Patent ID: 7169243

Claim:
A process comprising a first cold-rolling of a hot-rolled steel strip to form a first cold-rolled steel strip; annealing the first cold-rolled steel strip; and a second cold-rolling of the annealed first cold-rolled steel strip, wherein the hot-rolled steel strip comprises from 0.040 to 0.080% of carbon, from 0.35 to 0.50% of manganese, from 0.040 to 0.070% of aluminum, from 0.0035 to 0.0060% of nitrogen, and the remainder being iron and trace impurities, where % is % by weight based on the total weight of the hot-rolled steel strip; wherein the annealing is a continuous annealing comprising: raising the temperature of the first cold-rolled steel strip to a first temperature in a range of from 740° C. to 780° C., then holding the first cold-rolled steel strip above the first temperature for longer than 10 seconds, and then rapidly cooling the first cold-rolled steel strip to a second temperature of below 350° C. at a cooling rate of from 100° C./s to 300° C./s; and wherein the second cold-rolling is at a percentage elongation of from 2 to 16% and results in an aluminum-killed medium carbon steel strip having a maximum rupture strength Rm in a range of from 500 to 650 MPa.