Powder metallurgy knowledge

Powder metallurgy is preparing metal or metal powder (or the mixture of metal powder and nonmetal powder) as raw material, after forming and sintering, manufacturing metal materials, composite and technology of all kinds of products. Powder metallurgy method and has a similar place in ceramic production, therefore, a series of powder metallurgy new technology also can be used for the preparation of ceramic materials. Due to the advantages of powder metallurgy technology, it has become the key to solve the problem of new materials, in the development of new materials play an important role.

Powder metallurgy and development prospect.

Powder metallurgy industry in China has been nearly 10 years of rapid development, but China and abroad the gap still exist the following aspects: (1) enterprises, small scale and economic benefit vary widely with foreign enterprises. (2) the product cross, interacting each other enterprises, competition is fierce. (3) most enterprises lack of technical support, research and development ability, low product class, difficult to compete with foreign. (4) lack of and the problems. Add (5) process equipment and supporting facilities behind. Less (6) products export, trade channels.

Along with our country after joining the WTO, will improve the above shortcomings and weaknesses, this is because after joining the WTO, market internationalization gradually, powder metallurgy market will further expand opportunity; At the same time after the introduction of foreign capital and technology of powder metallurgy and related technical level will improve and development.

Second, the characteristics of the

Powder metallurgy with unique chemical composition and mechanical and physical properties, and these performance made with the traditional casting method can't get. Using powder metallurgy technology can be directly made into porous, half density or fully dense material and products, such as the oil bearing, gear, CAM, guide, cutting tools, etc., is a kind of no less cutting process.

(1) of powder metallurgy technology can minimize alloy composition partial poly, eliminate thick, uneven casting structure. In the preparation of high performance rare-earth permanent magnetic materials, rare earth hydrogen storage materials, rare earth luminescent material, rare earth catalyst, high temperature superconducting materials, new type metal materials (such as Al - Li alloy, heat-resistant Al alloy, super alloy, corrosion resistant stainless steel powder, powder high speed steel, intermetallic compound, high temperature structural materials, etc.) plays an important role.

(2) preparation of amorphous and microcrystalline, quasi crystal, nanocrystalline and super saturation solid solution and a series of high-performance nonequilibrium materials, these materials have excellent electrical, magnetic, optical, and mechanical properties.

(3) you can easily achieve a variety of types of composite, give full play to the respective features of every material, is a kind of low-cost production of high-performance metal and ceramic composite material technology.

(4) can produce ordinary smelting method cannot production with special structure and properties of materials and products, such as new porous biological material, porous membrane material, high performance structure ceramics abrasive material and functional ceramics, etc.

(5) can realize near net forming and automatic batch production, thus, can effectively reduce the production of resources and energy consumption.

(6) can make full use of ore, tailings, steelmaking sludge, rolled steel and iron scale as raw materials, recycling scrap metal, is a kind of material is effective for regeneration and comprehensive utilization of new technology.

Our common machining cutting tools, hardware tools, a lot is made of powder metallurgy technology.

Three, the powder metallurgy production process

(1) production powder. Powder production process includes steps of preparing powder, powder mixing. For improving the formability and plasticity often join powder gas, such as rubber or paraffin plasticizer.

(2) pressure molding. Powder in 500 ~ 600 mpa pressure, pressure into required shape. [1]

(3) the sintering. In high temperature furnace and vacuum furnace protective atmosphere. Sintering is different from the metal melting, is still in the solid state sintering at a rare elements. Powder sintering process between particles by diffusion, recrystallization, welding, chemical combination, dissolution and so on a series of physical and chemical process, become has certain porosity of metallurgical products.

(4) post-processing. In general, good sintering parts can be used directly. But for a certain size require high precision and high hardness, wear resistance of sintering processing parts. Post-processing including pressing, rolling, extrusion, hardening, surface quenching, oiled, and melt infiltration, etc.

Four, the application and classification of powder metallurgy materials

(1) application: automobile, motorcycle, textile machinery, industrial sewing machines, electric tools, hardware tools. Electrical appliances. Mechanical engineering) and so on all kinds of powder metallurgy parts (iron and copper base). [2]

(2) categories: porous materials, low friction metallurgical powder material, powder metallurgy friction metallurgical powder material, metallurgical powder structure parts, powder metallurgy tooling materials, and electromagnetic metallurgical powder material, and high temperature metallurgical powder material etc.

Powder metallurgy products application range is very wide, from general machinery manufacturing to precision instruments; From hardware tools to large machinery; From the electronic industry to the motor manufacturing; From civilian industry to military industry; From the more general to the sophisticated high technology, all can see the figure of powder metallurgy process.

Five, powder metallurgy process and performance

Isostatic pressing molding powder metallurgy

Metal injection molding of powder metallurgy

Powder forging of powder metallurgy

Pressure sintering of powder metallurgy

Powder properties (property of powder)

The floorboard of the powder all performance. It includes: the powder of the geometric properties (particle size, specific surface, pore size and shape, etc.); Chemical properties of the powder (chemical composition, purity, oxygen content and acid insoluble substance, etc.); Powder on the mechanical properties, apparent density, mobility, formability, compressibility, accumulation Angle and shearing Angle, etc.); Powder physical properties and surface characteristics (true density, gloss, wave absorption, surface activity, ze % 26 ndash; ta (% 26 ccedil; electric potential and magnetism, etc.). Powder performance often largely determine the performance of powder metallurgy products.

Is the most basic geometric properties of powder particle size and shape.

(1) the particle size. It affect the processing and forming, powder sintering shrinkage and final properties of the product. Some properties of powder metallurgy products almost directly related and granularity, for example, the filter material of filtering precision on the experience can be obtained by the original powder particle size divided by the average 10; Carbide product performance and the grain size of wc phase has much to do, to get a finer grain size of hard alloy, but using a finer grained wc material is possible. Powder used in the production practice, the particle size range from several hundred nanometers to hundreds of micrometers. Particle size is smaller, the activity, the greater the surface the easier it is to oxidation and the water absorption. When small to hundreds of nanometer powder storage and transport is not very easy, but when small to a certain degree of quantum effects began to work, its physical properties will happen great changes, such as ferromagnetic powder will become a super paramagnetic, melting point decrease with the decrease of the size as well.

(2) the powder particle shape. It depends on the pulverizing method, such as electrolytic method, powder, granule in dendritic; Reduction method, the iron powder particles show sponge shape; Gas atomization is essentially spherical powder. In addition, some are egg powder, disk, pin, onion, etc. Powder particle shape affects the powder mobility and apparent density, due to the mechanical engagement between particles, irregular powder compacting intensity is too big, especially the dendritic powder blocking its pressure intensity is the largest. But for porous materials, adopting the spherical powder is best.

Mechanical properties of powder and mechanical properties of powder process performance, it is the important process parameters of powder metallurgy forming technology. When the apparent density of the powder was pressed by the volumetric method of weighing basis; Powder liquidity determines the powder of die filling speed and pressure machine production capacity; Powder compressibility decided to suppress process difficulty and pressure of the high and low; And the formability of the powder is decided to the strength of the billet.

Chemical performance mainly depends on the chemical purity of raw materials and coal pulverizing method. Higher oxygen content will reduce the strength of suppression performance, compact and mechanical properties of sintered products, so powder metallurgy are for most of the technical conditions have a certain rules. Powder, for example, the permission of the oxygen content is 0.2% ~ 0.2%, this is equivalent to the oxide content of 1% ~ 1%.

Six, powder metallurgy industry development prospects

In recent years, through continuous introduction of foreign advanced technology combined with independent development and innovation, powder metallurgy industry and technology in China are shows a tendency of rapid development, is China's mechanical generic components industry, one of the fastest growing industry in powder metallurgy industry of the nation's output each year to increasing at the rate of 35%.

Global manufacturing is accelerating shift to China, automobile industry, machinery manufacturing, metal industry, aerospace, instrumentation, hardware tools, construction machinery, electronic appliances and the rapid development of high-tech industries, for the powder metallurgy industry has brought the rare development opportunity and huge market space. In addition, the powder metallurgy industry are listed in priority to the development of China and encourage foreign investment projects, the development prospect.

(5) can realize near net forming and automatic batch production, thus, can effectively reduce the production of resources and energy consumption.