inspection of the weld of the combined slab. After sealing, the spare carbon steel slab and the stainless steel plate are separated and removed at the spot-welding position. The weld is then inspected by ultrasonic testing to check for cracks, pores and other defects. The penetration depth is 45 mm.

[0046] 8. Heating of the composite blank. The composite blank is heated at a first stage heating rate of 80°C / h to 1050°C for 4 hours, and at a second stage heating rate of 70°C / h to 1230°C for 4 hours.

[0047] 9. Rolling of the composite blank. The composite blank is rolled at a differential speed of 15% throughout the rolling process, at a first stage rolling temperature of 1050°C, at a second stage rolling temperature of 925°C, at an intermediate thickness of 75 mm, and at a final rolling temperature of 830°C.

[0048] 10. Laminar cooling. The entry water temperature is 780°C, and the final cooling temperature is 600°C.

[0049] 11. No cracking occurs during the heating and rolling of the composite blank. The interfacial shear strength of the hot-rolled composite blank is 305 MPa, the interfacial bonding rate is 100%, the bonding performance is good, and the ferrite phase proportion of the dual-phase steel is 52%. Example Two

[0050] The stainless steel used in this example is dual-phase stainless steel S25073, and the carbon steel used is Q355B. The thickness of the stainless steel composite layer of the rolled product is 1 mm, and the thickness of the carbon steel base layer is 28 mm.

[0051] 1. Preparation of the blank. The carbon steel is smelted in a converter and refined outside the furnace (LF), and then continuously cast into a cast blank. The thickness of the carbon steel cast blank is 280 mm. After the cast blank is discharged, it is stacked and stored for stack cooling. One cast blank is placed on the bottom layer, the carbon steel cast blank for composite blank preparation is placed in the middle of the stack, and three cast blanks are placed on the top layer. The unevenness of the carbon steel cast blank for composite blank preparation is 3 mm, which is used as the base layer material for the composite plate. The stainless steel cast blank (blank thickness 200 mm) is rolled into a stainless steel medium plate, and the thickness of the stainless steel medium plate is 10 mm, which is used as the composite layer material for the composite plate. The thickness ratio of the base layer to the composite layer is 28:1.

[0052] 2. Pretreatment of the stainless steel medium plate. First, the stainless steel medium plate used as the composite layer material for the composite plate is subjected to solid solution treatment at a temperature of 1050-1100°C for a holding time of 1.5 min / mm, and then water-cooled to room temperature. Then, the solid-solution-treated stainless steel medium plate is subjected to straightening treatment to make the unevenness of the stainless steel medium plate 6 mm.

[0053] 3. Surface treatment of the blank. ① The surface of the carbon steel cast blank to be compounded is milled to remove surface defects such as iron oxide scale, cracks, and slag, and to process a metallic color. ② The surface of the stainless steel to be compounded is ground using an automatic grinding machine to remove the passivation layer and process a metallic color. ③ The surfaces of the carbon steel cast blank and the stainless steel medium plate to be compounded after milling are ground using a manual grinding machine, and a 120-mesh grinding wheel is used. The roughness of the carbon steel surface after treatment is Ra 3.2 μm, and the roughness of the stainless steel surface after treatment is Ra 3.6 μm.

[0054] 4. Cleaning. First, use compressed air without moisture to blow away the surface dust or iron dust; then use acetone or a volatile alkaline cleaning agent to clean the dust particles that cannot be blown away.

[0055] 5. Billet Assembly. First, place the carbon steel billet on the lower layer with the ground surface facing up. Then, flip the stainless steel middle plate along with the spare carbon steel billet so that the ground stainless steel surface faces down. Hoist it and slowly align it with the lower layer billet, with a 1.0mm gap between the composite surfaces. After assembly, the upper pressure billet is sent into the vacuum chamber.

[0056] 6. Electron beam sealing in the vacuum chamber. ① Evacuate the vacuum chamber to a vacuum level of 7.5 × 10⁻⁶. -2 Pa. ② Spot weld the four sides of the composite blank at intervals of 240mm. ③ Position the electron beam gun directly at the center of the weld. ④ Weld the two long sides first, then the two short sides. ⑤ Use a welding beam current of 160mA, a welding voltage of 65KV, and a welding speed of 120mm / min.

[0057] 7. Inspection of composite billet welds. After the composite billet is sealed, the spare carbon steel casting billet and stainless steel are separated and removed at the spot welding position. Then, the weld is inspected by ultrasonic testing to ensure there are no defects such as cracks or porosity, and the penetration depth is 35mm.

[0058] 8. Heating of composite billets. The composite billets are heated in the ingot furnace at a rate of 90℃ / h in the first stage, and held at 1050℃ for 4 hours. In the second stage, the heating rate is 60℃ / h, and the temperature is raised to 1210℃ and held for 4 hours.

[0059] 9. Composite plate rolling. The composite plate rolling process is set with a differential speed of 13% throughout. The first stage rolling temperature is 1080℃, the second stage rolling temperature is 930℃, the intermediate thickness is 87mm, and the final rolling temperature is 810℃.

[0060] 10. Laminar flow cooling. Inlet water temperature is 760℃, and final cooling temperature is 580℃.

[0061] 11. The composite billet did not crack during subsequent heating and rolling. The interfacial shear strength after hot rolling was 310 MPa, the interfacial bonding rate was 100%, the bonding performance was good, and the proportion of duplex ferrite was 55%. Example 3

[0062] The stainless steel used in this embodiment is duplex stainless steel S23043, and the carbon steel used is Q345R.

[0063] The rolled stainless steel cladding is 2mm thick, and the carbon steel base layer is 12mm thick.

[0064] 1. Raw material preparation for billet assembly. Carbon steel is continuously cast into billets after converter smelting and ladle refining (LF). The thickness of the carbon steel billets is 230mm. After the billets come off the production line, they are stacked for cooling. One billet is placed at the bottom, and carbon steel billets for composite billet making are placed in the middle of the stack. Three billets are placed on the top layer. The unevenness of the carbon steel billets for composite billet making is 4mm, and they are used as the base material for the composite plate. Stainless steel billets (200mm thick) are rolled into stainless steel medium plates with a thickness of 38mm, which are used as the cladding material for the composite plate. The base and cladding thickness ratio is 6:1.

[0065] 2. Pretreatment of Stainless Steel Medium Plates. First, the stainless steel medium plates used for the composite cladding are solution-treated. The solution treatment temperature is controlled at 950-1050℃, and the holding time is controlled at 1.5 min / mm. Then, they are water-cooled to room temperature. Next, the solution-treated stainless steel medium plates are straightened to achieve a flatness of 5 mm.

[0066] 3. Surface Treatment of Raw Materials for Assembly. ① The carbon steel billet to be assembled is milled on one side to remove surface defects such as iron oxide scale, cracks, and slag inclusions, achieving a metallic finish. ② The stainless steel to be assembled surface is ground using an automatic grinding machine to remove the passivation layer and achieve a metallic finish. ③ Both the milled carbon steel billet and the ground stainless steel medium plate to be assembled are ground using a manual grinding machine with a 120-grit grinding wheel. The surface roughness of the carbon steel after surface treatment is Ra2.5μm, and the surface roughness of the stainless steel after surface treatment is Ra3.0μm.

[0067] 4. Cleaning. First, use compressed air without moisture to blow away the surface dust or iron dust; then use acetone or a volatile alkaline cleaning agent to clean the dust particles that cannot be blown away.

[0068] 5. Billet Assembly. First, place the carbon steel billet on the lower layer with the ground surface facing up. Then, flip the stainless steel middle plate along with the spare carbon steel billet so that the ground stainless steel surface faces down. Hoist it and slowly align it with the lower layer billet, with a 0.9mm gap between the composite surfaces. After assembly, the upper pressure billet is sent into the vacuum chamber.

[0069] 6. Electron beam sealing in the vacuum chamber. ① Evacuate the vacuum chamber to a vacuum level of 4.0 × 10⁻⁶. -2 Pa. ② Spot weld the four sides of the composite blank at 300mm intervals. ③ Position the electron beam gun directly in front of the center of the weld. ④ Weld the two long sides first, then the two short sides. ⑤ Use a welding beam current of 200mA, a welding voltage of 75KV, and a welding speed of 140mm / min.

[0070] 7. Inspection of composite billet welds. After the composite billet is sealed, the spare carbon steel casting billet and stainless steel are separated and removed at the spot welding position. Then, the weld is inspected by ultrasonic testing to ensure there are no defects such as cracks or porosity, and the penetration depth is 45mm.

[0071] 8. Heating of composite billets. The composite billets are heated in the ingot furnace at a rate of 70℃ / h in the first stage, and held at 1050℃ for 4 hours. In the second stage, the heating rate is 50℃ / h, and the temperature is raised to 1230℃ and held for 4 hours.

[0072] 9. Composite Plate Rolling. The composite plate rolling process is set with a differential speed of 12% throughout. The first stage rolling temperature is 1050℃, the second stage rolling temperature is 930℃, the intermediate thickness is 56mm, and the final rolling temperature is 850℃.

[0073] 10. Laminar flow cooling. The inlet water temperature is 800℃, and the final cooling temperature is 610℃.

[0074] 11. The composite billet showed no cracking during heating and rolling. The interfacial shear strength after hot rolling was 342 MPa, the interfacial bonding rate was 100%, the bonding performance was good, and the proportion of duplex ferrite was 45%.

[0075] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for manufacturing a duplex stainless steel and carbon steel asymmetric rolled composite plate, characterized in that: Includes the following steps: Step 1: Raw material preparation for billet assembly: Carbon steel is continuously cast into billets after being smelted in a converter and refined in a ladle. The thickness of the carbon steel billets is 200-280mm. After the carbon steel billets come off the production line, they are stacked and stored for cooling for no less than 3 days. One carbon steel billet is placed at the bottom, and the carbon steel billet for composite billet making is placed in the middle of the stack. Two carbon steel billets are placed at the top, ensuring that the flatness of the carbon steel billet for composite billet making is ≤5mm. It is used as the base material for composite plates. Stainless steel billets are rolled into stainless steel medium plates with a thickness of 10-67mm. They are used as the cladding material for composite plates. The thickness ratio of the base layer to the cladding layer is (3-28):

1. Step 2: Pretreatment of stainless steel medium plate: First, the stainless steel medium plate used for the composite plate cladding is solution treated. The solution treatment temperature is controlled at 950-1100℃, and the holding time is controlled at 1.5min / mm. After water cooling to room temperature, the solution treated stainless steel medium plate is pickled to remove the oxide scale on the surface of the stainless steel medium plate and passivated. After pickling, it is straightened to make the unevenness of the stainless steel medium plate ≤7mm. Step 3: Surface treatment of raw materials for assembly: ① The carbon steel billet to be assembled is milled on one side to remove surface iron oxide scale, cracks, and slag inclusions, and the surface is processed to produce a metallic color; ② The stainless steel medium plate to be assembled is ground with an 80-mesh flap wheel automatic grinding machine to remove the passivation layer and produce a metallic color; ③ The carbon steel billet after milling and the stainless steel medium plate to be assembled are both ground with a manual grinding machine using a 100-120 mesh grinding wheel, and the surface roughness after surface treatment reaches Ra2.0-4.0μm; Step 4: Cleaning: First, use dry compressed air to blow away surface dust or iron dust. Then, use acetone or a volatile alkaline cleaning agent to clean any remaining dust particles that cannot be blown away. Cleaning time should be 3-5 minutes per minute. 2 ; Step 5: Billet Assembly: First, place the carbon steel billet on the lower layer with the ground surface facing up. Then, flip the stainless steel middle plate so that the ground surface of the stainless steel faces down. Hoist it and align it with the lower carbon steel billet. Use a flattening machine to press down the stainless steel middle plate to ensure that the gap between the composite surfaces is ≤1mm. Spot weld the four sides with a spot weld length of 40-60mm and a spot weld interval of 300-500mm. After assembly, it becomes a composite billet. Press the carbon steel billet on the composite billet and send it into the vacuum chamber. Step Six: Electron Beam Sealing in Vacuum Chamber: ① Evacuate the vacuum chamber to a vacuum level ≤7.5×10⁻⁶ -2 Pa; ② Then spot weld the four sides of the composite billet, with an interval of 200-300mm; ③ Position of the electron beam gun: The billet assembly method adopts direct welding of stainless steel medium plate and carbon steel cast billet, and the electron beam gun should be directly facing the center of the weld; ④ Welding sequence is to weld the two long sides first, and then weld the two short sides; ⑤ The sealing welding process adopts a welding beam current of 140-200mA, a welding voltage of 65-75KV, and a welding speed of 100-150mm / min; Step 7: Inspection of composite billet welds: After the composite billet has been sealed and welded, the carbon steel billet pressing on it is removed, and then the weld is inspected by ultrasonic testing to ensure that there are no cracks or pores, and that the penetration depth is 35-50mm. Step 8: Composite Billet Heating: Before heating the composite billet in the ingot furnace, place a carbon steel pad billet at the bottom, and place the composite billet on the pad billet with the stainless steel side facing down. The length and width of the pad billet should not be smaller than the composite billet, ensuring that the composite billet is placed in the middle of the pad billet, pressing down the four sides to suppress weld deformation. Next, a two-stage heating process is adopted in the ingot furnace. The furnace is loaded at a furnace temperature of 500℃-600℃. The first stage heating rate is 70-90℃ / h, and the temperature is raised to 1000-1100℃ and held for 4-6 hours. The second stage heating rate is 50-70℃ / h, and the temperature is raised to 1200-1230℃ and held for 4-6 hours. Step 9: Composite plate rolling: Two-stage rolling is adopted. The first stage rolling temperature is 1000-1080℃, the second stage rolling temperature is ≤930℃, the intermediate thickness is 2-4 times the finished product thickness, and the final rolling temperature is controlled at 830±20℃. Step 10: Laminar flow cooling: ACC laminar flow cooling is adopted, with the inlet water temperature controlled at 780±20℃ and the final cooling temperature controlled at 600±20℃.

2. A method for manufacturing a duplex stainless steel and carbon steel asymmetric rolled composite plate, characterized in that: In step two, the pickling concentration is HNO3: 120-300 g / L, HF: 15-50 g / L, and the pickling speed is 2-8 m / min.

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