Atmospheric corrosion resistant steel plate with yield ratio lower than 0.75 and production method thereof

Abstract

The invention discloses an atmospheric corrosion resistant steel plate with a yield ratio lower than 0.75. The atmospheric corrosion resistant steel plate comprises the following chemical components in percentage by mass: 0.08 to 0.13 percent of C, 0.40 to 0.65 percent of Si, 0.30 to 0.70 percent of Mn, 0.070 to 0.130 percent of P, less than or equal to 0.010 percent of S, 0.30 to 0.55 percent of Cr, 0.10 to 0.30 percent of Ni, 0.20 to 0.45 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 steel plate has the advantages that the steel plate has a low yield ratio, good plasticity and toughness are obtained, the production cost is reduced, and meanwhile stable product performance is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of high-strength steel plate production technology, and particularly relates to an atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75 and its production method. Background Technology

[0002] Atmospheric corrosion resistant steel, also known as weathering steel, is a low-alloy high-strength steel that significantly delays atmospheric corrosion by adding specific alloying elements such as copper, phosphorus, chromium, and nickel to form a dense protective rust layer. Its characteristics include a stable rust layer after long-term exposure, allowing it to be used without painting, thus combining functionality and aesthetics.

[0003] However, when the yield strength ratio of weathering steel plates is high, although the amount of material used can be reduced and the structural self-weight can be lowered, its plastic deformation capacity is severely reduced, the risk of brittle fracture increases, and the product structure has no obvious warning before it is destroyed, thus the safety is low and the risk of sudden failure is increased. Therefore, a lower yield strength ratio has an important impact on the plastic deformation capacity of weathering steel. How to maintain a low yield strength ratio while being conducive to obtaining good plasticity and toughness is a problem that needs to be solved. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of high yield strength ratio, poor plasticity and toughness, and high safety risks of existing weathering steel. It provides an atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75, which has a low yield strength ratio, good plasticity and toughness, reduces production costs, and ensures stable product performance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A type of atmospheric corrosion resistant steel plate with a yield strength ratio below 0.75 has the following chemical composition and mass percentages: C: 0.08–0.13%, Si: 0.40–0.65%, Mn: 0.30–0.70%, P: 0.070–0.130%, S≤0.010%, Cr: 0.30–0.55%, Ni: 0.10–0.30%, Cu: 0.20–0.45%, Nb: 0.010–0.035%, Ti: 0.005–0.030%, Alt: 0.020–0.045%, with the balance being Fe and impurities. The low manganese content and moderate silicon content help reduce the yield strength, thus lowering the yield strength ratio.

[0006] Furthermore, the chemical composition and its mass percentage of the steel plate include: C: 0.11%, Si: 0.60%, Mn: 0.55%, P: 0.070%, S: 0.0020%, Cr: 0.35%, Ni: 0.15%, Cu: 0.30%, Nb: 0.010%, Ti: 0.015%, Alt: 0.032%, with the balance being Fe and impurities.

[0007] Furthermore, the chemical composition and its mass percentage of the steel plate include: C: 0.10%, Si: 0.65%, Mn: 0.55%, P: 0.065%, S: 0.0010%, Cr: 0.33%, Ni: 0.20%, Cu: 0.25%, Nb: 0.010%, Ti: 0.018%, Alt: 0.031%, with the balance being Fe and impurities.

[0008] Furthermore, the chemical composition and its mass percentage of the steel plate include: C: 0.11%, Si: 0.58%, Mn: 0.47%, P: 0.068%, S: 0.0015%, Cr: 0.30%, Ni: 0.17%, Cu: 0.30%, Nb: 0.012%, Ti: 0.015%, Alt: 0.030%, with the balance being Fe and impurities.

[0009] Furthermore, the thickness of the steel plate is 8~20mm.

[0010] Furthermore, the steel plate has a yield strength between 360 and 450 MPa, an elongation A ≥ 22%, a yield strength ratio less than 0.75, and an impact energy ≥ 100 J at -40℃.

[0011] To further achieve the objectives of this invention, a method for producing atmospheric corrosion resistant steel plates with a yield strength ratio of less than 0.75 is also provided. The specific steps include smelting, continuous casting, and rolling. In the rolling step, a two-stage rolling process is adopted, with a roughing temperature of 900–1150°C, an initial rolling temperature of 820–900°C for finishing, and a final rolling temperature of 800–850°C.

[0012] Furthermore, in the rolling step, laminar flow cooling is performed after finishing rolling, with a reddening temperature of 500-620℃ and a cooling rate of 1-20℃ / s.

[0013] Furthermore, in the smelting steps, the molten iron is pre-treated for desulfurization, then blown in a converter, and then refined by LF to adjust the alloy composition. The purity of the molten steel is improved by RH vacuum treatment, and calcium treatment is carried out after soft stirring to ensure that high-purity molten steel with qualified composition is obtained.

[0014] Compared with the prior art, the advantages of the technical solution of the present invention are as follows: (1) This invention ensures the alloy composition and impurity element content through smelting, and uses a calcium treatment smelting process, continuous casting production combined with dynamic light pressure casting process to improve the internal quality of the billet. In the controlled rolling and controlled cooling stage, a precise rolling and precise control cooling process is adopted to ensure the plasticity and toughness of the steel plate. (2) The manufacturing process of the present invention is simple and the cost is low. The controlled rolling and controlled cooling process produces 345MPa grade atmospheric corrosion resistant steel plates with extremely low yield strength ratio. (3) The steel plate obtained by the manufacturing method of the present invention has stable performance: its yield strength is between 360 and 450 MPa, its elongation A is ≥22%, its yield strength ratio is less than 0.75, and its impact energy at -40℃ is ≥100 J. Attached Figure Description

[0015] Figure 1 The table shows the tensile properties of the steel plates in Examples 1-3 of this invention; Figure 2 The table shows the impact performance of the steel plates in Examples 1-3 of this invention. Detailed Implementation Example 1

[0016] To make the present invention clearer, the following description, in conjunction with the accompanying drawings, further illustrates an atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75 and its production method. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the present invention.

[0017] This embodiment provides an atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75. Its chemical composition and mass percentage include: C: 0.11%, Si: 0.60%, Mn: 0.55%, P: 0.070%, S: 0.0020%, Cr: 0.35%, Ni: 0.15%, Cu: 0.30%, Nb: 0.010%, Ti: 0.015%, Alt: 0.032%, with the balance being Fe and impurities.

[0018] The above-mentioned steel plates are produced using the following methods, specifically including: Controlled rolling and cooling process: A two-stage controlled rolling and cooling process is adopted; the roughing temperature is 900-1150℃; the initial rolling temperature of the finishing rolling is 820-900℃, and the final rolling temperature of the finishing rolling is 800-850℃; followed by laminar flow cooling, with a reddening temperature of 500-620℃; the cooling rate is 1-20℃ / s. The thickness of the finished steel plate is 14mm.

[0019] In the smelting process, the molten iron is pre-treated for desulfurization, then blown in a converter, and then refined by LF to adjust the alloy composition. RH vacuum treatment is used to improve the purity of the molten steel. After soft stirring, calcium treatment is carried out to ensure that high-purity molten steel with qualified composition is obtained.

[0020] The production method of this invention ensures the alloy composition and impurity element content during smelting, and employs smelting processes such as calcium treatment and RH vacuum treatment to ensure the control of inclusions in the steel plate; secondly, continuous casting production combined with dynamic light reduction process improves the internal quality of the billet and reduces the level of macroscopic and microscopic segregation in the center of the billet; precise controlled rolling process, using weak cooling in the controlled cooling stage to control the cooling rate to obtain a tough structure; through inclusion control and structure control, the toughness of the steel plate is improved.

[0021] The tensile and impact properties of the steel plates produced by the above method are as follows: Figure 1 and Figure 2 As shown, its atmospheric corrosion resistance index I is 7.43. Example 2

[0022] This embodiment provides an atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75. Its chemical composition and mass percentage include: C: 0.10%, Si: 0.65%, Mn: 0.55%, P: 0.065%, S: 0.0010%, Cr: 0.33%, Ni: 0.20%, Cu: 0.25%, Nb: 0.010%, Ti: 0.018%, Alt: 0.031%, with the balance being Fe and impurities.

[0023] The above-mentioned steel plates are produced using the following methods, specifically including: Controlled rolling and cooling process: A two-stage controlled rolling and cooling process is adopted; the roughing temperature is 900-1150℃; the initial rolling temperature of the finishing rolling is 820-900℃, and the final rolling temperature of the finishing rolling is 800-850℃; followed by laminar flow cooling, with a reddening temperature of 500-620℃; the cooling rate is 1-20℃ / s. The thickness of the finished steel plate is 14mm.

[0024] The tensile and impact properties of the steel plates produced by the above method are as follows: Figure 1 and Figure 2 As shown, its atmospheric corrosion resistance index I is 7.16. Example 3

[0025] This embodiment provides an atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75. Its chemical composition and mass percentage include: C: 0.11%, Si: 0.58%, Mn: 0.47%, P: 0.068%, S: 0.0015%, Cr: 0.30%, Ni: 0.17%, Cu: 0.30%, Nb: 0.012%, Ti: 0.015%, Alt: 0.030%, with the balance being Fe and impurities.

[0026] The above-mentioned steel plates are produced using the following methods, specifically including: Controlled rolling and cooling process: A two-stage controlled rolling and cooling process is adopted; the roughing temperature is 900-1150℃; the initial rolling temperature of the finishing rolling is 820-900℃, and the final rolling temperature of the finishing rolling is 800-850℃; followed by laminar flow cooling, with a reddening temperature of 500-620℃; the cooling rate is 1-20℃ / s. The thickness of the finished steel plate is 16mm.

[0027] The tensile and impact properties of the steel plates produced by the above method are as follows: Figure 1 and Figure 2 As shown, its atmospheric corrosion resistance index I is 7.33.

[0028] This invention develops a 345MPa grade atmospheric corrosion resistant steel plate with an extremely low yield strength ratio, forming a complete smelting and rolling production technology. The production process is simple and easy to operate, and the product performance is stable. The production method uses flat rolling instead of hot continuous rolling, resulting in a yield strength ratio below 0.75. The 345MPa grade atmospheric corrosion resistant steel plate obtained after rolling has a low yield strength ratio, good plasticity, and can achieve a yield strength between 360 and 450 MPa, an elongation A ≥ 22%, a yield strength ratio below 0.75, and an impact energy ≥ 100 J at -40℃, showing broad application prospects.

[0029] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A steel plate resistant to atmospheric corrosion with a yield strength ratio of less than 0.75, characterized in that: The chemical composition and mass percentage of the steel plate include: C: 0.08-0.13%, Si: 0.40-0.65%, Mn: 0.30-0.70%, P: 0.070-0.130%, S≤0.010%, Cr: 0.30-0.55%, Ni: 0.10-0.30%, Cu: 0.20-0.45%, Nb: 0.010-0.035%, Ti: 0.005-0.030%, Alt: 0.020-0.045%, with the balance being Fe and impurities.

2. The atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75 according to claim 1, characterized in that: The chemical composition and mass percentage of the steel plate include: C: 0.11%, Si: 0.60%, Mn: 0.55%, P: 0.070%, S: 0.0020%, Cr: 0.35%, Ni: 0.15%, Cu: 0.30%, Nb: 0.010%, Ti: 0.015%, Alt: 0.032%, with the balance being Fe and impurities.

3. The atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75 according to claim 1, characterized in that: The chemical composition and mass percentage of the steel plate include: C: 0.10%, Si: 0.65%, Mn: 0.55%, P: 0.065%, S: 0.0010%, Cr: 0.33%, Ni: 0.20%, Cu: 0.25%, Nb: 0.010%, Ti: 0.018%, Alt: 0.031%, with the balance being Fe and impurities.

4. The atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75 according to claim 1, characterized in that: The chemical composition and mass percentage of the steel plate include: C: 0.11%, Si: 0.58%, Mn: 0.47%, P: 0.068%, S: 0.0015%, Cr: 0.30%, Ni: 0.17%, Cu: 0.30%, Nb: 0.012%, Ti: 0.015%, Alt: 0.030%, with the balance being Fe and impurities.

5. The atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75 according to any one of claims 1 to 4, characterized in that: The thickness of the steel plate is 8~20mm.

6. The atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75 according to any one of claims 1 to 4, characterized in that: The steel plate has a yield strength between 360 and 450 MPa, an elongation A ≥ 22%, a yield strength ratio less than 0.75, and an impact energy ≥ 100 J at -40℃.

7. A method for producing an atmospheric corrosion resistant steel plate with a yield strength ratio of less than 0.75 as described in claim 1, comprising the steps of smelting, continuous casting, and rolling, characterized in that: The rolling process employs a two-stage rolling process, with a roughing temperature of 900–1150°C, an initial finishing temperature of 820–900°C, and a final finishing temperature of 800–850°C.

8. The method for producing atmospheric corrosion resistant steel plates with a yield strength ratio of less than 0.75 according to claim 7, characterized in that: In the rolling process, laminar flow cooling is performed after finishing rolling, with a reddening temperature of 500-620℃ and a cooling rate of 1-20℃ / s.

9. The method for producing atmospheric corrosion resistant steel plates with a yield strength ratio of less than 0.75 according to claim 7, characterized in that: In the smelting process, the molten iron is pre-treated for desulfurization, then blown in a converter, and then refined by LF to adjust the alloy composition. RH vacuum treatment is used to improve the purity of the molten steel. After soft stirring, calcium treatment is carried out to ensure that high-purity molten steel with qualified composition is obtained.

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