Cause Analysis on Abnormal Phenomenon of 34Cr2Ni2Mo Steel Flange Forks

Multi white banded abnormal areas were found in the bearing hole close to the flange side of a batch of 34Cr2Ni2Mo steel flange forks in machining process after quenching and tempering, and the causes were analyzed by means of macro-etching test, chemical composition analysis, hardness test and metallographic examination. The results show in the casting process of 34Cr2Ni2Mo steel flange forks, due to fixing instability, the 20 steel internal chill frame collapsed and stored in the casting under the scouring action of molten steel. The 20 steel was exposed in the bearing hole close to the flange side in the following machining process, so white banded abnormal areas different from the matrix produced.