Patent ID: 6395109
Filing Date: 2002-05-28
Classification: C21D,C22C

Abstract:
A bar product comprising:(a) hot rolled and heat treated microalloyed bar steel prepared by steps of: (i) hot rolling a preform comprising the microalloyed bar steel at a temperature of between about 1,400Â° F. and about 2,300Â° F. to provide a steel bar having a diameter of between about Â¾ inch and about 4 inches; (ii) cooling the steel bar to provide a surface temperature below about 1,100Â° F.; and (iii) heat treating the steel bar in an environment at a temperature of between about 500Â° F. and about 1,300Â° F.; (b) said microalloyed bar steel comprising: (i) about 0.36 wt. % to about 0.55 wt. % carbon; (ii) about 0.60 wt. % to about 0.90 wt. % manganese; (iii) about 0.01 wt. % to about 0.40 wt. % nickel; (iv) about 0.01 wt. % to about 0.30 wt. % chromium; (v) about 0.01 wt. % to about 0.15 wt. % molybdenum; and (vi) about 0.005 wt. % to about 0.50 wt. % microalloying additive comprising at least one of columbium (niobium), vanadium, titanium, aluminum and nitrogen; and (c) said hot rolled and heat treated microalloyed bar steel having a tensile strength of greater than about 105 ksi, a yield strength of greater than about 90 ksi, an elongation in two inches of greater than about 7%, and a reduction of area of greater than about 20%.