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A Method for Controlling Surface Cracks of Continuous Casting Slabs

A technology for surface cracks and slabs, which is applied in the field of controlling the surface cracks of continuous casting slabs, can solve the problems of increasing the scrap rate of steel plate cracks, difficult longitudinal cracking of slabs, complicated reasons, etc., and achieve the effect of reducing the occurrence rate.

Active Publication Date: 2017-01-18
ANGANG STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0002] Longitudinal cracks on the surface of slabs are common defects in the production process of slab continuous casting machines. The causes of them are intricate. In addition to the peritectic reaction shrinkage itself during the solidification of molten steel, it is also related to the taper of the mold, the performance of mold slag, and the quality of molten steel. Phosphorus, sulfur content, insertion depth of the nozzle, outlet angle of the nozzle, temperature of molten steel and changes in casting speed and other factors are related. The above factors vary in thousands of ways in the actual production process and change in real time, so in the actual production process, it is difficult Effective monitoring and prevention of slab longitudinal cracks will not only affect the pass rate of the surface quality of the slab, but once the slab with surface longitudinal cracks enters the subsequent process, it will directly lead to an increase in the cracked scrap rate of the rolled steel plate

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0015] For the production of peritectic steel, the cross-sectional size of the billet is 250×1800mm, and the superheat of molten steel is 25°C. The specific implementation method is as follows:

[0016] 1. According to the sensitivity of peritectic steel to cracks, choose to control the critical heat flux ≤ 1.30MW / m 2 , the pulling speed is controlled within 1.2m / min.

[0017] 2. Before pouring, check that the cooling water inlet temperature is 25°C, and keep the crystallizer cooling water flow rate at 275m 3 / h. After the pouring starts, raise the casting speed to 0.40m / min at the rate of 0.05m / min for 30s, and then manually raise the speed to 1.00m / min after maintaining for 1min. Speed ​​up to the target pulling speed of 1.2m / min.

[0018] 3. During the casting process, closely monitor the heat flux of the crystallizer, if it is found that the heat flux is greater than the critical heat flux of 1.30MW / m 2 0.10Mw / m at 0.1m / min 2 Decrease the speed so that the heat flux i...

Embodiment 2

[0021] For medium carbon steel, the billet section is 250×2050mm, and the superheat of molten steel is 20°C. The specific implementation method is as follows:

[0022] 1. According to the sensitivity of medium carbon steel to cracks, choose to control the critical heat flux ≤ 1.45MW / m 2 , The pulling speed is controlled within 1.2m / min.

[0023] 2. Before pouring, check that the cooling water inlet temperature is 22°C, and keep the crystallizer cooling water flow rate at 275m 3 / h remains unchanged; after pouring is started, the casting speed is increased to 0.40m / min, and after maintaining for 1min, the manual speed is increased to 0.9m / min, and after the billet reaches a total length of 25 meters, the casting speed is increased to the target casting speed of 1.2 m / min.

[0024] 3. During the casting process, closely monitor the heat flux of the crystallizer, if the heat flux is found to be greater than the critical heat flux of 1.45MW / m 2 0.10MW / m at 0.1m / min 2 Decrease ...

Embodiment 3

[0028] Low-carbon steel, the billet section is 250×1850mm, and the superheat of molten steel is 18°C. The specific implementation method is as follows:

[0029] 1. According to the sensitivity of medium carbon steel to cracks, choose to control the critical heat flux ≤ 1.65MW / m 2 , The pulling speed is controlled within 1.3m / min.

[0030] 2. Check that the cooling water inlet temperature is 18°C ​​before pouring, and increase the cooling water flow rate of the crystallizer from 275m 3 / h reduced to 265m 3 / h; after pouring starts, the casting speed increases to 0.40m / min, and after maintaining for 1 minute, manually increases the speed to 1.0m / min. min; after the second tank is poured, increase the casting speed to the target casting speed of 1.3m / min, and at the same time adjust the cooling water flow back to 275m 3 / h.

[0031] 3. During the casting process, closely monitor the heat flux density of the crystallizer, if it is found that the heat flux density is greater th...

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Abstract

The invention provides a method for controlling a surface crack of a continuous cast slab. The heat flow density of peritectic steel is 1.30 MW / m2; the heat flow density of medium carbon steel is not higher than 1.45 MW / m2; the heat flow density of low carbon steel is not higher than 1.65 MW / m2; before casting, the water inlet temperature of cooling water of a crystallizer is lower than 20 DEG C; the water flow is reduced to 10 m3 / h; and the operation is recovered to a normal state after the casting of a second tank. After casting, the pull speed slowly raises to 0.40 m / min, and is kept for 1 min; the speed of a casting blank with the width higher than1950 mm manually raises to 0.90 m / min; the speed of a casting blank with the width not higher than1950 mm manually raises to 1.00 m / min; and after the pull speed is kept until the whole length of the casting blank reaches 25 m, the target pull speed is reached. In casting, when the heat flow density is greater than the critical heat flow density, the pull speed is lowered; and when the adjustment of the pull speed is ineffective, casting powder is exchanged, or the flow of the cooling water is reduced to 10 m3 / h. The method can effectively reduce the generation rate of the surface crack of the continuous cast slab to reduce the after-rolled crack waste rate of a wide-thick plate continuous cast slab from 0.66% to 0.06%.

Description

technical field [0001] The invention belongs to the technical field of continuous casting technology, and in particular relates to a method for controlling surface cracks of continuous casting slabs. Background technique [0002] Longitudinal cracks on the surface of slabs are common defects in the production process of slab continuous casting machines. The causes of them are intricate. In addition to the peritectic reaction shrinkage itself during the solidification of molten steel, it is also related to the taper of the mold, the performance of mold slag, and the quality of molten steel. Phosphorus, sulfur content, insertion depth of the nozzle, outlet angle of the nozzle, temperature of molten steel and changes in casting speed and other factors are related. The above factors vary in thousands of ways in the actual production process and change in real time, so in the actual production process, it is difficult Effective monitoring and prevention of slab longitudinal crack...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B22D11/18
Inventor 金百刚李超方恩俊李立勋
Owner ANGANG STEEL CO LTD