用温压制造高密度材料的关键参数

KEY PARAMETERS FOR WARM COMPACTION OF HIGH DENSITY MATERIALS

温压技术是由在加热的阴模中压制预热的粉末组成[1],已知温压有助于零件密实,从而改进烧结件的性能[2,3]。温压需要在适合温压的温度范围内进行。特别是,粉末混合粉应具有好的流动性,同时对阴模模壁有良好润滑性,以减小脱模力。在试验室和工业生产中都研究了用粘结剂处理的和未经粘剂处理的用温压技术制造的材料的性状与性能。为了确定和定量各种关键生产参数,诸如压制压力,粉末温度与阴模温度,生产速率及零件大小对生坯和烧结件特性和零件脱模力的影响,进行了专门的试验研究。依照粉末流动性与松装密度的稳定性,压制压力与温度以及压制零件的重量与密度讨论了温压的工艺性。

The mechanical properties of high performance P/M parts depend heavily on material composition and the density reached during processing.Warm compaction technique,which consists of pressing preheated powder in a heated die[1],is known to favour densification of parts,leading to an improvement of sintered properties.Warm compaction requires powder mixes with specific physical characteristics to be adequately processed in the temperature range involved in warm pressing.In particular,powder mixes should provide good flowability and good lubrication of the die walls in order to reduce ejection forces. Behaviour and properties of binder and non-binder treated materials processed by the warm compaction technique were investigated both on lab and industrial scales.Specific test programs on a production press were conducted to identify and quantify the effects of different key production parameters such as the compaction pressure,the powder and die temperatures,the production rate and the part size on green and sintered characteristics and ejection forces of parts.The warm compaction process capability is discussed in terms of stability of powder flow rate and apparent density,compacting pressure and temperature as well as weight and density of pressed parts.