1、MIL-S-18732D 1 MARCH 1968 SUPERSEDING 16 August 1963 MIJA-18732C MILITARY SPECIFICATION STEEL BARS, WIRE, FORGING. STOCK, FORGINGS, TUBING (431), SPECIAL QUALITY This specification is mandatory for use by all Departme?tts and Agencies of the Department of Defense. 1. SCOPE Fed. Std. No. 183 - Contin
2、uous Iden- tification Mark- 1.1 Scope. This specification presents re- ing of Iron and quirements for a special quality of type 431 Steel Products corrosion-resistant steel. MILITARY 2. APPLICABLE DOCUMENTS MIL-STD-129 - Marking for Ship- ment and Storage 2.1 The following documents, of the issue MI
3、GSTD-163 - Steel Mill Products, in effect on date of invitation for bids or re- Preparation for quest for proposal, form a part of this spe- Shipment and Stor- cification to the extent specified herein: age SPECIFICATIONS MIL-STD-753 - Corrosion - Resistant Steel Parts, Sam- MILITARY pling, Inspecti
4、on MIGH-6875 - Heat Treatment of Steels (Aircraft Practice, Process for) STANDARDS FEDERAL and Testing for Surface Passiva- tion (Copies of specifications, standards, drawings, and publications required by suppliers in connection with specific procurement functions should be obtained from the procur
5、ing activity or as directed by the con- tracting officer.) Fed. Std. No. 48 - Tolerances for Steel and Iron 2.2 Other publications. The following docu- ments form a part of this specification to the Wrought Prod-. extent specified herein. Unless otherwise in- ucts dica.ted, the issue ilr effect on d
6、ate of invita- Fed. Test Method M et al s ; Te st tion for bids-or request for proposal shall Std. NO. 151 - Methods apply. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- flIL-S-LA732D MILS-18732D Society of Automotive Enginee?a, Inc. (Ao-ospace Mu
7、teTial Specificatiolt) AMs2303 - Aircraft Quality Steel Cleanliness (Application for copies of the above publication should be addressed to the Society of Automotive Engineers, Inc, 485 Lexington Ave., New York, N. Y. 10017.) Uniform Classification Committee Uniform Freight CIassification Rules . “a
8、= (Application for copies of the above publication should be addressed to the Uniform Classification Committee, 202 Chicago Union Station, Chicago, Ill. eoeo6.) 3. REQUIREMENTS 3.1 Chemical composition. The chemical composition shall be as specified in table I. TABLE I. Chemical contpostion Check an
9、alysis Element Percent tolernncc (percent) Carbon -0.13-0.17 I 0.01 Manganese -0.30-0.80 i .O3 Silicon -0.20-0.60 .O5 Phosphorous -0.040 (max.) I . ,005 Chromium i 15,50-16.50 i .20 Nickel . -2.00-3.00 .O7 Molybdenum -0.25 (max.) Nitrogen -0.10 (max.) Iron Balance Sulfur i -0,030 (max.) f ,005 Indiv
10、idunl determinations mny vnry nbovo or below the specified mngc to the extent shown in the check nnnlysis column, except that elements in any lient shall not vnty both shove nnd below the specified range. 3.2 Quality, All material supplied under this specification shall be magnetic particle inspecte
11、d in accordance with the require- ments of AMs2303 and shall comply with the frequency and severity limits specified therein. 3.2.1 Micyostwctwe, After heat treat- ment to the HT-125 condition, materials shall not exhibit banding or segregation in excess of the limits of 3,2.1,1 or 3.2.1.2, 2 _ -. 7
12、5 777790b OLL7307 b W respectively. The limits apply to all fields of longitudinal sections of specimens shQwn in figures 1 and 2 and when examined at 260 diameters magnification. 3.2.1.1 Free ferrite. Material shall not contain banded free ferrite in excess of that indicated by figure 3. Blocky fer
13、rite, not banded, shall not exceed 4 percent. Unaccept- able microstructure containing excessive banded free ferrite is shown on figure 4. 3.2.1.2 Retuined austenite. Material shall not contain banded retained austenite in ex- cess of amount shown in figure 6. Figures 6 and 7 represent unacceptable
14、microstruc- tures, Blocky austenite, not banded, is per- mitted. 3.3 Condition (as supplied). The material shall be furnished annealed, or otherwise heat treated to a hardness range of Brinell 229- 302 (excluding forging stock), 3.3.1 Swface condition. 3.3.1.1 Bur und forging stock, round. Sur- face
15、s shall be ground or rough turned. 3.3.1.2 Bur und forging stock, rectangular, Surfaces shall be hot-rolled and free from scale. Slight surface imperfections which are removable within half .the specified tolerances will not be cause for rejection. 3.3.1.3 Tubing. Surface imperfections such as handl
16、ing marks, straightening marks, light mandrel and die or roll marks, shallow pits, and scale pattern will not be cause for rejection, provided the imperfections are removable without reducing the diameter or wall thickness of the tubing below the per- missible tolerance limits. Imperfections shall b
17、e removed by grinding or buffing, except when the imperfections are open so that the root areas are visible to the unaided eye and the surfaces blend smoothly into the normal surfaces of the tubing, 3.3.1.4 Wire. Surfaces shall be cold drawn, ground, polished or pickled. Provided by IHSNot for Resal
18、eNo reproduction or networking permitted without license from IHS-,-,-MIL-S-L8732D 95 9999906 OLL7310 2 3.3.2 Grain size. Grain size shall be No. 3 or finer, as indicated in supplement A, Fed- eral Test Method Standard- No. 151, when tested in the HT-125 condition (excluding reforging stock). 3.4 Re
19、sponse to thermal treatment. When heat treated as specified herein, the materia1 shall develop the properties specified in table II. h 3.4.1 HT-ZOO condition. HT-200 is i achieved by (1) quenching in oil at 52“ +6“ C (125“ +loo F) from 1,020“ +14“ C (1,875“ 225“ F) ; (2) cooling to room tem- peratur
20、e in water; (3) soaking at -73“ MILS-18732D (4) tempering at 288“ t14“ C (550“ 225“ F) for 2 hours; and (5) retempering at 288“ “14“ C (550“ +25“ F) for 2 hours. 3.4.2 HT-125 condition,. HT-125 is achieved by quenching in vigorously agitated oil (Houghton #2 or oil of equivalent H value) at 52“ +6“
21、C (125“ “10“ F) from 1,024“ +8“ C (1,875“ t15“ F), cooling to room temperature in water, tempering at 635“ entire lot shall be rejected. (d) Quantity contained, feet or pounds b Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL“18732D (as defined i
22、n the contractors order for each size and shape). (e) Name of contractor (and name of manufacturer, if not the same). (f) Contract or order No. 6. NOTES 6.1 Intended use. The steel covered by this specification is intended for use in the manu- facture of highly stressed structural parts exposed to c
23、orrosive environments and op- erating temperatures to 500“ F for materials heat treated to the HT-200 condition. The material is useful for one component of threaded stainless steel fasteners because of a tendency to resist seizure when in contact with othr types of corrosion resisting steel. 6 I Pr
24、ovided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MILS-18732D FIGURE 1. Desired microstructure (loo./; Martensite) FIGURE 2. Acceptable microstructure containing small amount of banded free ferrite 7 Provided by IHSNot for ResaleNo reproduction or networ
25、king permitted without license from IHS-,-,-MIL-S-18732D e FIGURE 3. Acceptable microstructure containing maximum amount of banded free ferrite permitted in any field e FIGURE 4, UnacceptabIe microstructure containing excessive banded free ferrite - “ -c 8 Provided by IHSNot for ResaleNo reproductio
26、n or networking permitted without license from IHS-,-,-MILS-18732D FIGURE 6. Acceptable microstructure containing maximum amount of banded retained austenite permitted in any field of examination - Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MILr
27、S-18732D PIGUHE O. Unacceptable microstructure containing excessive banded retained austenite 10 FIGURE 7, Unacceptable microstructure containing excessive banded retained austenite Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-S-18732D ROUNDS
28、H 2/3 Wal I Th1 ckness RECTANGLES - Surf ace be Exemi to ned 11 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-S-18732D 6.2 Precaution, 6,2.1 Heut t?*eattn.ent. This material is not recommended for use after heat treatment to a strength level ot
29、her than as specified in table II because of the possibility of develop- ing low impact strength and unsatisfactory corrosion resistance, 6.3 The surfaces of parts manufactured from this type of steel will be passive when tested in accordance with MIL-STD-763, Custodians: Ar m y-M It Navy-AS Air For
30、ce-11 6.4 Ordering data. Procurement docu- menta should specify : (a) Title, number, and date of this specification. (see 3.3). desired. (b) Quantity, thickness, size or shape (c) Level of packaging and packing 6.5 Cold heading wire is not covered by this specification and should be purchased to 1 ASTM A493. Reviewer activities: Army-MX, MU, WE & U.-& GOVERNMENT PRINTING OFFICE: I968-30l.O73-(Zl40) , Preparing activity : Navy-AS Project No. 9510-0093 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
