Overview of the world's powder metallurgy industry
The total amount of global powder shipments in 2003 was about 880,000 tons, of which the United States accounted for 51%, 18% in Europe, 13% in Japan, and 18% in other countries and regions. Iron powder accounts for more than 90% of the entire total powder. Since 2001, the world market for iron powder has continued to grow, an increase of nearly 20% in four years.
The automobile industry is still the biggest driving force and the biggest user of powder metallurgy industry development. On the one hand, the production of automobiles is increasing, on the other hand, the amount of powder metallurgy parts in a single car is also increasing. North America has the highest average amount of powder metallurgy parts per car, which is 19.5 kilograms, Europe has an average of 9 kilograms, and Japan has an average of 8 kilograms. China has a huge powder metallurgy parts market prospect due to the rapid development of the automobile industry, which has become the focus of attention of many international powder metallurgy enterprises.
Powder metallurgy iron-based parts in automobiles are mainly used in engines, transmission systems, ABS systems, ignition devices and so on. The two major trends in automotive development are to reduce energy consumption and environmental protection; the main technical means is the use of advanced engine systems and lightweight.
European exhaust filtration for automobiles provides a large market for powder metallurgy porous materials. In the current engine operating conditions, powder metallurgy metal porous materials than ceramic materials have better performance advantages and cost advantages.
Tooling materials are another important category of products in the powder metallurgy industry, of which particularly important is cemented carbide. Manufacturing is currently moving in the 3A direction of Agility, Adaptivity and Anticipativity. This requires that the processing tool itself is sharper, more rigid, higher toughness; processing the range of materials to expand to Lvhe, magnesium alloys, titanium alloys and ceramics, etc.; higher dimensional accuracy requirements; processing cost requirements are lower; the environmental impact should be minimized, the proportion of dry machining is greater. These new requirements accelerate the development of powder metallurgy tool materials. Cemented carbide grain (<200nm = and ultra-coarse grain (>6um); coating technology is developing rapidly, CVD, PVD, PCVD technology is becoming increasingly sophisticated, and there are many types of coatings, from the commonly used CVDTiCN/Al2O3 /TiN to the CVD PCBN (Polycrystalline Cubic BN) as well as the PVD TiAIN, Al2O3, cBN (Cubic BN) and SiMAlON, etc. to meet the needs of processing occasions.
The development of the information industry also provides new opportunities for the powder metallurgy industry. Japan's electronics industry with powder metallurgy products has reached $ 4.3 per year, of which 23% of heat sink materials, light-emitting and point pole materials accounted for 30%. The former mainly includes heat sink materials, such as Si/SiC, Cu-Mo, Cu-W, Al-SiC, AlN and Cu/diamond materials; the latter mainly includes tungsten and molybdenum materials.
Powder injection molding
Powder injection molding is still one of the hot spots of current research. Powder injection molding of materials has developed from the early iron-based, cemented carbide, ceramics and other insensitive to the impurity content, performance requirements are not very demanding system, to nickel-based high-temperature alloys, titanium alloys and niobium materials. The field of application of materials has also developed from structural materials to functional materials, such as heat sink materials, magnetic materials and shape memory alloys. The material structure has also evolved from a single homogeneous structure to a composite structure. Metal injection molding technology allows for the simultaneous molding of powders of many different compositions, which results in composite structures in the form of sandwiches. For example, the 316L stainless steel and 17-4PH alloy composite, can realize the mechanical properties of the continuous adjustable. An important development direction of powder injection molding is closely related to microsystem technology. In closely related to microsystems technology. In areas related to microsystems, such as electronic information, microchemistry, medical devices, devices continue to miniaturize, more composite functions. And powder injection molding technology provides the possibility of realization. Micro-injection molding technology is an improvement of the traditional injection molding technology. It is for parts of the size structure as small as 1um developed by the molding technology, the basic process and the traditional injection molding consistent, but the raw material powder particle size is smaller. The use of micro-injection molding technology has developed a surface microstructure accuracy of 10um microfluidic devices, the size of 350um ~ 900um stainless steel parts; to achieve a different material composition, composite structure of the *** sintering or *** connection, to obtain the magnetic/non-magnetic, conductor/non-conductor micro-composite parts.
Powder Preparation Technology
Powder atomization has been a high-performance powder preparation technology. Hot gas atomization technology can extend the time of the metal droplets in the liquid phase state, so that the powder can go through the second broken (atomization), thus greatly improving the efficiency of the atomization, the powder obtained by the finer particle size.ASL company's research results show that, if the gas temperature is increased to 330 ℃. Preparation of the same particle size powder required to reduce gas consumption by 30%, its economic analysis and engineering research shows that the technology is completely feasible. Powder atomization aspects of the technology has been greatly improved. For example, the use of a new type of free naked gas atomization, can get finer tool steel powder, carbide distribution in the particles more uniform, less defects. The U.S. Hegelas company will be advanced steelmaking technology for powder production, the integration of electric arc furnace (EAF) technology, argon oxygen decarburization technology (ADO), high-performance atomization technology and hydrogen annealing technology, greatly improving the quality of the powder, powder billet density and strength has been improved. In the active powder atomization, in order to reduce the melting process melt and crucible reaction, Germany developed the electrode induction melting gas atomization (EIGA) technology, can be prepared with high activity of titanium, zirconium, and TiAl intermetallic compound powder. Mechanical alloying is still a hot research topic, but most of it is laboratory work. It is worth mentioning that the German company Zoz only with their own development of high-energy ball milling equipment to grind the arc melting furnace slag, and then through wet metallurgy to recover the metal, this technology not only improves the environment, has opened up a huge market.
Powder compacting technology
Traditional powder compacting technology relies heavily on equipment improvements and process optimization. Several well-known press manufacturers have introduced new models with more accurate precision control and a higher degree of automation.
Powder sintering theory and technology
Microwave sintering, as a new rapid sintering technology, has been fully applicable to metal powder materials, such as powdered steel, cemented carbide, non-ferrous metals and so on. The industrialization of microwave sintering may be just around the corner, as neither the maturity of the equipment and technology, nor the batch production capacity is too much of a problem; and the main obstacle is the acceptance and risk level of the producers.
Discharge plasma sintering (SPS) has also been studied quite a lot, and the material system has been extended from ceramics to metallic materials, especially some ultra-fine crystalline materials, such as aluminum alloys, magnesium alloys and self-lubricating iron-based materials. However, due to its single-piece production characteristics, I am afraid that the method can only be used for some basic research.
Jet deposition is very advantageous in the preparation of large, fine-grained materials. The technology was initially used to produce aluminum alloys and aluminum-silicon alloys. As melting technology has improved, jet deposition has been used to prepare tool steels and high-temperature alloys. The University of Bremen, Germany, reported using jet deposition to prepare a high-temperature alloy ring with a single piece mass of more than 100 kilograms, an inner diameter of 40 mm, an outer diameter of 500 mm, and a width of 100 mm.
Rapid prototyping technology has attracted the attention of many scholars in recent years. In the field of powder metallurgy is the most widely used direct metal laser sintering. Currently the technology has been used for steel powder and titanium alloy powder and so on. Another metal rapid forming method is three-dimensional printing. This method is very convenient for three-dimensional microstacking of various alloys of different compositions according to different structural needs, which is still in the conceptual stage. However, the technique has been used to prepare a number of structures consisting of metal + binder, as well as gradient functional materials.
Metal powder porous materials
Metal powder porous materials have a wide range of applications, such as lightweight structural materials, high-temperature filters, and separation membranes. The biggest market at the moment is probably soot filtration devices for diesel engines. Germany's Fraunhofer Institute developed a metal hollow ball preparation technology, in the polymer matrix coated with metal powder slurry, and then through the de-coating of the polymer matrix and binder, and finally sintered into a variety of metal spheres with hollow structure. The diameter of the spheres can be from 1mm to 8mm, and the density of the prepared steel hollow spheres is only 0.3g/cm3.
Cemented Carbide
Nanocrystalline and gradient structures are the two key directions for cemented carbide. The nanocrystalline material aspect includes grain growth control and nano-powder preparation. The gradient structure alloy aspect includes the relationship between process and structure. Combining nanocrystalline and gradient structures may be a good direction to achieve tunable properties at a more microscopic level. The high hardness and poor machinability of Cemented Carbide has led to a trend towards the use of injection molding to prepare small and medium-sized parts with complex shapes, but their commercialization is still controlled by the maturity of the technology. Other aspects of work on cemented carbides include tensile rare earths and alloying elements, fracture toughness and reliability characterization.
Powder light metal alloys
Automotive lightweight for aluminum, magnesium, titanium and other light metal materials provide a broad application prospects. Powdered aluminum alloys can be applied in many parts of the car, but Al-Si alloys are likely to take the lead in large-scale application in oil pump gears due to their high specific strength, high specific stiffness, low coefficient of thermal expansion and good wear resistance. From the industrialization point of view, the optimization research on the preparation process of powder metallurgy aluminum alloy is more important. Another research hotspot of aluminum alloys is composite materials, including the traditional Al/SiC, Al/C, Al/BN, Al/Ti (C, N) and the newly emerged aluminum alloys reinforced with carbon nanotubes. High-strength powdered aluminum alloys are closely related to rapid solidification technology. Aluminum alloys with a combination of high strength, high toughness, and high thermal stability can be prepared by adding intermetallic compounds rows of components to a pure aluminum matrix through compositional design. The material's room temperature strength is greater than 600Mpa, elongation of more than 10%, at 400 ℃ there is a very good thermal stability, fatigue limit is two times the forged aluminum alloy.
Magnesium alloys are much less dense, and their application prospects may be better, but they are still in a research state. The use of rapid solidification method is also an important means of preparing high-performance powder magnesium alloys. At present, the technology has no major problems in terms of safety, and the performance of the prepared material is much higher than the casting alloy.
Titanium alloys in automotive applications is mainly a cost issue, and the main obstacle to powder titanium alloys is high-performance low-cost titanium powder. QinetiQ Ltd in the UK has developed a store deoxidation technology (EDO) to mass produce titanium powder. The technology is completely different from the traditional hydrogenation dehydrogenation process using titanium sponge as raw material. It is a method similar to molten salt electrolysis, with TiO2 as the cathode and graphite as the anode. During the electrolysis process, the anode of TiO2 migrates and consumes the carbon of the anode to form CO, and titanium powder is obtained at the cathode. The oxygen content of the titanium powder is between 0.035% and 0.4%. Various titanium alloy powders can also be easily prepared using this technique. Due to the sensitivity of the atmosphere and impurities, the sintering of powdered titanium alloys is also a difficult process, usually with to hot isostatic pressing or subsequent thermal processing. Through the addition of *** crystal shape into components and rare earth elements can significantly improve the sintering density of powder titanium alloy, its mechanical properties can also reach the level of forging titanium alloy. This series of work will greatly promote the application of titanium alloy in the key components of automobile machine.
Powder parts subsequent processing technology
The subsequent processing of powder metallurgy parts performance is critical. Sinter hardening integrates sintering and heat treatment, and the alloy composition and cooling conditions have a great influence on the material properties.Miba has evaluated the machinability of parts using drilling techniques. Kobe Steel added a complex calcium oxide to sintered steel in place of the commonly used MnS, significantly improving the machinability of the part without compromising its mechanical properties. In addition with the expansion of applications, the cutting of powdered aluminum and composites, and wire cutting of porous materials have also received attention.
Surface hardening is an important means of improving powder metallurgy gears. Although the density of iron-based parts has been able to reach 7.4g/cm3, there is still a need to further improve the density and hardness at the root and contact surfaces. The use of radial rolling has become an important means, at present, the major iron-based parts manufacturers of high-performance powder metallurgy gear production and application have shown great concern.
Powder metallurgy process simulation and standardization
Europe launched two programs (PM Modnet and PM Dienet), first for the simulation of iron-based parts production process, and then seek to expand to other material systems, has achieved many results. In the UK, a large research program has been initiated, consisting of seven research groups and 23 companies, focusing on the process control of pressing processes for a variety of materials. Therefore, the simulation of powder pressing process has become a research hotspot, relatively speaking, the basic theory of the work, such as densification equations and constitutive equations of the work is less, while the use of finite element method and other numerical simulation methods. Of course, the simulation of the pressing process also includes friction, demolding, mold filling, and the simulation of the performance of the compression blank.
Dynamic observation of powder metallurgy process and product quality control are closely related to daily production. Using X-ray CT methods, it is easy to dynamically observe the powder sintering process in terms of three-dimensional density, porosity, particle size distribution and sintering neck growth. The use of high-temperature IET also enables the determination of the stiffness and internal consumption of the material, which, in combination with other means, can easily describe the dynamic evolution of microstructure and mechanical properties. Cracks in injection blanks can be quickly detected using dynamic thermography. At present, the most used in the production line is the acoustic means, the major powder metallurgy companies have utilized this nondestructive flaw detection technology to discover defective products or predict product performance in a timely manner, which includes GKN of Germany, Nissan Motor of Japan, and AMES of Spain. However, this quantitative analysis is a systematic work, including multivariate statistics, graphical analysis, physical and chemical theories and numerical simulation, etc., only multi-disciplinary workers work together to achieve accurate characterization.
Powder metallurgy methods are very advantageous for the preparation of certain special functional materials, such as the use of mechanical alloying to be able to prepare nanostructured MgB2 superconducting materials and CuNb magnets. The largest market for powder functional materials is magnetic materials. In terms of NbFeB materials, the use of atomized powder to improve density and performance is the most important direction. The powder is suitable for injection molding and thus is very interesting for the preparation of small and medium-sized shaped magnetic material parts. Soft magnetic composites (SMC), which are solidified iron powders with composite structures, have a very large application market in electric motors. As a result, there is a lot of research in this area, including market and application analysis, structural design and optimization, production and process control, fatigue properties.