Q235B热轧钢带冷弯开裂原因分析及措施

Reasons Analysis of the Cold-bending Cracking and the Countermeasures for Q235B Hot-rolled Steel Strip

对钢带发生的冷弯开裂试样进行了大量理化检测、组织分析。结果表明:材料冷弯开裂的主要原因是由于钢水非金属夹杂物含量偏高,次要原因是铸坯在热轧生产加热过程中表皮氧化严重,皮下气泡外露,轧制拉长使钢材表面产生裂纹源。当然,次要原因的根源还在于钢水气体含量高导致铸坯存在皮下气泡。而在这些非金属夹杂物中,又以C类(硅酸盐)和D类(环状氧化物)夹杂为最多和等级最高。基于上述原因,对Q235B板坯成分和生产工艺进行了认真研究和改进,在钢水不经LF炉精炼的条件下解决了钢带冷弯开裂的问题,从而大幅降低了板带生产成本。

The considerable physical and chemical examination and structure analysis were carried on for the cold-bending cracking specimen of Q235B hot rolled strip. The results show that, the main reasons of the material cold-bending cracking is that due to the content of nonmetallic inclusions in molten steel is more. Minor reason of coldbending cracking is that due to the steel billet epidermis oxidized seriously, subcutaneous bubble exposed, rolling elongation in the hot-rolled continuous production process. Of course, more gas content in molten steel causes that steel billets come into being the subcutaneous bubble is also important reason. In these nonmetallic inclusions, C class （silicate） and D category （annular oxides） inclusion are the most and highest grade. Based on the abovementioned reason, carried on researching and improving to the components and manufacturing technique of Q235B slab, solved the problems of strip cold-bending cracking under conditions of the molten steel without a LF refining. As a result, reduced obviously the manufacturing costs of the strip.