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| Control of Transverse Corner Cracking of Nb Steel Slab |
| ZHU Guosen1,ZHU Zhiyuan1,WANG Yanfeng1,LIU Jianhui2,BAI Xuejun2 |
| 1. Research Institute of Technology, Shougang Group, Beijing 100041, China; 2. Shouqin Metal Material Co., Ltd., Qinhuangdao 066000, Hebei, China |
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Abstract The optical microscope and SEM were applied to analyze the formation mechanism of transverse corner cracks of Nb microalloyed steel slab. It is found that the cracks occur at relatively low temperature in unbending section due to unbending strain because the corner temperatures of slab in this section is in No.3 brittle zone of Nb steel first, then the corner temperatures of slab is changed greatly due to the casting speed fluctuation, and third the temperature difference between corners at both sides of slab is large due to misfunction of sprayers. Increasing casting speed and decreasing the cooling water flux at slab corners in the unbending section for mild cooling were performed first to control corner temperature above the upper limit in No.3 brittle zone of Nb steel. As a result, the corner temperature of slab was increased apparantly and transverse corner cracking was minimized, but central segregation was got worsely. And then increasing the cooling water flux at corner for intensive cooling was applied to make corner temperature below the lower limit in No.3 brittle zone. Great diminution of both transverse corner cracking and central segregation was achieved finally.
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Received: 01 January 1900
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2006, Vol. 41 
