DP780双相钢不同静态断裂模式下点焊接头的疲劳特性

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中图分类号：TG47

Fatigue characteristics of DP78O steel spot welding joints with different static fracture modes

XIE Lihua， ZHOU Jinnan （Jiangsu Chengxin Inspection，Testing and Certification Co.，Ltd，Wuxi Jiangsu ）

Abstract： Two specimens made of DP78O dual phase steel are produced by resistance spot welding and the quality is evaluated by static tension-shear test and low cycle fatigue test.The fracture characteristics，macrostructure，microstructure，microhardness distribution and fatigue morphology arestudied.The results show that the nugget size and microhardness gradient in heat afcted zone affect the static load-bearing performance and fracture mode.Meanwhile，applied load，microhardnessgradient inheat affcted zone and inclinedangle on faying surface caused by macro deformation have influence on the low cycle fatigue life.Compared with the specimen P which has high static load-bearing capacity，the specimen I has a higher fatigue life and plastic deformation characteristics under the same applied load of 40% of its static load-bearing capacity，which indicates that applied load is the controlling factor in the low cycle fatigue test.

Key words： dual phase steel；resistance spot welding；macroscopic characteristics；microstructure；hardness gradient； fracture mode；fatigue

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