"Improvement of Transverse Cracks of NB-Alloyed Steel Slabs "

oleh "Hajime Suto, Kazuki Sumida, Jin Yoshida "

Penerbit - "Kakogawa Works, Iron & Steel Business and Kobe Steel, LTD, JAPAN "

Kategori - Kejuruteraan & IT

"Transverse cracks on the continuous casting slab surface lead to surface defects of steel sheet and plate. Such cracks are often formed near the slab corner during unbending of continuous cast strands. The oscillation marks and other surface depressions promote the cracks. And the cracks occur when the temperature of slab surface in the unbending zone is within the low ductility temperature range. The hot ductility of steel is affected by the compositions. Nb expands the temperature range of low ductility caused by the precipitation of niobium carbides and nitrides at the austenite grain boundaries. In this work, the transverse cracks of Nb-alloyed steel are inhibited by controlling the secondary cooling. The corner of the slab had a temperature lower than the low ductility temperature range. The temperature of the center (in terms of width) of the slab was higher than the low ductility temperature range. On the other hand, the surface temperature on the wide face of the slab reached the low ductility temperature. The area of low ductility temperature was kept to the depthless area of slab surface where the oscillation mark was shallow. As a result, the transverse cracks of Nb-alloyed steel slab decreased in No.4CC-1str machine at Kakogawa works. "

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