薄板坯连铸中碳钢角横裂缺陷成因及控制

Analysis and control of transverse corner cracking formation on middle carbon steel in thin slab casting

针对薄板坯连铸中碳钢边角部出现的角横裂纹缺陷,通过典型中碳钢(50Cr V4)缺陷试样的金相分析、热塑性分析和铸坯二冷模拟仿真计算等方法,确定了原工艺条件下典型中碳钢铸坯边角部在铸机弯曲和矫直处的温度为850℃、处于第Ⅲ脆性区(650~945℃)是造成铸坯边角部裂纹的主要原因。结合武钢CSP铸机工艺特点,提出了连铸高拉速4.0~4.2 m/min,二冷前段强冷、后段和边部弱冷以及提高铸机设备精度等控制措施。各项措施实施后,中高碳钢铸坯边角部温度显著提升,热轧板表面横裂纹基本消失,各项性能满足客户要求。

Aimed at transverse corner cracks on middle carbon steel during thin slab casting,the samples with cracks of typical middle-carbon steel（50 Cr V4）was analyzed through the methods of metallographical observation,high temperature plasticity analysis and numerical simulation about second cooling. The cause of transverse corner cracks on the middle-carbon steel in traditional casting process was that the temperature at slab corner was 850 ℃,which was in No.3 Brittleness Temperature Area between 650-945 ℃. According to the features of caster in WISCO CSP plant,several key measures were carried out,including high casting speed（4.0-4.2 m/min）,increasing second cooling water flow rate at the front segment and decreasing second cooling water flow rate at the back segment and edge of slab,and improving the equipment precision. The temperature at slab edge of middle carbon steel increased. Transverse corner cracks of hotrolled sheets were controlled. Each performance of hot-rolled product can meet customers＇ requirements.