A 650hb grade wear-resistant steel plate and a preparation method thereof

Abstract

The application relates to a 650HB-grade wear-resistant steel plate and a preparation method thereof, and belongs to the metallurgical technical field. The chemical component of the 650HB-grade wear-resistant steel plate is as follows: C: 0.60-0.70%, Si<=0.6%, Mn: 1.5-2.5%, S<=0.005%, P<=0.010%, Cr: 1.5-2.5%, B: 0.0015-0.0035%, Ti: 0.08-0.12%, V: 2.0-3.0%, and the rest is Fe and inevitable impurities; the preparation method comprises a smelting, rolling and heat treatment process. The wear-resistant steel does not need to use valuable alloy elements such as Ni, Mo and Nb, and after the heat treatment process, the microstructure is composed of tempered martensite, the surface Brinell hardness is greater than or equal to 650HBW, the core Brinell hardness is greater than or equal to 630HBW, the impact energy at -40 DEG C is greater than or equal to 30J, and the wear-resistant steel has good comprehensive mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a 650HB grade wear-resistant steel plate and its preparation method. Background Technology

[0002] Wear-resistant materials have a wide range of applications in the mining machinery field. Currently, the main types of wear-resistant materials used in mining machinery both domestically and internationally are high-manganese steel, special ceramics, and low-alloy wear-resistant steel. High-manganese steel is the most widely used, with advantages including good toughness and the ability to be cast. Its disadvantages include difficulty in guaranteeing service life under low to medium stress conditions and its high price. Special ceramic materials offer advantages such as high hardness and light weight, but suffer from poor toughness, difficulty in processing, and high cost. Low-alloy wear-resistant steel, on the other hand, is characterized by low cost and stable performance, and its application in the mining machinery field is continuously expanding. In recent years, with the trend towards larger-scale mining operations and continuous production processes, increasingly higher requirements have been placed on the hardness level and service life of low-alloy wear-resistant steel.

[0003] For low-alloy wear-resistant steels, hardness level is the primary factor determining their wear resistance and even service life. Good toughness and hardness uniformity are also required, placing increasingly higher demands on the development and production processes of wear-resistant steel products. Currently, domestic and international manufacturers are capable of stably producing wear-resistant steels with a hardness of 600HB and below, with a relatively complete range of varieties and thicknesses. However, wear-resistant steels with a higher hardness level of 650HB have not yet achieved mass production and are a blank product in both domestic and international markets. Summary of the Invention

[0004] This invention provides a 650HB grade wear-resistant steel plate and its preparation method, aiming to achieve industrial-scale production of this product and fill the gap in domestic and international markets. Based on the traditional C-Mn-B wear-resistant steel chemical composition system, this invention utilizes a reasonable ratio of C and alloying elements, and achieves a good balance of hardness, strength, and toughness through simple smelting, rolling, and heat treatment processes, while simultaneously reducing production costs and complexity, thus creating conditions for industrial-scale production.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a 650HB grade wear-resistant steel plate, wherein the plate has the following chemical composition by mass percentage: C: 0.60-0.70%, Si≤0.6%, Mn: 1.5-2.5%, S≤0.005%, P≤0.010%, Cr: 1.5-2.5%, B: 0.0015-0.0035%, Ti: 0.08-0.12%, V: 2.0-3.0%, with the remainder being Fe and unavoidable impurities.

[0006] The thickness of the 650HB grade wear-resistant steel plate described in this invention is 10-30mm.

[0007] The microstructure of the 650HB grade wear-resistant steel plate of the present invention consists of tempered martensite, with a surface Brinell hardness ≥650HBW, a core Brinell hardness ≥630HBW, and an impact energy ≥30J at -40℃.

[0008] The 650HB grade wear-resistant steel plate of this invention has a yield strength ≥1800MPa, a tensile strength ≥2000MPa, and an elongation after fracture ≥8%.

[0009] The present invention also provides a method for preparing the above-mentioned 650HB grade wear-resistant steel plate, the method comprising smelting, rolling and heat treatment processes, the specific steps of which are as follows: (1) Smelting process: The first step is alloying: pure iron and alloy elements carbon, manganese, chromium, titanium and vanadium are mixed and melted. When the temperature reaches the range of 1560 to 1600℃, it is held for 55 to 60 minutes. The second step is alloying treatment: When the temperature of the molten steel reaches the range of 1560 to 1600℃ and the holding time reaches the range of 55 to 60 minutes, first put the ferroboron into the ingot mold, then pour the molten steel into the ingot mold and complete the pouring, and then cool to obtain the casting billet with a thickness range of 60 to 80 mm. (2) Rolling process: Heating: After grinding the billet, place it in a heating furnace and heat it to 1100-1150℃, then keep it at that temperature for 1-2 hours; Rolling and cooling: The billet is taken out of the heating furnace, descaled by high pressure water and then rolled. The initial rolling temperature is ≥1050℃, the final rolling temperature is ≥900℃, the cumulative reduction rate of each pass is ≥60%, the thickness of the finished product is 10~30mm, and after rolling, it is naturally cooled to room temperature in the air. (3) Heat treatment process: Quenching: Heat the furnace to 840-860℃, then put the plate into the furnace and close the furnace door. Start timing when the temperature inside the furnace rises back to 840℃ and hold for 20-75 minutes. After holding, take the plate out of the furnace and quench it in oil to cool it to below 50℃, and then temper it. Tempering: Heat the furnace to 160-180℃, then put the quenched plate into the furnace and close the furnace door. Start timing when the temperature inside the furnace rises back to 160℃ and keep it at that temperature for 4-5 hours. After the holding time is completed, take the plate out of the furnace and air cool it to room temperature to obtain 650HB grade wear-resistant steel plate.

[0010] The smelting process described in this invention employs a vacuum medium-frequency induction heating furnace, and the alloy elemental carbon is high-purity graphite powder.

[0011] In the rolling process described in this invention, the heating furnace is protected by a nitrogen atmosphere.

[0012] In the heat treatment process described in this invention, the heat holding time is determined according to the thickness of the plate, at a rate of 2.0~2.5 minutes / mm.

[0013] In the heat treatment process described in this invention, the plate material after quenching and cooling must be tempered within 4 hours.

[0014] The compositional design concept of the 650HB grade wear-resistant steel plate of this invention: Based on the traditional C-Mn-B wear-resistant steel chemical composition system, the C content is increased to ensure the material's hardness and wear resistance. The addition of Cr and V can further improve the material's hardenability, and at the same time, carbide dispersion precipitation is formed during heat treatment, thereby refining the austenite grains and further improving the material's hardness and toughness. The addition of trace amounts of Ti during smelting can fix the N element in the molten steel, thereby increasing the proportion of effective boron and ensuring the stability of the material's hardenability and mechanical properties.

[0015] Specifically as follows: C: Carbon is the most basic element in steel and one of the main factors affecting hardness, strength, and wear resistance. Generally speaking, the higher the carbon content in steel, the higher the hardness and wear resistance after quenching and tempering heat treatment. To ensure that the wear-resistant steel plate achieves a hardness of 650HB, the carbon content must be at least 0.60%; otherwise, the hardness and wear resistance of the wear-resistant steel plate after heat treatment will be insufficient. On the other hand, if the carbon content is too high, exceeding 0.70%, network carbides will appear in the wear-resistant steel plate during the air-cooling process after rolling, increasing the risk of quenching cracking. Therefore, considering the comprehensive influence of carbon on hardness, wear resistance, and quenching cracking, the carbon content in the steel should be controlled within the range of 0.60% to 0.70%.

[0016] Silicon (Si): Silicon is the most basic element in steel and has no particularly direct impact on the hardness and toughness of wear-resistant steel plates. The residual silicon content in steel is usually below 0.6%. Therefore, no special control measures are needed for the silicon content; maintaining it at 0.6% or below is sufficient.

[0017] Mn: Manganese is the most basic element in steel and one of the important alloying elements used in this invention. Manganese can stabilize austenite and reduce the critical quenching rate of steel, thereby improving the hardenability of the material. In this invention, in order to improve hardenability and thus ensure the hardness and wear resistance of the wear-resistant steel plate after heat treatment, the manganese content should be at least 1.5%; however, if the manganese content exceeds 2.5%, it will significantly increase the risk of cracking of the slab during rolling. Therefore, the manganese content should be controlled within the range of 1.5% to 2.5%.

[0018] S: Sulfur is an impurity element in steel. If the sulfur content is too high, it will increase the steel's tendency to become hot-brittle. Therefore, the lower the sulfur content, the better. In actual production, it is generally controlled below 0.005%.

[0019] P: Phosphorus is an impurity element in steel. If the phosphorus content is too high, it will seriously damage the overall mechanical properties of the steel, especially its impact toughness. Therefore, the lower the phosphorus content, the better. In actual production, it is generally controlled below 0.010%.

[0020] Cr: Chromium is one of the important alloying elements used in this invention. Similar to manganese, chromium effectively improves the hardness, strength, and hardenability of steel. Especially when the manganese content is close to the upper limit (2.5%), the addition of chromium can further improve the hardenability of the steel, thereby ensuring its hardness and wear resistance after heat treatment. In this invention, the chromium content must reach at least 1.5% to achieve its beneficial effects; however, if the chromium content exceeds 2.5%, the steel billet will produce difficult-to-eliminate liquid carbides during solidification, which will harm the performance of the wear-resistant steel plate. Therefore, the chromium content should be controlled within the range of 1.5% to 2.5%.

[0021] B: Boron is one of the important alloying elements used in this invention. A small amount of boron (0.0015-0.0035%) can effectively improve hardenability, thereby ensuring the hardness and wear resistance of the wear-resistant steel plate after heat treatment. However, if the boron content is too low (below 0.0015%), it is difficult to improve hardenability; if the content is too high (above 0.0035%), it will significantly increase the material's tendency to hot crack and harm its toughness. Therefore, the boron content should be controlled within the range of 0.0015-0.0035%.

[0022] Ti: Titanium is one of the important alloying elements used in this invention. During smelting, especially before adding boron, adding a trace amount of Ti (0.08–0.12%) to the molten steel can effectively fix the nitrogen element in the steel, thereby increasing the proportion of available boron (acid-soluble boron) and thus more fully utilizing the beneficial effects of boron. If the titanium content is too high, it will increase the number of coarse carbide and nitride inclusions, thus affecting the overall mechanical properties. Therefore, the titanium content should be controlled within the range of 0.08–0.12%.

[0023] V: Vanadium is one of the key alloying elements used in this invention. As a strong carbide-forming element, vanadium, on the one hand, forms and precipitates stable, fine VC particles with C during rolling, thereby refining the grain structure after rolling and inhibiting grain growth during quenching and holding. On the other hand, it can also precipitate fine VC particles during tempering, thus significantly improving the hardness and wear resistance of the material. In this invention, the vanadium content must reach 2.0% or more to ensure the hardness level and wear resistance of the wear-resistant steel plate; however, if the vanadium content is too high and exceeds 3.0%, the billet will produce difficult-to-eliminate liquid carbides during solidification, which will harm the performance of the wear-resistant steel plate. Therefore, the vanadium content should be controlled within the range of 2.0% to 3.0%.

[0024] The design concept of the preparation method of the 650HB grade wear-resistant steel plate of this invention: The vacuum medium-frequency induction heating furnace melting method is adopted to minimize the content of harmful impurities and ensure the purity of molten steel. The controlled rolling method is adopted to refine the grains and ensure the uniformity of the microstructure. The oil quenching + low temperature tempering heat treatment method is adopted to obtain a tempered martensite structure with fine grains and good comprehensive mechanical properties, and to reduce the risk of quenching deformation and cracking.

[0025] Specifically as follows: Smelting: Two alloying processes are performed using a vacuum induction furnace and ingot mold. The first alloying process is carried out in the vacuum induction furnace, using pure iron and alloy elements as raw materials to minimize the content of harmful impurities. Pure iron and alloy elements such as carbon (high-purity graphite powder), manganese, chromium, titanium, and vanadium are mixed and melted. When the temperature reaches the range of 1560-1600℃, it is held for 55-60 minutes to ensure that harmful gaseous elements such as O, N, and H in the molten steel react fully with alloying elements such as Ti and are thoroughly removed in a vacuum environment. The second alloying process is carried out in the ingot mold. Its purpose is to add boron, which is necessary for 650HB grade wear-resistant steel plates. When the temperature of the molten steel reaches the range of 1560-1600℃ and the holding time reaches the range of 55-60 minutes, ferroboron is first placed into the ingot mold, and then the molten steel is poured into the ingot mold to complete the casting. After cooling, a billet with a thickness of 60-80 mm is obtained. The reason for using a smelting method involving two alloying processes is to minimize the reaction between boron and elements such as O and N in the molten steel, thus minimizing burn-off and fully utilizing the purifying effect of alloying elements such as Ti on the molten steel, thereby ensuring the proportion of effective boron (acid-soluble boron).

[0026] Rolling: This process includes heating, rolling, and cooling. Heating follows the conventional pre-rolling heating process for medium-thick plates. After grinding, the billet is placed in a heating furnace with a nitrogen atmosphere and heated to 1100–1150°C. It is then held at this temperature for 1–2 hours to ensure complete austenitization, uniform temperature distribution, and to inhibit oxidation and decarburization of the billet surface. For billets with thicknesses of 60mm, 70mm, and 80mm, the holding times are set to 1 hour, 1.5 hours, and 2 hours, respectively. Rolling follows the principle of controlled rolling with "low temperature and large deformation." The heated billet... After being heated and kept warm, the billet is taken out of the heating furnace and descaled by high-pressure water before rolling. The initial rolling temperature is ≥1050℃ and the final rolling temperature is ≥900℃ to ensure that the material maintains a single-phase austenitic structure throughout the rolling process. At the same time, the cumulative reduction rate of each pass is ≥60%, and the finished product thickness ranges from 10 to 30 mm to ensure the uniformity of grain size during the rolling process. After rolling, the material is cooled to room temperature by air. The microstructure of the material is mainly pearlite, and the Brinell hardness is in the range of 180 to 210 HB.

[0027] Heat treatment involves two steps: quenching and tempering. Quenching is performed using conventional heat treatment furnaces such as muffle furnaces or pit furnaces. First, the furnace temperature is raised to 840–860℃. Then, the sheet metal is placed in the furnace and the door is closed. Once the furnace temperature rises back to 840℃, timing begins, and the temperature is held for 20–75 minutes. The specific holding time is determined based on the sheet thickness, at a rate of 2.0–2.5 minutes per mm. For example, a 10mm thick sheet requires 20–25 minutes of holding time, and a 30mm thick sheet requires 60–75 minutes. If the temperature is below 840℃ or the holding time is too short, the carbides in the steel will not completely dissolve, resulting in insufficient hardness. If the temperature is above 860℃ or the holding time is too long, it can easily cause coarse grains and affect impact toughness. After holding, the sheet metal is removed from the furnace and quenched in oil. After the quenched steel plate is cooled to below 50°C, it must be tempered within 4 hours; otherwise, cracks will form in the plate and affect its impact toughness. Tempering is performed using conventional heat treatment furnaces such as muffle furnaces or pit furnaces. First, the furnace is heated to 160-180°C. Then, the quenched plate is placed in the furnace and the furnace door is closed. Once the furnace temperature rises back to 160°C, the timer is started and the plate is held for 4-5 hours. If the tempering temperature is below 160°C or the holding time is less than 4 hours, the plate will not be tempered sufficiently and it will be difficult to obtain the ideal impact toughness. If the tempering temperature exceeds 180°C or the holding time exceeds 5 hours, it will adversely affect the hardness of the plate. After the holding time is completed, the plate is removed from the furnace and air-cooled to room temperature to obtain 650HB grade wear-resistant steel plate.

[0028] The beneficial effects of adopting the above technical solution are as follows: 1. This invention does not require the use of expensive alloying elements such as Ni, Mo, and Nb. Instead, it utilizes a reasonable ratio of C and alloying elements, along with simple smelting, rolling, and heat treatment processes, to improve the comprehensive mechanical properties and service life of wear-resistant steel materials. Therefore, the manufacturing cost is lower, the preparation process is simpler, the surface and core hardness distribution of the product is uniform, and the quality stability is good. 2. The 650HB grade wear-resistant steel plate prepared by this invention has excellent comprehensive mechanical properties, with a surface Brinell hardness ≥650HBW, a core Brinell hardness ≥630HBW, an impact energy at -40℃ ≥30J, a yield strength ≥1800MPa, a tensile strength ≥2000MPa, and an elongation after fracture ≥8%. In applications with complex working conditions, such as mining machinery, its wear resistance is significantly improved compared to commonly used wear-resistant materials such as cast high-manganese steel and NM500, and its service life can be increased by more than 100%. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to specific embodiments. Example

[0030] In this embodiment, the 650HB grade wear-resistant steel plate has a thickness of 30mm. Its chemical composition and mass percentage are shown in Table 1. Its main use is for wear-resistant parts such as iron ore crusher liners.

[0031] The preparation method of the 650HB grade wear-resistant steel plate in this embodiment includes smelting, rolling and heat treatment processes, and the specific process steps are as follows: (1) Smelting: The first alloying process is carried out in a vacuum medium frequency induction heating furnace. Pure iron and alloy elements carbon (high purity graphite powder), manganese, chromium, titanium and vanadium are mixed and melted. When the temperature reaches 1600℃, it is held for 1 hour. Then the second alloying process is carried out. Boron iron is first put into the ingot mold, then molten steel is poured into the ingot mold and the casting is completed. Then it is cooled to obtain the billet with a thickness of 80mm.

[0032] (2) Rolling: First, the polished billet is placed in a heating furnace with nitrogen atmosphere protection and heated to 1150℃. After holding for 2 hours, the billet is taken out of the heating furnace and subjected to high-pressure water descaling and rolling. The initial rolling temperature is 1090℃, the final rolling temperature is 960℃, the finished product thickness is 30mm, and the cumulative reduction rate is 62.5%. After rolling, it is cooled to room temperature by air cooling.

[0033] (3) Heat treatment: First, heat the furnace to 860°C, then put the plate into the furnace and close the furnace door. When the temperature inside the furnace rises to 840°C, start timing and keep it warm for 60 minutes. Then, take the plate out of the furnace and quench it in oil to cool it to below 50°C. Then, perform tempering treatment. That is, first heat the furnace to 180°C, then put the quenched plate into the furnace and close the furnace door. When the temperature inside the furnace rises to 160°C, start timing and keep it warm for 5 hours. Finally, take the plate out and air cool it to room temperature.

[0034] The main mechanical properties of the 650HB grade wear-resistant steel plate in this embodiment are shown in Table 2. It can be seen that the surface Brinell hardness of the plate reaches more than 650HBW, the core Brinell hardness reaches more than 630HBW, the impact energy at -40℃ reaches more than 30J, the yield strength exceeds 1820MPa, the tensile strength exceeds 2050MPa, and the elongation after fracture reaches more than 9%.

[0035] In this embodiment, the 650HB grade wear-resistant steel plate is used to manufacture iron ore crusher liners, with an average service life of 7 months. Under the same service conditions, iron ore crusher liners made from traditional wear-resistant materials such as NM500 wear-resistant steel and cast high-manganese steel have an average service life of approximately 3 months. Therefore, it can be concluded that the wear resistance of the 650HB grade wear-resistant steel plate in this embodiment is significantly improved compared to traditional materials such as cast high-manganese steel and NM500, and its service life can be increased by more than 100%. Example

[0036] In this embodiment, the 650HB grade wear-resistant steel plate has a thickness of 20mm. Its chemical composition and mass percentage are shown in Table 1. Its main use is as wear-resistant parts such as the outer reinforcing plate of a mining hydraulic bucket.

[0037] The preparation method of the 650HB grade wear-resistant steel plate in this embodiment includes smelting, rolling and heat treatment processes, and the specific process steps are as follows: (1) Smelting: The first step of alloying is carried out in a vacuum medium frequency induction heating furnace. Pure iron and alloy elements carbon (high purity graphite powder), manganese, chromium, titanium and vanadium are mixed and melted. When the temperature reaches 1580℃, it is held for 1 hour. Then the second step of alloying is carried out. Boron iron is first put into the ingot mold, then molten steel is poured into the ingot mold and the casting is completed. Then it is cooled to obtain the billet with a thickness of 70mm.

[0038] (2) Rolling: First, the polished billet is placed in a heating furnace with nitrogen atmosphere protection and heated to 1130℃. After holding for 1.5 hours, the billet is taken out of the heating furnace and subjected to high-pressure water descaling and rolling. The initial rolling temperature is 1070℃, the final rolling temperature is 950℃, the finished product thickness is 20mm, and the cumulative reduction rate is 71.4%. After rolling, it is cooled to room temperature by air cooling.

[0039] (3) Heat treatment: First, heat the furnace to 850°C, then put the plate into the furnace and close the furnace door. When the temperature inside the furnace rises to 840°C, start timing and keep it at that temperature for 40 minutes. Then, take the plate out of the furnace and quench it in oil to cool it to below 50°C. Then, perform tempering treatment. That is, first heat the furnace to 170°C, then put the quenched plate into the furnace and close the furnace door. When the temperature inside the furnace rises to 160°C, start timing and keep it at that temperature for 4 hours. Finally, take the plate out and air cool it to room temperature.

[0040] The main mechanical properties of the 650HB grade wear-resistant steel plate in this embodiment are shown in Table 2. It can be seen that the surface Brinell hardness of the plate reaches more than 650HBW, the core Brinell hardness reaches more than 635HBW, the impact energy at -40℃ reaches more than 30J, the yield strength exceeds 1860MPa, the tensile strength exceeds 2040MPa, and the elongation after fracture reaches 8.5%.

[0041] In this embodiment, 650HB grade wear-resistant steel plates are used to manufacture the outer reinforcing plates of mining hydraulic buckets, with an average service life of 11 months. Under the same service conditions, the outer reinforcing plates of mining hydraulic buckets made of hot-rolled high-manganese steel have an average service life of 5 months. The service life can be increased by more than 2 times. Example

[0042] In this embodiment, the 650HB grade wear-resistant steel plate has a thickness of 10mm. Its chemical composition and mass percentage are shown in Table 1. Its main use is for wear-resistant parts such as mine car body panels.

[0043] The preparation method of the 650HB grade wear-resistant steel plate in this embodiment includes smelting, rolling and heat treatment processes, and the specific process steps are as follows: (1) Smelting: The first alloying process is carried out in a vacuum medium frequency induction heating furnace. Pure iron and alloy elements carbon (high purity graphite powder), manganese, chromium, titanium and vanadium are mixed and melted. When the temperature reaches 1560℃, it is held for 1 hour. Then the second alloying process is carried out. Boron iron is first placed into the ingot mold, and then molten steel is poured into the ingot mold and the casting is completed. Then it is cooled to obtain the billet with a thickness of 60mm.

[0044] (2) Rolling: First, the polished billet is placed in a heating furnace with nitrogen atmosphere protection and heated to 1100℃. After holding for 1 hour, the billet is taken out of the heating furnace and subjected to high-pressure water descaling and rolling. The initial rolling temperature is 1050℃, the final rolling temperature is 900℃, the finished product thickness is 10mm, and the cumulative reduction rate is 83.3%. After rolling, it is cooled to room temperature by air cooling.

[0045] (3) Heat treatment: First, heat the furnace to 840°C, then put the plate into the furnace and close the furnace door. When the temperature inside the furnace rises back to 840°C, start timing and keep it warm for 20 minutes. Then take the plate out of the furnace and quench it in oil to cool it to below 50°C. Then perform tempering treatment. That is, first heat the furnace to 160°C, then put the quenched plate into the furnace and close the furnace door. When the temperature inside the furnace rises back to 160°C, start timing and keep it warm for 4 hours. Finally, take the plate out and air cool it to room temperature.

[0046] The main mechanical properties of the 650HB grade wear-resistant steel plate in this embodiment are shown in Table 2. It can be seen that the Brinell hardness of both the surface and core of the plate reaches above 650HBW, and the impact energy at -40℃ reaches above 30J. The yield strength exceeds 1900MPa, the tensile strength exceeds 2100MPa, and the elongation after fracture reaches above 8%.

[0047] In this embodiment, 650HB grade wear-resistant steel plates are used to manufacture mine car body panels, with an average service life of 9 months; while under the same service conditions, mine car body panels made of NM500 wear-resistant steel have an average service life of 4 months. The service life can be increased by more than 100%. Example

[0048] In this embodiment, the 650HB grade wear-resistant steel plate has a thickness of 15mm. Its chemical composition and mass percentage are shown in Table 1. Its main use is for wear-resistant parts such as guard plates for iron ore conveying equipment.

[0049] The preparation method of the 650HB grade wear-resistant steel plate in this embodiment includes smelting, rolling and heat treatment processes, and the specific process steps are as follows: (1) Smelting: The first alloying process is carried out in a vacuum medium frequency induction heating furnace. Pure iron and alloy elements carbon (high purity graphite powder), manganese, chromium, titanium and vanadium are mixed and melted. When the temperature reaches 1565℃, it is held for 55 minutes. Then the second alloying process is carried out. Boron iron is first put into the ingot mold, then molten steel is poured into the ingot mold and the casting is completed. Then it is cooled to obtain the billet with a thickness of 68mm.

[0050] (2) Rolling: First, the polished billet is placed in a heating furnace with nitrogen atmosphere protection and heated to 1140℃. After holding for 1.5 hours, the billet is taken out of the heating furnace and subjected to high-pressure water descaling and rolling. The initial rolling temperature is 1060℃, the final rolling temperature is 920℃, the finished product thickness is 15mm, and the cumulative reduction rate is 77.9%. After rolling, it is cooled to room temperature by air cooling.

[0051] (3) Heat treatment: First, heat the furnace to 855°C, then put the plate into the furnace and close the furnace door. When the temperature inside the furnace rises to 840°C, start timing and keep it at that temperature for 35 minutes. Then, take the plate out of the furnace and quench it in oil to cool it to below 50°C. Then, perform tempering treatment. That is, first heat the furnace to 170°C, then put the quenched plate into the furnace and close the furnace door. When the temperature inside the furnace rises to 160°C, start timing and keep it at that temperature for 4.5 hours. Finally, take the plate out and air cool it to room temperature.

[0052] The main mechanical properties of the 650HB grade wear-resistant steel plate in this embodiment are shown in Table 2. It can be seen that the Brinell hardness of the surface and core of the plate reaches 650HBW or more, the impact energy at -40℃ reaches 30J or more, the yield strength exceeds 1850MPa, the tensile strength reaches 2030MPa or more, and the elongation after fracture exceeds 8%.

[0053] In this embodiment, 650HB grade wear-resistant steel plates are used to manufacture liners for iron ore conveying equipment, with an average service life of 14 months. Under the same service conditions, liners for iron ore conveying equipment made of NM500 wear-resistant steel have an average service life of 6 months. The service life can be increased by more than 100%. Example

[0054] In this embodiment, the 650HB grade wear-resistant steel plate has a thickness of 25mm. Its chemical composition and mass percentage are shown in Table 1. Its main use is for wear-resistant parts such as bottom plates of mining bar screens.

[0055] The preparation method of the 650HB grade wear-resistant steel plate in this embodiment includes smelting, rolling and heat treatment processes, and the specific process steps are as follows: (1) Smelting: The first alloying process is carried out in a vacuum medium frequency induction heating furnace. Pure iron and alloy elements carbon (high purity graphite powder), manganese, chromium, titanium and vanadium are mixed and melted. When the temperature reaches 1590℃, it is held for 58 minutes. Then the second alloying process is carried out. Boron iron is first put into the ingot mold, then molten steel is poured into the ingot mold and the casting is completed. Then it is cooled to obtain the billet with a thickness of 75mm.

[0056] (2) Rolling: First, the polished billet is placed in a heating furnace with nitrogen atmosphere protection and heated to 1130℃. After holding for 100 minutes, the billet is taken out of the heating furnace and subjected to high-pressure water descaling and rolling. The initial rolling temperature is 1080℃, the final rolling temperature is 980℃, the finished product thickness is 25mm, and the cumulative reduction rate is 66.7%. After rolling, it is cooled to room temperature by air cooling.

[0057] (3) Heat treatment: First, heat the furnace to 845°C, then put the plate into the furnace and close the furnace door. When the temperature inside the furnace rises back to 840°C, start timing and keep it warm for 55 minutes. Then take the plate out of the furnace and quench it in oil to cool it to below 50°C. Then perform tempering treatment. That is, first heat the furnace to 165°C, then put the quenched plate into the furnace and close the furnace door. When the temperature inside the furnace rises back to 160°C, start timing and keep it warm for 4 hours. Finally, take the plate out and air cool it to room temperature.

[0058] The main mechanical properties of the 650HB grade wear-resistant steel plate in this embodiment are shown in Table 2. It can be seen that the surface Brinell hardness of the plate reaches more than 650HBW, the core Brinell hardness reaches more than 630HBW, the impact energy at -40℃ reaches more than 30J, the yield strength exceeds 1800MPa, the tensile strength exceeds 2100MPa, and the elongation after fracture reaches more than 8%.

[0059] In this embodiment, 650HB grade wear-resistant steel plates are used to manufacture mining bar screen bottom plates, with an average service life of 5 months; while under the same service conditions, mining bar screen bottom plates made of hot-rolled high-manganese steel have an average service life of 2 months. The service life can be increased by more than 2 times.

[0060] Table 1. Chemical composition and mass percentage (%) of wear-resistant steel plates in Examples 1-5

[0061] Table 2 Mechanical properties of wear-resistant steel plates in Examples 1-3

[0062] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing 650HB grade wear-resistant steel plate, characterized in that, The preparation method includes smelting, rolling, and heat treatment processes, with the specific steps as follows: (1) Smelting process: The first step is alloying: pure iron and alloy elements carbon, manganese, chromium, titanium and vanadium are mixed and melted. When the temperature reaches the range of 1560 to 1600℃, it is held for 55 to 60 minutes. The second step is alloying treatment: When the temperature of the molten steel reaches the range of 1560 to 1600℃ and the holding time reaches the range of 55 to 60 minutes, first put the ferroboron into the ingot mold, then pour the molten steel into the ingot mold and complete the pouring, and then cool to obtain the casting billet with a thickness range of 60 to 80 mm. (2) Rolling process: Heating: After grinding the billet, place it in a heating furnace and heat it to 1100-1150℃, then keep it at that temperature for 1-2 hours; Rolling and cooling: The billet is taken out of the heating furnace, descaled by high pressure water and then rolled. The initial rolling temperature is ≥1050℃, the final rolling temperature is ≥900℃, the cumulative reduction rate of each pass is ≥60%, the thickness of the finished product is 10~30mm, and after rolling, it is naturally cooled to room temperature in the air. (3) Heat treatment process: Quenching: Heat the furnace to 840-860℃, then put the plate into the furnace and close the furnace door. Start timing when the temperature inside the furnace rises back to 840℃ and hold for 20-75 minutes. After holding, take the plate out of the furnace and quench it in oil to cool it to below 50℃, and then temper it. Tempering: Heat the furnace to 160-180℃, then put the quenched plate into the furnace and close the furnace door. Start timing when the temperature inside the furnace rises back to 160℃ and keep it at that temperature for 4-5 hours. After the holding time is completed, take the plate out of the furnace and air cool it to room temperature to obtain 650HB grade wear-resistant steel plate. The 650HB grade wear-resistant steel plate has the following chemical composition by mass percentage: C: 0.60-0.70%, Si≤0.6%, Mn: 1.5-2.5%, S≤0.005%, P≤0.010%, Cr: 1.5-2.5%, B: 0.0015-0.0035%, Ti: 0.08-0.12%, V: 2.0-3.0%, with the remainder being Fe and unavoidable impurities.

2. The method for preparing a 650HB grade wear-resistant steel plate according to claim 1, characterized in that, The smelting process is carried out in a vacuum medium-frequency induction heating furnace, and the elemental carbon in the alloy is high-purity graphite powder.

3. The method for preparing a 650HB grade wear-resistant steel plate according to claim 1, characterized in that, The rolling process is carried out in a heating furnace with a nitrogen atmosphere for protection.

4. The method for preparing a 650HB grade wear-resistant steel plate according to claim 1 or 2, characterized in that, The heat treatment process involves holding the material for 2.0 to 2.5 minutes per mm, depending on the thickness of the sheet.

5. A method for preparing a 650HB grade wear-resistant steel plate according to claim 1 or 2, characterized in that, In the heat treatment process, the plate material after quenching and cooling must be tempered within 4 hours.

6. A method for preparing a 650HB grade wear-resistant steel plate according to claim 1 or 2, characterized in that, The microstructure of the 650HB grade wear-resistant steel plate consists of tempered martensite, with a surface Brinell hardness ≥650HBW, a core Brinell hardness ≥630HBW, and an impact energy ≥30J at -40℃.

7. A method for preparing a 650HB grade wear-resistant steel plate according to claim 1 or 2, characterized in that, The 650HB grade wear-resistant steel plate has a yield strength ≥1800MPa, a tensile strength ≥2000MPa, and an elongation after fracture ≥8%.

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