What are the powder metallurgy molding technologies

What are the powder metallurgy molding technologies

Powder metallurgy is an advanced manufacturing technology integrating material preparation and part forming, which is energy-saving, material saving, efficient, final forming and less pollution. It has an irreplaceable position and role in the material and part manufacturing industry, and has entered the development frontier of contemporary material science. At present, powder metallurgy technology is developing in the direction of high density, high performance and low cost

New powder metallurgy forming technologies include warm compaction technology, flow warm compaction technology, die wall lubrication technology, high-speed compaction technology, etc

Warm compaction technique

Warm compaction technology is a new technology developed in the field of powder metallurgy in recent years. It can produce high density and high strength, and has a very broad application prospect

The so-called warm compaction technology is a technology that uses a special powder heating, powder conveying and mold heating system to heat the prealloyed powder and mold with special lubricant to 130~150 ℃, control the temperature fluctuation within ± 25 ℃, and then press and sinter the same as the traditional powder metallurgy process to produce powder metallurgy parts

Technical key: warm compaction powder preparation+warm compaction system

Technical advantages: the warm pressing process has low pressing pressure and small demoulding force, and at the same time, the parts have uniform performance, high product accuracy, high material utilization rate, simple process and low cost

Flow warm compaction technology

Warm Flow Compaction (WFC) is a new near net forming technology for powder metallurgy parts, which is based on the powder compaction and warm compaction process and combines the advantages of metal powder injection molding process. Its key technology is to improve the fluidity of mixed powder By improving the fluidity, filling capacity and formability of mixed powder, it can accurately form parts with complex geometric shapes on traditional presses at 80~130 ℃, such as parts with grooves, holes and threaded holes perpendicular to the pressing direction, without the need for subsequent secondary machining

Key technology: WFC technology is still in the initial stage of research abroad, and its key manufacturing technology and densification mechanism have not been reported yet

Technical advantages: it can form parts with complex geometry, with high density and uniform density, good adaptability to materials, simple process and low cost

Membrane wall lubrication technology

During the forming of traditional powder parts, in order to reduce the friction between powder particles and between powder particles and die wall, a certain amount of lubricant needs to be added to the powder mixture, but the mixed lubricant is not conducive to obtaining high-density powder metallurgy parts due to its low density; Moreover, the sintering of lubricant will pollute the environment, even reduce the life of sintering furnace and the performance of products. The application of mold wall lubrication technology has solved this problem well In recent years, using die wall lubrication instead of powder lubrication has become another hot spot in powder forming research and development

Technical key: realize mold wall lubrication

Technical advantages: obviously improve the green density of powder materials and the green strength of powder materials

High speed pressing technology

The process of high-speed pressing parts is the same as that of traditional pressing process The mixed powder is added into the feeding hopper, and the powder is automatically filled into the mold cavity through the powder feeding shoe for compaction. After that, the parts are ejected and transferred to the sintering process. The difference is that the compaction speed of high-speed compaction and the speed of the hammer head of the press are much higher than that of traditional compaction

Technical key: heavy hydraulic hammer, high pressure braking speed

Technical advantages: HVC technology has the characteristics of high density, high performance, low cost, high productivity and can form large parts

Dynamic magnetic compaction technology

DMC uses the pressure exerted by pulse modulated electromagnetic field to consolidate the powder Like the traditional powder metallurgy pressing process, dynamic magnetic pressing is also a two-dimensional pressing process, but it is a radial pressing rather than an axial pressing process When the powder is put into a conductive container (sheath) and placed in the central cavity with high field strength, the coil is connected with a high current pulse, a magnetic field is formed in the coil, and induced current is generated in the sheath The induced current interacts with the applied magnetic field to produce the magnetic force that compresses the sheath from the outside to the inside, so that the powder can be pressed. The whole pressing process time is less than 1ms

Technical key: two-dimensional radial suppression, electromagnetic field pressure

Technical advantages: It can achieve higher pressing force, lower maintenance and production costs. It can apply pressure in any temperature and atmosphere, and is suitable for all materials. The working conditions are more flexible. No lubricant or binder is used, which is conducive to environmental protection

Spark plasma sintering technology

This technology integrates powder forming and sintering, without pre forming, additives and adhesives It mainly uses the electric field formed by the external pulse strong current to remove the oxides and adsorbed gases on the powder particle surface, purify the materials, activate the powder surface, improve the diffusion ability of the powder surface, and then uses the strong current to heat the powder for a short time under low mechanical pressure for sintering densification

Key technology: combining powder forming and sintering

Technical advantages: the sintering temperature of the powder is reduced, the sintering time is shortened, and the heating effect of the powder itself is fully utilized. The thermal efficiency is extremely high, and the heating is uniform. Parts with high precision, homogeneity, compactness, low oxygen content, and fine grain structure can be obtained through one-time forming

Explosive suppression technology

The metal powder material is usually placed in a mold with a certain structure to apply explosive pressure. The chemical energy of the explosive substance is converted into a high-pressure shock wave in the surrounding medium in a very short time, and acts on the powder in the form of a pulse wave to obtain high density

Technical key: violent explosion+high-speed suppression

Technical advantages: It can make loose materials reach theoretical density Materials unsuitable for traditional pressure processing can be made into parts, and traditional incompressible cermet materials and low ductility metals can be made into composite materials by pressing

Powder metallurgy is an important part forming technology The continuous emergence of new technologies and processes in powder metallurgy will certainly promote the rapid development of high-tech industries and bring bright prospects to material engineering and manufacturing technology