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测试了不同成分和工艺生产的800 MPa级低合金高强钢板的力学性能,借助光学金相显微镜、扫描电镜及透射电镜对其组织进行了分析。结果表明,800 MPa级低碳非调质钢,具有较低的淬硬倾向,可实现免预热焊接,该钢轧后冷速>12℃/s时,形成以针状铁素体和板条贝氏体为主的微观组织,钢板冲击韧性大幅度提高,且裂纹敏感性值更低,焊接后也表现出更强的抗裂性能。而800 MPa级中碳调质钢具有一定淬硬倾向,焊接时必须预热否则接头部位易出现裂纹,母材组织主要为回火马氏体,焊接接头组织为少量回火马氏体、大量未溶解碳化物及一定量准多边形铁素体,对塑性变形抗力很小。
The mechanical properties of 800 MPa low alloyed high strength steel with different compositions and processes were tested. The microstructures were analyzed by optical microscope, scanning electron microscope and transmission electron microscope. The results show that 800 MPa low-carbon non-quenched and tempered steel has a lower tendency to harden and can achieve preheat-free welding. When the cooling speed is> 12 ℃ / s after rolling, the acicular ferrite and the plate Bainite-based microstructure, the impact toughness of steel increased significantly, and the lower the value of the crack sensitivity after welding also showed a stronger crack resistance. The 800 MPa grade carbon quenched and tempered steel with a certain tendency to harden when welding must be preheated or joints prone to cracks, the parent material is mainly tempered martensite, welded joints a small amount of tempered martensite, a large number Undissolved carbides and a certain amount of quasi-polygonal ferrite, resistance to plastic deformation is small.