含铌钢HRB400Nb 180 mm x 180 mm铸坯角部裂纹分析及改进工艺

通过对含铌钢HRB400Nb 180 mm×180 mm连铸坯产生的角部裂纹进行研究分析,结果表明,由于连铸冷却工艺、钢水氮含量和结晶器保护渣工艺控制不当易导致含铌钢铸坯角部沿晶开裂。通过工艺改进钢液氮含量由原（67～98）×10^-6降至（40～55）×10^-6,结晶器角部圆弧半径由8 mm调整为12 mm,结晶器冷却水量由150m³/h降至120m³/h,二冷比水量由1.35 L/kg降至1.1L/kg,二冷分配比由26:48:17:9调整为36:34:19:11,保护渣碱度由0.65调整为0.82、粘度由1.3 pa·s调整为0.69 pa·s、熔点由1260℃调整为1150℃等,有效解决了铸坯表面角部裂纹缺陷,保证了轧材的产品质量。

Analysis on Corner Crack of Nb-Bearing Steel HRB400Nb 180 mm x 180 mm Casting Billet and Process Improvement

The Corner crack of Nb bearing steel HRB400NB 180 mm x 180 mm billet has been studied and analyzed.The results show that improper control of continuous casting cooling process, nitrogen content in molten steel and mold flux can easily lead to corner cracking of Nb bearing billet along grain boundary. With process improvement measures including decreasing the nitrogen content in liquid from original (67 ~ 98) x 10^-6 to (40 ?55) x 10^-6, adjusting the arc radius at the corner of mould from 8 mm to 12 mm, decreasing the cooling water quantity of the mould from 150 m³/h to 120 m³/h, decreasing the water ratio of the secondary cooling from 1. 35 L/kg to 1. I L/kg and adjusting the partitioning ratio of secondary cooling from 26： 48： 17： 9 to 36： 34: 19: 11, adjusting the basicity of the mould flux from 0. 65 to 0. 82 , the viscosity from 1.3 pa ? s to 0. 69 pa ? s, and adjusting the melting point of shielding slag from 1260 °C to 1150 °C. The defects of corner cracks on the surface of billet are effectively solved and the quality of the products is guaranteed.