Manufacturing method of rare earth treatment type atmospheric corrosion resistant steel Q550NQR1

Abstract

The invention discloses a manufacturing method of rare earth treatment type atmospheric corrosion resistant steel Q550NQR1. The manufacturing method comprises a steelmaking technological process. Steel rolling technological process; the Q550NQR1 steel is prepared from chemical components in percentage by mass as follows: 0.06%-0.8% of C, 0.15%-0.25% of Si, 1.25%-1.4% of Mn, 0.02%-0.05% of Alt, smaller than or equal to 0.015% of P, smaller than or equal to 0.006% of S, 0.025%-0.036% of Nb, 0.035%-0.045% of Ti, 0.70%-0.80% of Cr, 0.25%-0.35% of Cu, 0.12%-0.22% of Ni, 0.050%-0.1% of La and the balance of Fe and impurities. The purpose of the invention is to realize collaborative improvement of steel strength, toughness, corrosion resistance and welding performance through rare earth microalloying and process optimization.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and particularly relates to a method for manufacturing rare earth treated atmospheric corrosion resistant steel Q550NQR1. Background Technology

[0002] Atmospheric corrosion resistant steel Q550NQR1 is widely used in outdoor structures such as railway freight cars, containers, and bridges. Its composition typically includes elements such as Cu, Cr, and Ni to improve corrosion resistance. However, traditional Q550NQR1 steel still has room for improvement in low-temperature toughness, weldability, and corrosion uniformity. Rare earth elements have the functions of purifying molten steel, modifying inclusions, and refining grains, which can significantly improve the overall performance of the steel. Currently, there are no publicly reported processes for applying rare earth systems to Q550NQR1 steel and achieving stable industrial production. Summary of the Invention

[0003] The purpose of this invention is to provide a manufacturing method for rare earth-treated atmospheric corrosion resistant steel Q550NQR1. Through rare earth microalloying and process optimization, the steel's strength, toughness, corrosion resistance, and weldability are synergistically improved. Its yield strength Rel≥550MPa, tensile strength Rm≥600MPa, elongation A≥18%, cold bending performance is qualified, low-temperature impact energy at -40℃≥60J, and cyclic wetting corrosion resistance≥55% (comparative sample: Q345B).

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention discloses a method for manufacturing rare earth-treated atmospheric corrosion-resistant steel Q550NQR1. The steelmaking process is as follows: blast furnace—KR desulfurization—converter—LF refining—RH furnace—slab continuous casting; the rolling process is as follows: heating furnace—high-pressure water descaling and width-fixing press—E1R1 roughing mill rolling—E2R2 roughing mill rolling—flying shear—high-pressure water descaling—F1~F7 finishing mill rolling—dense laminar flow cooling—coiling; its specific features are:

[0006] The converter tapping temperature is ≥1620℃ to ensure that the composition and temperature are coordinated during tapping; the vacuum degree of the RH process is required to be ≤2.6mbar, and the vacuum time is ≥15min. After calcium treatment, rare earth lanthanum-iron alloy is added to ensure that the soft blowing time is ≥8min; the casting machine in the continuous casting process adopts constant casting speed control, and the casting speed range is 0.9~1.4m / min.

[0007] Heating temperature 1210~1250℃, furnace time 170~270min, furnace exit temperature 1200~1240℃; finishing rolling temperature 835~865℃, coiling temperature 610~650℃.

[0008] The chemical composition of the Q550NQR1 steel by mass percentage is: C: 0.06%~0.8%, Si: 0.15%~0.25%, Mn: 1.25%~1.4%, Alt: 0.02%~0.05%, P: ≤0.015%, S≤0.006%, Nb: 0.025%~0.036%, Ti: 0.035%~0.045%, Cr: 0.70%~0.80%, Cu: 0.25%~0.35%, Ni: 0.12%~0.22%, La: 0.050%~0.1%, with the remainder being Fe and unavoidable inclusions.

[0009] Furthermore, the thickness of the steel strip is 6~20mm.

[0010] Furthermore, the steel strip meets the following requirements: yield strength ≥ 550 MPa, tensile strength > 600 MPa, elongation ≥ 18%, cold bending performance qualified, low temperature impact energy at -40℃ ≥ 60 J, and cyclic wetting corrosion resistance ≥ 55%.

[0011] Furthermore, the chemical composition of the Q550NQR1 steel by mass percentage is C: 0.072%, Si: 0.212%, Mn: 1.29%, Alt: 0.03%, P: 0.010%, S: 0.002%, Nb: 0.035%, Ti: 0.042%, Cr: 0.782%, Cu: 0.345%, Ni: 0.163%, La: 0.061%, with the remainder being Fe and unavoidable inclusions.

[0012] Furthermore, the chemical composition of the Q550NQR1 steel by mass percentage is C: 0.072%, Si: 0.191%, Mn: 1.26%, Alt: 0.03%, P: 0.009%, S: 0.002%, Nb: 0.035%, Ti: 0.042%, Cr: 0.772%, Cu: 0.338%, Ni: 0.163%, La: 0.073%, with the remainder being Fe and unavoidable inclusions.

[0013] Furthermore, the chemical composition of the Q550NQR1 steel by mass percentage is C: 0.071%, Si: 0.193%, Mn: 1.24%, Alt: 0.03%, P: 0.010%, S: 0.002%, Nb: 0.036%, Ti: 0.040%, Cr: 0.728%, Cu: 0.333%, Ni: 0.160%, La: 0.095%, with the remainder being Fe and unavoidable inclusions.

[0014] Furthermore, the rare earth lanthanum-iron alloy is a rare earth lanthanum-iron alloy with a rare earth mass content of 20%.

[0015] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0016] This invention employs a smelting process to ensure the alloy composition and impurity element content. After calcium treatment, lanthanum-iron alloy is added to further purify the molten steel, thereby obtaining molten steel with high purity and qualified alloy composition. Dynamic light pressure is combined to improve the internal quality of the billet, thus ensuring the excellent strength and plasticity of the steel strip.

[0017] The manufacturing method of this invention is simple and low-cost. Through reasonable alloy composition control and precise production process control, high-strength, high-corrosion-resistant weathering steel strip Q550NQR1 can be prepared.

[0018] The steel strip prepared by this invention is a hot-rolled steel strip with high strength and excellent corrosion resistance. Its atmospheric corrosion resistance meets the requirements: yield strength Rel≥550MPa, tensile strength Rm≥600MPa, elongation A≥18%, cold bending performance is qualified, low temperature impact energy at -40℃≥60J, and periodic immersion corrosion resistance≥55% (comparison sample is Q345B). Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings.

[0020] Figure 1 The metallographic morphology of the steel strip in Example 1 is shown, and the microstructure is acicular ferrite. Detailed Implementation

[0021] This invention provides a rare earth-treated atmospheric corrosion resistant steel Q550NQR1 and its manufacturing method. The following specific embodiments further illustrate this invention. These embodiments are for illustrative purposes only, and the scope of protection of this invention is not limited to these embodiments.

[0022] A method for manufacturing rare earth-treated atmospheric corrosion resistant steel Q550NQR1, with specific requirements as follows:

[0023] Controlled Rolling and Controlled Cooling (TMCP) Process: The steel strip is rolled using the TMCP process, with a finishing rolling temperature of 835~865℃, followed by laminar flow cooling, and a coiling temperature of 610~650℃. The thickness of the steel strip is 6~20mm.

[0024] The manufacturing method of this invention ensures the alloy composition and impurity element content through the smelting process. After calcium treatment, lanthanum-iron alloy is added to further purify the molten steel, thereby obtaining molten steel with high purity and qualified alloy composition. Secondly, dynamic light pressing is combined to improve the internal quality of the billet. Macroscopic and microscopic segregation in the center of the billet is reduced, ensuring the excellent strength and plasticity of the steel strip. The toughness of the steel strip is improved by controlling inclusions and metallographic structure.

[0025] This invention develops a manufacturing method for rare-earth treated atmospheric corrosion resistant steel Q550NQR1, forming a complete set of smelting, rolling, and cooling technologies. The manufacturing process is simple and easy to operate, and the product's performance temperature is optimal. The resulting rare-earth treated atmospheric corrosion resistant steel Q550NQR1 exhibits excellent strength, toughness, and corrosion resistance, and has broad application prospects.

[0026] Table 1 shows the weight percentage content of chemical components in the embodiments of the present invention, Tables 2 and 3 show the preparation process parameters of each embodiment of the present invention, Table 4 shows the process test results of mechanical properties in the embodiments of the present invention, and Table 5 shows the periodic immersion test results of this embodiment.

[0027] Table 1 Chemical composition and weight percentage (wt%) of the embodiments of the present invention

[0028] Examples C Si Mn P S Nb Ti Cu Cr Ni La Alt Example 1 0.072 0.212 1.29 0.010 0.002 0.035 0.042 0.345 0.782 0.163 0.061 0.03 Example 2 0.072 0.191 1.26 0.009 0.002 0.035 0.042 0.338 0.772 0.163 0.073 0.03 Example 3 0.071 0.193 1.24 0.010 0.002 0.036 0.04 0.333 0.728 0.160 0.095 0.03

[0029] Table 2 Steelmaking process parameters of embodiments of the present invention

[0030]

[0031] Table 3 Rolling process parameters of the present invention embodiment

[0032]

[0033] Table 4 Mechanical properties of embodiments of the present invention

[0034]

[0035] Table 5. Cyclic wetting performance of embodiments of the present invention

[0036]

[0037] Table 1 shows that the chemical composition of Examples 1 to 3 of the present invention is within the requirements of the present invention patent, and the smelting composition is well controlled.

[0038] Tables 2 and 3 show that the process parameters of steelmaking, rolling, and coiling in Examples 1 to 3 of the present invention are all within the requirements of the present invention patent, and the process parameters of steelmaking, rolling, and coiling are well controlled.

[0039] Table 4 shows that the mechanical properties of Examples 1 to 3 of the present invention all meet the technical requirements.

[0040] Table 5 shows that the periodic immersion corrosion performance of Examples 1 to 3 of the present invention all meet the technical requirements.

[0041] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for manufacturing rare earth-treated atmospheric corrosion resistant steel Q550NQR1, wherein the steelmaking process is as follows: blast furnace—KR desulfurization—converter—LF refining—RH furnace—slab continuous casting; the rolling process is as follows: heating furnace—high-pressure water descaling and width-fixing press—E1R1 roughing mill rolling—E2R2 roughing mill rolling—flying shear—high-pressure water descaling—F1~F7 finishing mill rolling—dense laminar flow cooling—coiling; characterized in that, Specifically: The converter tapping temperature is ≥1620℃ to ensure that the composition and temperature are coordinated during tapping; the vacuum degree of the RH process is required to be ≤2.6mbar, and the vacuum time is ≥15min. 0.20kg / t of φ13mm diameter silicon-calcium wire is fed in for calcium treatment, and then rare earth lanthanum-iron alloy is added to ensure a soft blowing time of ≥8min; the continuous casting process uses constant casting speed control, with a casting speed range of 0.9~1.4m / min. Heating temperature 1210~1250℃, furnace time 170~270min, furnace exit temperature 1200~1240℃; finishing rolling temperature 835~865℃, coiling temperature 610~650℃. The chemical composition of the Q550NQR1 steel by mass percentage is: C: 0.06%~0.8%, Si: 0.15%~0.25%, Mn: 1.25%~1.4%, Alt: 0.02%~0.05%, P: ≤0.015%, S≤0.006%, Nb: 0.025%~0.036%, Ti: 0.035%~0.045%, Cr: 0.70%~0.80%, Cu: 0.25%~0.35%, Ni: 0.12%~0.22%, La: 0.050%~0.1%, with the remainder being Fe and unavoidable inclusions.

2. The method for manufacturing rare earth-treated atmospheric corrosion resistant steel Q550NQR1 according to claim 1, characterized in that, The thickness of the steel strip is 6~20mm.

3. The method for manufacturing rare earth-treated atmospheric corrosion resistant steel Q550NQR1 according to claim 1 or 2, characterized in that, The steel strip meets the following requirements: yield strength ≥ 550 MPa, tensile strength > 600 MPa, elongation ≥ 18%, cold bending performance qualified, low temperature impact energy at -40℃ ≥ 60 J, and cyclic wetting corrosion resistance ≥ 55%.

4. The method for manufacturing rare earth-treated atmospheric corrosion resistant steel Q550NQR1 according to claim 1, characterized in that, The chemical composition of the Q550NQR1 steel by mass percentage is: C: 0.072%, Si: 0.212%, Mn: 1.29%, Alt: 0.03%, P: 0.010%, S: 0.002%, Nb: 0.035%, Ti: 0.042%, Cr: 0.782%, Cu: 0.345%, Ni: 0.163%, La: 0.061%, with the remainder being Fe and unavoidable inclusions.

5. The method for manufacturing rare earth-treated atmospheric corrosion resistant steel Q550NQR1 according to claim 1, characterized in that, The chemical composition of the Q550NQR1 steel by mass percentage is: C: 0.072%, Si: 0.191%, Mn: 1.26%, Alt: 0.03%, P: 0.009%, S: 0.002%, Nb: 0.035%, Ti: 0.042%, Cr: 0.772%, Cu: 0.338%, Ni: 0.163%, La: 0.073%, with the remainder being Fe and unavoidable inclusions.

6. The method for manufacturing rare earth-treated atmospheric corrosion resistant steel Q550NQR1 according to claim 1, characterized in that, The chemical composition of the Q550NQR1 steel by mass percentage is: C: 0.071%, Si: 0.193%, Mn: 1.24%, Alt: 0.03%, P: 0.010%, S: 0.002%, Nb: 0.036%, Ti: 0.04%, Cr: 0.728%, Cu: 0.333%, Ni: 0.160%, La: 0.095%, with the remainder being Fe and unavoidable inclusions.

7. The method for manufacturing rare earth-treated atmospheric corrosion resistant steel Q550NQR1 according to claim 1, characterized in that, The rare earth lanthanum-iron alloy is a rare earth lanthanum-iron alloy with a rare earth mass content of 20%.

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