High-toughness wear-resistant heterogeneous steel plate and preparation method thereof

Abstract

The application is a kind of high toughness wear-resistant heterogeneous steel plate and its preparation method. It includes the following steps: (1) surface pretreatment of low carbon steel plate; (2) homogenization heat treatment: remove internal stress, get ferrite-pearlite initial organization; (3) electron beam surface heat treatment: place the steel plate in the vacuum chamber, use electron beam surface heating equipment to heat the two surfaces of the steel plate, the steel plate is self-excited cooling quenching, the surface layer of the steel plate is transformed into ferrite-martensite organization, the core is still ferrite-pearlite organization; (4) warm rolling deformation: warm rolling, the ferrite-martensite dual-phase heterogeneous organization of the surface layer is deformed plastically, forming a super-high strength nanocrystalline layer, the core forms a super-fine grain layer, finally obtaining a high toughness wear-resistant heterogeneous steel plate. The process flow of the application is simple, the grain size of the surface hardening layer can be flexibly adjusted by adjusting the surface heat treatment and warm rolling process, different hardness surface layers can be obtained to meet the demand of different wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, specifically relating to a high-strength, tough, wear-resistant heterogeneous steel plate and its preparation method. Background Technology

[0002] As the material foundation of modern society, steel is one of the most widely used materials in the world due to its low price and reliable performance, and is extensively applied in the construction industry, manufacturing industry, and people's daily lives. In engineering machinery, steel is generally used to manufacture the entire machine or important components, such as blades, base plates, and drill rods. These parts usually have high requirements for wear resistance. Alloying is an effective method to improve the wear resistance of steel. By adding a certain amount of alloying elements to the steel, its hardness and strength can be increased, thereby increasing the wear resistance of the steel. However, alloying also has some drawbacks in the manufacturing process. For example, the increased carbon content significantly reduces the weldability of the material. Currently, the wear resistance of low-carbon, low-alloy steels commonly used in industrial production is generally not high, making it difficult to meet the high wear resistance requirements of factories. Therefore, how to obtain high-strength, high-toughness, and wear-resistant steel plates through effective methods is of great significance to the application and development of steel materials.

[0003] Currently, there are many methods to improve the surface hardness and wear resistance of low-carbon steel. Among them, surface nano-sizing is one of the effective methods to improve the wear resistance of low-carbon steel. That is, various physical or chemical methods are used to refine the surface grains of the material to the nanoscale to prepare a surface layer with a nanostructure, while the substrate remains in its original state, thereby improving and enhancing the surface properties of the material, such as fatigue strength, corrosion resistance and wear resistance. Feng Gan et al. (Feng Gan, Shi Lianjie, Lü Jian, et al. Study on surface nano-sizing of low-carbon steel by ultrasonic shot peening [J]. Acta Metallurgica Sinica, 2000, 36(3):300-303.) prepared a surface layer with nanocrystalline structure characteristics on 20 low-carbon steel by ultrasonic shot peening technology. The advantage of this method is that the thickness of the surface nano-layer can be flexibly controlled by adjusting the shot peening process, thereby improving the material properties. However, the limitations of this method are: (1) the impact amplitude cannot be locked and the impact time in the shot peening area is not uniform, making it difficult to obtain a uniform treatment layer; (2) microcracks are easily generated on the sample surface, affecting the overall performance of the material.

[0004] Further research on existing technologies revealed that Bai Haiqiang et al. (Bai Haiqiang, Zhong Lisheng, Kang Ling, et al. Research progress on high-strength and high-toughness coatings for steel surfaces [J]. Surface Technology, 2021, 50(7):97-105.) designed and developed a coating with high strength, high toughness, and high wear resistance, targeting the "inverted relationship" between strength and toughness. This is of great significance for expanding the application of steel materials. They used two or more different components to be superimposed in an alternating manner to prepare a coating material with a micro-nano-scale layered structure. Specifically, micro-nano-scale TiN / TiC ceramic / ceramic layered structure coatings with initial interface layer numbers of 2, 4, 6, and 10 were prepared on the surface of AISI H13 hot working tool steel by chemical vapor deposition. The fracture toughness and hardness of the coating increased with the increase of the number of layers. When the number of layers was 10, the fracture toughness and hardness values ​​were about twice that of the pure TiN ceramic layer. The advantages of this method are: (1) the interlayer interface undergoes moderate delamination under external load, which can promote crack deflection, absorb energy, reduce crack propagation driving force, and improve toughness; (2) the existence of the multi-interface structure restricts the material deformation dominated by the dislocation movement behavior inside the grains, and the strength is improved. The disadvantages of this technology are: (1) the adhesion between the coating and the substrate is difficult to control and it is easy to fall off; (2) the preparation of high-strength and tough coatings basically follows the traditional surface modification technology process, the preparation process is long and the production efficiency is low. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing high-strength, toughness, and wear-resistant heterogeneous steel plates using electron beam surface heat treatment and warm rolling deformation. First, the steel plate undergoes homogenization heat treatment to remove internal stress and obtain an initial ferrite-pearlite microstructure. Then, the steel plate undergoes electron beam surface heat treatment to obtain a ferrite-martensite dual-phase microstructure or a fully martensite microstructure on the surface, while the core remains ferrite-pearlite. Finally, the surface-heat-treated sample is subjected to warm rolling deformation. Due to the significant strength difference between ferrite and martensite, plastic deformation of the surface ferrite-martensite dual-phase heterogeneous microstructure promotes the generation of a large number of geometrically necessary dislocations, fostering dislocation accumulation and thus improving grain refinement efficiency to enhance the surface strength and hardness. Meanwhile, the strength difference between ferrite and pearlite in the core is smaller; after the same rolling deformation, the resulting dislocation density is lower than that of the surface layer, leading to lower grain refinement efficiency, larger grain size, and better toughness, ultimately yielding a high-strength, toughness, and wear-resistant heterogeneous steel plate.

[0006] The technical solution to achieve the objective of this invention is: a method for preparing a high-strength, tough, and wear-resistant heterogeneous steel plate, comprising the following steps:

[0007] Step (1): Pre-treatment of the surface of low-carbon steel plate;

[0008] Step (2): Homogenization heat treatment: Homogenization heat treatment is performed on the pretreated steel plate to remove internal stress and obtain the initial ferrite-pearlite structure;

[0009] Step (3): Electron beam surface heat treatment: The steel plate is placed in a vacuum chamber and heated on both surfaces of the steel plate using an electron beam surface heating device. The steel plate is then subjected to self-excited cooling quenching. The surface layer of the steel plate is transformed into a ferrite-martensite structure, while the core remains a ferrite-pearlite structure.

[0010] Step (4): Warm rolling deformation: The steel plate after surface heat treatment is warm rolled. After the ferrite-martensite dual-phase heterogeneous structure on the surface is plastically deformed, an ultra-high strength nanocrystalline layer is formed, and an ultra-fine crystalline layer is formed in the core, finally obtaining a high strength, toughness and wear-resistant heterogeneous steel plate.

[0011] Furthermore, in step (1), the carbon content of the low-carbon steel ranges from 0.08 to 0.25 wt.%.

[0012] Further, the pretreatment in step (1) is as follows: the original steel plate is wire-cut into steel plates with a length of 50-100mm, a width of 20-50mm, and a thickness of 5-20mm. The surface of the steel plate is polished with sandpaper and acid-washed to remove surface oil and impurities.

[0013] Furthermore, step (2) homogenization heat treatment specifically involves: using argon as a protective atmosphere in a vacuum heat treatment furnace, heating at a temperature of 920-980℃, holding for 60-180 minutes, and cooling with the furnace.

[0014] Furthermore, after the surface heat treatment in step (3), the depth of the surface ferrite-martensite hardened layer is 0.1-1 mm, and the proportion of martensite in the hardened layer is 50%-90%.

[0015] Furthermore, in step (3), the accelerating voltage used for electron beam surface heating is 10-80kV, the beam current is 1-20mA, the electron beam scanning diameter is 2-10mm, the electron gun moving speed is 100-400mm / min, and the surface heating temperature is 700-900℃.

[0016] Further, step (4) specifically involves: placing the sample in a muffle furnace and heating it for 10-30 minutes before warm rolling, with a warm rolling temperature of 100-400℃ and a cumulative rolling amount of 50%-95%.

[0017] A high-strength, tough, and wear-resistant heterogeneous steel plate is prepared using the method described above.

[0018] Furthermore, the depth of the ferrite-martensite hardened layer on the steel plate surface is 0.1-1 mm, the average grain size is 10-200 nm, the average grain size of the core ultrafine grain layer is 0.1-2 μm, the Vickers hardness of the surface nanocrystalline layer is 600-750 HV, and the strength is 1800 MPa-2500 MPa.

[0019] Compared with the prior art, the significant advantages of this invention are:

[0020] 1. This invention utilizes surface heat treatment and warm rolling to obtain a uniform surface hardened layer. The grain size of the surface hardened layer can be flexibly controlled by adjusting the surface heat treatment and warm rolling processes to obtain surface layers with different hardness, meeting the requirements of different wear resistance. The ultra-high strength nanocrystalline layer formed on the surface has higher strength and wear resistance than heat-treated martensite.

[0021] 2. This invention obtains a surface nanocrystalline layer and a core ultrafine crystalline layer by controlling the surface microstructure of the entire steel plate and utilizing the different structural evolution laws of the surface structure and the core structure during the rolling process. The ultrahard surface nanocrystalline layer and the core ultrafine crystalline layer are separated by grain boundaries or phase boundaries, which has better adhesion to the substrate than conventional hard coatings.

[0022] 3. The heterogeneous steel plate prepared by the present invention comprises a surface nanocrystalline hardened layer and a central ultrafine crystalline layer, which can improve the surface strength and wear resistance of the steel plate while maintaining a certain toughness in the core, thereby improving the safety of material use. Attached Figure Description

[0023] Figure 1 Electron beam surface heat treatment system and processing schematic diagram.

[0024] Figure 2 The microstructure distribution of the heterogeneous steel plate obtained after surface heat treatment.

[0025] Figure 3 Schematic diagram of rolling deformation.

[0026] Figure 4 Microstructure of the surface and core of the heterogeneous steel plate obtained after warm rolling deformation: (a) Schematic diagram of the sample after warm rolling; (b) Schematic diagram of the cross-section microstructure of the sample after warm rolling; (c) Transmission electron microscope image of the nanocrystalline structure on the surface; (d) Transmission electron microscope image of the ultrafine ferrite-pearlite structure in the core.

[0027] Figure 5 Mechanical property curves of nanocrystalline surface layer and integral steel plate of heterogeneous steel plate. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings.

[0029] This invention discloses a method for preparing a high-strength, tough, wear-resistant heterogeneous steel plate. The method includes the following steps: (1) Surface pretreatment: A steel plate of a certain size is obtained by wire EDM, and the surface of the steel plate is polished with sandpaper and then acid-washed to remove surface oil and impurities; (2) Homogenization heat treatment: The pretreated steel plate is subjected to homogenization heat treatment to remove internal stress and obtain an initial ferrite-pearlite microstructure; (3) Electron beam surface heat treatment: The two surfaces of the steel plate are heated using an electron beam surface heating device, and the electron gun is scanned along a specific trajectory by a control program. Heat treatment is performed on the sample surface by changing the electron gun moving speed and scanning diameter. When the specified temperature is reached, the electron gun is moved or the heating is stopped, and the steel plate is subjected to self-excited cooling quenching. The surface layer is transformed into ferrite-martensite structure, while the core remains ferrite-pearlite structure. (4) Warm rolling deformation: The steel plate after surface heat treatment is warm rolled. After the ferrite-martensite dual-phase heterogeneous structure on the surface is plastically deformed, an ultra-high strength nanocrystalline layer is formed, and an ultra-fine crystalline layer is formed in the core, finally obtaining a high strength, toughness and wear-resistant heterogeneous steel plate.

[0030] Example 1

[0031] Low-carbon steel plates with a chemical composition of 0.19% C, 1.46% Si, 1.01% Mn, 0.003% P, 0.001% S, and the balance being Fe were selected.

[0032] (1) Surface pretreatment: Low carbon steel plate with dimensions of 50×30×6mm was obtained by wire EDM. The surface of the steel plate was polished with 600# sandpaper and acid-washed to remove oil and impurities from the sample surface.

[0033] (2) Homogenization heat treatment: The pretreated steel plate is subjected to homogenization heat treatment in vacuum heat treatment. The heating temperature is 950℃, and after holding for 1 hour, it is cooled in the furnace to obtain the initial structure of ferrite-pearlite. The protective atmosphere during the heating process is argon.

[0034] (3) Electron beam surface heat treatment: The homogenized heat-treated steel plate is placed in the vacuum chamber of the electron beam heat treatment system. The two surfaces of the steel plate are heated by the electron beam surface heating device. The electron gun movement trajectory is controlled by the computer program to scan and heat the sample. The accelerating voltage used for electron beam surface heating is 50kV, the beam current is 4mA, the electron beam scanning diameter is 5mm, the electron gun movement speed is 240mm / min, and the surface heat treatment temperature is controlled at 760℃. When the electron gun is moved or heating is stopped, the steel plate is subjected to self-excited cooling quenching. The surface layer is transformed into ferrite-martensite structure, while the core remains ferrite-pearlite structure.

[0035] (4) Warm rolling deformation: The steel plate after surface heat treatment is warm rolled at 300℃. Before rolling, the sample is heated in a muffle furnace for 10 minutes. The rolling reduction is 5% each time, and the cumulative rolling amount is 80%. After rolling, the ferrite-martensite dual-phase heterogeneous structure on the surface undergoes plastic deformation to form an ultra-high strength nanocrystalline layer, and an ultra-fine crystalline layer is formed in the core, resulting in a high strength, toughness and wear-resistant heterogeneous steel plate. The strength of the surface nanocrystalline layer reaches more than 2GPa.

[0036] Example 2

[0037] The selected material is a 5mm thick low-carbon steel plate with a chemical composition of C 0.20%, Si 1.37%, Mn 1.94%, P 0.002%, S 0.001%, and the balance being Fe.

[0038] (1) Surface pretreatment: Low carbon steel plate with dimensions of 60×30×5mm was obtained by wire EDM. The surface of the steel plate was polished with 600# sandpaper and acid-washed to remove oil and impurities from the sample surface.

[0039] (2) Homogenization heat treatment: The pretreated steel plate is subjected to homogenization heat treatment in vacuum heat treatment. The protective atmosphere is argon, the heating temperature is 920℃, and after holding for 2 hours, it is cooled in the furnace to obtain the initial structure of ferrite-pearlite.

[0040] (3) Electron beam surface heat treatment: The homogenized heat-treated steel plate is placed in the vacuum chamber of the electron beam heat treatment system. The two surfaces of the steel plate are heated by the electron beam surface heating device. The electron gun movement trajectory is controlled by the computer program to scan and heat the sample. The accelerating voltage used for electron beam surface heating is 50kV, the beam current is 4mA, the electron beam scanning diameter is 5mm, the electron gun movement speed is 250mm / min, and the surface heat treatment temperature is controlled at 800℃. When the electron gun is moved or the heating is stopped, the steel plate is subjected to self-excited cooling quenching. The surface layer is transformed into ferrite-martensite structure, while the core remains ferrite-pearlite structure.

[0041] (4) Warm rolling deformation: The steel plate after surface heat treatment is warm rolled at 350℃. Before rolling, the sample is heated in a muffle furnace for 15 minutes. The rolling reduction is 5% each time, and the cumulative rolling amount is 90%. After rolling, the ferrite-martensite dual-phase heterogeneous structure on the surface undergoes plastic deformation to form an ultra-high strength nanocrystalline layer, and an ultra-fine crystalline layer is formed in the core, resulting in a high strength, toughness and wear-resistant heterogeneous steel plate. The strength of the surface nanocrystalline layer reaches more than 2GPa.

[0042] Example 3

[0043] Commercially available Q235B steel plates with a chemical composition of C 0.16%, Si 0.22%, Mn 0.45%, P 0.004%, S 0.001%, and the balance being Fe were selected.

[0044] (1) Surface pretreatment: The commercial Q235B steel plate with the above chemical composition of C 0.16%, Si 0.22%, Mn 0.45%, P 0.004%, S 0.001% and balance Fe is cut into steel plates with dimensions of 60×30×12mm by electrical discharge wire cutting, and the steel plate is polished with sandpaper and pickled to remove oil and impurities from the surface;

[0045] (2) Homogenization heat treatment: The steel plate after the above pretreatment is subjected to homogenization heat treatment in vacuum heat treatment. The protective atmosphere is argon, the heating temperature is 950℃, and after holding for 1 hour, it is cooled in the furnace to obtain the initial structure of ferrite-pearlite.

[0046] (3) Electron beam surface heat treatment: The homogenized heat-treated steel plate is placed in the vacuum chamber of the electron beam heat treatment system. The two surfaces of the steel plate are heated by the electron beam surface heating device. The electron gun movement trajectory is controlled by the computer program to scan and heat the sample. The accelerating voltage of the electron beam surface heating is 50kV, the beam current is 4mA, the electron beam scanning diameter is 5mm, the electron gun movement speed is 250mm / min, and the surface heat treatment temperature is controlled at 760℃. When the electron gun is moved or the heating is stopped, the steel plate is subjected to self-excited cooling quenching. The surface layer is transformed into ferrite-martensite structure, while the core remains ferrite-pearlite structure.

[0047] (4) Warm rolling deformation: The steel plate after surface heat treatment is warm rolled at 350℃. Before rolling, the sample is heated in a muffle furnace for 15 minutes. The rolling reduction is 5% each time, and the cumulative rolling amount is 85%. After rolling, the ferrite-martensite dual-phase heterogeneous structure on the surface undergoes plastic deformation to form an ultra-high strength nanocrystalline layer, and an ultra-fine crystalline layer is formed in the core, resulting in a high strength, toughness and wear-resistant heterogeneous steel plate.

Claims

1. A method for preparing a high-strength, tough, wear-resistant heterogeneous steel plate, characterized in that, Includes the following steps: Step (1): Pre-treatment of the surface of low-carbon steel plate; Step (2): Homogenization heat treatment: Homogenize the pretreated steel plate to remove internal stress and obtain the initial ferrite-pearlite structure; Step (3): Electron beam surface heat treatment: The steel plate is placed in a vacuum chamber and heated on both surfaces of the steel plate using an electron beam surface heating device. The steel plate is then subjected to self-excited cooling quenching. The surface layer of the steel plate is transformed into ferrite-martensite structure, while the core remains ferrite-pearlite structure. Step (4): Warm rolling deformation: The steel plate after surface heat treatment is warm rolled. After the ferrite-martensite dual-phase heterogeneous structure on the surface is plastically deformed, an ultra-high strength nanocrystalline layer is formed, and an ultra-fine crystalline layer is formed in the core, finally obtaining a high strength, toughness and wear-resistant heterogeneous steel plate. Step (1) The carbon content of the low-carbon steel ranges from 0.08 to 0.25 wt.%; Step (2) Homogenization heat treatment specifically involves: using argon as a protective atmosphere in a vacuum heat treatment furnace, heating at 920-980℃, holding for 60-180 minutes, and cooling with the furnace. Step (3) The accelerating voltage used for electron beam surface heating is 10-80kV, the beam current is 1-20mA, the electron beam scanning diameter is 2-10 mm, the electron gun moving speed is 100-400mm / min, and the surface heating temperature is 700-900℃. Step (4) specifically involves placing the sample in a muffle furnace and heating it for 10-30 minutes before warm rolling. The warm rolling temperature is 100-400℃, and the cumulative rolling amount is 50%-95%.

2. The method according to claim 1, characterized in that, Step (1) Pretreatment specifically involves: wire cutting the original steel plate into steel plates with a length of 50-100 mm, a width of 20-50 mm, and a thickness of 5-20 mm; using sandpaper to polish the surface of the steel plate and pickling to remove surface oil and impurities.

3. The method according to claim 2, characterized in that, After surface heat treatment in step (3), the depth of the surface ferrite-martensite hardened layer is 0.1-1 mm, and the proportion of martensite in the hardened layer is 50%-90%.

4. A high-strength, tough, wear-resistant heterogeneous steel plate, characterized in that, Prepared by the method according to any one of claims 1-3; the depth of the ferrite-martensite hardened layer on the surface of the steel plate is 0.1-1 mm, the average grain size is 10-200 nm, the average grain size of the ultrafine core layer is 0.1-2 μm, the Vickers hardness of the surface nanocrystalline layer is 600-750 HV, and the strength is 1800 MPa-2500 MPa.

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