Development of a New Type of Vacuum Carburizing Furnace

Jinan Qingqi Engine Co., Ltd. (Jinan 250101) Wang Bing Zhang Yuhe Compiler 0 Foreword Vacuum carburizing furnaces have been used as a new type of heat treatment equipment since 1984 because of the high quality of parts after heat treatment and the excellent working environment. use. The reason is that many carbon blacks are produced in the vacuum carburizing furnace at that time, and there are many problems in the maintenance of the device. However, due to the implementation of high-vacuum carburizing, the issue of carbon black has been basically solved recently. Therefore, vacuum carburizing furnaces and low distortions have been developed that improve the quality of heat treatment, increase the operational flexibility, improve the working environment and safety, and save energy and reduce operating costs. A new type of vacuum carburizing furnace combined with quenching tanks.

1 Vacuum Carburizing Furnace Overview The rear of the vacuum carburizing furnace is a heating chamber with an oil groove in the front.

Auxiliary devices include vacuum exhaust devices, carburizing gas inlet devices, temperature and atmosphere control devices, etc. Table 1 shows the basic parameters of this device.

Table 1 Basic Parameters of a New Type of Vacuum Carburizing Furnace Effective Dimensions Loaded M Total Weight/Heat Heater Electricity and Gas Up to Vacuum Degree Quenching and Cooling+Air Forced Cooling Carburizing Atmosphere Unsaturated Hydrocarbon Gas Material Handling Method Push-Pull Treatment Type Vacuum Permeability Carbon carbonitriding carburizing, slow cooling, reheating annealing, normalizing oil quenching (1 tank 3 quenching, quenching under reduced pressure) 1.1 Furnace heating chamber is hot wall type, thermal insulation material uses ceramic fiber. Heating device can choose electric heating or combustion type high performance radiant tube burner. The burner has a combustion efficiency of 70% 80%. The furnace temperature distribution of this furnace, whether electric or combustion type, does not fluctuate more than 6 radiant tube burners from a diffusion temperature in the range from 800 to 1050T. It can be used as a cooler at the quenching temperature, so the cooling time is shorter than that of the electrothermal type.

The material handling is carried out by a push-pull mechanism located on the oil tank. A recirculating fan is installed in the furnace, and the temperature of the material is increased and the temperature is decreased. The fan is rotated by the N2 repressurization and the time is greatly shortened compared to heating and cooling in a vacuum.

1.2 The Pinghu Oil Tank is attached to the quenching oil tank of this device, not only for simple bonfires, but also to minimize the deformation during quenching.

The conventional salt bath quenching is widely used due to its small deformation. However, if the salt bath is not clean after quenching, the salt attached to the rack will damage the furnace material. In addition, due to environmental problems caused by the washed water, a large amount of water treatment costs will be required. For this purpose, a new oil quenching method with one tank and three grades of fire has been developed. This method is a step quenching process in which a series of quenching cycles such as one anneal, soaking, and second quenching are performed in a quenching bath in one tank. The deformation of the work piece treated by this method is equivalent to that of salt bath grade quenching.

2 Vacuum carburizing 2.1 Selection of carburizing gas The carburizing gas used in vacuum carburizing is hydrocarbon gas.

General use of propane, acetylene and so on. Since unsaturated hydrocarbons have higher stability at high temperatures than saturated hydrocarbons, the carburizing gas uses unsaturated hydrocarbons.

2.2 Principle of vacuum carburizing Vacuum carburizing is a direct carburizing method using hydrocarbon gas. Hydrocarbon gas is adsorbed on the surface of the workpiece to be treated, and carburization occurs when it is decomposed.

The results of gas analysis in the vacuum carburizing furnace are mostly H2 and contain a small amount of hydrocarbon gas. According to this result, the following chemical reaction mainly occurs in the furnace, and it can be considered as a reaction that causes carburization.

+H23 vacuum carburizing data The following is an example of the results of the heat treatment performed in this vacuum carburizing furnace. The target depth of the effective carburized layer of vacuum carburizing treatment is 1 mm, and the sample material used is S420. The hardness distribution deviation of the sample within the effective size heated by the method is within 0.1 mm, and the metallurgical structure is free from grain boundary oxidation. The difference between the effective carburized layer of the gear tooth surface and the tooth bottom is small and the organization is the same, and the hole portion can also be fully carburized. With regard to the relationship between the depth of the effective carburized layer and the carburizing time, as shown in the figure, the total time for the carburizing plus diffusion time at the 950T carburization is reduced by about 40%. 4 Conclusion The new type of vacuum carburizing furnace and the traditional Compared with carburizing furnaces that generate gas, the emissions of C2 are greatly reduced, the surrounding environment is greatly improved, and the heating cycle is shortened. If the combustion type is adopted, the total energy can be saved (electrical power generation efficiency is 40% or less, and the combustion type combustion efficiency is 70% to 80%). Because of its advantages of improving quality, reducing operating costs, and improving the environment, it will be widely used in heat treatment production.

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