关键词: 不锈钢点焊, 疲劳性能, 疲劳开裂, 腐蚀介质, 应力比, 温度

Abstract: Joints of resistance spot welding on stainless steel body frame was used as research objects to find out the influences of temperature (-40 ℃, room temperature, 70 ℃), stress ratio(0.1，0.5) and 3.5% NaCl environmental medium on joint fatigue lifes. The electron back-scattered diffraction(EBSD) technology, scanning electron microscopy(SEM), instrumented ball indentation system(IBIS) and tensile-shear experiment were used to analyze the grain orientation, residual stress distribution, appearance of fatigue fractures and the mechanics properties. Results show that the fatigue property is better due to the increasing of material strength under low temperature conditions. And the high-cycle fatigue property is better due to the improvement of plastic property under 70 ℃. The fatigue property of stress ratio of 0.1 is better than that of 0.5. Corrosion medium and tensile stress may accelerate the strress corrosion, cracking and rapid dissolution of anode regions of crack top ends, accelerate the initiation and extension of the cracks，and may significantly reduce fatigue life of spot welding joints. The fatigue cracks are nucleated on the stress concentration interfaces, the cracks grow up along the softening zones and extend to the plate surfaces until fracture failure.

Key words: stainless steel spot welding, fatigue property, fatigue cracking, corrosion medium, stress ratio, temperature