Method for controlling high-strength weathering peritectic beam blank end transverse cracking

Abstract

The application discloses a high-strength weather-resistant peritectic shaped blank flange end transverse crack control method, controls low-melting-point substance generation, adjusts the secondary cooling water, matches the pulling speed and the superheat, guarantees the shaped blank entering the temperature of the straightening and correcting machine, improves the equipment precision, and adopts the automatic control of the stopper rod. The application effectively controls the generation of the high-strength weather-resistant peritectic shaped blank flange end transverse crack, improves the qualified rate of the high-strength weather-resistant peritectic shaped blank, and controls the transverse crack rate of the cast blank flange end to be below 0.5%.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for controlling transverse cracks at the flange end of a high-strength, weather-resistant peritectic billet. Background Technology

[0002] Atmospheric corrosion resistant steels are now a mature and well-developed field abroad, with detailed regulations governing everything from steel grade development to application and design. Compared to other countries, my country's research and development of atmospheric corrosion resistant steels started later, but with the rapid development of the national economy, they have attracted the attention of relevant domestic departments. During Baotou Steel's first trial production of high-strength, weather-resistant peritectic shaped billets, transverse cracking occurred at the flange ends of the billets, mainly concentrated on the inner arc of the cast billet. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a method for controlling transverse cracks at the flange end of a high-strength, weather-resistant peritectic billet.

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

[0005] This invention discloses a method for controlling transverse cracks at the flange end of a high-strength, weather-resistant, peritectic billet. The method includes controlling the generation of low-melting-point substances, adjusting the secondary cooling water, the matching relationship between drawing speed and superheat, ensuring the temperature of the billet entering the drawing straightener, improving equipment accuracy, and employing automatic stopper rod control. Specifically, it includes:

[0006] To control the generation of low-melting-point substances, Al deoxidation is employed. During the refining process, the residual amount of Al must be strictly controlled, generally between 0.005% and 0.010%. The amount of VN alloy added must be strictly controlled at 0.7 kg / t to avoid the generation of brittle AlN, while ensuring that Cu / Ni ≥ 0.8.

[0007] Adjust the matching relationship between the secondary cooling water, casting speed and superheat. The secondary cooling water is changed from medium cooling to weak cooling. The casting speed is kept constant at 0.85m / min. The superheat is controlled at 30℃-35℃ to increase the temperature of the billet at each position when it enters the straightening machine.

[0008] To ensure that the deformation rate of the continuously cast billet does not vary significantly in the straightening zone, the arc of the continuous casting machine and the spatial position of the straightening point rollers must be accurate. The equipment accuracy has been improved from an error of no more than ±0.30mm to an error of no more than ±0.15mm.

[0009] It adopts a 26mm lower slider and automatic stopper rod control to control liquid level fluctuation within ±3mm and constant pulling speed.

[0010] The formula for calculating carbon equivalent is:

[0011] CEN=C+A(C){S i / 24+Mn / 16+Cu / 15+Ni / 20+(Cr+Mo+V+Nb) / 5+5B}

[0012] Furthermore, it is applicable to irregularly shaped billets H730mm×370mm×90mm (BB3).

[0013] Furthermore, the chemical composition of the continuously cast billet comprises the following percentages by mass: C 0.09%–0.12%, Si 0.35%–0.45%, Mn 1.25%–1.35%, P ≤0.025%, S ≤0.015%, Cr 0.30%–0.35%, Cu 0.30%–0.35%, Ni 0.28%–0.33%, V 0.10%–0.12%, N 0.0080%–0.0130%, with the remainder being Fe and impurities, totaling 100% by mass.

[0014] Furthermore, the carbon equivalent (CEN) is ≤0.36%.

[0015] Furthermore, its mechanical properties are as follows: lower yield strength ReL≥440MPa, tensile strength Rm≥570MPa, impact toughness at -40℃≥140J, and elongation≥28%.

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

[0017] This invention effectively controls the generation of transverse cracks at the flange end of high-strength, weather-resistant, peritectic billets, improves the yield of high-strength, weather-resistant, peritectic billets, and controls the transverse crack rate at the flange end of the billet to below 0.5%.

[0018] Its mechanical properties are: lower yield strength ReL≥440MPa, tensile strength Rm≥570MPa, impact toughness at -40℃≥140J, and elongation≥28%. Attached Figure Description

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

[0020] Figure 1 Microscopic morphology of transverse cracks at the end of the flange of an irregularly shaped billet;

[0021] Figure 2 This describes the microstructure of the continuously cast billet of this invention. Detailed Implementation

[0022] A method for controlling transverse cracks at the flange end of a high-strength, weather-resistant, peritectic shaped billet, comprising the following chemical composition by mass percentage: C 0.09%–0.12%, Si 0.35%–0.45%, Mn 1.25%–1.35%, P≤0.025%, S≤0.015%, Cr 0.30%–0.35%, Cu 0.30%–0.35%, Ni 0.28%–0.33%, V 0.10%–0.12%, N 0.0080%–0.0130%, with the remainder being Fe and impurities, totaling 100% by mass, and a carbon equivalent (CEN) ≤0.36%. The finished H-beam exhibits a lower yield strength ReL ≥440MPa, tensile strength Rm ≥560MPa, impact toughness at -40℃ ≥140J, and elongation ≥28%.

[0023] A method for controlling transverse cracks at the flange end of a high-strength, weather-resistant, peritectic billet includes: controlling the generation of low-melting-point substances, adjusting the matching relationship between the secondary cooling water, drawing speed, and superheat, ensuring the temperature of the billet entering the drawing straightener, and improving equipment precision. Specifically:

[0024] To control the generation of low-melting-point substances, Al deoxidation is employed. During the refining process, the residual amount of Al must be strictly controlled, generally between 0.005% and 0.010%. The amount of VN alloy added must also be strictly controlled, generally between 0.7 kg / t, to avoid the generation of brittle AlN. At the same time, the Cu / Ni ratio must be ensured to be ≥ 0.8.

[0025] Adjust the matching relationship between the secondary cooling water, casting speed, and superheat. The secondary cooling water is changed from medium cooling to weak cooling, the casting speed is kept constant at 0.85m / min, and the superheat is controlled at 30℃-35℃, thereby increasing the temperature of the billet at each position when it enters the straightening machine.

[0026] To ensure that the deformation rate of the continuously cast billet does not vary significantly in the straightening zone, the arc of the continuous casting machine and the spatial position of the straightening point rollers must be accurate. The equipment accuracy has been improved from an error of no more than ±0.30mm to an error of no more than ±0.15mm.

[0027] It adopts a 26mm lower slider and automatic stopper rod control to control liquid level fluctuation within ±3mm and constant pulling speed.

[0028] The formula for calculating carbon equivalent is:

[0029] CEN=C+A(C){S i / 24+Mn / 16+Cu / 15+N i / 20+(Cr+Mo+V+Nb) / 5+5B}

[0030] Applicable to irregularly shaped billets H730mm×370mm×90mm (BB3).

[0031] Table 1 Chemical composition of each embodiment

[0032]

[0033] Table 2. Tension speed and superheat of each embodiment

[0034] Example Pulling speed (m / min) Superheat (°C) Example 1 0.85 33 Example 2 0.85 35 Example 3 0.85 31 Example 4 0.85 30

[0035] Table 3. Surface temperature of billet in each embodiment using the straightening machine

[0036]

[0037]

[0038] Table 4 Comparison of cooling water optimization before and after.

[0039] Water flow rate before optimization (L / min) Optimized water flow rate (L / min) Zone 1 233.85 177.08 Outer side of Zone 2 90.45 49.13 Inner side of Zone 2 69.85 33.97 Left side of Zone 2 50.84 17.82 Right side of Zone 2 50.41 18.00 Outer side of the three zones 29.86 30.47 Inner side of the three zones 18.06 18.29 Left side of Zone 3 21.18 11.78 Right side of Zone 3 20.95 11.90 Outer side of the fourth zone 24.87 24.87 Inner side of the fourth zone 12.85 12.88 Left side of Zone 4 6.25 6.34 Right side of Zone 4 6.13 6.45 outer five zones 24.81 24.81 Inner side of Zone 5 13.07 13.07 Left side of Zone 5 5.32 5.32 Right side of Zone 5 5.37 5.37

[0040] Table 5 Mechanical properties of each embodiment

[0041]

[0042] 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 transverse cracks at the flange end of a high-strength, weather-resistant, peritectic shaped billet, characterized in that: Controlling the generation of low-melting-point substances, adjusting the matching relationship between secondary cooling water, drawing speed and superheat, ensuring the temperature of irregular billets entering the drawing straightener, improving equipment accuracy, and adopting automatic control with stopper rods; specifically including: To control the generation of low-melting-point substances, Al deoxidation is employed. During the refining process, the residual amount of Al must be strictly controlled, and should be kept between 0.005% and 0.010%. The amount of VN alloy added must be strictly controlled, at 0.7 kg / t, to avoid the generation of brittle AlN. At the same time, Cu / Ni ≥ 0.8 must be ensured. Adjust the matching relationship between the secondary cooling water, casting speed and superheat. The secondary cooling water is changed from medium cooling to weak cooling. The casting speed is kept constant at 0.85m / min. The superheat is controlled at 30℃-35℃ to increase the temperature of the billet at each position when it enters the straightening machine. To ensure that the deformation rate of the continuously cast billet does not vary significantly in the straightening zone, the arc of the continuous casting machine and the spatial position of the straightening point rollers must be accurate. The equipment accuracy has been improved from an error of no more than ±0.30mm to an error of no more than ±0.15mm. It adopts a 26mm lower slider and automatic stopper rod control to control liquid level fluctuation within ±3mm and constant pulling speed.

2. The method for controlling transverse cracks at the flange end of a high-strength, weather-resistant, peritectic billet according to claim 1, characterized in that: Applicable to irregularly shaped blanks H730mm×370mm×90mm.

3. The method for controlling transverse cracks at the flange end of a high-strength, weather-resistant, peritectic billet according to claim 1, characterized in that: The chemical composition of the continuously cast billet comprises the following percentages by mass: C 0.09%–0.12%, Si 0.35%–0.45%, Mn 1.25%–1.35%, P ≤0.025%, S ≤0.015%, Cr 0.30%–0.35%, Cu 0.30%–0.35%, Ni 0.28%–0.33%, V 0.10%–0.12%, N 0.0080%–0.0130%, with the remainder being Fe and impurities, totaling 100% by mass.

4. The method for controlling transverse cracks at the flange end of a high-strength, weather-resistant, peritectic billet according to claim 3, characterized in that: Carbon equivalent (CEN) ≤ ​​0.36%.

5. The method for controlling transverse cracks at the flange end of a high-strength, weather-resistant, peritectic billet according to claim 3, characterized in that: Its mechanical properties are: lower yield strength ReL≥440MPa, tensile strength Rm≥570MPa, impact toughness at -40℃≥140J, and elongation≥28%.

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