ASTM F 519 has specified the use of air melted 4340 since the initial release in 1977. This requirement was driven by the belief that air melted 4340 was more susceptible to hydrogen embrittlement than vacuum arc remelted (VAR) 4340. So, even though aircraft structure was fabricated from VAR 4340, the specimens used to certify those structures as hydrogen embrittlement free were (are) made from air melt 4340. In 2005 ASTM F07.04 Task Group WK7840 on Revising F 519-05 convened their eighth meeting. Among other topics the issue of switching from air melt to VAR was discussed. The minutes from that meeting had the following to say: In regard to the raw material ballot, many in the group felt that the callout should be changed to AMS 6414 (VAR 4340). Others felt that it was important to stay with air melt. In the end, the group decided that, in the absence of comparison data, the switch to VAR could not be made. A presentation was made during the Annual Hydrogen Embrittlement Workshop in November of 2012 showing that VAR 4340 was actually more susceptible to embrittlement than air melt. The presentation has been attached to this ballot for your review and consideration. This issue was discussed during the F07.04 business meeting of November 2012 and it was the conclusion of those present that the issue should be put to a vote via a sub-committee ballot.
Keywordscleaner; coating; delayed failure; fluids; hydrogen embrittlement; maintenance chemicals; plating/coating; steel; stress cracking; threshold;
Draft Under Development