Shaft part is one of the typical parts in machines. It is mainly used to support transmission components, transmit torque and bear loads. The shaft part is a kind of rotating part whose length is larger than the diameter. Generally, it consist of the outer cylindrical surface, the conical surface, the inner hole, the thread and the corresponding end surface of the concentric shaft. According to the shape of the structure, the shaft parts can be divided into a plain axis, a stepped shaft, a hollow shaft and crankshaft. Common shaft steel material include
S45C carbon steel, 1045 carbon steel, SCR440 alloy steel, 5140 alloy steel, 52100 bearing steel, etc.
S45C carbon steel is a kind of commonly used material for shaft parts. It is cheap and has good cutting performance after quenching and tempering (or normalizing), and high mechanical strength can be obtained, such as high strength and toughness. The surface hardness after quenching can reach 45HRC to 52HRC. S45C carbon steel is widely used in machinery manufacturing, and the steel has good mechanical properties. But this is medium carbon steel, the quenching performance is not good.
S45C carbon steel can be hardened to HRC42 to HRC46. Therefore, if both surface hardness and superior mechanical properties of S45C steel is required, S45C steel is often quenched (high-frequency quenching or direct quenching), so that the required surface hardness can be obtained. SCR440 alloy structural steel is suitable for shaft parts with medium precision and high speed. This steel has good comprehensive mechanical properties after quenching and quenching. Surface hardness of bearing steel 52100 and spring steel 65Mn can reach 50HRC to 58HRC and have high fatigue resistance and good wear resistance after quenching and tempering and surface quenching, which can produce higher precision shaft. The spindle of a precision machine tool (such as grinding wheel shaft and coordinate boring spindle) can be made of 38CrMoAIA nitrided steel. After quenching, tempering and surface nitriding, the steel not only achieves high surface hardness, but also maintains a soft core and good impact toughness. Compared with carburized and quenched steel, it has the characteristics of small heat treatment deformation and higher hardness.