What are the operating points of gas carburizing

Operation points of gas carburizing

The operation points of gas carburizing have the following aspects.

1. Surface cleaning and anti-seepage treatment of the workpiece. Before the workpiece enters the carburizing furnace, remove the surface dirt, rust and grease. Generally, cleaning methods can be used. If the surface quality cannot be guaranteed by cleaning, sandblasting can be used. Anti-seepage measures should be taken on the parts where carburization is not allowed on the surface of the workpiece. Commonly used anti-seepage methods include copper plating and coating anti-seepage ointment. The ointment can be self-made or purchased. Although the copper plating effect is good, the cost is relatively high, and the use is limited in some cases, so it is more convenient to apply the anti-seepage paste. In addition, you can also use the reserved processing amount, carburized out of the furnace and then use mechanical processing to remove the carburized layer, or use tightly fixed steel sleeves and collars to protect the parts on the workpiece that do not need to be carburized.

2. Determination of the installed furnace capacity. Too much furnace load will cause the furnace temperature to drop too much, the temperature difference between the workpiece near the furnace wall and the center of the furnace is large, and affect the normal circulation of carburizing atmosphere. If the furnace load is too small, the productivity will be low and the energy consumption will be high. In actual production, the furnace capacity should be determined according to the furnace working space size, workpiece shape and fixture method.

3. Furnace sealing and furnace gas circulation. In order to ensure the quality of carburizing, the furnace must be well sealed and keep the atmosphere in the furnace at a positive pressure. The normal circulation of the furnace gas is conducive to the uniformity of the furnace gas, so that the workpiece can often contact with the fresh atmosphere. Therefore, the fan should always be kept rotating during the operation, and a guide muffle that can circulate the furnace gas evenly should be placed in the furnace.

4. The atmosphere in the furnace is adjusted. Pit furnace should take gas for analysis 10 minutes after closing the exhaust hole. If the oxidizing atmosphere is too much, the supply of permeating agent or the ratio of enriched gas should be adjusted. For continuous furnaces, the control range of the dew point (or CO2) of the furnace gas in each zone should be determined through process tests, and the operation of the control instrument or computer should be checked frequently.

5. Determination of carburizing time. During production, due to the fluctuation of the state of the furnace workpiece or the composition of the infiltrant or due to external factors, the carburizing time specified in the carburizing process can only be used as a reference for the operator. The accurate time for baking should be determined according to the depth of the sample layer.

6. Cooling operation in the cooling kiln. It is not suitable to quench directly after carburizing, and for workpieces with high surface quality requirements, they should be placed in a cooling tank to slowly cool after being out of the furnace, and protective gas or liquid carburizing agent should be introduced immediately (until the temperature of the workpiece drops to 500℃ Stop) for protection.