热轧卷板边部直裂纹的成因分析及控制

CAUSES ANALYSIS FOR STRAIGHT CRACK AT EDGE OF HOT-ROLLING COILED SHEET AND ITS CONTROL

热轧卷板上出现的不同于常规发纹的短直形边部直裂纹缺陷对产品的影响较大。轧钢环节的中间坯显示铸坯切角部位出现规则性斜向裂纹,通过使用电镜、金相、酸洗等检测方法对卷板、中间坯、连铸坯进行检测,分析裂纹形成机理,认为:铸坯三角区的多种缺陷在铸坯大切角量情况下被轧制放大是造成卷板边部直裂纹缺陷的主要原因。通过调整成分、优化保护渣、调整结晶器水量、优化二冷边部水量、调整设备精度等措施改善了铸坯三角区质量、优化了切边量,最终消除了热轧卷板边部直裂纹的产生。

The short and straight edge crack on hot-rolling coil sheet,which differs from normal hair veins,affects seriously the quality of sheet.And there are regular slanting cracks found at cutting corner of casting billet of medium billet in steel rolling stage.With electron microscope,metallographic and pickling,the coil sheet,medium billet and casting billet are examined and the cracks forming mechanism is analyzed.It is considered that the main reason for the short and straight edge cracks is that the various defects at three-angle region of casting billet are expanded through rolling under big corner-cutting quantity.The above mentioned straight cracks are eliminated with improving quality of three-angle region of casting billet and optimizing corner cutting quality by means of measures： adjusting composition,optimizing casting powder,adjusting water quantity of mold,optimizing second cooling water quantity at edge and adjusting equipments precision.