30CrMnSiA钢制三向接头开裂分析

Analysis on Fracture of 30CrMnSiA Three Dimensional Joints

对2件先后在表面沟槽根部发生开裂的30CrMnSiA钢制三向接头的断口进行宏微观观察,检测其金相组织、硬度和化学成分,测量源区位置的壁厚和倒角值。结果表明:2件三向接头均起源于沟槽根部的外表面,断口特征基本一致,均为疲劳特征,其金相组织、硬度和化学成分未见异常,但沟槽根部加工质量较差,壁厚较低,且圆角很小。综合分析认为,由于三向接头沟槽根部位置存在较大的应力集中,且该位置壁厚较薄,名义应力较大,在振动应力作用下发生了疲劳开裂,并由此提出了预防和改进建议。

Macro and micro observation,metallurgical structure examination,hardness testing,chemical analysis and depth testing were carried out on two three-dimensional joints fracturing at the root of surface groove.The results show that the cracks of the two joints initiated from the root of the groove and typical fatigue characteristics could be found at the fracture surface. Their metallurgical structure,hardness and chemical composition are all in the range of standard,but machining quality is bad and wall thickness and round angle is low at the root of the groove.So it can be concluded that nominal stress at the root of the groove of the joints is higher because of stress concentration and lower wall thickness,and fatigue fracture happened under working vibration stress.Based on the analysis result,some measures were put forward.