Rationale

The Mn content is 0.50 % maximum. This was included in the original version possibly for a specific application. The reason is not evident to the SC. A638 Precipitation Iron Base Superalloy Bars, Forgings and Forging Stock for High Temperature Service has Mn at 2.00 max. So do AMS standards 5732, 5734 and 5737. This ballot is to align it with industry standards and what mills typically melt at since the lower Mn makes it a distinct chemistry that is more difficult to obtain as starting stock. The ballot is also intended to find the reason it was lowered by any objections.