Abstract: Air-hardenable steels of duplex bainite/martensite microstructure consisting essentially of 0.10 to 0.7% C, 0.1 to 2% Si, 2.1 to 3.5% Mn, 0.0005 to 0.005% B, up to 3.5% Cr and preferably containing Cr in amount of at least 0.1%, balance Fe except for incidental impurities. Optional elements are up to 1.5% W, 1.0% Mo, 0.15% V, 0.2% S, 0.1% Ca, 0.1% Pb, 0.1% Ti and 0.2% total rare earths. At least 1.0% Cr is especially preferred and if below such amount, total Mn and Si is at least 3% and in such case, if C is under 0.47%, at least 0.6% Si is present. The steels are hardenable to R.sub.c 2o to R.sub.c 58 and have a hardenable diameter in the range between 35 mm and 80 to 100 mm by air-cooling only, together with good strength, toughness and fatigue- and wear-resistance.

Abstract: Air-hardenable steels of duplex bainite/martensite microstructure consisting essentially of 0.10 to 0.7% C, 0.1 to 2% Si, 2.1 to 3.5% Mn, 0.0005 to 0.005% B, up to 3.5% Cr and preferably containing Cr in amount of at least 0.1%, balance Fe except for incidental impurities. Optional elements are up to 1.5% W, 1.0% Mo, 0.15% V, 0.2% S, 0.1% Ca, 0.1% Pb, 0.1% Ti and 0.2% total rare earths. At least 1.0% Cr is especially preferred and if below such amount, total Mn and Si is at least 3% and in such case, if C is under 0.47%, at least 0.6% Si is present. The steels are hardenable to R.sub.c 20 to R.sub.c 58 and have a hardenable diameter in the range between 35 mm and 80 to 100 mm by air-cooling only, together with good strength, toughness and fatigue- and wear-resistance.

Abstract: Steel articles have a granular bainite microstructure on continuous air cooling, from hot working temperature, of a low cost, tough, high strength, low alloy (HSLA) steel having a composition which, in broadest scope, scope, consists essentially, by weight percent, of 0.08 to 0.25% carbon, 0.30 to 1.5% silicon, 2.0 to 3.2% manganese and 0.005 to 0.005% boron. The steel composition preferably contains, in one aspect of the invention: 0.08 to 0.18% carbon, 0.3 to 1.2% silicon, 2.1% to 2.5% manganese and 0.005 to 0.004% boron; and in another aspect: 0.08 to 0.18% carbon 0.7 to 1.2% silicon, 2.7 to 3.1% manganese, and 0.0005 to 0.004% boron. The steel optionally may contain, by weight percent: up to 0.10 calcium and up to.0.20%, preferably less than 0.01%, sulfur, or up to 0.10% lead; up to 0.10%, especially 0.04 to 0.10%, vanadium, and up to 1.5% chromium. The steel is substantially free of molybdenum, tungsten and other alloying elements, except for residual amounts.