Subsieve particle-size measurement of metal powders by air elutriation

Abstract

Parti.cle-size measurements of spheri cal metal powders by means of the Rolle r ail' an-~lyzer , usmg samples up to 40 !!;r':l-m s of I?owder, were found to be r eproducible within approx-lII~atel y ± 1 percent o~ th~ o.rt gmal weig ht of. the sample for particle diameters up to 120 microns: Th.e sepa rat ion lumts c lo~e l y approxImated t hose required by Stokes law (V = Kd2) f~)l' p~r~ICl e dlame,te rs of 5 to 20 mICrons, For particle diam eters of 20 to 70 microns, the size lumts of frac, tIOn s conformed approximately to the formula '17= [("d l.4. Wi th particles larger than 70 mICrons, the accuracy of separation was uncertain. Repl'od~cibl e res ults also were obtained wit h irregularl y s haped part icles, such a s those of electrolytIC coppe r powder , Howeve r, t he accuracy of calcu lated size limits was un ce rtain no attempt being made to check t hem by other m ethods of meaRurem ent. '