容器用钢板SA516Gr.70低温冲击性能异常分析及措施优化

Abnormal analysis and optimization measures of low temperature impact property of SA516Gr.70 steel plate for vessel

某钢厂在对SA516Gr.70钢进行低温横向冲击检测时,发现其低温冲击性能不稳定。采用金相显微镜、扫描电镜和能谱分析仪对冲击不合格的断口进行分析,发现造成SA516Gr.70钢低温冲击性能不合格的主要原因是钢板内部存在带状组织,且正火后晶粒度偏大。本文根据分析结果提出了工艺优化改进措施,通过控制连铸坯晶枝偏析,控制820±20℃轧制终轧温度和900℃的正火温度,有效改善钢板内部带状组织并细化晶粒,显著提高SA516Gr.70钢板正火低温冲击性能。

When actualizing the low temperature transverse impact test of SA516Gr.70 steel in a steel plant,it was found that its low temperature impact performance was unstable.Using metallographic microscope,scanning electron microscope and energy spectrum er to analyze the impact unqualified fracture fracture,found that the main reason for the unqualified low temperature impact property of SA516Gr.70 steel is the existence of banded structure in the steel plate,and the grain size is large after normalizing treatment.Therefore,this paper puts forward the process optimization and improvement measures,through controlling the dendrite segregation of continuous casting slab,controlling final rolling temperature of 820±20℃and 900℃normalizing temperature,which the internal banded structure is effectively improved and the grain size is refined,and significantly improved the low temperature impact property of SA516Gr.70 normalizing steel.