为找出500 MPa钢板探伤不合格原因,通过金相显微镜、扫描电镜、能谱分析和电子探针波谱仪对500 MPa钢板探伤缺陷组织、成分进行了分析.结果表明:钢板探伤不合格的原因是由钢板中心偏析带上的裂纹导致,MnS、Nb/Ti夹杂物是造成裂纹的主要原因.通过提高钢水洁净度,降低钢水过热度,优化二次冷却技术,采用电磁搅拌和轻压下提高铸坯内部质量,同时适当优化铸坯加热工艺以及轧后堆垛缓冷方式,可以防止裂纹的产生.
In order to find the causes of nonconformity in ultrasonic flaw detection of 500 MPa heavy steel plate,the structure and component of the defects found in ultrasonic flaw detection were investigated by optical microscope,scan electron microscope,EDS analysis and electron probe spectrometer.The results showed that the centerline segregation crack originating from MnS,Nb/Ti inclusions was the cause of nonconformity in ultrasonic flaw detection.By improving the internal quality of the slab with improving steel cleanliness,decreasing superheating temperature of liquid steel,optimizing second cooling technology,and using technologies of electromagnetic stirring and soft reduction,optimizing slab heat process,and stacking slow cooling after rolling,the crack can be prevented.
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