Characteristics And Process Flow Of Metal Powder Technology

Metal powder injection molding technology is a product that integrates multiple disciplines such as plastic molding technology, polymer chemistry, powder metallurgy technology, and metal materials science. By using molds to inject molded billets and rapidly manufacture high-density, high-precision, and three-dimensional complex shaped structural parts through sintering, design ideas can be quickly and accurately materialized into products with certain structural and functional characteristics, and parts can be directly mass-produced. It is a new revolution in the manufacturing technology industry.

This process technology not only has the advantages of fewer conventional powder metallurgy processes, no or less cutting, and high economic benefits, but also overcomes the shortcomings of traditional powder metallurgy products, such as uneven materials, low mechanical properties, difficulty in forming thin-walled and complex structures. It is particularly suitable for mass production of small, complex, and metal parts with special requirements. Process flow: binder - mixing - injection molding - degreasing - sintering - post-treatment.
Powder metal powder
The particle size of metal powder used in MIM process is generally between 0.5 and 20 μ M; In theory, the finer the particle, the larger the specific surface area, making it easier to shape and sinter. However, traditional powder metallurgy processes use materials larger than 40 μ Coarse powder of m.
Organic adhesive
The function of organic adhesive is to bond metal powder particles, making the mixture rheological and lubricating when heated in the injection machine barrel, which is the carrier that drives the flow of powder. Therefore, the choice of binder is the carrier of the entire powder. Therefore, the principle of adhesion is the key to the entire powder injection molding. Requirements for organic binders:
1. The amount used is small, and using fewer binders can produce better rheological properties of the mixture;
2. No reaction, no chemical reaction with metal powder during the removal of adhesive;
3. Easy to remove, without residual carbon in the product.
Mixing materials
Mix metal powder and organic binder evenly to make various raw materials into injection molding mixtures. The uniformity of the mixture directly affects its fluidity, thus affecting the injection molding process parameters, as well as the density and other properties of the final material. The process of injection molding in this step is consistent with the process of plastic injection molding in principle, and its equipment conditions are also basically the same. During the injection molding process, the mixture is heated into a plastic material with rheological properties inside the injection machine barrel, and injected into the grinding tool at an appropriate injection pressure to form a blank. The microstructure of the injection molded blank should be uniform and consistent, so that the product shrinks uniformly during the sintering process.
extraction
Before sintering, the organic binder contained in the formed blank must be removed, and this process is called extraction. The extraction process must ensure that the binder is gradually removed from different parts of the blank along the small channels between particles, without reducing the strength of the blank. The removal rate of binders generally follows the diffusion equation. Sintering can cause porous degreased blanks to shrink and densify into products with a certain structure and properties. Although the performance of the product is related to many process factors before sintering, in many cases, the sintering process has a significant and even decisive impact on the microstructure and properties of the final product.
Post processing
For parts with relatively precise size requirements, necessary post-processing is required. This process is the same as the heat treatment process for conventional metal products.