A method for controlling cracks of a Q450NQR1 peritectic weathering steel shaped blank

Abstract

This invention discloses a method for controlling cracks in Q450NQR1 peritectic weathering steel shaped billets, comprising: hot metal pretreatment; converter smelting; LF refining; and continuous casting. The chemical composition percentage requirements for the shaped billet are: C: 0.08-0.11%, Mn: 1.20-1.30%, Si: 0.40-0.50%, P: ≤0.015%, S: ≤0.008%, V: 0.11-0.13%, Cr: 0.35-0.45%, Ni: 0.30-0.35%, Cu: 0.26-0.36%, Nb: 0.02-0.04%, N: 0.01-0.012%, with the remainder being iron and unavoidable trace amounts of chemical elements. The purpose of this invention is to solve the problem of billet cracking in Q450NQR1 peritectic weathering steel shaped billets.

Description

Technical Field

[0001] This invention belongs to the field of materials metallurgy technology, and in particular relates to a method for controlling cracks in Q450NQR1 peritectic weathering steel shaped billets. Background Technology

[0002] The cross-section of the irregular billet is complex, and the thickness varies in different directions. The uneven cooling rate during the billet cooling process leads to inconsistent internal stresses. When the internal stress exceeds the tensile strength of the billet, longitudinal or transverse cracks will appear in the billet.

[0003] Patent CN 116287978 B discloses a low-crack-rate carbon structural steel billet and its production method. The chemical composition by mass percentage includes: C 0.12-0.20%, Si 0.10-0.35%, Mn 0.30-0.70%, P≤0.030%, S≤0.008%, V≤0.005%, Cr≤0.01%, Ni≤0.01%, Mo≤0.01%, Cu≤0.01%, N≤0.012%, with the remainder being Fe and impurities, totaling 100% by mass. This chemical composition does not belong to peritectic weathering steel and cannot solve the cracking problem in the production of high-strength peritectic weathering steel.

[0004] Patent CN 117904534 A discloses a special-shaped billet for weathering hot-rolled H-beams and its production process. The composition is: C 0.08-0.14%, Si 0.45-0.65%, Mn 1.40-1.55%, P≤0.030%, S≤0.015%, Cu 0.20-0.30%, Ni 0.20-0.30%, Cr 0.20-0.30%, V 0.10-0.14%, with the balance being Fe and unavoidable impurities. Although its chemical composition belongs to peritectic weathering steel, the invention focuses on the production process of Q420NQR1 special-shaped billets, while this invention focuses on the production of Q450NQR1 special-shaped billets; the chemical composition of the two is not significantly different.

[0005] Patent CN 110788293 B discloses "A continuous casting process for special-shaped billets for high weather-resistant hot-rolled H-beams". Its production process is mainly for S450EW material, which has a significantly different chemical composition from the Q450NQR1 material developed in this invention patent. Therefore, it cannot guide the production practice of this invention patent.

[0006] Currently, all materials produced using special-shaped billet casting machines in China, whether carbon steel, peritectic steel, or peritectic weathering steel, exhibit varying degrees of billet cracking. Peritectic weathering steel has a higher probability of cracking, which seriously affects the economic and technical indicators of subsequent rolled steel products—the yield rate. Summary of the Invention

[0007] The purpose of this invention is to provide a method for controlling cracks in Q450NQR1 peritectic weathering steel shaped billets, so as to solve the problem of cracking in Q450NQR1 peritectic weathering steel shaped billets.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] This invention discloses a method for controlling cracks in Q450NQR1 peritectic weathering steel shaped billets, comprising:

[0010] Hot metal pretreatment: Slag removal is carried out before and after KR desulfurization to ensure that the S content of the hot metal entering the converter is ≤0.008% and to guarantee the desulfurization rate of the hot metal;

[0011] Strictly control the converter charging amount to 100±2 tons, of which 97-98 tons are molten iron and 2-3 tons are scrap steel.

[0012] Converter smelting: Cu, Cr, Ni and other alloys are added to the converter. The alloys must be baked at a temperature ≥400℃. The H content at the end of the converter measurement must be ≤4ppm.

[0013] The carbon content of the converter steel is controlled between 0.08-0.11%, the tapping temperature is controlled above 1610℃, and the basicity of the final slag is controlled between 3.5-4.0.

[0014] LF refining: Argon blowing is used throughout the process, low-aluminum deoxidation is adopted, the Al content of the refined product is ≤0.010%, the soft blowing time is ≥25 minutes, and the alkalinity of the white slag is controlled between 4.0 and 4.5.

[0015] Continuous casting: Before continuous casting, perform crystallizer arc alignment operation, vibration table polarization ≤0.3mm, inner and outer arc ≤0.2mm;

[0016] Total water flow rate in the continuous casting shaped billet crystallizer: 180±5m 3 / h, specifically allocated as a wide-area flow rate of 58±1m³ / h. 3 / h, narrow face flow rate 29±1m 3 / h;

[0017] The flow rate control in the secondary cooling zone of continuously cast irregular-shaped billets is as follows:

[0018] 1) The total flow rate is controlled at 0.52L / kg. In Zone A, the inner arc is 0.083-0.093L / kg, the outer arc is 0.083-0.093L / kg, and both sides are 0.072-0.082L / kg.

[0019] 2) In Zone B, the inner arc is 0.045-0.048 L / kg, the outer arc is 0.032-0.042 L / kg, and both sides are 0.028-0.038 L / kg;

[0020] 3) Inner arc of zone two: 0.021-0.031 L / kg, outer arc: 0.019-0.029 L / kg, both sides: 0.014-0.024 L / kg;

[0021] The pulling speed of the irregular-shaped billet is controlled by a stopper rod, and the fluctuation range of the liquid level in the crystallizer is controlled within ±2mm.

[0022] For irregularly shaped billets with a cross section of 730mm×370mm×90mm, the superheat should be controlled between 35-40℃ and the drawing speed should be controlled between 0.80-0.85m / min.

[0023] Slow cooling time for cast billets ≥ 72 hours;

[0024] The chemical composition percentage requirements for the shaped billet are as follows: C: 0.08-0.11%, Mn: 1.20-1.30%, Si: 0.40-0.50%, P: ≤0.015%, S: ≤0.008%, V: 0.11-0.13%, Cr: 0.35-0.45%, Ni: 0.30-0.35%, Cu: 0.26-0.36%, Nb: 0.02-0.04%, N: 0.01-0.012%, with the remainder being iron and unavoidable trace amounts of chemical elements.

[0025] Furthermore, the scrap steel is low-carbon, high-quality scrap steel.

[0026] Furthermore, the protective slag is a special protective slag for peritectic steel, with basicity controlled between 1.20 and 1.32, melting point between 1150 and 1250℃, and viscosity between 1.2 and 1.5 PS.

[0027] Furthermore, the chemical composition percentage requirements for the shaped billet are as follows: C: 0.09%, Mn: 1.28%, Si: 0.45%, P: 0.012%, S: 0.005%, V: 0.12%, Cr: 0.35%, Ni: 0.31%, Cu: 0.28%, Nb: 0.02%, N: 0.010%, with the remainder being iron and unavoidable trace amounts of chemical elements.

[0028] Furthermore, the chemical composition percentage requirements for the shaped billet are as follows: C: 0.10%, Mn: 1.25%, Si: 0.44%, P: 0.010%, S: 0.003%, V: 0.12%, Cr: 0.35%, Ni: 0.32%, Cu: 0.28%, Nb: 0.03%, N: 0.011%, with the remainder being iron and unavoidable trace amounts of chemical elements.

[0029] Furthermore, the chemical composition percentage requirements for the shaped billet are as follows: C: 0.09%, Mn: 1.23%, Si: 0.42%, P: 0.011%, S: 0.003%, V: 0.12%, Cr: 0.36%, Ni: 0.31%, Cu: 0.29%, Nb: 0.02%, N: 0.010%, with the remainder being iron and unavoidable trace amounts of chemical elements.

[0030] Furthermore, the basicity of the protective slag is controlled at 1.24, the melting point is between 1174-1175℃, and the viscosity is between 1.35 PS.

[0031] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0032] Compared with existing technologies, this invention addresses the problem of surface cracks in high-strength weathering steel billets with a 730mm×370mm×90mm cross-section during continuous casting. This is achieved through a series of measures, including precise control of crack-sensitive elements S and P during the steelmaking process, and strict requirements for crystallizer cooling, secondary cooling zone cooling, and continuous casting protective slag. These measures effectively improve the surface cracking of high-strength weathering steel billets produced from shaped billets, increasing the product yield from 62% to over 82%. Attached Figure Description

[0033] The present invention will be further described below with reference to the accompanying drawings.

[0034] Figure 1 Photographs of longitudinal cracks in the cast billet before the implementation of this invention;

[0035] Figure 2 Macroscopic photograph of the cast billet after implementation of this invention. Detailed Implementation

[0036] The present invention will be further illustrated by specific embodiments below. These embodiments are for illustrative purposes only, and the scope of protection of the present invention is not limited to these embodiments.

[0037] The present invention will be further described below:

[0038] Table 1 shows the percentage content of chemical components of Q450NQR1 in various embodiments of the present invention.

[0039] Example C Si Mn P S V Cu Cr Ni Nb N 1 0.09 0.45 1.28 0.012 0.005 0.12 0.28 0.35 0.31 0.02 0.010 2 0.10 0.44 1.25 0.010 0.003 0.12 0.28 0.35 0.32 0.03 0.011 3 0.09 0.42 1.23 0.011 0.003 0.12 0.29 0.36 0.31 0.02 0.010

[0040] Table 2 shows the smelting process control parameters in the embodiments of the present invention.

[0041] Example KR deS% Converter H / ppm Converter final slag basicity Steel output C / % LF soft blow time / min LF final residue alkalinity 1 0.005 3.56 3.6 0.09 30 4.2 2 0.004 3.61 3.7 0.10 28 4.1 3 0.005 3.52 3.6 0.10 30 4.2

[0042] Table 3 shows the continuous casting process parameters in the embodiments of the present invention.

[0043] Example <![CDATA[Total water volume of the mold / m 3 / h]]> <![CDATA[Flow rate of the wide face of the mold / m 3 / h]]> <![CDATA[Flow rate of the narrow face of the mold / m 3 / h]]> Second Cooling Zone, Section A Inner Arc / L / kg Second Cooling Zone, Section A Outer Arc / L / kg Second Cooling Zone, Section B Inner Arc / L / kg Second Cooling Zone, Section B Outer Arc / L / kg 1 184 57 29 0.085 0.084 0.046 0.034 2 185 57 29 0.084 0.084 0.047 0.035 3 184 58 28 0.085 0.083 0.046 0.036

[0044] Continued from Table 3

[0045] Example Second Cooling Zone, Inner Arc / L / kg Second Cooling Zone 2 Outer Arc / L / kg Superheat / °C Pulling speed / m / min protective slag alkalinity Protective flux viscosity / PS Melting point of protective slag / °C 1 0.026 0.023 36 0.83 1.24 1.35 1175 2 0.027 0.022 37 0.83 1.24 1.35 1174 3 0.027 0.024 36 0.84 1.24 1.35 1175

[0046] As can be seen from Tables 1 and 2, the chemical composition and smelting process of each embodiment are within the scope of the claims of this invention patent, and the smelting composition and smelting process are well controlled.

[0047] As can be seen from Table 3, the continuous casting process parameters of each embodiment all fall within the protection scope of this invention patent.

[0048] Table 4 Crack Rate (%) in Examples

[0049] Example Slab crack rate Product success rate 1 3% 88% 2 4% 87% 3 4% 89%

[0050] 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 controlling cracks in Q450NQR1 peritectic weathering steel shaped billets, characterized in that, include: Hot metal pretreatment: Slag removal is carried out before and after KR desulfurization to ensure that the S content of the hot metal entering the converter is ≤0.008% and to guarantee the desulfurization rate of the hot metal; Strictly control the converter charging amount to 100±2 tons, of which 97-98 tons are molten iron and 2-3 tons are scrap steel. Converter smelting: Cu, Cr and Ni alloys are added to the converter. The alloys must be baked at a temperature ≥400℃. The H content at the converter endpoint must be ≤4ppm. The carbon content of the converter steel is controlled between 0.08-0.11%, the tapping temperature is controlled above 1610℃, and the basicity of the final slag is controlled between 3.5-4.

0. LF refining: Argon blowing is used throughout the process, low-aluminum deoxidation is adopted, the Al content of the refined product is ≤0.010%, the soft blowing time is ≥25 minutes, and the alkalinity of the white slag is controlled between 4.0 and 4.

5. Continuous casting: Before continuous casting, perform crystallizer arc alignment operation, vibration table polarization ≤0.3mm, inner and outer arc ≤0.2mm; The total flow of water for the continuous casting beam blank mold is 180±5m 3 / h, and the specific distribution is 58±1m 3 / h for the wide face flow, and 29±1m 3 / h for the narrow face flow; The flow rate control in the secondary cooling zone of continuously cast irregular-shaped billets is as follows: 1) The total flow rate is controlled at 0.52L / kg. In Zone A, the inner arc is 0.083-0.093L / kg, the outer arc is 0.083-0.093L / kg, and both sides are 0.072-0.082L / kg. 2) In Zone B, the inner arc is 0.045-0.048 L / kg, the outer arc is 0.032-0.042 L / kg, and both sides are 0.028-0.038 L / kg; 3) Inner arc of zone two: 0.021-0.031 L / kg, outer arc: 0.019-0.029 L / kg, both sides: 0.014-0.024 L / kg; The pulling speed of the irregular-shaped billet is controlled by a stopper rod, and the fluctuation range of the liquid level in the crystallizer is controlled within ±2mm. For a shaped billet with a cross section of 730mm×370mm×90mm, the superheat should be controlled between 35-40℃ and the drawing speed should be controlled between 0.80-0.85m / min. Slow cooling time for cast billets ≥ 72 hours; The chemical composition percentage requirements for the shaped billet are as follows: C: 0.08-0.11%, Mn: 1.20-1.30%, Si: 0.40-0.50%, P: ≤0.015%, S: ≤0.008%, V: 0.11-0.13%, Cr: 0.35-0.45%, Ni: 0.30-0.35%, Cu: 0.26-0.36%, Nb: 0.02-0.04%, N: 0.01-0.012%, with the remainder being iron and unavoidable trace amounts of chemical elements.

2. The method for controlling cracks in Q450NQR1 peritectic weathering steel shaped billets according to claim 1, characterized in that, The scrap steel is low-carbon, high-quality scrap steel.

3. The method for controlling cracks in Q450NQR1 peritectic weathering steel shaped billets according to claim 1, characterized in that, The protective slag used is a special protective slag for peritectic steel, with basicity controlled between 1.20 and 1.32, melting point between 1150 and 1250℃, and viscosity between 1.2 and 1.5 PS.

4. The method for controlling cracks in Q450NQR1 peritectic weathering steel shaped billets according to claim 1, characterized in that, The chemical composition percentage requirements for the shaped billet are as follows: C: 0.09%, Mn: 1.28%, Si: 0.45%, P: 0.012%, S: 0.005%, V: 0.12%, Cr: 0.35%, Ni: 0.31%, Cu: 0.28%, Nb: 0.02%, N: 0.010%, with the remainder being iron and unavoidable trace amounts of chemical elements.

5. The method for controlling cracks in Q450NQR1 peritectic weathering steel shaped billets according to claim 1, characterized in that, The chemical composition percentage requirements for the shaped billet are as follows: C: 0.10%, Mn: 1.25%, Si: 0.44%, P: 0.010%, S: 0.003%, V: 0.12%, Cr: 0.35%, Ni: 0.32%, Cu: 0.28%, Nb: 0.03%, N: 0.011%, with the remainder being iron and unavoidable trace amounts of chemical elements.

6. The method for controlling cracks in Q450NQR1 peritectic weathering steel shaped billets according to claim 1, characterized in that, The chemical composition percentage requirements for the shaped billet are as follows: C: 0.09%, Mn: 1.23%, Si: 0.42%, P: 0.011%, S: 0.003%, V: 0.12%, Cr: 0.36%, Ni: 0.31%, Cu: 0.29%, Nb: 0.02%, N: 0.010%, with the remainder being iron and unavoidable trace amounts of chemical elements.

7. The method for controlling cracks in Q450NQR1 peritectic weathering steel shaped billets according to claim 3, characterized in that, The basicity of the protective slag is controlled at 1.24, the melting point is between 1174-1175℃, and the viscosity is between 1.35 PS.

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