The shape, type, content, and dimension of nonmetallic inclusions in SUS304 strip produced by twin-roll strip casting were studied using scanning electron microscopy (SEM). The results show that the inclusions are mainly spherical Al2O3 and com-plex oxides composed of MnO, Al2O3, and SiO2. The percentage of fine oxides smaller than 3 μm reaches up to 51.8%. The theoreti-cal calculations show that fine oxides have precipitated during solidification. Therefore, it is concluded that during twin-roll strip casting, because of high cooling rate, the size of inclusions precipitated during solidification decreases, and the amount increases.
Mathematical model of solute [C] distribution in twin-roll strip casting process has been setup successfully with Calcosoft for the first time. Simulation result shows that in the center of the molten steel pool between the two rolls there is a vortex flow, which is a solute enriched area. But the highest solute concentration position is at the solidification front of the columnar grain zone near the cooling roll surface. Another solute enriched position is in the back flow above the nip point. Combined with the formation mechanism of microstructure in final as cast strip, analysis shows that solute enriched area is in the transitional area between columnar and equiaxed grain zone.
Yongsheng WANGChenxi JIJiongming ZHANGXinhua WANGWanjun WANG
