A low-alloy wear-resistant steel with large thickness and high brinell hardness and a preparation method thereof

Abstract

The application discloses a low-alloy wear-resistant steel with large thickness and high Brinell hardness and a preparation method thereof, and chemical components and mass percentages of the low-alloy wear-resistant steel 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 is Fe and inevitable impurities. The application adopts reasonable component design, adopts high-carbon and alloying component design, and through mutual cooperation of carbon, manganese, chromium, nickel, molybdenum and other alloy elements and niobium, titanium and other micro-alloy elements, good hardness and low-temperature toughness matching are obtained.

Description

Technical Field

[0001] This invention relates to the field of steel production technology, and in particular to a thick, high-Brønsted-hardness low-alloy wear-resistant steel and its preparation method. Background Technology

[0002] Low-alloy wear-resistant steel, due to its high strength and hardness, good weldability, impact toughness, and formability, is widely used in industries such as engineering machinery, mining, construction, agriculture, cement, ports, power, and metallurgy. It is mainly used in the manufacture of bulldozers, loaders, excavators, dump trucks, ball mills, and various mining machinery. These components typically operate in extremely harsh environments with alternating wet and dry conditions, and replacement is difficult. Therefore, the steel plates must possess high strength, hardness, excellent wear resistance, and good weldability to ensure a longer service life for the equipment.

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

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a thick, high Brinell hardness low alloy wear-resistant steel and its preparation method.

[0005] To solve the above technical problems, the technical solution of the present invention is as follows:

[0006] A thick-walled, high-Brownian-hardness low-alloy wear-resistant steel has the following chemical composition and mass percentage: 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%, with the remainder being Fe and unavoidable impurities.

[0007] As a preferred embodiment of the thick, high Brinell hardness low-alloy wear-resistant steel described in this 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%.

[0008] This invention also provides a method for preparing thick, high-Brønsted hardness low-alloy wear-resistant steel, comprising the following steps in sequence: hot metal desulfurization pretreatment, converter smelting, LF+RH refining, continuous casting, billet stacking, billet heating, descaling, rolling, controlled cooling or air cooling, flaw detection, shot blasting, quenching, tempering, straightening, cutting, sampling, marking, inspection, and warehousing.

[0009] As a preferred embodiment of the preparation method of the thick, high Brinell hardness low alloy wear-resistant steel of the present invention, wherein: in the LF refining process, 30 kg of 30% rare earth iron alloy is added to the refining furnace.

[0010] In a preferred embodiment of the preparation method of the thick, high Brinell hardness low alloy wear-resistant steel of the present invention, the high vacuum treatment time in the RH refining process is greater than 30 min.

[0011] As a preferred embodiment of the preparation method of the thick, high Brinell hardness low alloy wear-resistant steel of the present invention, wherein: the continuous casting process adopts a double-cooling single-roller electromagnetic stirring with a current of 200-250A and a frequency of 6HZ.

[0012] As a preferred embodiment of the preparation method of the thick, high Brinell hardness low alloy wear-resistant steel of the present invention, wherein: in the rolling process, after the billet is heated to 1180-1220℃, it is rolled in the austenite recrystallization zone and the non-recrystallization zone respectively. The rolling in the recrystallization zone requires a reduction rate of ≥12% per pass. The rolling in the non-recrystallization zone has an initial rolling temperature of ≤950℃ and a final rolling temperature of ≥800℃. The cumulative reduction rate in the non-recrystallization zone is ≥30%.

[0013] In a preferred embodiment of the preparation method of the thick, high Brinell hardness low alloy wear-resistant steel of the present invention, the quenching temperature is 850-880℃ and the tempering temperature is 120-200℃.

[0014] In a preferred embodiment of the preparation method of the thick, high Brinell hardness low alloy wear-resistant steel of the present invention, the thickness of the casting in the continuous casting is 370-450 mm.

[0015] The beneficial effects of this invention are:

[0016] (1) The present invention adopts a reasonable composition design, adopts a high carbon and alloy composition design, and through the mutual cooperation of alloying elements such as carbon, manganese, chromium, nickel, molybdenum and micro-alloying elements such as niobium and titanium, the controlled rolling process produces wear-resistant steel with a thickness of 100mm. Through a reasonable offline heat treatment process, a good match between hardness and low temperature toughness is obtained.

[0017] (2) In this invention, the RH high vacuum treatment plus billet stacking treatment for more than 48 hours makes the H in the billet ≤ 0.0001%, which effectively reduces the risk of H delayed cracking in steel plate.

[0018] (3) The present invention uses 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.

[0019] (4) The continuous casting process in this invention adopts the double-cooling single-roller electromagnetic stirring technology, which effectively improves the uniformity of the composition and structure of the billet.

[0020] (5) The finished product of this invention has a thickness of 100mm. It adopts two-stage controlled rolling, with a cumulative reduction rate of ≥30% in the non-recrystallization zone and a thickness of ≥150mm for the hot-cast billet, ensuring that there is no significant difference in the microstructure from the surface to the core. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the near-surface resistance of a thick, high-Brownian hardness low-alloy wear-resistant steel provided by the present invention.

[0023] Figure 2 This is a schematic diagram of the microstructure of a 1 / 4 thickness of the thick, high Brinell hardness low alloy wear-resistant steel provided by the present invention. Detailed Implementation

[0024] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0025] This application provides a thick, high-Brownian hardness low-alloy wear-resistant steel with the following chemical composition and mass percentage: 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%, with the remainder being Fe and unavoidable impurities.

[0026] This application also provides a method for preparing a thick, high-Brønsted hardness low-alloy wear-resistant steel, which includes the following steps in sequence: hot metal desulfurization pretreatment, converter smelting, LF+RH refining, continuous casting, billet stacking, billet heating, descaling, rolling, controlled cooling or air cooling, flaw detection, shot blasting, quenching, tempering, straightening, cutting, sampling, marking, inspection, and warehousing.

[0027] The RH refining process involves high vacuum treatment for more than 30 minutes to reduce the H content in the molten steel, followed by billet stacking treatment for more than 48 hours to ensure that the H content in the billet is ≤0.0001%.

[0028] In the LF refining process, adding 30 kg of 30% rare earth iron alloy to the refining furnace effectively improves the type of inclusions, reduces the number of inclusions inside the molten steel, and improves the purity of the molten steel.

[0029] The continuous casting process employs a dual-cooling single-roller electromagnetic stirring technology with a current of 200-250A and a frequency of 6Hz. The thickness of the continuously cast billet is 450mm.

[0030] The billet is heated to 1180-1220℃ and then rolled in both the austenite recrystallization and non-recrystallization zones. The recrystallization zone rolling requires a reduction of 15% per pass. The non-recrystallization zone rolling requires an initial rolling temperature of 948℃, a final rolling temperature of 850℃, and a cumulative reduction of ≥30%. The billet thickness is controlled to ≥150mm during the initial heating phase, and the final rolled thickness is 100mm. After rolling, the billet is air-cooled to room temperature and then subjected to offline heat treatment, including a quenching temperature of 860℃, a tempering temperature of 200℃, and a holding time of 60min.

[0031] The thick, high Brinell hardness low-alloy wear-resistant steel prepared by the above method has a hardness of 520-570 HBW and a low-temperature impact toughness of ≥25J at -20℃.

[0032] Table 1 shows the performance parameters of the obtained thick, high Brinell hardness low alloy wear-resistant steel.

[0033]

[0034] Table 1

[0035] Therefore, the technical solution of this application adopts a reasonable composition design, a high carbon and alloy composition design, and through the synergistic effect of alloying elements such as carbon, manganese, chromium, nickel, and molybdenum, as well as microalloying elements such as niobium and titanium, a controlled rolling process is used to produce wear-resistant steel with a thickness of 100mm. Through a reasonable offline heat treatment process, a good match between hardness and low-temperature toughness is obtained.

[0036] In addition to the above embodiments, the present invention may have other implementation methods; all technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method of producing a low alloy abrasion resistant steel of large thickness and high Brinell hardness, characterized in that: The chemical composition and mass percentage of the low alloy wear-resistant steel with large thickness and high Brinell hardness 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 is Fe and inevitable impurities; The preparation method of the low alloy wear-resistant steel with large thickness and high Brinell hardness comprises the following steps in sequence: molten iron desulfurization pretreatment, converter smelting, LF+RH refining, continuous casting, casting blank stacking, casting blank heating, dephosphorization, rolling, controlled cooling or air cooling, flaw detection, shot blasting, quenching, tempering, straightening, cutting, sampling, identification spraying, inspection, and warehousing; In the LF refining process, 30 kg of 30% rare earth iron alloy is added into the refining furnace; in the RH refining process, the high vacuum treatment time is greater than 30 min; and in the continuous casting process, two-cooling single-roller electromagnetic stirring is adopted, the current is 200-250 A, and the frequency is 6 HZ. In the rolling process, the casting blank is heated to 1180-1220 ℃ and then rolled in the austenite recrystallization zone and the unrecrystallization zone respectively, the rolling reduction in the recrystallization zone is required to be ≥12%, the open rolling temperature in the unrecrystallization zone is ≤950 ℃, the finish rolling temperature is ≥800 ℃, and the cumulative rolling reduction in the unrecrystallization zone is ≥30%; and the warm casting blank thickness is controlled to be ≥150 mm, and the final rolling thickness is 100 mm.

2. A method of producing a low alloy wear resistant steel of large thickness and high Brinell hardness according to claim 1, characterized in that: The 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%, and RE: ≥0.0010%.

3. The method of producing a low alloy abrasion resistant steel of high Brinell hardness at large thickness according to claim 1, characterized in that: The quenching temperature is 850-880 ℃, and the tempering temperature is 120-200 ℃.

4. The method of producing a low alloy abrasion resistant steel of high Brinell hardness at large thickness according to claim 1, characterized in that: The casting blank thickness of the continuous casting is 370-450 mm.

Images