Higher Green Strength and Improved Density by Conventional Compaction

A new material system that can produce very high green strength and green density has been developed for conventional compaction processing. The system, which uses a zincless lubricant, is based on the optimization of the bonding mechanism and binder chemistry. This approach permits the bonding of copper particles in a FC-0208 mix. Examples of the binder-treatment of FN-0208, Ancorstee145P, and Ancorstee150 HP are also included. Introduction Continuous improvements have been made in ANCORBOND® (binder-treated) premix technology. The benefits of using binder-lubricant treated and binder-treated mixes are substantial improvements in flowability, segregation resistance, green strength and compressibility1,2,3. More recently, developments in the technology have led to an even stronger capacity to bond elemental powders such as copper. Using a systems approach to optimize the binder and premixing process, the green strength of bonded mixes has been improved over 50%4. These developments have positive impacts on the sintered properties as well as the green properties. This paper will review these recent developments. The original binder-treated premixes required lubricants to be admixed to the premix. In this first generation, the binder acted solely as a binder. It did not exhibit lubricity enhancements measured in terms of the pressure required to strip and slide parts out from a die. Friction measurements during powder compaction studies showed the importance of a good quality lubricant5. The binder did improve die fill or flowability and segregation resistance resulting in more consistent compacts relative to unbonded mixes. The second generation of binder-treated premixes utilized a binder that also acted as a lubricant. The improvements in compressibility were evident at higher compaction pressures. The binder lubricant treatment reaped the benefits of the original treatment while adding to it increased compressibility, and equivalent or better lubricity. The third generation of binder-treated premixes incorporated a systems approach to develop ANCORDENSE® or warm compaction technology6. This method involves investment in peripheral powder heating equipment to warm compact the bonded mix and achieve a substantial improvement in properties. Recent developments in bonding mechanisms and binder chemistry have yielded properties a level beyond the first and second-generation ANCORBOND products. Two systems will be discussed in this paper; the improved ANCORBOND and the ANCORBOND PlusTM engineered materials. Both systems are designed for conventional compaction and do not require the use of peripheral heating equipment as would be needed with ANCORDENSE processing. ANCORBOND and ANCORBOND Plus induce a much higher green