精冲钢连铸坯角部横裂纹产生原因及控制措施

为了研究精冲钢角部横裂纹形成原因并制定相应控制措施,通过数值模拟计算了二冷区连铸坯温度场分布,在此基础上采用Gleeble 3500热模拟机测定了试验钢种在连铸条件下的断面收缩率。使用金相显微镜、扫描电镜对角部横裂纹附近成分、微观组织以及钢中夹杂物进行观察分析。结果表明,连铸坯角部横裂纹形成是由于钢中大尺寸夹杂形成裂纹源,弯曲过程中连铸坯角部表面温度处于第Ⅲ脆性区710~765 ℃,裂纹进一步扩展形成角部横裂纹。针对裂纹产生原因提出延长软吹时间、控制过程温降、调整二冷水量等措施,有效降低连铸坯角部横裂纹产生概率。

Causes and control measures of corner transverse cracks in fine blanking steel continuous casting billet

In order to study the causes of corner transverse cracks in fine blanking steel and formulate corresponding control measures, the temperature field distribution of continuous casting billet in secondary cooling zone was calculated by numerical simulation. On this basis, the section shrinkage of experimental steel under continuous casting conditions was measured by Gleeble 3500 thermal simulator. The composition, microstructure and inclusions in steel near the corner transverse crack were observed and analyzed by metallographic microscope and scanning electron microscope. The results show that the formation of corner transverse cracks is due to the formation of large size inclusions in the steel. During the bending process, the surface temperature of the corner of the continuous casting billet is at 710-765 ℃ in the brittle zone Ⅲ, and the crack propagates further to form corner transverse cracks. Some measures such as prolonging soft blowing time, controlling temperature drop during the process and adjusting the amount of secondary cooling water were put forward to effectively reduce the probability of corner transverse crack of continuous casting billet.