1、MIL-S- 9 8 OB 1 July 1965 Superseding 15January1952 MIL-S-98 OA MILITARY SPECIFICATION STEEL, CHROMIM ALLOY, BARS (FOR TORPEDO GYROSCOPE BEARINGS) This specification has been approved by the Department of Defense and is mandatory for use by the Departments of the Army, the Navy, and the Air Force. 1
2、. SCOPE 1.1 Scope - This specification covers spheroidized chromium alloy steel bars of special metallurgical quality in sizes 1 inch and under in diameter, for use in torpedo gyroscope bearings requiring a finish of minimum surface rough- ness. 1.2 Classification - Chromium alloy steel bars shall b
3、e of the following classes, as specified (see 6.1): Class I - Hot Rolled. Class II - Ground. 2. APPLICABLE DOCUMENTS 2.1 The following documents of the issue in effect on date of invitation for bids or request for proposal, form a part of the specification to the extent specified herein. SPECIFICATI
4、ONS Federal QQ- T-5 7 O . Tool Steel, Alloy FSC 9510 -* Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-S-SOB 95 SS9SSOb Ol11i11120 4 MIL-S-98OB STANDARDS Federal FED-STD-48 Fed Test Method Std. No. 151 FED-STD-183 Military MIL-STD-163 Tolerances
5、 for Iron and Steel Wrought Products Metals, Test Methods Continuous Identification Marking of Iron and Steel Products Steel Mill Products, Preparation for Shipment and Storage (Copies of specifications, standards, and drawings required by contractors in connection with specific procurement function
6、s should be obtained from the procuring agency or as directed by the contracting officer.) 2.2 Other publications - The following publication, unless otherwise stated, forms a part of this specification: AMERICAN SOCIETY FOR TESTING AND MATERIALS PUBLICATION ASTM Standard E45 of Steel Determining th
7、e Inclusion Content (Information as to the availability of this standard may be obtained from the American Society for Testing and Materials, 1916 Race Street, Philadelphia, Pa. 19103.) 3. REQUIREMENTS 3.1 Process - The bars shall be rolled or drawn from vacuum melted steel. 34 2 Chemical compositio
8、n - The chemical composition shall conform to Table I. The contractor shall furnish a report of the ladle analysis of each heat. 3.3 Hardness (as received) - The Rockwell hardness of the bars as received shail be not more than 95 on the B scale when tested in compliance with 4.4.3, 2 Provided by IHS
9、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-S-SBOB 75 9999906 OLL412L b W Element Carbon Manganes e Silicon Chromium Nickel Molybdenum Sulphur Phosphorus Copper 3.4 - MIL-S -9 8 OB TABLE I. Chemical Composition -=-.- Ladle analysis Minimum Percent -A - Maxi
10、mum Percent 1.10 0.45 0.35 1.60 0.35 0.08 0.025 0.025 0.25 Permissible variations for check analyses, over the maximum limit or under the minimum limit. Percent O. 03 O. 03 0.02 O. 05 O. 03 o. o1 0.005 0.005 -_ Macrostructure - The bars shall show no pipe, porosity, abnormal segregation, or abnormal
11、 change in structure from surface to center when tested in compliance with 4.4.4. The etched sections shall be superior to the macrostructures shown for 1 Diameter on Plate No. I of QQ-T-570, 3.5 Microstructure - 3.5.1 Carbide form - The carbides shall be spheroidized and of the size and form illust
12、rated on the acceptable.photograph of figure 1, when bars are tested in compliance with 4.4.7. 3.5.2 Carbide distribution - The carbide distribution shall be as illustrated on the acceptable photograph of figure 2, when the bars are tested in compliance with 4.4.8. 3.5.3 Inclusions - The inclusion r
13、ating of bars tested in compliance with 4.4.6 shall be in conformance with Table II. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-S-98OB TABLE II, Inclusion content rating (see 4.&6) INCLUSION DIMENSIONAL LIMITATION WORST TYPE THICKNESS OR DIA
14、METER, MCH FIELD A - Thin 0.00016 max 200 A - Heavy 0.00040 rnax 1.0 B - Thin 0.0003 to 0.0005, excl 1.5 B - Heavy 0.0005 to 0.0010, incl 1.0 C - Thin 0.00020 rnax 1.5 C - Heavy 0.00035 max 1.0 D - Thin 0,0002 to 0.0004, excl 1.5 D - Heavy 0,0004 to 0.0010, incl 1. o r 9.7 8.8 Grain size of the hard
15、ened fracture - The grain of specimens tested in compliance with 4.4.9 shall be fine and uniform. Decarburization - When tested in compliance with 4.4.2, ground bars shall show no decarburization (partial plus total). Decarburization partial plus total) of hot rolled bars 1 inch and under in diamete
16、r shall not exceed 0.012 inch in depth, Permissible variation in diameter - The maximum permissible variation from specified diameter for ground bars shall be plus or minus 0.001 inch. The maximum permissible variation from specified diameter for hot rolled bars shall be as shown in paragraph la1 of
17、 Federal Standard No. 48. Length - Unless otherwise specified by the procuring activity, bars shall be furnished in mill lengths of 6 to 16 feet except that weight of bars shorter than 10 feet shall not exceed 10 percent of the total weight. with Federal Standard No. 183. free from injurious defects
18、 such as heavy scale, deep pits, pipe, laps, cracks, and seams. The bars shall be commercially straight and free from damaged ends. 3.9 3.10 3.11 Identification of product - Bars shall be marked in accordance Workmanship - The bars shall be of uniform quality, smooth, 3.12 3.5.3.1 For Types A, B, an
19、d C thin combined, there shall be not more than three fields of No. 2.0 A Type or No, 1.5 B and C Types and not more than five other lower rateable A, B, and C Type thin fields per specimen. For Type D thin, there shall be not more than three No. 1.5 fields and no more than five other lower rateable
20、 D Type thin fields per specimen. There shall be not more than one field each of No. 1,O A, B, C, or D Type heavy per specimen. Hardness (heat treated1 - The Rockwell hardness from the center to the edge of specimens tested in compliance with 4.4.10 shall be not less than 63 on the C scale. 3.6 Prov
21、ided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4. QUALITY ASSURANCE PROVISIONS MIL-S-908 B 4.1 Responsibility for inspection - Unless otherwise specified in the contract or purchase order, the supplier is responsible for the performance of all inspectio
22、n requirements as specified herein. Except as otherwise specified, the supplier may utilize his own facilities or any commercial laboratory acceptable to- the Government. The Government reserves the right to perform any of the inspections set forth in the specification where such inspections are dee
23、med necessary to assure supplies and services conform to prescribed requirements. 4.2 Sampling - 4.2.1 Lot - For the purpose of sampling and inspection, a lot shall consist of all the bars submitted for inspection at the same time of the same melting furnace heat and of the same annealing furnace. 4
24、.2.2 Sampling for chemical analysis - One sample for chemical analysis .shail be selected from each lot. 4.2.3 Sampling for hardness (as received), macrostructure, micro- structure, decarburization - One full cross-sectional slice, 1/2 & 1/32 inch long, shall be taken from one end of each bar of the
25、 lot. 4.2.4 Sampling for hardness (heat treated), grain size - One full cross- sectional slice, 2 inches long, shall be taken from each of five bars of the lot, 4.3 Examination - Five bars from each lot shall be examined to establish compliance with identification, dimensional and workmanship requir
26、ements. 4.4 Tests - 4.4.1 Chemical analysis - The sample taken as specified in 4.2.2 shall be subjected to chemical analysis in accordance with Method 111 or 112 of Federal Test Method Standard No. 151. In case of dispute, the analysis of Method 111 shall be the basis for acceptance or rejection. 4.
27、4.2 Decarburization - Both faces of no fewer than five of the speci- mens taken as specified in 4.2.3 shall be finished flat and smootho One face of each specimen shall be polished and etched with a 5 percent nital solution (5 percent nitric acid, 1.43 sp. gr., plus 95 percent ethyl alcohol). The sp
28、ecimen shall be rinsed in ethyl alcohol, blown dry, and examined for decarburization, at a magnification of 100 diameters. 4.4.3 Hardness (as received) - Rockwell B hardness determinations shall be made on the unetched face of the five specimens employed for the tests of 4.4.2. Provided by IHSNot fo
29、r ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-S-9808 95 W 9999906 OLL412Li L r MIL-S-980B 4.4.4 taken as specified in 4.2.3 shall be made flat and smooth by a fine machine cut or by grinding, The smooth face of these specimens and the unetched face of the speci- me
30、ns employed for the tests of 4.4.2 shall be etched for 35 minutes at 160 to 175“ F in dilute hydrochloric acid (50 percent hydrochloric acid, 1.19 sp. gr., plus 50 per- cent water). The specimens shall be scrubbed with a brush under running hot water, rinsed, and dried by an air blast. The specimens
31、 shail be examined by the unaided eye for compliance with 3.4. Macrostructure - One face of each of the remaining specimens 4.4,5 Microstructure - Ten of the specimens employed for the tests of 4.4.4 shall be cut in the longitudinal direction, midway between the center and the surface of the specime
32、n. The longitudinal surface of one part of each specimen shall be polished. 4.4.6 Inclusions - The inclusion content shall be determined on the polished longitudinal face of each of the ten specimens taken as specified in 4.4.5. The area to be rated shall be approximately 1/2 by 1/2 inch. When test
33、specimens taken in conformance with 4.2.3 and 4.4.5 are smaller than 1/2 by 1/2 inch, the area to be rated shall be the entire area of the specimen. A rateable field is defined as one which, has a Type A, B, C, or D inclusion rating of at least No. 1.0 thin or heavy in accordance with the dimensiona
34、l limitations of 3.5.3 and the Jernkontoret chart, Plate El, ASTM E45. 4.4.7 Carbide form - The 10 specimens employed for the tests of 4.4.6 shal be etched in a 5 percent nital solution, rinsed in ethyl alcohol and dried by an air blast. The specimen shall be examined at a magnification of 1,000 dia
35、meters for compliance with 3.5.1. 4.4.8 Carbide distribution - The etched specimen employed for the tests specified in 4.4.7 shall be examined at a magnification of 100 diameters for compliance with 3.5.2. 4.4.9 Grain size - The specimens taken as specified in 4.2.4 shall be hardened by heating at 1
36、,500 to 1,600 F for 40 minutes &d quenching in oil maintained at 100 to 120F. The specimens shall be broken transversely at a section midway between the ends and examined at the fracture for compliance with 3.7. 4.4.10 Hardness (heat treated) - The fractured face of one part of the specimen employed
37、 for the tests of 4.4.9 shall be prepared for hardness test by carekl grinding, using a coolant. The Rockwell C hardness of the ground face shll be determined from the center to the edge. Hardness tests shall not be made on any decarburized zones near the edge. 6 Provided by IHSNot for ResaleNo repr
38、oduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-S-9OB 75 777770b OLLY12 9 -. MIL-S-980B -e I eu Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
