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为发挥低强匹配焊接能改善高强钢的可焊性、有效降低约束力和预热温度的优点,采用J422焊条焊接超声疲劳试样,对高铁转向架用钢SMA490BW低组配十字焊接接头开展常温拉压条件下的超声疲劳试验,并对失效试样进行断口分析,研究低组配接头的疲劳失效机理。试验结果表明:十字焊接接头试样均断于焊趾,疲劳S-N曲线呈连续下降趋势。将十字接头的疲劳性能与板状母材进行对比分析,发现十字接头的疲劳寿命远低于母材。在循环周次为3.11×106时,十字接头试样的疲劳强度仅为母材的67%。试样疲劳断口的扫描电镜(SEM)分析结果显示,裂纹源主要位于焊趾处的熔合区,该区域存在的几何不连续性及焊接缺陷会引起较大应力集中,是导致焊接接头疲劳断裂的主要因素。
In order to improve the weldability of high strength steel and reduce the restraint force and preheating temperature effectively by using low-strength matching welding, ultrasonic welding fatigue test specimen with J422 welding rod is used to weld low-profile high-speed steel bogie SMA490BW with cross welded joints at room temperature Ultrasonic fatigue test under the conditions of tension and compression, and fracture analysis of failure samples to study the fatigue failure mechanism of low assembly fittings. The experimental results show that the cross-sectional welded S-N curves show a continuous downward trend. Cross-joint fatigue performance and plate base metal comparative analysis showed that cross-joint fatigue life is much lower than the base metal. At cycle times of 3.11 x 106, the fatigue strength of the cross-joint specimen was only 67% of the base metal. Scanning electron microscopy (SEM) analysis of the fatigue fracture surface of the specimen shows that the crack source is mainly located in the fusion zone at the weld toe. The geometric discontinuities and welding defects in this area cause greater stress concentration and lead to fatigue fracture of the welded joint major factor.