Vacuum Carburizing Furnace

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Vacuum carburizing furnace refers to a process of carburizing at a pressure lower than one atmosphere, and is mainly applied to carburizing treatment (such as an engine, reduction box, etc.) of the core components of an automobile gearbox and a diesel nozzle.

The general process of vacuum carburizing furnace is: part cleaning, part loading, loading into vacuum carburizing furnace-pumping vacuum-heating and preheating — carburizing and diffusion-heat treatment.

(1) Carburizing agent: commonly used propane, methane, acetylene gas, or natural gas as a carburizing agent, the purity (volume fraction) is greater than 96%. In order to prevent the generation of carbon black, appropriate dilution of the gas (such as N2, H2, etc.).

(2) Carburizing gas flow rate and carburizing pressure: The flow rate of the carburizing gas is such that the pressure increase in the furnace is preferably 133.33 Pa/s. In the use of methane as carburizing gas, the furnace pressure is controlled at 26.6~45kPa. Propane is used as carburizing gas, and the furnace pressure is 13.3 to 23 kPa. The higher the carburizing pressure, the faster the carburizing and the more uniform the carburizing layer. But there are often more carbon blacks. Under the premise of ensuring uniform carburization layer, try to use low carburizing pressure to reduce carbon black production. If pulsed venting is used, the pressure of the furnace gas is controlled at about 20 kPa, and the fan can be stirred.

(3) Carburizing temperature: The effect of carburizing temperature on carburizing speed is the most obvious. The higher the temperature, the larger the diffusion coefficient and the faster the percolation rate. For example, the diffusion coefficient of carbon in iron increases by more than seven times when the temperature rises from 925℃ to 1100℃. The diffusion activation energy of carbon in r-Fe during vacuum carburizing is 24kcal/mol.

The gas carburizing (Q) is 36kcal/mol, so the vacuum carburizing process is faster than the gas carburizing process. The general carburizing temperature is between 920 and 1080 ℃.

(4) Carburizing time: The carburizing time is determined according to the carburizing temperature and the depth of the carburized layer.

Vacuum carburizing technology, also known as low-pressure carburizing technology, is a high-purity acetylene for rapid carburizing by introducing a carburizing medium into a high-temperature vacuum carburizing furnace under a low pressure (generally 0-30 mabar) vacuum process.