Ferritic stainless steel and carbon steel asymmetric composite blank and manufacturing method thereof

Abstract

The invention 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. The manufacturing method of the ferritic stainless steel and carbon steel asymmetric composite blank comprises the following working procedures of blank assembly raw material preparation, stainless steel middle plate pretreatment, blank assembly raw material surface treatment, cleaning, blank assembly and vacuum chamber electron beam seal welding. The process is simple, the cost is low, the blank manufacturing efficiency is improved, the method is suitable for mass production of products, and the ferrite stainless steel and carbon steel asymmetric composite blank with excellent quality can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of composite plate manufacturing, and in particular relates to an asymmetric composite billet of ferrite stainless steel and carbon steel and a manufacturing method thereof. Background Art

[0002] The stainless steel (A) + carbon steel (B) composite material combines the material properties of different steel grades. Compared with products made entirely of stainless steel or carbon steel, it not only meets the high strength and processing performance requirements of carbon steel as a structural component material, but also has the excellent corrosion resistance, wear resistance and aesthetics of stainless steel. It also greatly reduces the use of stainless steel and saves the use of precious metals such as chromium and nickel. It is a new type of material with higher cost performance, higher efficiency, low carbon and environmental protection, and has broad application prospects.

[0003] There are two main production methods for composite plates: explosion method and hot rolling method. The explosion method uses the high temperature and high pressure impact generated by explosives to fuse the interface of two metals. The interface is corrugated and has high bonding strength. However, the explosion method is affected by climate and environment, has low production efficiency, limited composite plate size, poor plate shape, and is not suitable for producing thin composite steel plates with a total thickness of less than 10 mm. The hot rolling method is a method of using a medium and thick plate rolling mill or a hot rolling mill to achieve metallurgical bonding between atoms of the substrate and the composite plate under high temperature and high pressure. The interface is planar, has high bonding strength, is not affected by external factors such as climate and environment, has high production efficiency, and can be mass-produced industrially. Existing rolling composite technologies mostly use four-layer (ABBA) or three-layer (ABA) symmetrical rolling, which requires additional subsequent plate separation work, has complicated procedures, high process costs, and low yield rate. The hot rolling method uses (A+B) type different steel grades to roll composite steel coils with asymmetric billets, which has the advantages of high efficiency, high yield rate, and high quality stability.

[0004] Due to the difference in material properties, composite rolling of different steel grades will cause rolling difficulties. The most important thing in rolling composite is how to achieve the assembly of stainless steel and carbon steel. (A+B) type asymmetric assembly of different steel grades refers to the direct welding of stainless steel plates and carbon steel ingots. The quality requirements for the weld are high, and it must be ensured that no cracks occur before the base plate and the composite plate are combined.

[0005] Therefore, in order to solve this problem, the art urgently needs to propose a method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel, so as to obtain an asymmetric billet of ferritic stainless steel and carbon steel and achieve the effect of no cracking during the rolling process of the composite billet. Summary of the invention

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

[0007] The present invention is achieved through 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 processed stainless steel middle plate;

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

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

[0013] (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.

[0014] In the above-mentioned method for manufacturing asymmetric composite billets of ferritic stainless steel and carbon steel, the annealing temperature of the annealing 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 middle plate is (4-28):1.

[0016] In the above-mentioned method for manufacturing an asymmetric composite billet 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] In the above-mentioned method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel, in step (2) and step (3), the particle size of the grinding wheel abrasive used for grinding is 60-100 mesh, and after grinding, the roughness of the surfaces to be composited of the stainless steel middle plate and the carbon steel ingot is Ra2.0-4.0μm.

[0019] In the above-mentioned method for manufacturing asymmetric composite billets of ferrite stainless steel and carbon steel, the vacuum degree of the vacuum chamber is ≤7.5×10 -2 Pa; the electron beam sealing welding is performed by four-side spot welding, the spot welding length is 100-150mm, and the spacing distance is 200-300mm.

[0020] In the above-mentioned method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel, the electron beam gun is offset 1.0-2.0 mm toward the stainless steel side relative to the center position of the weld, 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] On the other hand, the present invention further provides an asymmetric composite billet of ferritic stainless steel and carbon steel, which is manufactured by the above-mentioned manufacturing method.

[0022] In yet another aspect, the present invention further provides an asymmetric composite plate of ferritic stainless steel and carbon steel, which is formed by rolling the asymmetric composite billet of ferritic stainless steel and carbon steel.

[0023] The technical solution of the present invention has the following beneficial effects:

[0024] (1) In view of the characteristics of ferritic stainless steel and carbon steel billet raw materials having a large thickness ratio and being difficult to process and weld, the present invention provides a method for manufacturing asymmetric composite billets of ferritic stainless steel and carbon steel. The method has a simple process and low cost, improves billet making efficiency, is suitable for mass production of products, and can obtain high-quality asymmetric composite billets of ferritic stainless steel and carbon steel.

[0025] (2) After the composite blank prepared by the method of the present invention is heated and rolled into a composite plate, the shear strength τ is 362-410 MPa, the interface bonding rate is 100%, and the bonding performance is good.

[0026] (3) In the manufacturing method of the asymmetric composite billet of ferritic stainless steel and carbon steel of the present invention, a reasonable welding sequence during vacuum electron beam sealing can effectively reduce the 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 welding deformation degree of the stainless steel and reduce the generation of microcracks in the weld. The reduction of stress concentration and welding deformation degree can not only improve the 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 degree can not only improve the 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 of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the 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 method 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 above range is considered to be 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 should be understood to include any and all subranges included therein.

[0033] The market prospects for stainless steel composite plate products are broad, with high technical requirements and high requirements for 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 asymmetric composite billets of ferritic stainless steel and carbon steel of the present invention comprises the following steps: preparation of billet raw materials→pretreatment of stainless steel middle plate→surface treatment of billet raw materials→cleaning→billet assembly→vacuum chamber electron beam sealing welding.

[0036] The steps of the method for manufacturing the asymmetric composite billet of ferritic stainless steel and carbon steel of the present invention are described in detail below.

[0037] Raw material preparation for assembly

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

[0039] After the ingots are off the production line, they are stacked and stored for stack cooling. One ingot is placed on the bottom layer, the carbon steel continuous casting ingot for composite ingot making is placed in the middle of the stack, and three ingots are placed on the top layer to ensure that the unevenness of the spare carbon steel ingots is ≤5mm. The stack cooling process of the carbon steel ingots adopted in the present invention can ensure the unevenness of the ingots, which is conducive to the subsequent welding and assembly of ingots.

[0040] Among them, the ferritic stainless steel middle plate is obtained by rolling the 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 middle 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 middle plate is (4-28): 1. The thickness ratio of the carbon steel ingot to the thickness of the ferritic stainless steel middle plate used in the present invention is large, and the composite plate product produced has a wide range of specifications and can meet market demand.

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

[0044] Stainless steel plate pretreatment

[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 composite 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 the holding time, the furnace is cooled to 280-300° C. and then air-cooled to room temperature.

[0048] Surface treatment of raw materials for assembly

[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, etc., and processes the surface to produce a metallic color.

[0050] Since the ferritic stainless steel middle plate is relatively thin, the plate shape is easily deformed during milling, which will lead to uneven surface milling. Therefore, the present invention first assembles the ferritic stainless steel middle plate with a spare carbon steel billet that has been milled on one side and has a straight plate shape, and spot welds the four sides together, and then performs single-side milling on the surface to be composited of the ferritic stainless steel middle plate to remove the passivation layer and process the metallic color. The spot welding combination with the spare carbon steel billet can effectively inhibit the plate shape deformation of stainless steel during milling, reduce the generation of micro cracks in the weld, make the surface processing uniform and fast, and meet the billet assembly requirements.

[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 Ra2.0-4.0μm, 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 to-be-compounded surface; and then uses acetone or a volatile alkaline cleaning agent to clean the dust particles that cannot be blown away from the surface.

[0056] Assembly

[0057] In the process of billet assembly, the spare carbon steel billet is first placed in the lower layer with the grinding surface facing upward, and then the ferritic stainless steel middle plate is turned over with the grinding surface facing downward, and is hoisted and slowly aligned with the spare carbon steel billet in the lower layer to ensure that the combined gap between the composite surfaces is ≤1mm, thereby improving the welding quality and ensuring the welding strength.

[0058] in, Figure 1 The perspective diagram of the blank assembly before sealing welding is shown. Figure 1 It can be seen that the spare carbon steel ingot 1 is located in the lower layer, the ferritic stainless steel middle plate 2 is fixed to another spare carbon steel ingot 1 by spot welding 3, and the ferritic stainless steel middle plate 2 is fixed to the spare carbon steel ingot 1 by composite surface sealing welding 4.

[0059] Electron beam sealing of vacuum chamber

[0060] The assembled billet 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 sealing, the spare carbon steel billet spot-welded on the ferritic stainless steel middle plate is removed to obtain an asymmetric composite billet of ferritic stainless steel and carbon steel.

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

[0062] Preferably, the electron beam sealing is performed by four-side spot welding, with a spot welding length of 100-150 mm and an interval of 200-300 mm, thereby effectively reducing stress concentration at the sealing joint and improving the reliability of the sealing joint.

[0063] The assembly 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 strong magnetic field, resulting in a welding deviation problem. Therefore, compensation for the offset is required during the sealing process. Since the magnetism of ferritic stainless steel is relatively strong, the electron beam gun should be pre-shifted to the carbon steel side by 1.0-2.0 mm relative to the center of the weld. During welding, the electron beam will deviate to the stainless steel side, so that the weld fusion position is exactly located in the middle of the weld, which can effectively ensure the weld strength. Preferably, for ferrite, the welding sequence is to weld the two long sides first and 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 welding deformation degree of the ferritic stainless steel during the sealing process, and reduce the generation of weld microcracks. 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 blank, and the composite effect can be enhanced.

[0064] Furthermore, since the present invention uses ferritic stainless steel as the composite layer, and ferritic stainless steel is sensitive to heat input, when the heat input is too large, the grains in the heat affected zone of the weld tend to grow, resulting in a decrease in the plastic toughness of the heat affected zone of the weld. Therefore, it is necessary to carry out targeted control of the sealing welding process, while ensuring the depth of the weld, the strength of the weld must also be enhanced.

[0065] In some preferred embodiments, the sealing welding process uses a welding beam current of 160-240 mA. When the beam current is small, the heat input is too low, resulting in incomplete welding. When the beam current is too large, the heat input is too large, resulting in defects such as decreased plastic toughness of the welding heat affected zone.

[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 lead to incomplete penetration, 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 that the composite billet has good performance, 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 billet weld inspection

[0071] The present invention adopts ultrasonic flaw detection to check whether there are defects such as cracks and pores in the weld to ensure that the penetration depth is ≥35mm.

[0072] The method for manufacturing the asymmetric composite billet of ferritic stainless steel and carbon steel of the present invention has simple process, low cost, improved billet making efficiency, is suitable for mass production of products, and can obtain asymmetric composite billets of ferritic stainless steel and carbon steel of good quality.

[0073] On the other hand, the present invention also provides an asymmetric composite billet of ferrite stainless steel and carbon steel, which is manufactured by the above-mentioned manufacturing method. Figure 2 shown.

[0074] After testing, the composite billet prepared according to the method of the present invention has no cracking phenomenon during the subsequent heating and rolling process, the interface shear strength τ of the composite plate after hot rolling is ≥350MPa, the interface bonding rate is 100%, and the bonding performance is good.

[0075] Example

[0076] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods without specific conditions in the following examples are based on conventional methods and conditions.

[0077] Embodiment 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 raw materials for billet assembly. Carbon steel is continuously cast into billets after converter smelting and refining outside the furnace (LF). The thickness of carbon steel billets is 200mm. After the billets are off the line, they are stacked and stored for stack cooling. One billet is placed on the bottom layer. The carbon steel continuous casting billet for composite billet making is placed in the middle of the stack. Three billets are placed on the top layer. The unevenness of the carbon steel continuous casting billet for composite billet making is 5mm, which is used as the base material of the composite plate; stainless steel billets (bill thickness 200mm) are rolled into stainless steel middle plates with a thickness of 18mm, which are used as the composite material of the composite plate. The ratio of base and composite thickness is 11:1.

[0080] 2. Pretreatment of stainless steel middle plate. First, anneal the stainless steel middle plate used for composite plate cladding. The annealing temperature is controlled at 700℃ and the holding time is controlled at 8h. After holding, the furnace is cooled to 290℃ 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 7mm.

[0081] 3. Surface treatment of raw materials for assembly. ① Single-sided milling is performed 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 single-sided milling is performed 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 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 lower layer with the grinding surface facing upwards, then turn over the stainless steel middle plate and the spare carbon steel billet with the grinding surface facing downwards, and slowly align them with the billet on the lower layer. The gap between the composite surfaces is 0.9mm. After assembling, send them into the vacuum chamber.

[0084] 6. Electron beam sealing welding in vacuum chamber. ① Evacuate the vacuum chamber to a vacuum degree of 6.5×10 -2 Pa. ② Spot weld the four sides of the composite billet, with a spot welding length of 100mm and an interval of 200mm. ③ The electron beam gun is pre-shifted 1.5mm to the carbon steel side relative to the center of the weld. ④ The welding sequence is to weld the two long sides first, then the two short sides. ⑤ Use a welding beam current of 200mA, a welding voltage of 80KV, and a welding speed of 195mm / min.

[0085] 7. Inspection of weld seams of composite billets. After the sealing welding is completed, the spare carbon steel billet and stainless steel are separated and removed at the spot welding position, and then the weld is inspected by ultrasonic flaw detection to ensure that there are no defects such as cracks and pores, and the penetration depth is 46mm. The composite billet has no cracking phenomenon during the subsequent heating and rolling process. The interface shear strength after hot rolling is 387MPa, the interface bonding rate is 100%, and the bonding performance is good.

[0086] Embodiment 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 raw materials for billet assembly. Carbon steel is continuously cast into billets after converter smelting and refining outside the furnace (LF). The thickness of the carbon steel billet is 280mm. After the billet is off the line, it is stacked and stored for stack cooling. One billet is placed on the bottom layer. The carbon steel continuous casting billet for composite billet making is placed in the middle of the stack. Three billets are placed on the top layer. The unevenness of the carbon steel continuous casting billet for composite billet making is 3mm, which is used as the base material of the composite plate; stainless steel billets (bill thickness 200mm) are rolled into stainless steel middle plates with a thickness of 10mm, which are used as the composite material of the composite plate. The ratio of base to composite thickness is 28:1.

[0089] 2. Pretreatment of stainless steel middle plate. First, anneal the stainless steel middle plate used for composite plate cladding. The annealing temperature is controlled at 750℃ and the holding time is controlled at 7h. After holding, the furnace is cooled to 300℃ 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 6mm.

[0090] 3. Surface treatment of raw materials for assembly. ① Single-sided milling is performed on the surface of the carbon steel ingot to be composited to remove surface defects such as iron oxide, cracks, slag inclusions, and process the 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 50mm and the spot welding interval is 410mm. Then single-sided milling is performed on the surface of the stainless steel middle plate to be composited to remove the passivation layer and process the metallic color. ③ After milling, the carbon steel ingot and the stainless steel middle plate to be composited are both ground with a manual grinding wheel machine, using an 80-mesh grinding wheel. The roughness of the carbon steel surface after treatment is Ra3.2μm, and the roughness of the stainless steel surface after treatment is Ra3.6μm.

[0091] 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.

[0092] 5. Assemble the billets. First, place the carbon steel billet on the lower layer with the grinding surface facing upwards, then turn over the stainless steel middle plate and the spare carbon steel billet so that the grinding surface of the stainless steel is facing downwards, and slowly align them with the billet on the lower layer. The gap between the composite surfaces is 1.0mm. After assembling, send them into the vacuum chamber.

[0093] 6. Electron beam sealing welding in vacuum chamber. ① Evacuate the vacuum chamber to a vacuum degree of 7.5×10 -2 Pa. ② Spot weld the four sides of the composite billet, the spot welding length is 125mm, and the spacing is 240mm. ③ The electron beam gun is pre-shifted 1.0mm 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 Use a welding beam current of 160mA, a welding voltage of 85KV, and a welding speed of 220mm / min.

[0094] 7. Inspection of the weld seam of the composite billet. After the sealing welding is completed, the spare carbon steel billet and the stainless steel are separated and removed at the spot welding position, and then the weld is inspected by ultrasonic flaw detection to ensure that there are no defects such as cracks and pores, and the penetration depth is 35mm. The composite billet has no cracking phenomenon during the subsequent heating and rolling process. The interface shear strength after hot rolling is 362MPa, the interface bonding rate is 100%, and the bonding performance is good.

[0095] Embodiment 3

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

[0097] 1. Preparation of raw materials for billet assembly. Carbon steel is continuously cast into billets after converter smelting and refining outside the furnace (LF). The thickness of carbon steel billets is 230mm. After the billets are off the line, they are stacked and stored for stack cooling. One billet is placed on the bottom layer. The carbon steel continuous casting billet for composite billet making is placed in the middle of the stack. Three billets are placed on the top layer. The unevenness of the carbon steel continuous casting billet for composite billet making is 4mm, which is used as the base material of the composite plate; stainless steel billets (bill thickness 200mm) are rolled into stainless steel middle plates with a thickness of 38mm, which are used as the composite material of the composite plate. The ratio of base to composite thickness is 6:1.

[0098] 2. Pretreatment of stainless steel middle plate. First, anneal the stainless steel middle plate used for composite plate cladding. The annealing temperature is controlled at 650℃ and the holding time is controlled at 9h. After holding, the furnace is cooled to 280℃ 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 5mm.

[0099] 3. Surface treatment of raw materials for assembly. ① Single-sided milling is performed on the surface of the carbon steel ingot to be composited to remove surface defects such as surface oxide scale, 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 single-sided milling is performed 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 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. Assemble the billets. First, place the carbon steel billet on the lower layer with the grinding surface facing upwards, then turn over the stainless steel middle plate and the spare carbon steel billet so that the grinding surface of the stainless steel is facing downwards, and slowly align them with the billet on the lower layer. The gap between the composite surfaces is 0.8mm. After assembling, send them into the vacuum chamber.

[0102] 6. Electron beam sealing welding in vacuum chamber. ① Evacuate the vacuum chamber to a vacuum degree of 4.0×10 -2 Pa. ② Spot weld the four sides of the composite billet, with a spot welding length of 150mm and an interval of 300mm. ③ The electron beam gun is pre-shifted 2.0mm to the carbon steel side relative to the center of the weld. ④ The welding sequence is to weld the two long sides first, then the two short sides. ⑤ Use a welding beam current of 240mA, a welding voltage of 75KV, and a welding speed of 170mm / min.

[0103] 7. Inspection of weld seams of composite billets. After the weld is completed, the spare carbon steel billet and stainless steel are separated and removed at the spot welding position, and then the weld is inspected by ultrasonic flaw detection to ensure that there are no defects such as cracks and pores, and the penetration depth is 52mm. The composite billet has no cracking during the subsequent heating and rolling process. The interface shear strength after hot rolling is 398MPa, the interface bonding rate is 100%, and the bonding performance is good.

[0104] Embodiment 4

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

[0106] 1. Preparation of raw materials for billet assembly. Carbon steel is continuously cast into billets after converter smelting and refining outside the furnace (LF). The thickness of the carbon steel billets is 230mm. After the billets are off the line, they are stacked and stored for stack cooling. One billet is placed on the bottom layer. The carbon steel continuous casting billet for composite billet making is placed in the middle of the stack. Three billets are placed on the top layer. The unevenness of the carbon steel continuous casting billet for composite billet making is 5mm, which is used as the base material of the composite plate; stainless steel billets (bill thickness 200mm) are rolled into stainless steel middle plates. The thickness of the stainless steel middle plates is 26mm, which is used as the composite material of the composite plate. The ratio of base and composite thickness is 9:1.

[0107] 2. Pretreatment of stainless steel middle plate. First, anneal the stainless steel middle plate used for composite plate cladding. The annealing temperature is controlled at 730℃ and the holding time is controlled at 7.5h. After holding, the furnace is 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 5.5mm.

[0108] 3. Surface treatment of raw materials for assembly. ① Single-sided milling is performed on the surface of the carbon steel ingot to be composited to remove surface defects such as iron oxide, cracks, slag inclusions, and process the 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 single-sided milling is performed on the surface of the stainless steel middle plate to be composited to remove the passivation layer and process the metallic color. ③ After milling, the carbon steel ingot and the stainless steel middle plate to be composited 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 lower layer with the grinding surface facing upwards, then turn over the stainless steel middle plate and the spare carbon steel billet so that the grinding surface of the stainless steel is facing downwards, and slowly align them with the billet on the lower layer. The gap between the composite surfaces is 1.0mm. After assembling, send them into the vacuum chamber.

[0111] 6. Electron beam sealing welding in vacuum chamber. ① Evacuate the vacuum chamber to a vacuum degree of 5.5×10 -2 Pa. ② Spot weld the four sides of the composite billet, the spot welding length is 140mm, and the spacing is 220mm. ③ The electron beam gun is pre-shifted 1.8mm 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 Use a welding beam current of 180mA, a welding voltage of 78KV, and a welding speed of 210mm / min.

[0112] 7. Inspection of the weld seam of the composite billet. After the sealing welding is completed, the spare carbon steel billet and the stainless steel are separated and removed at the spot welding position, and then the weld is inspected by ultrasonic flaw detection to ensure that there are no defects such as cracks and pores, and the penetration depth is 45mm. The composite billet has no cracking phenomenon during the subsequent heating and rolling process. The interface shear strength after hot rolling is 410MPa, the interface bonding rate is 100%, and the bonding performance is good.

[0113] Embodiment 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 raw materials for billet assembly. Carbon steel is continuously cast into billets after converter smelting and refining outside the furnace (LF). The thickness of carbon steel billets is 200mm. After the billets are off the line, they are stacked and stored for stack cooling. One billet is placed on the bottom layer. The carbon steel continuous casting billet for composite billet making is placed in the middle of the stack. Three billets are placed on the top layer. The unevenness of the carbon steel continuous casting billet for composite billet making is 4mm, which is used as the base material of the composite plate; stainless steel billets (bill thickness 200mm) are rolled into stainless steel middle plates with a thickness of 50mm, which are used as the composite material of the composite plate. The ratio of base to composite thickness is 4:1.

[0116] 2. Pretreatment of stainless steel middle plate. First, anneal the stainless steel middle plate used for composite plate cladding. The annealing temperature is controlled at 670℃ and the holding time is controlled at 8.5h. After holding, the furnace is cooled to 286℃ 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 6.5mm.

[0117] 3. Surface treatment of raw materials for assembly. ① Single-sided milling is performed on the surface of the carbon steel ingot to be composited to remove surface defects such as iron oxide, cracks, slag inclusions, and process the 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 56mm and the spot welding interval is 460mm. Then single-sided milling is performed on the surface of the stainless steel middle plate to be composited to remove the passivation layer and process the metallic color. ③ After milling, the carbon steel ingot and the stainless steel middle plate to be composited are both ground with a manual grinding wheel machine, using an 80-mesh grinding wheel. The roughness of the carbon steel surface after treatment is Ra3.4μm, and the roughness of the stainless steel surface after treatment is Ra3.5μm.

[0118] 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.

[0119] 5. Assemble the billets. First, place the carbon steel billet on the lower layer with the grinding surface facing upwards, then turn over the stainless steel middle plate and the spare carbon steel billet so that the grinding surface of the stainless steel is facing downwards, and slowly align them with the billet on the lower layer. The gap between the composite surfaces is 0.7mm. After assembling, send them into the vacuum chamber.

[0120] 6. Electron beam sealing welding in vacuum chamber. ① Evacuate the vacuum chamber to a vacuum degree of 6.0×10 -2 Pa. ② Spot weld the four sides of the composite billet, the spot welding length is 115mm, and the spacing is 270mm. ③ The electron beam gun is pre-shifted 1.2mm 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 Use a welding beam current of 220mA, a welding voltage of 82KV, and a welding speed of 180mm / min.

[0121] 7. Inspection of weld seams of composite billets. After the weld is completed, the spare carbon steel billet and stainless steel are separated and removed at the spot welding position, and then the weld is inspected by ultrasonic flaw detection to ensure that there are no defects such as cracks and pores, and the penetration depth is 50mm. The composite billet has no cracking during 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 present invention has been disclosed above with preferred embodiments, but those skilled in the art should understand that these embodiments are only used to describe the present invention and should not be understood as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to these embodiments should be deemed to be included in the scope of the claims of the present invention. Therefore, the scope of protection of the present invention should be based on 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) 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. (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 processed stainless steel middle plate; (3) taking another piece of the spare carbon steel ingot, and grinding and cleaning the surface to be composited to obtain a processed carbon steel ingot; (4) placing the surface to be composited of the treated carbon steel ingot upward, and placing the surface to be composited of the treated stainless steel middle plate 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.

2. The method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel according to claim 1, characterized in that: The annealing temperature of the annealing is 650-750° C., the holding time is 7-9 hours, and after the holding is completed, the furnace is cooled to 280-300° C. and then air-cooled to room temperature.

3. 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.

4. 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.

5. 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.

6. 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) and step (3), the particle size of the grinding wheel abrasive used for grinding is 60-100 mesh. After grinding, the roughness of the surfaces to be composited of the stainless steel middle plate and the carbon steel ingot is Ra2.0-4.0μm.

7. The method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel according to claim 1, characterized in that: The vacuum degree of the vacuum chamber is ≤7.5×10 -2 Pa; the electron beam sealing welding is performed by four-side spot welding, the spot welding length is 100-150mm, and the spacing distance is 200-300mm.

8. The method for manufacturing an asymmetric composite billet of ferritic stainless steel and carbon steel according to claim 1, characterized in that: The electron beam gun is offset 1.0-2.0 mm toward the stainless steel side relative to the center of the weld, the welding beam current is 160-240 mA, the welding voltage is 75-85 KV, and the welding speed is 170-220 mm / min.

9. An asymmetric composite billet of ferritic stainless steel and carbon steel, characterized in that: The method is produced by any one of claims 1 to 8.

10. An asymmetric composite 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 9 is rolled.

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