Bulk Properties of Powders
ASM Handbook, Volume 7: Powder Metal Technologies and Applications Copyright © 1998 ASM International® P.W. Lee, Y. Trudel, R. Iacocca, R.M. German, B.L. Ferguson, W.B. Eisen, K. Moyer, All rights reserved. D. Madan, and H. Sanderow, editors, p 287-301 www.asminternational.org DOI: 10.1361/asmhba0001530 Bulk Properties of Powders John W. Carson and Brian H. Pittenger, Jenike & Johanson, Inc. THE P/M INDUSTRY has grown consider- Bulk Properties. One of the main reasons that and flow rate) result in a method that does not ably in the past decade. As a result of this powder flow problems are so prevalent is lack of measure either one very well. growth, more critical components in the automo- knowledge about the bulk properties of various Apparent Density or Tap Density. Neither of tive, aircraft, tooling, and industrial equipment powders. For many engineers, the name of a these parameters, nor their ratio (the Hausner industries are being considered for manufacture powder, such as atomized aluminum, is thought Ratio), is a direct indicator of powder flowabil- using this technology: This is placing increas- to connote some useful information about its ity. They do not, for example, assist in sizing ingly stringent quality requirements on the final handling characteristics. While this may be tme hopper outlets or calculating appropriate hopper P/M part. Variations in part density, mechanical in a general sense, it is not a reliable tool. Unfor- angles. properties including strength, wear, and fatigue tunately, major differences in flowability often Free-Flowing versus Nonfree-Flowing. Whether life, as well as in aesthetic appearance and di- occur between different grades and types of or not a metal powder is considered free-flowing mensional accuracy are no longer tolerated.
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