AISI 4140 alloy steel round bar sheet plate has high fatigue strength and low notch sensitivity. Low-temperature impact toughness is also very high, no obvious temper brittleness. It is mainly used after quenching and tempering state. It is used to manufacture high-strength parts under impact loads and the fittings with large cross-sections and other stressed members. Such as the horizontal eccentric shaft of the horizontal forging machine, the crankshaft of the forging press, and etc. And the equivalent grade for it is DIN 1.7225 and JIS SCM440. 4140 Steel properties and chemical composition as below.