含硼钢表面裂纹产生的内因及对策研究进展

The latest development of genetic analysis and protection of surfacial crack of boron steel

采用Gleeble-3500热模拟试验机研究了含硼和无硼Q345B连铸板坯的高温力学性能,得到了零强度温度和零塑性温度。并用扫描电镜观察了断口形貌,分析了含硼钢容易产生裂纹的内在原因,结合国内含硼钢冶炼连铸方面的工业技术,提出了含硼钢冶炼连铸方面的一般解决措施。分析结果表明:硼主要从两方面影响连铸坯裂纹:一方面硼在凝固阶段偏析降低了钢的零塑性温度,使钢的第一脆性区间向低温区延伸。另一方面,在连铸二冷阶段BN在晶界析出,增加了晶界脆性,降低了钢的热塑性。国内外在生产含硼钢避免裂纹方面均提出了诸如加钛固氮,降低冷却强度等有效措施。

High temperature mechanical property of Q345B with boron or without boron are investigated by gleeble- 3500. Zero ductility temperature and zero plastic temperature are got. The fracture morphologies of the billet at different temperature were analyzed by SEM. The inner causes of surfacial crack of boron Steel was analyzed. Considering the development of boron steel industrial technology, protection of surfacial crack of boron steel was proposed. The results show that zero ductility temperature decreases after the addition of boron due to the segregation of boron during the stages of freezing. On the other hand, BN precipitates at grain boundary which makes steel more brittle during the secondary cooling of billet. Many effective measures such as adding titanium and reduction billet＇s cooling strength are put forward to reduce surfacial Crack of boron steel.