1、MILITARY SPECIFICATION PEENING OF METALS This specification has been approved by the Naval Air Systems Command, Department of the Navy. 1. SCOPE 1.1 Scope. This specification covers procedures and require- ments for dry peening the surfaces of metals by impingement of metallic shot or glass beads fo
2、r the purpose of increasing the fatigue strength and resistance to stress corrosion cracking by inducing residual compressive stresses in specified surfaces. 2. APPLICABLE DOCUMENTS 2.1 The following documents of issue in effect on date of invitation for bids or request for proposal form a part of t
3、his specifica- tion to the extent specified herein. - Specifications Federal RR-S-366 Sieves, Standard for Testing Purposes Military MIL-S-851 MIL-S-5002 MIL-C-5541 MIL-1-6866 MIL-1-6868 MIL-A4625 MIL-G-9954 MIL-S-13165 Steel Grit, Shot and Cut Wire Shot; and Iron Grit and Shot-Blast Cleaning and Pe
4、ening Surface Treatments and Coatings for Metal Sur- faces of Weapons Systems Chemical Conversion Coatings on.Aluminum and Aluminum Alloys Inspection, Penetrant, Method of Inspection Process, Magnetic Particles Anodic Coatings for Aluminum and Aluminum Alloys Glass Beads: For Cleaning and Peening Sh
5、ot Peening of Metal Parts Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIIrP-81985 (AS) (Copies of specifications and standards required by contractors in connection with specific procurement functions should be obtained from the procuring activit
6、y or as directed by the contracting officer.) 3. REQUIREMENTS 3.1 Peening equipment. The peening equipment shall provide means for a controlled rate propelling of dry metallic shot by air pressure or centrifugal force or of dry glass beads by air pressure against the work. The peening machine shall
7、be equipped with suitable nozzles, de- flectors or baffles to direct the peening medium against the part where desired and to prevent peening of areas not to be peened. The machine shall be so designed that the part to be peened is securely fastened. Mechanical means shall be provided to move unifor
8、mly either the part or the shot stream in either translation or rotation or both during peening. This movement shall be powered by a speed device such as a synchronous motor, induction motor, differential pressure cylinder or other controlled speed devices capable of automatically replenishing and m
9、aintaining an adequate quantity of shot at all times for maximum effectiveness and consistent reproduction of required peening intensities. Series motors and single acting cylinder activating mechanism are prohibited. All work shall be moved mechanically unless manual movement is permitted by the pr
10、ocuring activity in the contact or order, 3.2 Peening material, Peening material shall be either metallic shot or glass beads. Metallic shot shall conform to MIL-S-851 as hardened cast steel (Type I), cast iron (Type 11) or stainless steel cut wire (Type III). Glass beads shall be essentially solid
11、spheres hard tempered, chemically pure crown glass and shall conform to MIL-G-9954, except for sieve analysis. Peening materials shall be capable of producing the required peening inten- sity without excessive fracturing or deformation of the particles. 3.2.1 Size. Unless otherwise specified, the as
12、-received particle size distribution of the metallic shot shall conform to the applicable tables of MIL-S-851 for both cast shot and for cut stainless steel wire. Glass beads shall range in size from 0.0024 to 6.0661 inch (0.061 to 1.68 mm in diameter. Unless otherwise specified, the particle size d
13、isbribution o the as-received glass beads shall conform to MIL-G-9954 or to Table I, as selected by the peening contractor. Unless otherwise specified, the nominal size of the peening media charged into a machine shall be at the option of the supplier. 3.2.2 Uniformity. The shot or beads shall be fr
14、ee from sharp edges and broken pieces. Cast shot shall be spherical in shape and form and shall be free as practical from elongated, angular particles. Cut wire shot shall be free from shear cracks and laps, shall not contain seams or burrs, and shall be preused or otherwise conditioned to remove sh
15、arp edges before being used for peening, and shall be spherically formed. When visually examined the maximum number of deformed cast shot shall not exceed the values stated in Table II. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-P-81985 (AS)
16、 8s Bead Sizes Through Sieves ead Size - 83 70 59 49 29 41 35 24 r Sieves shall be as specified - 1/ in RR-S-366 l 100 r r -1 100 98-100 f T i 0-8 98-100 I- i 100 98-100 - 0-8 O 100 98-100 - 0-8 O - -. - - . . OI 0-8 100 98-100 O 100 98-100 100 . . . . . - . . 100 98-100 -. _“ - - 0-8 O .“ 0-8 O Pro
17、vided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Table I - Gla Percent Passing Nominal BI . “ .- - -. - “ “_ Number - 1/ 331 I 280 I 232 1 19 7 -Y!“ 25 - 1 98-1001 100 I 30 , r8 I - 1 98-100 35 0-8 - 40 i O 0-8 45 . O - “_ - - “ “- “ “ “- “ .“ . - - -“-
18、50 i 100 .“ -t 98-100 “ “ - .“ . - “ . 0-8 O - . . -. . - 165 100 98-100 - - 0-8 “ .“ - O 70 ! 80 _.“ -_.-A I_ . _.-_ . I 98-100 100 . “ I _I_ .- i8 98-10( - 0-8 O - .- . 98 9 100 98-100 _. . _“ - . - 0-8 O Y Provided by IHSNot for ResaleNo reproduction or networking permitted without license from I
19、HS-,-,-MIGP-81985 (AS) Table II - Uniformity of Cast Shot Shot Peening Number of Area- Number (See Acceptable Square Table III) - Maximum 930 and 780 5 1 660 and 550 12 1 460 15 1 390 20 1 MIL-S-851, Deformed Shot Inch Shot Peening Number (See Table III) 320, 280, 230, MIL-S-851, Number of Acceptabl
20、e Deformed Shot - Maximum 20 Area- Square Inch 112 190 and 170 130 30 114 110 and 70 40 114 I I I 3.2.3 Shot maintenance. Equipment shall have a separator for continuous removal of broken or defect shot material during peening. Metal- lic shot shall be maintained 5n the equipment and shall not requi
21、re replace- ment until more than 20 percent by weight shall pass through the sieve size specified in Table III for the shot peening number used. When so specified, glass bead peening equipment used on unpeened surfaces shall be so arranged that no beads are returned. Glass beads used for peening ove
22、r steel shot peened surfaces shall be replaced every two hours of operation. 3.2.4 Usability. Ferrous and non-ferrous metals shall not be peened interchangeably with the same peening medium in the same machine. . Neither glass beads nor metal shot used on ferrous parts shall later be used on non-fer
23、rous parts. Table III - Uniformity of Steel Shot in the Equipment Shot Peening Number 20%“ Maximum Shot Peening Number 20% - Maximum. (See MIL-S-851, Amount Passing (See MIL-S-851, Amount Passing Tables III and IV) Through Sieve L/ Tables III and IV) Through Sieve L/ Cast shot L Cut steel Sieve Nomi
24、nal !Cast shot Cut steel Sieve Nominal wire number opening - wire number opening - inch inch 930 - 16 O. 0469 280 ow 28 45 O .O139 780 - 18 O. 0394 230 CW 23 50 O .O117 660 CW 62 20 O. 0331 190 - 60 o .O098 550 cw 54 25 0.0278 170 cw 20 70 O .O083 460 cw 47 30 0.0234 130 100 O ,0059 390 CW 41 35 0.0
25、197 i 110 - 120 O .O049 330 cw 35 40 0.0165 ! 70 - 170 O .O035 - 1/ Sieves shall be as specified in RR-S-366 I - CW 32 40 0.0165 i 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-HIL-P-8L985 HF 9777906 042332q 2 W MIGP-81985 (AS) 3.3 Preparation pr
26、ocedures. 3.3.1 Dimensions and conditions of parts. Areas of parts to be peened shall be within dimensional requirements and surface finish re- quirements before peening. Except as otherwise permitted (see 3.5.11, all heat treatments to meet requirements for mechanical properties, all machin- ing, g
27、rinding and required polishing of areas shall be completed before peening. All fillets shall be properly formed, all burrs shall be removed and all. sharp edges and corners to be peened shall be provided with suffi- cient radii to result in complete coverage without any distortion prior to peening.
28、3.3.2 Cleaning and stripping. Unless otherwise specified, all areas shall be cleaned in accordance with MIL-S-5002. Procedures for stripping coatings shall be as specified or approved in the contract or order (see 6.11 ) . 3.3.3 Masking. Areas of the part or work piece which are desig- nated in the
29、contract or applicable drawing as having critical surface finishes that must be free from peening shall be suitably masked or other- wise handled to protect such surfaces. When it is impractical to mask areas designated to be free from peening marks, sufficient stock may be provided in these areas f
30、or subsequent removal of affected material for compliance with dimensional requirements of the applicable drawings. Masking shall be optional for areas not requiring peening and whose surface finish is not critical. 3.3.4 Magnetic particle or penetrant inspection. Unless other- wise specified, where
31、 magnetic particle or penetrant inspection is required, parts shall be subgected to such inspection in accordance with MIL-1-6868 or MIL-1-6866 before and after peening. 3.3.5 Sustained stress (preload), Unless otherwise specified, peening shall be accomplished on parts or areas of parts which do no
32、t have any sustained stress as the results of fabrication. When manufacturing operations induce residual stresses which may be detrimental to service after peening, the part shall be given a suitable stress relief heat treat- ment prior to peening. 3.4 Peening procedures. 3.4.1 Peening intensity. Un
33、less otherwise specified on the drawings or in the contract. the peenine. intensity as indicated by a speci- fied a& height value shall-be aslisted in Table- IV for the thiciness- involved. If only a minimum intensity is specified, the maximum intensity should not exceed the minimum intensity by mor
34、e than 0.004A for steel shot or 0.006N for glass beads. The maximum intensity shall not cause undue warp- age of the part and shall be below the threshold of erosion of the basis material. Unless otherwise specified, for peening to intensities where the arc-height-inch is stated as A and C, metallic
35、 shot shall be used and where the arc-height-inch is stated as N, glass beads shall be used. 6 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-On h ad m $G4 lJ m I m O00 O00 uuu “am 004 999 O00 ao orl O0 O0 uuu o00 ma- O00 o00 999 moo 444 Odd O00 O00
36、 . uuc) O00 maa O00 O00 999 0 O00 uuu O00 maw 004 O00 999 wm u O u alm mal 3u a .rl al W rf al L) m a 3 c) O -2 al U .r4 3 u c) 1 d al a, U m v) m rl al .rl G U cd (D LI O d al al c) m U 3 V MIL-P-81985 (AS) 7 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
37、IHS-,-,-MIL-P-B1785 NF 7777706 Oq21126 b MIL-P-81985 (AS) 3.4.2 Coverage. Areas of parts, peened as referenced on appli- cable drawings, purchase orders or contracts, shall be peened to complete 100 percent visual coverage (see 4.2.4 and 6.10). Each portion of the critical surface shall show visible
38、 evidence of plastic flow, that is a uniform peened or hammered appearance, to indicate complete coverage and obliteration of the original surface finish as indicated by overlapping impressions. On parts having a hardness of Rockwell C50 and greater, such coverage appearance may not be apparent. How
39、ever, such parts shall show a noticeable difference in luster from an unpeened part. The length of time to achieve complete visual coverage shall be measured. Unless other- wise specified, the final operation shall last twice the time for steel shot and four times as long for glass bead shot, that i
40、s 200 percent minimum coverage for steel shot and 400 percent minimum coverage for glass shot. Coverage for holes and internal diameters shall be in accordance with Table V. Table V - Coverage for Holes and Internal Diameters Nominal Hole Ratio- Minimum Diameter- Diameter to Coverage- Inch Depth Per
41、cent 0.750 or greater I Any I 200 Less than 0,750 1 or .greater 200 Less than 0.750 I Less than 1 100 to depth of 112 I inch diameter 3.4.3 Area limitations. Unless otherwise specified, the varia- tions in boundaries of areas to be peened, when limited, shall be -0 to + 118 inch. 3.4.4 Shot selectio
42、n. The nominal shot size shall be the smallest size practical to produce the required intensity. 3.4.4.1 Fillet surfaces. If fillet surfaces on parts are required to be peened, the shot or bead size used shall be such that the nominal diam- eter of the peening medium is not greater than one-half the
43、 smallest nominal fillet radius to be peened, except that the nominal diameter of the shot need not be smaller than 0.007 inch (Shot No. 70 of MIL-S-851) and the nominal diameter of the beads need not be smaller than 0.002 inch (No. 13 size of MIL-G-9954 or No. 24 of Table I) when fillet radii of le
44、ss than twice these dimensions require peening. 3.4.4.2 Shielded areas. If the shot or beads must pass thru slots, recesses or apertures to peen required shielded surfaces, the nominal diameter of the peening medium shall not be greater than 25 percent of the diameter or width of the opening, except
45、 that limitations as to minimum shot and bead specified for peening fillets (see 3.4.4.1) shall also apply. Except as otherwise speciied or permitted, such as when shielded areas are involved, nonferrous materials shall not be peened with shot smaller than the following for the intensities given: 8
46、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-P-81985 (AS) I Intensity Shot Numbers (MIL-S-851) Types I and II r Type III (cast iron and steel) (cut wire) O. 012A ! 2 80 CW2 8 I O. 016A 390 CI.141 O, 020A 550 cw5 4 i 3.4.5 Angle of impact. The
47、nozzle or nozzles of the equipment shall be kept as nearly as possible at an angle of 90 degrees to the surface of the part being peened. Effective peening intensity will vary directly as the sine of the angle of impact. Nozzle angles approaching 45 degrees will not produce residual compressive stre
48、ss on the surface of parts. 3.5 Post-treatments. 3.5.1 Post operations. After peening, areas of parts shall still be within the dimensional and surface finish requirements. No manufacturing operations, such as straightening, grinding, or etching which relieve stresses developed by peening or which d
49、evelop detrimental residual stresses shall not be permitted after peening. If straightening is required for peened parts, any means other than peen forming shall be prohibited. When peened parts are heated after peening as for baking of paints or protective coating systems, for hydrogen embrittlement relief after electroplating or for other thermal treatments, the temperatures employed shall be limited as follows (
