Mar 15, 2019
1. Carbon steel 35, 45, 50 and other high-quality carbon structural steels have higher comprehensive mechanical properties and are used more widely, among which 45 steel is the most widely used. In order to improve its mechanical properties, normalizing or quenching and tempering should be carried out. Carbon steels such as Q235 and Q275 can be used for shafts that are not important or have low forces.
2. Alloy steel alloy steel has high mechanical properties, but the price is more expensive, and it is mostly used for shafts with special requirements. For example, high-speed shafts with sliding bearings, commonly used low-carbon alloy structural steels such as 20Cr and 20CrMnTi can improve the wear resistance of the journal after carburizing and quenching; the rotor shaft must work well under high temperature, high speed and heavy load conditions. For high temperature mechanical properties, alloy structural steels such as 40CrNi and 38CrMoAlA are often used. The blank of the shaft is preferentially forged, followed by steel; for larger or complex structures, cast steel or ductile iron can be considered. For example, the manufacture of a crankshaft and a camshaft from ductile iron has the advantages of low cost, good vibration absorption, low sensitivity to stress concentration, and good strength. The mechanical model of the shaft is the beam, which is mostly rotated, so its stress is usually a symmetric cycle. Possible failure modes include fatigue fracture, overload fracture, and excessive elastic deformation. Some parts with hubs are usually installed on the shaft, so most shafts should be made into stepped shafts with a large amount of machining.