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Surface deformation strengthening
The metal surface layer is plastically deformed by a mechanical method to form a hardened layer of high hardness and high strength. This surface strengthening method is called surface deformation strengthening, which is also called work hardening. Including shot peening, sand blasting, cold extrusion, rolling, cold rolling and impact, explosion shock strengthening. The characteristics of these methods are: increased dislocation density of the strengthening layer, refinement of the subgrain structure, thereby increasing the hardness and strength, and reducing the surface roughness value, which can significantly improve the surface fatigue strength of the part and reduce the sensitivity of the fatigue gap. The strengthening method has simple process and remarkable effect, and there is no obvious boundary between the hardened layer and the matrix, the structure is continuous, and it is not easy to fall off during use. Most of its methods have been applied in the bearing industry: the surface impact strengthening of rolling elements is the application of such methods, and precision rolling has become a new method of ferrule processing and strengthening.
2. Surface heat treatment strengthening
The use of solid phase transformation, quenching the surface layer of the part by rapid heating is called surface heat treatment, commonly known as surface quenching. Including flame heating quenching, high (medium) frequency induction heating quenching, laser heating or electron beam heating quenching. The characteristics of these methods are: local surface heating and quenching, small deformation of the workpiece; fast heating speed, high production efficiency; short heating time, surface oxidative decarburization is very slight.
This method is particularly effective in improving the wear resistance and fatigue strength of large and extra large bearing parts subjected to a certain impact load.
The working surface and the core of the bearing parts are quite different in terms of state, structure and performance requirements, and the overall heat treatment often makes it impossible to balance the potential of the material. Applied material surface strengthening technology not only can better solve the difference in structure and requirements between surface and core, but also can further obtain some special working performance of the surface to meet the bearing surface performance of working under certain conditions. Requirements. This is very meaningful in the development of modern science and technology. The traditional surface strengthening method is technically a category of heat treatment. The surface strengthening methods such as laser, electron beam and ion beam developed in modern times not only apply some high-tech to the surface strengthening of materials, but also go beyond the traditional heat treatment field in the process, forming a new technical field. Therefore, the current surface strengthening technology can form a variety of classification methods from different angles. According to the physical and chemical processes of surface strengthening technology, it can be roughly divided into five categories: surface deformation strengthening, surface heat treatment strengthening, chemical heat treatment strengthening, surface metallurgy strengthening. Surface film strengthening.