Classification Of Surface Hardening Technology Of Imported Bearing Materials

In the process of bearing manufacturing, we usually find that the bearing will be hardened on the surface of the material, which can strengthen the bearing surface, and let the bearing material surface get beautiful, smooth and so on. Bearing steel material surface hardening technology classification, it is mainly divided into: chemical heat treatment, surface deformation strengthening, surface heat treatment, surface metallurgical strengthening and film surface strengthening five technical classification.

1. Chemical heat treatment

The use of solid phase diffusion to some elements, change the chemical composition of the metal surface layer, for the realization of surface strengthening of the method of strengthening chemical heat treatment, also known as heat diffusion. Including boronizing, carburizing, carburizing and carburizing, nitriding and nitrogen carburizing, sulfide and sulfur carburizing, chromizing, aluminum and silicon penetration, graphitized layer, varieties, characteristics, etc. Infiltrating elements or dissolving into the matrix metal to form solid solutions, or forming compounds with other metal elements. In short chemical components, the elements of the surface layer can be changed and different phase structures can be obtained. Carburized bearing steel reinforcement treatment process and Timken imported needle roller bearing sleeve surface this reinforcement method nitriding.

2. Surface deformation strengthening

Mechanical methods and plastic deformation of the metal surface layer, thus forming a high hardness and high strength of the hardened layer, the surface strengthening method is called enhanced surface deformation, also known as work hardening. Including shot peening, sandblasting, cold extrusion, rolling, rolling and impact, explosion impact, etc. These methods are characterized by the increase of dislocation density, the refinement of substructure, the increase of hardness and strength, and the decrease of surface roughness, which can significantly improve the surface fatigue strength of parts and reduce the fatigue notch sensitivity. This reinforcement method has the advantages of simple process and remarkable effect. There is no obvious boundary between the hardened layer and the matrix structure, and it is not easy to fall off and use. Many methods have been applied to the imported bearing industry: the application of surface impact to strengthen the rolling element method, precision rolling has become a new reinforcement method of ring processing.

3. Surface heat treatment

The use of solid phase transformation, by the quenching treatment of parts, called surface heat treatment surface layer rapid heating, commonly known as surface hardening. Including flame quenching, high (medium) high frequency induction heating quenching, laser heating or electron beam heating quenching. The characteristics of these methods are: local quenching of the surface, small deformation of the workpiece; Fast heating speed, high production efficiency; Heating time is short, surface oxidation and decarbonization are very slight. This method can especially improve the wear resistance and fatigue strength of large and extra large imported bearing parts under obvious impact load.

4. Surface metallurgical strengthening

The melting and solidification of the metal surface layer, in order to obtain the desired surface strengthening technique of the composition or tissue surface metallurgical strengthening. Including surface autolytic alloy or composite powder coating, surface melting crystallization or amorphous treatment, surface alloying methods. With high energy density of rapid heating, metal surface layer or coating alloy material melting metal surface, followed by enhanced cooling curing, get special structure or specific properties. This particular structure or crystalline structure refinement may also be supersaturated phase, metastable phase, or even amorphous structure, depending on different process parameters and surface metallurgical methods. Research on laser heating surface strengthening of rolling work in micro import bearing industry, good results.

5. Film surface strengthening

By physical or chemical methods, the surface of a metal is coated with different reinforced layers of substrate material properties, called enhanced surface film. It includes electroplating, electroless plating (chromium, nickel, copper, silver, etc.) and composite plating, brush plating or conversion processes, including the rapid development of high technology in recent years: such as CVD, PVD, P-CVD and other vapor deposition film strengthening methods and ion implantation surface strengthening technology (also known as atomic metallurgy technology). Their common feature is that the film can form specific properties on the working surface, which improves the wear resistance, fatigue resistance, corrosion resistance and self-lubricating performance of the surface. For example, the surface strengthening technology of ion implantation imported bearing can make the wear resistance, corrosion resistance and contact fatigue resistance of imported bearing surface have been significantly improved, and the life of imported bearing has been doubled.