Warm die compaction of low alloy steel powder mix – Compaction mechanics and densification

Powder behavior in uniaxial cold compaction has been extensively investigated in previous work. The constitutive model of different powder mixes has been derived, and the influence of several variables, such as geometry, chemical composition, lubricant type and amount etc., has been studied in depth. This work focuses on the influence of warm die compaction. A commercial diffusion bonded low alloy steel powder, added with 0.6% wt. lubricant, has been used producing cylindrical specimens with two different H/D ratios, both in cold and in warm die compaction. Concerning warm die compaction, two different lubricants have been added. The constitutive model and the densification curves have been derived for all the powder mixes using the data recorded by the press, in terms of forces and displacements. Comparing ejection force and energy, the influence of warm die compaction, type of lubricant, and height of the specimens have been highlighted.