PROCESS PROPERTIES OF GAS-ATOMIZED AND GROUND FINE MIXTURES OF HIGH-SPEED STEEL POWDERS

Abstract

The influence of ground R6M5K5 tool steel powder combined with gas-atomized powder on the process properties of the powder mixtures was studied. Both powders were sifted through a 50 μm sieve. The ground powder was present in amounts of 0, 10, 20, 30, 40, 50, and 100%. The bulk density, tapped density, flowability, and repose angle of the powder mixture were determined. Additionally, the Carr index, Hausner ratio, and flow rate were calculated. The bulk density hardly changed because of a high content of near-spherical particles in the ground powder. The flowability of the mixture decreased with increasing content of the ground powder (the flow time for the standard weighed sample increased). Grinding the powder resulted in deterioration of its flowability by nearly 35%. The flowability of the gas-atomized powder was 22.49 sec/50 g. When the mixture contained 50% ground powder, the flowability was 25.72 sec/50 g, i.e., decreased by 14%. The linear approximation of dependencies for the bulk density (BD), flowability (t), and flow rate (V) on the content of the ground powder (weight percent) combined with the gas-atomized powder (X) provided the following results with a high coefficient of determination (R² ): BD = 4.52 – 0.0043X (R² = = 0.98); τ = 23.48 + 0.07X (R² = 0.95); V = 36.32 – 0.012X (R² = 0.97). The linear dependence of the relative bulk density (expressed in percent) on the content of the ground powder demonstrated that the effect from the amount of the ground powder can be assessed using the slope angle of the dependence to the abscissa axis. The slope angle of the dependence is less than 1 deg, indicating a very weak effect of the ground powder content on the relative bulk density of the powder mixtures considered.