Influence of Strands' Brittle Zones on Surface Cracks of Hypo-peritectic Steel

In view of large amounts of cracks formed in the hypo-peritectic HSLA steel during solidification,the cracks on the surface of strands were analyzed by optical microscope,SEM and EDS,and the precipitates were studied by thermodynamic calculation. Furthermore,hot ductility was studied by Gleeble-1500. The results showed that steel matrix was deteriorated by inclusions(Fe,Mn,Si,Al)(S,O) in cracks,and transverse cracking sensitivity was increased by Ti-Al-(C,N) inclusions. The longitude cracks tend to appear in the high-temperature brittle zone with a longitude cracking sensitive range of 1 454~1 478℃,and the minimum value of Z was 37.59%; the transverse cracks tend to appear in the low-temperature brittle zone with a longitude cracking sensitive range of 900~750℃,and the minimum value of Z was 45.24%. Precipitating at 896℃,the ferrite led to strain concentration on the grain boundary,resulting in crack formation.