A microalloyed reinforced bainite wear-resistant steel

Abstract

The invention discloses a microalloyed reinforced bainite wear-resistant steel, belonging to the technical field of bainite wear-resistant steel materials. The microalloyed reinforced bainite wear-resistant steel of the invention comprises the following chemical components in weight percentage: C: 0.2-0.3%, N: 0.01-0.02%, Si: 0.1-0.3%, Mn: 1-3%, Ti: 0.4-0.6%, Mo: 0.1-0.6%, Cr: 0.8-1.0%, Ni: 0.5-0.6%, P<0.03%, S<0.03%, and the balance is Fe and unavoidable impurities. The present invention optimizes the alloy components so that the alloy components interact with each other to promote the types and quantities of nano-scale precipitates and submicron-scale precipitates in bainitic steel, and successively refines the grains, increases the number of dislocations and promotes precipitation through the processes of graded heating and multi-stage water-air alternating quenching, hot rolling and warm rolling, and tempering treatment, while eliminating phase transformation stress and thermal stress to reduce quenching deformation and cracking tendency, thereby improving the comprehensive mechanical properties and wear resistance of micro-alloyed enhanced bainitic wear-resistant steel.

Description

Technical Field

[0001] The invention belongs to the technical field of bainite wear-resistant steel materials, and in particular relates to a micro-alloyed reinforced bainite wear-resistant steel. Background Art

[0002] Wear-resistant steel is widely used in mining, metallurgy, construction, coal, cement, electricity and other industries. It can be used to manufacture wear-resistant parts such as crusher linings, excavator shovel teeth, conveyor linings, concrete mixer mixing arms, etc. However, in such extreme application environments, a large amount of highly wear-resistant steel is still worn out during use every year, causing huge economic losses to society and frequent safety accidents. Therefore, the development of higher performance wear-resistant steel has become a research focus in the field of steel materials in the world.

[0003] Bainitic steel itself has excellent strength and toughness. Optimizing its alloy composition and / or heat treatment process can further improve its performance, making it more adaptable to some extreme wear environments. Chinese invention patent CN202110671265.4 performs microalloying by adding expensive vanadium. But its cost is too high. Chinese invention patent CN202211617522.7 uses niobium and vanadium to alloy and strengthen bainitic steel. While its cost is high, the size of its precipitates is easily coarsened due to the presence of niobium, which will damage the toughness of the material. Therefore, it is crucial to improve the mechanical properties and wear resistance of bainitic steel under extreme conditions while reducing costs. Summary of the invention

[0004] In view of the shortcomings of the above-mentioned prior art, the present invention provides a micro-alloyed reinforced bainitic wear-resistant steel, which optimizes the alloy composition so that the alloy composition interacts with each other to promote the types and quantities of nano-scale precipitates and submicron-scale precipitates in the bainitic steel, and refines the grains, increases the number of dislocations and promotes precipitation through rolling and heat treatment processes, while eliminating phase transformation stress and thermal stress, reducing quenching deformation and cracking tendency, thereby improving the comprehensive mechanical properties and wear resistance of the micro-alloyed reinforced bainitic wear-resistant steel.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a microalloyed reinforced bainite wear-resistant steel, by optimizing the alloy composition and the preparation method, to achieve the purpose of improving the performance of the microalloyed reinforced bainite wear-resistant steel;

[0006] The microalloyed reinforced bainite wear-resistant steel comprises the following chemical components in weight percentage: C: 0.2-0.3%, N: 0.01-0.02%, Si: 0.1-0.3%, Mn: 1-3%, Ti: 0.4-0.6%, Mo: 0.1-0.6%, Cr: 0.8-1.0%, Ni: 0.5-0.6%, P<0.03%, S<0.03%, and the balance is Fe and unavoidable impurities.

[0007] The microalloyed reinforced bainite wear-resistant steel comprises the following steps:

[0008] (1) According to the alloy composition of microalloyed reinforced bainitic wear-resistant steel, the ingredients are prepared, and smelted and cast into bainitic steel ingots;

[0009] (2) heating and keeping the bainite steel ingot warm, then continue heating and keeping warm, and finally air-cooling to 1000-950°C;

[0010] (3) hot rolling the air-cooled steel billet, and then subjecting the hot-rolled steel billet to the first water quenching, the first air cooling, the second water quenching, and the second air cooling to 300-350°C, and then warm rolling, and air cooling the warm-rolled steel billet to room temperature;

[0011] (4) Heat the billet to 300±50℃ and perform tempering treatment for 1h.

[0012] As a preferred embodiment of the present invention, in the step (1), the smelting specifically comprises: heating the iron block to 1450°C ± 50°C, then adding ferrosilicon blocks, ferromanganese blocks, and nitrogen-chromium cast iron, and continuing to heat them to fully melt them. When the temperature is heated to 1500°C ± 50°C, the temperature is maintained, and titanium ingots, molybdenum wires, and nickel wires are continuously added for alloying smelting for 30-50 minutes.

[0013] As a preferred embodiment of the present invention, in step (1), the casting process is controlled within 3 minutes.

[0014] As a preferred embodiment of the present invention, casting is started after impurities are removed, and steel chips are drilled from different positions after the casting is cooled, and chemical composition analysis is performed to control the composition within the alloying control range.

[0015] As a preferred embodiment of the present invention, in the step (2), the bainitic steel ingot is heated to 600±50°C and kept at this temperature for 1 hour, with a heating rate of ≤75°C / h.

[0016] As a preferred embodiment of the present invention, in the step (2), the bainitic steel ingot is further heated to 1100±50°C and kept at this temperature for 1 hour, with a heating rate of ≤75°C / h.

[0017] As a preferred embodiment of the present invention, in step (3), the temperature of the first water quenching is reduced to 800±50°C, and then a first air cooling is performed for 10-20 minutes; the temperature of the second water quenching is reduced to 500±50°C, and then a second air cooling is performed to 300-350°C.

[0018] As a preferred embodiment of the present invention, in the step (3), the temperature of water during water quenching is ≤35°C, the volume of water is ≥8L, and the cooling time in water is no more than 1 hour.

[0019] As a preferred embodiment of the present invention, in the step (3), the starting temperature of hot rolling is 1100°C to 950°C, the total deformation of hot rolling is 75-85%, and the final rolling temperature is ≥850°C.

[0020] As a preferred embodiment of the present invention, in the step (3), the starting temperature of warm rolling is 350°C to 300°C, the total deformation of warm rolling is 20% to 40%, and the final rolling temperature is ≥250°C.

[0021] In a preferred embodiment of the present invention, in step (4), the heating rate is 140°C to 150°C / h.

[0022] Principle of the invention: First, the invention uses cheap Ti, N, and C as the main precipitation elements, wherein N is used to promote the precipitation of nano-scale and submicron-scale precipitates, and promotes the transformation of solid solution titanium into precipitated titanium, so that a large amount of Ti (C, N) can be precipitated, and the formed carbonitride particles can also effectively hinder the growth of grains and play a role in refining grains. Mo combines with free carbon in steel to form hexagonal lattice MoC or / and Mo 2 C-type carbide, combined with nitrogen in steel, can form a face-centered cubic lattice structure of Mo 2 N and MoN with hexagonal lattice structure; at the same time, Mo segregates at the interface between Ti(C,N) phase and matrix, reducing the interface energy, which can greatly improve the anti-coarsening ability of Ti(C,N) and further refine the size of precipitates. Ni can adjust Ti(C,N), MoC, Mo 2 C.Mo 2 The addition of Mn can promote the stability of austenite and increase the toughness of the material, while Cr can increase the strength of the material through solid solution strengthening.

[0023] Second, the present invention combines the optimization of alloy composition with the preparation process of microalloying enhanced bainitic wear-resistant steel. The present invention first adopts a graded heating method to make the heating rate inside and outside the steel consistent, avoid the internal stress cracking of the steel due to excessive temperature gradient inside and outside, and make the material more fully austenitized. In addition, the ingot is kept warm at high temperature, and the titanium and molybdenum elements in the solid solution are combined with nitrogen and carbon elements to transform into titanium and molybdenum in the precipitated state to play the role of second phase strengthening, and at the same time promote the homogenization of alloy elements. Secondly, hot rolling and warm rolling cooperate with each other to increase the dislocation density in bainitic steel, refine the grains of austenite structure, and induce the precipitation of a large number of Ti (C, N), MoC, MoN particles and crush large-sized precipitates, greatly improving the hardness and deformation resistance of the steel matrix and reducing the damage of large-sized precipitates to the toughness of the material. Rapid cooling after warm rolling is mainly to prevent the occurrence of other phase changes. Finally, a multi-stage water-air alternating treatment method is used to effectively reduce phase transformation stress and thermal stress, reduce quenching deformation and cracking tendency. At the same time, tempering treatment allows more small-sized precipitates to precipitate in the steel matrix to further increase the strength of the material, eliminate the residual internal stress in bainitic steel, and improve the stability of the organization.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: on the one hand, the present invention promotes the types and quantities of nano-scale precipitates and submicron-scale precipitates in bainitic steel through the interaction of alloying elements such as Ti, N, C, Mo, and Ni, and improves the mechanical properties and wear resistance of micro-alloyed enhanced bainitic wear-resistant steel. On the other hand, according to the optimization of the preparation process of the alloying elements, the heat treatment process of graded heating and multi-stage water-air alternating quenching is sequentially performed to keep the bainitic steel as hot as possible inside and outside during the heat treatment process, so as to obtain a more uniform and stable organization and performance, and then the hot rolling and warm rolling are mutually coordinated to refine the grains, increase a large number of dislocations, and promote the precipitation of second-phase particles. Finally, through a long-term tempering treatment, more small-sized precipitates are distributed in the steel matrix, and the hardness and deformation resistance of the matrix are greatly improved through the second phase strengthening gain, so as to achieve the purpose of improving the impact abrasive wear resistance of micro-alloyed enhanced bainitic wear-resistant steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a process flow chart of the preparation of the microalloyed reinforced bainite wear-resistant steel of the present invention.

[0026] Figure 2 This is the distribution diagram of the precipitates of the microalloyed reinforced bainitic wear-resistant steel described in Example 1 on the matrix.

[0027] Figure 3 This is the wear diagram of the microalloyed reinforced bainitic wear-resistant steel described in Example 1. DETAILED DESCRIPTION

[0028] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. Example 1

[0029] The microalloyed reinforced bainite wear-resistant steel contains the following components in mass percentage: C: 0.2%, N: 0.015%, Si: 0.25%, Mn: 1.8%, Ti: 0.5%, Mo: 0.45%, Cr: 0.85%, Ni: 0.5%, P<0.03%, S<0.03%, and the balance is Fe and unavoidable impurities.

[0030] A method for preparing microalloyed reinforced bainite wear-resistant steel comprises the following steps:

[0031] (1) The ingredients are prepared according to the composition of microalloyed reinforced bainitic wear-resistant steel, and then the iron block is placed in a crucible in a vacuum melting furnace and heated to 1450°C. Ferrosilicon blocks, ferromanganese blocks, and nitrogen-chromium cast iron are added to the furnace and the temperature is continued to be raised to fully melt. When the temperature is heated to 1500°C, the temperature is maintained and titanium ingots, molybdenum wires, and nickel wires are continued to be added to the furnace for alloying smelting. The smelting is continued for 40 minutes. After removing impurities, casting is started. The casting process is controlled within 3 minutes. When the casting is cooled, steel chips are drilled from different positions, and then chemical composition analysis is performed to control the composition within the alloying control range.

[0032] (2) The bainitic steel ingot was cut into rectangular blocks of 200 mm × 30 mm × 30 mm. The rectangular blocks were first heated to 600 °C at a heating rate of 75 °C / h and kept at this temperature for 1 hour. Then, the rectangular blocks were heated to 1150 °C at a heating rate of 75 °C / h and kept at this temperature for 1 hour. The samples were taken out and air-cooled to 1000 °C for hot rolling. The starting rolling temperature was 965 °C, the final rolling temperature was 850 °C, and the total hot rolling deformation was 75%. The hot-rolled billet was placed in an 8L 30 °C water cooling pool for water quenching, and the billet surface temperature was monitored. When the billet temperature dropped to 800 °C, the billet was taken out and air-cooled for 15 min, and then quenched in an 8L 30 °C water cooling pool again. When the temperature dropped to 500 °C, the billet was taken out and air-cooled to 350 °C for warm rolling. The starting rolling temperature was 325 °C, the final rolling temperature was 250 °C, and the total hot rolling deformation was 25%. After warm rolling, the billet was air-cooled to room temperature, and finally heated to 300°C at a heating rate of 150°C / h for 1h tempering to relieve stress and precipitate more precipitates. Samples were then taken for microstructural characterization and performance testing. The results are shown in Tables 1 and 2. Example 2

[0033] The microalloyed reinforced bainitic wear-resistant steel contains the following components in mass percentage: C: 0.2%, N: 0.02%, Si: 0.25%, Mn: 1.8%, Ti: 0.6%, Mo: 0.45%, Cr: 0.85%, Ni: 0.5%, P<0.03%, S<0.03%, and the balance is Fe and inevitable impurities.

[0034] A method for preparing microalloyed reinforced bainite wear-resistant steel comprises the following steps:

[0035] (1) The ingredients are prepared according to the composition of microalloyed reinforced bainitic wear-resistant steel, and then the iron block is placed in a crucible in a vacuum melting furnace and heated to 1450°C. Ferrosilicon blocks, ferromanganese blocks, and nitrogen-chromium cast iron are added to the furnace and the temperature is continued to be raised to fully melt. When the temperature is heated to 1500°C, the temperature is maintained and titanium ingots, molybdenum wires, and nickel wires are continued to be added to the furnace for alloying smelting. The smelting is continued for 40 minutes. After removing impurities, casting is started. The casting process is controlled within 3 minutes. When the casting is cooled, steel chips are drilled from different positions, and then chemical composition analysis is performed to control the composition within the alloying control range.

[0036] (2) The bainite steel ingot was cut into rectangular blocks of 200 mm × 30 mm × 30 mm. The rectangular blocks were first heated to 600°C at a heating rate of 70°C / h and kept at this temperature for 1 hour. Then, the rectangular blocks were heated to 1150°C at a heating rate of 70°C / h and kept at this temperature for 1 hour. The samples were taken out and air-cooled to 1000°C for hot rolling. The starting rolling temperature was 965°C, the final rolling temperature was 850°C, and the total hot rolling deformation was 75%. The hot-rolled billet was placed in an 8L 30°C water cooling pool for water quenching. The billet surface temperature was monitored. When the billet temperature dropped to 800°C, the billet was taken out and air-cooled for 15 minutes, and then quenched again in an 8L 30°C water cooling pool. When the temperature dropped to 500°C, the billet was taken out and air-cooled to 350°C for warm rolling. The starting rolling temperature was 325°C, the final rolling temperature was 250°C, and the total hot rolling deformation was 25%. After warm rolling, the billet was air-cooled to room temperature, and finally heated to 300°C at a heating rate of 150°C / h for 1h tempering to relieve stress and precipitate more precipitates. Samples were then taken for microstructural characterization and performance testing. The results are shown in Tables 1 and 2. Example 3

[0037] The microalloyed reinforced bainitic wear-resistant steel contains the following components in mass percentage: C: 0.3%, N: 0.01%, Si: 0.3%, Mn: 3%, Ti: 0.4%, Mo: 0.1%, Cr: 0.8%, Ni: 0.6%, P<0.03%, S<0.03%, and the balance is Fe and inevitable impurities.

[0038] A method for preparing microalloyed reinforced bainite wear-resistant steel comprises the following steps:

[0039] (1) The ingredients are prepared according to the composition of microalloyed reinforced bainitic wear-resistant steel, and then the iron block is placed in a crucible in a vacuum melting furnace and heated to 1400°C. Ferrosilicon blocks, ferromanganese blocks, and nitrogen-chromium cast iron are added to the furnace and the temperature is continued to be raised to fully melt. When the temperature is heated to 1550°C, the temperature is maintained and titanium ingots, molybdenum wires, and nickel wires are continued to be added to the furnace for alloying smelting. The smelting is continued for 30 minutes. After removing impurities, casting is started. The casting process is controlled within 3 minutes. When the casting is cooled, steel chips are drilled from different positions, and then chemical composition analysis is performed to control the composition within the alloying control range.

[0040] (2) The bainite steel ingot was cut into rectangular blocks of 200 mm × 30 mm × 30 mm. The rectangular blocks were first heated to 550°C at a heating rate of 50°C / h and kept at this temperature for 1 hour. Then, the rectangular blocks were heated to 1050°C at a heating rate of 50°C / h and kept at this temperature for 1 hour. The samples were taken out and air-cooled to 950°C for hot rolling. The starting rolling temperature was 950°C, the final rolling temperature was 900°C, and the total hot rolling deformation was 85%. The hot-rolled billet was placed in a 10L 20°C water cooling pool for water quenching. The billet surface temperature was monitored. When the billet temperature dropped to 850°C, the billet was taken out and air-cooled for 10 minutes, and then water-quenched again in an 8L 20°C water cooling pool. When the temperature dropped to 450°C, the billet was taken out and air-cooled to 300°C for warm rolling. The starting rolling temperature was 300°C, the final rolling temperature was 260°C, and the total hot rolling deformation was 40%. After warm rolling, the billet was air-cooled to room temperature, and finally heated to 350°C at a heating rate of 150°C / h for 1h tempering to relieve stress and precipitate more precipitates. Samples were then taken for microstructural characterization and performance testing. The results are shown in Tables 1 and 2. Example 4

[0041] The microalloyed reinforced bainitic wear-resistant steel contains the following components in mass percentage: C: 0.2%, N: 0.015%, Si: 0.1%, Mn: 1%, Ti: 0.45%, Mo: 0.3%, Cr: 0.9%, Ni: 0.55%, P<0.03%, S<0.03%, and the balance is Fe and inevitable impurities.

[0042] A method for preparing microalloyed reinforced bainite wear-resistant steel comprises the following steps:

[0043] (1) The ingredients are prepared according to the composition of microalloyed reinforced bainitic wear-resistant steel, and then the iron block is placed in a crucible in a vacuum melting furnace and heated to 1500°C. Ferrosilicon blocks, ferromanganese blocks, and nitrogen-chromium cast iron are added to the furnace and the temperature is continued to be raised to fully melt. When the temperature is heated to 1550°C, the temperature is maintained and titanium ingots, molybdenum wires, and nickel wires are continued to be added to the furnace for alloying smelting. The smelting is continued for 50 minutes. After removing impurities, casting is started. The casting process is controlled within 3 minutes. When the casting is cooled, steel chips are drilled from different positions, and then chemical composition analysis is performed to control the composition within the alloying control range.

[0044] (2) The bainite steel ingot was cut into rectangular blocks of 200 mm × 30 mm × 30 mm. The rectangular blocks were first heated to 650°C at a heating rate of 70°C / h and kept at this temperature for 1 hour. Then, the rectangular blocks were heated to 1150°C at a heating rate of 60°C / h and kept at this temperature for 1 hour. The samples were taken out and air-cooled to 1100°C for hot rolling. The starting rolling temperature was 1100°C, the final rolling temperature was 950°C, and the total hot rolling deformation was 75%. The hot-rolled billet was placed in a 10L 20°C water cooling pool for water quenching. The billet surface temperature was monitored. When the billet temperature dropped to 750°C, the billet was taken out and air-cooled for 20 minutes, and then quenched again in an 8L 20°C water cooling pool. When the temperature dropped to 550°C, the billet was taken out and air-cooled to 350°C for warm rolling. The starting rolling temperature was 350°C, the final rolling temperature was 280°C, and the total hot rolling deformation was 20%. After warm rolling, the billet was air-cooled to room temperature, and finally heated to 250°C at a heating rate of 140°C / h for 1h tempering to relieve stress and precipitate more precipitates. Samples were then taken for microstructural characterization and performance testing. The results are shown in Tables 1 and 2.

[0045] Comparative Example 1

[0046] The microalloyed reinforced bainite wear-resistant steel contains the following components in mass percentage: C: 0.2%, Si: 0.25%, Mn: 1.8%, Ti: 0.5%, Mo: 0.45%, Cr: 0.85%, Ni: 0.5%, P<0.03%, S<0.03%, and the balance is Fe and inevitable impurities.

[0047] The preparation method of a microalloyed reinforced bainite wear-resistant steel is the same as that in Example 1. The results are shown in Tables 1 and 2.

[0048] Comparative Example 2

[0049] The microalloyed reinforced bainitic wear-resistant steel contains the following components in mass percentage: C: 0.2%, N: 0.015%, Si: 0.25%, Mn: 1.8%, Ti: 0.5%, Cr: 0.85%, Ni: 0.5%, P<0.03%, S<0.03%, and the balance is Fe and inevitable impurities.

[0050] The preparation method of a microalloyed reinforced bainite wear-resistant steel is the same as that in Example 1. The results are shown in Tables 1 and 2.

[0051] Comparative Example 3

[0052] The microalloyed reinforced bainitic wear-resistant steel contains the following components in mass percentage: C: 0.2%, N: 0.003%, Si: 0.25%, Mn: 1.8%, Ti: 0.5%, Mo: 0.45%, Cr: 0.85%, Ni: 0.5%, P<0.03%, S<0.03%, and the balance is Fe and inevitable impurities.

[0053] The preparation method of a microalloyed reinforced bainite wear-resistant steel is the same as that in Example 1. The results are shown in Tables 1 and 2.

[0054] Comparative Example 4

[0055] The microalloyed reinforced bainitic wear-resistant steel contains the following components in mass percentage: C: 0.2%, N: 0.015%, Si: 0.25%, Mn: 1.8%, Ti: 0.5%, Mo: 0.45%, Cr: 0.85%, Ni: 0.5%, P<0.03%, S<0.03%, and the balance is Fe and inevitable impurities.

[0056] A method for preparing microalloyed reinforced bainite wear-resistant steel comprises the following steps:

[0057] (1) The ingredients are prepared according to the composition of microalloyed reinforced bainitic wear-resistant steel, and then the iron block is placed in a crucible in a vacuum melting furnace and heated to 1450°C. Ferrosilicon blocks, ferromanganese blocks, and nitrogen-chromium cast iron are added to the furnace and the temperature is continued to be raised to fully melt. When the temperature is heated to 1500°C, the temperature is maintained and titanium ingots, molybdenum wires, and nickel wires are continued to be added to the furnace for alloying smelting. The smelting is continued for 40 minutes. After removing impurities, casting is started. The casting process is controlled within 3 minutes. When the casting is cooled, steel chips are drilled from different positions, and then chemical composition analysis is performed to control the composition within the alloying control range.

[0058] (2) The bainitic steel ingot was cut into rectangular blocks of 200 mm × 30 mm × 30 mm. The rectangular blocks were first heated to 600 °C at a heating rate of 75 °C / h and kept warm for 1 hour. Then, they were heated to 1150 °C at a heating rate of 75 °C / h and kept warm for 1 hour. The samples were placed in an 8L 30 °C water cooling pool for water quenching to 300 °C and then air-cooled to room temperature. Finally, the billet was heated to 300 °C at a heating rate of 150 °C / h for 1 hour for tempering treatment to relieve stress and precipitate more precipitates. Then, samples were taken for microstructure characterization and performance testing. The results are shown in Tables 1 and 2.

[0059] Comparative Example 5

[0060] The microalloyed reinforced bainitic wear-resistant steel contains the following components in mass percentage: C: 0.2%, N: 0.015%, Si: 0.25%, Mn: 1.8%, Ti: 0.5%, Mo: 0.45%, Cr: 0.85%, Ni: 0.5%, P<0.03%, S<0.03%, and the balance is Fe and inevitable impurities.

[0061] A method for preparing microalloyed reinforced bainite wear-resistant steel comprises the following steps:

[0062] (1) The ingredients are prepared according to the composition of microalloyed reinforced bainitic wear-resistant steel, and then the iron block is placed in a crucible in a vacuum melting furnace and heated to 1450°C. Ferrosilicon blocks, ferromanganese blocks, and nitrogen-chromium cast iron are added to the furnace and the temperature is continued to be raised to fully melt. When the temperature is heated to 1500°C, the temperature is maintained and titanium ingots, molybdenum wires, and nickel wires are continued to be added to the furnace for alloying smelting. The smelting is continued for 40 minutes. After removing impurities, casting is started. The casting process is controlled within 3 minutes. When the casting is cooled, steel chips are drilled from different positions, and then chemical composition analysis is performed to control the composition within the alloying control range.

[0063] (2) The bainitic steel ingot was cut into rectangular blocks of 200 mm × 30 mm × 30 mm. The rectangular blocks were first heated to 600 °C at a heating rate of 75 °C / h and kept at this temperature for 1 hour. Then, the rectangular blocks were heated to 1150 °C at a heating rate of 75 °C / h and kept at this temperature for 1 hour. After that, the samples were taken out and air-cooled to 1000 °C for hot rolling. The starting rolling temperature was 965 °C, the final rolling temperature was 850 °C, and the total hot rolling deformation was 75%. Then, warm rolling was carried out. The starting rolling temperature was 850 °C, the final rolling temperature was 750 °C, and the total hot rolling deformation was 25%. The warm rolled billet was placed in an 8L 30°C water cooling pool for water quenching, and the billet surface temperature was monitored. When the billet temperature dropped to 650°C, the billet was taken out and air cooled for 15 minutes, and then water quenched again in an 8L 30°C water cooling pool. When the temperature dropped to 400°C, the billet was taken out and air cooled to room temperature. Finally, the billet was heated to 300°C at a heating rate of 150°C / h for 1h tempering treatment to relieve stress and precipitate more precipitates. Samples were then taken for microstructure characterization and performance testing. The results are shown in Tables 1 and 2.

[0064] Table 1

[0065]

[0066] According to Examples 1-4 and Comparative Examples 1-5, the microalloyed reinforced bainite wear-resistant steel prepared in Examples 1-4 has better yield strength, tensile strength, elongation, hardness and impact toughness properties.

[0067] According to Example 1 and Comparative Examples 1-2, since some of the precipitated elements are lost in Comparative Examples 1-2, the material matrix lacks sufficient support of the second phase and thus its strength and hardness are significantly reduced.

[0068] According to Example 1 and Comparative Example 3, the obvious decrease in N content means that there is not enough N inside the material to promote precipitation and refine the size of precipitates, which reduces the number of precipitates and significantly increases the size of precipitates, which will lead to a certain decrease in the strength and toughness of microalloyed precipitates to enhance bainitic steel. In the actual production process, the preparation conditions of steel with a higher N content are harsh, and at the same time, too much N content is very unfavorable to the performance of the material. Excessive nitrogen can easily cause the steel to produce aging brittleness and easy brittle cracking during processing. When N is added to a higher amount, the steel cannot dissolve so much nitrogen inside, and the excess N will overflow, which will make the macroscopic structure of the steel loose and the material performance greatly reduced.

[0069] According to Example 1 and Comparative Example 4, it can be seen that Comparative Example 4 did not perform optimized heat treatment and rolling treatment, and the faster cooling rate resulted in insufficient bainite transformation, and the internal stress in the material could not be released in time. Due to the lack of hot rolling and warm rolling, the grain size of the structure was not refined, and the precipitates could not induce precipitation through deformation, nor could more dislocations be generated, so its strength and toughness were significantly reduced.

[0070] According to Example 1 and Comparative Example 5, although continuous hot rolling and warm rolling refine the grains of the material and increase the dislocations inside the material, a large internal stress is generated inside the material, and the subsequent direct water quenching treatment makes it impossible to release this part of the internal stress in time. Even if stress relief tempering treatment is performed later, the toughness of the material is still poor. There are many micro-alloyed enhanced bainite wear-resistant steels described in the embodiments.

[0071] Test example

[0072] This test example is to verify the wear resistance of the microalloyed reinforced bainite wear-resistant steel prepared in the examples and comparative examples.

[0073] Experimental method: The microalloyed reinforced bainitic wear-resistant steels prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to impact abrasive wear tests under the same environment, with an impact energy of 2.5 J, an abrasive particle size of 40-70 mesh, and an impact time of 5 hours. Impact wear specimens were prepared by wire cutting, and the sample size was 10 mm × 10 mm × 30 mm. The wear weight loss per hour, the total wear weight loss, the thickness of the work-hardened layer, and the hardest Brinell hardness of the work-hardened layer are shown in Table 2.

[0074] Table 2

[0075]

[0076] It can be seen that the wear resistance of Comparative Example 1-2, which has lost some of the precipitated elements, is significantly reduced compared to Examples 1-4. This is because there are not enough second-phase particles to support the matrix and resist abrasive embedding, which makes it easier to be worn away. With the same alloy composition, the wear resistance of Comparative Example 4, which has not undergone optimized heat treatment and rolling, is also lower than that of Examples 1-2, which have undergone optimized heat treatment and rolling. Hot rolling and warm rolling cooperate with each other to refine the grains, increase a large number of dislocations, and promote the precipitation of second-phase particles, so that the strength of the material is significantly increased, and it has a better ability to resist abrasive wear.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A microalloyed reinforced bainite wear-resistant steel, It is characterized in that By optimizing the alloy composition and preparation method, the purpose of improving the performance of microalloyed reinforced bainite wear-resistant steel is achieved; The microalloyed reinforced bainite wear-resistant steel comprises the following chemical components in weight percentage: C: 0.2-0.3%, N: 0.01-0.02%, Si: 0.1-0.3%, Mn: 1-3%, Ti: 0.4-0.6%, Mo: 0.1-0.6%, Cr: 0.8-1.0%, Ni: 0.5-0.6%, P<0.03%, S<0.03%, and the balance is Fe and unavoidable impurities; The preparation method comprises the following steps: (1) preparing materials according to the alloy composition of the microalloyed reinforced bainitic wear-resistant steel, and melting and casting the steel into a bainitic steel ingot; (2) heating and keeping the bainite steel ingot warm, then continuing to heat and keep warm, and finally air cooling to 1000-950°C; (3) hot rolling the air-cooled steel billet, the starting rolling temperature of hot rolling is 1100°C to 950°C, the final rolling temperature is ≥850°C, the hot-rolled steel billet is subjected to the first water quenching to 800±50°C, and then subjected to the first air cooling for 10-20min, and then subjected to the second water quenching to 500±50°C, and then subjected to the second air cooling to 300-350°C for warm rolling, the starting rolling temperature of warm rolling is 350°C to 300°C, the final rolling temperature is ≥250°C, and the warm-rolled steel billet is air-cooled to room temperature; (4) The billet is heated to 300±50℃ and tempered for 1h.

2. The microalloyed reinforced bainite wear-resistant steel according to claim 1, It is characterized in that In the step (1), the smelting specifically includes: heating the iron block to 1450°C ± 50°C, then adding ferrosilicon blocks, ferromanganese blocks, and nitrogen-chromium cast iron, and continuing to heat them to fully melt them. When the temperature is heated to 1500°C ± 50°C, the temperature is maintained, and titanium ingots, molybdenum wires, and nickel wires are continuously added for alloying smelting for 30-50 minutes.

3. The microalloyed reinforced bainite wear-resistant steel according to claim 1, It is characterized in that In the step (2), the bainitic steel ingot is heated to 600±50°C and kept warm for 1 hour, with a heating rate of ≤75°C / h.

4. The microalloyed reinforced bainite wear-resistant steel according to claim 1, It is characterized in that In the step (2), the bainitic steel ingot is further heated to 1100±50°C and kept warm for 1 hour, with a heating rate of ≤75°C / h.

5. The microalloyed reinforced bainite wear-resistant steel according to claim 1, It is characterized in that In the step (3), the water temperature during water quenching is ≤35°C, the water volume is ≥8L, and the cooling time in water is no more than 1 hour.

6. The microalloyed reinforced bainite wear-resistant steel according to claim 1, It is characterized in that In the step (3), the total hot rolling deformation is 75-85%.

7. The microalloyed reinforced bainite wear-resistant steel according to claim 1, It is characterized in that In the step (3), the total deformation of the warm rolling is 20 to 40%.

8. The microalloyed reinforced bainite wear-resistant steel according to claim 1, It is characterized in that In the step (4), the heating rate is 140°C to 150°C / h.

9. The microalloyed reinforced bainite wear-resistant steel according to claim 1, It is characterized in that In the step (1), the casting process is controlled within 3 minutes.

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