High-efficiency tempering method for improving and modulating aging impact of high-strength steel

Abstract

The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a high-efficiency tempering method for improving aging impact of modulated high-strength steel, which comprises the following steps: 1, heating a quenched and tempered high-strength steel plate in a quenching furnace, controlling the quenching temperature at 885-905 DEG C, and calculating the heat preservation time according to the thickness; 2, after the quenching temperature and time meet the requirements, quenching the steel plate to be lower than or equal to 50 DEG C by adopting a quenching machine, and ensuring thorough quenching; thirdly, the quenched steel plate is tempered, the tempering temperature ranges from 680 DEG C to 720 DEG C, and the tempering time is calculated according to the thickness; and fourthly, the surface temperature of the steel plate can reach 700 + / -20 DEG C after the steel plate is discharged from the furnace, and the temperature of the thickness center is controlled not to exceed 660 DEG C. By implementing high-temperature short-time tempering, the surface aging impact of the quenched and tempered high-strength steel is effectively improved, and the aging impact value can be stabilized to be 200 J or above.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, and in particular, it is an improved method for high-efficiency tempering of high-strength steel under aging impact. Background Technology

[0002] For steel plates with a yield strength exceeding 600MPa, failure to pass the aging impact test is a significant factor affecting the pass rate of such high-strength steel plates. Due to factors such as equipment, process, and water volume, the surface of quenched and tempered high-strength steel plates is prone to problems such as overcooling and overquenching, which in turn affects the surface aging impact test of the quenched and tempered steel plates. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies, such as unstable surface aging impact of tempered high-strength steel (i.e., the tendency for single surface aging impact values ​​to be too low), and to propose an improved high-efficiency tempering method for modulating the aging impact of high-strength steel.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] An improved high-efficiency tempering method for modulating the aging impact of high-strength steel includes the following steps:

[0006] Step 1: Heat the quenched and tempered high-strength steel plate with a strength of 600MPa or above in a quenching furnace. The quenching temperature is controlled at 885-905℃, and the holding time is calculated according to the thickness.

[0007] Step 2: After the quenching temperature and time meet the heating requirements, use a quenching machine to cool the steel plate to below or equal to 50°C to ensure thorough quenching.

[0008] Step 3: Temper the quenched steel plate. The tempering furnace is a radiation tube heated non-oxidizing roller hearth furnace. Nitrogen gas is used for protection throughout the tempering process to prevent oxidation of the steel plate surface. The tempering temperature is 680-720℃, and the tempering time is calculated according to the thickness.

[0009] Step 4: After the steel plate comes out of the furnace, the surface temperature can reach 700±20℃, and the temperature at the center of the thickness should not exceed 660℃ according to the black box test of the tempering furnace.

[0010] As a further preferred option, in step one, the quenching temperature is controlled at 895℃.

[0011] As a further preferred option, in step one, the holding time after quenching is controlled to be 1.6 ± 0.2 minutes / mm.

[0012] As a further preferred option, in step three, the tempering temperature is 700°C.

[0013] As a further preferred option, in step three, the tempering time is controlled to be less than or equal to 2 minutes / mm.

[0014] Beneficial effects: The technical solution of the present invention can ensure that the impact energy of the surface aging impact of high-strength steel such as hydroelectric steel of 800MPa grade is stably controlled above 200J, which effectively improves the pass rate of aging impact performance of this type of steel. Attached Figure Description

[0015] Figure 1 This is a surface view of the metallographic structure of Example 4;

[0016] Figure 2 This is a cross-sectional view of the metallographic structure at 1 / 4 thickness in Example 4;

[0017] Figure 3 This is a cross-sectional view of the metallographic structure at 1 / 2 thickness in Example 4;

[0018] Figure 4 This is a metallographic surface view of Example 5;

[0019] Figure 5 This is a cross-sectional view of the metallographic structure at 1 / 4 thickness in Example 5;

[0020] Figure 6 This is a cross-sectional view of the metallographic structure at 1 / 2 thickness in Example 5. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] This invention discloses an improved tempering heat treatment process for quenched and tempered high-strength steel plates with a strength of 600 MPa or higher. This process effectively increases the aging impact pass rate and tempering efficiency of such high-strength steel plates. The main technical solutions are as follows:

[0023] Step 1: Heat the quenched and tempered high-strength steel plate with a strength of 600MPa or above in a quenching furnace. The quenching temperature is controlled at 895±10℃, and the holding time is calculated according to the thickness and controlled at 1.6±0.2 minutes / mm.

[0024] Step 2: After the quenching temperature and time meet the heating requirements, use a quenching machine to cool the steel plate to below or equal to 50°C to ensure thorough quenching.

[0025] Step 3: Temper the quenched steel plate. The tempering furnace is a radiation tube heated non-oxidizing roller hearth furnace. Nitrogen gas is used for protection throughout the tempering process to prevent oxidation of the steel plate surface. The tempering temperature is 700±20℃ and the tempering time coefficient is controlled not to exceed 2.0 minutes / mm.

[0026] Step 4: After the steel plate comes out of the furnace, the surface temperature can reach 700±20℃, and the temperature at the center of the thickness does not exceed 660℃ according to the black box test of the tempering furnace.

[0027] Examples 1-3

[0028] The embodiments of this technical solution use hydroelectric steel as the main steel grade. The steelmaking and rolling processes of this steel grade are conventional processes. The quenching and tempering processes are carried out in accordance with the technical solution of this invention patent. The heat treatment embodiments of tempering are shown in Table 1, and the aging impact of the embodiments are shown in Table 2.

[0029] Table 1: Results of tempering heat treatment

[0030]

[0031] Table 2: Surface aging impact results

[0032]

[0033] Example 4

[0034] Metallographic microstructure of 120mm thick 780CF hydroelectric steel produced using this technical solution (full cross-sectional thickness). Figure 1 For surface view, Figure 2 This is a cross-sectional view at 1 / 4 thickness. Figure 3 This is a cross-sectional view with a thickness of 1 / 2.

[0035] Example 5

[0036] Metallographic microstructure of 60mm thick 780CF hydroelectric steel produced using this technical solution (full cross-sectional thickness). Figure 4 For surface view, Figure 5 This is a cross-sectional view at 1 / 4 thickness. Figure 6 This is a cross-sectional view with a thickness of 1 / 2.

[0037] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An improved high-efficiency tempering method for modulating the aging impact of high-strength steel, characterized in that: Includes the following steps: Step 1: Heat the quenched and tempered high-strength steel plate with a strength of 600MPa or above in a quenching furnace. The quenching temperature is controlled at 885-905℃, and the holding time is calculated according to the thickness. Step 2: After the quenching temperature and time meet the heating requirements, use a quenching machine to cool the steel plate to below or equal to 50°C to ensure thorough quenching. Step 3: Temper the quenched steel plate. The tempering furnace is a radiation tube heated non-oxidizing roller hearth furnace. Nitrogen gas is used for protection throughout the tempering process to prevent oxidation of the steel plate surface. The tempering temperature is 680-720℃, and the tempering time is calculated according to the thickness. Step 4: After the steel plate comes out of the furnace, the surface temperature can reach 700±20℃, and the temperature at the center of the thickness is less than or equal to 660℃ according to the black box test of the tempering furnace.

2. The improved high-efficiency tempering method for modulating the aging impact of high-strength steel according to claim 1, characterized in that: In step one, the quenching temperature is controlled at 895℃.

3. The improved high-efficiency tempering method for modulated aging impact of high-strength steel according to claim 1, characterized in that: In step one, the holding time after quenching is controlled to be 1.6 ± 0.2 minutes / mm.

4. The improved high-efficiency tempering method for modulating the aging impact of high-strength steel according to claim 1, characterized in that: In step three, the tempering temperature is 700°C.

5. The improved high-efficiency tempering method for modulated aging impact of high-strength steel according to claim 1, characterized in that: In step three, the tempering time is controlled to be less than or equal to 2 minutes / mm.

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