Low-alloy high-wear-resistance steel and preparation method thereof

Abstract

The invention discloses low-alloy high-wear-resistance steel and a preparation method thereof, and relates to the field of metal materials, the low-alloy high-wear-resistance steel comprises the following chemical components in percentage by weight: 0.3-0.6% of C, 1.0-1.5% of Mn, 0.5-2.0% of Cr, 0.2-0.5% of Mo, 0.3-0.8% of S i, 0.001-0.005% of B, 0.03-0.06% of Nb, 0.05-0.12% of V and the balance of Fe and inevitable impurities, the content of Cu in the impurities is smaller than or equal to 0.15%, and the content of Sn in the impurities is smaller than or equal to 0.05%; according to the low-alloy high-wear-resistance steel and the preparation method thereof, the cost of the raw materials is reduced through synergistic matching of the regenerated waste steel and the high-purity pig iron, and meanwhile the addition amount of precious metal Cr and Mo is reduced; through a controlled rolling and controlled cooling process and microalloying, synergistic strengthening of a nanoscale NbC and VC precipitated phase and a bainite / martensite complex phase structure in a matrix is achieved.

Description

Technical Field

[0001] The present invention relates to metal material technology, in particular to a low-alloy high-wear-resistant steel and a preparation method thereof. Background Art

[0002] Steel is an iron-carbon alloy with a carbon content ranging from 0.02% to 2.11%. The main element is iron, and the carbon content determines its properties. Steels with a carbon content below 1.7% are called carbon steels. Adding alloying elements such as manganese, nickel, and chromium (total content ≤5% is low-alloy steel, 5%-10% is medium-alloy steel, and >10% is high-alloy steel) enhances properties such as corrosion resistance and high-temperature resistance.

[0003] Although existing high wear-resistant steels (such as high manganese steel and high chromium cast iron) have high hardness, they have the following problems:

[0004] High alloy cost: Relying on a large amount of precious metals such as Cr and Mo, which is not economical;

[0005] Insufficient toughness: high carbon and high alloy lead to high brittleness and easy cracking;

[0006] Complex process: requires multiple heat treatments or surface strengthening, and high energy consumption.

[0007] In recent years, low alloy wear-resistant steel has achieved performance improvement through microalloying and microstructure control, but the following problems still exist:

[0008] The utilization rate of recycled scrap steel is low, and impurity elements (Cu, Sn) are prone to cause hot brittleness;

[0009] Traditional rolling processes make it difficult to achieve both grain refinement and nano-precipitation control;

[0010] The bonding strength between the surface hardened layer and the substrate is insufficient and it is easy to peel off. Summary of the Invention

[0011] The object of the present invention is to provide a low alloy high wear resistant steel and a preparation method thereof, so as to solve the above-mentioned deficiencies in the prior art.

[0012] In order to achieve the above object, the present invention provides the following technical solution: a low alloy high wear-resistant steel comprising the following chemical components in weight percentage:

[0013] C 0.3-0.6%, Mn 1.0-1.5%, Cr 0.5-2.0%, Mo 0.2-0.5%, Si 0.3-0.8%, B0.001-0.005%, Nb 0.03-0.06%, V 0.05-0.12%, the balance is Fe and unavoidable impurities, among which the Cu content in the impurities is ≤0.15% and Sn ≤0.05%.

[0014] Furthermore, the metallographic structure of the low-alloy high-wear-resistant steel is a complex phase structure of bainite and martensite, the grain size is 5-10 μm, and NbC and VC precipitates with a size of 10-50 nm are dispersed in the matrix.

[0015] A method for preparing low-alloy high-wear-resistant steel comprises the following steps:

[0016] S1. Select recycled scrap steel accounting for 60-80% by weight of the steel raw material, remove Cu and Sn impurities through magnetic separation, and then shot blast the recycled scrap steel at a shot blasting pressure of 0.4-0.6 MPa and a steel shot diameter of 1.0-2.0 mm; select high-purity pig iron with a carbon content of 3.5-4.0%, sulfur ≤0.010%, and phosphorus ≤0.020% accounting for 20-40% by weight of the steel raw material, put it into a vacuum induction furnace for melting, evacuate to a pressure ≤0.5 Pa, heat to 1550-1600° C., add 0.02-0.05wt% of Al blocks, keep warm for 10-15 minutes, then heat to 1600-1650° C., add 0.1-0.3wt% of Ca-Si alloy and stir for 5-10 minutes to obtain molten steel;

[0017] S2, rolling the smelted steel of S1 through a four-roll reversible hot rolling mill at 1000-1100° C. in 3-5 passes, with a single-pass reduction of 15-20%, a cumulative reduction of 50-60%, and a rolling interval of ≤30 seconds to obtain rough-rolled steel;

[0018] S3, rolling the rough-rolled steel of S2 in the non-recrystallization zone at 800-900°C for 2-3 passes with a cumulative reduction of 30-40% and a final rolling temperature of 780-820°C to obtain a finished steel;

[0019] S4, cooling the finished steel of S3 to 450-550°C at a rate of 30-50°C / s within 10 seconds after rolling by high-pressure water mist spraying, and then slowly cooling to room temperature at a rate of 5-10°C / s;

[0020] S5. Temper the cooled steel of S4 at 600-650°C for 1-2 hours to precipitate NbC and VC carbides to obtain low alloy wear-resistant steel.

[0021] Furthermore, after the S5 tempering treatment, the low alloy wear-resistant steel is subjected to nitriding treatment, wherein the nitriding medium is ammonia, the nitriding temperature is 500-550° C., the nitriding time is 4-8 hours, the nitriding layer depth is 0.1-0.3 mm, and the surface hardness is ≥HV 1000.

[0022] Furthermore, after the S5 tempering treatment, the low alloy wear-resistant steel is subjected to laser cladding surface strengthening, the cladding material is Fe-Cr-B-Si alloy powder, the laser power is 2-4kW, the scanning speed is 5-10mm / s, the cladding layer hardness is ≥HRC 60, and the thickness is 0.5-2.0mm.

[0023] Furthermore, the S5 tempering treatment is a two-step tempering:

[0024] Step 1: Tempering at 200-300℃ for 1 hour to eliminate residual stress;

[0025] Step 2: Tempering at 600-650℃ for 1 hour to promote carbide precipitation.

[0026] Furthermore, the molar ratio of V to C in the VC precipitated phase is 1:0.8-1:1.2.

[0027] Compared with the prior art, the present invention provides a low-alloy high-wear-resistant steel and a preparation method thereof, which reduces the cost of raw materials and reduces the amount of Cr and Mo precious metals added by synergistically proportioning recycled scrap steel and high-purity pig iron;

[0028] Through controlled rolling and controlled cooling process and microalloying, the synergistic strengthening of nano-scale NbC and VC precipitation phases and bainite / martensite multiphase structure in the matrix is ​​achieved;

[0029] Through dynamic recrystallization rough rolling and non-recrystallization area finishing rolling, grain refinement and dislocation density control are achieved, thereby improving impact toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments described in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0031] Figure 1 The preparation flow chart provided in this embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] Example 1:

[0034] A low alloy high wear resistant steel comprising the following chemical components in weight percentage:

[0035] C 0.3-0.6%, Mn 1.0-1.5%, Cr 0.5-2.0%, Mo 0.2-0.5%, Si 0.3-0.8%, B0.001-0.005%, Nb 0.03-0.06%, V 0.05-0.12%, the balance is Fe and unavoidable impurities, among which the Cu content in the impurities is ≤0.15% and Sn ≤0.05%.

[0036] Example 2:

[0037] See also Figure 1 , a method for preparing low-alloy high-wear-resistant steel, comprising the following steps:

[0038] S1. Select recycled scrap steel accounting for 60-80% by weight of the steel raw material, remove Cu and Sn impurities through magnetic separation, and then shot blast the recycled scrap steel at a shot blasting pressure of 0.4-0.6 MPa and a steel shot diameter of 1.0-2.0 mm; select high-purity pig iron with a carbon content of 3.5-4.0%, sulfur ≤0.010%, and phosphorus ≤0.020% accounting for 20-40% by weight of the steel raw material, put it into a vacuum induction furnace for melting, evacuate to a pressure ≤0.5 Pa, heat to 1550-1600° C., add 0.02-0.05wt% of Al blocks, keep warm for 10-15 minutes, then heat to 1600-1650° C., add 0.1-0.3wt% of Ca-Si alloy and stir for 5-10 minutes to obtain molten steel;

[0039] S2. The smelted steel of S1 is rolled in 3-5 passes at 1000-1100° C. on a four-roll reversible hot rolling mill, with a single-pass reduction rate of 15-20%, a cumulative reduction rate of 50-60%, and a rolling interval of ≤30 seconds to obtain rough-rolled steel; dynamic recrystallization is promoted to refine austenite.

[0040] S3, rolling the rough-rolled steel of S2 in the non-recrystallized region at 800-900°C for 2-3 passes with a cumulative reduction of 30-40% and a final rolling temperature of 780-820°C to obtain a finished steel; rolling in the austenite non-recrystallized region to induce precipitation through dislocation accumulation and strain;

[0041] S4, cooling the finished steel of S3 to 450-550°C at a rate of 30-50°C / s within 10 seconds after rolling by high-pressure water mist spraying, and then slowly cooling to room temperature at a rate of 5-10°C / s;

[0042] S5. Temper the cooled steel of S4 at 600-650°C for 1-2 hours to precipitate NbC and VC carbides to obtain low alloy wear-resistant steel.

[0043] After S5 tempering treatment, the low alloy wear-resistant steel is nitrided. The nitriding medium is ammonia, the nitriding temperature is 500-550℃, the nitriding time is 4-8 hours, the nitriding layer depth is 0.1-0.3mm, and the surface hardness is ≥HV 1000.

[0044] After S5 tempering treatment, the low alloy wear-resistant steel is subjected to laser cladding surface strengthening. The cladding material is Fe-Cr-B-Si alloy powder, the laser power is 2-4kW, the scanning speed is 5-10mm / s, the cladding layer hardness is ≥HRC 60, and the thickness is 0.5-2.0mm.

[0045] S5 tempering treatment is a two-step tempering:

[0046] Step 1: Tempering at 200-300℃ for 1 hour to eliminate residual stress;

[0047] Step 2: Tempering at 600-650℃ for 1 hour to promote carbide precipitation.

[0048] The molar ratio of V to C in the VC precipitated phase is 1:0.8-1:1.2.

[0049] Example 3:

[0050] Raw material selection: C 0.45%, Mn 1.2%, Cr 1.0%, Mo 0.3%, Si 0.6%, Nb 0.05%, V0.08%, B 0.003%, Fe balance.

[0051] Preparation steps: 70% recycled scrap steel and 30% high-purity pig iron are smelted in a vacuum induction furnace, 0.03% Al is added for deoxidation and 0.2% Ca-Si alloy is added for purification during the smelting process, rough rolling is performed at 1050°C, 4 passes, and a reduction rate of 58%, and then finishing rolling is performed at 850°C, 3 passes, and a reduction rate of 35%. After rolling, the steel is cooled to 500°C with water mist at a rate of 40°C / s within 8 seconds and then slowly cooled to room temperature at 8°C / s, and tempered at 620°C for 1.5 hours;

[0052] Post-treatment: Nitriding treatment was performed at 540℃ for 6h with an ammonia flow rate of 2L / min. The obtained low alloy wear-resistant steel was subjected to performance testing. The parameters are shown in Table 1 below:

[0053] Test items Test results Test standards Matrix hardness (HRC) 52 ASTME18 Surface hardness (HV) 1050 ISO6507 Impact toughness (-20℃, J) 58 ASTME23 <![CDATA[Wear resistance (volume loss, mm 3 )]]> 120 (Compared to high manganese steel: 205) ASTMG65

[0054] Table 1

[0055] Example 4:

[0056] Raw material selection: C 0.55%, Mn 1.4%, Cr 1.8%, Mo 0.4%, Si 0.7%, Nb 0.06%, V0.11%, B 0.004%, Fe balance.

[0057] The preparation steps are the same as those in Example 3;

[0058] Post-processing: Laser cladding process was used. The specific parameters were as follows: Fe-Cr-B-Si alloy powder was used as cladding material. Under the condition of 3kW laser power, the surface treatment was carried out at a scanning speed of 8mm / s. Finally, a cladding layer with a thickness of 1.2mm was formed. The performance of the obtained low-alloy wear-resistant steel was tested. The parameters are shown below.

[0059] Table 2:

[0060]

[0061] Table 2

[0062] Embodiment 5:

[0063] The material composition is consistent with that of Example 3. The preparation process is as follows: first, the same rolling and cooling process as in Example 3 is used for preliminary forming, followed by a two-stage tempering treatment: in the first stage, the material is kept at 250°C for 1 hour to eliminate residual stress, and in the second stage, the material is heated to 600°C and kept for 1 hour to promote uniform precipitation of carbides. Finally, the same post-treatment method as in Example 3 is used to perform performance tests on the obtained low-alloy wear-resistant steel. The parameters are shown in Table 3 below:

[0064] Performance indicators Two-step tempering Single-step tempering Residual stress (MPa) 85 220 Impact toughness (J) 64 58 Wear resistance (volume loss) 115 120

[0065] Table 3

[0066] Example 6:

[0067] The material composition is consistent with that in Example 3. The preparation steps are as follows: the finishing rolling temperature in Example 3 is changed to 780°C; the post-processing method is consistent with that in Example 3; the performance test of the obtained low alloy wear-resistant steel is carried out; the parameters are shown in Table 4 below:

[0068] parameter 780℃ finishing rolling 850℃ finishing rolling Grain size (μm) 6.2 8.5 <![CDATA[Precipitate phase density (number / μm 2 )]]> 120 85 Matrix hardness (HRC) 54 52

[0069] Table 4

[0070] Embodiment seven:

[0071] The material preparation process is as follows: the raw material selection and preparation steps are consistent with Example 3, and the subsequent surface treatment adopts a composite process: first, nitriding treatment is performed at a temperature of 520°C for 5 hours to form a 0.15mm thick nitrided layer with a hardness of HV980; then a laser cladding process is performed to deposit a 0.8mm thick cladding layer on the substrate surface. The performance of the obtained low-alloy wear-resistant steel is tested, and the parameters are shown in Table 5 below:

[0072] index Composite processing Single Processing Surface hardness gradient (HV) 1000→600 Sudden drop (e.g. 1050→400) Peeling resistance (number of cycles) ＞5000 3000-4000

[0073] Table 5

[0074] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims.

Claims

1. A low alloy high wear resistant steel, characterized in that: The chemical composition includes the following weight percentages: C 0.3-0.6%, Mn 1.0-1.5%, Cr 0.5-2.0%, Mo 0.2-0.5%, Si 0.3-0.8%, B 0.001-0.005%, Nb 0.03-0.06%, V 0.05-0.12%, the balance is Fe and impurities, among which the Cu content in the impurities is ≤0.15% and Sn ≤0.05%.

2. The low alloy high wear resistant steel according to claim 1, characterized in that: The metallographic structure of the low-alloy high-wear-resistant steel is a complex phase structure of bainite and martensite, the grain size is 5-10 μm, and NbC and VC precipitate phases with a size of 10-50 nm are dispersed in the matrix.

3. A method for preparing low-alloy high-wear-resistant steel, which is applicable to the low-alloy wear-resistant steel according to any one of claims 1-2, characterized in that: The following steps are involved: S1. Select steel raw materials, wherein the steel raw materials include recycled scrap steel and high-purity pig iron, and the recycled scrap steel accounts for 60-80% by weight of the steel raw materials. After magnetic separation and sorting to remove Cu and Sn impurities, the recycled scrap steel is shot blasted at a shot blasting pressure of 0.4-0.6 MPa and a steel shot diameter of 1.0-2.0 mm. Select high-purity pig iron with a carbon content of 3.5-4.0%, sulfur ≤0.010%, and phosphorus ≤0.020%, which accounts for 20-40% by weight of the steel raw materials, and put it into a vacuum induction furnace for melting. Evacuate to a pressure ≤0.5 Pa, heat to 1550-1600° C., add 0.02-0.05wt% of Al blocks, keep warm for 10-15 minutes, then heat to 1600-1650° C., add 0.1-0.3wt% of Ca-Si alloy and stir for 5-10 minutes to obtain molten steel. S2, rolling the smelted steel of S1 through a four-roll reversible hot rolling mill at 1000-1100° C. in 3-5 passes, with a single-pass reduction of 15-20%, a cumulative reduction of 50-60%, and a rolling interval of ≤30 seconds to obtain rough-rolled steel; S3, rolling the rough-rolled steel of S2 in the non-recrystallization zone at 800-900°C for 2-3 passes with a cumulative reduction of 30-40% and a final rolling temperature of 780-820°C to obtain a finished steel; S4, cooling the finished steel of S3 to 450-550°C at a rate of 30-50°C / s within 10 seconds after rolling by high-pressure water mist spraying, and then slowly cooling to room temperature at a rate of 5-10°C / s; S5. Temper the cooled steel of S4 at 600-650°C for 1-2 hours to precipitate NbC and VC carbides to obtain low alloy wear-resistant steel.

4. The method for preparing low alloy high wear resistant steel according to claim 3, characterized in that: After the S5 tempering treatment, the low alloy wear-resistant steel is subjected to nitriding treatment, wherein the nitriding medium is ammonia, the nitriding temperature is 500-550° C., the nitriding time is 4-8 hours, the nitriding layer depth is 0.1-0.3 mm, and the surface hardness is ≥HV 1000.

5. The method for preparing low alloy high wear resistant steel according to claim 3, characterized in that: After the S5 tempering treatment, the low alloy wear-resistant steel is subjected to laser cladding surface strengthening, the cladding material is Fe-Cr-B-Si alloy powder, the laser power is 2-4kW, the scanning speed is 5-10mm / s, the cladding layer hardness is ≥HRC 60, and the thickness is 0.5-2.0mm.

6. The method for preparing low alloy high wear resistant steel according to claim 3, characterized in that: The S5 tempering treatment is a two-step tempering: Step 1: Tempering at 200-300℃ for 1 hour to eliminate residual stress; Step 2: Tempering at 600-650℃ for 1 hour to promote carbide precipitation.

7. The method for preparing low alloy high wear resistant steel according to claim 3, characterized in that: The molar ratio of V to C in the VC precipitated phase is 1:0.8-1:1.2.

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