Abstract: A drive train gear having a plurality of teeth thereon is formed of an alloy steel having a predominantly homogeneous and substantially complete low temperature bainite microstructure, including less than 10 Vol % austenite. The gear preferably consists essentially of preselected weight percentages of carbon, manganese, silicon, molybdenum, boron and the balance substantially iron. Such a gear has a high tensile strength, a reduced distortion during heat treatment, and a through hardness level of at least Rc56 therethrough.

Abstract: A method of making a low temperature bainite steel alloy gear includes forming a toothed gear having preferably preselected weight percentages of carbon, manganese, silicon, molybdenum, boron and the balance substantially iron, heating the gear to assure a substantially complete austenite morphology, quenching the gear toward a preselected temperature and avoiding transformation, and then holding the gear at the preselected temperature less than about two hours and transforming the austenite directly to substantially complete lower temperature bainite. Energy is saved by the short holding time and the usual further processing of the gear is avoided.

Abstract: A lower bainite alloy steel article particularly suitable for gears, bushings and the like includes carbon in the range of 0.60 to 0.80 Wt.%, manganese in the range of 0.45 to 1.00 Wt.%, silicon in the range of 0.15 to 2.20 Wt.%, molybdenum in the range of 0.40 to 0.70 Wt.%, and the balance substantially iron. A process of heat treatment of the article includes the steps of quenching it from a first temperature at a preselected rate and of holding it at a second temperature for less than about two hours to complete transformation of the alloy directly from an austenite morphology to a substantially complete low temperature bainite morphology.