AISI 4140 is defined as a low alloy steel which has 1% Cr-Mo as strengthening alloy elements,widely used in general purpose high tensile steel for components, like axles, shafts, bolts, gears and other applications. Compared with AISI 4130, it has a higher carbon content with good balance of strength, toughness ,abrasion and impact resistance and heat treatment capabilities,but poor in weldability characteristics.AISI 4140 is generally supplied in quenched and tempered condition with hardness 28-34HRC.