Patent ID: 9493864
Filing Date: 2016-11-15
CPC Classification: C21D,C22C

Claim Text:
1. A process for producing high strength steel, the process comprising: providing a steel slab having a chemical composition in weight percent in a range of 0.025-0.070 C, 1.50-1.70 Mn, 0.050-0.085 Nb, 0.022 max Ti, 0.065 max N, 0.0040 max S, 0.10-0.45 Si, 0.070 max P, with the remainder or balance being iron (Fe) and incidental impurities, the quantity of Nb and C in weight percent obeys the relationship log(Nb·C) is less than or equal to −2.33 and a Ti to N ratio is between 2.0-4.0, inclusive; soaking the steel slab between 1150-1230° C.; hot rolling the steel slab using a roughing treatment and producing a transfer bar; hot rolling the transfer bar using a finishing treatment and producing hot rolled strip; cooling the hot rolled strip using a cooling rate between 10-100° C./sec; and coiling the cooled hot rolled strip at a temperature between 580-400° C., the coiled hot rolled strip, the coiled hot rolled strip having a yield strength of at least 80 ksi and a DWTT transition temperature equal to or less than −20° C.