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MIL-H-6875H
AMENDMENT 1
16
July 1993
MILITARY SPECIFICATION
HEAT TREATMENT OF STEEL, PROCESS FOR
This amendment forms a part of MIL-H-6875H, dated 1 March 1989,
and is approved for use by all Departments and Agencies of the
Department of Defense.
PAGE 4
3.1.1.1: For “Nitrogen”,
under the “Class D“ column, delete “No” and substitute
“X 10/”, and add a new footnote:
—
“10/ The use of a nitrogen atmosphere shall be limited to heat treating
—
temperatures of 1400”F and below.
A nitrogen atmosphere may be used for
heat treatment above 1400”F provided a minimum of 0.020 Inches of metal is
subsequently removed from all surfaces of heat treated material.”
3.1.1.1: For “Vacuum”,
under the “Class D“ column, add “JJ/” next to the “X”,
and add a new footnote:
“~/ Nitrogen is not permitted as a partial pressure above 1400*F. Nitrogen
may be used as a backfill quench for vacuum heat treatments performed at
or below 1925aF.”
PAGE 20
Footnote 12/:
Delete and substitute:
—
“Coollng In alr or other gases Is optional for small parts up to, and including,
0.250 Inches In thickness.
For 440C, cool to -90°F or Iowerlmmedlately after
quenching and before tempering and soak for 2 hours minimum; the delay between
quenching and sub-zero cooling shall not exceed 1 hour.”
AMSC N/A lof2
FSC 95GP
Distribution Statement A. Approved for public release; distribution Is unlimited.
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