DP980钢及DP980钢激光焊接接头的高周疲劳性能

摘要：为了研究DP980钢的高周疲劳性能，采用疲劳试验机对DP980钢和DP980钢激光焊接接头进行高周疲劳试验，得到Basquin方程，并利用光学金相显微镜和扫描电镜进行组织和断口分析。结果表明：DP980钢激光焊接接头的焊缝根部和顶部出现形状凹陷，焊接接头的质量为中等。DP980钢疲劳极限为341MPa，DP980钢激光焊接接头的疲劳极限为148MPa，激光焊接接头的疲劳极限较母材的疲劳极限降低约50%。对于DP980钢而言，铁素体/马氏体晶界是裂纹萌生的主要位置，疲劳断口为准解理断口。对于DP980钢激光焊接接头而言，疲劳裂纹源位于焊缝凹陷处，而非热影响区及母材，疲劳断口为解理断口。DP980钢和DP980钢激光焊接接头的疲劳裂纹扩展区均有明显的疲劳条带，并伴随有二次裂纹。

High cycle fatigue behavior of DP980 steel and DP980 steel laser welded joints

Abstract： For the study of the DP980 steel high cycle fatigue property, high fatigue tests of DP980 steel and DP980 steel laser welded joints were carried out with fatigue testing machine, the Basquin equation was concluded. Microstructures and fractures were analyzed by optical microscope and scanning electron microscope. The results show that DP980 steel laser welding joints have the weld concavity at the welding root and top, the quality of welded joints is medium. The fatigue limit of DP980 steel is 341MPa, the fatigue limit of DP980 steel laser welded joint is 148MPa, the fatigue limit decreases by 50% compared with the fatigue limit of the base metal. For DP980 steel, the crystal boundary of the ferrite/martensite is the main location of micro cracks initiation, the fatigue fracture of DP980 steel is the quasi cleavage fracture. For DP980 steel laser welding joints, the fatigue cracks initiation is located in the weld concavity, not in the heat affected zone, the fatigue fracture is cleavage fracture. DP980 steel and DP980 steel laser welding joints crack propagation is characterized by the obviously fatigue striations coupled with secondary cracks.