Ferritic stainless steel and carbon steel asymmetric composite billet and method of making same

Abstract

The present application belongs to the technical field of composite plate manufacturing, and particularly relates to a ferrite stainless steel and carbon steel asymmetric composite blank and a manufacturing method thereof. The manufacturing method of the ferrite stainless steel and carbon steel asymmetric composite blank comprises the following steps: blank assembling raw material preparation, stainless steel middle plate pretreatment, blank assembling raw material surface treatment, cleaning, blank assembling and vacuum chamber electron beam sealing. The present application has simple process, low cost, improved blank assembling efficiency, is suitable for mass production of products, and can obtain ferrite stainless steel and carbon steel asymmetric composite blanks with excellent quality.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite plate manufacturing, and particularly relates to a ferritic stainless steel and carbon steel asymmetric composite blank and a manufacturing method thereof. BACKGROUND

[0002] The stainless steel (A) + carbon steel (B) composite material has the material properties of different steel types, and compared with a product made of stainless steel or carbon steel, meets the high strength and processing performance requirements of carbon steel as a structural component material in use function, has excellent corrosion resistance, wear resistance and aesthetic appearance of stainless steel, greatly reduces the use amount of stainless steel, saves the use amount of valuable metals such as chromium and nickel, is a new type of material with higher cost performance, higher efficiency and low carbon environmental protection, and has a wide application prospect.

[0003] The production methods of the composite plate mainly include explosion method and hot rolling method. The explosion method uses high temperature and high pressure impact generated by explosives to make the interfaces of two metals fuse, the interface is corrugated, and the bonding strength is high, but the explosion method is affected by climate, environment, has low production efficiency, the size of the composite plate is limited, and the plate shape is poor, and is not suitable for producing relatively thin composite steel plates with a total thickness of less than 10 mm. The hot rolling method is a method for realizing atomic intermetallic bonding of base plate and composite plate under high temperature and large pressure by using a plate rolling mill or a hot continuous rolling mill, the interface is planar, the bonding strength is high, and the production efficiency is high, and the hot rolling method is not affected by climate, environment and other external factors, and can be mass-produced. The existing rolling composite technology mainly adopts four-layer (ABBA) or three-layer (ABA) symmetrical rolling, and needs to increase subsequent plate splitting work, so the process is complicated, the process cost is high, and the yield is low. The (A+B) type asymmetric group blank rolling composite steel coil has the advantages of high efficiency, high yield and high quality stability.

[0004] Due to the difference in material properties, the rolling of the composite of different steel types causes rolling difficulty, and the most important thing for rolling composite is how to realize the group blanking of stainless steel and carbon steel. The (A+B) type asymmetric group blanking refers to directly welding the stainless steel plate and the carbon steel casting blank, and the quality of the welding seam needs to be high, and it must be ensured that the base plate and the composite plate cannot crack before being combined.

[0005] Therefore, in order to solve this problem, the present application urgently needs to provide a manufacturing method of a ferritic stainless steel and carbon steel asymmetric composite blank, so as to obtain the ferritic stainless steel and carbon steel asymmetric group blank, and realize the effect of not cracking in the rolling process of the composite blank. SUMMARY

[0006] In view of the defects of the prior art, the present application provides a ferritic stainless steel and carbon steel asymmetric composite blank and a manufacturing method thereof.

[0007] The present application is realized by the following technical solutions:

[0008] A method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel, comprising:

[0009] (1) The surface to be composited of the carbon steel ingot is subjected to single-side milling to obtain a spare carbon steel ingot; the ferritic stainless steel middle plate is annealed and straightened.

[0010] (2) spot welding the ferritic stainless steel middle plate to the four sides of the spare ingot by electric welding, and then grinding and cleaning the surface to be composited of the ferritic stainless steel middle plate to obtain a treated stainless steel middle plate;

[0011] (3) taking another piece of the spare carbon steel ingot, grinding and cleaning the surface to be composited to obtain a treated carbon steel ingot;

[0012] (4) placing the surface of the treated carbon steel ingot to be composited upward, and placing the surface of the treated stainless steel middle plate to be composited downward, and slowly aligning them with the treated carbon steel ingot to obtain an assembly;

[0013] (5) The billet assembly is sent into a vacuum chamber, and after vacuuming, the treated carbon steel billet and the ferritic stainless steel middle plate are electron beam sealed by an electron beam gun. After the sealing is completed, the spare carbon steel billet fixed on the ferritic stainless steel middle plate by spot welding is removed to obtain an asymmetric composite billet of ferritic stainless steel and carbon steel.

[0014] In the above-mentioned method for manufacturing the asymmetric composite billet of ferritic stainless steel and carbon steel, the annealing temperature is 650-750°C, the holding time is 7-9h, and after the holding is completed, the furnace is cooled to 280-300°C and then air-cooled to room temperature.

[0015] In the above-mentioned method for manufacturing the asymmetric composite billet of ferritic stainless steel and carbon steel, the ratio of the thickness of the carbon steel billet to the thickness of the ferritic stainless steel mid-plate is (4-28):1.

[0016] In the above-mentioned method for manufacturing asymmetric composite billets of ferritic stainless steel and carbon steel, the carbon steel billets are stacked and stored for stack cooling after continuous casting, wherein one billet is placed on the bottom layer, the carbon steel billet for composite billet making is placed in the middle of the stack, and three billets are placed on the top layer, ensuring that the unevenness of the carbon steel continuous casting billet for composite billet making is ≤5mm.

[0017] In the above-mentioned method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel, in step (2), the length of the spot welding is 40-60 mm, and the spot welding interval is 300-500 mm.

[0018] The manufacturing method of the ferritic stainless steel and carbon steel asymmetric composite blank, in the step (2) and the step (3), the grit size of the abrasive wheel piece used in the grinding is 60-100 mesh, and the roughness of the surface to be compounded of the stainless steel middle plate and the carbon steel casting blank after the grinding is Ra2.0-4.0 microns.

[0019] The manufacturing method of the ferritic stainless steel and carbon steel asymmetric composite blank, the vacuum degree of the vacuum chamber is ≤7.5*10 -2 Pa; the electron beam sealing welding is performed in the way of four-edge spot welding, the spot welding length is 100-150 mm, and the interval distance is 200-300 mm.

[0020] The manufacturing method of the ferritic stainless steel and carbon steel asymmetric composite blank, the electron beam gun is offset to the carbon steel side by 1.0-2.0 mm relative to the central position of the welding seam, the welding beam current is 160-240 mA, the welding voltage is 75-85 KV, and the welding speed is 170-220 mm / min.

[0021] In another aspect, the present application also provides a ferritic stainless steel and carbon steel asymmetric composite blank, which is manufactured by the above manufacturing method.

[0022] In still another aspect, the present application also provides a ferritic stainless steel and carbon steel asymmetric composite plate, which is rolled by the above ferritic stainless steel and carbon steel asymmetric composite blank.

[0023] The technical scheme of the present application has the following beneficial effects:

[0024] (1) The present application provides a manufacturing method of a ferritic stainless steel and carbon steel asymmetric composite blank according to the characteristics of the large thickness ratio of the ferritic stainless steel and carbon steel group blank raw material, the large processing and welding difficulty, etc., the method is simple in process, low in cost, improves the blank manufacturing efficiency, is suitable for mass production of products, and can obtain a ferritic stainless steel and carbon steel asymmetric composite blank with excellent quality.

[0025] (2) The composite blank prepared according to the method of the present application has a shear strength τ: 362-410 MPa, an interface bonding rate of 100%, and good bonding performance after being heated and rolled into a composite plate.

[0026] (3) The manufacturing method of the asymmetric composite billet of ferritic stainless steel and carbon steel of the present invention, during vacuum electron beam sealing welding, a reasonable welding sequence can effectively reduce stress concentration at the sealing joint and improve the reliability of the sealing joint. The combined effect of spot welding of the stainless steel middle plate and the spare carbon steel ingot can effectively reduce the degree of welding deformation of the stainless steel and reduce the generation of microcracks in the weld. The reduction of stress concentration and welding deformation can not only improve welding efficiency, but also enable the composite billet to maintain the vacuum effectiveness of the bonding surface during the subsequent heating and rolling process, thereby enhancing the composite effect. In addition, the reduction of stress concentration and welding deformation can not only improve welding efficiency, but also enable the composite billet to maintain the vacuum effectiveness of the bonding surface during the subsequent heating and rolling process, thereby enhancing the composite effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Various other advantages and benefits will become apparent to those skilled in the art by reading the following detailed description of the preferred embodiment.The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present invention.

[0028] Figure 1 This is a schematic diagram of the assembly before sealing welding;

[0029] Figure 2 A schematic diagram of a composite billet after sealing and welding with the spare billet removed;

[0030] Explanation of symbols: 1-spare carbon steel ingot, 2-ferritic stainless steel middle plate, 3-spot welding position, 4-sealing welding position. DETAILED DESCRIPTION

[0031] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments. Except for the following contents, the process of the present invention adopts conventional methods or devices in the art. Unless otherwise specified, the following terms have the meanings commonly understood by those skilled in the art.

[0032] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0033] The market prospects for stainless steel composite plate products are broad, with high technical requirements and high demands on the integrated system control of the production line's process and equipment.

[0034] The present invention relates to an asymmetric composite blank of ferrite stainless steel and carbon steel and a manufacturing method thereof. According to the present invention, the quality of the sealing and welding composite blank can be effectively improved, and the produced composite plate has excellent bonding performance.

[0035] Specifically, the method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel of the present invention includes the following steps: billet raw material preparation → stainless steel middle plate pretreatment → billet raw material surface treatment → cleaning → billet assembly → vacuum chamber electron beam sealing welding.

[0036] The following is a detailed introduction to each step of the method for manufacturing the asymmetric composite billet of ferritic stainless steel and carbon steel of the present invention.

[0037] Preparation of blank stock

[0038] In some embodiments, the carbon steel ingot has a thickness of 200-280 mm and is produced by continuous casting the carbon steel after converter smelting and furnace refining (LF).

[0039] After the ingots come off the production line, they are stacked and stored for cooling. One ingot is placed on the bottom layer, the carbon steel continuous casting ingot for composite billet production is placed in the middle of the stack, and three ingots are placed on the top layer. This ensures that the unevenness of the spare carbon steel ingots is ≤ 5 mm. The stack cooling process for carbon steel ingots employed in this invention ensures that the unevenness of the ingots is minimized, facilitating subsequent welding and assembly.

[0040] Among them, ferritic stainless steel middle plate is obtained by rolling stainless steel ingot.

[0041] In some embodiments, the ferritic stainless steel ingot has a thickness of 200 mm, and after rolling, a ferritic stainless steel mid-plate with a thickness of 10-50 mm is obtained.

[0042] In some preferred embodiments, the ratio of the thickness of the carbon steel ingot to the thickness of the ferritic stainless steel mid-plate is (4-28):1. The large ratio of the thickness of the carbon steel ingot to the thickness of the ferritic stainless steel mid-plate employed in the present invention allows for a wide range of composite plate specifications to be produced, meeting market demand.

[0043] The stainless steel is any one of ferritic stainless steels; the carbon steel is any one of plain carbon steel, low carbon steel and alloy steel.

[0044] Pre-treatment of stainless steel plate

[0045] The inventors have found through research that a reasonable annealing process can make the ferritic stainless steel structure soften evenly, improve internal stress, reduce the degree of welding deformation of ferritic stainless steel, effectively reduce the cracking rate in the subsequent heating and rolling process, and enhance the composite effect.

[0046] In some preferred embodiments, the pretreatment of the stainless steel middle plate of the present invention includes: first annealing the stainless steel middle plate used as the composite plate cladding material, and then straightening the annealed stainless steel middle plate to make the unevenness of the stainless steel middle plate ≤7mm.

[0047] Further preferably, the annealing temperature of the annealing is controlled at 650-750° C., the holding time is controlled at 7-9 hours, and after holding, the furnace is cooled to 280-300° C. and then air-cooled to room temperature.

[0048] Surface treatment of blank stock

[0049] In some embodiments, the present invention performs single-side milling on the surface to be composited of the carbon steel ingot to remove surface defects such as surface oxide scale, cracks, slag inclusions, and process the surface to produce a metallic color.

[0050] Because ferritic stainless steel mid-plates are relatively thin, they are prone to deformation during milling, resulting in uneven milling of the surface. Therefore, the present invention first pairs the ferritic stainless steel mid-plate with a spare carbon steel ingot that has been single-sided milled and has a straight plate shape, spot-welding the four sides together. The surface to be composited of the ferritic stainless steel mid-plate is then single-sided milled to remove the passivation layer and achieve a metallic color. This spot welding combination with the spare carbon steel ingot effectively suppresses plate deformation during milling, reduces the occurrence of microcracks in the weld, and ensures uniform and efficient surface processing, meeting the requirements for ingot assembly.

[0051] In some preferred embodiments, the spot welding length is 40-60 mm, and the spot welding interval is 300-500 mm.

[0052] Furthermore, it has been found in practice that a hard and brittle hardened layer is conducive to achieving rolling composite and improving the interface bonding strength of the composite plate. Based on this, the present invention uses a manual grinding wheel machine to grind the milled spare carbon steel ingot and the ferritic stainless steel middle plate to be composited.

[0053] In some preferred embodiments, the abrasive particle size of the grinding wheel used is 60-100 mesh. After surface treatment, the roughness of the surface to be composited reaches Ra2.0-4.0 μm, thereby effectively removing the surface oxide scale and forming a surface hardened layer. The hard and brittle hardened layer is conducive to achieving rolling composite and improving the interface bonding strength of the composite plate.

[0054] Cleaning

[0055] In some embodiments, the present invention first uses compressed air without moisture to blow away the floating dust or iron dust on the surface of the surface to be composited; and then uses acetone or a volatile alkaline cleaning agent to clean the dust particles on the surface that cannot be blown away.

[0056] Blanking

[0057] In the process of assembling the blanks, the standby carbon steel casting blank is placed in the lower layer with the ground surface facing upward, the ferritic stainless steel plate is turned over with the ground surface facing downward, and is hoisted and slowly aligned with the lower layer of the standby carbon steel casting blank, so as to ensure that the assembly gap between the composite surfaces is ≤1mm, thereby improving the welding quality and ensuring the welding strength.

[0058] wherein, Figure 1 A perspective view of the assembled blanks before sealing is shown, and the ferritic stainless steel plate is fixed to another standby carbon steel casting blank by spot welding, and the ferritic stainless steel plate and the standby carbon steel casting blank are fixed by composite surface sealing. Figure 1 As can be seen, the standby carbon steel casting blank 1 is located in the lower layer, the ferritic stainless steel plate 2 is fixed to another standby carbon steel casting blank 1 by spot welding 3, and the ferritic stainless steel plate 2 and the standby carbon steel casting blank 1 are fixed by composite surface sealing 4.

[0059] Vacuum chamber electron beam seal welding

[0060] The assembled blanks are sent into the vacuum chamber, and after vacuumizing, the treated carbon steel casting blank and the ferritic stainless steel plate are electron beam sealed by an electron beam gun, the standby carbon steel casting blank fixed on the ferritic stainless steel plate by spot welding is removed after sealing, and an asymmetric composite blank of ferritic stainless steel and carbon steel is obtained.

[0061] In practice, with the increase of vacuum degree, the composite effect is enhanced, which is more conducive to slab composite. In some preferred embodiments, the vacuum degree of the vacuum chamber of the present application reaches ≤7.5×10 -2 Pa.

[0062] Preferably, the electron beam sealing is carried out in the form of four-edge spot welding, the spot welding length is 100-150mm, and the interval distance is 200-300mm, thereby effectively reducing the stress concentration at the sealing joint and improving the reliability of the sealing joint.

[0063] The assembling method adopted by the present invention is direct welding of stainless steel and carbon steel. When welding dissimilar metals, the thermocouple effect may generate a magnetic field, causing the electron beam to deviate to the side with a stronger magnetic field, resulting in a welding deviation problem. Therefore, offset compensation needs to be performed during the sealing process. Since ferritic stainless steel has a strong magnetism, the electron beam gun must be pre-shifted 1.0-2.0 mm toward the carbon steel side relative to the center of the weld. During welding, the electron beam will deviate toward the stainless steel side, so that the weld fusion position is exactly in the middle of the weld, which can effectively ensure the weld strength. For ferrite, the welding sequence is preferably to weld the two long sides first, then 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 combination fixing effect of the ferritic stainless steel middle plate and the spare carbon steel ingot can effectively reduce the degree of welding deformation of the ferritic stainless steel during the sealing process and reduce the generation of microcracks 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 in the subsequent heating and rolling process of the composite billet, thereby enhancing the composite effect.

[0064] Furthermore, since the present invention uses ferritic stainless steel as the cladding layer, ferritic stainless steel is sensitive to heat input. When the heat input is too high, the grains in the heat-affected zone (HAZ) tend to grow, resulting in a decrease in the plastic toughness of the HAZ. Therefore, the sealing process needs to be controlled in a targeted manner to ensure the weld depth while also enhancing the weld strength.

[0065] In some preferred embodiments, the sealing welding process uses a welding beam current of 160-240 mA. When the beam current is too low, the heat input is too low, resulting in incomplete welding. When the beam current is too high, it will cause defects such as reduced plastic toughness in the weld heat affected zone due to excessive heat input.

[0066] In some preferred embodiments, the welding voltage is 75-85 kV. When the voltage is too low, the weld penetration will be insufficient, while when the voltage is too high, the weld will be too wide.

[0067] In some preferred embodiments, the welding speed is 170-220 mm / min. If the welding speed is too fast, it will result in incomplete welding, and if the welding speed is too slow, it will cause weld concavity.

[0068] The sealing welding process of the present invention is not only simple to operate but also has high welding efficiency and can effectively ensure the quality of the sealing welding of the composite blank.

[0069] In order to ensure good performance of the composite billet, in some preferred embodiments, the method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel of the present invention further includes a composite billet weld detection step.

[0070] Composite blank weld inspection

[0071] The present application adopts the ultrasonic flaw detection mode to inspect whether the weld has cracks, pores and other defects, and ensures that the penetration depth is greater than or equal to 35 mm.

[0072] The manufacturing method of the ferritic stainless steel and carbon steel asymmetric composite blank has simple process, low cost, and improves the blank manufacturing efficiency, is suitable for mass production of products, and can obtain the ferritic stainless steel and carbon steel asymmetric composite blank with excellent quality.

[0073] In another aspect, the present application also provides a ferritic stainless steel and carbon steel asymmetric composite blank, which is manufactured by the above manufacturing method. The structure is as shown in Figure 2 .

[0074] It is detected that the composite blank prepared by the method of the present application has no cracking phenomenon in the subsequent heating and rolling process, the interface shear strength of the composite plate after hot rolling is greater than or equal to 350 MPa, the interface bonding rate is 100%, and the bonding performance is good.

[0075] Embodiment

[0076] The present application will be further described by way of examples, but the present application is not limited to the scope of the examples. The experimental methods not specified in the following examples are carried out according to the conventional methods and conditions.

[0077] Example 1

[0078] The stainless steel used in this embodiment is ferritic stainless steel T4003, and the carbon steel used is Q450NQR1.

[0079] 1. Preparation of blank raw materials. The carbon steel is continuously cast into a cast blank after converter smelting and secondary refining (LF), the thickness of the carbon steel cast blank is 200 mm, and the cast blank is stacked and stored after being discharged for stack cooling. One cast blank is placed at the bottom, the carbon steel continuous casting blank for composite blank is placed in the middle of the stack, and three cast blanks are placed at the top. The unevenness of the carbon steel continuous casting blank for composite blank is 5 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, the thickness of the stainless steel medium plate is 18 mm, which is used as the composite layer material for the composite plate. The thickness ratio of the base layer and the composite layer is 11:1.

[0080] 2. Pretreatment of stainless steel medium plate. First, the stainless steel medium plate used as the composite layer material for the composite plate is annealed at a temperature of 700℃ for 8h, and then cooled to room temperature after furnace cooling to 290℃. Then, the annealed stainless steel medium plate is straightened to make the unevenness of the stainless steel medium plate 7mm.

[0081] 3. Surface treatment of the raw materials for assembly. ① Perform single-sided milling on the surface of the carbon steel ingot to be composited to remove surface defects such as iron oxide, cracks, slag inclusions, and process out metallic color. ② First, assemble the stainless steel middle plate with a spare carbon steel ingot that has been single-sided milled and has a straight plate shape, and spot weld the four sides together. The spot welding length is 40mm and the spot welding interval is 500mm. Then perform single-sided milling on the surface of the stainless steel middle plate to be composited to remove the passivation layer and process out metallic color. ③ After milling, the carbon steel ingot and the stainless steel middle plate to be composited surfaces are both ground with a manual grinding wheel machine using a 60-mesh grinding wheel. The roughness of the carbon steel surface after treatment is Ra3.8μm, and the roughness of the stainless steel surface after treatment is Ra4.0μm.

[0082] 4. Cleaning: First, use compressed air without moisture to blow away the floating dust or iron dust on the surface; then use acetone or volatile alkaline cleaning agent to clean the dust particles that cannot be blown away.

[0083] 5. Assemble the billets. First, place the carbon steel billet on the bottom layer with the ground surface facing up. Then, flip the stainless steel middle plate and the spare carbon steel billet over so that the ground surface of the stainless steel billet faces down. Lift and slowly align them with the billet on the bottom layer, ensuring a clearance of 0.9mm between the combined surfaces. After assembly, place the billets into the vacuum chamber.

[0084] 6. Electron beam sealing welding in vacuum chamber. ①Evacuate the vacuum chamber to a vacuum degree of 6.5×10 -2 ② Spot weld all four sides of the composite billet, with a spot weld length of 100 mm and a spacing of 200 mm. ③ Pre-set the electron beam gun 1.5 mm toward the carbon steel side relative to the center of the weld. ④ Weld the two long sides first, then the two short sides. ⑤ Use a welding beam current of 200 mA, a welding voltage of 80 kV, and a welding speed of 195 mm / min.

[0085] 7. Composite billet weld inspection. After the welded composite billet is sealed, the spare carbon steel ingot and stainless steel ingot are separated and removed at the spot weld locations. Ultrasonic testing is then performed to inspect the weld seams, confirming the absence of cracks, pores, and other defects. The weld penetration depth is 46mm. The composite billet exhibits no cracking during subsequent heating and rolling. The interfacial shear strength after hot rolling is 387MPa, and the interfacial bonding rate is 100%, indicating excellent bonding performance.

[0086] Example 2

[0087] The stainless steel used in this embodiment is ferritic stainless steel 06Cr13, and the carbon steel used is Q235B.

[0088] 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 280 mm. The slab is stored in a stack after being cast and cooled by piling. One slab is placed at the bottom of the stack. The carbon steel slab used for the composite blank is placed in the middle of the stack. Three slabs are placed at the top of the stack. The unevenness of the carbon steel slab used for the composite blank is 3 mm and is used as the base layer of the composite plate. The stainless steel slab (200 mm thick) is rolled into a stainless steel medium plate. The thickness of the stainless steel medium plate is 10 mm and is used as the composite layer of the composite plate. The thickness ratio of the base layer to the composite layer is 28:1.

[0089] 2. Pretreatment of the stainless steel medium plate. The stainless steel medium plate used for the composite layer is first annealed at a temperature of 750°C for 7 hours. The stainless steel medium plate is then cooled in the furnace to 300°C and then air-cooled to room temperature. The annealed stainless steel medium plate is then straightened so that the unevenness of the stainless steel medium plate is 6 mm.

[0090] 3. Surface treatment of the blank. ① The surface of the carbon steel slab to be combined is milled on one side to remove surface defects such as iron oxide scale, cracks, and slag and to produce a metallic color. ② The stainless steel medium plate is first combined with a spare carbon steel slab that has been milled on one side to produce a flat surface and the four edges are spot-welded together with a length of 50 mm and a spacing of 410 mm. The surface of the stainless steel medium plate to be combined is then milled on one side to remove the passivation layer and to produce a metallic color. ③ The surfaces of the carbon steel slab and the stainless steel medium plate to be combined are ground by hand using a 80 grit abrasive wheel. 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.

[0091] 4. Cleaning. The surface is first blown with compressed air that does not contain moisture to remove floating dust or iron dust. The surface is then cleaned with acetone or an easily volatile alkaline cleaning agent to remove dust particles that cannot be blown away.

[0092] 5. Assembly of the blank. The carbon steel slab is placed on the lower layer with the ground surface facing upwards. The stainless steel medium plate is then placed on the upper layer with the ground surface facing downwards. The two slabs are slowly aligned and the gap between the combined surfaces is 1.0 mm. The assembled blank is then sent to the vacuum chamber.

[0093] 6. Electron beam sealing in the vacuum chamber. ① The vacuum chamber is evacuated to a vacuum degree of 7.5 x 10 -2 Pa. ② The four edges of the combined blank are spot-welded with a length of 125 mm and a spacing of 240 mm. ③ The electron beam gun is offset by 1.0 mm towards the carbon steel side relative to the center of the weld. ④ The welding sequence is to weld the two long sides first and then the two short sides. ⑤ The welding beam current is 160 mA, the welding voltage is 85 KV, and the welding speed is 220 mm / min.

[0094] 7. Composite billet weld inspection. After the welded composite billet is sealed, the spare carbon steel ingot and stainless steel ingot are separated and removed at the spot weld locations. Ultrasonic testing is then performed to verify the welds are free of defects such as cracks and pores, with a penetration depth of 35mm. The composite billet exhibits no cracking during subsequent heating and rolling. The interfacial shear strength after hot rolling is 362MPa, and the interfacial bonding rate is 100%, indicating excellent bonding performance.

[0095] Example 3

[0096] The stainless steel used in this embodiment is ferritic stainless steel 445, and the carbon steel used is Q355B.

[0097] 1. Billet Raw Material Preparation. Carbon steel is smelted in a converter and refined outside the furnace (LF) before being continuously cast into ingots. The thickness of the carbon steel ingots is 230mm. After rolling off the production line, the ingots are stacked and stored for cooling. One ingot is placed on the bottom layer, and the carbon steel continuous-cast ingot for composite billet production is placed in the middle of the stack. Three ingots are placed on the top layer. The carbon steel continuous-cast ingots for composite billet production have a flatness of 4mm and serve as the base material for composite plates. Stainless steel ingots (200mm thick) are rolled into stainless steel mid-plates. The stainless steel mid-plates are 38mm thick and serve as the cladding layer for composite plates. The base-to-cladding thickness ratio is 6:1.

[0098] 2. Pretreatment of the stainless steel mid-plate. First, anneal the stainless steel mid-plate used for the composite plate cladding. The annealing temperature is controlled at 650°C and the holding time is controlled at 9 hours. After holding, the plate is furnace cooled to 280°C and then air-cooled to room temperature. The annealed plate is then straightened to a flatness of 5mm.

[0099] 3. Surface treatment of the raw materials for assembly. ① Perform single-sided milling on the surface of the carbon steel ingot to be composited to remove surface defects such as iron oxide, cracks, slag inclusions, and process out metallic color. ② First, assemble the stainless steel middle plate with a spare carbon steel ingot that has been single-sided milled and has a straight plate shape, and spot weld the four sides together. The spot welding length is 60mm and the spot welding interval is 300mm. Then perform single-sided milling on the surface of the stainless steel middle plate to be composited to remove the passivation layer and process out metallic color. ③ After milling, the carbon steel ingot and the stainless steel middle plate to be composited surfaces are both ground with a manual grinding wheel machine using a 100-mesh grinding wheel. The roughness of the carbon steel surface after treatment is Ra2.0μm, and the roughness of the stainless steel surface after treatment is Ra2.5μm.

[0100] 4. Cleaning: First, use compressed air without moisture to blow away the floating dust or iron dust on the surface; then use acetone or volatile alkaline cleaning agent to clean the dust particles that cannot be blown away.

[0101] 5、Group billets. First, the carbon steel billet is placed in the lower layer, and the grinding surface is upward. Then, the stainless steel middle plate is turned over together with the standby carbon steel billet, so that the stainless steel grinding surface faces downward. The billets are hoisted and slowly aligned with the lower billet, and the combined gap between the composite surfaces is 0.8 mm. After the billets are grouped, they are sent to the vacuum chamber.

[0102] 6、Vacuum chamber electron beam sealing. ① The vacuum chamber is evacuated, and the vacuum degree reaches 4.0 x 10 -2 Pa. ② The composite billet is spot welded on four sides, with a spot welding length of 150 mm and a spacing distance of 300 mm. ③ The electron beam gun is pre-shifted 2.0 mm to the carbon steel side relative to the center of the weld. ④ The welding sequence is to weld the two long sides first, and then the two short sides. ⑤ The welding beam current is 240 mA, the welding voltage is 75 KV, and the welding speed is 170 mm / min.

[0103] 7、Composite billet weld detection. The standby carbon steel billet and the stainless steel are separated and removed at the spot welding position after the sealing of the composite billet is completed. The weld is inspected for cracks, pores and other defects by ultrasonic testing, and the penetration depth is 52 mm. The composite billet does not crack during subsequent heating and rolling, the interface shear strength after hot rolling is 398 MPa, the interface bonding rate is 100%, and the bonding performance is good.

[0104] Example Four

[0105] The stainless steel used in this example is ferritic stainless steel T4003, and the carbon steel used is Q450NQR1.

[0106] 1、Group billet raw material preparation. The carbon steel is continuously cast into a billet after converter smelting and secondary refining (LF). The thickness of the carbon steel billet is 230 mm, and the billet is stacked and stored after being discharged for stack cooling. One billet is placed at the bottom, the carbon steel continuous casting billet for composite production is placed in the middle of the stack, and three billets are placed on the top. The unevenness of the carbon steel continuous casting billet for composite production is 5 mm, which is used as the base layer material for the composite plate; the stainless steel billet (billet thickness 200 mm) is rolled into a stainless steel middle plate, and the thickness of the stainless steel middle plate is 26 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 9:1.

[0107] 2、Stainless steel middle plate pretreatment. First, the stainless steel middle plate used as the composite layer material for the composite plate is annealed at a temperature of 730 ℃ for 7.5 h. After holding, the billet is furnace cooled to 295 ℃ and then air cooled to room temperature. Then, the annealed stainless steel middle plate is straightened to make the unevenness of the stainless steel middle plate 5.5 mm.

[0108] 3. Surface treatment of the raw materials for assembly. ① Perform single-sided milling on the surface of the carbon steel ingot to be composited to remove surface defects such as iron oxide, cracks, slag inclusions, and process out metallic color. ② First, assemble the stainless steel middle plate with a spare carbon steel ingot that has been single-sided milled and has a straight plate shape, and spot weld the four sides together. The spot welding length is 43mm and the spot welding interval is 350mm. Then perform single-sided milling on the surface of the stainless steel middle plate to be composited to remove the passivation layer and process out metallic color. ③ After milling, the carbon steel ingot and the stainless steel middle plate to be composited surfaces are both ground with a manual grinding wheel machine using a 60-mesh grinding wheel. The roughness of the carbon steel surface after treatment is Ra3.9μm, and the roughness of the stainless steel surface after treatment is Ra3.7μm.

[0109] 4. Cleaning: First, use compressed air without moisture to blow away the floating dust or iron dust on the surface; then use acetone or volatile alkaline cleaning agent to clean the dust particles that cannot be blown away.

[0110] 5. Assemble the billets. First, place the carbon steel billet on the bottom layer with the ground surface facing up. Then, flip the stainless steel middle plate and the spare carbon steel billet over so that the ground surface of the stainless steel billet faces down. Hoist and slowly align them with the billet on the bottom layer, ensuring a 1.0mm clearance between the combined surfaces. After assembling, transfer the billets into the vacuum chamber.

[0111] 6. Electron beam sealing welding in vacuum chamber. ①Evacuate the vacuum chamber to a vacuum degree of 5.5×10 -2 ② Spot weld all four sides of the composite billet, with a spot weld length of 140 mm and a spacing of 220 mm. ③ Pre-set the electron beam gun 1.8 mm toward the carbon steel side relative to the center of the weld. ④ Weld the two long sides first, then the two short sides. ⑤ Use a welding beam current of 180 mA, a welding voltage of 78 kV, and a welding speed of 210 mm / min.

[0112] 7. Composite billet weld inspection. After the welded composite billet is sealed, the spare carbon steel ingot and stainless steel ingot are separated and removed at the spot weld locations. Ultrasonic testing is then performed to verify the welds are free of defects such as cracks and pores, with a penetration depth of 45mm. The composite billet exhibits no cracking during subsequent heating and rolling. The interfacial shear strength after hot rolling is 410 MPa, and the interfacial bonding rate is 100%, indicating excellent bonding performance.

[0113] Example 5

[0114] The stainless steel used in this embodiment is ferritic stainless steel 443, and the carbon steel used is Q235B.

[0115] 1. Preparation of blank. Carbon steel is smelted by converter and refined outside the converter (LF) and then cast into billet. The thickness of the carbon steel billet is 200 mm. The billet is stored and cooled by stacking after being discharged. One billet is placed at the bottom. The carbon steel continuous casting billet used for the base layer of the clad plate is placed in the middle of the stack. Three billets are placed at the top. The unevenness of the carbon steel continuous casting billet used for the base layer of the clad plate is 4 mm. Stainless steel billet (billet thickness 200 mm) is rolled into stainless steel medium plate. The thickness of the stainless steel medium plate is 50 mm. The stainless steel medium plate is used for the clad layer of the clad plate. The thickness ratio of the base layer to the clad layer is 4:1.

[0116] 2. Pretreatment of the stainless steel medium plate. The stainless steel medium plate used for the clad layer of the clad plate is first annealed at a temperature of 670 °C for 8.5 h. The stainless steel medium plate is then cooled in the furnace to 286 °C and then air cooled to room temperature. The annealed stainless steel medium plate is then straightened to make the unevenness of the stainless steel medium plate 6.5 mm.

[0117] 3. Surface treatment of the blank. ① The surface of the carbon steel billet to be clad is milled to remove surface scale, cracks and slag and to make the surface metallic. ② The stainless steel medium plate is first milled with a spare carbon steel billet which has been milled on one side to make the plate flat and straight. The four edges are then spot welded together with a length of 56 mm and a distance of 460 mm. The surface of the stainless steel medium plate to be clad is then milled to remove the passivation layer and to make the surface metallic. ③ The surfaces of the carbon steel billet and the stainless steel medium plate to be clad are then ground by hand using a 80 grit abrasive wheel. The roughness of the carbon steel surface after treatment is Ra 3.4 μm and the roughness of the stainless steel surface after treatment is Ra 3.5 μm.

[0118] 4. Cleaning. The surface is first blown with compressed air to remove dust and iron dust. The surface is then cleaned with acetone or volatile alkaline cleaning agent.

[0119] 5. Assembly of the blank. The carbon steel billet is placed on the bottom layer with the ground surface facing upwards. The stainless steel medium plate is then placed on top of the carbon steel billet with the ground surface facing downwards. The two blanks are then slowly aligned with a gap of 0.7 mm between the cladding surfaces. The blanks are then sent to the vacuum chamber.

[0120] 6. Electron beam sealing in the vacuum chamber. ① The vacuum chamber is evacuated to a vacuum degree of 6.0 x 10 -2 Pa. ② The four edges of the blank are spot welded with a length of 115 mm and a distance of 270 mm. ③ The electron beam gun is offset by 1.2 mm to the carbon steel side relative to the center of the weld. ④ The welding sequence is to weld the two long sides first and then the two short sides. ⑤ The welding beam current is 220 mA, the welding voltage is 82 KV and the welding speed is 180 mm / min.

[0121] 7. The composite blank weld joint is detected. The composite blank after sealing is separated and removed from the backup carbon steel casting blank and stainless steel at the spot welding position, and then the weld joint is inspected by ultrasonic flaw detection to check whether there are cracks, pores and other defects, and the penetration depth is 50mm. The composite blank does not crack in the subsequent heating and rolling process, the interface shear strength after hot rolling is 379MPa, the interface bonding rate is 100%, and the bonding performance is good.

[0122] The application has been disclosed above in preferred embodiments, but those skilled in the art should understand that these embodiments are only used to depict the application and should not be understood as limiting the scope of the application. It should be noted that any equivalent changes and substitutions with these embodiments should be considered as covered by the scope of the claims of the application. Therefore, the protection scope of the application should be subject to the scope defined in the claims.

Claims

1. A method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel, characterized in that: include: (1) Single-side milling of the surface to be composited of the carbon steel ingot is performed to obtain a spare carbon steel ingot; the ferritic stainless steel middle plate is annealed and straightened; The annealing temperature is 650-750°C, the holding time is 7-9h, and after the holding is completed, the furnace is cooled to 280-300°C and then air-cooled to room temperature; (2) spot welding the ferritic stainless steel middle plate to the four sides of the spare ingot by electric welding, and then milling, grinding and cleaning the surface to be composited of the ferritic stainless steel middle plate to obtain a processed stainless steel middle plate; (3) taking another piece of the spare carbon steel ingot, grinding and cleaning the surface to be composited to obtain a treated carbon steel ingot; (4) placing the surface of the treated carbon steel ingot to be composited upward, and placing the surface of the treated stainless steel middle plate to be composited downward, and slowly aligning them with the treated carbon steel ingot to obtain an assembly; (5) sending the assembled billet into a vacuum chamber, and after evacuating the vacuum, using an electron beam gun to electron beam seal weld the treated carbon steel billet and the ferritic stainless steel middle plate, and after sealing welding, removing the spare carbon steel billet fixed on the ferritic stainless steel middle plate by spot welding to obtain an asymmetric composite billet of ferritic stainless steel and carbon steel; Wherein, in step (2) and step (3), the particle size of the grinding wheel abrasive used for the grinding is 60-100 mesh, and after grinding, the roughness of the surface to be composited of the stainless steel middle plate and the carbon steel ingot is Ra2.0-4.0 μm; The vacuum degree of the vacuum chamber is ≤7.5×10 -2 Pa; the electron beam sealing is carried out by four-side spot welding, the spot welding length is 100-150mm, and the interval distance is 200-300mm; the electron beam gun is offset 1.0-2.0mm toward the carbon steel side relative to the center position of the weld, the welding beam current is 160-240mA, the welding voltage is 75-85KV, and the welding speed is 170-220mm / min.

2. The method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel according to claim 1, characterized in that: The ratio of the thickness of the carbon steel ingot to the thickness of the ferritic stainless steel mid-plate is (4-28):

1.

3. The method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel according to claim 1, characterized in that: The carbon steel ingots are stacked and stored for stack cooling after continuous casting, wherein one ingot is placed on the bottom layer, the carbon steel ingot for composite ingot making is placed in the middle of the stack, and three ingots are placed on the top layer, ensuring that the unevenness of the carbon steel continuous casting ingot for composite ingot making is ≤5mm.

4. The method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel according to claim 1, characterized in that: In step (2), the length of the spot welding is 40-60 mm, and the spot welding interval is 300-500 mm.

5. An asymmetric composite billet of ferritic stainless steel and carbon steel, characterized in that: The invention is obtained by adopting the manufacturing method according to any one of claims 1 to 4.

6. An asymmetric clad plate of ferritic stainless steel and carbon steel, characterized in that: The asymmetric composite billet of ferritic stainless steel and carbon steel as claimed in claim 5 is rolled.

Images