Metal injection molding (MIM) is a new powder metallurgy near-net molding technology originated in the plastic injection molding industry. As we all know, plastic injection moulding technology produces various complex shapes at a low cost, but the strength of plastic products is not high. Metal or ceramic powder can be added to plastic to improve its performance, resulting in higher power and wear resistance. This concept has evolved in recent years to maximize solid particles' content, remove the binder, and densify the compact during the subsequent sintering process. This new powder metallurgy moulding method is called metal injection molding. The metal injection molding atmosphere types are as follows.
Metal injection moulding's protective atmosphere is divided into reducing atmosphere and neutral atmosphere, and the reducing atmosphere is further divided into hydrogen and decomposing ammonia. The primary function of the protective atmosphere during the sintering process is to protect the sintered product from oxidation. Under certain temperature conditions, hydrogen has high permeability and is a chemically active, flammable, non-toxic gas. It's frequently used as a protective atmosphere during the sintering of refractory powder metallurgy products like tungsten, cemented carbide, and stainless steel.
This type of atmosphere is divided into exothermic type (no need to supply heat from the outside) and endothermic type atmosphere (need to supply heat from the outside), both of which are converted from hydrocarbons. The exothermic type can be used to control the carbon content of powder metallurgy sintered products (including meatl injection molding). It is divided into two types of atmospheres: light and dense. The light exothermic atmosphere has a shallow carbon potential. It is used to make low carbon steel and copper. It is only used for non-oxidation heating during sintering; the carbon potential of the concentrated exothermic atmosphere is higher, which can be used to prevent oxidation of powder metallurgy iron- and copper-based parts and reduce decarburization of iron-based parts.
The sintering atmosphere of metal injection molding is mainly through a certain air gas in the sintering furnace. It can also be regarded as sintering under normal pressure and is generally used in sintered products of metal composite materials and ceramic materials. From the perspective of manufacturing mechanical parts, a new process with less cutting and no cutting when manufacturing mechanical parts by metal injection molding can greatly reduce the amount of machining, save metal materials, and improve labor productivity.
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