A new quenching and tempering method for improving the strength and toughness of medium plate high-strength steel at low cost

Abstract

The application provides a new quenching and tempering method for improving the strength and toughness of a medium plate high-strength steel, and relates to the technical field of improving the strength and toughness of a medium plate high-strength steel. The method comprises the following steps: austenitizing heat treatment: heating a medium plate steel to be heat-treated to an austenitizing heat treatment temperature and keeping the temperature, so as to obtain a medium plate after austenitizing heat treatment; incomplete quenching and aging treatment: quenching the medium plate after austenitizing heat treatment to the vicinity of a martensite phase transition end point, and then performing incomplete quenching and aging treatment, and then cooling to room temperature, so as to obtain a medium plate high-strength steel with high strength and toughness. The medium plate steel to be heat-treated is subjected to austenitizing heat treatment and subsequent corresponding incomplete quenching and aging treatment, so that the toughness, especially the low-temperature toughness, of the medium plate high-strength steel is greatly improved without reducing the hardness. The method has the characteristics of low cost, high efficiency and green low carbon, and the internal stress of the steel plate is small after process modulation, so that the method is beneficial to industrial large-scale production and popularization and application.

Description

Technical Field

[0001] This invention relates to the technical field of improving the strength and toughness of medium and heavy plate high-strength steel, and in particular to a novel quenching and tempering treatment method for improving the strength and toughness of medium and heavy plate high-strength steel at low cost. Background Technology

[0002] Medium and heavy high-strength steel plates are widely used in engineering machinery, offshore platforms, large bridges, pressure vessels, and other fields. These materials withstand complex and harsh service conditions such as heavy loads, impacts, low temperatures, and wear, requiring them to possess both high strength and high toughness. Ordinary hot-rolled or normalized steel plates lack sufficient strength and toughness; quenching and tempering is the core path to achieving high strength and toughness in medium and heavy plate production, and it is widely used in the field of medium and heavy plate heat treatment. However, traditional quenching and tempering processes have drawbacks such as long processing time, high energy consumption, high production costs, low toughness, and high residual stress in the steel parts. How to improve the toughness, especially low-temperature toughness, of medium and heavy high-strength steel plates through low-cost, efficient, and low-energy heat treatment technologies is a key problem that urgently needs to be solved.

[0003] Chinese patent CN103225045A discloses a method for preparing high-ductility medium-thick plate steel with a yield strength of 690 MPa. The steel plate composition is: C 0.1%, Si 0.4-0.8%, Mn 2.0-2.5%, Al 0.4-0.8%, Nb 0.06-0.10%, Cu 1.0%, Ni 0.5-1.0%, Mo 0.1-0.3%, with the balance being Fe and unavoidable impurities. A multiphase microstructure including ferrite, bainite, secondary bainite, martensite, and retained austenite is obtained through heat treatment, resulting in a high elongation. However, this method suffers from drawbacks such as a complex heat treatment process and a tensile strength below 900 MPa.

[0004] Chinese patent CN121802128A discloses a medium-thick plate wear-resistant steel, based on a method for preparing ultrafine-grained wear-resistant steel controlled by austenite reverse phase transformation. The chemical element composition of the steel plate, by mass percentage, includes: C 0.15-0.30%, Si 0.20-0.80%, Mn 4.0-7.0%, P≤0.015%, S≤0.008%, Al 0.01-0.05%, Ti 0.01-0.05%, Nb 0.02-0.06%, V 0.05-0.15%, Mo 0.10-0.40%, Ni 0.5-1.5%, with the balance being Fe and unavoidable impurities. This method can obtain an ultrafine equiaxed austenitic structure, which is then quenched to obtain a fine-grained martensite matrix, and finally tempered at low temperature to obtain wear-resistant steel with high strength and toughness. However, this technology is complex, requires stringent heat treatment conditions, demands precise control of heating rates and annealing temperature ranges, and involves the addition of numerous alloying elements, resulting in high costs. Furthermore, the prepared materials exhibit low strength and minimal improvement in toughness, with an impact energy of only 30J at -20℃ and a Brinell hardness of less than 500HB.

[0005] Chinese patent CN105385835A discloses a heat treatment method for improving the strength and toughness of medium-thick plate high-strength steel components. The chemical element composition of the steel plate, by mass percentage, includes C 0.05-0.10%, Si 0.1-0.4%, Mn 1.20-1.80%, P≤0.01%, S≤0.01%, N≤0.004%, and Ti 0.025-0.049%. The method achieves an impact energy of >75J at -20℃ by controlling the rolling process within recrystallization, non-recrystallization, and the two-phase region. However, the multiple rolling processes across multiple temperature ranges are complex and difficult to manufacture industrially. Furthermore, the material has low strength, with a tensile strength of only 530-630MPa and a yield strength of 420-520MPa, which does not meet the requirements for high-strength medium-thick plate steel.

[0006] Therefore, there is an urgent need to develop a new quenching and tempering treatment method that is low-cost, low-carbon, and low-energy-consumption to improve the strength and toughness of medium and heavy plate high-strength steel, and to solve the technical problems of insufficient toughness and high energy consumption. Summary of the Invention

[0007] The main objective of this invention is to address the technical problems existing in the prior art for improving the strength and toughness of medium-thick plate high-strength steel, including the mismatch between low-temperature toughness and hardness. Therefore, a novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost is proposed, which can solve the aforementioned problems.

[0008] The technical solution is as follows: A novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost, comprising the following steps: S1. Austenitizing heat treatment: The medium-thick plate steel to be heat-treated is heated to the austenitizing heat treatment temperature and held at that temperature to obtain the medium-thick plate after austenitizing heat treatment. S2, Incomplete Quenching-Aging Treatment: The medium-thick plate after the austenitizing heat treatment of S1 is quenched and cooled to near the end point of martensitic phase transformation, and then subjected to incomplete quenching-aging treatment. After cooling to room temperature, high-strength and high-toughness medium-thick plate high-strength steel is finally obtained.

[0009] Optionally, the chemical composition of the medium-thick plate steel to be heat-treated in S1, by mass percentage, is: C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, other necessary alloying elements, with the balance being Fe and unavoidable impurity elements.

[0010] Optionally, the austenitizing heat treatment temperature in S1 needs to be determined based on the thickness of the steel plate, its specific composition, and the target austenite grain size.

[0011] Optionally, the thickness of the steel plate to be heat-treated in S1 is 3-10 mm, with a specific composition of C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, a target austenite grain size of 1-200 μm, and an austenitizing heat treatment temperature of A. c3 Above 5-100℃.

[0012] Optionally, the thickness of the steel plate to be heat-treated in S1 is 10-30mm, with the specific composition being C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, the target austenite grain size being 1-200μm, and the austenitizing heat treatment temperature being A. c3 Above 5-100℃.

[0013] Optionally, the thickness of the steel plate to be heat-treated in S1 is greater than 30 mm, with the specific composition being C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, the target austenite grain size being 1-200 μm, and the austenitizing heat treatment temperature being A. c3 Above 5-100℃.

[0014] Optionally, in S2, the incomplete quenching-aging treatment, wherein the incomplete quenching temperature is determined based on conditions including the steel thickness, chemical composition, and martensitic transformation end temperature, and the aging treatment includes any one of the following steps: Step a, isothermal aging: After incomplete quenching, perform heat preservation aging treatment at the target quenching temperature, and then cool to room temperature; Step b, heating and aging: After incomplete quenching, continue heating at a rate of 0.1-100℃ / min to 10-100℃ for aging treatment, and then cool to room temperature; Step c, Natural cooling aging: After incomplete quenching, no heat preservation is performed. The residual heat of the steel part is used for natural cooling aging treatment until it cools to room temperature. Step d, other aging methods: After incomplete quenching, staged or gradient cooling-aging treatment is performed.

[0015] Optionally, the thickness of the medium-thick plate steel heat-treated in S2 is 3-10mm, with the specific composition being C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, and the martensitic transformation end temperature Mf is much lower than A. c3 The incomplete quenching temperature is 100-400℃, and the aging treatment is selected from step a; the surface of high-strength steel in medium-thick plates has an impact absorption energy of 40-50J at -20℃ and a hardness of 470-530HB; its core has an impact absorption energy of 45-60J at -20℃ and a hardness of 470-530HB.

[0016] Optionally, the thickness of the medium-thick plate steel heat-treated in S2 is 10-30mm, with a specific composition of C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, and the martensitic transformation end temperature Mf is much lower than A. c3 The incomplete quenching temperature is 100-400℃, and the aging treatment is selected from step b; the surface of high-strength steel in medium-thick plates has an impact absorption energy of 40-50J at -20℃ and a hardness of 470-530HB; its core has an impact absorption energy of 45-60J at -20℃ and a hardness of 470-530HB.

[0017] Optionally, the thickness of the medium-thick plate steel heat-treated in S2 is greater than 30 mm, with the specific composition being C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, and the martensitic transformation end temperature Mf is much lower than A. c3 The incomplete quenching temperature is 100-400℃, and the aging treatment is selected from step c or step d; the surface of high-strength steel in medium-thick plates has an impact absorption energy of 40-55J and a hardness of 470-530HB at -20℃; its core has an impact absorption energy of 45-60J and a hardness of 470-530HB at -20℃.

[0018] The above technical solution has at least the following advantages compared with the existing technology: The present invention proposes a novel quenching and tempering treatment method for improving the strength and toughness of medium and heavy plate high-strength steel at low cost, which can solve the technical problems such as the mismatch between low-temperature toughness and hardness in the existing technology for improving the strength and toughness of medium and heavy plate high-strength steel.

[0019] The method of this invention significantly improves low-temperature toughness without reducing Brinell hardness, facilitates industrial production, does not significantly change the composition of existing industrial products, and is simple and significantly improved.

[0020] In summary, compared with traditional methods for preparing medium-thick plate high-strength steel, the method of this invention improves the low-temperature toughness of medium-thick plate high-strength steel without reducing its hardness by performing austenitic heat treatment on the medium-thick plate steel to be heat-treated and then performing corresponding incomplete quenching-aging treatment. This method is low-cost and highly efficient. The process is stable, easy to implement, environmentally friendly, and has a wide range of applications, which is conducive to large-scale industrial production and promotion. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used 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 those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a comparison chart of the impact absorption energy at -20℃ of medium-thick plate high-strength steel treated by the novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to the present invention, and that of medium-thick plate steel in the control example. Figure 2 This is a comparison diagram of the surface hardness and core hardness of medium-thick plate high-strength steel after a novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to Embodiment 1 of the present invention. Figure 3 This is a comparison of the -20℃ impact absorption energy of the surface and core of medium-thick plate high-strength steel after a novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to Embodiment 1 of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0024] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0025] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0026] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0027] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0028] A novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost, comprising the following steps: S1. Austenitizing heat treatment: The medium-thick plate steel to be heat-treated is heated to the austenitizing heat treatment temperature and held at that temperature to obtain the medium-thick plate after austenitizing heat treatment. S2. Incomplete Quenching-Aging Treatment: The medium-thick plate after the austenitizing heat treatment of S1 is quenched and cooled to near the end point of martensitic transformation, then subjected to incomplete quenching-aging treatment, and subsequently cooled to room temperature, finally obtaining high-strength and high-toughness medium-thick plate high-strength steel. Among them, the impact absorption energy at -20℃ of a portion of the high-strength and high-toughness medium-thick plate high-strength steel is compared with that of the control example medium-thick plate steel. Figure 1 As shown.

[0029] Specifically, the chemical composition of the medium-thick plate steel to be heat-treated in S1, by mass percentage, is: C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, other necessary alloying elements, with the balance being Fe and unavoidable impurity elements.

[0030] In particular, the austenitizing heat treatment temperature in S1 needs to be determined based on the thickness, specific composition, and target austenite grain size of the steel plate to be heat treated.

[0031] Specifically, the thickness of the steel plate to be heat-treated in S1 is 3-10 mm, with a specific composition of C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, a target austenite grain size of 1-200 μm, and an austenitizing heat treatment temperature of A. c3 Above 5-100 ℃.

[0032] Specifically, the thickness of the steel plate to be heat-treated in S1 is 10-30mm, with a specific composition of C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, a target austenite grain size of 1-200μm, and an austenitizing heat treatment temperature of A. c3 Above 5-100 ℃.

[0033] Specifically, the steel parts to be heat-treated in S1 are thicker than 30mm, with the following composition: C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, target austenite grain size of 1-200μm, and austenitizing heat treatment temperature of A. c3 Above 5-100 ℃.

[0034] Specifically, in S2, the incomplete quenching-aging treatment, wherein the incomplete quenching temperature is determined based on conditions including the steel thickness, chemical composition, and martensitic transformation end temperature, and the aging treatment includes any of the following steps: Step a, isothermal aging: After incomplete quenching, perform heat preservation aging treatment at the target quenching temperature, and then cool to room temperature; Step b, heating and aging: After incomplete quenching, continue heating at a rate of 0.1-100℃ / min to 10-100℃ for aging treatment, and then cool to room temperature; Step c, Natural cooling aging: After incomplete quenching, no heat preservation is performed. The residual heat of the steel part is used for natural cooling aging treatment until it cools to room temperature. Step d, other aging methods: After incomplete quenching, staged or gradient cooling-aging treatment is performed.

[0035] Specifically, the thickness of the medium-thick plate steel heat-treated in S2 is 3-10mm, with a specific composition of C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, and the martensitic transformation end temperature Mf is much lower than that of A. c3 The incomplete quenching temperature is 100-400℃, and the aging treatment is selected from step a; the surface of high-strength steel in medium-thick plates has an impact absorption energy of 40-50J at -20℃ and a hardness of 470-530HB; its core has an impact absorption energy of 45-60J at -20℃ and a hardness of 470-530HB.

[0036] Specifically, the thickness of the medium-thick plate steel heat-treated in S2 is 10-30mm, with a specific composition of C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, and the martensitic transformation end temperature Mf is much lower than that of A. c3 The incomplete quenching temperature is 100-400℃, and the aging treatment is selected from step b; the surface of high-strength steel in medium-thick plates has an impact absorption energy of 40-50J at -20℃ and a hardness of 470-530HB; its core has an impact absorption energy of 45-60J at -20℃ and a hardness of 470-530HB.

[0037] Specifically, the thickness of the medium-thick plate steel heat-treated in S2 is greater than 30 mm, with a specific composition of C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, and the martensitic transformation end temperature Mf is much lower than A. c3 The incomplete quenching temperature is 100-400℃, and the aging treatment is selected from step c or step d; the surface of high-strength steel in medium-thick plates has an impact absorption energy of 40-55J and a hardness of 470-530HB at -20℃; its core has an impact absorption energy of 45-60J and a hardness of 470-530HB at -20℃.

[0038] The impact testing equipment uses a microcomputer-controlled metal pendulum testing machine, and the impact test uses a Charpy V-notch.

[0039] The process of heat treatment for quenching and tempering of ordinary medium-thick plates is as follows: The steel plate sample was heated to the austenitic single-phase region and held at that temperature for a period of time to completely austenitize the initial microstructure. Then, it was rapidly cooled to room temperature to obtain a martensitic microstructure. The martensitic microstructure was then tempered and finally air-cooled to room temperature to obtain a tempered martensitic microstructure.

[0040] Comparative Example 1: The steel plate sample was austenitized by heating to 900℃ and holding for 15 min. It was then water-quenched to room temperature. The steel plate sample was then slowly heated to 300℃, held for 10 min for aging treatment, and then air-cooled to room temperature.

[0041] The high-strength and high-toughness medium-thick plate high-strength steel prepared in this comparative example has an impact absorption energy of 35J at -20℃, a hardness of 510HB, and an aging heat treatment time of 120min in the furnace; its core has an impact absorption energy of 25J at -20℃, a hardness of 510HB, and an aging heat treatment time of 120min in the furnace.

[0042] Example 1

[0043] This embodiment presents a novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost includes the following steps: S1. Austenitic heat treatment: The thickness of the medium-thick plate steel to be heat treated is 35mm. The chemical composition by mass percentage is: C 0.35%, Si 0.28%, Mn 1.35%, V+Nb total 0.020%, Cr+Mo total 0.78%, other necessary alloying elements, and the balance is Fe and unavoidable impurity elements. The medium-thick plate steel to be heat-treated is heated to the austenitizing heat treatment temperature and held at that temperature for 11 minutes to carry out austenitizing treatment. S2. Incomplete quenching-aging treatment: The medium-thick plate after the austenitizing heat treatment in S1 is quenched and cooled to near the end point of martensitic transformation, and then subjected to incomplete quenching-aging treatment; wherein, the end point temperature of martensitic transformation Mf is used for water quenching after being taken out of the furnace by spraying water, and the temperature of incomplete quenching is 300℃; the aging treatment is a natural cooling aging treatment, and no heat preservation is performed after incomplete quenching, and the residual heat of the steel part is used for natural cooling aging treatment until it is cooled to room temperature; The final product is a high-strength, high-toughness medium-thick plate high-strength steel.

[0044] The high-strength and high-toughness medium-thick plate high-strength steel prepared in this embodiment has an impact absorption energy of 50J at -20℃, a hardness of 502HB, and an aging heat treatment time of 0min in the furnace; its core has an impact absorption energy of 60J at -20℃, a hardness of 504HB, and an aging heat treatment time of 0min in the furnace. The hardness comparison between the surface and the core is as follows: Figure 2 As shown, the impact energy of the surface and the core is compared to, for example... Figure 3 As shown.

[0045] Example 2

[0046] This embodiment presents a novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost includes the following steps: S1. Austenitic heat treatment: The thickness of the medium-thick plate steel to be heat treated is 35mm. The chemical composition by mass percentage is: C 0.35%, Si 0.28%, Mn 1.35%, V+Nb total 0.020%, Cr+Mo total 0.78%, other necessary alloying elements, and the balance is Fe and unavoidable impurity elements. The medium-thick steel plate to be heat-treated is heated to the austenitizing heat treatment temperature and held at that temperature for 10 minutes to perform austenitizing treatment. S2. Incomplete quenching-aging treatment: The medium-thick plate after the austenitizing heat treatment in S1 is quenched and cooled to near the end point of martensitic transformation, and then subjected to incomplete quenching-aging treatment; wherein, the end point temperature of martensitic transformation is Mf, and after being taken out of the furnace, it is water-quenched by spraying water, and the incomplete quenching temperature is 300℃; the aging treatment is isothermal aging: after incomplete quenching, it is subjected to heat preservation aging treatment in a heating furnace at 300℃. After being removed, the material is air-cooled to room temperature, ultimately yielding high-strength, high-toughness medium-thick plate high-strength steel.

[0047] The high-strength and high-toughness medium-thick plate high-strength steel prepared in this embodiment has an impact absorption energy of 51J at -20℃, a hardness of 498HB, and an aging heat treatment time of 0min in the furnace; its core has an impact absorption energy of 47J at -20℃, a hardness of 502HB, and an aging heat treatment time of 30min in the furnace.

[0048] Example 3

[0049] This embodiment presents a novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost includes the following steps: S1. Austenitic heat treatment: The thickness of the steel plate to be heat treated is 20mm. The chemical composition by mass percentage is: C 0.35%, Si 0.28%, Mn 1.35%, V+Nb total 0.020%, Cr+Mo total 0.78%, other necessary alloying elements, and the balance is Fe and unavoidable impurity elements. The medium-thick plate steel to be heat-treated is heated to the austenitizing heat treatment temperature and held at that temperature for 10 minutes to carry out austenitizing treatment. S2, Incomplete Quenching-Aging Treatment: The medium-thick plate steel treated in S1 is quenched and cooled to near the end point of martensitic transformation, and then subjected to incomplete quenching-aging treatment; wherein, the end point temperature of martensitic transformation is Mf, and after exiting the furnace, it is water-quenched by spraying water, and the incomplete quenching temperature is 250℃; the aging treatment is isothermal aging: after incomplete quenching, it is heated in a furnace at 300℃ and held for aging treatment. After being removed, the material is air-cooled to room temperature, ultimately yielding high-strength, high-toughness medium-thick plate high-strength steel.

[0050] The high-strength and high-toughness medium-thick plate high-strength steel prepared in this embodiment has an impact absorption energy of 49J at -20℃ and a hardness of 503HB. The aging heat treatment time in the furnace is 30min. Its core has an impact absorption energy of 43J at -20℃ and a hardness of 506HB. The aging heat treatment time in the furnace is 30min.

[0051] Example 4

[0052] This embodiment presents a novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost includes the following steps: S1. Austenitic heat treatment: The thickness of the steel plate to be heat treated is 20mm. The chemical composition by mass percentage is: C 0.35%, Si 0.28%, Mn 1.35%, V+Nb total 0.020%, Cr+Mo total 0.78%, other necessary alloying elements, and the balance is Fe and unavoidable impurity elements. The medium-thick plate steel to be heat-treated is heated to the austenitizing heat treatment temperature and held at that temperature for 9 minutes to carry out austenitizing treatment. S2. Incomplete quenching-aging treatment: The medium-thick plate after the austenitizing heat treatment in S1 is quenched and cooled to near the end point of the martensitic transformation, and then subjected to incomplete quenching-aging treatment; wherein, the end point temperature of the martensitic transformation is Mf, and after being taken out of the furnace, it is water-quenched by spraying water, and the incomplete quenching temperature is 270℃; the aging treatment is isothermal aging: after incomplete quenching, it is heated in a furnace at 300℃ and held for aging treatment. After being removed, the material is air-cooled to room temperature, ultimately yielding high-strength, high-toughness medium-thick plate high-strength steel.

[0053] The high-strength and high-toughness medium-thick plate high-strength steel prepared in this embodiment has an impact absorption energy of 45J at -20℃ and a hardness of 509HB, and the aging heat treatment time in the furnace is 30min; its core has an impact absorption energy of 43J at -20℃ and a hardness of 507HB, and the aging heat treatment time in the furnace is 20min.

[0054] The present invention proposes a novel quenching and tempering treatment method for improving the strength and toughness of medium and heavy plate high-strength steel at low cost, which can solve the technical problems such as the mismatch between low-temperature toughness and hardness in the existing technology for improving the strength and toughness of medium and heavy plate high-strength steel.

[0055] The method of this invention significantly improves low-temperature toughness without reducing Brinell hardness, facilitates industrial production, does not significantly change the composition of existing industrial products, and is simple and significantly improved.

[0056] In summary, compared with traditional methods for preparing medium-thick plate high-strength steel, the method of this invention improves the low-temperature toughness of medium-thick plate high-strength steel without reducing its hardness by performing austenitic heat treatment on the medium-thick plate steel to be heat-treated and then performing corresponding incomplete quenching-aging treatment. This method is low-cost and highly efficient. The process is stable, easy to implement, environmentally friendly, and has a wide range of applications, which is conducive to large-scale industrial production and promotion.

[0057] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0058] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0059] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0060] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost, characterized in that, The novel quenching and tempering treatment method for improving the strength and toughness of medium and heavy plate high-strength steel at low cost includes the following steps: S1. Austenitizing heat treatment: The medium-thick plate steel to be heat-treated is heated to the austenitizing heat treatment temperature range and held at that temperature to obtain the medium-thick plate after austenitizing heat treatment. S2, Incomplete Quenching-Aging Treatment: The medium-thick plate after the austenitizing heat treatment of S1 is quenched and cooled to near the end point of martensitic phase transformation, and then subjected to incomplete quenching-aging treatment. After cooling to room temperature, high-strength and high-toughness medium-thick plate high-strength steel is finally obtained.

2. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to claim 1, characterized in that, The chemical composition of the medium-thick plate steel to be heat-treated in S1, by mass percentage, is: C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, other necessary alloying elements, with the balance being Fe and unavoidable impurity elements.

3. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to claim 1, characterized in that, The austenitizing heat treatment temperature in S1 needs to be determined based on the thickness of the steel plate, its specific composition, and the target austenite grain size.

4. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to claim 3, characterized in that, The thickness of the medium-thick steel plate to be heat-treated in S1 is 3-10mm, with the following specific composition: C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, target austenite grain size of 1-200μm, and austenitizing heat treatment temperature equal to the austenite phase transformation completion temperature A. c3 Above 5~100℃.

5. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to claim 1, characterized in that, The thickness of the medium-thick steel plate to be heat-treated in S1 is 10-30mm, with the following specific composition: C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, target austenite grain size of 1-200μm, and austenitizing heat treatment temperature of A. c3 Above 5~100℃.

6. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to claim 1, characterized in that, The steel plate to be heat-treated in S1 has a thickness greater than 30 mm. Its specific composition is: C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, with a target austenite grain size of 1-200 μm, and an austenitizing heat treatment temperature of A. c3 Above 5 ~ 100 ℃.

7. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to claim 1, characterized in that, In S2, the incomplete quenching-aging treatment, wherein the incomplete quenching temperature is determined based on conditions including the steel thickness, chemical composition, and martensitic transformation end temperature, and the aging treatment includes any one of the following steps: Step a, isothermal aging: After incomplete quenching, perform heat preservation aging treatment at the target quenching temperature, and then cool to room temperature; Step b, heating and aging: After incomplete quenching, continue to heat at a rate of 0.1-100℃ / min for aging treatment by 10-100℃, and then cool to room temperature; Step c, Natural cooling aging: After incomplete quenching, no heat preservation is performed. The residual heat of the steel part is used for natural cooling aging treatment until it cools to room temperature. Step d, other aging methods: After incomplete quenching, staged or gradient cooling-aging treatment is performed.

8. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to claim 7, characterized in that, The thickness of medium-thick plate steel treated in S2 is 3-10mm, with the specific composition as follows: C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, and the martensitic transformation end temperature M. f Much lower than A c3 The temperature range for incomplete quenching is 100-400℃, and step a is selected for aging treatment; the surface of high-strength steel in medium-thick plates has an impact energy absorption of 40-50J and a hardness of 470-530HB at -20℃; its core has an impact energy absorption of 45-60J and a hardness of 470-530HB at -20℃.

9. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to claim 7, characterized in that, The thickness of medium-thick plate steel treated in S2 is 10-30mm, with the specific composition as follows: C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, and the martensitic transformation end temperature Mf is much lower than that of A. c3 The incomplete quenching temperature is 100-400℃, and the aging treatment is selected from step b; the surface of high-strength steel in medium-thick plates has an impact absorption energy of 40-50J at -20℃ and a hardness of 470-530HB; its core has an impact absorption energy of 45-60J at -20℃ and a hardness of 470-530HB.

10. The novel quenching and tempering treatment method for improving the strength and toughness of medium-thick plate high-strength steel at low cost according to claim 7, characterized in that, The thickness of medium-thick plate steel treated in S2 is greater than 30mm. The specific composition is: C 0.10-0.8%, Si 0.01-2.5%, Mn 0.01-3.0%, V+Nb+Ti total 0.0-0.2%, Ni+Cr+Mo total 0.0-3.0%, and the martensitic transformation end temperature Mf is much lower than A. c3 The incomplete quenching temperature is 100-400℃, and the aging treatment is selected from step c or step d; the surface of high-strength steel in medium-thick plates has an impact absorption energy of 40-55J and a hardness of 470-530HB at -20℃; its core has an impact absorption energy of 45-60J and a hardness of 470-530HB at -20℃.

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