Measuring Particle Size Average or “Fisher number” of Metal Powders

Metal powders are used in a wide variety of applications.  Many of the items we use on a daily basis include parts molded using metal powders.  One parameter to control the quality of the metal powders is particle or powder size, typically in the form of an average value or “Fisher number.” 

A common metal powder sizing technique is by air-permeability which gives an average size.  Traditionally, a Fisher Model 95 Sub-Sieve Sizer (FSSS), with a particle size range of 0.5 to 50 µm, has been used to get this average size value, or “Fisher number.”  Using this technique is the basis for ASTM Standard B330-12, “Standard Test Methods for Estimating Average Particle Size of Metal Powders and Related Compounds Using Air Permeability” as well.  Since the FSSS has been discontinued, industry has been clamoring to find an alternative to technique or device that gives the same results and agrees with all the historical data collected on the FSSS.

HEL’s Subsieve AutoSizer (SAS) distributed by Particulate Systems, a Micromeritics Brand, is now available to collect particle size data of metal powders using the air-permeability technique.  Developed as a direct and improved successor to the widely used FSSS, HEL has improved on the Fisher’s performance and brought the technology to the 21st century by offering easy to use automated functions together with electronically recorded data. 

By design, the SAS successfully generates “Fisher number” results identical to that of its predecessor (the Fisher FSSS).  The SAS’s objective is to produce the same value and is not intended to be “better” or “more accurate”  This is a crucial point as the FSSS is still used as a benchmark in many industries. Simultaneously, historical data goes back decades and now the HEL SAS is available for comparison purposes going forward.

The SAS has a particle size range of 0.2 to 75 µm and has been recently approved and added to ASTM Standard B330-12.

For more information on the HEL Subsieve AutoSizer (SAS) and a comparison study with the Fisher Model 95 Sub-Sieve Sizer (FSSS), please click here.