A method for preparing hot-rolled steel plate with yield strength of 550 MPa, high and low temperature toughness, and sulfuric acid corrosion resistance

Abstract

This invention discloses a method for preparing a hot-rolled steel plate with a yield strength of 550 MPa and high and low temperature toughness resistant to sulfuric acid corrosion. Its chemical composition, by weight percentage, is: C: 0.08–0.10%, Si: 0.25–0.35%, Mn: 0.81–0.89%, P≤0.015%, S≤0.010%, Cu: 0.35–0.45%, Cr: 0.75–0.90%, Ni: 0.20–0.35%, Ti: 0.04–0.05%, Sb: 0.09–0.14%, Als: 0.020–0.035%, Ce: 0.0009–0.0014%. The main process parameters of the preparation method are also disclosed. This invention, through reasonable composition design and appropriate process, can obtain a hot-rolled steel plate with excellent resistance to sulfuric acid corrosion.

Description

Technical Field

[0001] This invention relates to the field of corrosion-resistant steel technology, and in particular to a method for preparing a hot-rolled steel plate with high and low temperature toughness and resistance to sulfuric acid corrosion with a yield strength of 550 MPa. Background Technology

[0002] Steel is widely used in various industries, operating in diverse environments, especially those with sulfuric acid corrosion. Currently, coal is the primary fuel used by coal enterprises, and high-sulfur coal easily produces sulfate ions, which corrode the steel it comes into contact with. The transportation of high-sulfur coal and minerals also easily corrodes steel. Over 90% of desulfurization devices use wet desulfurization, which increases the dilute sulfuric acid content in the flue gas after desulfurization, causing sulfuric acid corrosion to the flue gas treatment system and surrounding areas. Using sulfuric acid-resistant steel is one of the most effective solutions. With the increasing demand for lightweight development, using high-strength sulfuric acid-resistant steel not only improves strength but also effectively reduces material consumption, lowers overall costs, and achieves the goal of carbon reduction and emission reduction. Therefore, the development of sulfuric acid-resistant steel plates has become an inevitable trend.

[0003] Patent publication number CN 113862570 A discloses a high-strength steel resistant to sulfuric acid dew point corrosion and its production method, belonging to the field of steel production. Its chemical composition and mass percentage are as follows: C: 0.03–0.07%, Si: 0.20–0.30%, Mn: 1.20–1.60%, P: ≤0.020%, S≤0.020%, Cu: 0.20–0.55%, Ni: 0.12–0.20%, Cr: 0.30–0.60%, Mo: 0.15–0.25%, Al: 0.015–0.040%; the balance is Fe and unavoidable impurities. Its characteristics are corrosion resistance and high strength. The composition design of the above-mentioned invention is significantly different from that of this invention, and the low-temperature impact toughness of this invention is significantly superior.

[0004] The invention disclosed in Publication No. CN 115637391 B provides a rare earth steel for 550MPa grade sulfuric acid dew point corrosion resistance and its manufacturing method. The composition of the steel, by weight percentage, is as follows: C: 0.072%–0.093%, Si: 0.31%–0.54%, Mn: 0.63%–0.94%, P: ≤0.017%, S: ≤0.0050%, Cr: 0.82%–1.07%, Ni: 0.21%–0.32%, Cu: 0.13%–0.23%, Sb: 0.092%–0.12%. The rare earth steel produced by this invention has the following composition: 2%, Ti: 0.054%–0.075%, Sn: 0.38%–0.53%, Als: 0.016%–0.039%, Ce: 0.031%–0.041%, O: ≤4.2ppm, with the balance being Fe and unavoidable impurities. The manufacturing method includes smelting, continuous casting, billet heating, rolling, laminar flow cooling, and coiling. The yield strength of the rare earth steel produced by this invention is greater than 550 MPa, the tensile strength is between 682 and 694 MPa, and the elongation is greater than 26%. The composition design and rolling cooling process of the aforementioned invention are significantly different from those of this invention, and the low-temperature impact toughness of this invention is significantly superior.

[0005] Application publication number: CN 115652209 Invention A provides a 650MPa grade rare earth steel resistant to sulfuric acid dew point corrosion and its manufacturing method. The composition of the steel, by weight percentage, is as follows: C: 0.074%–0.095%, Si: 0.41%–0.64%, Mn: 0.87%–1.18%, P: ≤0.017%, S: ≤0.0050%, Cr: 0.92%–1.17%, Ni: 0.26%–0.37%, Cu: 0.16%–0.26%, Sb: 0.102%–0.132%, Ti: 0.064%–0.085%, Sn: 0.58%–0.73%, Als: 0.018%–0.041%, Ce: 0.048%–0.058%, O: ≤3.8ppm, with the balance being Fe and unavoidable impurities. The manufacturing method includes smelting, continuous casting, billet heating, rolling, laminar flow cooling, and coiling; the rare earth steel produced by this invention has a yield strength greater than 650 MPa, a tensile strength between 759 and 791 MPa, and an elongation greater than 19%. The composition design and rolling and cooling process of the above-mentioned invention are significantly different from those of this invention, and the low-temperature impact toughness of this invention is significantly superior. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a hot-rolled steel plate with high and low temperature toughness and sulfuric acid corrosion resistance with a yield strength of 550MPa. Through reasonable composition design and appropriate process, a hot-rolled steel plate with good sulfuric acid corrosion resistance can be obtained.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] This invention discloses a method for preparing a hot-rolled steel plate with a yield strength of 550 MPa and high and low temperature toughness resistant to sulfuric acid corrosion. The chemical composition of the steel plate, by weight percentage, is: C: 0.08-0.10%, Si: 0.25-0.35%, Mn: 0.81-0.89%, P≤0.015%, S≤0.010%, Cu: 0.35-0.45%, Cr: 0.75-0.90%, Ni: 0.20-0.35%, Ti: 0.04-0.05%, Sb: 0.09-0.14%, Als: 0.020-0.035%, Ce: 0.0009-0.0014%, with the balance being Fe and unavoidable impurities. The main process parameters of the preparation method are as follows:

[0009] The molten iron used for smelting and casting is pre-treated by desulfurization and then sent to the LF refining furnace for refining to ensure that the steel composition and temperature are ≥1620℃. RH vacuum treatment is performed to ensure the vacuum degree and the vacuum treatment time is ≥20min. Rare earth cerium-iron alloy is added after 15min of vacuum treatment and the soft blowing time is ≥10min.

[0010] Protective casting should be used during the casting process. During continuous casting, the casting speed should be kept stable. The casting speed should be selected within the range of 0.9 to 1.6 m / min, and then kept as constant as possible.

[0011] The slab is heated to 1190–1250℃, in the furnace for 180–300 min, and exited from the furnace at 1180–1230℃. Hot rolling is carried out in two stages: the initial rolling temperature in the austenite recrystallization zone is ≥1100℃, the initial rolling temperature in the austenite non-recrystallization zone is 940–1030℃, the final rolling temperature is 820–850℃, and the slab is rapidly cooled to 550–580℃ after rolling. The slab is then rolled into a coil and air-cooled in the warehouse.

[0012] Furthermore, the thickness of the steel plate ranges from 5mm to 12mm.

[0013] Furthermore, the chemical composition of the steel plate by weight percentage is C: 0.085%, Si: 0.34%, Mn: 0.89%, P: 0.012%, S: 0.005%, Cu: 0.37%, Cr: 0.77%, Ni: 0.20%, Ti: 0.049%, Sb: 0.14%, Als: 0.034%, Ce: 0.0009%, with the balance being Fe and unavoidable impurities.

[0014] Furthermore, the chemical composition of the steel plate by weight percentage is C: 0.088%, Si: 0.27%, Mn: 0.87%, P: 0.012%, S: 0.005%, Cu: 0.42%, Cr: 0.89%, Ni: 0.25%, Ti: 0.047%, Sb: 0.12%, Als: 0.031%, Ce: 0.0012%, with the balance being Fe and unavoidable impurities.

[0015] Furthermore, the chemical composition of the steel plate by weight percentage is C: 0.097%, Si: 0.25%, Mn: 0.82%, P: 0.012%, S: 0.004%, Cu: 0.45%, Cr: 0.90%, Ni: 0.33%, Ti: 0.042%, Sb: 0.09%, Als: 0.023%, Ce: 0.0014%, with the balance being Fe and unavoidable impurities.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0017] The beneficial effects of this invention are that by employing a multi-element microalloying scheme treated with rare earth cerium and combined with appropriate processes, a hot-rolled steel sheet with a yield strength of 550 MPa and resistance to sulfuric acid corrosion can be obtained. It possesses good resistance to sulfuric acid corrosion while also exhibiting high low-temperature impact toughness, making it suitable for low-temperature environments. Detailed Implementation

[0018] A hot-rolled steel sheet with a yield strength of 550 MPa and resistant to sulfuric acid corrosion, and its preparation method, are disclosed. The method employs a multi-element microalloying scheme treated with rare earth cerium, combined with appropriate processes, to obtain a hot-rolled steel sheet with a yield strength of 550 MPa and resistant to sulfuric acid corrosion. It exhibits good resistance to sulfuric acid corrosion while also possessing high low-temperature impact toughness, making it suitable for low-temperature environments.

[0019] The production method specifically includes the following steps:

[0020] 1. Smelting and casting

[0021] The molten iron for smelting is pretreated by desulfurization and then sent to the LF refining furnace for refining to ensure that the composition and temperature of the molten steel are ≥1620℃. It is then subjected to RH vacuum treatment to ensure the vacuum degree and the vacuum treatment time is ≥20min. Rare earth cerium-iron alloy is added after 15min of vacuum treatment, and the soft blowing time is ≥10min.

[0022] 2. Continuous casting

[0023] Protective casting should be used during the casting process. During continuous casting, the casting speed should be kept stable. The casting speed should be selected within the range of 0.9 to 1.6 m / min, and then the casting speed should be kept as constant as possible.

[0024] 3. Heating and rolling

[0025] The slab is heated to 1190-1250℃, with a furnace time of 180-300 minutes, and a furnace exit temperature of 1180-1230℃. Hot rolling adopts a two-stage controlled rolling process: the initial rolling temperature in the austenite recrystallization zone is ≥1100℃, the initial rolling temperature in the austenite non-recrystallization zone is 940-1030℃, and the final rolling temperature is 820-850℃. After rolling, the slab is rapidly cooled to 550-580℃, and then the steel plate is rolled into a coil and air-cooled in a warehouse.

[0026] Example 1

[0027] The chemical composition of Example 1 is shown in Table 1, the mechanical properties are shown in Table 2, and the corrosion test results of the steel plate at 27°C, 20% sulfuric acid concentration, and 24h are shown in Table 3.

[0028] The slab is heated to 1245℃. Hot rolling employs a two-stage controlled rolling process: the initial finishing rolling temperature is 1020℃, the final rolling temperature is 845℃, and after rolling, it is rapidly cooled to 575℃ and coiled, then air-cooled to room temperature. This yields the steel plate.

[0029] Example 2

[0030] The chemical composition of Example 2 is shown in Table 1, the mechanical properties are shown in Table 2, and the corrosion test results of the steel plate at 27°C, 20% sulfuric acid concentration, and 24h are shown in Table 3.

[0031] The slab is heated to 1210℃, and hot rolling is carried out using a two-stage controlled rolling process. The initial rolling temperature for finishing is 980℃, and the final rolling temperature is 835℃. After rolling, the slab is rapidly cooled to 565℃ and then coiled, followed by air cooling to room temperature. This yields the steel plate.

[0032] Example 3

[0033] The chemical composition of Example 3 is shown in Table 1, the mechanical properties are shown in Table 2, and the corrosion test results of the steel plate at 27°C, 20% sulfuric acid concentration, and 24h are shown in Table 3.

[0034] The slab is heated to 1198℃, and hot rolling is carried out using a two-stage controlled rolling process. The initial rolling temperature for finishing is 955℃, and the final rolling temperature is 827℃. After rolling, the slab is rapidly cooled to 558℃ and then coiled, followed by air cooling to room temperature. This yields the steel plate.

[0035] Table 1: Chemical composition of steel plates (wt%)

[0036]

[0037] Table 2: Steel Plate Properties

[0038]

[0039] Table 3 Corrosion test results of steel plate examples of the present invention

[0040]

[0041]

[0042] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a hot-rolled steel plate with a yield strength of 550 MPa and high and low temperature toughness and resistance to sulfuric acid corrosion, characterized in that: The chemical composition of the steel plate, by weight percentage, is: C: 0.08–0.10%, Si: 0.25–0.35%, Mn: 0.81–0.89%, P≤0.015%, S≤0.010%, Cu: 0.35–0.45%, Cr: 0.75–0.90%, Ni: 0.20–0.35%, Ti: 0.04–0.05%, Sb: 0.09–0.14%, Als: 0.020–0.035%, Ce: 0.0009–0.0014%, with the balance being Fe and unavoidable impurities. The main process parameters for its preparation are as follows: The molten iron used for smelting and casting is pre-treated by desulfurization and then sent to the LF refining furnace for refining to ensure that the steel composition and temperature are ≥1620℃. RH vacuum treatment is performed to ensure the vacuum degree and the vacuum treatment time is ≥20min. Rare earth cerium-iron alloy is added after 15min of vacuum treatment and the soft blowing time is ≥10min. Protective casting should be used during the casting process. During continuous casting, the casting speed should be kept stable. The casting speed should be selected within the range of 0.9 to 1.6 m / min, and then kept as constant as possible. The slab is heated to 1190–1250℃, in the furnace for 180–300 min, and exited from the furnace at 1180–1230℃. Hot rolling is carried out in two stages: the initial rolling temperature in the austenite recrystallization zone is ≥1100℃, the initial rolling temperature in the austenite non-recrystallization zone is 940–1030℃, the final rolling temperature is 820–850℃, and the slab is rapidly cooled to 550–580℃ after rolling. The slab is then rolled into a coil and air-cooled in the warehouse.

2. The method for preparing hot-rolled steel plate with a yield strength of 550 MPa, high and low temperature toughness, and resistance to sulfuric acid corrosion according to claim 1, characterized in that: The thickness of the steel plate ranges from 5mm to 12mm.

3. The method for preparing high and low temperature toughness and sulfuric acid corrosion resistant hot-rolled steel plate with a yield strength of 550 MPa according to claim 1, characterized in that: The chemical composition of the steel plate, by weight percentage, is C: 0.085%, Si: 0.34%, Mn: 0.89%, P: 0.012%, S: 0.005%, Cu: 0.37%, Cr: 0.77%, Ni: 0.20%, Ti: 0.049%, Sb: 0.14%, Als: 0.034%, Ce: 0.0009%, with the balance being Fe and unavoidable impurities.

4. The method for preparing hot-rolled steel plate with a yield strength of 550 MPa, high and low temperature toughness, and resistance to sulfuric acid corrosion according to claim 1, characterized in that: The chemical composition of the steel plate by weight percentage is: C: 0.088%, Si: 0.27%, Mn: 0.87%, P: 0.012%, S: 0.005%, Cu: 0.42%, Cr: 0.89%, Ni: 0.25%, Ti: 0.047%, Sb: 0.12%, Als: 0.031%, Ce: 0.0012%, with the balance being Fe and unavoidable impurities.

5. The method for preparing hot-rolled steel plate with a yield strength of 550 MPa, high and low temperature toughness, and resistance to sulfuric acid corrosion according to claim 1, characterized in that: The chemical composition of the steel plate, by weight percentage, is C: 0.097%, Si: 0.25%, Mn: 0.82%, P: 0.012%, S: 0.004%, Cu: 0.45%, Cr: 0.90%, Ni: 0.33%, Ti: 0.042%, Sb: 0.09%, Als: 0.023%, Ce: 0.0014%, with the balance being Fe and unavoidable impurities.

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