Sieve test of metal powders

Abstract

R eproducible rcsu l t~ lI'ere obtained in sie l'c tests of sponge iron, electrolytic iron, electrolytic coppe r, and nickel II'hen cer tain I'a riables a ffect ing the sieving characte ristics of t he powders were c liminated o r controll ed. One of thesc was a cumulat ive sampling e rror res ul t in g from rc peated riffle cu Lting of limi ted pOII'del' s upplies. Another lI'as th e effect of expos urc of th e powder t o humid atmospheres . The eff ects of both yariables we re de monstrated in tests wi th spongc iron. Variations of co nsiderab le magnit ude wcre obscrved whe n either variable I\"aS uncontroll ed . Signifi cant va riat ions also we rc noted lI'he n the samc pOIl"(ler lI'e re sieved \\'ith different sets of cc rtifi cd sieves. These d ifJe rences were reduced considerably in magnitude when co mpa ri sons we re madc on t he basis o f the s izc of t'he ave rage ope nin g as dete rmi ned durin g the certi fi cation te ts insteacl of the nominal sie ve ope nin g. Dcve lopme nt of more effective methods for controlling these va riables or cvaluati ng the ir cr-rects would improve t he re producibilit.v of ieve tcs ts.