This alloy has high strength, high fatigue strength, toughness, torsional strength, and impact and abrasion resistance. Additionally, 4140 steel is highly ductile when annealed, though it requires more pressure as it is tougher than most carbon steels. 4140 is easily welded, but if this is done after hardening, it will also require a post weld heat treatment. This material is typically used in aerospace, oil, gas, automotive, agricultural, and defense industries, specifically gears, shafts, spindles, fixtures, and collars.
