Precision gear vacuum heat treatment

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The vacuum heat treatment of gears includes vacuum heating and quenching and vacuum chemical heat treatment. Low-pressure vacuum carburizing and high-pressure gas quenching technology are used in the heat treatment of precision automobile gears to obtain smaller gear heat treatment deformation and better mechanical properties.

Low-pressure vacuum carburizing and high-pressure gas quenching technology has become a feasible alternative to controllable atmosphere due to its flexible process and modular design, high production efficiency, low operating cost and environmental protection. Compared with the traditional atmosphere carburizing and oil quenching technology, the low-pressure vacuum carburizing and high-pressure gas quenching technology has the following advantages:

(1) The vacuum carburizing speed is fast, and a high temperature carburizing process can be used. For example, the use of 980-1050 ℃ carburizing can significantly shorten the process time by 20%-40%, and reduce the holding time of the parts at high temperature, which is conducive to reducing high-temperature deformation. .

(2) The quenching intensity of high-pressure gas quenching is lower than that of oil quenching. Under the premise of ensuring the hardness of the parts, the cooling deformation of the parts is also much smaller.

(3) There are no three stages in the oil quenching process in the high-pressure gas quenching process, only the convection conduction process, and the parts are easier to obtain higher hardness.

(4) There is no oxygen atom in the low-pressure vacuum carburizing process, which can avoid the appearance of bad structures on the surface of the parts (such as internal oxidation, etc.) and improve the service life of the parts.

(5) The surface cleanliness of the treated parts is high, and there is no need for post-cleaning and strong shot blasting processes, which reduces production costs.

(6) Good environmental protection, no fire curtain, no emission of S02 and C0.

Vacuum heat treatment technology of gears

Vacuum quenching technology

Vacuum quenching technology includes vacuum oil quenching, negative pressure gas quenching and high pressure gas quenching. Among them, vacuum oil quenching is used for 920 ℃ vacuum oil quenching. The gear surface has no oxidation and decarburization, and the performance is uniform, which solves the problem of quenching and deformation of precision parts with complex structures. Nitrogen, 0.9×10°Pa) gas quenching; high-pressure gas quenching uses nitrogen, helium, hydrogen and helium+nitrogen to carry out high-pressure (such as 20×10°Pa) gas quenching for general alloy structural steel gears. Advanced gas quenching technology also realizes intermittent quenching according to program, controlled cooling, gas classification and isothermal operation. Using the relay and solenoid valve control system, the critical air volume in the pearlite area is chilled, and the small air volume in the martensite area is slow cooling, avoiding deformation and cracking; even three-stage cooling operation is realized.

Vacuum chemical heat treatment technology

Vacuum chemical heat treatment technology includes vacuum carburizing, vacuum carbonitriding, and vacuum ion heat treatment technology.

For vacuum carburizing, a disc of workpieces is put into a chamber of a vacuum carburizing furnace, and then evacuated to 270Pa. Carburizing gas is usually 130 ~ 2660Pa into the furnace. The incoming flow is set in the process menu, and the typical usage is 1 to 4m³/cycle. Nitrogen is often introduced during the diffusion stage to maintain a set pressure value. The carburizing gas is introduced and extracted in a pulsed manner. After the carburizing treatment, the workpiece is either heated in situ (single-chamber furnace) or quickly moved to a cooling chamber for slow cooling, oil quenching and high-pressure gas quenching.

Vacuum carbonitriding can further reduce gear deformation and improve gear wear and corrosion resistance, thereby greatly improving product quality.

Vacuum ion heat treatment techniques include ion nitriding, ion carburizing and ion carbonitriding. Due to the low nitriding temperature of ion nitriding, the gear deformation is small. In order to further increase the nitriding speed, adding an appropriate amount of rare earth organic solution into the atmosphere can increase the nitriding speed and shorten the nitriding cycle. %, the blind hole length and radius of the uniform layer obtained by this process are approximately twice that of gas carburizing. High temperature ion carburizing (>1000℃) can increase the carburizing speed; ion carbonitriding, carburizing atmosphere Add an appropriate amount of N. or NH to it, and ion carbonitriding at 780-860°C.

Process flow:

Material: Typical automotive fifth gear (8620H steel)

The process parameters are as follows:

Equipment selection: The VOGQ series vacuum heat treatment furnace produced by SIMUWU is a high-quality product for the vacuum heat treatment process of tooling and molds. Good temperature control accuracy and temperature control uniformity ensure the effective progress of the vacuum heat treatment process. SIMUWU specializes in the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc, which are widely sold in developed and developing countries.