Fracture Analysis of Case Hardening in Kingpins Parts

Abstract

Kingpin parts are the critical product for heavy vehicles and are generally made of 20MnCr5 steel. A kingpin is a heavy metal cylindrical pin that is located underneath the front end of the trailer. The kingpin is the mechanism on the trailer that locks it to a road tractor. The parts in this study have undergone to case hardening heat treatment after the rough machining operation. During the operation in the assembly line, cracks have been shown on the parts surface. In this study, kingpin parts are examined with Scanning Electron Microscopy (SEM) analysis, hardness and %C potential analysis in order to determine the potential causes of crack formations. It is shown that, heat treatment of the parts is not homogeneously distributed and therefore fractures occur. The exact outcome of the fracture could not be determined. Under the scanning electron microscope, it becomes clear that it is a crack. There are no signs of hydrogen embrittlement. With the present structure, it is to be expected that even a low dynamic load can lead to breakage. As a result, investigations suggest that the parts have exposed to incorrect heat treatment parameters.

Keywords

• Kingpin
• Case Hardening,
• Scanning Electron Microscopy (SEM),
• Crack formation
• 20MnCr5 steel

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