23MnNiMoCr54钢矿用圆环链的疲劳失效分析

Fatigue failure analysis of round-link chain for mining produced by 23MnNiMoCr54 steel

矿山链环疲劳断裂是影响链环使用寿命最主要的因素,通过对链环断口附近、断口对称未断裂的肩部和链环直臂处显微组织观察、夹杂物分析、断口形貌的分析以及扫描电镜观察,分析了矿山圆环链疲劳失效的原因。结果表明：链环直臂处组织为回火屈氏体,链环断裂与未断裂处肩部为回火索氏体组织,显微组织满足链环的服役要求,热处理显微组织不是导致疲劳失效的主要原因。断口裂纹源位置分布着多颗尺寸10~50μm的氧化物夹杂颗粒,夹杂物周围存在着二次裂纹,大量的脆性夹杂物破坏了钢基体的连续性,往往成为裂纹的起点;随着裂纹的扩展,又会在夹杂物附近形成多个二次裂纹,进而加速疲劳失效。对满足链环疲劳性能用钢中夹杂物进行分析表明,夹杂物尺寸减小与数量的减少,降低了对钢的疲劳性能的不利影响,从而大幅度提高了钢的疲劳循环次数。

Mining chain fatigue fracture is the most important factor that affects the service life of the chain. According to the observation of the optical microstructure,the analysis of inclusions and the fracture morphology and the scanning electron microscope observation of the symmetric shoulder without fracture,the straight arm of the chain and near the fracture surface of the chain,the causes of fatigue failure of the mine round-chain has been analyzed. The results show that the microstructure of the straight arm of the link was tempered troostite. The shoulder of the link and the shoulder of the un-ruptured surface are tempered sorbite. Such microstructures meet well the service requirements of the link,so that the microstructure resulted from the heat treatment is not the main cause of fatigue failure. Many oxide inclusions with sizes of 10-50 μm are found in the source of fracture cracks,and there are secondary cracks around these inclusions. A large number of brittle inclusions destroy the continuity of the steel matrix and often become the initiation of cracks. With the expansion of cracks,many secondary cracks form in the vicinity of the inclusions,which accelerate the fatigue failure. The analysis of the inclusions in the steel that satisfy the fatigue performance of the link shows that the reduction of the size and the number of inclusions can reduce the harmful effect on the fatigue performance of the steel,thereby greatly increasing the number of fatigue cycles of the steel.