Abstract: The radial cracks were found on the inner hole steps of the bearing block. The cracking reason of the bearing chock was confirmed by site investigation, metallographic examination, chemical composition analysis and macrography examination. The results show that the cracks of bearing chock is caused by quenching, which results from workpiece diameter falling into the critical size of quenching of the step, right angle transition and some chemical elements content close to the upper limit. The problem is solved by changing the right angle to round angle, and fine tuning the quenching temperature according to the chemical composition.

Key words: bearing chock, quenching crack, preventive measures