Shaft parts are rotating parts, whose length is greater than the diameter. They are generally composed of cylindrical surfaces, conical surfaces, inner holes, threads and corresponding end faces of concentric shafts. According to different structural shapes, shaft parts can be divided into optical axis, stepped axis, hollow axis and crankshaft.
1、 Blank selection of shaft parts
According to the use requirements, production types, equipment conditions and structures, shaft sleeve parts can choose blank forms such as bars and forgings. For the shaft with little difference in the diameter of the outer circle, it is generally dominated by bars; Forgings are often used for stepped shafts or important shafts with large external diameter differences, which not only saves materials, reduces the workload of machining, but also improves mechanical properties.
According to the different production scale, there are two forging methods of blank: free forging and die forging. Free forging is often used in small and medium-sized batch production, and die forging is used in mass production.
2、 Material analysis of shaft sleeve parts
The blank material is 20cr380*55mm, and the workpiece is long. It is difficult to process the slender shaft. It is necessary to select a reasonable machine tool and adopt the corresponding processing scheme, and select reasonable cutting parameters and props to obtain the surface roughness Ra0.4.
The material selected for part cutting is 20Cr, which can improve the structure and cutting performance after normalizing; Eliminate internal stress.
Normalizing the workpiece after forging can eliminate the internal stress generated during forging, refine the grain, reduce the hardness and improve the processing performance.
Since most of the allowance has been removed after rough machining, the diameter of the workpiece is reduced and it is easy to harden. After high temperature tempering, the tempered sorbite structure with good toughness and impact resistance can be obtained in the central layer. Quenching and tempering treatment can eliminate part of the internal stress caused by rough machining, instead of aging treatment, and the deformation of the workpiece after quenching and tempering can be eliminated in the next process. After finishing turning, high-frequency quenching is carried out to improve the strength, hardness and wear resistance of the spindle. Quenching deformation can be eliminated by grinding in the subsequent process, so the material selection and heat treatment requirements of this part are reasonable.