A densification equation derived from the stress-deformation analysis of uniaxial cold compaction of metal powder mixes

ABSTRACT

A new densification equation for uniaxial cold compaction of four low alloy steel powders was determined from the deformation vs. mean axial stress correlation. Both deformation and stress are averaged along the height of the powder column. A power law relation, with two parameters representing the plasticity and the inverse of the resistance to deformation (densification) of the powder mix, respectively, fits the curves that are divided in two steps, distinguished by the prevailingdeformation/densification mechanism (rearrangement or plastic deformation).

Densification of the four powder mixes is greatly affected by the starting density in the die cavity, while the chemical composition of the base iron powder has a less significant effect.

KEYWORDS:

• Cold compaction
• densification
• deformation

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Alberto Molinari received the Ph.D. degree in Metallurgical Engineering in 1986 from Torino technical University, Italy. He is currently a full professor of the Department of Industrial Engineering, Trento University. His main research activity is devoted to the study of mechanisms of cold compaction and of sintering of metallic powders, to mechanical and wear properties of sintered steels, to the application of AM in medical industry. He received Honor Ph.D. by University Carlos III, Madrid in 2016 and is Fellow of EPMA.

Ilaria Cristofolini received the Ph.D. degree in Metallurgical Engineering in 1995 from Padua University, Italy. She is currently associate professor of the Department of Industrial Engineering, Trento University, in the field Design methods for industrial engineering. Her main research activity is devoted to the study of design methods for powder metallurgy, to design methods against wear, to PM parts geometric dimensioning and tolerancing.

Gianluca Pederzini was born in Bologna in 1980 and holds a Master of Science Degree in Mechanical Engineering and a Master in Technology and Innovation Management, both received from University of Bologna in Italy. He is employed in SACMI since 2007, where he is currently responsible for the development of powder metal presses, as well as cold forging and refractory presses.

Alex Rambelli received the degree in Mechanical Engineering in 2008 from Bologna University, Italy. He currently works for the technical department of Sacmi Imola S.C., Italy. His main activity is related to the development of industrial hydraulic presses for powder metal, for metal sheet cold deformation and for refractory materials.