Summary of New Powder Metallurgical Forming Technologies in China in the Last Decade

Summary of New Powder Metallurgical Forming Technologies in China in the Last Decade

Powder metallurgy is an advanced manufacturing technology that integrates material preparation and part forming, energy-saving, material saving, high-efficiency, final forming, and less pollution. It has an irreplaceable position and role in the material and part manufacturing industry, and has entered the forefront of contemporary material science.

At present, powder metallurgy technology is developing towards high density, high performance, and low cost. This article focuses on introducing several new forming technologies for powder metallurgy parts in the past decade.

1、 Warm compaction technique

Warm compaction technology is a new technology developed in the field of powder metallurgy in recent years, which 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 pre alloy powders and molds with special lubricants to 130 to 150 ℃, and control the temperature fluctuation within ± 2.5 ℃. Then, like traditional powder metallurgy processes, powder metallurgy parts are produced by pressing and sintering. The technical keys are: first, warm compaction powder preparation, and second, warm compaction system.

Compared with traditional processes, the density of warm compaction compacts has an increase of about 0.15 to 0.30g/cm3, and its density can reach 7.45g/cm3. Under the same pressing pressure, the yield strength of warm pressing materials is on average 11% higher than that of traditional processes, the ultimate tensile strength is on average 13.5% higher, and the impact toughness can be improved by 33%. In addition, the green strength of warm pressed parts is high, up to 2O~30MPa, which is 50~100% higher than traditional methods. This not only reduces the damage rate during green handling, but also enables machining of the green, with a good surface finish. In addition, the warm pressing process has low pressing pressure and small demoulding force, while the performance of the parts is uniform, the product accuracy is high, and the material utilization rate is high.

The warm compaction process is also characterized by its simplicity and low cost. The research shows that if the cost of a conventional powder metallurgy process of one-time pressing and sintering is 1.0, the relative cost of powder forging is 2.0, the relative cost of re pressing and re sintering is 1.5, the relative cost of copper infiltration is 1.4, and the relative cost of warm compaction technology is 1.25. Currently, there are more than 200 kinds of powder metallurgy parts produced using warm compaction technology, with the weight of 5-1200g. For example, Sinterstahl GmbH of Germany used warm compaction technology to produce complex synchronous gear rings for friction transmission, and won the award at the PM2TEC2001 International Conference held in New Orleans, USA. The tooth density of the part exceeds 7.3 g/cm, the ring density exceeds 7.1 g/cm, and the green strength reaches 28 MPa. Diffusion alloying sintered hard pressed powder is used, with a minimum tensile strength of 850 MPa. Due to the use of warm compaction technology and the use of powder metallurgy parts, the overall cost has been reduced by 38%.

2、 Flow warm compaction technology

Warm Flow Compaction (WFC) is a new near-net forming technology for powder metallurgy components, which is based on powder compaction and warm compaction molding processes and combines the advantages of metal powder injection molding. The key technology is to improve the fluidity of the mixed powder. By improving the fluidity, filling ability, and formability of the mixed powder, it is possible to accurately form parts with complex geometric shapes, such as those with grooves, holes, and threaded holes perpendicular to the pressing direction, on a traditional press at temperatures ranging from 8O to 130C, without the need for subsequent secondary machining. WFC technology not only overcomes the shortcomings of traditional powder metallurgy in forming complex geometric shapes, but also avoids the high cost of metal injection molding technology. It is a promising new technology with very broad application prospects.

WFC technology, as a new near-net forming technology for powder metallurgy parts, has the following main characteristics: (1) It can form parts with complex geometric shapes; (2) High compact density and uniform density; (3) Good adaptability to materials; (4) The process is simple and the cost is low.

Currently, WFC technology is still in the initial stage of research abroad, and the research on its key manufacturing technology and densification mechanism has not been reported yet