460MPa-grade corrosion-resistant steel plate with extremely low yield ratio and preparation method of 460MPa-grade corrosion-resistant steel plate

Abstract

The invention discloses a 460MPa-grade corrosion-resistant steel plate with an extremely low yield ratio. The 460MPa-grade corrosion-resistant steel plate comprises the following components in percentage by weight: 0.12%-0.16% of C, 0.30%-0.60% of Si, 1.40%-1.60% of Mn, less than or equal to 0.015% of P, less than or equal to 0.003% of S, 0.45%-0.65% of Cr, 0.10%-0.20% of Ni, 0.30%-0.50% of Cu, 0.025%-0.040% of Nb, 0.010%-0.020% of V, 0.010%-0.025% of Ti, 0.020%-0.050% of Alt and the balance of Fe and impurities. Meanwhile, the invention discloses a preparation method of the corrosion-resistant steel plate. A complex phase structure of ferrite, bainite and martensite is obtained, the structure is uniform and fine, stable yield strength is obtained, and the yield ratio is extremely low.

Description

Technical Field

[0001] The present invention relates to the field of steel smelting, and in particular to a 460MPa-grade corrosion-resistant steel plate with an extremely low yield ratio and a preparation method thereof. Background Art

[0002] Atmospheric corrosion resistant steel refers to a low alloy steel with good atmospheric corrosion resistance, which is made by adding a certain amount of Cu, P, C or Ni, Mo, Nb, Ti and other alloy elements to the steel. In industrial and rural atmospheric environments, weathering steel forms a dense and stable oxide protective film on the surface of its substrate, which hinders the entry of corrosive media and has excellent atmospheric corrosion resistance. However, the rust layer formed by corrosion on the surface of ordinary carbon steel substrate has a loose structure and micro-cracks, which cannot really protect the substrate steel.

[0003] The application of corrosion-resistant steel has many advantages, which can not only reduce the cost of the entire life cycle, but also simplify maintenance and be environmentally friendly. Existing corrosion-resistant steels include:

[0004] For example, patent CN114790532B discloses an alloy corrosion-resistant steel bar and its preparation method, wherein Si: 1.05-2%, Cr: 0.5-2.5% etc. are added to the composition, and the yield strength reaches ≥ 360MPa, which is a corrosion-resistant steel bar. However, the strength grade is low and cannot meet the needs of higher strength grades.

[0005] For example, patent CN117947335A discloses a high-strength corrosion-resistant steel for photovoltaic pile foundations and its manufacturing method. The components include C: 0.05-0.12%, Mo: 0.02-0.15%, etc., and the chemical composition also includes one or two of Sn: 0.01-0.12%, RE: 0.01-0.12%, and the chemical composition must simultaneously meet the following requirements: Cr / (0.54Mo+1.93Al)≥2.0, reaching a yield strength of ≥460MPa, a tensile strength of ≥540MPa, and an elongation of A≥18%. It is a corrosion-resistant steel. However, tin or rare earth elements are also added in the composition design, which not only has high cost, but also has low tensile strength and elongation.

[0006] Therefore, it is necessary to develop new corrosion-resistant steel plates and their preparation methods in a targeted manner to improve product performance. Summary of the invention

[0007] Purpose of the invention: In view of the shortcomings and defects of the prior art, the present invention provides a 460MPa-grade corrosion-resistant steel plate with an extremely low yield ratio and a preparation method thereof, so as to obtain a multiphase structure of "ferrite + bainite + martensite" with a uniform and fine structure, thereby obtaining a stable yield strength and an extremely low yield ratio.

[0008] Technical solution: A 460MPa grade corrosion-resistant steel plate with an extremely low yield ratio of the present invention is characterized in that it comprises the following components in weight percentage: C: 0.12% to 0.16%, Si: 0.30% to 0.60%, Mn: 1.40% to 1.60%, P: ≤0.015%, S: ≤0.003%, Cr: 0.45% to 0.65%, Ni: 0.10% to 0.20%, Cu: 0.30% to 0.50%, Nb: 0.025% to 0.040%, V: 0.010% to 0.020%, Ti: 0.010% to 0.025%, Alt: 0.020% to 0.050%, and the balance is Fe and impurities.

[0009] Preferably, the following components are included in weight percentage: C: 0.14%, Si: 0.35%, Mn: 1.45%, P: 0.013%, S: 0.003%, Cr: 0.50%, Ni: 0.14%, Cu: 0.35%, Nb: 0.030%, V: 0.015%, Ti: 0.015%, Alt: 0.030%, and the balance is Fe and impurities.

[0010] Preferably, the following components are included in weight percentage: C: 0.13%, Si: 0.35%, Mn: 1.40%, P: 0.013%, S: 0.003%, Cr: 0.45%, Ni: 0.15%, Cu: 0.35%, Nb: 0.035%, V: 0.015%, Ti: 0.020%, Alt: 0.030%, and the balance is Fe and impurities.

[0011] Preferably, the following components are included in weight percentage: C: 0.13%, Si: 0.35%, Mn: 1.48%, P: 0.013%, S: 0.003%, Cr: 0.47%, Ni: 0.12%, Cu: 0.35%, Nb: 0.035%, V: 0.015%, Ti: 0.020%, Alt: 0.030%, and the balance is Fe and impurities.

[0012] The method for preparing a 460MPa grade corrosion-resistant steel plate with an extremely low yield ratio of the present invention is characterized by: ensuring the alloy composition and controlling the content of impurity elements through smelting, implementing a calcium treatment smelting process after the refining process, combining a casting process of dynamic light pressure reduction and electromagnetic stirring to improve the internal quality of the ingot; and adopting a process of precise rolling and precise control of cooling in the rolling stage.

[0013] The smelting process ensures the alloy composition and the content of impurity elements, and adopts the smelting process of molten iron pretreatment, calcium treatment and RH vacuum treatment to achieve the control of molten steel purity and inclusions.

[0014] The casting process adopts a casting process of dynamic light pressure reduction and electromagnetic stirring to improve the internal quality of the ingot and reduce the level of central segregation and looseness of the ingot.

[0015] Among them, the process of precise rolling and precise controlled cooling adopts weak cooling to control the cooling rate to a small level in the controlled cooling stage to obtain a metallographic microstructure with both strength and toughness; the comprehensive performance of the steel plate is improved by inclusion control and microstructure control.

[0016] The method for preparing a 460MPa grade corrosion resistant steel plate with an extremely low yield ratio of the present invention is characterized by comprising the steps of smelting, continuous casting, heating and rolling. Specifically, the method comprises the following steps:

[0017] 1) Smelting: Pre-desulfurization by spraying magnesium powder through the molten iron pretreatment process, converter smelting process and converter steel alloying pre-refining, and then LF refining to fine-tune the alloy composition, RH vacuum treatment is used to further improve the purity of the molten steel, and calcium treatment is implemented after soft stirring to ensure that high-purity and qualified molten steel is obtained;

[0018] 2) Continuous casting: Dynamic soft reduction and electromagnetic stirring technology are used to improve the internal quality of the ingot;

[0019] 3) Heating: Put the 260mm thick billet into the heating furnace, the billet is heated to 1150℃~1220℃, the time in the furnace is 200min~375min, and the temperature out of the furnace is 1160℃~1220℃;

[0020] 4) Rolling: Two-stage rolling is adopted, and the two-stage rolling includes rough rolling and finish rolling; the rough rolling temperature is 900℃~1120℃; the start rolling temperature of finish rolling is 860℃~960℃, and the final rolling temperature of finish rolling is 790℃~840℃; followed by laminar cooling, the red return temperature is 570℃~620℃; the cooling rate is 1℃ / s~20℃ / s; the thickness of the finished steel plate is 10mm~50mm.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention forms a complete set of smelting and rolling production technology, the production process is simple and easy to operate, and the product performance is stable. The present invention adopts a smelting process that ensures the alloy composition and controls the content of harmful impurity elements, and at the same time, calcium treatment, combined with a casting process of dynamic light pressure and electromagnetic stirring to improve the internal quality of the ingot and ensure the toughness of the steel plate. The preparation process of the present invention is simple and low in cost. It uses a 260mm thick billet and produces a 460MPa grade corrosion-resistant steel plate with an extremely low yield ratio through a controlled rolling and controlled cooling process. The corrosion-resistant steel plate obtained by the present invention has stable performance: the yield strength is between 460 and 600 MPa, the tensile strength is between 665 and 800 MPa, the elongation A50 is ≥22%, the yield strength ratio is ≤0.80, the corrosion rate of the corrosion-resistant steel is 2.40 to 2.45 mm / a in the automatic periodic immersion corrosion test (industrial atmosphere), the corrosion rate of the low alloy steel is 4.20 to 4.25 mm / a, and the corrosion resistance is low alloy corrosion rate / corrosion resistant steel corrosion rate ≥1.70. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a typical microstructure image of a 16 mm thick corrosion-resistant structural steel plate obtained after rolling production in Example 1 of the present invention under a metallographic microscope;

[0023] Figure 2 This is a typical microstructure image of a 19 mm thick corrosion-resistant structural steel plate obtained after rolling production in Example 2 of the present invention under a metallographic microscope;

[0024] Figure 3 This is a typical microstructure image of a 26 mm thick corrosion-resistant structural steel plate obtained after rolling production in Example 3 of the present invention under a metallographic microscope. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0026] Embodiment 1:

[0027] The 460 MPa grade corrosion-resistant steel plate with an extremely low yield ratio of this embodiment includes the following components in weight percentage: C: 0.14%, Si: 0.35%, Mn: 1.45%, P: 0.013%, S: 0.003%, Cr: 0.50%, Ni: 0.14%, Cu: 0.35%, Nb: 0.030%, V: 0.015%, Ti: 0.015%, Alt: 0.030%, and the balance is Fe and impurities.

[0028] During preparation, a 260 mm thick ingot is placed into a heating furnace, the heating temperature of the ingot is between 1150°C and 1220°C, the time in the furnace is between 200 min and 375 min, and the furnace exit temperature is between 1160°C and 1220°C; two-stage rolling is adopted, and the two-stage rolling includes rough rolling and finish rolling; the rough rolling temperature is between 900°C and 1120°C; the start rolling temperature of finish rolling is between 860°C and 960°C, and the final rolling temperature of finish rolling is between 790°C and 840°C; followed by laminar cooling, the red return temperature is between 570°C and 620°C; the cooling rate is between 1°C / s and 20°C / s.

[0029] like Figure 1 As shown in Table 1-4, the typical microstructure of the 16 mm thick corrosion-resistant structural steel plate obtained after rolling production in Example 1 under a metallographic microscope. It can be found that the microstructure is ferrite + bainite + martensite, and the microstructure is uniform and fine. The complex phase structure of ferrite + bainite + martensite is conducive to obtaining a stable yield strength and has an extremely low yield strength ratio.

[0030] Embodiment 2:

[0031] The 460 MPa grade corrosion-resistant steel plate with an extremely low yield ratio of this embodiment includes the following components in weight percentage: C: 0.13%, Si: 0.35%, Mn: 1.40%, P: 0.013%, S: 0.003%, Cr: 0.45%, Ni: 0.15%, Cu: 0.35%, Nb: 0.035%, V: 0.015%, Ti: 0.020%, Alt: 0.030%, and the balance is Fe and impurities.

[0032] During preparation, a 260 mm thick ingot is placed into a heating furnace, the heating temperature of the ingot is between 1150°C and 1220°C, the time in the furnace is between 200 min and 375 min, and the furnace exit temperature is between 1160°C and 1220°C; two-stage rolling is adopted, and the two-stage rolling includes rough rolling and finish rolling; the rough rolling temperature is between 900°C and 1120°C; the start rolling temperature of finish rolling is between 860°C and 960°C, and the final rolling temperature of finish rolling is between 790°C and 840°C; followed by laminar cooling, the red return temperature is between 570°C and 620°C; the cooling rate is between 1°C / s and 20°C / s.

[0033] like Figure 2 As shown in Table 1-4, the typical microstructure of the 19 mm thick corrosion-resistant structural steel plate obtained after rolling production in Example 2 under a metallographic microscope. It can be found that the microstructure is ferrite + bainite + martensite, and the microstructure is uniform and fine. The complex phase structure of ferrite + bainite + martensite is conducive to obtaining a stable yield strength and has an extremely low yield strength ratio.

[0034] Embodiment 3:

[0035] The 460 MPa grade corrosion-resistant steel plate with an extremely low yield ratio of this embodiment includes the following components in weight percentage: C: 0.13%, Si: 0.35%, Mn: 1.48%, P: 0.013%, S: 0.003%, Cr: 0.47%, Ni: 0.12%, Cu: 0.35%, Nb: 0.035%, V: 0.015%, Ti: 0.020%, Alt: 0.030%, and the balance is Fe and impurities.

[0036] During preparation, a 260 mm thick ingot is placed into a heating furnace, the heating temperature of the ingot is between 1150°C and 1220°C, the time in the furnace is between 200 min and 375 min, and the furnace exit temperature is between 1160°C and 1220°C; two-stage rolling is adopted, and the two-stage rolling includes rough rolling and finish rolling; the rough rolling temperature is between 900°C and 1120°C; the start rolling temperature of finish rolling is between 860°C and 960°C, and the final rolling temperature of finish rolling is between 790°C and 840°C; followed by laminar cooling, the red return temperature is between 570°C and 620°C; the cooling rate is between 1°C / s and 20°C / s.

[0037] like Figure 3 As shown in Table 1-4, the typical microstructure of the 26 mm thick corrosion-resistant structural steel plate obtained after rolling production in Example 3 under a metallographic microscope. It can be found that the microstructure is ferrite + bainite + martensite, and the microstructure is uniform and fine. The complex phase structure of ferrite + bainite + martensite is conducive to obtaining a stable yield strength and has an extremely low yield strength ratio.

[0038] Table 1 - Chemical composition (wt%) of Examples 1-3 of the present invention

[0039]

[0040] Table 2 - Tensile properties of Examples 1-3 of the present invention

[0041]

[0042] Table 3 - 29°C impact performance of Examples 1-3 of the present invention

[0043]

[0044] Table 4 - Average corrosion rate table of corrosion-resistant steel and Q345D of Examples 1-3 of the present invention (weekly immersion corrosion test: simulated industrial atmosphere)

[0045]

[0046] It can be seen that the mechanical properties of Examples 1, 2, and 3 all meet the requirements of 460MPa-grade corrosion-resistant structural steel plates; the specific performance of the steel plates reaches the following levels: yield strength is between 460 and 600MPa, tensile strength is between 665 and 800MPa, elongation A50 ≥ 22%, yield strength ratio ≤ 0.80, and the corrosion rate of corrosion-resistant steel in the automatic periodic immersion corrosion test (industrial atmosphere) is 2.40 to 2.45mm / a, the corrosion rate of low alloy steel is 4.20 to 4.25mm / a, and the corrosion resistance is low alloy corrosion rate / corrosion resistant steel corrosion rate ≥ 1.70.

Claims

1. A 460MPa grade corrosion resistant steel plate with extremely low yield ratio, characterized in that: The invention comprises the following components in weight percentage: C: 0.12% to 0.16%, Si: 0.30% to 0.60%, Mn: 1.40% to 1.60%, P: ≤0.015%, S: ≤0.003%, Cr: 0.45% to 0.65%, Ni: 0.10% to 0.20%, Cu: 0.30% to 0.50%, Nb: 0.025% to 0.040%, V: 0.010% to 0.020%, Ti: 0.010% to 0.025%, Alt: 0.020% to 0.050%, and the balance is Fe and impurities.

2. The 460MPa grade corrosion resistant steel plate with extremely low yield ratio according to claim 1, characterized in that: The present invention comprises the following components in weight percentage: C: 0.14%, Si: 0.35%, Mn: 1.45%, P: 0.013%, S: 0.003%, Cr: 0.50%, Ni: 0.14%, Cu: 0.35%, Nb: 0.030%, V: 0.015%, Ti: 0.015%, Alt: 0.030%, and the balance is Fe and impurities.

3. The 460MPa grade corrosion-resistant steel plate with an extremely low yield ratio according to claim 1, characterized in that: The present invention comprises the following components in weight percentage: C: 0.13%, Si: 0.35%, Mn: 1.40%, P: 0.013%, S: 0.003%, Cr: 0.45%, Ni: 0.15%, Cu: 0.35%, Nb: 0.035%, V: 0.015%, Ti: 0.020%, Alt: 0.030%, and the balance is Fe and impurities.

4. The 460MPa grade corrosion resistant steel plate with extremely low yield ratio according to claim 1, characterized in that: The present invention comprises the following components in weight percentage: C: 0.13%, Si: 0.35%, Mn: 1.48%, P: 0.013%, S: 0.003%, Cr: 0.47%, Ni: 0.12%, Cu: 0.35%, Nb: 0.035%, V: 0.015%, Ti: 0.020%, Alt: 0.030%, and the balance is Fe and impurities.

5. The method for preparing a 460MPa grade corrosion resistant steel plate with an extremely low yield ratio according to claim 1, characterized in that: The alloy composition is ensured and the content of impurity elements is controlled through smelting. A calcium treatment smelting process is implemented after the refining process. The casting process is combined with dynamic soft pressure and electromagnetic stirring to improve the internal quality of the ingot. Precision rolling and precise cooling control are used in the rolling stage.

6. The method for preparing a 460MPa grade corrosion resistant steel plate with an extremely low yield ratio according to claim 5, characterized in that: The smelting process ensures the alloy composition and the content of impurity elements, and adopts the smelting process of molten iron pretreatment, calcium treatment and RH vacuum treatment to achieve the control of molten steel purity and inclusions.

7. The method for preparing a 460MPa grade corrosion resistant steel plate with an extremely low yield ratio according to claim 5, characterized in that: The casting process adopts a casting process of dynamic light pressure reduction and electromagnetic stirring to improve the internal quality of the casting billet and reduce the level of central segregation and looseness of the casting billet.

8. The method for preparing a 460MPa grade corrosion resistant steel plate with an extremely low yield ratio according to claim 5, characterized in that: The process of precise rolling and precise controlled cooling adopts weak cooling to control the cooling rate in the controlled cooling stage to obtain a metallographic microstructure with both strength and toughness; the performance of the steel plate is improved by inclusion control and microstructure control.

9. The method for preparing a 460 MPa grade corrosion resistant steel plate with an extremely low yield ratio according to any one of claims 5 to 8, characterized in that: It includes smelting, continuous casting, heating and rolling steps.

10. The method for preparing a 460MPa grade corrosion resistant steel plate with an extremely low yield ratio according to claim 9, characterized in that: The specific steps include: 1) Smelting: Pre-desulfurization by spraying magnesium powder through the molten iron pretreatment process, converter smelting process and converter steel alloying pre-refining, and then LF refining to fine-tune the alloy composition, RH vacuum treatment is used to further improve the purity of the molten steel, and calcium treatment is implemented after soft stirring to ensure that high-purity and qualified molten steel is obtained; 2) Continuous casting: Dynamic soft reduction and electromagnetic stirring technology are used to improve the internal quality of the ingot; 3) Heating: Put the 260mm thick billet into the heating furnace, the billet is heated to 1150℃~1220℃, the time in the furnace is 200min~375min, and the temperature out of the furnace is 1160℃~1220℃; 4) Rolling: Two-stage rolling is adopted, and the two-stage rolling includes rough rolling and finishing rolling; the rough rolling temperature is 900℃~1120℃; the starting rolling temperature of finishing rolling is 860℃~960℃, and the final rolling temperature of finishing rolling is 790℃~840℃; followed by laminar cooling, the red return temperature is 570℃~620℃; the cooling rate is 1℃ / s~20℃ / s; The thickness of the finished steel plate is 10mm to 50mm.

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