针对85mm厚海上风电用S355G10+N钢板心部冲击功低且离散性大的问题,结合夹杂物生成理论计算,采用金相检验、扫描电镜及能谱分析研究了钢板不同厚度处的微观组织。结果表明,钢板的组织主要为粒状贝氏体、少量铁素体和少量珠光体。钢板表面与1/4厚度处组织均匀,而在钢板心部发现了严重偏析和板条贝氏体。冲击断口形貌表明,由于中心偏析导致生成的MnS和(Nb,Ti)C夹杂物为断裂源,其附近断裂方式为沿晶断裂。钢板中心偏析处的板条贝氏体加剧了裂纹的扩展,夹杂物与板条贝氏体的综合作用显著降低了钢板心部的冲击韧性。

In order to solve the problems of low impact energy and high dispersion in the core of S355G10+N steel plate used for offshore wind power with 85mm thickness, the microstructure of the steel plate with different thickness was studied by metallographic examination, scanning electron microscope and energy spectrum analysis combined with theoretical calculation of inclusion formation.The results show that the microstructure of the steel plate is mainly granular bainite, a little ferrite and a little pearlite.The surface of the plate is homogeneous with the thickness of 1/4, but severe segregation and lath bainite are found in the heart of the plate.The impact fracture morphology shows that the MnS and (Nb,Ti)C inclusions generated by center segregation are fracture sources, and the fracture mode near them is intergranular fracture. The lath bainite in the center segregation of steel plate increases the crack propagation, and the combined action of inclusions and lath bainite significantly reduces the impact toughness of steel plate core.