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1 问题的提出 在内燃机行业中,连杆螺钉为A级零件,汽缸头螺柱为重要零件。无锡洛社标准件厂为常州柴油机厂、巢湖柴油机厂等生产的连杆螺钉及汽缸头螺柱在装配过程中发生断裂,受到生产厂质量检验部门重视。通过连杆螺钉及汽缸头螺柱断裂分析的程序和磁粉探伤磁痕的分析,达到正确判断断裂原因,从而采用纵向磁粉探伤手段,严格控制产品质量。 2 原材料供应及加工状态 连杆螺钉和汽缸头螺柱为40Cr冷拉圆钢。其尺寸为14mm。在供应的冷拉钢中发现有规律的沿纵向垂直的裂纹(横向裂纹),并存在有规律的冷变形周向压痕,见图1所示,说明零件断裂与表面横向裂纹及有规律的冷变形周向压痕有关。
1 problem raised In the internal combustion engine industry, connecting rod screws for the A-level parts, cylinder head studs as an important part. Wuxi LOSI standard parts factory for the Changzhou Diesel Engine Factory, Chaoyang Diesel Engine Factory and other production of the connecting rod screws and cylinder head stud fracture occurred in the assembly process, the quality inspection departments by the manufacturer attention. Through the procedure of the fracture analysis of connecting rod screw and cylinder head stud and the analysis of the magnetic trace of the magnetic particle inspection, the reason of the fracture can be judged correctly so that the longitudinal magnetic particle inspection method is adopted to strictly control the product quality. 2 raw material supply and processing status Connecting rod screw and cylinder head studs are 40Cr cold rolled round bar. Its size is 14mm. In the supply of cold-drawn steel found in the vertical cracks along the vertical (horizontal cracks), and there is a regular cold deformation circumferential indentation, shown in Figure 1, shows the parts and surface cracks and lateral cracks and regular Cold deformation circumferential indentation.