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我厂生产的BJ121汽车后桥差速器上有20只偏心螺栓,因处于关键部位,是相当重要的零件,其质量好坏直接影响汽车行驶的安全。1986年8月,生产中出现有5%左右的偏心螺栓在组装时即发生断裂,为确保整车质量和行驶安全,厂部决定暂停装车查找原因。为此我们深入现场,在各工序中随机取样,对原材料及该零件进行了全面的检查和分析,发现原材料存在严重冶金缺陷是导致螺拴断裂的根本原因。制作该偏心螺栓的材料是ML35,其工艺流程:用φ12mm棒料二次冷拔成φ9.7mm棒料→下料→冷墩成型→车偏心→滚丝→调质→酸洗→镀锌。
I plant the BJ121 automobile rear axle differential on 20 eccentric bolts, because of the key parts, is a very important part, the quality of its direct impact on vehicle safety. In August 1986, about 5% of the eccentric bolts were broken during assembly. To ensure vehicle quality and driving safety, the factory decided to suspend the loading reason. For this reason, we went to the scene, randomly sampled in each process, conducted a comprehensive inspection and analysis of the raw materials and the parts, and found that the serious metallurgical defects of the raw materials are the root causes of the breakage of the bolts. Production of the eccentric bolt material is ML35, the process: secondary cold drawn φ12mm bar into φ9.7mm bar → blanking → cold pier forming → car eccentric → rolling → quenching → pickling → galvanized.