MIL-A-21180D
Class 4 castings - Sample size shall be selected in accordance with the table for Class 3
castings of MIL-STD-2175, and be completely examined, unless radiographic
examination is waived in the acquisition documents (see 6.2.1).
Sampling shall remain at these levels until 10 casting lots of the part, produced consecutively,
show compliance with soundness requirements. Once this condition is satisfied, inspection levels
may be reduced to those levels specified in MIL-STD-2175, as applicable to class number.
4.4.2.4 Sampling for mechanical properties.
4.4.2.4.1 Lot sampling for castings. In the event that a casting radiographed according to
4.5.2 shows borderline soundness according to 3.4.2.2, that casting shall be among those
subjected to the test specified in 4.5.4 together with other castings selected at random from the
same lot. From such a casting, specimen blanks for test shall be removed in accordance with the
directions of the purchaser. For the first 10 casting lots of a part produced following foundry
control approval, the number of castings in the samples shall conform to the applicable sample
size code letters listed under Inspection Level S-3 of MIL-STD-105, with an Acceptance Number
Zero, and a Rejection Number 1. Sampling shall conform to the foregoing sampling plan until 10
casting lots of the part, produced consecutively, have been sampled and tension-tested, and have
demonstrated properties complying with those specified herein. Once this condition is satisfied,
samples may be sized in accordance with Inspection Level S-2 of MIL-STD-105, with an
Acceptance Number Zero, and a Rejection Number 1.
4.4.2.4.2 Locations of specimens for tension tests. Following heat treatment, castings shall
have test specimen blanks removed from locations shown on drawings, or as specified elsewhere
in the acquisition documents (see 6.2.1). If no location is specified, three specimens shall be
excised from a thick, medium and thin section of each casting selected at random and as approved
by the purchaser. With the approval of the purchaser, test bars cast integrally with the casting
may be tested in lieu of testing the casting itself, provided that the casting is too small for either
excising test coupons or testing of the casting as a whole, and that the thickness of the test bars is
equal to or greater than the thickness of the portions of the castings to which the bars are
attached. Test bars shall not be removed from the casting until all heat treatments have been
completed, unless the bars interfere with inspection processes or straightening whereupon they
may be removed after solution heat treatment, but must accompany the associated casting during
precipitation heat treatment.
4.4.2.4.3 Lot sampling for large castings. Where the size of a casting precludes obtaining a
sample (over 100 pounds poured weight) from a single heat, integrally cast test bars from each
casting in the lot shall be tested with an Acceptance Number Zero and a Rejection Number 1. Lot
sizes greater than eight shall be sampled in accordance with Inspection Level S-3 of
MIL-STD-105, with an Acceptance Number Zero and a Rejection Number 1. The Inspection
Level shall remain S-3 until ten casting lots of a part, produced consecutively, have been sampled
and tension-tested, and have demonstrated properties complying with those specified herein.
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