Analysis on Cracking Reason of Flange Sleeve Parts after Quenching and Tempering

The circumferential cracking was found on the edge of flange sleeve parts for oil pipeline after the hot forging,quenching and tempering.Through chemical composition analysis and metallographic examination,the cracking reason of flange sleeve parts was analyzed.The results showed that the intergranular oxidation was formed in flange sleeve parts,which was overheating or overburning in the forging process,because the heating temperature was too high and the heating time was too long.The intergranular binding capacity decreased significantly,the microstructure was embrittled,led to hot forging cracking in the parts.