The Porosity-Pressure Curve and its Relation to the Pore-Size Distribution in Iron Powder Compacts

  • Gerhard Bockstiegel


Porosity-pressure curves obtained from isostatic compacting as well as from ordinary die-compacting of pure and carburized iron powders are found to be in disagreement with the popular formula suggested by Konopicky and by Shapiro and Kolthoff. Torre’s model of the hollow sphere, designed to lend theoretical support to Konopicky’s formula, is criticized and recalculated. The pore-size distributions of compacts made at varying pressures are assessed by microscopic lineal analysis. The accumulated porosity function, calculated from the pore-size distribution, proved to be of the logarithmic-normal type. The porosity is found to be related to the logarithm of the diameter of the largest pores through a function closely approximating the complementary error function. The relation between the largest pore diameter and the compacting pressure cannot be described by a straight line in either log-linear or log-log coordinates. With increasing compacting pressure, the pores seem to be eliminated strictly size by size—the largest pores disappearing at the lowest and the smallest pores at the highest pressure.


Hollow Sphere Iron Powder Chord Length Porous Body Lineal Analysis 
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Copyright information

© Metal Powder Industries Federation and The Metallurgical Society of AIME 1966

Authors and Affiliations

  • Gerhard Bockstiegel
    • 1
  1. 1.Höganäs-Billesholms AktiebolagHöganäsSweden

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