Corner crack controlling of niobium microalloyed steel billet for construction
BAI Xiao-lu1, ZHANG Xiao-wei1, LI Meng-fei2, ZHANG Li-qiang2
1. Steelmaking Plant,Yonggang Group Co.,Ltd.,Zhangjiagang 215628, Jiangsu, China; 2. School of Metallurgical Engineering, Anhui University of Technology, Ma'anshan 243032, Anhui, China
Abstract:In order to study the cracking of building steel containing Nb during rolling, multiple groups of low magnification samples of slab were detected and analyzed, and the chemical composition, superheat degree of tundish, drawing speed and specific water volume in secondary cooling zone were statistically analyzed combined with the production process data. The results show that the corner crack is the root of the defect, and the temperature range of niobium-containing steel slab with area shrinkage less than 75% is 750-960 ℃. By reducing the specific water volume in the first zone of the second cooling zone, appropriately increasing the specific water volume of the third zone and the fourth zone,adjusting the straightening temperature to avoid the temperature range of area shrinkage less than 75%,and a series of optimization measures to control the contents of sulfur, phosphorus and chromium so as to effective solve the corner crack defects on the slab surface and ensure the product quality of Nb containing construction steel.
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