Cracking phenomena in automotive wheels: An insight

Abstract

In an automotive, wheels form a very critical and important part with respect to application. Wheels with as less number of flaws as possible are a must to make them fit for application in field. The norms of wheel quality parameters are becoming stringent day by day, thereby increasing the onus on raw material suppliers i.e. – steelmakers to improve the soundness of sheet steel. During their manufacturing (through cold forming, welding etc. of hot rolled sheets) cracking of wheel rim or disc is a major issue encountered at the production line. Surface crack, bore crack and flange crack are common types of failures which lead to rejection. This paper discusses a compilation of metallurgical studies of various such defects and their probable root causes, as conducted by authors. Metallography and advanced characterization techniques have been used in analysing the root cause of the defects. Presence of non-metallic foreign material in steel is one of the major causes leading to surface cracks in wheels. In some cases, it has been found that segregation of elements like Carbon, Phosphorous in steel sheets can lead to poor performance of material during deep drawing or forming at the wheel-maker's end. There are also evidences that bad shearing process at the wheel maker's end can also initiate cracking in wheel.