 |
|||
|
|
|||
| ||||||||||
|
|  MIL-P-18682D(SH)
A certificate of compliance with ASTM A 744 shall be provided. In addition,
certification of the chemical test results for each heat of material and
the specific heat treatment (including temperature and holding time) to
which each casting was subjected shall be provided. The time between
removing the stainless steel part from the furnace and quenching shall be
minimized. This certification shall list both chemical test result values
and the corresponding acceptance criteria valve specified in ASTM A 744.
Repair welding shall be accompanied by post-weld heat treatment in
accordance-with ASTM A 744 (see 6.2.2).
All nickel-copper-aluminum alloy parts shall be annealed prior to age-
hardening except parts for which a hardness greater than 265 BHN is required.
For submarine pumps, sleeves which are a seat for O-rings where movement
occurs, e.g., under mechanical seals which are spring loaded, shall be
nickel-copper alloy that is weld clad with Ni-Cr-Mo-Cb alloy. The area to
be weld clad shall be minimized. Cladding shall extend a minimum of
3/16 inch deep in the final machined condition. Deposit shall be made by
a minimum of two passes. The filler weld material shall be as follows:
Covered electrode in accordance with MIL-E-22200/3 (MIL-1N12), or bare wire
in accordance with MIL-E-21562 (MIL-EN625). Machining into the first
(lower) layer for the final surface shall not be permitted. The final
machined surface of the cladding shall be PT inspected. The acceptance
standard shall be class I of NAVSEA 0900-LP-O03-8000. The surrounding
areas shall be inspected in accordance with MIL-STD-278.
Sleeves that are subject to wear or that establish a critical clearance (i.e.,
less than 40 roils radial clearance) shall be made of nickel-copper-aluminum
alloy and shall meet the 265 Brinell minimum hardness specified in the table.
Sleeves for which footnote 8 requires weld cladding shall be made of nickel-
copper alloy. Other sleeves shall be made of either: (a) nickel-copper-
aluminum alloy meeting the annealing requirement of footnote 7 rather than
the above hardness requirement or, (b) nickel-copper alloy.
Special high lead bronze or other suitable bearing materials may be used
subject to review by the design agency. Bearing metal, alloy B-10, is an
acceptable alternative material.
When the mechanical properties of the material used in the fabrication of
a part are altered by metal working processes or heat treatment, sample
material from each lot of material, as defined in the material specification,
shall be subjected to tensile tests in the final heat treated condition for
the part. As a minimum, tensile tests shall determine ultimate strength,
yield strength, percent reduction in area, percent elongation and hardness.
The tensile tests shall be conducted on test samples machined from the heat
treated material or from a piece of parent stock which had been heat treated
in the same batch in the lot processed at the same time. The tensile test
requirements and acceptance criteria for mechanical properties shall be
included on the part drawing. Acceptance criteria for the mechanical
properties shall be in accordance with the material specification or as
approved by the design review agency. In no case shall ductility of less
than 10 percent elongation in 2 inches be allowed.
Where nickel-aluminum-bronze is used, it will be in accordance with alloy
632M of QQ-C-465 and its amendment.
22
|
|
Privacy Statement - Press Release - Copyright Information. - Contact Us |
Click
here for thousands of PDF manuals