Patent ID: 6568462
Filing Date: 2003-05-27
Classification: C21D

Abstract:
Process for the production of austenitic stainless steel strips, comprisingcasting in a mould with twin counterrotating rolls of a continuous casting apparatus, a strip having thickness between 1 to 5 mm, and consisting of the following composition in percent by weight: Cr 17-20; Ni 6-11; C<0.04; N<0.04; S<0.01; Mn<1.5; Si<1.0; Mo 0-3; Al<0.03; and wherein Ti, Nb, Ta are provided in the strip so that: Ti+0.5(Nb+Ta)>6C-3S when Ti>6S; and Nb+Ta>12C when Ti<6S; wherein, in either case, Nb+Ti+Ta<1.0%; the remaining part being Fe and impurities, and having a dendritic solidification microstructure with an average grain size, measured on a cross-section parallel to the strip surface, between 30 and 80 &mgr;m, and having a &dgr;-ferrite volume percentage between 4 and 10%, calculated by the formula: &dgr;-ferrite=(Creq/Nieqâˆ’0.728)Ã—500/3 wherein: Creq/Nieq=[Cr+Mo+1.5Si+0.5Nb+0.25Ta+2.5(Al+Ti)+18]/[Ni+30(C+N)+0.5Mn+36]; wherein the element symbols represent their weight percentage in the whole composition; and cooling the resultant stainless steel strip as cast at a cooling rate of 20-50Â° C./s.