Metal injection molding technology is the introduction of modern plastic injection molding technology into the field of powder metallurgy and the formation of a new type of metal powder metallurgy near-net shape technology. Although the plastic injection molding technology can produce a variety of complex shapes of products at a low price, but the strength of plastic products is not high, in order to improve its performance, can be added to the plastic metal or ceramic powder in order to get a higher strength, good wear resistance products. In recent years, this novel method of operation has evolved to maximize the content of solid particles and to completely remove the binder and densify the forming blanks during the subsequent sintering process. This new method of powder metallurgical forming is known as metal injection molding.

First of all, metal powder injection molding is a solid powder and organic binder uniform mixing, after granulation in the state of heating plasticization injection molding machine injection molding cavity solidification, and then chemical or thermal decomposition of the molding billet in the binder removed, and finally by the sintering densification to get the final product.

In metal powder injection molding degreasing methods are: thermal decomposition, solvent degreasing, catalytic degreasing and so on. Among them, the products produced after catalytic degreasing have higher dimensional accuracy, and Harber Metal adopts catalytic degreasing.

Taking POM binder as an example, the degreasing process is divided into three stages: pre-rinsing, degreasing and post-rinsing.

Pre-rinsing stage: Because the degreasing product of metal powder injection molding raw embryo will react with oxygen, so before degreasing, we need to dilute the air inside the furnace chamber, so that the internal oxygen content reaches a safe value. In the pre-flushing stage, the heating of the furnace chamber, flue and nitrogen pipeline will be carried out, and at the same time, the furnace fan will be activated to deliver nitrogen into the furnace.

Degreasing stage: This refers to the process of decomposing the binder (paraformaldehyde) in the raw embryo into formaldehyde in the degreasing furnace at a set temperature. The furnace is in a holding state, and the nitric acid pump is activated to inject nitric acid into the furnace, which accelerates the decomposition reaction rate of paraformaldehyde in an acidic atmosphere.

After flushing stage: after the end of the degreasing stage, nitrogen began to fill the furnace chamber, the furnace after degreasing stage of formaldehyde as well as nitric acid through the heating tube discharge. Formaldehyde and nitric acid will be heated and burned in the tube, and finally discharged to the outside world only carbon dioxide, water vapor and nitrogen dioxide gas, which are composed of air gas, in line with environmental requirements.

After catalytic degreasing of metal powder injection molding raw embryo degreasing rate of up to 90%, into gray blank, the next stage is to enter the sintering furnace for sintering.

Powder metallurgy parts in the casting process of the surface layer is detailed and internal roughness porous. In the degreasing process should not use strong acid and alkaline degreasing agent. It is better to use neutral degreasing agent or weak alkaline degreasing agent, and the degreasing time is as short as possible. In order to improve the degreasing speed, the content and temperature of degreasing liquid can be increased. It is better to use ultrasonic cleaning in order to clean thoroughly. For example: sodium pyrophosphate 30g / L LT83 additive 10-20mL / L.