MIL-S-6758B-1998

AMSC N/A FSC 9510 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. MIL-S-6758B NOTICE 1 5 October 1998 MILITARY SPECIFICATION STEEL, CHROME-MOLYBDENUM (4130) BARS AND REFORGING STOCK (AIRCRAFT QUALITY) MIL-S-6758B, dated 18 May 1993, is hereby cancelled. Future acquisition of this item should refer to SAE-AMS-S-6758, "Steel, Chrome-Molybdenum (4130) Bars and Reforging Stock (Aircraft Quality)." (Application for copies of SAE publications should be addressed to the Society of Automotive Engineers, 400 Commonwealth Drive, Warrendale, PA 15096-0001.) Custodians: Preparing Activity: Army - MR Navy - AS Navy - AS Air Force - 11 (Project 9510-1026) Review Activities: Army - AT, CR4, EA, MI Navy - OS DLA - IS NOTICE OF CANCELLATION INCH-POUND Y flIL-S-b758B 99999Ob 1855433 82b I INCH-POUND I MIL-S-67586 18 MAY 1993 SUPERSEDING MIL-S-6758A 23 MAY 1961 MILITARY SPECIFICATION STEEL, CHROME-MOLYBDENUM (4130) BARS AND REFORGING STOCK (AIRCRAFT QUALITY) T h i s s p e c i f i c a t i o n i s approved fo r use by a l l Departments and Agencies o f the Depar tment o f Defense. l. SCOPE 1 .1 Scope . Th i s spec i f i ca t i on cove rs chrome-molybdenum (4130) steel bars and f o r g i n g s t o c k o f a i r c r a f t q u a l i t y . 1 . 2 C l a s s i f i c a t i o n . The s t e e l b a r s and r e f o r g i n g stock sha l l be as fol lows: 1 . 2 . 1 P h y s i c a l c o n d i t i o n . M a t e r i a l s s h a l l b e f u r n i s h e d i n o n e o f t h e f o l l o w i n g p h y s i c a l c o n d i t i o n s , a s s p e c i f i e d ( s e e 6 . 2 ~ ) : A . A s f o r g e d B. A s r o l l e d C. Annealed D. Normal i zed E . Normal i zed and tempered F . Hardened and tempered 1 . 2 . 2 S u r f a c e c o n d i t i o n s . M a t e r i a l s s h a l l be f u r n i s h e d i n one o f t h e f o l l o w i n g s u r f a c e c o n d i t i o n s , as s p e c i f i e d ( s e e 6 . 2 ~ ) : 1 . Black , as f o rged or r o l l e d 2 . P i c k l e d or b l a s t c l e a n e d 3. Rough t u r n e d 4 . C o l d f i n i s h e d ( d r a w n ) 5 . Turned, ground and pol ished B e n e f i c i a l comments ( recommendat ions , add i t ions , de le t ions) and any per t inent da ta wh ich may be o f use i n i m p r o v i n g t h i s document should be addressed to : Commanding O f f i c e r , N a v a l Air W a r f a r e C e n t e r A i r c r a f t D i v i s i o n L a k e h u r s t , Systems Requirements Department (Code SR3>, Lakehurs t , NJ 08733-5100, by using t h e s e l f - a d d r e s s e d S t a n d a r d i z a t i o n Document Improvement Proposal (DD Form 1426) a p p e a r i n g a t t h e e n d o f t h i s document or b y l e t t e r . AMSC N I A FSC 9510 D I S T R I B U T I O N STATEMENT A. Approved f o r p u b l i c r e l e a s e ; d i s t r i b u t i o n i s u n l i m i t e d . c NIL-S-b75BB m 9999906 1855434 7b2 m MIL-S-6758B 2. APPLICABLE DOCUMENTS 2.1 Government documents. 2 .1 .1 Spec i f i ca t i ons , s tandards , and handbooks. The f o l l o w i n g spec i f i ca t i ons , s tandards , and handbooks form a p a r t of t h i s document to t h e e x t e n t s p e c i f i e d h e r e i n . U n l e s s o t h e r w i s e s p e c i f i e d , t h e i s s u e s o f these d o c u m e n t s a r e t h o s e l i s t e d i n t h e i s s u e of the Depar tment o f Defense Index o f S p e c i f i c a t i o n s a n d S t a n d a r d s (DODISS) a n d s u p p l e m e n t t h e r e t o , c i t e d i n t h e s o l i c i t a t i o n ( s e e 6 . 2 e ) . STANDARDS FEDERAL FED-STD-183 - C o n t i n u o u s I d e n t i f i c a t i o n M a r k i n g o f I r o n and Steel Products MILITARY MIL-STD-129 - Mark ing for Shipment and Storage MIL-STD-163 - S t e e l Mill Produc ts P repara t i on f o r Shipment and Storage ( U n l e s s o t h e r w i s e i n d i c a t e d , c o p i e s o f f e d e r a l a n d m i l i t a r y s p e c i f i c a t i o n s , s tandards , and handbooks a re ava i lab le from DODSSP, S u b s c r i p t i o n S e r v i c e s Desk, 700 Robbins Avenue, Bldg. 4D, P h i l a d e l p h i a , PA 19111-5094.) 2 .2 Non-Government publ icat ions. The f o l l o w i n g documents form a p a r t o f t h i s document t o t h e e x t e n t s p e c i f i e d h e r e i n . U n l e s s o t h e r w i s e s p e c i f i e d , t h e i ssues of the documents which are DOD a d o p t e d a r e t h o s e l i s t e d i n t h e i s s u e o f t h e DODISS c i t e d i n t h e s o l i c i t a t i o n . U n l e s s o t h e r w i s e s p e c i f i e d , t h e i s s u e s o f documents n o t l i s t e d i n t h e DODISS a re t he i ssues of t h e d o c u m e n t s c i t e d i n t h e s o l i c i t a t i o n ( s e e 6 . 2 e ) . AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM) ASTM A255 - End-Quench T e s t for H a r d e n a b i l i t y o f S tee l ASTM A700 - Packaging, Marking, and Loading Methods for Stee l Produc ts for Domestic Shipment ASTM E8 - Test Methods o f Tens ion Tes t i ng o f M e t a l l i c M a t e r i a l S ASTM E10 - Test Method for B r i n e 1 1 Hardness o f M e t a l l i c M a t e r i a l S ASTM E18 - Test Methods for Rockwell Hardness and Rockwell Super f i c ia l Hardness o f M e t a l l i c M a t e r i a l s 2 --``,`,,``,,````,,,,`,,`,````,`-`-`,,`,,`,`,,`--- MIL-S-6758B m 999990b L855435 bT9 m M I L-S-6758B ASTM E112 - Determin ing Average Gra in S ize ASTM E350 - Chemical Analysis of Carbon Steel , Low-Al loy, S t e e l , S i l i c o n E l e c t r i c a l S t e e l , I n g o t I r o n ASTM E381 - Macro tech Tes t ing , Inspec t ion , and Rat ing S tee l P roduc ts Compr i s ing Ba rs , B i l l e t s , B1 ooms , and Forgi ngs ASTM E l 077 - Es t ima t ing t he Dep th of D e c a r b u r i z a t i o n of S tee l Specimens ( A p p l i c a t i o n for cop ies shou ld be addressed t o the Amer ican Soc ie ty for T e s t i n g a n d M a t e r i a l s (ASTM), 1916 Race S t r e e t , P h i l a d e l p h i a , PA 19103-1187.) SOCIETY OF AUTOMOTIVE ENGINEERS (SAE) AMS 2251 - Tolerances, Low-Al loy Steel Bars AMS 2301 - A i r c r a f t Q u a l i t y S t e e l C l e a n l i n e s s , M a g n e t i c P a r t i c l e I n s p e c t i o n P r o c e d u r e . AMS 2370 - Qual i t y Assurance Sampl ing and T e s t i n g Carbon and Low-Alloy Steel Wrought Products and Forg ing S tock . ( A p p l i c a t i o n for cop ies shou ld be addressed t o t h e S o c i e t y o f Automot ive Eng ineers , I nc . 400 Commonweal t h D r i v e , W a r r e n d a l e , PA 15096. ) (Non-Government s t a n d a r d s a n d o t h e r p u b l i c a t i o n s a r e n o r m a l l y a v a i l a b l e from t h e o r g a n i z a t i o n s t h a t p r e p a r e or d i s t r i b u t e t h e d o c u m e n t s . These documents a l s o may be a v a i l a b l e i n or t h r o u g h l i b r a r i e s or o t h e r i n f o r m a t i o n a l s e r v i c e s . ) 2.3 Order of precedence. I n t h e e v e n t o f a c o n f l i c t between the t e x t o f t h i s documen t and t he re fe rences c i t ed he re in , t he t ex t o f t h i s document takes precedence. Noth ing i n t h i s document, however, supersedes appl icable laws and r e g u l a t i o n s u n l e s s a s p e c i f i c e x e m p t i o n has been obtained. 3. REQUIREMENTS 3.1 M a t e r i a l . 3 . 1 . 1 Q u a l i t y . The s t e e l s h a l l be o f a i r c r a f t q u a l i t y . 3 .1 .1 .1 C lean l i ness . When i n s p e c t e d m a g n e t i c a l l y i n a c c o r d a n c e w i t h t h e procedures o f AMS 2 3 0 1 , m a t e r i a l s h a l l n o t e x c e e d t h e s i z e a n d f r e q u e n c y r a t i n g limits s p e c i f i e d i n AMS 2301 (see 4.5). 3.1 .2 Manufac tur ing p rocess . The s t e e l may be mel ted by one o f t h e commerc ia l l y accep tab le t ypes o f me l t i ng i nc lud ing open hea r th , bas i c oxygen or e l e c t r i c a r c f u r n a c e . The s t e e l may be i n g o t c a s t or c o n t i n u o u s c a s t i n t o from p i p i n g and undue segregation. b i 1 l e t s . When i n g o t c a s t i n g , s u f f i c i e n t d i s c a r d s h a l l be made t o secure freedom 3 MIL-S-6758B 9999706 1855436 535 D MIL-S-6758B 3 . 1 . 3 P h y s i c a l / s u r f a c e c o n d i t i o n . U n l e s s o t h e r w i s e s p e c i f i e d i n t h e a c q u i s i t i o n d o c u m e n t s , ( s e e 6 . 2 ~ 1 , b a r s 1.500 inches or l e s s i n d i a m e t e r or t h i c k n e s s s h a l l be f u r n i s h e d i n c o n d i t i o n s (C> (41, and bars over 1 .500 inches i n O d iamete r or t h i c k n e s s s h a l l be f u r n i s h e d i n c o n d i t i o n s ( C ) ( 2 ) . 3 .2 Chemical composi t ion. The chemica l compos i t i on sha l l be w i th in t he limits s p e c i f i e d i n t a b l e I when t e s t e d i n a c c o r d a n c e w i t h 4 . 6 . The hea t a n a l y s i s s h a l l c o n f o r m t o t h e c o l u m n e n t i t l e d " A n a l y s i s " , and the semi - f i n i shed or f i n i s h e d p r o d u c t s h a l l c o n f o r m to t h e c o l u m n e n t i t l e d "Check a n a l y s i s to1 erance" . 3 . 3 H a r d e n a b i l i t y . The h a r d e n a b i l i t y f o r a l l s p e c i f i e d p h y s i c a l c o n d i t i o n s s h a l l be J5 = 34 HRC min, and J8 = 27 HRC min when t e s t e d i n a c c o r d a n c e w i t h 4 . 7 . 3 . 4 G r a i n s i z e . The a u s t e n i t i c g r a i n s i z e s h a l l be p redominan t l y No. 5 or f i n e r , w i t h g r a i n s as l a r g e as No. 3 p e r m i s s i b l e when t e s t e d i n a c c o r d a n c e w i t h 4.8. 3 .5 Mac ros t ruc tu re . V i sua l examina t ion of t r a n s v e r s e s e c t i o n s o f stock i n s i z e s up t o and i n c l u d i n g 36 square inches shal l be equal to or b e t t e r t h a n S-2, R - 1 , and C-2 o f ASTM E381; s i z e s o v e r 36 square inches, up t o a n d i n c l u d i n g 100 square i nches , sha l l be equal t o or b e t t e r t h a n S-2, R-2, and C-3 o f ASTM E381. I n a d d i t i o n , t h e t r a n s v e r s e s e c t i o n s s h a l l show n o p i p e or c racks , and any p o r o s i t y , s e g r e g a t i o n s , i n c l u s i o n s , and o t h e r i m p e r f e c t i o n s s h a l l be no worse than the preceeding macrographs o f ASTM E 381. Macroscopic examinat ion o f f i n i s h e d b a r s i s r e q u i r e d o n l y i f m a n u f a c t u r e r s i n s p e c t i o n o f t h e m a c r o s t r u c t u r e a t an e a r l i e r s t a g e of processing such as forged bars, b looms or b i l l e t s has n o t been accompl ished (see 4.9). 3 . 6 D e c a r b u r i z a t i o n . U n l e s s o t h e r w i s e s p e c i f i e d ( s e e accordance w i th 4 .10 , the depth of a n y d e c a r b u r i z a t i o n s h a l 6.2f1, when t e s t e d i n 1 be as f o l lows: a . M a t e r i a l s f u r n i s h e d i n s u r f a c e c o n d i t i o n s ( 2 ) and ( 4 ) s h a l l n o t h a v e d e c a r b u r i z a t i o n g r e a t e r t h a n t h e limits i n t a b l e II. b . B a r s f u r n i s h e d i n s u r f a c e c o n d i t i o n s ( 3 ) a n d ( 5 ) s h a l l be f r e e from d e c a r b u r i z a t i o n . c . When b a r s a r e o r d e r e d fo r r e f o r g i n g p u r p o s e s , or s u r f a c e c o n d i t i o n (11, a n y d e c a r b u r i z a t i o n l i m i t s a r e w a i v e d . d. When d e t e r m i n i n g t h e d e p t h o f d e c a r b u r i z a t i o n , i t i s p e r m i s s i b l e t o d i s r e g a r d l o c a l a r e a s , p r o v i d e d t h e d e c a r b u r i z a t i o n of such areas does n o t e x c e e d t h e l i m i t s o f t a b l e II by more than 0.005 inch and t he w i d t h i s 0 .065 inch or l e s s . 3.7 Hardness limits for c o n d i t i o n s (C) and ( E ) . a . The hardness f o r ma g r e a t e r t h a n B r i n e 1 c o n d i t i o n s ( l ) , (2) t e r i a 1 i n p h y s i c a l c o n d i t i o n s (C) and ( E ) s h a l l be no 1 229 (or e q u i v a l e n t ) when fu rn i shed i n s u r f a c e , ( 3 1 , and (51 , (see 4 . 1 1 ) . 4 - - ` ` , ` , , ` ` , , ` ` ` ` , , , , ` , , ` , ` ` ` ` , ` - ` - ` , , ` , , ` , ` , , ` - - - MIL-S-b758B m 99999Ob L855437 471 m MI L-S-67588 b. The hardness for m a t e r i a l i n p h y s i c a l c o n d i t i o n s (C) ( E ) s h a l l be no g r e a t e r t h a n B r i n e l l 241 (or e q u i v a l e n t ) when f u r n i s h e d i n s u r f a c e cond i t i on (4 ) ( see 4 .11 ) . 3 . 8 T e n s i l e p r o p e r t i e s o f c o n d i t i o n ( F ) s t e e l . U n l e s s o t h e r w i s e s p e c i f i e d ( see 6 .2 .g ) , t he mechan ica l p roper t i es of b a r s u p p l i e d i n c o n d i t i o n ( F ) i n s i z e s up to a n d - i n c l u d i n g 1 . 5 0 0 i n c h e s i n d i a m e t e r , o r ' d i s t a n c e b e t w e e n p a r a l l e l s i d e s , s h a l l be as s p e c i f i e d i n t a b l e III when t e s t e d i n a c c o r d a n c e w i t h 4 . 1 2 . . . 3 . 9 I d e n t i f i c a t i o n o f p r o d u c t . I t e m s s h a l l be i n d i v i d u a l l y marked for i d e n t i f i c a t i o n i n a c c o r d a n c e w i t h FED-STD-183, e x c e p t t h a t b a r s i z e s l e s s t h a n 0 . 5 0 i n c h i n d i a m e t e r , or d i s t a n c e b e t w e e n p a r a l l e l s i d e s , s h a l l b e m a r k e d i n l i k e manner or b u n d l e d a n d i d e n t i f i e d b y t a g s m a r k e d w i t h t h e same i d e n t i f i c a t i code, the tags t o be a t tached t o each end o f each bund le w i th an ex t ra t ag i n c l u d e d i n t h e b u n d l e . The m a r k i n g i t e m s s h a l l i n c l u d e t h i s s p e c i f i c a t i o n number and the phys i ca l cond i t i on des igna to r ( see 1 .2 .1 and 4 .4 ) . on 3.10 Tolerances. The p e r m i s s i b l e v a r i a t i o n i n d i m e n s i o n o f bars, produced i n c o n f o r m a n c e w i t h t h i s s p e c i f i c a t i o n , s h a l l be as s p e c i f i e d i n AMS 2251 (see 4.4) . 3.10.1 Mill l e n g t h s . When e x a c t or m u l t i p l e l e n g t h s a r e n o t o r d e r e d ( s e e 6 .2 .h>, bars will b e a c c e p t a b l e i n mill l e n g t h s o f 6 to 2 0 f e e t , b u t n o t more than 10 p e r c e n t o f a n y o r d e r s h a l l be f u r n i s h e d i n l e n g t h s s h o r t e r t h a n 1 0 f e e t . 3 .11 Workmanship. Mater ia l shal l be sound, o f u n i f o r m q u a l i t y and c o n d i t i o n , f r e e from p i p e s , a n d s h a l l n o t c o n t a i n l a p s , c r a c k s , t w i s t s , seams, or o t h e r d e f e c t s d e t r i m e n t a l to t h e f a b r i c a t i o n or per formance o f p a r t s ( s e e 4 . 4 ) . 4. QUALITY ASSURANCE PROVISIONS 4 . 1 R e s p o n s i b i l i t y for i n s p e c t i o n . U n l e s s o t h e r w i s e s p e c i f i e d i n t h e c o n t r a c t or p u r c h a s e o r d e r , t h e c o n t r a c t o r i s r e s p o n s i b l e for the per fo rmance of a l l i n s p e c t i o n r e q u i r e m e n t s ( e x a m i n a t i o n s and t e s t s ) as s p e c i f i e d h e r e i n . E x c e p t a s o t h e r w i s e s p e c i f i e d i n t h e c o n t r a c t or p u r c h a s e o r d e r , t h e c o n t r a c t o r may use h i s own or a n y o t h e r f a c i l i t i e s s u i t a b l e fo r the per fo rmance o f t h e i n s p e c t i o n requ i remen ts spec i f i ed he re in , un less d i sapproved by t he Governmen t . The Governmen t rese rves t he r i gh t t o p e r f o r m a n y o f t h e i n s p e c t i o n s s e t f o r t h i n t h i s s p e c i f i c a t i o n where such i n s p e c t i o n s a r e deemed necessary t o ensure supp l ies and se rv i ces con fo rm t o p r e s c r i b e d r e q u i r e m e n t s . 4 . 1 . 1 R e s p o n s i b i l i t y f o r compl iance. All i t e m s s h a l l meet a l l r e q u i r e m e n t s o f s e c t i o n s 3 and 5. The i n s p e c t i o n s e t f o r t h i n t h i s s p e c i f i c a t i o n s h a l l become a p a r t of t h e c o n t r a c t o r ' s o v e r a l l i n s p e c t i o n s y s t e m or q u a l i t y p r o g r a m . The absence o f a n y i n s p e c t i o n r e q u i r e m e n t s i n t h e s p e c i f i c a t i o n s h a l l n o t r e l i e v e t h e c o n t r a c t o r o f t h e r e s p o n s i b i l i t y o f e n s u r i n g t h a t a l l p r o d u c t s or s u p p l i e s submi t ted t o the Government for accep tance comp ly w i th a l l r equ i remen ts o f t h e c o n t r a c t . S a m p l i n g i n s p e c t i o n , a s p a r t o f manu fac tu r ing ope ra t i ons , i s an a c c e p t a b l e p r a c t i c e t o ascer ta in con formance t o requ i rements , however , th is does n o t a u t h o r i z e s u b m i s s i o n o f known d e f e c t i v e m a t e r i a l , e i t h e r i n d i c a t e d or a c t u a l , n o r does i t commit the Government t o a c c e p t d e f e c t i v e m a t e r i a l . 5 --``,`,,``,,````,,,,`,,`,````,`-`-`,,`,,`,`,,`--- MIL-S-b758B m 99999Ob 1855438 308 m MIL-S-6758B 4.2 C l a s s i f i c a t i o n o f i n s p e c t i o n . The i n s p e c t i o n r e q u i r e m e n t s s p e c i f i e d h e r e i n a r e c l a s s i f i e d as follows: O a . Q u a l i t y c o n f o r m a n c e i n s p e c t i o n ( s e e 4 . 3 ) . 4.3 Qua l i t y con fo rmance i nspec t i on . Qua l i t y con fo rmance i nspec t i ons sha l l c o n s i s t o f t h e e x a m i n a t i o n s a n d t e s t s s p e c i f i e d i n t h i s s p e c i f i c a t i o n . For each r e q u i r e m e n t s p e c i f i e d i n s e c t i o n 3 , t h e c o r r e s p o n d i n g t e s t m e t h o d o f s e c t i o n 4 i s shown i n t a b l e IV. 4.3.1 x. The l o t s h a l l c o n s i s t o f a l l b a r s o f t h e same s i z e and c o n f i g u r a t i o n , p h y s i c a l c o n d i t i o n , from the same heat , produced under the same p r o c e s