The well type furnace manufacturer will introduce the cleaning process of the part surface before the well type nitriding furnace:

1、 Overview of Nitriding Treatment

Nitriding treatment refers to a chemical heat treatment process that allows nitrogen atoms to penetrate into the surface of the workpiece in a certain medium at a certain temperature. The nitrided products have excellent wear resistance, fatigue resistance, corrosion resistance and high temperature resistance.

2、 Surface cleaning of parts before nitriding

Most parts can be nitrided immediately after degreasing by gas degreasing method. Some parts also need to be cleaned with gasoline, but if the final processing method before nitriding is polishing, grinding, polishing, etc., it can produce a surface layer that hinders nitriding, resulting in uneven nitriding layer or bending and other defects after nitriding. At this time, one of the following two methods should be used to remove the surface layer. One method uses gas to remove oil before nitriding. Then use aluminum oxide powder to abrasively clean the surface. The second method is to treat the surface with phosphoric acid film.

Discharge air of nitriding furnace

Put the parts to be treated in the nitriding furnace, and heat them after sealing the furnace cover, but exhaust air in the furnace before heating to 150 ℃.

The main function of discharging the furnace is to prevent explosive gas from coming into contact with air during ammonia decomposition, and to prevent the surface oxidation of the treated objects and supports. The gas used includes ammonia and nitrogen. The key points for removing the air in the furnace by nitriding cast iron are as follows:

① After the parts to be treated are installed, the furnace cover shall be sealed, and anhydrous ammonia shall be introduced with as much flow as possible.

② Set the automatic temperature control of the heating furnace at 150 ℃ and start heating (note that the furnace temperature cannot be higher than 150 ℃).

③ When the air in the furnace is discharged to less than 10%, or the discharged gas contains more than 90% NH3, the furnace temperature is raised to the nitriding temperature.

Decomposition rate of ammonia

Nitriding is carried out by spreading other alloy elements in contact with the primary nitrogen, but the primary nitrogen is generated, that is, because the steel itself becomes a catalyst when the ammonia gas contacts the heating steel, which promotes the decomposition of ammonia. Although automobile die nitriding can be carried out under ammonia gas with various decomposition rates, the decomposition rate of 15-30% is generally adopted, and the nitriding shall be maintained for at least 4-10 hours according to the required thickness of nitriding, and the treatment temperature shall be maintained at about 520 ℃. Most industrial nitriding furnaces for cooling are equipped with heat exchangers to rapidly cool the heating furnace and parts to be treated after nitriding. That is, after nitriding, turn off the heating power supply to reduce the furnace temperature by about 50 ℃, and then double the ammonia flow before starting the heat exchanger. At this time, observe whether there is bubble overflow in the glass bottle connected to the exhaust pipe to confirm the positive pressure in the furnace. After the ammonia introduced into the furnace is stabilized, the ammonia flow can be reduced until the positive pressure in the furnace is maintained. When the furnace temperature drops below 150 ℃, the method of removing gas in the furnace described above shall be used, and the furnace cover can be opened only after air or nitrogen is introduced.

The above is the relevant content introduced to you by the well type carburizing furnace, and I hope it will be helpful to you.