Vacuum Carburizing for Large Gear Applications

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We all know that gears are one of the most important parts of the transmission system of each of our cars. The role of the gear is to transmit power, and at the same time, it can change the speed and direction of the car. It is precisely because of the important role of gears in automobiles that we have high technical requirements and relatively complicated technical processes in the production of automobile gears.

For high-speed, heavy-duty precision gears, the gear surface is required to be hard and wear-resistant, but at the same time, the gear core must have very good toughness.

However, the high hardness and high toughness of the material itself are a pair of contradictory indicators, so there is the most commonly used process for advanced gears: carburizing. Because many carburizing steel workpieces have low carbon content, the gear surface cannot achieve high hardness by simple quenching, so the gear needs to be put into the carburizing furnace to infiltrate the gear surface with a layer of high carbon elements to achieve the required hardness. , so as to meet the two requirements of tough core and high hardness of tooth surface. The vacuum carburizing technology provided by CMe-D double chamber vacuum furnace is an advanced version of carburizing.

Vacuum carburizing has been widely used in automobiles, machinery, aerospace and other fields, showing a tendency to gradually replace controlled atmosphere carburizing. Especially in specific fields, vacuum carburizing shows its excellent performance. It is difficult to process special parts with general controlled atmosphere carburizing, but vacuum carburizing can be easily solved.

Vacuum carburizing, also known as low-pressure carburizing, is a chemical heat treatment process in which gas is infiltrated in an atmosphere below atmospheric pressure to allow carbon atoms to penetrate into the surface of the part. Its whole process is basically the same as that of ordinary gas carburizing. It consists of three processes: the decomposition of carburizing gas, the absorption of activated carbon atoms, and the inward diffusion of activated carbon atoms. The specific process includes parts cleaning, charging, and furnace extraction. Vacuum (≤2000Pa), heating and soaking (900-1000℃), carburizing and diffusion, heat treatment and other steps.

According to the different process parameters of each stage, the whole vacuum carburizing process can be divided into one-stage, pulse, and swing. Vacuum degree, temperature, carburizing time, etc. will vary with specific requirements.

Carburizing and diffusion pulse process: T1: first step acetylene time T2: first step diffusion time T3: final diffusion time.

The flow rate of carburizing gas should be able to increase the pressure in the furnace by 133.33Pa/s. At present, the carburizing media mainly used in vacuum carburizing heat treatment at home and abroad are C3H8 (propane) and C2H2 (acetylene). The temperature of vacuum carburizing is generally between 920 and 1080°C, and the specific selection is determined according to the type, shape and characteristics of the parts to be processed and the depth of the carburized layer.

Compared with the traditional carburizing process, vacuum carburizing has the following advantages:

Products treated by vacuum carburizing technology have good surface purification and activation effects, fast carburizing speed, and the carburizing time is about one-half to one-third of ordinary carburizing. Heated in a vacuum, there are no other abnormal carburizing gases present, so there are no oxidation problems. After the carburizing process, the temperature of the treated parts is uniform, and the carburizing is uniform. In vacuum carburizing, 22-29% of the heat is used for heating parts, and only 6-10% in ordinary carburizing, which is energy-saving and environmentally friendly, and has high thermal efficiency.

According to the different loading methods of carburizing workpieces, users can choose vertical or horizontal furnaces; according to different quenching methods, users can choose oil quenching or gas quenching furnaces; Hot chamber, carburizing chamber, carbonitriding chamber, slow cooling chamber or quenching chamber; according to the size of production, users can choose periodic vacuum carburizing equipment or production line vacuum carburizing equipment.

Due to a series of advantages of vacuum low-pressure carburizing technology, vacuum carburizing is more and more widely used in aerospace, automobile industry, shipbuilding, weapons and military industry, electronics, mold and other industries. Especially in the field of auto parts manufacturing.

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