The final process of bearings and other wear-resistant materials made by traditional powder metallurgy is oil immersed. MIM products, such as electronic parts, they are finished after injection molding, sintering process, and surface finished. So many people who work in MIM process, are not familiar with oil immersion. For most products no need soaking oil, but for some special porous friction reduction products, oil immersion is a very important step after sintering.

MIM is one technology of Powder Metallurgy, but many powder metallurgy theories and methods can be used to MIM products. Oil immersion can not only increase the corrosion resistance of MIM products to improve their wear-resistance, for some porous bearing material, it can also have automatic oil supply characteristics, and reduce the lubricate maintenance times in usual, so as to extend the service life.

The principle why oil immersion can improve the performance of the is, under a certain condition, the lubricating oil goes into MIM products. The oil-soaked products will be rubbed in the post working environment. Their surface temperature will rise when rubbed. Then, the oil within the pores s will expanse, and the oil will pore out of from the apertures become the automatic oil supply. And this automatic oil film can play the role of lubrication friction.
For immerse oil on the sintered products, first we need to clean up the products surface. There are three ways for MIM products oil immersion.

Put the clean sintered products into the vacuum box, close the vacuum box to keep the sealed state. Then, turn on the vacuum device to achieve a real vacuum state, and input oil into the vacuum box through the special pipe. The next step, heat the box to 80 degrees Celsius for twenty to thirty minutes. Because the air in the product's interconnected pores is drawn out, the oil can be immersed in the product within ten minutes. This method has high working rate and high speed.

Second, the hot oil method

Heat the oil to eighty to one hundred and twenty degrees Celsius, then put the clean sintered products into the hot oil for an hour. The principle is that due to the products get heated by hot oil. The air in its tissue pores expanses due to heating, so a part of the air is driven away. As the oil cools, the product cools accordingly and the remaining air in the pores cools and shrinks, drawing oil into the pores. The hot oil has better fluidity than the cold oil, and the smoothness is high, so the oil quantity entering the products is large, and this method has the characteristics of high oil immersion efficiency.

Third, ordinary oil immersion

Put the sintered clean products into the room temperature oil soaking. The oil is immersed into the pores of the products under the effect of capillary force. This method has low power, long soaking time which usually take several hours, used in the products which have low oil content. But it is economical and requires no special oil-immersed equipment and oil heating.

The above three commonly oil immersion methods have different oil rate and efficiency. Different MIM manufacturers should choose the proper way based on different parts oil requirements of oil products. We believe that with the development of science and technology, more and more new oil immersion method will appears. Since then, the effect of oil immersion for product performance will be greatly increased.