Intruction of shaft and common used material
Introduction
The shaft is a cylindrical object that is worn in the middle of a bearing, a wheel, or a gear, but a small part is square. A shaft is a mechanical part that supports and rotates with a rotating part to transmit motion, torque, or bending moment. Generally round metal rods, each section can have different diameters. The parts in the machine that perform rotary motion are mounted on the shaft.
Use of materials
1.Carbon steel
High-quality carbon structural steels such as 35, 45, and 50 have many applications due to their high comprehensive mechanical properties. Among them, 45 steel is the most widely used.
In order to improve its mechanical properties, it should be normalized or quenched and tempered. For shafts that are not important or subject to small forces, carbon structural steels such as Q235 and Q275 can be used.
2.Alloy steel
Alloy steel has higher mechanical properties, but is more expensive, and is mostly used for shafts with special requirements.
For example, high-speed shafts using sliding bearings are usually low-carbon alloy structural steels such as 20Cr and 20CrMnTi. After carburizing and quenching, the journal wear resistance can be improved;
Turbine generator rotor shafts work under high temperature, high speed, and heavy load conditions, and must have good high temperature mechanical properties, often using 40CrNi, 38CrMoAlA and other alloy structural steel.
Forgings of shafts are given priority to forgings, followed by round steel;
Larger sizes or complex structures can consider cast steel or ductile iron.
For example, the manufacture of crankshafts and camshafts with nodular cast 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 a beam, most of which rotates, so its stress is usually a symmetrical cycle.
The possible failure forms are: fatigue fracture, overload fracture, excessive elastic deformation, etc.
Some parts with a hub are usually installed on the shaft, so most shafts should be made into stepped shafts with a large amount of cutting.
