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Control method for typical middle cracks and center segregation during pipeline steel slab continuous casting

A control method and technology for steel slabs, applied in the field of steelmaking and continuous casting, can solve the problems of inaccurate reduction position, poor improvement of center segregation, and influence on the effect of light reduction, so as to improve accuracy, improve control level, reduce Effect of Small Intermediate Crack Defect Incidence

Active Publication Date: 2016-05-11
SHOUGANG CORPORATION
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Problems solved by technology

First of all, in order to verify the accuracy of the online heat tracking model of the casting machine, a nail-shooting test was carried out. The results showed that there was a certain deviation between the actual solidified slab shell thickness and the model calculation results, which would inevitably lead to inaccurate pressing positions, which would lead to inaccurate improvement of central segregation. Second, the light reduction of different steel types can be calculated according to their solidification shrinkage characteristics, but affected by the deformation resistance of the slab shell, under the same reduction, the reduction efficiency of different steel types of slabs is not the same , so the total reduction should be properly adjusted according to the typical steel type; finally, the key factor affecting the reduction effect is the roll gap control accuracy of the fan section. And reach +0.5 ~ 1.5mm, which seriously affects the effect of light depression

Method used

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  • Control method for typical middle cracks and center segregation during pipeline steel slab continuous casting

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Effect test

Embodiment 1

[0024] Scanning electron microscope energy spectrum analysis was carried out on the cracks in the middle of a typical pipeline steel slab, and there were obvious segregation of Nb, S and other elements in the cracks, resulting in a decrease in thermoplasticity. Under complex stress conditions, the local maximum principal strain exceeds the local critical strain, which in turn leads to the occurrence of the above-mentioned intermediate cracks. Therefore, in order to reduce the stress and strain at the solidification front near the triangular area, the continuous casting process route formulated is shown in Table 2 below. In the down mode, the casting machine presses down the segment into 8 and 9 segments. Tracking the historical data of the displacement sensor of the oil cylinder in the segment within the billet reduction range, the reductions of the two segments in the reduction range are more uniform, and the reduction rates are 1.2mm / m and 0.7mm / m respectively. , eliminatin...

Embodiment 2

[0028] In order to ensure the equipment conditions of the soft reduction process, the off-line maintenance calibration and prior inspection of the sector are strictly required to ensure that the roll gap control accuracy is ±0.2mm. According to the reduction control principle of the casting machine, the length of the theoretical reduction interval is increased to 4.5m, and the solidus temperature is revised to 1450°C. The accuracy of the reduction position is guaranteed, and the maximum reduction rate in a single segment is reduced. The basic roll gap curve of the casting machine is: the central liquid phase area is 0.39, the central two-phase area is 0.21, and the central solidification area is 0.11; The curves in the table below are three-stage reductions, and the reduction rates are 0.7mm / m, 1.0mm / m, and 0.25mm / m. Track the internal quality of the slab, center segregation, and the proportion of Class C ≤ 1.0 has been greatly increased from 45% to 87%.

[0029] Table 3 cont...

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Abstract

The invention belongs to the technical field of steelmaking continuous casting, and relates to a control method for typical middle cracks and center segregation during pipeline steel slab continuous casting. The control method comprises the steps that a roll gap of a casting machine is subjected to offline calibration and online detection, and it is guaranteed that precision is + / -0.2 mm; steel grade grouping is carried out, and matching of steel grades and thermophysical parameters is enhanced; the degree of superheat is strictly controlled, the proportion of equiaxed grains is increased, and developed columnar grains are avoided; a pulling rate and a secondary cooling process are adjusted, and basic roll gap control in the casting slab solidification process is optimized; and the soft press quantity is optimized, two or three segments of press are selected to the greatest extent according to the continuous casting process, and a large press quantity difference is avoided in press distribution between different sector segments. The control method has the beneficial effects that the internal quality of the casting slab is improved, and the product competitiveness is enhanced.

Description

technical field [0001] The invention belongs to the technical field of steelmaking and continuous casting, in particular to a control method for typical intermediate cracks and central segregation of pipeline steel slab continuous casting. It can effectively reduce the occurrence rate of intermediate crack defects near a triangular area, significantly improve the control level of central segregation, and improve the internal quality of the slab. Background technique [0002] Pipeline steel is mainly used to manufacture pipelines for transporting oil and natural gas. The working environment is usually harsh, the pressure on the pipeline is high, the transportation line is long, and maintenance is difficult. Therefore, the quality requirements for pipeline steel are very strict. Its performance requirements mainly include: high strength, high toughness, excellent resistance to hydrogen-induced cracking (HIC) and stress corrosion cracking (SCC) and good welding performance. Cr...

Claims

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Application Information

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IPC IPC(8): B22D11/16B22D11/06B22D11/22
CPCB22D11/001B22D11/06B22D11/16B22D11/225
Inventor 刘珂刘国梁曾智牛涛孙齐松陈斌王畅倪有金张颖华李中华马威
Owner SHOUGANG CORPORATION
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