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Influence of Vacuum Heat Treatment on Bearing Steel

Bearing steel is the steel used to manufacture rolling elements and inner and outer rings of rolling bearings, and is usually used in a quenched state. Rolling bearings need to bear high alternating loads during work, and the contact stress between the rolling elements and the inner and outer rings is large, and at the same time work in the lubricant medium. Therefore, rolling bearing steel has high compressive strength and fatigue resistance, certain toughness, plasticity, wear resistance and corrosion resistance, the internal structure of steel is uniform, and it has good dimensional stability after vacuum heat treatment.

Working conditions and performance requirements of bearing steel

The main applications of bearing steel are automobiles, railways, machine tools, wind power, etc. The working conditions are very complicated, bearing all kinds of high alternating stress, such as tension, compression, shear stress and friction, so that the bearing is prone to fatigue cracks and friction damage.

According to the working conditions and failure damage of the bearing, the performance of the bearing steel should meet the following requirements:

High and uniform hardness and high wear resistance contact fatigue strength;

High elastic limit and certain toughness and good dimensional stability;

Certain corrosion resistance;

Has good cold and hot processing properties.

In order to meet the performance requirements of bearings, the following three points need to be done for bearing steel:

1.The correct chemical composition

2.High metallurgical quality

3.Appropriate vacuum heat treatment process

Bearing Steel Vacuum Heat Treatment

Method: vacuum quenching + low temperature tempering. For GCr15 steel, the heating temperature for vacuum quenching is 830°C-860°C.

The influence of heating temperature: if the temperature is too high, it will cause overheating and grain growth, which will reduce the toughness and fatigue strength of the steel, and it will be easy to quench and deform; if the temperature is too low, the content of chromium and carbon dissolved in austenite will not be enough , The hardness of the steel is insufficient after vacuum quenching.

When the carbon content in martensite is 0.45%-0.5%, the bearing steel has high hardness, good toughness, and the highest contact fatigue life.

Vacuum heat treatment quality inspection

High carbon chromium bearing steel: hardness, microstructure, cracks, tempering stability, fracture, decarburization and soft spots, steel ball crushing load, ferrule deformation, etc.;

Carburized bearing steel: surface carbon content, coarse carbide, network carbide, surface hardness, core hardness, effective hardened layer depth, surface layer microstructure, core structure, decarburization and soft spots, cracks of finished parts , ferrule and deformation, tempering stability, etc.