Wear-resistant martensitic stainless steel and preparation method thereof

Abstract

The present invention relates to the technical field of steel materials, specifically to a wear-resistant martensitic stainless steel and a preparation method thereof. A certain amount of V and Ti elements are added to conventional martensitic stainless steel to achieve grain refinement and precipitation strengthening. A quenching-partitioning-tempering heat treatment process and a dynamic strain aging treatment during hot rolling are performed to form a stable retained austenite and secondary martensite duplex structure, thereby significantly improving the wear resistance and toughness of the material. The wear-resistant martensitic stainless steel has a Vickers hardness of over 600 HV and an impact toughness of over 10 J / cm 2 In a ball-on-disc friction and wear test with a load of 200N, a rotation speed of 200r / min, and a wear time of 30min, the wear loss was less than 2mg. Its overall performance surpasses that of traditional martensitic stainless steel, making it suitable for high-wear applications such as cutting tools and bearings.

Description

Technical Field

[0001] The present invention relates to the technical field of steel materials, in particular to wear-resistant martensitic stainless steel and a preparation method thereof. Background Art

[0002] Martensitic stainless steel, renowned for its moderate hardness, excellent corrosion resistance, and good machinability, is widely used in a variety of industries, including cutting tools, medical devices, mechanical parts, and components for chemical equipment. However, traditional martensitic stainless steels such as 40Cr13 are prone to wear and tear over time, shortening equipment life and increasing production costs. While conventional quenching and tempering processes offer some wear resistance, these materials lack the toughness and retained austenite stability to meet the demands of high-load, high-wear operating conditions. Summary of the Invention

[0003] In view of the technical problems existing in the prior art, the present invention provides a wear-resistant martensitic stainless steel and a preparation method thereof.

[0004] According to one aspect of the present invention, the present invention provides the following technical solutions:

[0005] A method for preparing wear-resistant martensitic stainless steel comprises the following steps:

[0006] S1, smelting and casting to obtain a casting;

[0007] S2, performing homogenization treatment on the ingot and then forging;

[0008] S3, hot rolling the forged ingot to obtain a hot-rolled plate;

[0009] S4. The hot-rolled plate is subjected to a quenching-partitioning-tempering treatment, wherein the quenching austenitizing temperature is 980-1100° C. and the holding time is 30-60 min. The plate is then cooled to a quenching stop temperature of 50-200° C. for a first time, and the tempering temperature is 320-450° C. and the holding time is 5-60 min. The plate is then cooled to room temperature for a second time to obtain the wear-resistant martensitic stainless steel, wherein the wear-resistant martensitic stainless steel has a V content of 0.1-0.4wt% and a Ti content of 0.1-0.3wt%.

[0010] According to another aspect of the present invention, the present invention provides the following technical solutions:

[0011] A wear-resistant martensitic stainless steel is prepared by the above-mentioned preparation method of wear-resistant martensitic stainless steel. The microstructure of the wear-resistant martensitic stainless steel is primary martensite, secondary martensite and retained austenite, wherein the retained austenite accounts for more than 20%.

[0012] As a preferred embodiment of the wear-resistant martensitic stainless steel of the present invention, wherein: the wear-resistant martensitic stainless steel has a Vickers hardness of more than 600HV and an impact toughness of 10J / cm 2 As shown above, the wear loss under the ball-on-disc friction and wear test with a load of 200N, a rotation speed of 200r / min, and a wear time of 30min is less than 2mg.

[0013] The beneficial effects of the present invention are as follows:

[0014] The present invention provides a wear-resistant martensitic stainless steel and a preparation method thereof. A certain amount of V and Ti elements are added to traditional martensitic stainless steel to achieve the effects of grain refinement and precipitation strengthening. Through a quenching-partitioning-tempering heat treatment process and a dynamic strain aging treatment during hot rolling, a stable retained austenite and secondary martensite multiphase structure is formed, significantly improving the wear resistance and toughness of the material. The wear-resistant martensitic stainless steel has a Vickers hardness of more than 600 HV and an impact toughness of 10 J / cm 2 In a ball-on-disc friction and wear test with a load of 200N, a rotation speed of 200r / min, and a wear time of 30min, the wear loss was less than 2mg. Its overall performance surpasses that of traditional martensitic stainless steel, making it suitable for high-wear applications such as cutting tools and bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0016] Figure 1 This is the microstructure diagram of the wear-resistant martensitic stainless steel prepared in Example 1.

[0017] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0018] The following will be a clear and complete description of the technical solutions in the embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0019] The present invention provides a wear-resistant martensitic stainless steel and its preparation method. By strictly controlling the heat treatment process to achieve a uniform structure, controlling the strain rate during hot rolling to refine the grains and enhance dislocation strengthening, and obtaining retained austenite through a quenching-partitioning-tempering process, the wear resistance and toughness of the martensitic stainless steel are improved. The resulting wear-resistant martensitic stainless steel is particularly suitable for the manufacture of industrial components requiring high wear resistance and toughness.

[0020] According to one aspect of the present invention, the present invention provides the following technical solutions:

[0021] A method for preparing wear-resistant martensitic stainless steel comprises the following steps:

[0022] S1. smelting and casting to obtain a casting billet;

[0023] S2, performing homogenization treatment on the ingot and then forging;

[0024] S3, hot rolling the forged ingot to obtain a hot-rolled plate;

[0025] S4. The hot-rolled plate is subjected to a quenching-partitioning-tempering treatment, wherein the quenching austenitizing temperature is 980-1100° C. and the holding time is 30-60 min. The plate is then cooled to a quenching stop temperature of 50-200° C. for a first time, and the tempering temperature is 320-450° C. and the holding time is 5-60 min. The plate is then cooled to room temperature for a second time to obtain the wear-resistant martensitic stainless steel, wherein the wear-resistant martensitic stainless steel has a V content of 0.1-0.4wt% and a Ti content of 0.1-0.3wt%.

[0026] The present invention adds a certain amount of V and Ti elements to traditional martensitic stainless steel, which has the effects of grain refinement and precipitation strengthening. At the same time, combined with the quenching-partitioning-tempering heat treatment process, the quenching termination temperature and the tempering process are controlled to obtain a certain proportion of soft phase retained austenite and hard phase secondary martensite. The prepared wear-resistant martensitic stainless steel has good wear resistance and toughness.

[0027] Preferably, in step S2, the homogenization temperature is 1200° C. and the homogenization time is 3 hours.

[0028] Preferably, in step S2, the ingot is forged in the austenite single-phase region; the initial forging temperature is 1200°C, the final forging temperature is 950-1000°C, and the ingot is air-cooled to room temperature after forging. Specifically, the final forging temperature can be, for example, any one of 950°C, 960°C, 970°C, 980°C, 990°C, and 1000°C, or a range between any two thereof.

[0029] Preferably, in step S3, dynamic strain aging treatment is used during hot rolling, and the strain rate is controlled to be 0.1-1s -1 The rolling temperature is 950-1150℃, the total reduction is ≥80%, and then air-cooled to room temperature to refine the grains to the micron level (average size ≤2μm). Combined with controlling the strain rate during hot rolling, the grains are refined to the submicron level, significantly improving the dislocation strengthening and grain refinement effects. Specifically, the strain rate can be, for example, 0.1s -1 , 0.2s -1 , 0.3s -1 , 0.4s -1 , 0.5s -1 , 0.6s -1 , 0.7s -1 , 0.8s -1 , 0.9s -1 , 1s -1 The rolling temperature may be, for example, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, 1050°C, 1060°C, 1070°C, 1080°C, 1090°C, 1100°C, 1110°C, 1120°C, 1130°C, 1140°C, or 1150°C, or a range between any two thereof. During the dynamic strain aging treatment, solute atoms interact with dislocations to form nano-precipitates (with a size of 5-20 nm), and the dislocation density is ≥1×10 15 m -2 .

[0030] Preferably, in step S4, the first cooling is oil cooling and the second cooling is air cooling. Specifically, the quenching austenitizing temperature can be, for example, any one of 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, 1050°C, 1060°C, 1070°C, 1080°C, 1090°C, 1100°C or a range between any two thereof; the holding time can be, for example, any one of 30min, 40min, 50min, 60min or a range between any two thereof; the quenching termination temperature can be, for example, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 2100°C, 2200°C, 2300°C, 2400°C, 2500°C, 2600°C, 2700°C, 2800°C, 2900°C, 3000°C, 3100°C, 3200°C, 3300°C, 3400°C, 3500°C, 3600°C, 3700°C, 3800°C, 3900°C, 4000°C, 4100°C, 4200°C, 4300 The annealing temperature may be, for example, any one of 70°C, 180°C, 190°C, 200°C, or a range between any two of them; the tempering temperature may be, for example, any one of 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C, or 450°C, or a range between any two of them; the holding time may be, for example, any one of 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, or 60 min, or a range between any two of them.

[0031] According to another aspect of the present invention, the present invention provides the following technical solutions:

[0032] A wear-resistant martensitic stainless steel is prepared by the above-mentioned preparation method of wear-resistant martensitic stainless steel. The microstructure of the wear-resistant martensitic stainless steel is primary martensite, secondary martensite and retained austenite, wherein the retained austenite accounts for more than 20%.

[0033] Preferably, the wear-resistant martensitic stainless steel has a Vickers hardness of more than 600 HV and an impact toughness of more than 10 J / cm 2 As shown above, the wear loss under the ball-on-disc friction and wear test with a load of 200N, a rotation speed of 200r / min, and a wear time of 30min is less than 2mg.

[0034] Preferably, the wear-resistant martensitic stainless steel comprises, by mass percentage, C: 0.36-0.45%, Cr: 12.0-14.0%, Si: 0.2-0.8%, Mn: 0.2-0.6%, Ni: 0.2-0.6%, V: 0.1-0.4%, Ti: 0.1-0.3%, P≤0.035%, S≤0.030%, and the balance is Fe and unavoidable impurity elements.

[0035] Carbon is the primary element for martensite formation and a fundamental element for wear resistance. It significantly increases hardness through solid solution strengthening and carbide formation. When the carbon content is below 0.36wt%, there isn't enough carbon to form martensite, failing to meet hardness requirements. Higher carbon content increases martensite hardness, but excessive carbon content leads to a continuous network of carbides, reducing matrix toughness and making brittle spalling more likely. Carbon content is generally below 0.45wt%.

[0036] Cr dissolves in martensite and improves the matrix hardness through solid solution strengthening to form Cr 23 C6 is distributed at grain boundaries or in the matrix, hindering the movement of abrasive particles. To achieve good wear resistance, the Cr content should reach 12wt%. If the Cr content is too low, the number of chromium carbides is insufficient, the oxide film becomes unstable, and wear resistance is significantly reduced. However, excessive Cr content promotes ferrite formation, reduces the martensite content, and coarsens the chromium carbides (prone to flaking when the size is >1μm), which in turn reduces wear resistance. Therefore, the Cr content should be below 14wt%.

[0037] Si can solid-solution strengthen the matrix, slightly increasing hardness, inhibiting carbide precipitation during tempering, and maintaining the stability of the martensite matrix. However, excessive Si content increases matrix brittleness and easily causes microcracks during wear. Therefore, its content should be no more than 0.8wt%. A content that is too low (below 0.2wt%) cannot meet the deoxidation requirements.

[0038] Mn can improve hardenability, ensure uniform cross-section wear resistance, form MnS inclusions (if the S content is high), and can act as a solid lubricant to reduce the friction coefficient. Too low a Mn content (below 0.2wt%) will weaken its deoxidation and desulfurization effects; too much MnS soft phase will reduce hardness, and too high a Mn content will also promote austenite stabilization and reduce the amount of martensite transformation, so the content should be less than 0.6wt%.

[0039] Ni improves toughness and reduces crack propagation during wear. It also lowers the cold-brittle transition temperature, preventing abnormal wear caused by brittle fracture at low temperatures. A content greater than 1wt% stabilizes austenite, hindering martensite formation and resulting in a decrease in hardness.

[0040] V is a strong carbide-forming element. When the content is greater than 0.1wt%, it can refine the grain size and improve the strength and toughness of the steel. However, too high a V content (above 0.4wt%) may reduce ductility and toughness.

[0041] Ti can form titanium carbide, which can strengthen synergistically with vanadium carbide to further increase the density of wear-resistant particles. In 0.36-0.45% C, about 0.1% C can combine with Ti (titanium carbide forms first before Cr). 23C6), so the Ti content needs to be ≥0.1wt%; too high titanium will reduce the effective utilization of carbon (carbon is over-fixed and the hardness of martensite decreases), so the Ti content should be ≤0.3wt%.

[0042] P segregates at grain boundaries, reducing the grain boundary bonding strength and making it easy to peel off along the grain boundaries during wear; S forms a low-melting-point FeS phase, which causes surface roughness during hot working. Therefore, the lower the P and S content, the better.

[0043] The technical solution of the present invention is further described below with reference to specific embodiments.

[0044] Example 1

[0045] A method for preparing wear-resistant martensitic stainless steel comprises the following steps:

[0046] S1, smelting and casting to obtain a casting;

[0047] S2. After homogenizing the ingot at 1200° C. for 3 h, forging the ingot in the austenite single-phase region; the initial forging temperature is 1200° C., the final forging temperature is 1000° C., and the ingot is air-cooled to room temperature after forging.

[0048] S3. The forged ingot is hot rolled to obtain a hot rolled plate; dynamic strain aging treatment is used during the hot rolling process, and the strain rate is controlled to be 0.5s -1 , rolling temperature is 1100℃, total reduction is 85%, and then air-cooled to room temperature;

[0049] S4, performing a quenching-partitioning-tempering treatment on the hot-rolled plate; wherein the quenching austenitizing temperature is 1050° C. and the holding time is 60 min, followed by a first oil cooling to a quenching stop temperature of 150° C.; a tempering temperature is 400° C. and the holding time is 30 min; and then a second air cooling to room temperature is performed to obtain the wear-resistant martensitic stainless steel.

[0050] The wear-resistant martensitic stainless steel of this embodiment includes, by mass percentage, C: 0.39%, Cr: 13.1%, Si: 0.4%, Mn: 0.6%, Ni: 0.4%, V: 0.15%, Ti: 0.15%, P: 0.009%, S: 0.012%, and the balance is Fe and unavoidable impurity elements.

[0051] Example 2

[0052] The difference from Example 1 is that in step S4, the quenching termination temperature is 50°C.

[0053] Example 3

[0054] The difference from Example 1 is that in step S4, the quenching stop temperature is 100°C.

[0055] Example 4

[0056] The difference from Example 1 is that in step S4, the quenching stop temperature is 200°C.

[0057] Comparative Example 1

[0058] The difference from Example 1 is that in step S3, dynamic strain aging treatment is not used during the hot rolling process.

[0059] Comparative Example 2

[0060] The difference from Example 1 is that in step S4, the oil is cooled to room temperature for the first time.

[0061] Comparative Example 3

[0062] The difference from Example 1 is that the V element content is 0.8 wt %.

[0063] Comparative Example 4

[0064] The difference from Example 1 is that the Ti element content is 0.5 wt %.

[0065] Comparative Example 5

[0066] The difference from Example 1 is that V and Ti elements are not contained.

[0067] The microstructure of the sample was observed by scanning electron microscope. The microstructure of the wear-resistant martensitic stainless steel prepared in Example 1 is as follows: Figure 1 As shown by Figure 1 It can be seen that the microstructure of the wear-resistant martensite stainless steel of Example 1 of the present invention is mainly composed of primary martensite, secondary martensite, carbide and retained austenite. After the first quenching is terminated at 150°C, the microstructure retains a portion of untransformed austenite. Subsequently, at a tempering temperature of 400°C, carbon atoms diffuse from the martensite to the retained austenite. The retained austenite becomes stable due to the abundance of carbon and does not undergo phase transformation during the subsequent cooling process and is retained. The stable retained austenite can improve the toughness of the material, and the secondary martensite with higher hardness can ensure the high hardness of the material.

[0068] Sliding wear tests were conducted on a multifunctional tribological testing machine. The grinding balls were made of ceramic steel with a hardness of approximately 1400 HV and a diameter of 6.35 mm. Ball-on-disc friction and wear tests were conducted with a load of 200 N, a rotation speed of 200 r / min, and a wear time of 30 min. The specimen size in the sliding wear test was 12 mm × 14 mm × 2 mm, and the surface was ground and polished. The ball-on-disc friction and wear tests were conducted at room temperature and atmospheric conditions. All working conditions were repeated three times to ensure the repeatability and accuracy of the experiments, and the average of the three experiments was taken as the experimental result. The surface morphology of the samples was observed using a field emission scanning electron microscope.

[0069] Hardness was measured using a micro-Vickers hardness tester under a load of 9.8 N. The average of 10 points was taken for each specimen. Impact tests were conducted on a 10 mm × 10 mm × 55 mm V-notched specimen, with the average of three data points taken.

[0070] The performance test results of the embodiments of the present invention and the comparative examples are shown in Table 1.

[0071]

[0072] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention specification under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing wear-resistant martensitic stainless steel, characterized in that: The steps include: S1. smelting and casting to obtain a casting billet; S2, performing homogenization treatment on the ingot and then forging; S3. Hot rolling the forged ingot to obtain a hot-rolled plate; dynamic strain aging treatment is used during the hot rolling process, and the strain rate is controlled to be 0.1-1s -1 ; S4, performing a quenching-partitioning-tempering treatment on the hot-rolled plate; wherein the quenching austenitizing temperature is 980-1100° C., the holding time is 30-60 min, followed by a first cooling to a quenching stop temperature of 50-200° C.; the tempering temperature is 320-450° C., the holding time is 5-60 min; and then a second cooling to room temperature to obtain the wear-resistant martensitic stainless steel; The wear-resistant martensitic stainless steel, expressed in mass percentage, include, C: 0.36-0.45%, Cr: 12.0-14.0%, Si: 0.2-0.8%, Mn: 0.2-0.6%, Ni: 0.2-0.6%, V: 0.1-0.4%, Ti: 0.1-0.3%, P≤0.035%, S≤0.030%, the balance is Fe and unavoidable impurity elements; The wear-resistant martensitic stainless steel has a Vickers hardness of more than 600 HV and an impact toughness of 10 J / cm 2 As shown above, the wear loss under the ball-on-disc friction and wear test with a load of 200N, a rotation speed of 200r / min, and a wear time of 30min is less than 2mg.

2. The method for preparing wear-resistant martensitic stainless steel according to claim 1, characterized in that: In step S2, the homogenization temperature is 1200° C. and the homogenization time is 3 hours.

3. The method for preparing wear-resistant martensitic stainless steel according to claim 1, characterized in that: In the step S2, the ingot is forged in the austenite single phase region; the initial forging temperature is 1200° C., the final forging temperature is 950-1000° C., and the ingot is air-cooled to room temperature after forging.

4. The method for preparing wear-resistant martensitic stainless steel according to claim 1, characterized in that: In step S3, the rolling temperature is 950-1150° C., the total reduction is ≥80%, and then the steel is air-cooled to room temperature to refine the grains to micron level.

5. The method for preparing wear-resistant martensitic stainless steel according to claim 1, characterized in that: In step S4, the first cooling is oil cooling, and the second cooling is air cooling.

6. A wear-resistant martensitic stainless steel, characterized in that: The wear-resistant martensitic stainless steel is prepared by the preparation method of any one of claims 1 to 5, wherein the structure of the wear-resistant martensitic stainless steel is primary martensite, secondary martensite and retained austenite, wherein the retained austenite accounts for more than 20%.

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