Degreasing is a process in which the binder in the preform can be completely removed by using appropriate methods. There are two basic methods for degreasing: solvent extraction and thermal decomposition. The most important index to evaluate various degreasing technologies is degreasing time. In addition, if the formation of liquid phase can be avoided during degreasing, the deformation of green billets can be effectively controlled to ensure the dimensional accuracy after sintering.

In the whole MIM process, batching and mixing, injection molding, degreasing and sintering, the degreasing process is the most difficult and critical factor in PIM process, which is time-consuming, defective and difficult to control, and is still the bottleneck of PIM industry development.

Why Degrease?

Degreasing is used to remove the lubricants and binders that must be adjusted during powder injection molding, such as stearic acid, zinc stearate, lithium stearate, paraffin wax, resin, etc. At the same time, the lubricant or binder shall be completely evaporated to remove without damaging the compact and invading the sintering belt or furnace. Because the binder will cause defects such as parts cracking under high temperature, before sintering, parts need to be degreased. There are three types of degreasing: solvent degreasing, catalytic degreasing and thermal degreasing. The main purpose is to remove the low melting point binder and stabilize the quality of sintered products.

Common degreasing methods: 1) Solvent degreasing: mainly for wax based feed, the removal ratio of adhesive is generally 50-60% by weight. The process of solvent degreasing is complex, the production cycle is long, and the degreasing products are deformed.

2) Thermal degreasing: both wax based and plastic based feeds can be used, and the removal ratio of adhesive is generally above 95%, which has a certain pre sintering effect. The thermal degreasing process is slow in degreasing speed, easy to produce defects, and only suitable for small pieces;

3) Catalytic degreasing: mainly for plastic based feed, the removal ratio of adhesive is generally about 90%. It combines the advantages of thermal degreasing and solvent degreasing, and overcomes the disadvantages of traditional degreasing methods, such as long time, many defects, high energy consumption, environmental pollution, etc. It is considered as one of the current advanced degreasing processes.

Lianyungang Fuchi Intelligent Manufacturing Technology Co., Ltd. has a catalytic degreasing furnace. The catalytic degreasing furnace can slowly heat the temperature. The heating temperature is lower than the sintering temperature. Generally, 600 ℃ organic matter can volatilize. Some organics can be recycled and do not need to be ignited, and the ignition of organics will pollute the environment. The protective atmosphere discharged from the tail of the continuous sintering furnace should be ignited, which is why the open fire of the continuous sintering furnace is seen. When the powder is heated below the component melting point temperature, it can bond with each other without relying on the binder.