Heat treatment technology and equipment of the hot

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Bearing heat treatment technology and equipment (II)

2 Tooling equipment for conventional martensite quenching at present, the tooling equipment for conventional martensite quenching in China's bearing industry is uneven. From the perspective of protective medium, it can be divided into oxidation furnace without protective medium, controllable atmosphere furnace and vacuum furnace. The oxidation furnace without protective medium accounts for about 25% of the bearing heat treatment equipment, the less oxidation furnace with protective medium accounts for about 50% of the bearing heat treatment equipment, the controllable atmosphere furnace accounts for about 20% of the bearing heat treatment equipment, and the vacuum furnace accounts for about 5% of the bearing heat treatment equipment. The production cycle can be divided into periodic furnace and continuous furnace

in recent decades, the development of tooling and equipment for martensite quenching has mainly focused on the following aspects:

the change type extensometer supporting the experimental machine mostly refers to the axial extensometer to issue calibration certificates (1) automatic production lines. At present, the automatic production lines adopted in China can be divided into: muffle belt furnace, muffle belt furnace without muffle belt furnace, chain casting furnace, roller hearth furnace The roller hearth furnace with furnace and rotary hearth furnace series production lines can automatically complete feeding, pre cleaning, heating under protective atmosphere (or controllable atmosphere), quenching, post cleaning (sometimes secondary cryogenic roller hearth furnace for secondary cryogenic) and tempering. The production line has a high degree of automation and control precision, and the quality of the workpiece after treatment is uniform. The whole heat treatment production line can be used as a part of the bearing automatic production line. Different heat treatment production lines are suitable for different types and sizes of bearing parts according to their structural characteristics. It can be handled by adding pads to the hot parts and then tightening the screws. For example, the furnace is suitable for small and medium-sized bearing rings; Rotary hearth furnace is suitable for small batch of bearing rings; Roller hearth furnace is equipped with automatic lifting quenching device, which is suitable for bearing parts with large wall thickness; Roller furnace is suitable for rolling elements and small ferrules

(2) the multi-purpose furnace can be used for carburizing or carbonitriding in a controlled atmosphere and quenching in a protective atmosphere to complete the non oxidation quenching process of the workpiece. It is a kind of periodic furnace, which is mainly applicable to the heat treatment of small batch and multi variety bearing parts

(3) induction heating quenching and tempering equipment need to set new parameters for adjustment heating, which has the advantages of fast heating speed, energy saving and small deformation. The processed workpiece has some properties that conventional heating does not have. At present, the standards of government departments for bearing heat treatment in China are becoming more and more stringent, mainly focusing on rotary table bearings and car hub bearings, but not on GCr15 steel

(4) heating in the vacuum state of the vacuum furnace can reduce or avoid the oxidation of the workpiece. Combined with high-pressure gas quenching, the cooling and deformation of the workpiece can be controlled to avoid the environmental pollution caused by oil quenching and realize clean heat treatment. In addition, after vacuum heat treatment, the microstructure of the workpiece is more fine and uniform, the surface and heart structure are consistent, and the hardness is uniform, which is conducive to the improvement of bearing fatigue life. Vacuum furnaces are mainly used for heat treatment of special steels (heating temperature above 1000 ℃) and quenching of bearing parts made of GCr15 steel with high requirements. They are widely used in the field of bearing heat treatment in China. The development trend of vacuum furnace is to replace oil quenching with ultra-high pressure gas quenching, and to apply vacuum carburizing furnace to solve the application of new steel in bearing field

(5) quenching cooling medium and equipment quenching medium can be divided into three categories: oil-based, water-based and gas quenching medium. Oil based quenchants are the most commonly used quenchants. Ordinary quenching oil is N32 or N22 full system loss oil. In order to improve its cooling performance, anti-aging performance, brightening performance and high-temperature performance, a series of quenching oils, such as quick oil, quick brightening oil and high-temperature graded isothermal oil, have been formed to be used for the quenching of bearing parts with different sizes and requirements by adding a refrigerant, a cleaning agent, a brightener and an antioxidant; In addition, there is low volatile vacuum quenching oil. The disadvantage of oil-based quenching medium is that it produces oil fume during quenching, which causes air pollution and water pollution during subsequent cleaning

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