345MPa-grade atmospheric corrosion-resistant steel plate with extremely low yield ratio and production method of 345MPa-grade atmospheric corrosion-resistant steel plate

Abstract

The invention relates to the technical field of high-strength steel plates, in particular to a 345MPa-grade atmospheric corrosion resistant steel plate with an extremely low yield ratio and a production method thereof, and the steel plate comprises the following chemical components in percentage by mass: 0.06 to 0.12 percent of C, 0.15 to 0.40 percent of Si, 0.30 to 0.60 percent of Mn, 0.060 to 0.120 percent of P, less than or equal to 0.010 percent of S, 0.30 to 0.50 percent of Cr, 0.15 to 0.35 percent of Ni, 0.25 to 0.50 percent of Cu, 0.010 to 0.035 percent of Nb, 0.005 to 0.030 percent of Ti, 0.020 to 0.045 percent of Alt and the balance of Fe and impurities. The manufacturing method provided by the invention is simple in process and relatively low in cost, and the 345MPa-grade atmospheric corrosion-resistant steel plate with an extremely low yield ratio is produced through a controlled rolling and controlled cooling process.

Description

Technical Field

[0001] The present invention relates to the technical field of high-strength steel plates, and in particular to a 345MPa-grade atmospheric corrosion-resistant steel plate with an extremely low yield ratio and a production method thereof. Background Art

[0002] Atmospheric corrosion-resistant steel is a high-phosphorus steel with appropriate amounts of chromium, nickel, copper, and other atmospheric corrosion-resistant elements. Its weathering resistance is several times that of ordinary carbon steel, and its paintability is 1.5 to 10 times that of ordinary carbon steel. It also offers advantages such as rust resistance, extended service life, reduced thickness, reduced consumption, and labor and energy savings, and has broad application prospects.

[0003] How to provide a 345MPa grade atmospheric corrosion resistant steel plate with an extremely low yield ratio and a production method thereof, which is beneficial to maintaining a low yield ratio and obtaining good plasticity, is a problem that needs to be solved at present. Summary of the Invention

[0004] The present invention aims to solve the above-mentioned technical problems and overcome the shortcomings of the prior art, and provides a 345MPa-grade atmospheric corrosion-resistant steel plate with an extremely low yield ratio and a production method thereof. The 345MPa-grade atmospheric corrosion-resistant steel plate with an extremely low yield ratio is produced through a controlled rolling and controlled cooling process, with a yield strength between 350 and 400MPa, an elongation A ≥ 25%, a yield ratio between 0.72 and 0.79, and an impact energy ≥ 80J at -40°C.

[0005] In a first aspect, the present invention provides a 345 MPa-grade atmospheric corrosion-resistant steel plate with an extremely low yield ratio, the chemical composition and percentage by mass of which are as follows: C: 0.06-0.12%, Si: 0.15-0.40%, Mn: 0.30-0.60%, P: 0.060-0.120%, S: ≤0.010%, Cr: 0.30-0.50%, Ni: 0.15-0.35%, Cu: 0.25-0.50%, Nb: 0.010-0.035%, Ti: 0.005-0.030%, Alt: 0.020-0.045%, with the balance being Fe and impurities. A low manganese content helps reduce yield strength, thereby lowering the yield ratio.

[0006] Furthermore, the thickness of the steel plate is 8-20 mm.

[0007] Furthermore, the yield strength of the steel plate is between 350 and 400 MPa, the elongation A is ≥25%, the yield strength ratio is between 0.72 and 0.79, and the impact energy at -40°C is ≥80J.

[0008] In the second aspect, the present invention also provides a method for producing a 345MPa grade atmospheric corrosion resistant steel plate with an extremely low yield ratio, which is suitable for the 345MPa grade atmospheric corrosion resistant steel plate described in the first aspect. The specific steps include smelting, continuous casting and rolling. In the rolling step, two-stage rolling is adopted, and the rough rolling temperature is 900-1150°C; the starting rolling temperature of the finishing rolling is 850-950°C, and the final rolling temperature of the finishing rolling is 800-850°C.

[0009] Furthermore, laminar cooling is performed after finish rolling, with a return temperature of 450 to 600° C. and a cooling rate of 1 to 20° C. / s.

[0010] Furthermore, the smelting specifically includes: pre-desulfurization through molten iron pretreatment, converter blowing, and then LF refining to adjust the alloy composition, RH vacuum treatment to improve the purity of the molten steel, and calcium treatment after soft stirring to ensure that the molten steel with high purity and qualified composition is obtained.

[0011] The present invention ensures the alloy composition and impurity element content through smelting, and uses a calcium treatment smelting process combined with a dynamic soft reduction process to improve the internal quality of the ingot; and adopts precise rolling and precise controlled cooling processes in the controlled rolling and controlled cooling stage.

[0012] The beneficial effects of the present invention are:

[0013] (1) The present invention adopts a smelting process that ensures the alloy composition and impurity element content while also performing calcium treatment. The continuous casting production is combined with a dynamic soft pressure casting process to improve the internal quality of the ingot and ensure the plasticity and toughness of the steel plate.

[0014] (2) The manufacturing method of the present invention has a simple process and low cost, and produces a 345MPa grade atmospheric corrosion resistant steel plate with an extremely low yield ratio through a controlled rolling and controlled cooling process;

[0015] (3) The steel plate obtained by the manufacturing method of the present invention has stable performance: yield strength is between 350 and 400 MPa, elongation A ≥ 25%, yield strength ratio is between 0.72 and 0.79, and impact energy at -40°C is ≥ 80 J. DETAILED DESCRIPTION

[0016] The present invention provides a 345 MPa grade atmospheric corrosion resistant steel plate with an extremely low yield ratio and a production method thereof, wherein the components of each embodiment of the 345 MPa grade atmospheric corrosion resistant steel plate are shown in Table 1 in terms of weight percentage.

[0017] The specific requirements for the production method of the above-mentioned 345MPa grade atmospheric corrosion resistant steel plate with extremely low yield ratio are as follows:

[0018] Controlled Rolling and Controlled Cooling Process: A two-stage controlled rolling and cooling process (TMCP) is used; the rough rolling temperature is 900-1150°C; the start rolling temperature of the finishing rolling is 850-950°C, and the final rolling temperature of the finishing rolling is 800-850°C. Laminar cooling is then performed with a return to red temperature of 450-600°C and a cooling rate of 1-20°C / s. The finished steel plate has a thickness of 8-20mm.

[0019] It can be understood that the production method of the present invention not only ensures the alloy composition and impurity element content during smelting, but also adopts smelting processes such as calcium treatment and RH vacuum treatment to ensure the control of inclusions in the steel plate; secondly, the continuous casting production is combined with the dynamic light reduction process to improve the internal quality of the ingot and reduce the level of macro and micro segregation in the center of the ingot; the precise controlled rolling process adopts weak cooling to control the cooling rate to a smaller level in the controlled cooling stage to obtain a tough structure; the toughness of the steel plate is improved through the control of inclusions and the control of the structure.

[0020] The present invention develops a 345MPa-grade atmospheric corrosion-resistant steel plate with an extremely low yield ratio, forming a complete set of smelting and rolling production technologies. The production process is simple, easy to operate, and the product has stable performance. The production method uses flat rolling rather than hot continuous rolling to achieve a yield ratio below 0.8. The resulting 345MPa-grade atmospheric corrosion-resistant steel plate has a low yield ratio and good plasticity, and has broad application prospects. The properties of the finished steel plate are shown in Table 2-3 below, where the balance is iron and I is the atmospheric corrosion resistance index.

[0021] Table 1 Chemical composition of the present invention (wt%)

[0022] Example C Si Mn P S Alt Cr Ni Cu Nb Ti I Example 1 0.08 0.35 0.55 0.102 0.005 0.032 0.36 0.16 0.31 0.017 0.013 7.63 Example 2 0.09 0.35 0.55 0.090 0.005 0.031 0.35 0.15 0.29 0.015 0.014 7.30 Example 3 0.10 0.38 0.47 0.090 0.004 0.030 0.35 0.17 0.30 0.015 0.014 7.44 Example 4 0.09 0.35 0.55 0.09 0.005 0.032 0.35 0.15 0.29 0.015 0.014 7.33 Example 5 0.10 0.38 0.48 0.09 0.004 0.033 0.35 0.17 0.3 0.016 0.010 7.44

[0023] Table 2 Tensile properties

[0024]

[0025] Table 3 Series Temperature Shock Performance

[0026]

[0027] It can be seen that the mechanical properties of Examples 1, 2, and 3 all meet the requirements of 345 MPa-grade atmospheric corrosion-resistant steel plates; specifically, the properties of the steel plates reach the following levels: yield strength between 350 and 400 MPa, elongation A ≥ 25%, yield strength ratio between 0.72 and 0.79, and impact energy ≥ 80 J at -40°C.

[0028] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions based on the principles of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A 345MPa grade atmospheric corrosion resistant steel plate with an extremely low yield ratio, characterized in that: Its chemical composition and mass percentage are as follows: C: 0.06-0.12%, Si: 0.15-0.40%, Mn: 0.30-0.60%, P: 0.060-0.120%, S: ≤0.010%, Cr: 0.30-0.50%, Ni: 0.15-0.35%, Cu: 0.25-0.50%, Nb: 0.010-0.035%, Ti: 0.005-0.030%, Alt: 0.020-0.045%, and the balance is Fe and impurities.

2. The 345MPa grade atmospheric corrosion resistant steel plate according to claim 1, characterized in that: The thickness of the steel plate is 8-20 mm.

3. The 345MPa grade atmospheric corrosion resistant steel plate according to claim 1, characterized in that: The steel plate has a yield strength of 350-400 MPa, an elongation A of ≥25%, a yield strength ratio of 0.72-0.79, and an impact energy of ≥80J at -40°C.

4. The method for producing a 345 MPa grade atmospheric corrosion resistant steel plate with an extremely low yield ratio according to any one of claims 1 to 3, comprising smelting, continuous casting and rolling, wherein: In the rolling step, two-stage rolling is adopted, the rough rolling temperature is 900-1150°C; the start rolling temperature of the finishing rolling is 850-950°C; and the final rolling temperature of the finishing rolling is 800-850°C.

5. The production method according to claim 4, characterized in that After finishing rolling, laminar cooling is carried out, the red-return temperature is 450-600°C, and the cooling rate is 1-20°C / s.

6. The production method according to claim 4, characterized in that The smelting specifically includes: pre-desulfurization through molten iron pretreatment, converter blowing, LF refining to adjust alloy composition, RH vacuum treatment to improve molten steel purity, and calcium treatment after soft stirring.

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