Powder metallurgy new technology

Production in anaerobic atmosphere, and contains some of paraffin, which is decomposed into carbon and hydrogen. Of carbon react with iron to form a thin surface layer of carbon. The ductility of the carbon content of the particles is reduced, but increased the sintered on the surface of the activity. Carbon in the powder briquetting, easy to spread to the pellet center and adjacent particles, and therefore do not need to add graphite can be used in the production of powder metallurgy steel.

Swedish IPS steel powder atomized iron powder company annual low oxygen content, its oxygen content was less than (0.015%).

Anaerobic powder for powder metallurgical applications, this permits the use of cheap alloy elements (such as chromium and manganese) instead of nickel and copper. Nickel as a strategic resource, not only expensive, and is a kind of carcinogen, should avoid to use. The powder is also very suitable for pressure with temperature and hot isostatic pressing technology to produce high strength components.

In order to improve the mechanical properties of sintered steel, usually must also to heat treatment after sintering. In order to reduce the production cost, has developed many sintering after hardening heat treatment of material, need not again. Hoeganaes companies in the United States launched a sinter hardening Ancoresteel737SH iron base powder and its hardenability and the compressibility than existing sintering high hardened materials.

2. The powder sinter hardening

Used to sinter hardening powder production don't need to hardening or rarely then quenching and tempering of powder metallurgy parts; In addition to the cost reduction, sinter hardening can provide better tolerance control often caused a certain degree of distortion (quenching and tempering).

The powder can be used in the automotive industry, especially suitable for engine parts, transmission parts and nearly end gear, etc.

Soft magnetic composite material has been widely used at present. They are on the pure iron powder particles coated a layer of oxide or heat curable resin for insulation. In low frequency applications, using coarse particle iron powder mixed with heat curable resin, high permeability and low iron loss of materials. High frequency applications, need more efficient insulation between particles, and particle size to smaller, more  have jiao unable Tang sheen Liang osprey А K  Que glance to share screen Nao  edge na Xue gulls spring like test? / span >, but I don't need high temperature sintering. When the powder grain size increases, the permeability increase, the coercive force is reduced.

2. Soft magnetic metal composite powder preparation

Flame combustion and chemical gas phase method is used to produce nano powder. In this method, the stability of the flat flame is produced by low pressure fuel/oxygen mixture combustion. Chemical matrix with the fuel into the combustion chamber, the flame of the hot spots of rapid thermal decomposition. Stay well due to the combustion chamber surface temperature distribution, gas phase concentration time is short and chemical matrix evenly, and in a very narrow hotspots for thermal decomposition, and thus to produce nano powder particle size distribution of high quality.

3. The flame combustion and chemical gas phase method to produce nano powder

At present, the method has been used in the production of SiO2, TiO2, Al2O3, SnO2, V2O5, ZrO2 oxide nano powder. The nanosize powder production cost is very low, according to the estimated annual output of 100 tons of nanometer powder, nanometer powder will not higher than the cost of $50 per kilogram.

American ordinary mixer, laser reaction with cheap materials, can be fast, cheap and clean production 1 ~ 100 nm silver powder and nickel powder.

4. The laser manufacturing nano powder

Silver nitrate solution with a reducing agent, for example, import the blender, use laser mixture short-term exposure, simultaneously. When laser pulses into liquid form tiny "hot spots", make the reaction of silver nitrate and reducing agent, to generate tiny silver particles. By changing the intensity of laser, agitator speed and reaction, can control the silver powder particle size, particle shape to a certain extent, also can control.

The production speed is 0.5-30 g/min, is higher than other nano powder preparation methods productivity. Reaction materials used in this method does not pollute the environment, and previous hydrazine is a carcinogen used in the production of silver powder. Produced in this way can be used to make silver solder, dental filling, circuit boards, high-speed photography, film, etc.

High power electric pulse to argon protection wire, and the special fields generated by high power pulse constraints. Cylindrical plasma is heated to high temperature above 15000 k, and therefore resistance increase, lead to special field collapse. An explosion caused by metal vapor pressure, shock wave, the formation of metallic aerosol adiabatic cooling fast, nano powder was prepared.

5. Wire electrical explosion preparing nano powder

This method can produce aluminum, nickel, silver, copper, zinc, platinum, molybdenum, titanium, zirconium, indium, tungsten and its alloy powders.

These propellants, explosives, fireworks powder can be used for cement, metal and ceramics, sintering agent, catalyst, synthesis of organometallic compounds, etc.

Australia has developed a mechanized method, can be inexpensive to produce nano metal powder and ceramic powder. It use ball mill to activate chemical reaction, make grain forming superfine nanometer metal or compounds, separation and extraction of fine grain again. Such as mechanical polishing FeCl3, by sodium, calcium, or a mixture of the reduction of iron and aluminum chloride. With appropriate washing method to remove chloride, iron nanoparticles can be got.

6. Mechanization research method in the production of cheap nano powder

This method can successfully produce 10 to 20 nm powder, chemical purity is high, the surface oxide was less than 10% ~ 15%. Also can produce oxide powder, particle size is smaller than 5 nm.

Potential high technology applied: cutting tools, advanced ceramics, catalyst, high density magnetic recording media, magnetic, etc.

American scientists using sound chemical technology and nano metal powder. Sound chemistry is the study of liquid high intensity ultrasound, the formation of tiny bubbles, grew up and broken phenomenon such as introversion subjects.

7. Chemical preparing nanometer metal powder

These ultrasonic bubbles burst, produce strong local heating and forming "hot spots" in the cold liquid, instantaneous temperature is about 5000 ℃, about 1 gpa pressure, duration of about of a second.

Rough and figuratively speaking, these data is equivalent to the sun's surface temperature, the pressure at the bottom of the ocean, lightning. When bubbles burst bubbles metal contained in the volatile compounds are broken down into individual metal atoms, and then gathered for atomic clusters. These clusters containing hundreds of atoms, is about 2 ~ 3 nm in diameter.

These small magnetic metal atom clusters, like a paramagnetic material, composed of clusters of atoms spin magnetic moment, and all the spin in the same direction, and magnetic moment, 100 times higher than ordinary materials. Coating the particles can form stable colloidal iron and particles in a suspended state, always has a "magnetic" industrialized production, used for speakers, magnetic ink, magnetic liquid seal, lubricants, bearings, medical, etc.

Second, the new technology of powder metallurgy forming

Principle: the powder in a conductive container (sheath), placed in a high magnetic field coil in the center of the cavity. Capacitor discharge in a few microseconds access to coil high pulse current, the cavity formed in the magnetic field, coil inside the sheath induced current. Induced current interact with applied magnetic field, magnetic outside-in compress sheath, thus powder is two-dimensional. The whole process is less than 1 ms.

1. The magnetic suppression technology

Dynamic magnetic suppression of advantages:

Because do not use mold, molding die wall friction is reduced to zero, and therefore can achieve higher pressing pressure, to improve products, and production cost is low;

Because at any temperature and atmosphere pressure, and applies to all materials, and therefore more flexible working conditions;

Because the process does not use lubricant and binder, thus forming the product does not contain impurities, high performance, but also conducive to environmental protection.

Many steel alloy powder with a moving magnet suppression experiments, don't add any lubricant powder, green density is above 95%. Dynamic magnetic suppression can be sintered under the condition of the conventional sintering, the mechanical properties is higher than traditional repression. Dynamic magnetic suppression is suitable for manufacturing cylindrical symmetry nearly final shape, thin wall pipe, high aspect ratio of the parts and internal complex shape parts.

Dynamic magnetic suppression has the potential to revolutionise the motor design and manufacturing methods of change, made out of powder materials, a nearly final shape of the stator and rotor, high-performance products, thus greatly reduce the production cost.

Dynamic magnetic suppression is being used to develop high-performance bonded ndfeb magnets and sintered samarium cobalt magnet. Due to the high density magnetic suppression of bonded ndfeb magnets, the magnetic energy product can be increased by 15% - 20%.

Moving magnet to suppress the milliseconds to neutralize process will help to keep the material microscopic structure remains the same, and therefore improve the performance of materials. To hard to suppress, such as W and WC and ceramic powder materials, dynamic magnetic suppression can achieve higher density, thereby reducing the sintering shrinkage ratio. Now many of the applications of dynamic magnetic suppression is close to the industrialization stage, the first moving magnet system has set up a file in the run.

Sweden developed powder metallurgy with high-speed suppression method. This may be a powder metallurgy industry and a major technological breakthrough. High-speed pressing adopts hydraulic impact machine, and the tradition, it has many similarities, but the key is pressed, 500 ~ 1000 times faster than traditional the head speed up to 2 ~ 30 m/s, and is suitable for mass production. Hydraulic drive of heavy hammer (5 ~ 1200 kg) can produce strong shock waves, within 0.02 s pressing energy through the die to powder densification. Hammer the quality and impact of the speed of decided to suppress energy and densification degree.

2. The high speed suppressed

High-speed pressing another characteristic is the multiple wave, interval of about 0 3 s additional shock waves will density increasing. A multiple impact to improve the density of the advantage is, available smaller than traditional suppression equipment manufacturing large parts weighing 5 kg or more.

High-speed suppression is suitable for manufacturing valve seat, valve guide, the main bearing cover, wheel, gear, flange, connecting rod, shaft sleeve and bearing race, etc.

Compared with the tradition, the advantages of high speed crushing is:

Suppression of a density increase, increase at about 0.3 g/cm3,;

Suppression of a tensile strength can be increased by 20% ~ 20%;

High speed suppressing radial elastic aftereffect is very small, compact ejection force is relatively low;

High-speed pressed density is uniform, the deviation is less than 0.01 g/cm3.

Compaction technology is a new development of a new technology in recent years. It is added to the mixture high temperature new lubricant, then put the powder and mould to mould rigidity, heated to 423 k or so the traditional sintering process is adopted to improve the sintering technology, is ordinary moulding technology development and extension of the international powder metallurgy industry known as "creating new era iron-base powder metallurgy parts application" and "lead to powder metallurgy technology revolution" of the new type of molding technology.

3. The temperature pressure molding technology

Characteristics of temperature, pressure technology:

At a relatively low cost produce high performance powder metallurgy components;

Improve the green density parts and high strength, easy to manufacture complex shape and required precision of zero parts;

Product density is uniform.

Core of temperature, pressure technology research and development:

Advance manufacturing technology of alloying powder;

The design of new type polymer lubricant;

Graphite powder adding technology effectively;

No segregation powder manufacturing technology;

Temperature pressure system preparation technology.

Compaction technology mainly is suitable for the production of iron base alloy parts. At the same time, people are trying to use this technology for copper alloy and other material parts. Due to improve the density of temperature, pressure parts better, thus greatly improving the iron-based powder metallurgy products, such as reliability, so the temperature press technology in automotive manufacturing fields such as machinery manufacturing, home to weapons manufacture there is a broad application prospect.

Flow compaction technology based on the compaction technology, and combined with the advantages of metal injection molding, by adding appropriate amount of fine powder and increase the content of lubricant and greatly improve the fluidity, filling ability of the mixed powder and formability, and the process is the use of regulating the packing density of powder with lubricant content to improve the formability of powder material. It is between metal injection molding and the traditional die forming technology.

4. The flow pressure technology

Blended powder flow compaction technology is the key to improve liquidity, mainly by two methods:

The first method is to add fine powder in the powder. The fine powder can fill in the gap between large particles, so as to improve the apparent density of mixed powder.

The second method is to add more adhesive than traditional powder metallurgy technology and lubricant, but its much less than for the amount of powder injection molding. Binder or lubricant to optimize the dosage, mixing powder in suppressing is transformed into a kind of high filling liquid fluid.

Combine the above two methods, the mixed powder liquidity under the pressing temperature can be turned into good sticky fluid, it not only has all the advantages of the liquid, and has the very high viscosity. Rheological behavior of the mixed powder makes the powder in the process of suppression can flow to every corner and not to produce crack.

Flow pressure technology the main features are as follows:

(1) forming part of the complex geometric shapes. Abroad are already was prepared successfully using conventional compaction process some shape more complex powder metallurgy parts, such as cars drive torque converter turbine hub, connecting rod and gear parts, etc.

(2) high density and uniform performance. Flow compaction process because of the apparent density is higher, the temperature and pressure in the intermediate density can reach very high value. Flow compaction due to the process of powder, good fluidity, the resulting material density are more homogeneous.

(3) has good adaptability. Flow of powder compaction process has been used in low alloy steel, stainless steel 316 l powder, pure Ti powder and WC - Co cemented carbide powder. In principle, it can be applied to all of the powder system, the only condition that the system must have enough good sintering performance, so as to achieve the required density and performance.

(4) to simplify the process, reduces the cost.

The United States developed a can produce full dense parts at room temperature without subsequent sintering of powder metallurgy technology. This process is called "cold forming of powder metallurgy. It USES a special activation solution with feeding boots technical innovation, precisely the powder into the mold under pressure. Pressurized conveying feeding boots make powder filling more uniform, while the active solution to prevent formation of oxides, which greatly promoted the cold welding effect.

4. The cold forming process

Using a process that can be made full density is close to the final shape of parts, the suppression without after sintering and machining. This process USES the coated powder. But many of the commercially available metal or non-metallic powder can also be used. At present the process of the development work focused on production of hot parts operation, but the process also applies to parts of production structure and other USES.

In ordinary sintering technology on the basis of applying force by improving heating source, the action such as in a relatively short time make the powder densification process, mainly include electric spark sintering and microwave sintering technology, etc.

Microwave sintering is absorbing microwave for powder by sintering, the electromagnetic energy is directly converted into the energy of particles in the material, make its internal heat and sintering method. Thermal efficiency is high, it can rise sharply shorten sintering time, coupled with microwave interaction between particles, reduces the activation energy between the particles, accelerate the densification of the material. It than traditional electric furnace to heat conduction, thermal convection and thermal radiation of external heating method has higher efficiency. To avoid the external heating caused by internal and external temperature gradient sintered body defects such as cracks or deformation significantly.

1. The microwave sintering technology

Burned into a variety of materials: materials such as ceramics and ferrite. Furthermore, developed in Japan and similar millimeter wave sintering technology, and successfully under 2023 k insulation 1 h dense sintering of AlN materials.

Dual-band microwave sintering furnace

Production with large microwave sintering furnace

2. The explosion suppression technique

Repression is also called the blast suppression method is a promising technology, it has played a very important role in the powder metallurgy, explosion suppression, just on the surface of particles generate instantaneous high temperature, short action time, temperature and cooling speed. Appropriate control explosion parameters, makes the material density to theoretical density of more than 90%, even up to 99%.

Explosion suppression device schematic diagram

Domestic use NdFeB magnetic powder explosion suppression technology research was carried out. The performance of magnetic powder: magnetic induction coercive force Hcb = 453.08 kA/m, Br = 0.783 T, (BH) Max = 89.9 kJ/m3. The NdFeB magnet performance is: the resulting from the explosion suppression Hcb = 403 ka/m, Br = 0.805 T, (BH) Max = 90.7 kJ/m3.

As can be seen from the measurement results, the explosion suppression of ndfeb magnet magnetic performance, can maintain the original magnetic powder maximum magnetic energy product no too big changes. This is out of reach for conventional bonded NdFeB magnets.

3. The discharge plasma sintering (SPS)

Discharge plasma sintering is the metal powder into the mold made of graphite material, the use of upper and lower die and electricity electrode would impose on specific sintering power and suppress pressure sintering powder. The discharge activation, thermoplastic deformation and cooling stage to complete or parts of a method for making high performance materials. It is a new sintering technology of powder metallurgy, the electric energy and mechanical energy is the assignment at the same time in sintering is a new technology of powder.

The SPS sintering principle diagram

SPS principle is to use strong pulse electric current on the powder particles generate many conducive to rapid sintering effect:

1) due to the pulse discharge produced plasma shock wave and electron, ion in the electric field in the opposite direction of high speed flow, can make the powder adsorption gas from escaping, initial oxidation film on the surface of the powder can be disruptive to a certain extent, to purification, activation powder;

2) due to intermittent pulse is instantaneous and high frequency, the powder particles not contact parts produced by the electric heating, as well as the joule heat generated in the powder particles contact parts, greatly promoted the powder particles atoms diffusion, the diffusion coefficient of hot-pressing condition is much larger than usual, so as to achieve the rapidness of powder sintering;

3) rapid pulse current to join, whether it is within the powder discharge parts or the joule heating parts, fast moving, powder sintering of homogenization.

Compared with traditional powder metallurgy process, the characteristics of the SPS process are:

Powder raw material widely: all kinds of metal, not gold, alloy powder, especially the large activity of various particle size of powder sintering SPS can be used as the original.

Forming of low pressure: SPS candle when junction through full micro discharge processing, sintering powder surface in target activation condition. To this end, the forming pressure only need cold-press sintering l / 10 ~ 1/20.

Short sintering time, sintering small parts usually only takes a few seconds to several minutes, the heating rate can be as high as 106 ℃ / s, automated production of small parts productivity can reach 400 / h.

Using graphite mould, low cost, easy to processing.

Sintering under atmospheric: electric spark sintering is generally, under the atmosphere even highly active beryllium parts can be sintered in the atmosphere.

Pulse power supply, usually USES the dc and ac superposition of pulse power supply.

Energy saving, high thermal efficiency, power consumption is only 1/10 of the equivalent resistance sintering.

Materials can be processed SPS

SPS technology preparation of functionally gradient materials

Through the SPS technology can produce ceramic/metal, polymer/metal and other thermal gradient, gradient, the hardness gradient, conductive material such as gradient, porosity gradient. Gradient layer to 10 layers.

In the United States, the national institute of standards technology and mechanical engineering laboratory with Japan's international trade industry department cooperation, to jointly develop a more efficient engine heat resistant, high strength gradient materials with large sizes. Can now mass production of 150 mm, 15 mm thick, 11 layers of ZrO2 gradient material. Adoption of SPS process parameters are: 20 ~ 40 mpa pressure, temperature of 1243 ~ 1293 k, the heating rate of 50 k/Min, 10 pa vacuum degree.

Using SPS sintering got glass at both ends are respectively 100% and 100% of the 304 stainless steel, and in the middle of 4 layer gradient material. Sintering temperature 1073 k, keep time 15 min, carried out under vacuum.

SPS technology preparation of magnetic materials

Can be produced by SPS technology SiGe/PbTe/BiTe/FeSi CoSb3 is a thermoelectric conversion element, and is widely used for various functions in the field of electronic materials, superconducting materials, magnetic materials, such as target material, dielectric materials, hydrogen storage materials, shape memory materials, solid battery materials, optical materials, etc.

SPS preparation of soft magnetic materials

Usually use quenching or injection method can get FeMe B (Nb, Zr and Hf) of amorphous alloy, after treatment was slightly higher than that of crystallization temperature, the grain number 10 nm, can be obtained with body centered cubic structure, high Bs, small magnetic loss of nanocrystalline materials. But amorphous alloy at present is only strip or powder, also on the production of finished products need to strip overlap and consolidation with resin, which makes the density of the finished product and Bs are lower. Using SPS technology research in recent years, Japan FeMeB tile forming condition and magnetic.

With SPS preparing blocky Fe90Zr7B3 soft magnetic nanocrystals process is: first by amorphous thin belt into the ball of 50 ~ 150 microns of amorphous powder into the WC/Co alloy mould, and in the SPS sintering on the sintering (below 1 x 10-2 pa vacuum, heating speed is 0.09 ~ 1.7 K/s, temperature of 673 ~ 873 K, pressure 590 mpa), put the proceeds from the sintered body at 1 x 2 pa under vacuum, 10 - to 3 7 K/s speed made after heated to 923 K, the heat preservation. Materials show better magnetic can: maximum permeability dynamic permeability under 29800, 100 hz 3430, coercive force 12 a/m.

SPS preparation of bulk nanocrystalline FeMeB series permanent magnet materials

Japan carried out the preparation with SPS Fe66Co20Nd2Pr7B5 anisotropic permanent magnet. Will quench made of amorphous thin grinding ball into 37-105 microns of powder, into the WC/Co alloy mold, the SPS sintering on the sintering (374 ~ 636 mpa pressure, the temperature of 673 ~ 873 k), and then sintered body under vacuum 1 x 10-2 pa, in 973 k to 973 s. The results show that the sintering temperature of 873 k, pressure 636 mpa, the relative density of sintered body is 97 6% ~ 98 6%. Through magnetic measurement show that the sintering pressurized the direction of the maximum magnetic energy product is bigger than the direction of the parallel, and with the increase of SPS sintering temperature and pressure, anisotropy increases.

Japan also studied as a exchange spring magnet Fe76Nd9Co8V1B6 bulk nanocrystalline materials research. USES the SPS process, will quench thin belt formed a piece of burning wood. Experimental results show that: the pressure 940 mpa, temperature 948 k, 1 min of the SPS process can get good magnetic: Br = 1.02 T, Hcj = 461 ka/m, m = 122 kj/m3 (BH), Hk/Hcj = 30%, rho = 7.67 g/cm3. Under the condition of 373 k x 1 h heat, magnetic material of the irreversible loss of only 4%, and the MQP - B bonded magnets are roughly the same.

SPS preparation high BaTiO3 dielectric material

Japan reported within the BaTiO3 powder into graphite mould, using SPS technology (39 mpa pressure, ventilation with current 4000 a, temperature 1373 k, time is 3 min) made of sintered body, its density of 5.82 g/cm3, amounted to 97% of theoretical density, and the traditional sintering method can reach 88%; SPS sintered body of the grain size of 0.5 mu m, basically the traditional sintering for 1 ~ 1.5 microns. SPS sintered body of dielectric coefficient of 6200, compared with the traditional sintering can reach 2400.

SPS technology production of cemented carbide

In Japan, SPS is put into batch production cemented carbide in the first place. Sumitomo coal mining co., LTD has established the SPS in Hokkaido, super hard alloy production demonstration plant, and formed the TC series products. In the table below lists the TC10, TC20 and cobalt free TC00 performance of the alloy.

SPS production of fine ceramic technology

Because the SPS sintering effect of pulse discharge characteristic, can be widely sintering of various oxides, nitrides, silicides, carbide and boride, etc. SPS sintering of Si3N4 + Al2O3 fine ceramics (circular, cylindrical, cylindrical, round cakes, etc.) has been widely used as heat resistant wear resistant material. SPS sintering inhibits grain growth, eliminate pores and the sintering inhomogeneity, relative density of 99% ~ 99%, HV reach more than 20 gpa.

High purity, high density, the sintering of SiC

The SPS can make without bond SiC sintered by more than 99% of the theoretical density, while the traditional sintering method can reach 92% ~ 93%. Sintering process of SPS are as follows: temperature 2673 k, heating and heat preservation time 7 min. Are listed below under the two methods of sintering SiC ceramic performance comparison.

SPS technique was used to prepare porous materials

SPS can be in a short period of time not only at the sintering densification of materials, and by choosing appropriate technological parameters (mainly pressure), but also for making an ideal porous material. In recent years, Japan with rutile, cutting cast iron powder, atomized iron powder and so on has carried on the SPS sintering porous materials.

The SiC whisker into graphite mould, in 1973 ~ 2273 k, 10 ~ 80 mpa, 5 ~ 60 min cheap relatively system of sintering process conditions. When sintering pressure to 10 mpa, the porosity of sintered body reached 63%, the flexural strength reaches 42 mpa; When sintering pressure of 80 mpa, the porosity of sintered body reached 34%, the flexural strength of 80 mpa.

SPS technique was used to prepare the uniformity of the pores in porous materials is very good. The atomization Ni20Cr (20 microns) mean particle size of powder preparation of porous materials with SPS technology, SPS sintering process parameters is vacuum, temperature 1073 k, 300 s sintering. In porous radius (25 mm) direction, the uniformity of the porosity is very good, the regional porosity difference less than 2%. You couldn't see in the section of SEM topography on the phenomenon of pressure under the direction of the particles get squashed, and combination between particles is very good, open hole porosity about 33%.

4, metal powder injection molding technology

Metal powder injection molding technology is developed with the application of polymer materials and a new type of consolidation of metal powder, metal powder and ceramic powder special forming method. It is to use a lot of thermoplastic binder with powder injection forming mold, in low and static pressure such as uniform, consolidation forming, and then take off the adhesive sinter.

Injection molding products

This technology can be made with regular moulding powder technology complex shape structure that could not be made, such as hole with thread, vertical or high fork acute Angle, wing, etc.), many steps, wall products, have a higher density of the material (93% ~ 100% of theoretical density) and the strong toughness, and has the characteristics such as isotropic material. At present the technology become the most dynamic new technology of powder metallurgy field and has entered the stage of industrialization.

Products are made of metal powder injection molding technology gear auto parts, communications equipment components (such as mobile phone of information communications equipment and computer OA devices), power tools, locks, Musical Instruments, medical devices and sewing machine parts, industrial equipment components and magnetic components, gun sight bracket, pistol back hook and firing pin, window lock block sector, loom triangle block, glasses frame of flexible hinge, glasses legs, watch case, etc. Product has an obvious characteristic: the small, complex structure, density and higher precision. Materials in addition to the iron nickel alloy, and titanium and titanium alloy, aluminium and aluminium alloy, hard alloy and alloy, etc.

Micro injection molding

Powder injection molding technology, the traditional 0 ~ 1 mm size can be obtained from components, has obtained the minimum 20 mg parts. But with the development of the micro system, including micro optics, minimum invasion surgery and micro jet technology, etc., need complex shape, size in micron range of metals and ceramic parts. Micro injection molding is suitable for large-scale manufacturing micro structures.

Germany in 10 years ago began studying micro injection molding technology, but the raw material for thermoplastics, minimum size has amounted to 0.2 mu m. Germany on the basis of the study, is now studying micro ceramic taste micro injection molding and metal injection molding technology. Powder used for an average of 1 5 microns of carbonyl iron powder granularity, 4 ~ 5 microns of 0.6 mu m stainless steel powder and alumina powder. Used binder has a mix of polyolefin/wax compounds together with normal aldehyde compounds. Take off the adhesive method is heated to remove organic matter in the study of law, poly aldehyde compound catalytic to take off the adhesive method and supercritical carbon dioxide to take off the adhesive method.

After making products after pressure by density was 98%, and the linear shrinkage 15% ~ 22%. Minimum and ceramic injection molding parts size 10 microns, micro injection ceramic wheel weight was only about 0. 5 mg, the smallest micro metal injection molding parts size of 50 microns. Micro injection molding is used for the micro pump, micro gear, micro turbines, minimal injury surgical miniature catheter, etc.

Five, the rapid prototyping technology

Rapid prototyping technology is developed in recent years, using computer aided design and manufacturing technology of complex shape parts. Using three-dimensional computer aided design, computer tomography X-ray camera digital data type, finite element analysis, or the mother, to three-dimensional description for parts, parts will be divided into many thin layer level, get the corresponding process parameters. After the input process parameters, rapid prototyping machine can automatically produce the parts. Most rapid prototyping method using powder raw materials. Commonly used method is, laser sintering, the multiphase jet consolidation method and three dimensional printing method, etc.

The principle diagram of the selective laser sintering (SLS) process

Selective laser sintering process is to use laser sintering production plastic prototype one layer at a time. Now can choose a variety of powder, including metal powder and ceramic powder. Metal powder laser sintering choice, aims to direct production features. The industry has a great interest on it, because it is in the product development process, save time and reduce costs.

SLS system and products

Polyphase free jet consolidation method is a new forming technology. Can be used to make biological medical parts, such as orthopaedic implants, orthodontics and repairing material, general surgical repair parts, etc. Multiphase jet consolidation method, according to CT scan to get 3 d description of the prosthesis, can make surgery needed parts, usually without surgery to actual measurement. Mix powder metal or ceramic powder and binder, form a homogeneous mixture. Multiphase jet consolidation method is to spray according to technical requirements, the mixture layer by layer to form a part. After the parts form, one of the binding phase or heat removal with chemical method, and then sintered density to the final.

Multiphase jet consolidation method flow diagram

Three dimensional printing was invented in the United States at the Massachusetts institute of technology. The method is based on printing technology, through the computer aided design, the binder accurate deposition on a layer of metal powder. Print one by one, like this repeatedly until you reach the final geometry. Has got a green one. Green piece by sintering and melt in a furnace, permeability, and can achieve full density.

3 d printing process flow diagram

3 d printing method is different from the prototype making selective laser sintering. Which can only produce one parts at a time, while the former can produce several different shapes of parts at the same time. 3 d printing method has two advantages: first, it can make any shape of parts, including free cavity, inner hole, taper or bubbles on the surface of the parts. Second, the production speed is fast. Time-consuming costly traditional prototyping method, a prototype parts for weeks or months to make, and with 3 d printing method, a few days can be completed.

Powder metallurgy application domain expands unceasingly, new technology emerge in endlessly. The powder metallurgy industry in China started not late, but the product quantity, quality and technology compared with advanced countries, there are quite a gap. And therefore should understand and master new technologies that are always present in time is especially important, should take the initiative to develop our new technology.