Abstract：SAPH440 automobile structural steel cracked during bearizing and flanging when making a clutch. The cracking samples were analyzedby means of the optical microscope（OM），scanning electron microscope（SEM）， energy disperse spectrometer（EDS），inductively coupled plasma optical emission spectrometer（ICP）and high-frequency infrared carbon-sulfur analyzer. The results showed that the segregation of strip manganese sulfide was the main cause of bearizing and flanging cracking. The crack fracture of the part presented a wood grain shape. There were lots of manganese sulfide inclusions segregated in the matrix at the end of the fracture. The sulfur con-tent in steel exceeded the target. It was recommended to strictly control the sulfur content in steel，improve the so-lidification process，increase the soaking temperature and time to reduce element segregation and prevent segrega-tionofmanganesesulfide.
2019, Vol. 37 
