4140 steel is suitable for shaft parts.
After quenching and tempering, it exhibits excellent strength-toughness balance, good hardenability, and the ability to withstand combined loads such as torsion and bending. It also possesses certain wear resistance and fatigue resistance, meeting the working requirements of medium to heavy-duty shaft components such as gear shafts, drive shafts, and machine tool spindles.
Furthermore, its machinability is controllable, facilitating subsequent turning, milling, grinding, and finishing processes.