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采用高倍金相检验、扫描电镜及能谱分析等方法对120mm Q390GJC-Z35特厚板的z向性能不合缺陷进行了研究。结果表明:z向性能不合主要是由于钢锭存在着较严重的中心偏析,在不合试样断口处存在着较多的块状(Nb、Ti)C聚集,块状的(Nb、Ti)C成为裂纹源。此外,偏析处还存在贝氏体等硬相组织,更加剧了断裂扩展,导致z向性能不合。通过优化成分设计,加强精炼过程控制,改进模铸浇注工艺,制定合理热处理工艺等相关措施,取得了良好的效果。
High-power metallographic examination, scanning electron microscopy and energy-dispersive spectroscopy were used to study the defect of the z-shaped performance of the 120mm Q390GJC-Z35 extra thick slab. The results show that the main factors of z-direction failure are the more serious segregation of the center of the ingot and the accumulation of massive (Nb, Ti) C in the fracture surface of the unqualified specimen. The massive (Nb, Ti) C becomes Crack source. In addition, segregation also exists bainite and other hard phase structure, more exacerbated the fracture expansion, resulting in z-performance incompatibility. By optimizing the composition design, strengthening the control of the refining process, improving the casting process, formulating reasonable heat treatment process and other related measures, good results have been achieved.