MIL-DTL-12560K (MR)
4.8.2.1 Hardness tests for thin gauge. For plates less than 0.187 inches (4.75 mm) in thickness, a
Brinell hardness test shall be conducted in accordance with ASTM E10 using a 5 mm carbide
ball and a 750 kilogram load or a 10 mm carbide ball and a 1500 kilogram load.
4.8.2.2 Hardness tests for impact test specimens. Samples for all classifications shall be
examined on a lot by lot basis. Except as provided in 4.8.2.2.1, each sample from which impact
test specimens are taken shall have a hardness check made upon it as follows: For samples 0.098
to 0.500 inch inclusive at least one hardness check shall be made on the surface. For samples
greater than 1/2 inch up to 4 inches (inclusive) in thickness, at least two hardness tests shall be
taken from an adjacent location, midway between the surfaces of the plate. For samples of 4
inches in thickness or greater, at least six hardness tests shall be made at equal intervals across
the plate thickness.
4.8.2.3 Hardness traverse test. Prior to production to assure compliance to paragraph 3.2.11.2,
the size of the heat affected zone for thermally-cut edges shall be determined by taking hardness
tests at 1/16 inch increments from the edge. Surface scale and decarburization shall be removed
from the test surface. The distance at which there is no change in surface hardness shall be
considered the depth of the heat affected zone. The contractor shall document the test results for
each thickness and thermal cutting method used in production. The contractor is also responsible
for documenting all heat input controls to assure the cutting process is under control. Re-
verification of heat affected zone size for subsequent production lots is not required provided
there is no change in the cutting method or heat input from that previously tested. The records
shall be available for review by the cognizant government representative.
4.8.3 Charpy V-notch impact tests. Three (3) Charpy V-notch impact test specimens per
direction for a total of six (6) Charpy V-notch impact specimens shall be taken from the sample
and shall be prepared and tested in accordance with ASTM E23 and ASTM A370. Charpy V-
notch impact test specimens shall be taken in both the transverse (TL) orientation and
longitudinal (LT) orientation from each sample as obtained in accordance with 4.8.3.1 or 4.8.3.2,
and shall be prepared and tested in accordance with ASTM E23 and A370. The largest
attainable sub-size Charpy V-notch impact test specimens shown in Figure 7 of ASTM E23 shall
be used.
4.8.3.1 For samples less than 4 inches in thickness. Charpy V-notch impact test specimens from
samples less than 4 inches in thickness shall be taken in both the transverse (TL) orientation and
longitudinal (LT) orientation (see 3.2.7.2) from a location midway between the top and bottom
surfaces of the plate and at least 4 inches or 2T, whichever is less, from any quenched edge as
well as outside the heat-affected zone of any thermally-cut edge. When the amount of materials
available is insufficient to obtain standard specimens, the largest attainable sub-size Charpy V-
notch impact specimens shown in Figure 4 of ASTM E23 shall be used and the results compared
to the applicable requirements of Table IV. There are no Charpy V-notch impact test
requirements for plates less than 0.140 inches thick.
4.8.3.2 For sample 4 inches or greater in thickness. Charpy V-notch impact test specimens from
samples 4 inches or greater in thickness shall be taken in both the transverse (TL) orientation and
longitudinal (LT) orientation approximately 1 inch below the surface of the plate and at least 4
inches from any quenched edge as well as outside the heat-affected zone of any thermally-cut
edge.
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