High-strength high-carbon bainitic wear-resistant steel and preparation method therefor

Abstract

The present application relates to a high-strength high-carbon bainitic wear-resistant steel and a preparation method therefor, belonging to the technical field of high-strength steel materials and solving the problems that the bainite isothermal transformation time in existing high-carbon bainitic steels is long and that existing accelerated transformation methods have high alloying costs and a complex heat treatment process. The components of the high-strength high-carbon bainitic wear-resistant steel are, by mass percentage: 0.65-0.90 wt% of C, 1.0-1.55 wt% of Si, 1.90-2.20 wt% of Mn, 0.70-0.95 wt% of Cr, 0.50-0.70 wt% of Ni, 0.85-1.10 wt% of Al, 0.001-0.0035 wt% of O, and 0.01-0.03 wt% of Ce, the ratio of C content to Cr content C / Cr being less than 1, and the rest being Fe and unavoidable impurities. The bainitic wear-resistant steel and the preparation method of the present application have a short bainite phase transformation time and a simple heat treatment process.

Description

A high-strength high-carbon bainite wear-resistant steel and its preparation method Technical Field

[0001] The present application relates to the technical field of high-strength steel materials, and in particular to a high-strength, high-carbon, bainite wear-resistant steel and a preparation method thereof. Background Art

[0002] High-carbon, low-temperature bainitic steel (also known as nano-bainitic steel or super bainitic steel) is a type of steel that has attracted much attention in the field of wear-resistant materials in recent years. After austenitization, this type of steel undergoes isothermal treatment at 200-350°C to obtain an ultrafine bainitic ferrite structure (the lath width can be refined to tens of nanometers). The unique microstructure gives this type of steel excellent strength and wear resistance. In addition, the composition of typical high-carbon, low-temperature bainitic steel is mainly composed of elements such as Fe, C, Mn, Si, Cr, and Mo, and the alloy cost is controllable. High-carbon, low-temperature bainitic steel has broad application prospects in the field of high-performance wear-resistant steel. However, the excessively long phase transformation process (typical high-carbon, low-temperature bainitic steel requires dozens of hours or even days for complete phase transformation) significantly reduces the production efficiency of this type of steel.

[0003] To shorten the phase transformation time and improve the production efficiency of high-carbon, low-temperature bainitic steel, technicians have adopted various methods. Invention patent CN108384928B reports a method for accelerating the nano-bainite phase transformation. This method uses a two-stage isothermal phase transformation method to promote the phase transformation of high-carbon bainitic steel. After austenitization, the steel material undergoes a first stage transformation at a first temperature (5 to 100°C above the martensite transformation temperature). The temperature is then raised to a second temperature for a second isothermal transformation, thereby shortening the phase transformation time. This method adopts a two-stage isothermal treatment and adds an additional heat treatment process. Invention patent CN108384928B reports a method for accelerating the bainite phase transformation in steel using in-situ nano-AlN heterogeneous nucleation. 0.1-0.2wt% Al and 100-200ppm N are added to the steel, and uniformly distributed AlN particles with a size of 20-100nm and a volume fraction of 0.1-0.2vol.% are precipitated in situ in the steel to promote the bainite phase transformation. However, for some high-carbon, low-temperature bainitic steels with high aluminum content, controlling the AlN size and content in this method is relatively difficult. Invention patent CN103451549B reports a 2100MPa nano-bainite steel and its preparation method. In this method, the ingot is forged and hot-rolled, and then subjected to high-temperature isothermal treatment, salt bath cooling, and low-temperature salt bath isothermal treatment, and kept at 200-300°C for 10-100 hours to obtain fine nano-sized bainitic ferrite. Although the salt bath treatment can obtain high tensile strength, the salt bath treatment increases the complexity of the heat treatment, which is not conducive to large-scale production. In addition, 1.0-3.0wt% of Co is added to the steel to promote bainite phase transformation, which increases the alloy cost.

[0004] Therefore, it is necessary to continue to optimize the composition design and preparation method of high-carbon and low-temperature bainitic steel and shorten the phase transformation time.

[0005] Summary of the Invention

[0006] In view of the above analysis, the embodiments of the present application aim to provide a high-strength, high-carbon, bainitic wear-resistant steel and a preparation method thereof, to at least solve one of the following problems existing in the existing high-strength, high-carbon, bainitic wear-resistant steel and a preparation method thereof: 1. In the preparation process of the existing high-strength, high-carbon, bainitic wear-resistant steel, the time required for the bainite phase transformation is long, resulting in low production efficiency; 2. The method adopted in the preparation process of the existing high-strength, high-carbon, bainitic wear-resistant steel to shorten the phase transformation process time has high alloy cost and complex heat treatment process, which is not conducive to large-scale production.

[0007] The purpose of this application is mainly achieved according to the following technical solutions:

[0008] The present application provides a high-strength, high-carbon bainitic wear-resistant steel, the components of which are, by mass percentage, C 0.65-0.90wt%, Si 1.0-1.55wt%, Mn 1.90-2.20wt%, Cr 0.70-0.95wt%, Ni 0.50-0.70wt%, Al 0.85-1.10wt%, O 0.001-0.0035wt% and Ce 0.01-0.03wt%, the C content and Cr content ratio C / Cr is less than 1, and the rest is Fe and unavoidable impurities.

[0009] Furthermore, the components of the high-strength high-carbon bainitic wear-resistant steel are, by mass percentage, C 0.67-0.90wt%, Si 1.06-1.55wt%, Mn 1.91-2.20wt%, Cr 0.72-0.95wt%, Ni 0.57-0.70wt%, Al 0.85-0.98wt%, O 0.0018-0.0035wt% and Ce 0.013-0.03wt%, the C content and Cr content ratio C / Cr is less than 1, and the rest is Fe and unavoidable impurities.

[0010] Furthermore, the microstructure of the high-strength high-carbon bainitic wear-resistant steel includes bainitic ferrite and retained austenite, wherein the width of the bainitic ferrite lath is less than 200 nm.

[0011] The present application also provides a method for preparing high-strength high-carbon bainite wear-resistant steel, which is used to prepare the above-mentioned high-strength high-carbon bainite wear-resistant steel, comprising the following steps:

[0012] S1: Weigh the alloy raw materials according to the proportion of wear-resistant steel alloy components;

[0013] S2: smelting, casting and forging the alloy raw materials to obtain a first steel ingot;

[0014] S3: reheating the first steel ingot to 950-1030° C., keeping the temperature, and then cooling it to the low-temperature bainite phase transformation temperature to obtain a second steel ingot;

[0015] S4: isothermally treating the second steel ingot at 230-300° C. and then cooling to room temperature to obtain bainite wear-resistant steel.

[0016] Furthermore, in step S2, the smelting is non-vacuum induction smelting.

[0017] Furthermore, in step S2, the thickness of the first steel ingot is 15-30 mm.

[0018] Furthermore, in step S2, the first steel ingot contains rare earth oxides, and the volume fraction of the rare earth oxides is 0.1-0.2 vol%.

[0019] Furthermore, the size of the rare earth oxide is 0.5 to 3 μm.

[0020] Furthermore, in step S3, the holding time is 1.5-2 times the thickness of the first steel ingot, in minutes.

[0021] Furthermore, in step S4, the isothermal treatment time is 6 to 12 hours.

[0022] Compared with the prior art, this application can achieve at least one of the following beneficial effects:

[0023] 1. This application provides a high-strength, high-carbon, bainitic wear-resistant steel and a method for its preparation. The steel incorporates highly stable rare earth oxide particles into its composition, eliminating the need for additional heat treatment. The rare earth oxide particles provide effective nucleation sites for the bainitic-ferrite phase transformation, thereby promoting the high-carbon bainite phase transformation. They also enable isothermal treatment at lower temperatures, resulting in finer bainitic ferrite. Furthermore, the addition of rare earth oxide particles shortens the bainitic phase transformation time, potentially improving the industrial production efficiency of high-carbon bainitic steel.

[0024] 2. The preparation method of high-strength, high-carbon bainitic wear-resistant steel provided in this application designs a higher steel austenitizing temperature based on the addition of rare earth oxide particles, thereby obtaining larger austenite grains; on the one hand, the higher steel austenitizing temperature is conducive to the growth of bainitic ferrite during the low-temperature isothermal process; on the other hand, the large austenite grain size can promote the bainitic ferrite phase transformation, so that more bainite structure is obtained in the steel, thereby improving the strength and toughness of the high-carbon bainitic wear-resistant steel.

[0025] 3. The wear-resistant steel of the present application is designed with a high carbon component, so that the martensite transformation temperature of the steel drops below 200°C, ensuring that the bainite phase transformation occurs within the range of 230-300°C, thereby obtaining ultrafine bainitic ferrite, wherein the width of the bainitic ferrite lath is less than 200nm. The Si and Al matching design is used to suppress the precipitation of cementite during the bainite phase transformation. Compared with the single addition of Si, the addition of Al elements can obtain a greater driving force for the bainite phase transformation, promote the bainite phase transformation, avoid the addition of expensive elements such as Co, and reduce the alloy cost. At the same time, Mn and Cr elements are used to improve the hardenability, and the carbon content and chromium content ratio C / Cr is designed to be less than 1, which suppresses the occurrence of pearlite phase transformation in the high-carbon bainitic wear-resistant steel during the air cooling process after austenitization, ensuring that the high-carbon bainitic wear-resistant steel obtains ultrafine bainitic ferrite and retained austenite, thereby obtaining high tensile strength and elongation after fracture. The high carbon bainite wear-resistant steel is austenitized at 950-1030° C., then cooled to 230-300° C. and isothermal for 6-12 hours. The wear-resistant steel finally prepared has a tensile strength of 1500-2077 MPa, a yield strength of 1030-1291 MPa, and an elongation after fracture of 6-17%.

[0026] In this application, the above-mentioned technical solutions can be combined with each other to achieve more preferred combination solutions. Other features and advantages of this application will be described in the subsequent description, and some advantages will become apparent from the description or be understood by practicing this application. The objectives and other advantages of this application can be achieved and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered as limiting the present application. Like reference symbols denote like components throughout the drawings.

[0028] FIG1 is a scanning electron microscope image of the steel of Example 1;

[0029] FIG2 is a scanning electron microscope morphology image and EDS energy spectrum analysis image of the steel in Example 2;

[0030] FIG3 is a transmission electron microscope image of the steel of Example 3;

[0031] FIG4 is a tensile curve diagram of the steel of Examples 1-3;

[0032] FIG5 is a scanning electron microscope image of the steel of Comparative Example 1;

[0033] FIG6 is a graph showing the isothermal phase transformation curves of austenitization and bainite regions of the steels of Example 1 and Comparative Example 1;

[0034] FIG7 is a scanning electron microscope image of Comparative Example 2;

[0035] FIG8 is a scanning electron microscope image of Comparative Example 3. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present application are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present application and are used together with the embodiments of the present application to illustrate the principles of the present application, and are not used to limit the scope of the present application.

[0037] The present application provides a high-strength, high-carbon bainite wear-resistant steel, the components of which are, by mass percentage, C 0.65-0.90wt%, Si 1.0-1.55wt%, Mn 1.90-2.20wt%, Cr 0.70-0.95wt%, Ni 0.50-0.70wt%, Al 0.85-1.10wt%, O 0.001-0.0035wt% and Ce 0.01-0.03wt%, with the remainder being Fe and unavoidable impurities.

[0038] The reasons for limiting the alloy composition of the high-strength, high-carbon, bainite wear-resistant steel and its preparation method in this application are explained below. Only wt% is used to represent the mass percentage in the composition.

[0039] C: The role of carbon element in this application includes three aspects. First, the increase in carbon content can significantly improve the strength of steel; second, the use of a high-carbon composition design can reduce the martensite transformation temperature of steel to below 200°C, ensuring that the bainite phase transformation can proceed at a lower temperature above 200°C, thereby obtaining ultrafine bainitic ferrite; third, the increase in carbon content can significantly improve the strength of austenite; therefore, the content of C element in this application is 0.65~0.90wt%.

[0040] Si, Al: The addition of Si and Al elements to high-carbon bainitic steel can effectively inhibit the precipitation of cementite in austenite during the bainite phase transformation, thereby obtaining bainitic ferrite and residual austenite structure, and achieving a match between high strength and high plasticity; compared with the single addition of Si, the addition of Al element can obtain a greater driving force for the bainite phase transformation, thereby promoting the bainite phase transformation; therefore, the content of Si element in this application is 1.0~1.55wt%, and the content of Al element is 0.85~1.10wt%.

[0041] Mn and Cr: Adding Mn significantly delays high-temperature phase transformation and improves the hardenability of steel. Adding Cr not only improves the hardenability of steel but also lowers the bainite transformation temperature, allowing the bainite transformation to occur at a lower temperature. Excessive Mn content increases the tendency for segregation in the ingot, while excessive Cr content can easily form brittle carbides such as Cr7C3 in the steel. Both of these factors can degrade the steel's plasticity and toughness. Therefore, the Mn content in this application is 1.90-2.20 wt%, and the Cr content is 0.70-0.95 wt%.

[0042] Ni: The addition of Ni element can improve the toughness of steel. Adding Ni to high-carbon bainitic wear-resistant steel can make it have high strength and high toughness at the same time; however, adding a large amount of Ni element will significantly increase the cost of steel. Therefore, the Ni content in this application is 0.50~0.70wt%.

[0043] Ce and O: Adding Ce to high-carbon bainitic wear-resistant steel while retaining a certain amount of O forms Ce-containing oxide particles during the smelting process, providing effective nucleation sites for the bainitic-ferrite phase transformation, thereby promoting the high-carbon bainite phase transformation. When the Ce and O content is too low, fewer oxide particles are formed, and the phase transformation effect is less pronounced. When the O content is too high, other oxygen-containing non-metallic inclusions are easily formed, deteriorating the steel's plasticity and toughness. In this application, the Ce content is 0.01-0.03wt% and the O content is 0.001-0.0035wt%.

[0044] Furthermore, in the alloy composition, the ratio of carbon content to chromium content is C / Cr<1.

[0045] It should be noted that when the carbon content in steel approaches 0.77wt%, pearlite is very likely to form. In this application, the carbon content is increased while the chromium content is increased. The carbon content and chromium content ratio (C / Cr) are designed to be less than 1, thereby ensuring the steel's hardenability while suppressing pearlite transformation. If C / Cr is ≥ 1, this series of high-carbon bainitic steels are prone to pearlite transformation during the isothermal cooling process to the bainite region after austenitization, which deteriorates their strength and toughness.

[0046] Preferably, a high-strength, high-carbon bainitic wear-resistant steel comprises, in mass percentage, the following components: C 0.67-0.90wt%, Si 1.06-1.55wt%, Mn 1.91-2.20wt%, Cr 0.72-0.95wt%, Ni 0.57-0.70wt%, Al 0.85-0.98wt%, O 0.0018-0.0035wt% and Ce 0.013-0.03wt%, with the remainder being Fe and unavoidable impurities.

[0047] The present application also provides a method for preparing high-strength high-carbon bainite wear-resistant steel, which is used to prepare the above-mentioned high-strength high-carbon bainite wear-resistant steel, comprising the following steps:

[0048] S1: Weigh a certain amount of alloy raw materials according to the composition ratio of wear-resistant steel alloy;

[0049] S2: smelting, casting and forging the alloy raw materials to obtain a first steel ingot;

[0050] S3: reheating the first steel ingot to 950-1030° C., keeping the temperature, and then cooling it to the low-temperature bainite phase transformation temperature to obtain a second steel ingot;

[0051] S4: isothermally treating the second steel ingot at 230-300° C. and then cooling to room temperature to obtain bainite wear-resistant steel.

[0052] Specifically, in step S1, the alloy raw materials are calculated by mass percentage: C 0.65-0.90wt%, Si 1.0-1.55wt%, Mn 1.90-2.20wt%, Cr 0.70-0.95wt%, Ni 0.50-0.70wt%, Al 0.85-1.10wt%, O 0.001-0.0035wt% and Ce 0.01-0.03wt%, with the remainder being Fe and unavoidable impurities.

[0053] Specifically, in step S2, the smelting is performed using non-vacuum induction smelting. The first steel ingot obtained after casting and forging has a thickness of 15-30 mm, a volume fraction of rare earth oxides in the ingot of 0.1-0.2 vol%, and a size of 0.5-3 μm. It should be noted that in this application, rare earth oxide particles are obtained during the smelting process, providing nucleation sites for the bainite transformation during the subsequent heat treatment. This means that a certain content of rare earth elements and oxygen is required during the smelting process. If vacuum smelting is used, rare earth oxide particles are difficult to obtain due to the low oxygen content. If the first steel ingot is less than 15 mm thick, the ingot is prone to deformation during forging, requiring additional straightening steps. In subsequent processes, the steel ingot in this application is cooled to the low-temperature bainite transformation zone after austenitization using air cooling. Therefore, when the first steel ingot is thicker than 30 mm, insufficient cooling intensity can easily cause high-temperature transformations such as pearlite in the ingot's core, hindering the achievement of the ultrafine bainitic ferrite structure described in this application.

[0054] Specifically, in step S3, the first steel ingot is reheated to 950-1030°C, and the holding time is determined according to the sample thickness of the first steel ingot (in mm). Generally, the holding time (i.e., the austenitizing time) is 1.5-2 times the thickness of the first steel ingot (in min). After that, the ingot is taken out of the furnace and cooled to the low-temperature bainite phase transformation zone temperature (generally 230-300°C) to obtain the second steel ingot; it should be noted that the austenitizing temperature in the prior art is 30-50°C above Ac3 (taking Example 2 as an example, Ac3=825°C), and 950-1030°C is the austenitizing temperature of the steel designed in this application. A higher austenitizing temperature can bring a larger austenite grain size, which is conducive to the growth of bainitic ferrite, thereby further promoting the bainitic ferrite phase transformation; on the other hand, a large austenite grain size can promote the bainitic ferrite phase transformation, so that more bainite structure is obtained in the steel, which can improve the mechanical properties of the experimental steel. When the austenitizing temperature is below 950°C, the austenite grain size is small, which has little effect on promoting the bainite-ferrite phase transformation. When the austenitizing temperature exceeds 1030°C, the austenite grain size becomes too large, deteriorating the mechanical properties of the steel. After holding at 950-1030°C, air cooling is used during the cooling process to the low-temperature bainite phase transformation zone. Air cooling eliminates the need for quenching media such as water or oil, simplifying the production process.

[0055] Specifically, in step S4, the second steel ingot is isothermally treated at 230-300°C for 6-12 hours and then cooled to room temperature to obtain bainitic wear-resistant steel. It should be noted that the high-carbon bainitic wear-resistant steel in this application has a high carbon content, and the bainitic phase transformation requires a long time. As can be seen from the isothermal phase transformation curve of the bainite region of the steel in Example 1 in Figure 3, when the isothermal time is less than 6 hours, the phase transformation is insufficient. After 6 hours of isothermal treatment, the bainitic ferrite phase transformation is gradually completed. Although isothermal treatment time longer than 12 hours is beneficial for obtaining more bainitic ferrite, excessively long isothermal treatment times significantly increase industrial production costs.

[0056] In step S4, the second steel ingot is isothermally treated at 230-300°C. At this temperature, the bainite phase transformation of the steel occurs at a relatively low temperature, thereby obtaining ultrafine bainitic ferrite and retained austenite. It should be noted that the lower the isothermal treatment temperature, the finer the width of the resulting bainitic ferrite laths. However, when the isothermal temperature of the bainite region is below 230°C, the bainite phase transformation time is too long, which is not conducive to industrial production. When the isothermal temperature of the bainite region is above 300°C, the bainitic ferrite laths are relatively wide, which is not conducive to improving the strength of the steel.

[0057] The high-strength, high-carbon, bainitic wear-resistant steel prepared in the present application has a microstructure comprising bainitic ferrite and retained austenite, wherein the width of the bainitic ferrite lath is less than 200 nm; the high-strength, high-carbon, bainitic wear-resistant steel prepared in the present application has a tensile strength of 1500-2077 MPa, a yield strength of 1030-1291 MPa, and an elongation after fracture of 6-17%.

[0058] Example 1

[0059] This embodiment provides a high-strength, high-carbon bainitic wear-resistant steel, the components of which are, by mass percentage, 0.75 wt% C, 1.06 wt% Si, 2.02 wt% Mn, 0.80 wt% Cr, 0.57 wt% Ni, 0.98 wt% Al, 0.0022 wt% O and 0.013 wt% Ce, with the remainder being Fe and unavoidable impurities.

[0060] Among them, C / Cr=0.75 / 0.80=0.94<1;

[0061] The method for preparing the above-mentioned high-strength high-carbon bainite wear-resistant steel comprises the following steps:

[0062] S1: Weigh the alloy raw materials according to the proportion of wear-resistant steel alloy components;

[0063] S2: The alloy raw material is subjected to non-vacuum induction smelting, casting, and forging to obtain a first steel ingot, wherein the steel ingot has a thickness of 30 mm, a volume fraction of rare earth oxides in the steel ingot of 0.12 vol%, and an average size of 1.1 μm;

[0064] S3: reheating the first steel ingot to 950°C, holding the temperature for 60 minutes, and then cooling the ingot to 300°C (low-temperature bainite transformation zone temperature) to obtain a second steel ingot;

[0065] S4: The second steel ingot is isothermally treated at 300° C. for 6 h, and then cooled to room temperature to obtain bainite wear-resistant steel.

[0066] Example 2

[0067] This embodiment provides a high-strength, high-carbon bainitic wear-resistant steel, the components of which are, by mass percentage, 0.88 wt% C, 1.25 wt% Si, 2.11 wt% Mn, 0.90 wt% Cr, 0.62 wt% Ni, 0.94 wt% Al, 0.0018 wt% O and 0.023 wt% Ce, with the remainder being Fe and unavoidable impurities.

[0068] Among them, C / Cr=0.88 / 0.90=0.98<1;

[0069] The method for preparing the above-mentioned high-strength high-carbon bainite wear-resistant steel comprises the following steps:

[0070] S1: Weigh the alloy raw materials according to the proportion of wear-resistant steel alloy components;

[0071] S2: The alloy raw material is subjected to non-vacuum induction smelting, casting, and forging to obtain a first steel ingot, wherein the steel ingot has a thickness of 15 mm, a volume fraction of rare earth oxides in the steel ingot of 0.17 vol%, and an average size of 2.5 μm;

[0072] S3: reheating the first steel ingot to 1030°C, keeping the temperature for 30 minutes, and then cooling it to 230°C (low-temperature bainite phase transformation zone) to obtain a second steel ingot;

[0073] S4: The second steel ingot was isothermally treated at 230° C. for 12 h, and then cooled to room temperature to obtain bainite wear-resistant steel.

[0074] Example 3

[0075] This embodiment provides a high-strength, high-carbon bainitic wear-resistant steel, the components of which are, by mass percentage, 0.67 wt% C, 1.5 wt% Si, 1.91 wt% Mn, 0.72 wt% Cr, 0.64 wt% Ni, 0.85 wt% Al, 0.003 wt% O and 0.018 wt% Ce, with the remainder being Fe and unavoidable impurities.

[0076] Among them, C / Cr=0.67 / 0.72=0.93<1;

[0077] The method for preparing the above-mentioned high-strength high-carbon bainite wear-resistant steel comprises the following steps:

[0078] S1: Weigh the alloy raw materials according to the proportion of wear-resistant steel alloy components;

[0079] S2: The alloy raw material is subjected to non-vacuum induction smelting, casting, and forging to obtain a first steel ingot, wherein the steel ingot has a thickness of 20 mm, a volume fraction of rare earth oxides in the steel ingot of 0.15 vol%, and an average size of 1.8 μm;

[0080] S3: reheating the first steel ingot to 1000°C, keeping it at this temperature for 30 minutes, and then cooling it to 250°C (low-temperature bainite transformation zone temperature) to obtain a second steel ingot;

[0081] S4: The second steel ingot is isothermally treated at 250° C. for 10 h, and then cooled to room temperature to obtain bainite wear-resistant steel.

[0082] Comparative Example 1

[0083] This comparative example provides a high-carbon bainite wear-resistant steel, the components of which are, by mass percentage, 0.72 wt% C, 1.15 wt% Si, 1.91 wt% Mn, 0.80 wt% Cr, 0.63 wt% Ni, 0.97 wt% Al, 0.008 wt% O, and the remainder being Fe and unavoidable impurities.

[0084] The method for preparing the above-mentioned high-strength high-carbon bainite wear-resistant steel comprises the following steps:

[0085] S1: Weigh the alloy raw materials according to the proportion of wear-resistant steel alloy components;

[0086] S2: non-vacuum induction smelting, casting, and forging the alloy raw materials to obtain a first steel ingot, wherein the steel ingot has a thickness of 30 mm and contains no rare earth oxide particles;

[0087] S3: reheating the first steel ingot to 950°C, keeping it at this temperature for 60 minutes, and then cooling it to 300°C (low-temperature bainite transformation zone temperature) to obtain a second steel ingot;

[0088] S4: The second steel ingot is isothermally treated at 300° C. for 6 h, and then cooled to room temperature to obtain bainite wear-resistant steel.

[0089] Comparative Example 2

[0090] This comparative example provides a high carbon bainite wear-resistant steel, the components of which are, by mass percentage, 0.89 wt% C, 1.45 wt% Si, 2.00 wt% Mn, 0.75 wt% Cr, 0.60 wt% Ni, 0.85 wt% Al, 0.002 wt% O and 0.017 wt% Ce, with the remainder being Fe and unavoidable impurities.

[0091] Among them, C / Cr=0.89 / 0.75=1.19>1;

[0092] The method for preparing the above-mentioned high-strength high-carbon bainite wear-resistant steel comprises the following steps:

[0093] S1: Weigh the alloy raw materials according to the proportion of wear-resistant steel alloy components;

[0094] S2: The alloy raw materials are subjected to non-vacuum induction smelting, casting, and forging to obtain a first steel ingot, wherein the steel ingot has a thickness of 20 mm, a volume fraction of rare earth oxides in the steel ingot of 0.16 vol%, and an average size of 2.1 μm;

[0095] S3: reheating the first steel ingot to 980°C, keeping the temperature for 30 minutes, and then cooling it to 250°C (low-temperature bainite phase transformation temperature) to obtain a second steel ingot;

[0096] S4: The second steel ingot was isothermally treated at 250° C. for 12 h, and then cooled to room temperature to obtain bainite wear-resistant steel.

[0097] Comparative Example 3

[0098] This comparative example provides a high-carbon bainite wear-resistant steel, whose components, in mass percentage, are: C 0.74wt%, Si 1.16wt%, Mn 2.03wt%, Cr 0.82wt%, Ni 0.56wt%, Al 0.89wt%, O < 0.0005wt% and Ce 0.03wt%, with the remainder being Fe and unavoidable impurities.

[0099] Among them, C / Cr=0.74 / 0.82=0.90<1;

[0100] The method for preparing the above-mentioned high-strength high-carbon bainite wear-resistant steel comprises the following steps:

[0101] S1: Weigh a certain amount of alloy raw materials according to the composition ratio of wear-resistant steel alloy;

[0102] S2: The alloy raw materials are subjected to vacuum induction smelting, casting, and forging to obtain a first steel ingot, wherein the steel ingot has a thickness of 20 mm and almost no rare earth oxides are found in the steel ingot;

[0103] S3: reheating the first steel ingot to 1000°C, keeping it at this temperature for 30 minutes, and then cooling it to 250°C (low-temperature bainite transformation zone temperature) to obtain a second steel ingot;

[0104] S4: The second steel ingot is isothermally treated at 250° C. for 10 h, and then cooled to room temperature to obtain bainite wear-resistant steel.

[0105] Comparative Example 4

[0106] This comparative example provides a high-strength, high-carbon, bainite wear-resistant steel, the components of which are as follows in percentage by mass:

[0107] C 0.88 wt%, Si 1.25 wt%, Mn 2.11 wt%, Cr 0.90 wt%, Ni 0.62 wt%, Al 0.94 wt%, O 0.0018 wt% and Ce 0.023 wt%, with the remainder being Fe and inevitable impurities.

[0108] Wherein, C / Cr=0.88 / 0.90=0.98<1;

[0109] The method for preparing the above-mentioned high-strength high-carbon bainite wear-resistant steel comprises the following steps:

[0110] S1: Weigh the alloy raw materials according to the proportion of wear-resistant steel alloy components;

[0111] S2: The alloy raw material is subjected to non-vacuum induction smelting, casting, and forging to obtain a first steel ingot, wherein the steel ingot has a thickness of 15 mm, a volume fraction of rare earth oxides in the steel ingot of 0.17 vol%, and an average size of 2.5 μm;

[0112] S3: reheating the first steel ingot to 870°C, keeping the temperature for 30 minutes, and then cooling it to 230°C (low-temperature bainite transformation zone temperature) to obtain a second steel ingot;

[0113] S4: The second steel ingot was isothermally treated at 230° C. for 5 h, and then cooled to room temperature to obtain bainite wear-resistant steel.

[0114] Table 1 Wear-resistant steel composition (wt%) of Examples and Comparative Examples

[0115] Table 2 Process parameters for the preparation of wear-resistant steel in Examples and Comparative Examples

[0116] Table 3 Mechanical properties of wear-resistant steels of Examples and Comparative Examples

[0117] In Example 1, the steel composition, preparation method, and process parameters during the preparation process all meet the requirements of this application. Figure 1 is a scanning electron microscope image of the wear-resistant steel produced in Example 1. As can be seen from the image, the microstructure of the wear-resistant steel comprises bainite and retained austenite, with rare earth oxide particles distributed in the matrix. Part of the bainite structure is formed and grown by the rare earth oxide particles. The wear-resistant steel produced in Example 1 has a yield strength of 1041 MPa, a tensile strength of 1533 MPa, and an elongation after fracture of 17.0%.

[0118] In Example 2, the steel composition, preparation method, and process parameters during the preparation process all meet the requirements of this application. Figure 2 shows the scanning electron microscope morphology and EDS spectrum analysis of the wear-resistant steel produced in Example 2. The EDS analysis results show that the fine particles are rare earth oxides containing Ce. Compared with Example 1, the carbon content in Example 2 is increased, the bainite isothermal temperature is lowered, and the tensile strength in Example 2 is increased to 2077 MPa.

[0119] In Example 3, the steel composition, preparation method, and process parameters during the preparation process all meet the requirements of this application. Figure 3 is a transmission electron microscopy image of Example 3, showing that the wear-resistant steel's microstructure is similar to that of Example 1, including bainite and retained austenite. The wear-resistant steel prepared in Example 3 has a yield strength of 1291 MPa, a tensile strength of 1914 MPa, and an elongation of 11.5%. Figure 4 shows the tensile curves of Examples 1, 2, and 3. The tensile strength of the steel in all three examples exceeds 1500 MPa, and the elongation exceeds 6%.

[0120] In Comparative Example 1, the steel composition does not meet the requirements of this application. Ce is not added, and the oxygen content is 0.008 wt%. The preparation method and process parameters during the preparation process all meet the requirements of this application. No rare earth oxides are formed. The scanning electron microscopy morphology of Comparative Example 1 is shown in Figure 5. As can be seen from the figure, the microstructure includes bainite and retained austenite. Figure 6 compares the phase transformation curves of Example 1 and Comparative Example 1. As can be seen from the figure, the phase transformation of the steel in Example 1 is faster. After 12 hours of isothermal treatment, the relative expansion curve is almost horizontal, indicating that the transformation is essentially complete. The phase transformation of the steel in Comparative Example 1 is slower, and the transformation is still not complete after 12 hours of isothermal treatment. This indicates that the presence of rare earth oxide particles significantly increases the bainite transformation rate compared to steel without rare earth oxide particles. Compared with Example 1, due to the low degree of bainite transformation, the steel prepared in Comparative Example 1 has a yield strength of 629 MPa, a tensile strength of 1360 MPa, and an elongation of 4.8%.

[0121] In Comparative Example 2, the steel composition does not meet the requirements of this application; the carbon content and chromium content ratio (C / Cr) is greater than 1. However, the preparation method and process parameters during the preparation process all meet the requirements of this application. Figure 7 is a scanning electron microscope image of the steel prepared in Comparative Example 2. As can be seen from the image, pearlite appears in the microstructure of the steel prepared in Comparative Example 2. Compared with Example 3, the yield strength, tensile strength, and elongation of Comparative Example 2 decrease to 561 MPa, 901 MPa, and 4.5%, respectively.

[0122] In Comparative Example 3, the steel preparation method does not meet the requirements of this application; vacuum induction smelting was employed. The heat treatment parameters were the same as those in Example 3. The scanning electron microscopy morphology of Comparative Example 3 is shown in Figure 8 . As can be seen, the microstructure consists of bainite and retained austenite, with virtually no rare earth oxides. Compared to Example 3, the yield strength, tensile strength, and elongation of Comparative Example 3 decreased to 733 MPa, 1459 MPa, and 7.2%, respectively.

[0123] In Comparative Example 4, the steel composition and preparation method and process parameters were the same as in Example 2. However, during preparation, the steel was austenitized at 870°C and the second ingot was isothermally treated for 5 hours, which did not meet the requirements of this application. Compared with Example 2, the yield strength, tensile strength, and elongation of Comparative Example 4 decreased to 712 MPa, 1421 MPa, and 6.2%, respectively.

[0124] The above is only a preferred specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in this application should be covered by the scope of protection of the present application.

Claims

1. A high-strength, high-carbon, bainite wear-resistant steel, characterized in that: The components are calculated by mass percentage as follows: C 0.65-0.90wt%, Si 1.0-1.55wt%, Mn 1.90-2.20wt%, Cr 0.70-0.95wt%, Ni 0.50-0.70wt%, Al 0.85-1.10wt%, O 0.001-0.0035wt% and Ce 0.01-0.03wt%, the ratio of C content to Cr content C / Cr is less than 1, and the rest is Fe and unavoidable impurities.

2. The high-strength high-carbon bainite wear-resistant steel according to claim 1, characterized in that: The components of the high-strength high-carbon bainite wear-resistant steel are, by mass percentage, C 0.67-0.90wt%, Si 1.06-1.55wt%, Mn 1.91-2.20wt%, Cr 0.72-0.95wt%, Ni 0.57-0.70wt%, Al 0.85-0.98wt%, O 0.0018-0.0035wt% and Ce 0.013-0.03wt%, the ratio of C content to Cr content C / Cr is less than 1, and the rest is Fe and unavoidable impurities.

3. The high-strength, high-carbon, bainite wear-resistant steel according to claim 1 or 2, characterized in that: The microstructure of the high-strength high-carbon bainite wear-resistant steel includes bainite ferrite and residual austenite, wherein the width of the bainite ferrite lath is less than 200 nm.

4. A method for preparing high-strength high-carbon bainite wear-resistant steel, used for preparing the high-strength high-carbon bainite wear-resistant steel according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: Weigh the alloy raw materials according to the proportion of wear-resistant steel alloy; S2: smelting, casting and forging the alloy raw materials to obtain a first steel ingot; S3: reheating the first steel ingot to 950-1030° C., keeping the temperature, and then cooling the ingot to the temperature of the low-temperature bainite phase transformation zone to obtain a second steel ingot; S4: isothermally treating the second steel ingot at 230-300° C., and then cooling to room temperature to obtain bainite wear-resistant steel.

5. The preparation method according to claim 4, characterized in that: In step S2, the smelting is non-vacuum induction smelting.

6. The preparation method according to claim 4, characterized in that: In step S2, the thickness of the first steel ingot is 15-30 mm.

7. The preparation method according to claim 4, characterized in that: In step S2, the first steel ingot contains rare earth oxides, and the volume fraction of the rare earth oxides is 0.1-0.2 vol%.

8. The preparation method according to claim 7, characterized in that: The rare earth oxide has a size of 0.5 to 3 μm.

9. The preparation method according to claim 4, characterized in that: In step S3, the holding time is 1.5-2 times of the thickness of the first steel ingot, in minutes.

10. The preparation method according to claim 4, characterized in that: In step S4, the isothermal treatment time is 6 to 12 hours.

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