Control method of surface roughness of precision metal processing
Published on:
2021-02-01
The surface of metal processing is to change the size, shape and performance of the surface of the blank through fine machining or other methods to make it meet the requirements of the design drawing. However, the outer surface formed by turning the fine mechanical parts is not a complete and ideal appearance. After processing, a thin outer layer is formed on the surface of the part, and its characteristics are very different from those of the internal matrix. During fine metal processing, the surface is in a complex stress state of wedging, extrusion, fracture and friction during the entire cutting process, and undergoes elastic and plastic deformation. Under the combined action of cutting force, cutting heat and surrounding media, changes The original geometric characteristics and physical and mechanical properties of the workpiece surface. Therefore, the use of "surface quality" to evaluate the degree of conformity between the geometric, physical, chemical or other engineering properties of the surface layer of the processed part and the technical requirements of the part is mainly expressed in the following aspects.
Surface roughness: the micro-geometric features composed of peaks and valleys with small spacing on the surface of fine metal processing, which are mainly composed of the motion trajectory of cutting tools in fine machining, and the ratio of wave height to wavelength is generally greater than 1:50.
Surface waviness: The intermediate geometric shape error between the macro geometric shape error and the surface roughness, which is mainly formed by the offset and vibration of the cutting tool, and the ratio of the wave height to the wavelength is generally 1:50 to 1:1000.
Surface processing texture: the main direction of the surface microstructure, which depends on the fine machining method used for the surface structure, that is, the relationship between the main motion and the feed motion.
Scars: Defects appearing in some individual positions on the surface of fine metal processing, most of which are randomly distributed. Such as burrs, cracks and scratches.
Physical and mechanical properties of the outer layer: During the processing of precision mechanical parts, various complex physical and chemical changes occur on the surface of the parts, causing changes in the physical and mechanical properties of the outer layer. It mainly includes the following three aspects: the work hardening of the outer layer, the change of the metallographic structure of the outer layer, and the residual stress of the outer layer.
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