Patent ID: 6328826
Filing Date: 2001-12-11
Classification: C21D

Abstract:
A method of fabricating transformation induced plasticity steel in the form of thin strip, comprising:casting a strip from 1.5 to 10 mm thick directly from liquid steel comprising (in weight percent) C% from 0.05 to 0.25, (Mn+Cu+Ni) % from 0.5 to 3, (Si+Al) % from 0.1 to 4, (P+Sn+As+Sb) % not greater than 0.1, (Ti+Nb+V+Zr+rare earths) % less than impurities;hot-rolling said strip on-line in one or more passes at a temperature higher than the Ar.sub.3 temperature of said steel and with a reduction ratio from 25 to 70%;first forced cooling of said strip at a cooling rate from 5 to 100.degree. C./s;holding the strip at a temperature of from 550 to 400.degree. C. for the time needed for bainitic transformation to occur therein with a residual austenite content greater than 5%, whilst preventing the formation of perlite;interrupting the transformation by second forced cooling of said strip to a temperature below 400.degree. C.; andcoiling said strip at a temperature below 350.degree. C.