大壁厚Q420高强结构钢焊接裂纹失效分析

为了提高大壁厚高强度建筑结构钢的焊接效率和实际工况下的焊接质量，对Q420高强结构钢进行了焊接工艺研究，通过化学分析、宏观形貌分析、显微组织分析、显微硬度测试、断口分析和力学性能测试等试验方法，对焊接接头出现的沿钢板厚度方向的贯穿裂纹进行了失效分析。分析结果表明，裂纹产生原因是受到超过钢板厚度方向屈服强度载荷作用，并在巨大的载荷作用下启裂和扩展。建议Q420钢板厚度方向不能代替纵向承载，应避免在壁厚两侧焊接和在壁厚方向承载主要拉伸应力。

Failure Analysis of Welding Cracks for Q420 High-strength Structural Steel with Large Wall Thickness

In order to improve the welding efficiency and the welding quality of high strength structural steel with large wall thickness under the actual working conditions, the welding ability of Q420 high strength structural steel was studied. Through chemical analysis, macro morphology analysis, microstructure analysis, micro hardness test, fracture analysis and mechanical properties test, the failure analysis of penetrating cracks along the thickness direction of steel plate in welded joints was carried out. The analysis results show that the crack is caused by the load of yield strength beyond the thickness of steel plate, and initiates and propagates under the huge load. It is suggested that the thickness direction of Q420 steel plate can not replace the longitudinal load and the main tensile stress, on both sides of the wall thickness and in the wall thickness direction, should be avoided.