Patent ID: 6818073
Filing Date: 2004-11-16
Classification: B22D,C21D,C22C

Abstract:
A low carbon steel produced by a process comprising the steps of:(a) continuously casting molten low carbon steel into a strip of no more than 5 mm thickness with austenite grains that are coarse grains of 100-300 micron width; and (b) providing desired mechanical properties in the cast strip without changing the chemistry requirements of the steel supplied by cooling the strip to transform the austenite grains to ferrite in a temperature range from 850Â° C. to 400Â° C. at a selected cooling rate of at least 0.01Â° C./sec to produce a microstructure that provides a strip having a yield strength between 200 and in excess of 700 MPa, the microstructure being selected from the group consisting of: (i) predominantly polygonal ferrite; (ii) a mixture of polygonal ferrite and low temperature transformation products; and (iii) predominantly low temperature transformation products.