Large-thickness high-brinell-hardness low-alloy wear-resistant steel and preparation method thereof

Abstract

The invention discloses large-thickness high-brinell-hardness low-alloy wear-resistant steel and a preparation method thereof. The steel comprises the following chemical components in percentage by mass: 0.90-1.20% of Cr, 0.80-1.2% of Ni, 0.008-0.030% of Ti, 0.015-0.050% of Nb, 0.0008-0.0025% of B, less than or equal to 0.0040% of N, less than or equal to 0.0025% of O, 0.34-0.38% of C, 0.10-0.30% of Si, 0.35-0.70% of Mn, less than 0.20% of Mo, less than or equal to 0.010% of P, less than or equal to 0.0015% of S, less than or equal to 0.0001% of H, more than or equal to 0.0010% of Re and the balance of Fe and inevitable impurities. Reasonable component design is adopted, high-carbon and alloying component design is adopted, alloy elements such as carbon, manganese, chromium, nickel and molybdenum and microalloy elements such as niobium and titanium are matched with one another, and good hardness and low-temperature toughness matching is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, in particular to a low-alloy wear-resistant steel with large thickness and high Brinell hardness and a preparation method thereof. Background Art

[0002] Low alloy wear-resistant steel is widely used in engineering machinery, mining, construction, agriculture, cement, ports, electricity, metallurgy and other industries due to its high strength and hardness, good weldability, good impact toughness and formability. It is mainly used to manufacture bulldozers, loaders, excavators, dump trucks, ball mills and various mining machinery. Such parts generally work in extremely harsh conditions of dry and wet environments, and are difficult to replace. The steel plate is required to have high strength, hardness, excellent wear resistance, and good welding performance to ensure a longer service life of the equipment.

[0003] In the past 10 years, domestic low-alloy wear-resistant steel has developed rapidly, and the number of companies capable of producing thin-gauge NM360-NM500 has gradually increased. However, high-grade NM550, especially thick-gauge NM550, is very prone to cracking during production and user processing and use, and there are few companies that can produce it stably. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the disadvantages of the prior art and provide a low-alloy wear-resistant steel with large thickness and high Brinell hardness and a preparation method thereof.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows: A low-alloy wear-resistant steel with large thickness and high Brinell hardness, whose chemical composition and mass percentage are as follows: Cr: 0.90-1.20%, Ni: 0.80-1.2%, Ti: 0.008-0.030%, Nb: 0.015-0.050%, B: 0.0008-0.0025%, N≤0.0040%, O≤0.0025%, C: 0.34-0.38%, Si: 0.10-0.30%, Mn: 0.35-0.70%, Mo: <0.20%, P≤0.010%, S≤ 0.0015%, H≤0.0001%, Re: ≥0.0010%, and the rest are Fe and unavoidable impurities.

[0006] As a preferred embodiment of the low-alloy wear-resistant steel with large thickness and high Brinell hardness described in the present invention, its chemical composition and mass percentage are as follows: Cr: 1.0%, Ni: 1.20%, Ti: 0.008-0.030%, Nb: 0.015-0.030%, B: 0.0008-0.0025%, N≤0.0040%, O≤0.0025%, C: 0.38%, Si: 0.30%, Mn: 0.55%, Mo: 0.08%, P≤0.010%, S≤0.0013%, H≤0.0001%, Re: ≥0.0010%.

[0007] The present invention also provides a method for preparing low-alloy wear-resistant steel with large thickness and high Brinell hardness, which comprises the following steps in sequence: molten iron desulfurization pretreatment, converter smelting, LF+RH refining, continuous casting, ingot stacking, ingot heating, dephosphorization, rolling, controlled cooling or air cooling, flaw detection, shot blasting, quenching, tempering, straightening, cutting, sampling, printing identification, inspection, and warehousing.

[0008] As a preferred solution of the method for preparing the thick and high Brinell hardness low alloy wear-resistant steel of the present invention, in the LF refining process, 30 kg of 30% rare earth iron alloy is added into the refining furnace.

[0009] As a preferred solution of the method for preparing thick low-alloy wear-resistant steel with high Brinell hardness described in the present invention, the high vacuum treatment time in the RH refining process is greater than 30 minutes.

[0010] As a preferred solution of the method for preparing thick low-alloy wear-resistant steel with high Brinell hardness described in the present invention, the continuous casting process adopts secondary cooling single-roller electromagnetic stirring, the current is 200-250A, and the frequency is 6HZ.

[0011] As a preferred embodiment of the method for preparing thick and high Brinell hardness low-alloy wear-resistant steel according to the present invention, in the rolling process, the ingot is heated to 1180-1220°C and then rolled in the austenite recrystallization zone and the non-recrystallization zone respectively, the rolling in the recrystallization zone requires a pass reduction rate of ≥12%, the starting rolling temperature of the non-recrystallization zone rolling is ≤950°C, the final rolling temperature is ≥800°C, and the cumulative rolling reduction rate of the non-recrystallization zone rolling is ≥30%.

[0012] As a preferred solution of the method for preparing the thick and high Brinell hardness low alloy wear-resistant steel of the present invention, the quenching temperature is 850-880°C, and the tempering temperature is 120-200°C.

[0013] As a preferred solution of the method for preparing thick low-alloy wear-resistant steel with high Brinell hardness described in the present invention, the casting thickness of the continuous casting is 370-450mm.

[0014] The beneficial effects of the present invention are: (1) The present invention adopts reasonable composition design, high carbon and alloying composition design, and through the mutual cooperation of alloy elements such as carbon, manganese, chromium, nickel, molybdenum and micro-alloying elements such as niobium and titanium, the controlled rolling process is used to produce wear-resistant steel with a thickness of 100 mm, and through a reasonable offline heat treatment process, a good match between hardness and low-temperature toughness is obtained.

[0015] (2) In the present invention, the RH high vacuum treatment plus the ingot stacking treatment for more than 48 hours makes the H in the ingot ≤ 0.0001%, effectively reducing the risk of H delayed cracking of the steel plate.

[0016] (3) The present invention adopts the LF refining process to add 30 kg of 30% rare earth iron alloy, which effectively improves the type of inclusions, reduces the number of inclusions in the molten steel, and improves the purity of the molten steel.

[0017] (4) The continuous casting process of the present invention adopts the secondary cooling single-roller electromagnetic stirring technology, which effectively improves the uniformity of the composition and structure of the ingot.

[0018] (5) The thickness of the finished product of the present invention is 100 mm. Two-stage controlled rolling is adopted, the cumulative rolling reduction rate in the non-recrystallization zone is ≥30%, and the thickness of the warm-cast billet is controlled at ≥150 mm to ensure that there is no obvious difference in the structure from the surface to the core. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0020] Figure 1 A schematic diagram of the near-surface resistance of a low-alloy wear-resistant steel with a large thickness and high Brinell hardness provided by the present invention; Figure 2 This is a schematic diagram of the 1 / 4 thickness organization of the thick, high Brinell hardness, low-alloy wear-resistant steel provided by the present invention. DETAILED DESCRIPTION

[0021] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific implementation modes and in combination with the accompanying drawings.

[0022] The embodiment of the present application provides a low-alloy wear-resistant steel with large thickness and high Brinell hardness, whose chemical composition and mass percentage are as follows: C: 0.38%, Si: 0.30%, Mn: 0.55%, P≤0.010%, S≤0.0013%, Cr: 1.0%, Mo: 0.08%, Ni: 1.20%, Ti: 0.008-0.030%, Nb: 0.015-0.030%, B: 0.0008-0.0025%, Re: 0.0015%, N≤0.0040%, O≤0.0025%, H≤0.0001%, and the rest are Fe and unavoidable impurities.

[0023] The embodiment of the present application also provides a method for preparing low-alloy wear-resistant steel with large thickness and high Brinell hardness, which comprises the following steps in sequence: molten iron desulfurization pretreatment, converter smelting, LF+RH refining, continuous casting, ingot stacking, ingot heating, dephosphorization, rolling, controlled cooling or air cooling, flaw detection, shot blasting, quenching, tempering, straightening, cutting, sampling, printing identification, inspection, and warehousing.

[0024] The RH refining process uses high vacuum treatment for more than 30 minutes to reduce the H content in the molten steel, and then the ingots are stacked for more than 48 hours to make the H content in the ingots ≤ 0.0001%.

[0025] In the LF refining process, 30 kg of 30% rare earth iron alloy is added to the refining furnace, which effectively improves the type of inclusions, reduces the number of inclusions inside the molten steel, and improves the purity of the molten steel.

[0026] The continuous casting process adopts the secondary cooling single roller electromagnetic stirring technology, the current is 200-250A, the frequency is 6HZ. The continuous casting billet thickness is 450mm.

[0027] After the ingot is heated at 1180-1220℃, it is rolled in the austenite recrystallization zone and the non-recrystallization zone. Among them, the rolling in the recrystallization zone requires a pass reduction rate of 15%. The rolling in the non-recrystallization zone requires a starting rolling temperature of 948℃, a final rolling temperature of 850℃, and a cumulative rolling reduction rate of ≥30% in the non-recrystallization zone. The thickness of the warm ingot is controlled at ≥150mm, and the final rolling thickness is 100mm. After rolling, it is air-cooled to room temperature, and then offline heat treatment is carried out, wherein the quenching temperature is 860℃, the tempering temperature is 200℃, and the holding time is 60min.

[0028] The thick low-alloy wear-resistant steel with high Brinell hardness prepared by the above method has a hardness of 520-570 HBW and a low-temperature impact toughness of ≥25J at -20°C.

[0029] Table 1 shows the performance parameters of the produced low alloy wear-resistant steel with large thickness and high Brinell hardness.

[0030]

[0031] Table 1 Therefore, the technical solution of the present application adopts a reasonable composition design, a high-carbon and alloyed composition design, and through the mutual coordination of alloy elements such as carbon, manganese, chromium, nickel, molybdenum, and micro-alloy elements such as niobium and titanium, a controlled rolling process is used to produce wear-resistant steel with a thickness of 100 mm, and a good match of hardness and low-temperature toughness is obtained through a reasonable offline heat treatment process.

[0032] In addition to the above embodiments, the present invention may also have other implementation modes; any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. A low alloy wear-resistant steel with large thickness and high Brinell hardness, characterized in that: Its chemical composition and mass percentage are as follows: Cr: 0.90-1.20%, Ni: 0.80-1.2%, Ti: 0.008-0.030%, Nb: 0.015-0.050%, B: 0.0008-0.0025%, N≤0.0040%, O≤0.0025%, C: 0.34-0.38%, Si: 0.10-0.30%, Mn: 0.35-0.70%, Mo: <0.20%, P≤0.010%, S≤ 0.0015%, H≤0.0001%, Re: ≥0.0010%, and the rest are Fe and unavoidable impurities.

2. The thick low alloy wear-resistant steel with high Brinell hardness according to claim 1 is characterized in that: Its chemical composition and mass percentage are as follows: Cr: 1.0%, Ni: 1.20%, Ti: 0.008-0.030%, Nb: 0.015-0.030%, B: 0.0008-0.0025%, N≤0.0040%, O≤0.0025%, C: 0.38%, Si: 0.30%, Mn: 0.55%, Mo: 0.08%, P≤0.010%, S≤0.0013%, H≤0.0001%, Re: ≥0.0010%.

3. A method for preparing a thick and high Brinell hardness low alloy wear-resistant steel according to claim 1, characterized in that: The following processes are included in sequence: molten iron desulfurization pretreatment, converter smelting, LF+RH refining, continuous casting, ingot stacking, ingot heating, dephosphorization, rolling, controlled cooling or air cooling, flaw detection, shot blasting, quenching, tempering, straightening, cutting, sampling, printing identification, inspection, and warehousing.

4. The method for preparing thick low alloy wear-resistant steel with high Brinell hardness according to claim 3, characterized in that: In the LF refining process, 30 kg of 30% rare earth iron alloy is added into the refining furnace.

5. The method for preparing thick low alloy wear-resistant steel with high Brinell hardness according to claim 3, characterized in that: The high vacuum treatment time in the RH refining process is greater than 30 minutes.

6. The method for preparing thick low alloy wear-resistant steel with high Brinell hardness according to claim 3, characterized in that: The continuous casting process adopts secondary cooling single roller electromagnetic stirring, the current is 200-250A, and the frequency is 6HZ.

7. The method for preparing thick low alloy wear-resistant steel with high Brinell hardness according to claim 3, characterized in that: In the rolling process, after the ingot is heated to 1180-1220°C, it is rolled in the austenite recrystallization zone and the non-recrystallization zone respectively. The rolling in the recrystallization zone requires a pass reduction rate of ≥12%, the starting rolling temperature of the non-recrystallization zone rolling is ≤950°C, the final rolling temperature is ≥800°C, and the cumulative rolling reduction rate of the non-recrystallization zone rolling is ≥30%.

8. The method for preparing thick low alloy wear-resistant steel with high Brinell hardness according to claim 3, characterized in that: The quenching temperature is 850-880°C, and the tempering temperature is 120-200°C.

9. The method for preparing thick low alloy wear-resistant steel with high Brinell hardness according to claim 3, characterized in that: The casting thickness of the continuous casting is 370-450mm.

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