Abstract: In order to improve the qualification rate of postweld detection of wind power steel plates, the unqualified and qualified steel plates of heat-affected zone after welding of 18 mm thick wind power steel were taken as the research object. Metallographic microscopes and scanning electron microscopes were used to analyze the metallographic structure and inclusions. The difference between qualified and unqualified parts of flaw detection was investigated, and the cause of unqualified of flaw detection in heat affected zone after welding was studied. The results showed that, the presence of large size aluminum oxide or calcium aluminate inclusions in the steel plate was the cause of failure in post-weld heat affected zone. Combined with actual production, the whole process was controlled from the beginning of tapping process to continuous casting process，and the proportion of type B inclusions below class 1.5 in the steel plate from 85 % to more than 98 %.The quality objection of flaw detection unqualified in the heat affected zone after welding was eliminated.

Key words: wind power steel, heat affected zone, flaw detection defect, inclusion, process optimization