furnace manufacturers to introduce the nitriding furnace parts before the surface cleaning process:
An overview of nitriding treatment
Nitriding refers to a chemical heat treatment process in which nitrogen atoms are permeated into the surface of a workpiece in a certain medium at a certain temperature. The nitriding products have the characteristics of excellent wear resistance, fatigue resistance, corrosion resistance and high temperature resistance.
Before nitriding parts surface cleaning
For most parts, nitriding can be done immediately after oil removal by gas removal. Some parts also need to be cleaned with gasoline better, but in the last processing method before nitriding if the use of polishing, grinding, polishing, etc., that may hinder nitriding surface layer, resulting in nitriding, nitriding layer uneven or bending defects. It is advisable to use one of the following two methods to remove the surface layer. A method of first removing oil with gas before nitriding. Then, aluminum oxide powder was used to sand the surface. The second method is to treat the surface with phosphoric acid skin film.
The removal of air from the nitriding furnace
The parts to be treated are placed in the nitriding furnace, and the furnace cover can be heated after sealing, but before heating to 150℃ must be done in the furnace to remove air.
The main function of the elimination furnace is to prevent ammonia decomposition with air contact and explosive gas, and to prevent the surface of the treatment and support oxidation. The gases used are ammonia and nitrogen. The main points of iron nitriding to remove the air in furnace are as follows:
(1) be processed parts installed after the furnace cover sealed, began to pass anhydrous ammonia, its flow as much as possible.
Set the automatic temperature control of the heating furnace at 150℃ and start heating (note that the furnace temperature should not be higher than 150℃).
When the air in the furnace is removed to less than 10%, or when the gas discharged contains more than 90% NH3, the furnace temperature is raised to the nitriding temperature.
Decomposition rate of ammonia
Nitriding is the process of laying and other alloying elements in contact with the primary nitrogen, but the primary nitrogen is produced because the steel material itself becomes the catalyst when the ammonia gas comes into contact with the steel material in heating and promotes the ammonia decomposition. Although the car mold nitriding in a variety of decomposition rate of ammonia, can be nitriding, but generally are used in the decomposition rate of 15 ~ 30%, and according to the thickness of nitriding required to maintain at least 4 ~ 10 hours, the treatment temperature is maintained at about 520℃. Cooling most industrial nitriding furnaces are equipped with a heat exchanger to rapidly cool the heating furnace and the treated parts after nitriding is completed. That is, after the completion of nitriding, turn off the heating power to reduce the furnace temperature by about 50℃, and then double the ammonia flow to start the heat exchange. At this time, it is necessary to observe the glass bottle connected to the exhaust pipe, whether there are bubbles overflow, in order to confirm the positive pressure in the furnace. After waiting for ammonia stabilization in the furnace, the ammonia flow rate can be reduced to maintain the positive pressure in the furnace. When the furnace temperature drops below 150℃, the furnace cover can be opened after the above mentioned method of removing the gas in the furnace is used and air or nitrogen is introduced.
Above is the well carburizing furnace to introduce the relevant content, I hope to help you.
On 2018-08-08 11:45:46
