铌微合金化建筑用钢连铸坯角部裂纹控制

为了研究含铌建筑用钢轧制产生开裂的问题,对多组铸坯低倍样进行检测分析,并结合生产过程数据对化学成分、中间包过热度、拉速及二冷各区比水量进行了统计分析。结果表明,角部裂纹是缺陷根源,含铌钢铸坯的断面收缩率低于75%的温度范围为750～960 ℃。通过降低二冷一区的比水量,适当提高三区、四区的比水量、调整矫直温度使其避开断面收缩率小于75%的温度区间和控制硫、磷、铬含量等一系列优化措施,有效解决铸坯表面的角部裂纹缺陷,保证了含铌建筑用钢的产品质量。

Corner crack controlling of niobium microalloyed steel billet for construction

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.