High wear-resistant martensitic stainless steel and carbon steel symmetrical composite billet and its manufacturing method

Abstract

This invention belongs to the field of composite plate manufacturing technology, specifically relating to a symmetrical composite billet of high wear-resistant martensitic stainless steel and carbon steel and its manufacturing method. The manufacturing method of this invention for a symmetrical composite billet of high wear-resistant martensitic stainless steel and carbon steel includes the following steps in sequence: preparation of billet raw materials, surface treatment of billet raw materials, application of a release agent to the stainless steel plate, drying of the release agent in a heating furnace, cleaning, billet assembly, electron beam sealing welding in a vacuum chamber, and weld inspection of the composite billet. This invention achieves stable symmetrical assembly of stainless steel and carbon steel by optimizing the symmetrical billet structure and customizing the welding process, ensuring that the composite billet does not crack or delaminate during the entire rolling process, ultimately producing a high wear-resistant stainless steel + carbon steel composite plate with a strong interfacial bond.

Description

Technical Field

[0001] This invention belongs to the field of composite plate manufacturing technology, specifically relating to a symmetrical composite billet of high wear-resistant martensitic stainless steel and carbon steel and its manufacturing method. Background Technology

[0002] High wear-resistant stainless steel + carbon steel composite materials possess both characteristics, meeting the hardness requirements of stainless steel while also exhibiting excellent mechanical properties. They are widely used in key components such as rolling mill liners and motor bases, making them a new material with great potential.

[0003] High wear-resistant martensitic stainless steel, used as the wear-resistant layer of composite plates, has extremely poor weldability. If it is directly welded to carbon steel to form a billet and then subjected to asymmetric rolling, it will face many technical challenges: on the one hand, direct welding of dissimilar steels is prone to problems such as weld cracks and low bonding strength, making it difficult to meet weld quality standards; on the other hand, stainless steel and carbon steel have significant differences in material properties, and uneven stress distribution during asymmetric rolling can easily lead to cracking of the composite billet and rolling failure, resulting in unreliable yield and product performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, a symmetrical composite billet of high wear-resistant martensitic stainless steel and carbon steel and its manufacturing method are provided.

[0005] Specifically, the present invention is achieved through the following technical solution: A method for manufacturing a symmetrical composite billet of high wear-resistant martensitic stainless steel and carbon steel includes: (1) Prepare two carbon steel billets as base material and two stainless steel medium plates as cladding material; (2) Milling and grinding the surfaces of carbon steel billets to be laminated, and grinding the surfaces of stainless steel plates to be laminated. (3) Apply MgO-type release agent to the non-grinding surface of the stainless steel medium plate and dry it; (4) Two carbon steel billets are placed on the outside and two stainless steel plates are placed on the inside to form an ABBA symmetrical structure. The contact surfaces of the carbon steel billets and the stainless steel plates are both ground surfaces, and the contact surfaces of the two stainless steel plates are coated with release agent. A plug strip of the same material as the carbon steel billet is set around the stainless steel plates. The height of the plug strip is the sum of the thicknesses of the two stainless steel plates. A gap is left between the stainless steel plates and the plug strip. The outer side of the plug strip is flush with the carbon steel billet. (5) After the billet is assembled, the four sides of the carbon steel billet are spot welded to the plug strip, then a vacuum is drawn, and an electron beam gun is used to seal the weld in the center of the weld. (6) Perform weld inspection on the composite blank after sealing.

[0006] In the above-mentioned method for manufacturing symmetrical composite billets, in step (1), the thickness of the carbon steel base billet is 100-230mm and the flatness is ≤10mm; the thickness of the stainless steel medium plate is 10-67mm and the flatness is ≤5mm; wherein, the thickness ratio of the carbon steel base billet to the stainless steel medium plate is (3-23):1.

[0007] The above-mentioned method for manufacturing symmetrical composite billets includes step (1) further including tempering heat treatment of stainless steel medium plate; wherein the tempering heat treatment temperature is 540-600℃, and after holding for 8-30h, it is air-cooled to room temperature.

[0008] In the above-mentioned method for manufacturing symmetrical composite billets, in step (2), after grinding, the roughness of the surfaces to be composited on the carbon steel billet and the stainless steel plate is Ra2.0-4.0.

[0009] In the above-mentioned method for manufacturing symmetrical composite blanks, in step (3), the MgO content of the MgO-type release agent is 30-50%, and the amount of release agent used is 5-30 g / m. 2 The drying temperature is 350-450℃, and the drying time is 3-5 hours.

[0010] In the above-mentioned method for manufacturing symmetrical composite blanks, in step (4), the width of the plug strip is 35-100mm, the gap between the carbon steel base blank and the plug strip is ≤1mm, and the gap between the stainless steel middle plate and the plug strip is 20-40mm.

[0011] In the above-mentioned method for manufacturing symmetrical composite blanks, in step (5), the length of the spot weld is 40-60 mm, and the interval is 300-500 mm; the vacuum degree of the sealing weld is ≤7.5×10 -2 The welding current is 160-220mA, the welding voltage is 65-85KV, and the welding speed is 120-170mm / min.

[0012] A high wear-resistant martensitic stainless steel and carbon steel symmetrical composite billet is obtained by the above-mentioned manufacturing method of symmetrical composite billet.

[0013] A high wear-resistant martensitic stainless steel and carbon steel composite plate is obtained by hot rolling and splitting the above-mentioned high wear-resistant martensitic stainless steel and carbon steel symmetrical composite billet.

[0014] The aforementioned high wear-resistant martensitic stainless steel and carbon steel composite plate has an interfacial shear strength τ≥250MPa and an interfacial bonding rate of 100%.

[0015] The technical solution of the present invention has the following beneficial effects: (1) This invention innovatively adopts a symmetrical billet assembly structure of "AB + release agent + BA", replacing the traditional direct welding of stainless steel and carbon steel with butt welding of carbon steel. This effectively avoids the inherent defect of poor weldability of high wear-resistant martensitic stainless steel, significantly improves the bonding strength and forming quality of the weld, and reduces the probability of welding defects such as cracks and weld failure. At the same time, this symmetrical billet assembly method makes the composite billet more uniformly stressed during the rolling process, which is conducive to improving the stability of the rolling process and the yield.

[0016] (2) By optimizing the symmetrical billet structure design and using customized welding process, the present invention achieves stable symmetrical billet assembly of stainless steel and carbon steel, which can ensure that the composite billet does not crack or delaminate during the entire hot rolling process, and finally obtains a high wear-resistant stainless steel / carbon steel composite plate with strong interface bonding and excellent performance.

[0017] (3) To address the technical challenge of assembling high-wear-resistant martensitic stainless steel and carbon steel into composite billets, this invention provides a symmetrical composite billet manufacturing method with lower manufacturing costs and stronger operational controllability. This effectively improves the success rate of billet assembly and rolling, enabling the production of composite plate products with stable quality in batches. The composite plate prepared using the method of this invention exhibits an interfacial shear strength τ≥250MPa and an interfacial bonding rate of 100%, demonstrating excellent bonding performance and promising prospects for industrial application. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

[0019] Figure 1 This is a schematic diagram of the structure of the composite blank of the present invention; Symbol explanation: 1 represents carbon steel billet, 2 represents stainless steel medium plate, and 3 represents plug strip. Detailed Implementation

[0020] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms and expressions used below have the meanings commonly understood by those skilled in the art.

[0021] The terms “the,” “the,” “an,” and “a” as used herein do not indicate a limitation on quantity, but rather that at least one of the mentioned objects is present. The terms “preferred,” “more preferred,” etc., refer to embodiments of the invention that may provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of the invention.

[0022] When a range of values ​​is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0023] A method for manufacturing a symmetrical composite billet of high wear-resistant martensitic stainless steel and carbon steel includes: Raw material preparation for billet assembly Prepare two carbon steel billets as the base material and two stainless steel medium plates as the cladding material.

[0024] Among them, carbon steel billet is carbon steel that has been smelted in a converter and refined in a ladle (LF) and then continuously cast into a billet, or modified billet that has been modified by a hot rolling mill.

[0025] In some preferred embodiments, the thickness of the carbon steel billet is 100-230mm. After the carbon steel billets are produced, they are stacked and stored for cooling for no less than 3 days. One cast billet is placed at the bottom, the carbon steel billet for composite billet making is placed in the middle of the stack, and two cast billets are placed at the top to ensure that the flatness of the carbon steel billet for composite billet making is ≤10mm, which is beneficial to subsequent welding assembly.

[0026] Among them, stainless steel medium plates are obtained by rolling stainless steel billets.

[0027] In some preferred embodiments, the stainless steel medium plate used in this invention is obtained by rolling a stainless steel billet with a billet thickness of 200 mm into a thickness of 10-67 mm.

[0028] More preferably, the thickness ratio of the carbon steel billet to the stainless steel medium plate in this invention is (3-23):1.

[0029] In some preferred embodiments, the present invention further performs tempering heat treatment on the stainless steel medium plate; more preferably, the tempering heat treatment temperature is 540-600℃, and the plate is held at that temperature for 8-30 hours and then air-cooled to room temperature.

[0030] This invention utilizes the aforementioned tempering process to soften and homogenize the microstructure of high-wear-resistant martensitic stainless steel, improve internal stress, and prevent cracking. This effectively reduces the cracking rate during subsequent heating and rolling processes, enhancing the composite effect. The tempered stainless steel plate is then pickled and straightened to ensure an unevenness of ≤5mm.

[0031] Surface treatment of raw materials for billet assembly The surface of the carbon steel billet to be composited is milled to remove defects such as iron oxide scale, cracks, and slag inclusions, and to produce a metallic color.

[0032] The surface of the stainless steel medium plate to be laminated is ground to remove the passivation layer and achieve a metallic finish. In some optional embodiments, the surface of the stainless steel medium plate to be laminated is ground using an 80-mesh flap wheel automatic grinding machine. This invention replaces the stainless steel milling process with grinding, improving processing efficiency while effectively suppressing plate deformation during milling, resulting in uniform and rapid surface processing that meets the requirements for blank assembly.

[0033] The carbon steel billet after milling and the stainless steel medium plate after automatic grinding are both ground by manual grinding machine.

[0034] In some preferred embodiments, the surfaces of the carbon steel billet and the stainless steel plate to be laminated are manually ground using a 100-120 mesh grinding wheel to achieve a surface roughness of Ra2.0-4.0μm.

[0035] This invention, through a reasonable surface treatment process, can effectively remove iron oxide scale from the surface and form a surface hardened layer. The hard and brittle hardened layer is conducive to achieving rolling composite and improving the interfacial bonding strength of the composite plate.

[0036] Stainless steel sheet coated with release agent and dried Before assembly, the un-polished surfaces of the two stainless steel medium plates were coated with an MgO-type release agent.

[0037] To ensure that the composite billet can be smoothly separated into two composite plates after hot rolling, in some preferred embodiments, the MgO content of the MgO-type release agent is 30-50%, and the release agent dosage is 5-30 g / m². 2 After applying the release agent, dry it in a heating oven at 350-450℃ for 3-5 hours. Ensure sufficient release agent is applied and select a suitable drying process.

[0038] Cleaning In some preferred embodiments, the surfaces of the stainless steel medium plate and the carbon steel base billet are cleaned before billet assembly.

[0039] Specifically, first use compressed air without moisture to blow away the dust or iron dust on the surface of carbon steel and stainless steel; then use acetone or volatile alkaline cleaning agent to clean the dust particles that cannot be blown away.

[0040] billet assembly Two carbon steel billets are placed on the outer side, and two stainless steel plates are placed on the inner side, forming an ABBA symmetrical structure. The contact surfaces of the carbon steel billets and stainless steel plates are both ground surfaces, while the contact surfaces of the two stainless steel plates are coated with a release agent. A stopper strip of the same material as the carbon steel billets is placed around the perimeter of the stainless steel plates; the height of the stopper strip is the sum of the thicknesses of the two stainless steel plates, and a gap is left between the stainless steel plates and the stopper strip. The outer side of the stopper strip is flush with the carbon steel billet. The structure of the assembled composite billet is shown in [Figure number missing]. Figure 1 , where 1 is a carbon steel billet, 2 is a stainless steel medium plate, and 3 is a plug strip.

[0041] In some preferred embodiments, the width of the plug strip is 35-100mm, the gap between the carbon steel billet and the plug strip is ≤1mm, and the gap between the stainless steel plate and the plug strip is 20-40mm.

[0042] This invention limits the gap between the stainless steel plate and the stopper strip to 20-40mm, which can prevent the stainless steel from laterally squeezing the stopper strip during the stretching process and reduce the risk of weld cracking between the stopper strip and carbon steel.

[0043] welding After the billet is assembled, the four sides of the carbon steel billet are spot-welded to the stopper strip for fixation. Then, a vacuum is drawn, and an electron beam gun is used to seal the weld in the center of the weld.

[0044] This invention combines carbon steel billets and plug strips by spot welding, which can effectively reduce the degree of welding deformation of stainless steel and reduce the generation of microcracks in the weld.

[0045] In some preferred embodiments, the length of the spot weld is 40-60 mm and the interval is 300-500 mm.

[0046] The sealing welding is a vacuum chamber electron beam sealing welding, with the electron beam gun positioned directly in front of the center of the spot weld. This ensures that the weld fusion point is located exactly in the middle of the weld, thereby effectively guaranteeing the weld strength.

[0047] In some preferred embodiments, the sealing vacuum degree is ≤7.5×10 -2 Pa, as the vacuum level increases, the composite effect is enhanced, which is more conducive to slab composite.

[0048] In some preferred embodiments, the welding sequence for sealing is to weld the two long sides first, followed by the two short sides. This effectively reduces stress concentration at the weld joint and improves its reliability. Furthermore, the spot welding between the carbon steel billet and the plug strip provides additional fixation, effectively reducing the degree of welding deformation of the plug strip and minimizing the formation of microcracks in the weld. These combined effects not only improve welding efficiency but also ensure the composite billet maintains effective vacuum at the bonding surface during subsequent heating and rolling processes, enhancing the composite effect.

[0049] During the research process, the inventors of this application discovered that when the heat input for sealing welding is too low, it leads to incomplete penetration and insufficient weld strength; when the heat input is too high, the grains in the heat-affected zone (HAZ) tend to grow, resulting in a decrease in the ductility and toughness of the HAZ. Therefore, it is necessary to specifically control the sealing welding process to ensure weld depth while also enhancing weld strength.

[0050] In some preferred embodiments, the welding current used in the sealing process is 160-220mA. When the current is too low, the heat input is too low and incomplete penetration occurs. When the current is too high, the heat input is too high and the plasticity and toughness of the heat-affected zone of the weld decreases.

[0051] In some preferred embodiments, the sealing process uses a welding voltage of 65-85KV. Too low a voltage will result in insufficient weld penetration, while too high a voltage will result in an excessively wide weld.

[0052] In some preferred embodiments, the sealing process uses a welding speed of 120-170 mm / min. If the welding speed is too fast, it will result in incomplete penetration, and if the welding speed is too slow, it will result in weld depression.

[0053] In practice, the sealing process of the present invention is not only simple to operate, but also has high welding efficiency, and can effectively ensure the quality of sealing of composite billets.

[0054] Composite billet weld inspection Weld inspection is performed on the composite blank after sealing and welding.

[0055] In some preferred embodiments, ultrasonic testing and PT penetrant testing are used to inspect the weld for defects such as cracks and porosity, ensuring that the penetration depth is ≥35mm.

[0056] In practice, the composite billet obtained by the method of the present invention did not crack during subsequent heating and rolling processes, and the prepared composite plate had an interfacial shear strength τ≥250MPa, an interfacial bonding rate of 100%, and good bonding performance.

[0057] Example The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments, unless otherwise specified, are performed according to conventional methods and conditions.

[0058] Example 1 The stainless steel used in this embodiment is high wear-resistant martensitic stainless steel 4Cr13, and the carbon steel used is Q235B. The thickness of the rolled stainless steel cladding layer is 5mm, and the thickness of the carbon steel base layer is 30mm.

[0059] 1. Preparation of raw materials for billet assembly Carbon steel is smelted in a converter and refined in a ladle (LF) before being continuously cast into billets. The thickness of the carbon steel base billet is 200mm. After the carbon steel base billets come off the production line, they are stacked for cooling. One billet is placed at the bottom, and the carbon steel base billet for composite billet making is placed in the middle of the stack. Two billets are placed at the top. The flatness of the carbon steel base billet for composite billet making is 8mm, and it is used as the base material for the composite plate. Stainless steel billets (200mm thick) are rolled into stainless steel medium plates with a thickness of 33mm, which are used as the cladding material for the composite plate. The base and cladding thickness ratio is 6:1.

[0060] 2. Pretreatment of stainless steel medium plates First, the stainless steel medium plate used for the composite panel cladding is tempered, with the heat treatment temperature controlled at 560-600℃ and the holding time controlled at 18-20 hours, followed by air cooling to room temperature. Then, the tempered stainless steel medium plate is straightened to achieve a flatness of 5mm.

[0061] 3. Surface treatment of raw materials for billet assembly ① The carbon steel billet to be laminated is milled on one side to remove surface defects such as iron oxide scale, cracks, and slag inclusions, resulting in a metallic color. ② The stainless steel medium plate to be laminated is ground using an automatic grinding machine to remove the passivation layer, resulting in a metallic color. ③ Both the milled carbon steel billet and the ground stainless steel medium plate to be laminated are manually ground using a 120-grit grinding wheel. The surface roughness of the carbon steel after surface treatment is Ra3.2μm, and the surface roughness of the stainless steel after surface treatment is Ra3μm.

[0062] 4. Apply release agent to stainless steel sheet and dry. Before assembly, a release agent was applied to the un-ground surfaces of the two stainless steel medium plates. The release agent was MgO type (MgO content 30-50%), and the amount of release agent used was 20g / m². 2 After applying the release agent, it is dried in a heating oven at 400℃ for 5 hours, and then air-cooled to room temperature.

[0063] 5. Cleaning The treated carbon steel and stainless steel surfaces are first blown away with compressed air that is free of moisture to remove surface dust or iron dust; then, acetone or a volatile alkaline cleaning agent is used to clean the dust particles that cannot be blown away.

[0064] 6. Assembly First, place a carbon steel billet on the lower layer with the ground surface facing up. Then, flip a stainless steel plate so that the ground surface of the stainless steel is facing down and the side coated with release agent is facing up, and place it in the center of the billet surface. Next, hoist a stainless steel plate with the release agent side facing down and slowly align it with the first stainless steel plate. Place stoppers around the four sides of the stainless steel plate, leaving a 20mm gap between the stainless steel plate and the stoppers. Finally, place another carbon steel billet with the ground surface facing down, aligning it with the four-sided stoppers. The outer side of the stoppers should be flush with the carbon steel billet. The stopper height is 66mm and the stopper width is 50mm. After aligning the billets, the gap between the billet and the stoppers is 0.5mm. Manual spot welding is then performed between the four sides of the carbon steel and the stoppers. The spot weld length is 40-60mm and the spot weld interval is 300-500mm. After assembling, the billets are sent into the vacuum chamber.

[0065] 7. Vacuum chamber electron beam sealing ① Evacuate the vacuum chamber to a vacuum level of 7×10⁻⁶. -2 Pa. ② Spot weld the four sides of the composite blank at intervals of 300mm. ③ Position the electron beam gun directly at the center of the weld. ④ Weld the two long sides first, then the two short sides. ⑤ Use a welding beam current of 190mA, a welding voltage of 80KV, and a welding speed of 150mm / min.

[0066] 8. Inspection of weld seams in composite billets The weld was inspected by ultrasonic testing and PT penetration testing and found to be free of defects such as cracks and porosity, with a penetration depth of 45mm.

[0067] The composite billet showed no cracking during heating and rolling. The interfacial shear strength after hot rolling was 305 MPa, the interfacial bonding rate was 100%, and the bonding performance was good.

[0068] Example 2 The stainless steel used in this embodiment is high wear-resistant martensitic stainless steel 6Cr13, and the carbon steel used is Q355B. The thickness of the rolled stainless steel cladding layer is 3mm, and the thickness of the carbon steel base layer is 14mm.

[0069] 1. Preparation of raw materials for billet assembly Carbon steel is smelted in a converter and refined in a ladle (LF) before being continuously cast into 230mm thick billets. These billets are then rolled to 140mm in a hot rolling mill. After the billets come off the line, they are stacked for cooling. One billet is placed at the bottom of the stack, and carbon steel billets for composite billet making are placed in the middle of the stack. Two billets are placed at the top. The flatness of the carbon steel billets for composite billet making is 10mm, and they are used as the base material for the composite plate. Stainless steel billets (200mm thick) are rolled into stainless steel medium plates with a thickness of 30mm, which are used as the cladding material for the composite plate. The base and cladding thickness ratio is 4.7:1.

[0070] 2. Pretreatment of stainless steel medium plates First, the stainless steel medium plate used for the composite panel cladding is tempered at a temperature of 540-580℃ for 24 hours, followed by air cooling to room temperature. Then, the tempered stainless steel medium plate is straightened to achieve a flatness of 4mm.

[0071] 3. Surface treatment of raw materials for billet assembly ① The carbon steel billet to be laminated is milled on one side to remove surface defects such as iron oxide scale, cracks, and slag inclusions, resulting in a metallic finish. ② The stainless steel to be laminated surface is ground using an automatic grinding machine to remove the passivation layer and achieve a metallic finish. ③ Both the milled carbon steel billet and the ground stainless steel plate to be laminated are manually ground using a 100-grit grinding wheel. The surface roughness of the carbon steel after surface treatment is Ra3.8μm, and the surface roughness of the stainless steel after surface treatment is Ra4μm.

[0072] 4. Apply release agent to stainless steel sheet and dry. Before assembly, a release agent was applied to the un-ground surfaces of the two stainless steel medium plates. The release agent was MgO type (MgO content 30-50%), and the amount of release agent used was 15g / m². 2 After applying the release agent, it is dried in a heating oven at 450℃ for 4 hours, and then air-cooled to room temperature.

[0073] 5. Cleaning First, use compressed air without moisture to blow away the floating dust or iron dust on the treated carbon steel and stainless steel surfaces; then use acetone or a volatile alkaline cleaning agent to clean the dust particles that cannot be blown away.

[0074] 6. Assembly First, place a carbon steel billet on the lower layer with the ground surface facing up. Then, flip a stainless steel plate so that the ground surface of the stainless steel is facing down and the side coated with release agent is facing up, and place it in the center of the billet surface. Next, hoist a stainless steel plate with the release agent side facing down and slowly align it with the first stainless steel plate. Place stoppers around the four sides of the stainless steel plate, leaving a 30mm gap between the stainless steel plate and the stoppers. Finally, place another carbon steel billet with the ground surface facing down, aligning it with the four-sided stoppers. The outer side of the stoppers should be flush with the carbon steel billet. The stopper height and width are 60mm. After aligning the billets, the gap between the billet and the stoppers is 0.5mm. Manual spot welding is then performed between the four sides of the carbon steel and the stoppers. The spot weld length is 40-60mm and the spot weld interval is 300-500mm. After assembling, the billet is sent into the vacuum chamber.

[0075] 7. Vacuum chamber electron beam sealing ① Evacuate the vacuum chamber to a vacuum level of 7.5 × 10⁻⁶. -2 Pa. ② Spot weld the four sides of the composite blank at intervals of 240mm. ③ Position the electron beam gun directly at the center of the weld. ④ Weld the two long sides first, then the two short sides. ⑤ Use a welding beam current of 165mA, a welding voltage of 70KV, and a welding speed of 130mm / min.

[0076] 8. Inspection of weld seams in composite billets After the sealing weld was completed, ultrasonic testing and PT penetration testing were performed to check that the weld had no defects such as cracks or porosity, and the penetration depth was 40mm.

[0077] The composite billet did not crack during subsequent heating and rolling processes. The interfacial shear strength after hot rolling was 310 MPa, the interfacial bonding rate was 100%, and the bonding performance was good.

[0078] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0079] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0080] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for manufacturing a symmetrical composite billet of high wear-resistant martensitic stainless steel and carbon steel, characterized in that, include: (1) Prepare two carbon steel billets as base material and two stainless steel medium plates as cladding material; (2) Milling and grinding the composite surface of the carbon steel billet and grinding the composite surface of the stainless steel medium plate. (3) Apply MgO-type release agent to the non-grinding surface of the stainless steel medium plate and dry it; (4) Two carbon steel billets are placed on the outside and two stainless steel plates are placed on the inside to form an ABBA symmetrical structure. The contact surfaces of the carbon steel billets and the stainless steel plates are both ground surfaces, and the contact surfaces of the two stainless steel plates are coated with release agent. A plug strip of the same material as the carbon steel billet is set around the stainless steel plates. The height of the plug strip is the sum of the thicknesses of the two stainless steel plates. A gap is left between the stainless steel plates and the plug strip. The outer side of the plug strip is flush with the carbon steel billet. (5) After the billet is assembled, the four sides of the carbon steel billet are spot welded to the plug strip, then a vacuum is drawn, and an electron beam gun is used to seal the weld in the center of the weld. (6) Perform weld inspection on the composite blank after sealing.

2. The method for manufacturing a symmetrical composite blank according to claim 1, characterized in that, In step (1), the thickness of the carbon steel billet is 100-230mm and the flatness is ≤10mm; the thickness of the stainless steel medium plate is 10-67mm and the flatness is ≤5mm; the thickness ratio of the carbon steel billet to the stainless steel medium plate is (3-23):

1.

3. The method for manufacturing a symmetrical composite blank according to claim 1, characterized in that, Step (1) also includes tempering heat treatment of the stainless steel plate; wherein the tempering heat treatment temperature is 540-600℃, and the plate is kept at the temperature for 8-30 hours and then air-cooled to room temperature.

4. The method for manufacturing a symmetrical composite blank according to claim 1, characterized in that, In step (2), after grinding, the surface roughness of the carbon steel billet and the stainless steel plate to be laminated is Ra2.0-4.

0.

5. The method for manufacturing a symmetrical composite blank according to claim 1, characterized in that, In step (3), the MgO content of the MgO-type release agent is 30-50%, and the amount of release agent used is 5-30 g / m. 2 The drying temperature is 350-450℃, and the drying time is 3-5 hours.

6. The method for manufacturing a symmetrical composite blank according to claim 1, characterized in that, In step (4), the width of the plug strip is 35-100mm, the gap between the carbon steel billet and the plug strip is ≤1mm, and the gap between the stainless steel plate and the plug strip is 20-40mm.

7. The method for manufacturing a symmetrical composite blank according to claim 1, characterized in that, In step (5), the length of the spot weld is 40-60mm, and the interval is 300-500mm; the vacuum degree of the sealing weld is ≤7.5×10 -2 The welding current is 160-220mA, the welding voltage is 65-85KV, and the welding speed is 120-170mm / min.

8. A symmetrical composite billet of high wear-resistant martensitic stainless steel and carbon steel, characterized in that, The symmetrical composite blank is obtained by the manufacturing method of any one of claims 1 to 7.

9. A high wear-resistant martensitic stainless steel and carbon steel composite plate, characterized in that, The high wear-resistant martensitic stainless steel and carbon steel symmetrical composite billet as described in claim 8 are obtained by hot rolling and splitting.

10. The high wear-resistant martensitic stainless steel and carbon steel composite plate according to claim 9, characterized in that, The composite plate has an interfacial shear strength τ≥250MPa and an interfacial bonding rate of 100%.

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