low pressure vacuum carburizing advantages and disadvantages

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Low pressure vacuum carburized parts have the general advantages of vacuum heat treatment, compared with ordinary carburized parts, they have more advantages as follows:
1. Good surface quality: the vacuum carburized surface does not oxidize or decarburize, which can keep the metal color; does not produce internal oxygen (black structure), which is helpful to improve the fatigue strength of parts; can greatly improve the reliability and service life of products. Vacuum carburizing will not contact with oxygen, so all defects caused by oxygen are avoided in vacuum carburizing.

2. It can deal with parts with complex shapes and small deformation of workpiece: when the vacuum carburizing workpiece is heated, the heating speed is continuously controllable, which can reduce the temperature difference between the inside and outside of the workpiece and small deformation; after carburizing, the quenching method is vacuum quenching, which greatly reduces the quenching deformation of the workpiece; reduces the processing amount in the later stage and saves the processing cost.
The deformation of workpiece can be effectively reduced by slowing down the heating speed properly. The heating speed of the vacuum carburizing furnace can be controlled, and the heating speed can be adjusted according to the complexity of the workpiece.

3. The depth of carburizing layer is more uniform: after the workpiece is heated to a uniform temperature, the carburizing gas is introduced to ensure the synchronization of the initial carburizing points of large and small workpieces, which is the basis of the uniform carburizing layer. However, conventional gas carburizing and multi-purpose furnace are difficult to ensure this. Vacuum can purify the surface of the workpiece, which is conducive to the adsorption of carbon atoms by the workpiece.
In conventional carburizing and multi-purpose furnace carburizing, there is no obvious boundary between gas driving and carbon potential establishment. Small parts arrive at temperature first and start carburizing first. The starting point of Carburizing for large and small parts is different. The carburizing starting point of low-pressure vacuum carburizing is the same. After heating to the temperature, all workpieces are heated to the temperature and homogenized, acetylene carburizing is started, so the carburizing layer uniformity of large and small carburized parts is the same.

4. The surface carbon content is easy to control: the surface carbon content of vacuum carburizing does not need to be controlled by carbon potential, but can be precisely controlled by controlling carburizing pressure and carburizing gas flow. The principle of vacuum carburizing is different from that of traditional gas carburizing.

5. Wide range of carburizing temperature: from low-temperature carburizing to the highest carburizing temperature can reach 1050 ℃, which can greatly save the process time for deep carburizing. It is more beneficial to complete the carburizing process of special steel grades. In the range of 880-1000 ℃, the carburizing speed of the same material increases with the increase of carburizing temperature. The carburizing speed at 980 ℃ can be twice as fast as 920 ℃. Vacuum high temperature carburizing can carburize special materials, such as martensitic stainless steel, ferritic stainless steel, H13, Cr12MoV, etc. For these materials, it is another carburizing type, namely carbide precipitation carburizing.

6. Stable carburizing quality: after the process parameters are set, the whole carburizing process is controlled by a microcomputer and the process parameters are recorded. The control system can accurately control the carburizing process, comprehensively monitor and record the operation status of the equipment, reduce the adverse factors in the process, and make the heat treatment workpiece have good repeatability and stable quality.

7. Wide range of application: vacuum carburizing can achieve the parts with blind holes, deep holes and slits or the parts with poor or even difficult carburizing effect of ordinary gas carburizing such as stainless steel. Vacuum carburizing can obtain a good carburizing layer.

8. Safety and environmental protection: the low-pressure vacuum carburizing equipment takes the common vacuum equipment as the platform and has all the environmental protection advantages of the existing vacuum heat treatment equipment. The production process is free of oil smoke, open fire, safety, environmental protection and pollution, and the working environment is clean.

9. High production efficiency: low pressure vacuum carburizing realizes high temperature and high speed carburizing, greatly shortens production cycle and effectively saves time and cost.
The advantages of low-pressure vacuum carburizing are obvious, but the disadvantages must also exist.
1) The cost of equipment is relatively high.
2) Compared with the multi-purpose furnace, the charging capacity of small parts will be less. During vacuum carburizing charging, especially for small parts, the gap between layers shall be about 50 mm.

vacuum carburizing furnace