Damage to the bearing caused by improper heat treatment
Source:未知Author:hyzc Addtime:2021-07-13 Click:
Heat treatment is one of the core key processes of bearing manufacturers (bearing processing process). The heat treatment process and the physical properties of the raw materials determine the final hardness, wear resistance and contact fatigue life of the bearing. If the heat treatment is improper, what problems will the bearing have?
1. Heat treatment deformation
During the heat treatment of bearing parts, there are (will produce) thermal stress and structural stress. This internal stress can be superimposed or partially offset each other, which is complex and changeable, because it can change with the heating temperature, heating speed, cooling method, and cooling Speed, part shape and size change, so heat treatment deformation is inevitable.
The microstructure after quenching is overheated, the retained austenite in the structure increases, and the dimensional stability decreases. Due to the overheating of the quenched structure and the coarse steel crystals, the toughness of the parts will be reduced, the impact resistance will be reduced, and the life of the bearing will also be reduced.
Low quenching temperature or poor cooling will produce troostite structure in the microstructure that exceeds the standard, called underheated structure, which reduces the hardness and the wear resistance sharply, which affects the life of the bearing.
Due to insufficient heating, poor cooling, improper quenching operation, etc., the phenomenon of insufficient local hardness on the surface of bearing parts is called quenching soft point.
In the process of heat treatment, if the bearing parts are heated in an oxidizing medium, oxidation will occur on the surface to reduce the mass fraction of carbon on the surface of the parts, resulting in surface decarburization. Surface decarburization can also cause a serious decrease in surface wear resistance and fatigue strength. The depth of the surface decarburization layer exceeding the final machining allowance will cause the parts to be scrapped.