φ710mm走轮开裂原因分析

CRACKING ANALYSIS OF THE φ710mm WHEEL

710mm走轮在未经使用情况下发生严重开裂。为确定走轮开裂原因,进行了工艺调查和解剖分析。通过SEM观察,可知主断口微观形貌符合白点断口特征。低倍检验轮毂部位有白点裂纹。低倍试样的断口面有白点亮斑,亮斑宏、微观形貌符合白点断口特征,断口表面附近有呈穿晶分布的锯齿形裂纹,裂纹内及其周围未见明显的非金属夹杂。踏面硬度高达390HBS,超过工艺规定的上限360HBS。由此认为,走轮的开裂是由白点引起的,而白点裂纹的形成与走轮材料的含氢量、热处理工艺欠妥导致较大的内应力等因素有关。

 710mm wheel cracked seriously in unused condition. In order to find out the reason of the wheel cracking, technique investigation and dissection analysis have been carried out. By SEM the micro appearance of main fracture conformed to characteristics of flake fracture. There are some cracks in the wheel boss by macro examination. There are some light spots on the fracture of the broken sample. The macro and micro appearance of light spot conformed to characteristics of flake fracture. Conclusions can be drawn from metallographic examination as follows: there are some zigzag cracks which located transgranularly near the fracture. What′s more, there are no apparent inclusions within and near the cracks. The hardness of tread was up to 390HBS, which exceeded the upper limited value 360HBS specified by technical standard. So it can be concluded that flake led to the wheel cracking and the formation of cracks were related to the content of hydrogen in the material and residual stress which was caused by improper heat treatment.