Cause analysis of cracks in diesel engine crankshaft blank

Abstract

Through comprehensive analysis, crack propagated along the nitride in the form of planar clusters, which caused the metal to layer on the parting surface. There are deep decarburization layer on both sides of the crack of crankshaft blank, and the crack line is soft and thick. The process of quenching and cooling, only when the transformation amount of martensite reaches a certain amount, can cracks be formed. At such a low temperature, even if cracks occur, decarburization and obvious oxidation won’t occur on both sides of the cracks. If there is oxidation decarburization on both sides of the crack, it can be confirmed that the crack has existed before quenching, and the crack belongs to non quenching crack.

Keywords

• crankshaft
• analysis
• defect
• heat treatment
• stress