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PM method

Metallurgical terminology
synonym Powder metallurgy (Powder metallurgy method) generally refers to PM method
conventional Powder metallurgy PM method for short, namely, uniaxial rigid die pressing forming method, is a widely used method in the current powder metallurgy industry, belonging to powder metallurgy Metal powder forming methods in industry, other methods include metal injection molding (MIM), powder forging (P/F), hot isostatic pressing (HIP), cold isostatic pressing (CIP).
Chinese name
Powder metallurgy
Foreign name
powder metallurgy
Abbreviation
PM method

Basic process

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1. Preparation of raw material powder. The existing pulverizing methods can be roughly divided into two categories: mechanical method and physical chemical method. The mechanical method can be divided into: mechanical crushing and atomization; Physicochemical method can be divided into electrochemical corrosion method, reduction method, chemical method, reduction chemical method Vapor deposition method , liquid deposition and electrolysis. Among them, reduction method, atomization method and Electrolytic method
2. The powder is formed into a green block of the desired shape. The purpose of forming is to make the compact with certain shape and size, and make it have certain density and strength. The forming methods are basically divided into pressure forming and non pressure forming. The most widely used in pressure forming is Compression Molding
3. Sintering of billets. Sintering is powder metallurgy Key processes in the process. The formed compact is sintered to obtain the required final physical and mechanical properties. Sintering can be divided into unit system sintering and multi system sintering. For the solid state sintering of unit system and element system, the sintering temperature is lower than the melting point of the metal and alloy used; For liquid phase sintering of multi-component systems, the sintering temperature is generally lower than the melting point of the refractory component, but higher than the melting point of the fusible component. In addition to ordinary sintering, there are also special sintering processes such as loose sintering, melt leaching and hot pressing.
4. Post processing of products. The treatment after sintering can be carried out in various ways according to different product requirements. Such as finishing, oil immersion, machining, heat treatment and electroplating. In addition, in recent years, some new processes such as rolling and forging have also been applied to Powder metallurgy material The processing after sintering has achieved ideal results.

advantage

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1. Most refractory metals and their compounds, false alloys and porous materials can only be used Powder metallurgy method To manufacture.
2. Because the powder metallurgy method can be pressed into the final size of the compact, without or little need for subsequent machining, it can greatly save metal and reduce product costs. When powder metallurgy is used to manufacture products, the metal loss is only 1-5%, while when general casting is used, the metal loss may reach 80%.
3. Because powder metallurgy The process does not melt materials in the material production process, so it is not afraid of mixing impurities brought by crucibles and deoxidizers. Sintering is generally carried out in vacuum and reducing atmosphere, and it is not afraid of oxidation, nor will it pollute the materials, so it is possible to produce high-purity materials.
4、 Powder metallurgy It can ensure the correctness and uniformity of material composition ratio.
5. Powder metallurgy is suitable for producing many products of the same shape, especially those with high processing costs such as gears. The production cost can be greatly reduced by powder metallurgy.

shortcoming

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1. In case of no batch, the size of parts shall be considered;
2、 mould The cost is relatively higher than the casting mould.

application

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powder metallurgy It is a universal process with a wide range of applications. Many PM parts are installed in various automobile assemblies, such as engine, transmission and chassis. In addition, powder metallurgy is also used in aerospace, agricultural machinery and other fields, as well as in the manufacture of small and large appliances, office machinery, electrical instruments, grassland and garden equipment, locks and hardware parts, medical equipment, cross-country machinery, electric and manual tools, sports products and automatic recording instruments.
powder metallurgy Parts can be surface coated to make them decorative, corrosion resistant or wear-resistant. When parts with precise dimensional tolerance or high strength are required, they can be reshaped or re pressed. Parts that cannot be pressed can be finished by cutting.
Most P/M parts have a mass of no more than 2.2kg, but parts with a mass of less than 1g to 16kg can also be manufactured. [1]

development direction

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1. Representative Iron base alloy , will develop into large volume precision products and high-quality structural parts;
2. Manufacture high-performance alloy with uniform microstructure, difficult to process and completely compact;
3. A special alloy containing mixed phase is produced by strengthening and densification process;
4. Manufacturing heterogeneous materials, amorphous, microcrystalline or metastable alloys;
5. Processing unique and non general shape or composition of composite parts.