Process characteristics of metal powder injection molding technology

Nov 29, 2022

Metal powder injection molding technology is based on the penetration and intersection of plastic molding technology, polymer chemistry, powder metallurgy technology, metal materials and other disciplines. The mold can be used to inject blank parts, and rapidly manufacture high-density, high-precision, three-dimensional complex structural parts through sintering. It can quickly and accurately materialize design ideas into products with certain structural and functional characteristics, and can directly produce parts in batches. This is a new change in the manufacturing technology industry. The following is a brief introduction to the process characteristics of metal powder technology by Zhongwei Precision Manufacturer:

1、 Powder metal powder: the particle size of metal powder in the process of metal injection molding is generally 0.5~20 μ m; In theory, the finer the particles are, the larger the specific surface area is, which is easy to form and sinter. However, traditional powder metallurgy processes use more than 40 μ M of coarse powder.

2、 Organic adhesive: The function of organic adhesive is to bond metal powder particles, so that the mixture is heated in the barrel of the injection molding machine to have rheological properties and lubricity, that is, the carrier that drives the powder flow. Therefore, the choice of binder is the carrier of the whole powder. Therefore, the bonding principle is the key to the whole powder injection molding. Requirements for organic adhesives:

powder metallurgy

1. Small dosage and less binder can produce better rheological properties;

2. No reaction or chemical reaction with metal powder occurs in the process of removing adhesive;

3. It is easy to remove and there is no carbon residue in the product.

3、 Mixing: the metal powder and the organic adhesive are uniformly mixed together to make a mixture for injection molding. The homogeneity of the mixture directly affects its fluidity, thereby affecting the injection molding process parameters, the density and other properties of the final material. In principle, this injection molding process is consistent with the plastic injection molding process, and the equipment conditions are basically the same. In the injection molding process, the mixture is heated into a plastic material with rheological properties in the barrel of the injection molding machine, and is injected into the abrasive tool to form a blank under an appropriate injection pressure. The microstructure of injection molded blanks should be uniform, so that the products can shrink uniformly during sintering

4、 Extraction: Before sintering, the organic binder in the preform must be removed. This process is called extraction. The extraction process must ensure that the adhesive is gradually removed from different parts of the blank along the micro channels between the particles without reducing the strength of the blank. The removal rate of adhesive usually follows the diffusion equation. The porous degreased green body can be shrunk and densified into products with certain structure and properties by sintering. Although the properties of products are related to many process factors before sintering, in many cases, the sintering process has a great or even decisive influence on the microstructure and properties of the final products.

Now you know what the process characteristics of metal powder technology are! This process technology not only has the advantages of less traditional powder metallurgy process flow, no cutting or less cutting, and high economic benefits, but also overcomes the shortcomings of traditional powder metallurgy process products such as uneven materials, low mechanical properties, and difficult forming of thin-walled and complex structures. It is especially suitable for large-scale production of small, complex and metal parts with special requirements. Technological process: adhesive - mixing - injection molding - degreasing - sintering - post-treatment.