Rationale

The standard material for the determination of the Miller number is no longer commercially available. Revision is to propose another standard material, that can be approved in concurrence with the original standard material. The 28%Cr steel milled out of centrifugally cast cylinders, a.k.a. Miller blocks are no longer in use, the alloy has changed. No more cast cylinders can be obtained, to mill the Miller blocks from. We propose to use D2 Tool steel as alternative reference material. First tests with a D2 tool steel (complying with ASTM G65) show excellent in-lab repeatability and sufficient wear loss to be used as a replacement. A first round-robin will be organised with a limited number of volunteer labs, round-robin data will be presented at the next ASTM Subcommittee meeting.