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针对800 MPa级低碳贝氏体高强钢板拉伸测试时出现断口分层问题,使用扫描电镜对断口分层面进行了观察,并结合力学性能测试结果分析。研究表明,钢板中Ti和Nb偏析,大面积聚合析出,严重破坏了钢基体沿厚度方向的整体性,造成厚度方向塑性较差,成为拉伸断口出现分层的先天性因素,通过修改成分设计、降低钢水浇铸过热度和拉速以及提高铸坯出钢温度,改善中心偏析,再配合560～580℃回火,可有效改善钢板拉伸断口形貌,保证足够的强度和断后伸长率。
For the 800 MPa low carbon bainitic high tensile steel plate, the fracture stratification problem occurred. The fracture surface was observed by scanning electron microscopy, and the mechanical performance test results were analyzed. The results show that segregation of Ti and Nb in the steel and segregation of large area in the steel plate seriously degrade the integrity of the steel substrate in the thickness direction and result in poor plasticity in the thickness direction and become a congenital factor in the delamination of the tensile fracture. , Reduce the superheat and speed of molten steel casting and increase the slab tapping temperature, improve the center segregation, and then with 560 ~ 580 ℃ tempering, which can effectively improve the tensile fracture morphology of steel plate, to ensure adequate strength and elongation after fracture.