Production method of high-hardness and high-toughness wear-resistant steel plate

Abstract

The invention discloses a production method of a high-hardness and high-toughness wear-resistant steel plate. The production process comprises the steps of molten iron pretreatment, converter treatment, LF and RH / VD refining, continuous casting, heating, rolling, finishing and quenched-tempered heat treatment. The steel plate comprises the following chemical components in percentage by weight: 0.2-0.35% of C, 0.5-2.0% of Mn, 0.5-1.5% of Si, less than or equal to 1.0% of Ni, less than or equal to 2.0% of Cr, 0.2-1.5% of Mo, less than or equal to 0.5% of Cu, less than or equal to 0.020% of P, less than or equal to 0.005% of S, 0.001-0.005% of B and the balance of Fe and inevitable impurity elements. According to the invention, a multi-phase composite structure of tempered martensite, tempered bainite and retained austenite is realized by combining novel alloy component design with controlled rolling and heat treatment processes, and the high-hardness and high-toughness wear-resistant steel plate with yield strength greater than or equal to 1150 MPa, tensile strength greater than or equal to 1450 MPa, total elongation greater than or equal to 10%, brinell hardness greater than or equal to 460 HBW and ballistic energy greater than or equal to 40 J at-20 DEG C is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel material manufacturing, and relates to a high-hardness and high-toughness wear-resistant steel plate containing residual austenite and a production method thereof. BACKGROUND

[0002] With the global industrialization, especially the development of large-scale, automation and intensification of the mining, cement, building materials, metallurgy, energy and engineering machinery industries, the wear-resistant conditions faced by equipment are increasingly severe. According to statistics, in the mining, power and other industries, the equipment failure and material consumption caused by wear account for a considerable proportion of the total cost, and the replacement of key parts due to wear will cause huge production losses. Ordinary carbon steel and low alloy steel cannot meet the requirements under strong impact or high stress wear conditions, and frequent replacement of parts not only has high material cost, but also brings huge labor, downtime and time cost. Therefore, the market urgently needs a new type of steel plate that can significantly prolong the service life of equipment, reduce downtime and reduce the overall operating cost. In addition to the high hardness of the new high-hardness and high-toughness wear-resistant steel containing a proper amount of residual austenite, the residual austenite can also increase toughness and further improve hardness by dynamic phase change to martensite. SUMMARY

[0003] The application aims to provide a production method of a high-hardness and high-toughness wear-resistant steel plate containing residual austenite, which obtains a high-hardness and high-toughness wear-resistant steel plate through alloy composition design, spherical inclusions, reduction of gas element content and proper heat treatment.

[0004] The technical scheme of the application is as follows: A production method of a high-hardness and high-toughness wear-resistant steel plate, the production process includes molten iron pretreatment-converter-LF and RH / VD refining-continuous casting-heating-rolling-finishing-quenching and tempering heat treatment, the chemical composition of the steel is C=0.2-0.35%, Mn=0.5-2.0%, Si=0.5-1.5%, Ni≤1.0%, Cr≤2.0%, Mo=0.2-1.5%, Cu≤0.5%, P≤0.020%, S≤0.005%, B=0.001-0.005%, and the rest is Fe and inevitable impurity elements; the key process steps include: (1) RH / VD furnace: vacuum degree ≤80Pa, vacuum holding time ≥10 minutes and 12 minutes respectively, and pure calcium wire ≥100m is fed after vacuum treatment; (2) Continuous casting: billet off-line temperature ≥400℃, and the billet is stack-cooled in a slow cooling pit or a heat preservation cover for ≥48 hours; (3) Heating: the continuous casting billet needs to be preheated before entering the heating furnace, and the preheating temperature is ≥200℃; (4) Rolling: two-stage rolling is adopted, the rough rolling starting temperature is ≥1050℃, the single pass reduction rate is ≥10%, the rolling times are ≥2, the fine rolling starting temperature is 850-950℃, the final rolling temperature is 700-850℃, and the rolled steel plate is directly air-cooled without water cooling; (5) Quenching and tempering heat treatment: quenching + tempering process is adopted, the quenching temperature is 850-950℃, the tempering temperature is 170-300℃, the obtained steel plate has a yield strength ≥1150MPa, a tensile strength ≥1450MPa, a total elongation ≥10%, a Brinell hardness ≥460HBW, and an impact energy at-20℃ ≥40J.

[0005] Further, the microstructure of the produced steel plate is composed of tempered martensite, tempered bainite and residual austenite, wherein the volume percentage of the residual austenite is 3%-10%.

[0006] Invention principle and main alloying element effect description: C: main hardenability element, increases strength and hardness through interstitial solid solution strengthening, excessive content will form a large number of twinned martensite to affect impact toughness, the content of C is controlled to be 0.2%-0.35% in the application.

[0007] Si: common deoxidizer, also has the effect of solid solution strengthening, when the Si content is high, the toughness and plasticity of the steel will be reduced, appropriate Si can inhibit the precipitation of carbide, the supersaturated carbon atoms diffuse and enrich in the untransformed austenite during bainite transformation, and appropriate residual austenite is retained after quenching, the content of Si is controlled to be 0.5%-1.5% in the application.

[0008] Mn: one of deoxidizers, main hardenability element, effectively improves strength and hardness through substitution solid solution strengthening, excessive Mn content will cause mold casting segregation and poor toughness, the content of Mn is controlled to be 0.5%-2.0% in the application.

[0009] Mo, Cr, Ni: increase hardenability, in addition to solid solution strengthening, Mo and Cr are mainly used to increase corrosion resistance and high temperature performance, and Ni is mainly used to improve low temperature performance.

[0010] B: gathers at the austenite grain boundary, effectively inhibits ferrite nucleation and delays ferrite pearlite transformation, thereby improving the hardenability of the steel, the content of B is controlled to be 0.001%-0.005% in the application.

[0011] P, S: are adverse elements in steel, seriously affect the strength, toughness and corrosion resistance of the steel, the content of P is controlled to be below 0.020% and the content of S is controlled to be below 0.005% in the application.

[0012] Compared with the prior art, the application has the beneficial effects that the H and N element contents are effectively reduced, the consumption of B by N is reduced, the effective B content is increased, and the hardenability of the steel plate is increased by long-time treatment at high vacuum degree by RH or VD furnace; the H content of the steel plate is further reduced by long-time stack cooling of the continuous casting billet, and the cracking tendency of the steel plate in cutting, processing and forming processes is reduced; the large reduction in the rough rolling process promotes dynamic recrystallization and refines the grains, which is beneficial to increase the toughness; the new alloy component design combined with the rolling and heat treatment processes can obtain a multi-phase composite structure of tempered martensite, tempered bainite and residual austenite, wherein the tempered martensite and bainite ensure that the matrix has high hardness, and the appropriate amount of residual austenite ensures that the steel plate provides high toughness and further hardening through the TRIP effect under the application working condition. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 Microstructure of the high-hardness and high-toughness wear-resistant steel produced in Example 1.

[0014] Figure 2 Residual austenite distribution diagram of the high-hardness and high-toughness wear-resistant steel produced in Example 1. DETAILED DESCRIPTION

[0015] The application will be further described below in combination with examples.

[0016] Example Group One: including Example 1, Example 2 and Example 3.

[0017] A production method of a high-hardness and high-toughness wear-resistant steel plate, the chemical components of the steel plate are as follows in terms of percentage by weight: C=0.28%, Mn=1.0%, Si=0.5%, Ni=0.8%, Cr=0.1%, Mo=0.2%, Cu=0.4, P=0.009%, S=0.002%, B=0.002, and the rest is Fe and inevitable impurity elements; the production process includes hot metal pretreatment, converter, LF and RH / VD refining, continuous casting, heating, rolling, finishing and quenching and tempering heat treatment. The smelting process is as follows: hot metal pretreatment, converter stirring and P removal, LF furnace refining for chemical component control, VD furnace vacuum treatment for 15 minutes, H content of 0.9 ppm, N content of 40 ppm, continuous casting billet thickness of 350 mm, and stack cooling time of 24 h.

[0018] The rolling process of Example 1, Example 2 and Example 3 is shown in Table 1, the heat treatment process is shown in Table 2, and the mechanical property test results and residual austenite content are shown in Table 3.

[0019] From the mechanical property test results, it can be known that the mechanical properties of the steel plate produced in the examples are as follows: yield strength ≥1150 MPa, tensile strength ≥1450 MPa, total elongation ≥10%, Brinell hardness ≥460 HBW, and impact energy at -20 ℃ ≥40 J.

[0020] Table 1 Rolling process parameters of examples .

[0021] Table 2 Heat treatment process parameters of examples .

[0022] Table 3 Mechanical properties and retained austenite content of steel sheets produced in examples .

[0023] Note: Sampling position is 1 / 4 thickness transverse direction.

Claims

1. A method for producing high-hardness, high-toughness, wear-resistant steel plates, the production process including hot metal pretreatment - converter - LF and RH / VD refining - continuous casting - heating - rolling - finishing - quenching and tempering heat treatment, characterized in that: The chemical composition of the steel, by weight percentage, is C=0.2~0.35%, Mn=0.5~2.0%, Si=0.5~1.5%, Ni≤1.0%, Cr≤2.0%, Mo=0.2~1.5%, Cu≤0.5%, P≤0.020%, S≤0.005%, B=0.001~0.005%, with the remainder being Fe and unavoidable impurity elements; Key process steps include: (1) RH / VD furnace: vacuum degree ≤80Pa, vacuum holding time ≥10 minutes and 12 minutes respectively, pure calcium wire ≥100m after vacuum treatment; (2) Continuous casting: The billet temperature at the bottom line is ≥400℃. It is cooled in a slow cooling pit or heat preservation cover for ≥48 hours. (3) Heating: The continuous casting billet needs to be preheated before entering the heating furnace. The preheating temperature is ≥200℃; (4) Rolling: Two-stage rolling is adopted. The roughing rolling temperature is ≥1050℃, the number of rolling passes with a single pass reduction rate of ≥10% is ≥2, the finishing rolling temperature is 850~950℃, and the finishing rolling temperature is 700~850℃. After rolling, the rolling is directly air-cooled without water. (5) Quenching and tempering heat treatment: Quenching + tempering process is adopted, with quenching temperature of 850~950℃ and tempering temperature of 170~300℃; the resulting steel plate has a yield strength ≥1150MPa, tensile strength ≥1450MPa, total elongation ≥10%, Brinell hardness ≥460HBW, and impact energy at -20℃ ≥40J.

2. The method for producing a high-hardness, high-toughness, wear-resistant steel plate as described in claim 1, characterized in that: The microstructure of the produced steel plate consists of tempered martensite, tempered bainite and retained austenite, with the retained austenite accounting for 3% to 10% of the volume.

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