BiPolarMoment
Mechanical
- Mar 28, 2006
- 621
Chemical requirements of UNS17400 per ASTM A693 changed such that previously (rev -13) a limit of Ta+Nb of 0.15-0.45 was the acceptable amount. In the newest revision (-16) they have removed tantalum entirely and list only Niobium 0.15-0.45. In a theoretical context of Ta=0.00... these two are equivalent.
However, per ASTM A480 6.2.2 the fact that Tantalum is no longer a listed requirement means that material with trace amounts don't have to have it measured or reported and even if it is reported is not basis for rejection. So in a theoretical case where Nb=0.450... and Ta=0.001 this is satisfactory to revision -16 but not -13 (>0.45). The likelihood of this seems minute but on the other hand ASTM provides no rationale in the summary of changes of the revision.
Furthermore, some other standards that use the same material have not been revised (yet) to include this change (e.g. A564)
Any thoughts?
However, per ASTM A480 6.2.2 the fact that Tantalum is no longer a listed requirement means that material with trace amounts don't have to have it measured or reported and even if it is reported is not basis for rejection. So in a theoretical case where Nb=0.450... and Ta=0.001 this is satisfactory to revision -16 but not -13 (>0.45). The likelihood of this seems minute but on the other hand ASTM provides no rationale in the summary of changes of the revision.
Furthermore, some other standards that use the same material have not been revised (yet) to include this change (e.g. A564)
Any thoughts?
