1、NOTE: MIL-STD-276 has been redesignated as a Design Criteria Standard. Thecover page has been changed for Administrative reasons. There are no otherchanges to this Document.MIL-STD-276A30 DECEMBER 1992_SUPERSEDINGMIL-STD-2762 FEBRUARY 1956(See 6.4)AMSC N/A FSC 9540DISTRIBUTION STATEMENT A. Approved
2、for public release; distribution isunlimited.NOT MEASUREMENTSENSITIVEDEPARTMENT OF DEFENSEDESIGN CRITERIAIMPREGNATION OF POROUSMETAL CASTINGS AND POWERED METALCOMPONENTSProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-MIL-STD-276AFOREWORD1. This militar
3、y standard is approved for use by the Naval Sea SystemsCommand, Department of the Navy and is available for use by all Departments andAgencies of the Department of Defense.2. Beneficial comments (recommendations, additions, deletions) and anypertinent data which may be of use in improving this docum
4、ent should be addressedto: Commander, Naval Sea Systems Command, SSA 05Q4, 2531 National Center Bldg 3,Washington, DC 20362-5160 by using the self-addressed Standardization DocumentImprovement Proposal (DD Form 1426) appearing at the end of this document or byletter.iiProvided by IHSNot for ResaleNo
5、 reproduction or networking permitted without license from IHS-,-MIL-sTD-276ACONTENTSParagraph 1.1.11.21.2.11.2.21.2.32.2.12.1.12.23.4.4.14.2b.3rb.3.l.5.3.24.3.3li.f44.4.14.6.26./$.36.4.44.54.5.16.5.26.66.74.84.94.10SCOPE .Scope .Applicabil icyAuthorization .Restrictions on use of filled sodium siim
6、pregnants Prohibitions on impregnncing. . . . . . . . . . . . . . . . . . . . . . 1. . . . . . . . . . . . . . . . . . . . . 1.1.1icate.1. . . . . . . . . . . . . . . . . . . . . 1APPLICABLE DOCU!4ENTS.2Government documents 2Specifications, standards, and handbooks. .2Order of precedence .2DEFINITIO
7、NS .2GENERAL REQUIREMENTS .2Preliminary test for pressure tightness. 2Materials .3Preparationof castings for impregnation3Preliminary operations3Cleaning3Surface preparation.3Impregnatingmethods3llethodA - internal pressure (individual cascings) 3!lechodB - dry vacuum and pressure (batch immersion)
8、3IlethodC - wet vacuum and pressure (batch immersion) 4Impregnation procedure rescriccions. 4Post-impregnation troac.ment.4Rinsing .6Curing process 4Lsokage .4Discoloration .4!+nrking.6Resporrsibilityfor lrrspection.6Proof prassure cesc.54. 10.1 Proof pressure cescmechod. . . . . . . . . . . . . . .
9、 . . . . . . . . . . . . . . . . .54 .10.2 Alternate proof pressure test method . . . . . . . . . . . . . . . . . . . . . .54 .10.3 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54.11 Reimpregnatirm . . . . . . . . . . . . . . . . . . . .
10、. . . . . . . . . . . . . . . . . . . . . . . .55. DETAILED REQUIRSMZNTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56. NOTES 56.1 Incended use56.2 Issue of DDOISS 56.3 Subjecc cerm (keyword) listing.66.4 Changes from previous issue.6Appendix Documents forobcaining waive
11、rs 7iiiProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-IIIL-STD-276A1. SCOPE1.1 - This standard covers the requirements and tests Eor theimpregnation of structurcrlly sound castings and powder metal components in aluminum,magnesium, copper, iron, (excl
12、uding steels) and zinc alloys. Components for Navalservice shall be shovn to be struccurnlly sound in accordance with NIL-STD-278. Icis also applicable co test specimens used for evaluating impregnating materials inaccordance with IIIL-I-17563.1.2 19vrlicabili1.2.1 Authorizetiou Components shall be
13、impregnated or reimpregnated inaccordance wfth this standard when authorized by NAVSSA for Naval applications andby the end user for other applications. When impregrracionor reimpregnacion is nocspecifically authorized, but is deemed necessary co satisfy performancerequirements, n waiver may be obta
14、ined in accordance with MIL-STD-480 or flIL-STD-L81(see appendix) . Impregnation should only be permitted in the following situationswhen ic is agreed upon between the impregnator and the end user.(a) When components are to be exposed co fluids ocher than those tested forcompaclbilicy with che impre
15、gncctingmaterial in accordance wLchIiIL-I-17563.(b) When impregnating a75crterialsocher than those specified in .4.2are used.(c) When impregnating methods ocher than those specified-in 6.4 are used.1.2.2 Restrictions on use of filled sodium silicace im9remrincs . Filledsodium silicate impregnancs sh
16、all noc be used unless all of che following conditionsare applicable:(a) Measured leak rates are less than O.75 cubic inches of air per second(750 cm per minute).(b) The maximum service temperature of the casting is 250 degreesFahrenheit or below. (Temperatures co 80D”F are acceptableprovided the im
17、pregnant is seep cured to che maximum servicecemperncure. )(c) HinimrunDrying Time at mubienc temperature shccllbe 68 hours. Oryingtime may be conducced at 175-200”F for 2 hours followed by polymerizingac the specified oparncing cempertrcure.(d) Castings shall noc be used in concact with concentrzcc
18、ed acid orhydrogen peroxide.(e) Specific gravity of the uncured filled sodium silicate impregcwrntshallbe 28 degrees Eaume minimum.1.2.3 Rrohibicions on imoremmc Impregnation shrillnot be performed underany circumstances in the following situations:(a) When castings are to be exposed to temperncures
19、 grenr.erchccnthea75aximum specified in IIIL-I-17563 for the specific impregnanc usedexcept for sodium silicaces properly cured as shovn above.(b) When castings are to be exposed to oxygen gas at any pressure. (Sincesodium silicace is cocally inorganic, it can be used in contacc withoxygen.)1Provide
20、d by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-MIL-sTD-276A(c) When castings must be welded after impregnation during fabrication.(d) When castings exhibit rejectable structural defects as defined by thespecified radiographic standards.Waivers shall not be g
21、ranted for these applications2. APPLICABLE DOCUMENTS2.1 Government documents2.1.1 Srrecifications. standards and handbooks. The following specifications,standards, and handbooks form a part of this document to the extent specifiedherein. Unless otherwise specified, the issues of these documents are
22、those listedin the issue of the Department of Defense(DODISS) and supplement thereto, cited inSPECIFICATIONSMILITARYMIL-I-17563 -I STANDARDSMILITARYMIL-STD-278 -MIL-STD-480 -MIL-STD-481 -ImpregnancsIndex of Specifications and Standardsthe solicitation (see 6.2)for Aluminum, Copper, Iron,Magnesium an
23、d Zinc Alloy CastingsWelding and Casting Standard.Configuration Control-EngineeringChanges, Deviations and Waivers.Configuration Control-EngineeringChanges (Short Form), Deviations andWaivers(Unless otherwise indicated, copies of federal and military specifications,standards , and handbooks are avai
24、lable from the Standardization Documents OrderDesk, Bldg. 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094. )2.2 Order of Precedence. In the event of a conflicc between the text of thisdocument and the references cited herein, the text of this document takesprecedence. Nothing in this documenc, h
25、owever, supersedes applicable laws andregulations unless a specific exemption has been obtained.3. DEFINITIONS - This section is not applicable to this standard.4. GENERAL REQUIREMENTS4.1 Preliminirv test for pressure tihtness. Components which have beenthoroughly cleaned and completely machined sha
26、ll be subjected to the hydrostatic oraerostatic pressure required by the applicable drawing or directive, or as specifiedin 4.10. If pressure tests are made on components before final machining andthreading of bolt holes , the components shall be retested after final machining andbefore impregnation
27、. Components which leak through the wall during this test may berepaired by impregnation provided they meet all the requirements of 1,2.2Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-MIL-sTD-276A6.2 Materials. The materials used co impregnate compone
28、nts shall confocm toMIL-I-17563 unless filled sodium silicate can be shovn to be a suitable alternativeby shoving all the restrictionsof 1.2.2 have been a75et.6.3 Pre9eration of castins-sfor imvretmurtion&fb.3.l ?relimi arvn overircions. Unless otherwise specified, all heat treating,welding, brazing
29、, and a75achining operncions shall be performed prior to impregnation.Surface finishing shall be performed nfcer impregnncing.6.3.2 Cleani& Components shall be thoroughly cleaned free of oils andother mschining compounds. Components after water rinse shall be dried by heatingto 150 to 18D”F for a a7
30、5inimum of one hour and shall be brought to ambienttempericturebefore impregnocing, if vapor decreasing is used for cleaning, no dryingis necessary.4.3.3 Surfsce Premracion. Rough magnesium castings shall be created toremove surface skin to a depth of approximately 0.002 inches by mechanicaltreacmen
31、c.4.4 mpremacinc mechods. Impregnation shall be by one of the followingmethods nc the discretion of the contractor.h.h.l Method A - internal r.ressure(individual castings) . !ethodA involvesusing the casting itself as che pressure containlccgvessel and can only be done onone casting at a time. It is
32、 primarily applicable co large castings. All of cheopenings in the cascing, excepc for pores for the impregnant shall be plugged. Theimpregnant shall be injected into che cascing until ic is completely filled, orshall be circulated through che casting under pressure. Pressure from 50 co 75pounds per
33、 square inch (lb/in2) above prescribed test pressure shall be applied (iffactor of safety of the cascings will permi.c). This pressure shall be maintaineduntil the liquid is observed seeping through the pores or, in che case of extremelyfine porosity where the liquid may not come noticeably co the o
34、utside surface, thelength of time to hold che pressure shall be determined empirically. Loss ofsolution by seepage may be stopped by spot curing, cccrebeing taken noc to heat checastings to the cure cemperocure over n larger volume than is co be cured. In casesof minute porosity in heavy walls, 6 ho
35、urs or more under pressure may be required toeffecc complece penetrirtion of che solution through the wall.4.6.2 Method B - drv vacuum and pressure (batch immersion) . Hethod Bicwolves evncuatinz the components porosity to remove air, writer,and other foreigna75aterial turdintroducing the impregnant
36、 under pressure. The clean and drycomponents shall be placed in an empty pressure vessel. The vessel shall then beclosed and the air evacuated until n vacuum of not less than 29 inches of mercuryattained. If the vapor pressure of che impregcumt solution prohibits using aminimum vacuum of 29 inches o
37、f mercury, the mmximum vacuum comptrciblewith thesolution shall be used, buc shall not be less than 27 inches of mercury. Theimpregnating solution shall be drawn into the tank at such a rate chat the abovespecified vscuum is maintained. When che tank contains a sufficiencyamount ofissolution to cove
38、r the components to a level of atatmospheric or greater pressure shrill be opplied.lensc 2 inches above che Load,AfCr a period of time which has3Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-been determined empirically. Thesolution, and the parts rem
39、oved.required to determine penetrationMIL-STD-276Apressure shall be released, the tank emptied ofSecticming of actual parts or samples may be4.4, 3 Method C - wet vacuum and Dres.sure (batch immersion) The componentsshall be placed in a pressure vessel containing the impregnating solution. Eachitem
40、shall be submerged until it is covered by at least 2 inches of impregnatingsolution. The vessel shall then be closed and the air exhausted until a vacuum ofnot less than 29 inches of mercury is attained. The vacuum shall be maintained fora period determined empirically to be sufficient for complete
41、air removal. At theend of the vacuum cycle, a Pressure of nOt less than 50 pounds per square inch shallbe applied for a period shown by experience to be sufficient for complete porositysealing. The pressure shall then be released and the castings removed from thesolution. For components with a wall
42、thickness not exceeding 1/2 inch, the pressurecycle may be omitted.4,4.4 Impregnation procedure restrictions4,4,4.1 Sodium silicace. Impregnation with sodium silicate shall be permittedonly by Methods A or B.4.4.h.2 Hazardous wastes, All hazardous waste generated by this process ,shall be disposed o
43、f in accordance with local and federal regulations6.5 Post-imprecation treatment.4.5.1 RinsinP. The parts shall be well drained and the surface , includingducts, vents , and pockets , thoroughly rinsed in aqueous solution to remove excessimpregnant. A corrosion inhibitor additive may be added to the
44、 final rinse water.4.5.2 CurinE urocess The components shall be cured in accordance with theimpregnant solution manufacturer s instructions4.6 Leakae. Impregnation shall be accomplished co the extent that the itemsdo not leak under proof tests described in 4.10.1.4.7 Discoloration, Discoloration whi
45、ch does not affect the quality ofimpregnation or the serviceability shall not be cause for rejection of the castingor powder metal component,4.8 Markin. Each component which has been impregnated shall be marked “IMP-,on the stamping pad or in a conspicuous place that will not impair its strength ors
46、erviceability. Marking shall be by low stress die stamps or vibrotool engraving,4.9 Resuonsibilitv for inspection. Unless otherwise specified in the contractor purchase order, the contractor is responsible for the performance of allinspection requirements (examinations and tests) as specified herein
47、. Except asotherwise specified in the contract or purchase order, the contractor may use hisown or any other facilities suitable for the performance of the inspectionrequirements specified herein, unless disapproved by the Government. The Governmentreserves the right to perform any of the inspection
48、s set forth in this specificationwhere such inspections are deemed necessary to ensure supplies and services conformto prescribed requirements4Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-MIL-STD-276A4.10 proof vressure test. Erichcomponent shall be
49、 subjected to the pressuretest, either hydrostatic or aeroscacic, in accordance with the applicable drawings,directives, or specifications. If che applicable drawings, directives, orspecifications do noc specify the proof pressure or ocher testing requirements, therequirements of 6.10.1 or 4.10.2 shall apply, In the event machining is necessaryafter impregnncion, the final pressure test shall be
