Reasons for surface oxidation of mold after nitriding

The surface oxidation of the mold after nitriding not only affects the appearance quality of the mold, but also affects the hardness and wear resistance of the mold surface, which is one of the reasons that affect the service life of the mold. Let's first find out the reason, the reason for the surface oxidation of the mold after nitriding:

(1) The gas nitriding tank is leaking or the furnace cover is not properly sealed.

(2) The desiccant in the drying device that supplies ammonia gas fails, and the ammonia gas passed into the furnace contains moisture.

(3) After the nitriding is completed, when the furnace is cooled down, insufficient oxygen supply causes negative pressure in the tank, and the inhalation of air causes oxidation color.

(4) After the mold is nitrided, the furnace temperature is too high and oxidized in the air.

For the problem, find a way to deal with it.

(1) The equipment should be checked frequently, the leaking muffle should be replaced in time, and the furnace cover should be kept well sealed.

(2) The desiccant in the ammonia drying device should be replaced regularly.

(3) The mold after nitriding is best to use oil cooling. For molds that require strict control of deformation, a small amount of ammonia gas should be continuously provided at the end of nitriding to avoid negative pressure in the furnace. The temperature of the furnace is controlled below 200℃ to avoid oxidation of the nitriding mold in the air.

(4) The nitriding mold that has been oxidized can be cleaned by blasting fine sand at low pressure, and reheated to about 510°C for 4h nitriding. After nitriding, the furnace is cooled to below 200°C and discharged.