HOT FREE FORGING OF IRON-BASED POWDER PELLETS

Abstract

The manual forging of cylindrical powder pellets of small (8.0–8.5 g) weight, pressed at 700 MPa from mixtures of iron and graphite powders, was studied. The presintered pellets were heated in charcoal at 1100 °С and subjected to double-sided face forging on a heated flat anvil with a hammer with a flat striker and naturally cooled on a steel plate. The vertical setting of the forged pellets was 70–80%. Samples were cut out from the pellets for analysis. The influence of the graphite amount on the compaction process and the mechanical properties of powder materials in hot free face forging was established. The improvement in the properties of materials with a high graphite content (4 and 12%) was shown to be due to an increase in the number of sections for hot welding of iron grains. This is associated with shear deformation of the pellet material during free forging, contributing to the emergence of new iron–iron contacts. The high characteristics of materials containing 1.7% graphite are due to the action of several mechanisms in parallel: dissolution of carbon in iron, decrease in total porosity, elimination of interparticle gaps and grain refinement under shear deformation. The use of a steel shell makes it possible to significantly expand the range of powders and powder compositions without destroying them in hot forging. The combination of experimental results and analytical data allowed us to conclude that manual forging was promising for quick and cheap screening of formulations for dense powder materials.