Characteristics of metal powder injection molding technology

Characteristics of metal powder injection molding technology

Metal powder injection molding technology is a new powder metallurgy near-net forming technology that introduces modern plastic injection molding technology into the field of powder metallurgy. The basic process is: first mix the solid powder and the organic binder evenly, then inject it into the mold cavity by the injection molding machine after heating and plasticizing (~150 ℃), then remove the binder in the molding blank through chemical or thermal decomposition, and then sinter and compact the molding. Compared with the traditional process, it has the characteristics of high precision, uniform organization, excellent performance and low production cost. Its products are widely used in electronic information engineering, biomedical equipment, office equipment, automobiles, machinery, hardware, sports equipment, clock industry, weapons, aerospace and other industrial fields.

Metal powder injection molding technology is a product that combines plastic molding technology, polymer chemistry, powder metallurgy technology, metal material science and other disciplines through and across. It uses mold injection molding blank and rapidly manufactures high-density, high-precision, three-dimensional complex shape structural parts through sintering. Quickly and accurately convert the design concept into products with certain structural and functional characteristics, and directly produce parts in batches. This process not only has the advantages of less traditional P/M process flow, no cutting or less cutting, and high economic efficiency, but also overcomes the disadvantages of traditional P/M process products such as uneven material, low mechanical properties, difficult to form thin wall, and complex structure, especially suitable for batch production of small metal parts, with complex structure and special requirements.

The metal powder and organic adhesive are uniformly mixed together to make various raw materials into injection molding mixture. The uniformity of the mixture directly affects its fluidity, and then affects the injection molding process parameters, as well as the density and other properties of the material. The injection molding process in this step is the same as the plastic injection molding process in principle, and its equipment conditions are basically the same. In the process of injection molding, the mixture is heated into plastic materials with rheological properties in the barrel of the injection molding machine, and then injected into the mold at an appropriate injection pressure to form a blank. The injection molding blank shall be uniformly organized to make the product shrink evenly during sintering. Before sintering, the organic adhesive contained in the forming blank must be removed. This process is called extraction. The extraction process must ensure that the adhesive is gradually discharged from different parts of the blank along the micro-channel between the pellets without reducing the strength of the blank. The removal rate of binder generally follows the diffusion equation. Sintering can make the porous degreased blank shrink and compact, and become a product with certain structure and performance. Although the properties of products before sintering are related to many process factors, in many cases, the sintering process has a great or even decisive impact on the microstructure and properties of products.