Classification of bearing material surface hardening technology

When we understand the bearing manufacturing process, we usually find that the bearing will harden the surface of the material, which can strengthen the surface of the bearing and make the surface of the bearing material beautiful and smooth. The technical classification of the surface hardening of bearing steel materials is mainly divided into: There are five technical classifications: chemical heat treatment, surface deformation strengthening, surface heat treatment, surface metallurgical strengthening and membrane surface strengthening.

1. Chemical heat treatment

Using solid phase diffusion to some elements to change the chemical composition of the metal surface layer, to achieve surface strengthening means strengthening chemical heat treatment, also known as thermal diffusion. Including boronizing, carburizing, carburizing and carbonitriding, nitriding and nitrocarburizing, sulfide and sulfur nitrocarburizing, chromizing, aluminum and silicon infiltration, graphitized layer, etc., varieties, characteristics. Infiltrate the element or dissolve into the base metal to form a solid solution, or form a compound with other metal elements. In the short chemical composition, the elements of the surface layer can be changed, and different phase structures can be obtained. Carburized bearing steel reinforcement process and Timken imported needle roller bearing sleeve surface reinforcement method nitriding.

2. Surface deformation strengthening

The metal surface layer is mechanically and plastically deformed to form a hardened layer with high hardness and high strength. The method of surface strengthening is called enhanced surface deformation, also called work hardening. Including shot blasting, sandblasting, cold extrusion, rolling, rolling and impact, explosion impact, etc. The characteristics of these methods are: increasing the density of strengthening dislocations, the refinement of substructures, the increase in hardness and strength, and the decrease in surface roughness, which can significantly increase the surface fatigue strength of parts and reduce fatigue notch sensitivity. This kind of reinforcement method has the advantages of simple process and obvious effect, has a hardened layer and a matrix structure, has no obvious boundary between the coherence, and is not easy to fall off and use. Many of the methods have been applied to the imported bearing industry: the application of surface impact to strengthen this rolling element method, precision rolling into a new reinforcement method for ferrule processing.

3. Surface heat treatment

The use of solid-state phase change, the quenching treatment of the parts, is called surface heat treatment, and the surface layer is rapidly heated, 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: the surface is locally quenched, and the deformation of the workpiece is small; the heating speed is fast and the production efficiency is high; the heating time is short, and the surface oxidation and decarburization are very slight. This method is especially useful for improving the wear resistance and fatigue strength of large and extra-large imported bearing parts under obvious impact loads.

4. Surface metallurgy strengthening

Melting and solidification of the metal surface layer, in order to obtain the desired surface strengthening technology composition or structure surface metallurgical strengthening. Including surface self-dissolving alloy or composite powder coating, surface melting crystallization or amorphous treatment, surface alloying methods. Rapid heating with high energy density, metal surface layer or coating alloy material melting metal surface, followed by enhanced cooling and solidification, to obtain special structure or specific performance. This special structure or crystal structure refinement may also be the supersaturation stage, the metastable phase, or even the amorphous structure, according to different process parameters and surface metallurgy methods. In the miniature imported bearing imported bearing industry rolling work laser heating surface strengthening research, good results.

5. Film surface strengthening

Using physical or chemical methods, the performance of the metal surface coating on the substrate material of the different reinforcement layers is called the enhanced surface film. It includes electroplating, electroless plating (chromium, nickel, copper, silver, etc.) and composite electroplating, brush plating or conversion process, including the rapid development of high technology in recent years: such as CVD, PVD, P-CVD and other vapor-deposited films Strengthening methods and ion implantation surface strengthening technology (also known as atomic metallurgy technology), etc. Their common feature is that the film can form specific properties on the working surface, improving the surface's wear resistance, fatigue resistance, corrosion resistance and self-lubricating properties. For example, the surface strengthening technology of ion implantation imported bearings can significantly improve the wear resistance, corrosion resistance and contact fatigue resistance of imported bearings, and double the life of imported bearings.