Production and manufacturing method of low-cost high-elongation 600MPa-grade steel plate

Abstract

The invention relates to the technical field of ferrous metallurgy, in particular to a production and manufacturing method of a low-cost high-elongation 600MPa-grade steel plate, which is characterized in that raw materials comprise the following chemical components in percentage by weight: 0.111 to 0.173 percent of C, 0.13 to 0.43 percent of Si, 1.325 to 1.565 percent of Mn, less than or equal to 0.018 percent of P, less than or equal to 0.008 percent of S, 0.020 to 0.060 percent of Alt, 0.0225 to 0.0435 percent of Nb, less than or equal to 0.0070 percent of N and the balance of Fe; the manufacturing method comprises the following steps of top-bottom combined blown converter, LF refining, VD vacuum refining, slab continuous casting, two-stage controlled rolling and subsection cooling.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a method for producing a low-cost, high-elongation 600MPa grade steel plate. Background Art

[0002] Limited by the mechanical properties of traditional 600MPa steel plates, heavy machinery and large steel structure industries mostly use cutting, blanking and welding to process and manufacture traditional 600MPa steel. This processing method has high work intensity, low production efficiency and poor working environment. In recent years, with the improvement of production efficiency and carbon emission standards, traditional 600MPa steel plates can no longer meet processing requirements. Therefore, there is an urgent need for a 600MPa steel plate with low cost, high elongation and excellent bending performance, which can be processed by cold forming to replace traditional 600MPa steel plates, solve the problems encountered in the processing process, improve its production efficiency and reduce its carbon emissions. Summary of the invention

[0003] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a method for producing a low-cost and high-elongation 600MPa grade steel plate. The technical solution to the problem is that the present invention provides a low-cost, high-elongation, 600MPa grade steel plate composition design, and only a small amount of Si, Mn, Al, and Nb alloys are added to the raw materials, and no other precious alloys are needed. Clean steel smelting technology, two-stage controlled rolling and segmented cooling are used to obtain a low-cost and high-elongation 600MPa grade steel plate.

[0004] The steel plate produced by this manufacturing method has a yield strength of ≥480MPa, a tensile strength of ≥600MPa, an elongation after fracture A≥22%, a longitudinal impact energy at -20°C ≥100J, and is qualified in a 180° cold bending test D=1a.

[0005] To achieve the above object, the composition scheme adopted by the present invention is: A low-cost, high-elongation 600MPa grade steel plate, comprising the following chemical components in weight percentage: C: 0.111-0.173%, Si: 0.13-0.43%, Mn: 1.32-1.56%, P≤0.018%, S≤0.008%, Alt: 0.020%-0.060%, Nb: 0.022%-0.043%, N≤0.0070%, and the balance is Fe and unavoidable impurities; To achieve the above purpose, the production scheme adopted by the present invention is: A method for manufacturing a low-cost, high-elongation 600MPa grade steel plate, comprising a top and bottom combined blowing converter, LF refining, VD vacuum refining, slab continuous casting, two-stage controlled rolling and segmented cooling; wherein: The oxygen blowing time of the top and bottom combined blowing converter is 14-16 minutes, and the steel tapping ensures that the molten steel P≤0.014%, S≤0.022%, O≤0.060%; During the LF refining process, aluminum is controlled throughout the process, and at the same time, argon weak stirring time is not less than 5 minutes in the later stage of the LF furnace to reduce large and medium-sized inclusions in the steel while ensuring uniform temperature of the molten steel on the VD furnace; The vacuum degree in the VD degassing process is ≤0.67mbar, and the maximum vacuum degree smelting holding time is not less than 12min; The LF refining and VD vacuum refining treatments ensure that the temperature and composition of the molten steel meet the requirements for continuous casting, wherein the gas: N≤0.0060%, O≤0.0030%, H≤0.0002%; The wide slab continuous casting adopts full-process protection casting, the casting speed fluctuation is ±0.06m / min, the crystallizer liquid level fluctuation is ±2.5mm, and the molten steel superheat is controlled at 9-23℃; The two-stage controlled rolling plus segmented cooling: segmented cooling is performed in the cooling stage after rolling, the first stage adopts air cooling, the starting temperature is 780-820°C, and the ending temperature is 760-820°C; the second stage adopts laminar cooling, the starting temperature is 760-820°C, and the ending temperature is 500-650°C.

[0006] Compared with the prior art, the present invention has the following beneficial effects: 1. The 600MPa grade steel plate produced by the manufacturing method of the present invention has a yield strength of ≥480MPa, a tensile strength of ≥600MPa, an elongation after fracture A ≥22%, a longitudinal impact energy at -20°C ≥100J, and a 180° cold bending test D=1a that is qualified.

[0007] 2. The amount of alloy added in its production process is small, the production cost is low, the elongation is high, and the bending performance is good.

[0008] 3. Cold forming can be used for processing to reduce the welding workload of downstream users. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 These are the performance indicators of the steel plate manufactured in Example 1 of the present invention.

[0010] Figure 2 These are the performance indicators of the steel plate manufactured in Example 2 of the present invention. DETAILED DESCRIPTION

[0011] The technical solutions and effects of the present invention are further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0012] Example 1 The present invention is further described below by taking the company's 3500mm Steckel mill production line, which rolls a 20mm thick, low-cost, high-elongation 600MPa grade steel plate as an example.

[0013] In this embodiment, the smelting components are matched by weight percentage, including the following components: C: 0.132%, Si: 0.211%, Mn: 1.534%, P: 0.011%, S: 0.004%, Alt: 0.025%, Nb: 0.028%, N: 0.0053%, and the balance is Fe and unavoidable impurities.

[0014] The production process of this embodiment includes top and bottom combined blowing converter, LF refining, VD degassing refining, wide slab continuous casting, furnace coil mill controlled rolling, and three-stage controlled cooling. Among them, the oxygen blowing time of the top and bottom combined blowing converter is 14~16min, and the steel tapping ensures that the molten steel P≤0.014%, S≤0.022%, O≤0.060%; during the LF refining process, aluminum is controlled throughout the process, and at the same time, the argon weak stirring time in the late stage of the LF furnace is not less than 5min, which reduces large and medium-sized inclusions in the steel while ensuring uniform temperature of the molten steel on the VD furnace; the vacuum degree in the VD degassing process is ≤0.67mbar, and the highest vacuum degree smelting time is not less than 12min. After LF refining and VD vacuum refining treatment, the temperature and composition of the molten steel meet the requirements of continuous casting, among which the gas: N≤0.0060%, O≤0.0030%, H≤0.0002%; the slab continuous casting adopts full-process protective pouring, the pulling speed fluctuates within ±0.06m / min, the crystallizer liquid level fluctuates within ±2.5mm, and the molten steel superheat is controlled at 9~23℃.

[0015] The cooling stage after rolling is carried out in stages. The first stage uses air cooling, with a starting temperature of 780~793℃ and an ending temperature of 765~785℃; the second stage uses laminar cooling, with a starting temperature of 765~785℃ and an ending temperature of 590~620℃.

[0016] The performance index of the steel plate produced according to the steps of this embodiment is shown in Figure 1 .

[0017] Depend on Figure 1 It can be seen that the 600MPa steel plate produced in this embodiment can meet the product performance requirements by adopting clean steel smelting technology, two-stage controlled rolling and segmented cooling.

[0018] Among them, C: 0.132%, Mn: 1.534%, Nb: 0.028%. Clean steel smelting technology, two-stage controlled rolling + segmented cooling are adopted to obtain good plasticity while ensuring strength. The steel plate has an elongation after fracture A≥22%, a longitudinal impact energy at -20℃≥100J, and a 180° cold bending test D=1a that is qualified. This is one of the core technologies of the present invention.

[0019] Example 2 The present invention is further described below by taking the company's 3500mm Steckel mill production line, which rolls a 16mm thick, low-cost, high-elongation 600MPa grade steel plate as an example.

[0020] In this embodiment, the smelting components are matched by weight percentage, including the following components: C: 0.127%, Si: 0.251%, Mn: 1.516%, P: 0.012%, S: 0.003%, Alt: 0.028%, Nb: 0.031%, N: 0.0047%, and the balance is Fe and unavoidable impurities.

[0021] The production process of this embodiment includes top and bottom combined blowing converter, LF refining, VD degassing refining, wide slab continuous casting, furnace coil mill controlled rolling, and three-stage controlled cooling. Among them, the oxygen blowing time of the top and bottom combined blowing converter is 14~16min, and the steel tapping ensures that the molten steel P≤0.014%, S≤0.022%, O≤0.060%; during the LF refining process, aluminum is controlled throughout the process, and at the same time, the argon weak stirring time in the late stage of the LF furnace is not less than 5min, which reduces large and medium-sized inclusions in the steel while ensuring uniform temperature of the molten steel on the VD furnace; the vacuum degree in the VD degassing process is ≤0.67mbar, and the highest vacuum degree smelting time is not less than 12min. After LF refining and VD vacuum refining treatment, the temperature and composition of the molten steel meet the requirements of continuous casting, among which the gas: N≤0.0060%, O≤0.0030%, H≤0.0002%; the slab continuous casting adopts full-process protective pouring, the pulling speed fluctuates within ±0.06m / min, the crystallizer liquid level fluctuates within ±2.5mm, and the molten steel superheat is controlled at 9~23℃.

[0022] The cooling stage after rolling is carried out in stages. The first stage uses air cooling, with a starting temperature of 780~793℃ and an ending temperature of 765~785℃; the second stage uses laminar cooling, with a starting temperature of 765~785℃ and an ending temperature of 590~620℃.

[0023] The performance index of the steel plate produced according to the steps of this embodiment is shown in Figure 2 .

[0024] Depend on Figure 2 It can be seen that the 600MPa steel plate produced in this embodiment can meet the product performance requirements by adopting clean steel smelting technology, two-stage controlled rolling + segmented cooling.

[0025] Among them, C: 0.127%, Mn: 1.516%, Nb: 0.031%. Clean steel smelting technology, two-stage controlled rolling + segmented cooling are adopted to obtain good plasticity while ensuring strength. The steel plate has an elongation after fracture A≥22%, the longitudinal impact energy at -20℃≥100J, and the 180° cold bending test D=a is qualified. This is one of the core technologies of the present invention.

[0026] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing a low-cost, high-elongation 600MPa grade steel plate, characterized in that: The raw material includes the following chemical components in weight percentage: C: 0.111-0.173%, Si: 0.13-0.43%, Mn: 1.325-1.565%, P≤0.018%, S≤0.008%, Alt: 0.020%-0.060%, Nb: 0.0225%-0.0435%, N≤0.0070%, and the balance is Fe; The manufacturing method comprises the following steps: top and bottom combined blowing converter, LF refining, VD vacuum refining, slab continuous casting, two-stage controlled rolling and segmented cooling; Step 1: Blowing the raw materials in a top-bottom combined blowing converter, wherein the oxygen blowing time of the top-bottom combined blowing converter is 14-16 minutes, and the steelmaking process ensures that the molten steel P≤0.014%, S≤0.022%, and O≤0.060%; Step 2: LF refining is performed on the molten steel. During the LF refining process, aluminum is controlled throughout the process. At the same time, argon weak stirring time is not less than 5 minutes in the later stage of the LF furnace to reduce large and medium-sized inclusions in the steel while ensuring uniform temperature of the molten steel in the VD furnace; Step 3, further VD vacuum refining is performed on the molten steel, wherein the vacuum degree in the VD degassing process is ≤0.67mbar, and the maximum vacuum degree smelting holding time is not less than 12min; Step 4: slab continuous casting is performed on the molten steel after VD vacuum refining. The wide slab continuous casting adopts full-process protection casting, the casting speed fluctuates within ±0.06m / min, the crystallizer liquid level fluctuates within ±2.5mm, and the superheat of the molten steel is controlled within 9-23°C; Step 5: The slab is subjected to two-stage controlled rolling and segmented cooling: segmented cooling is performed in the cooling stage after rolling, the first stage adopts air cooling, the starting temperature is 780-820°C, and the ending temperature is 760-820°C; the second stage adopts laminar cooling, the starting temperature is 760-820°C, and the ending temperature is 500-650°C.

2. The method for producing a low-cost, high-elongation 600MPa grade steel plate according to claim 1, characterized in that: In the LF refining and VD vacuum refining treatment, the temperature and composition of the molten steel must meet the continuous casting requirements, wherein the gas: N≤0.0060%, O≤0.0030%, H≤0.0002%.

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