42CrMo4 / 1.7225 / 4140 Alloy steel description: Available sizes: Round: Dia. 20 ¨C 1200mm Flat: Thickness 20 ¨C 120mm, width 305 ¨C 660mm Delivery condition: Hot rolled or forged, Peeled or black surface, annealed or QT. Properties: One of the chromium, molybdenum, manganese low alloy steels noted for toughness, good torsional strength and good fatigue strength Applications: Statically and dynamically stressed components for vehicles, engines and machines. For parts of larger cross-sections, crankshafts, gears. Heat Treatment: Soft annealing: heat to 680-720C, cool slowly. Hardness after annealing: Max. 241 HB Hardening: 820 - 850 C Normalizing temperature: 840-880C Tempering: 540-680C.