1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2014 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AS7251CAEROSPACESTANDARDAS7251 REV. C Issued 1991-10 Reaffirmed 2006-10 Revised 2
5、014-08 Superseding AS7251BNuts, Self-Locking, Steel, Corrosion and Heat Resistant High Strength, All Metal 1200 F Use, UNJ Thread Form FSC 5310 RATIONALE Introduction of sampling data including the updating of 4.2 and 4.3 and the addition of Tables 8 to 12, addition of new 3.2 headed design, additio
6、n of new 3.6 for NDT requirement, paragraphs renumbered and general updating. 1. SCOPE 1.1 Type This document covers all metal, self-locking wrenching nuts, plate nuts, shank nuts, and gang channel nuts made from a corrosion and heat resistant steel of the type identified under the Unified Numbering
7、 System as UNS S66286 and of 160 ksi tensile strength at room temperature, with maximum test temperature of parts at 1200 F. 1.2 Application For use up to approximately 1200 F where high strength nuts with UNJ thread form are required for use with standard AS8879 external threads. 2. REFERENCES 2.1
8、Applicable Documents The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between t
9、he text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. SAE INTERNATIONAL AS7251C Page 2 of 24 2.1.1 SAE Publications Available from
10、SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.AMS2410 Plating, Silver, Nickel Strike, High Bake AMS2411 Plating, Silver for High Temperature Applications AMS5731 Steel, Corrosion and Heat-Res
11、istant, Bars, Wire, Forgings, Tubing, and Rings, 15Cr - 25.5Ni - 1.2Mo - 2.1Ti - 0.006B - 0.30V, Consumable Electrode Melted, 1800 F (982 C) Solution Heat Treated AMS5732 Steel, Corrosion and Heat-Resistant, Bars, Wire, Forgings, Tubing, and Rings, 15Cr - 25.5Ni - 1.2Mo - 2.1Ti - 0.006B - 0.30V, Con
12、sumable Electrode Melted, 1800 F (982 C) Solution and Precipitation Heat Treated AMS5734 Steel, Corrosion and Heat-Resistant, Bars, Wire, Forgings, and Tubing, 15Cr - 25.5Ni - 1.2Mo - 2.1Ti - 0.006B - 0.30V, Consumable Electrode Melted, 1650 F (899 C) Solution Heat Treated AMS5737 Steel, Corrosion a
13、nd Heat-Resistant, Bars, Wire, Forgings, and Tubing, 15Cr - 25.5Ni - 1.2Mo - 2.1Ti - 0.006B - 0.30V, Consumable Electrode Melted, 1650 F (899 C) Solution and Precipitation Heat Treated AMS5853 Steel, Corrosion and Heat-Resistant, Bars and Wire, 15Cr - 25.5Ni - 1.2Mo - 2.1Ti - 0.006B - 0.30V, Consuma
14、ble Electrode Melted, 1800 F (982 C) Solution Treated and Work Strengthened, 160 ksi (1103 MPa) Tensile Strength AS954 Wrenches, Hand, Twelve Point, High Strength, Thin Wall AS1310 Fastener Torque for Threaded Applications, Definitions of AS3071 Acceptance Criteria - Magnetic Particle, Fluorescent P
15、enetrant and Contrast Dye Penetrant Inspection AS7477 Bolts and Screws, Steel, UNS S66286, Tensile Strength 130 ksi, Procurement Specification AS7478 Bolts and Screws, Steel, UNS S66286, Classification: 130 ksi/1200 F, 1800 F Solution Heat Treated, Aged After Roll Threaded, Procurement Specification
16、 for AS7481 Studs, Steel, UNS S66286, Aged After Roll Threaded, Procurement Specification for AS7482 Studs, Corrosion and Heat Resistant Steel, UNS S66286, Tensile Strength 130 ksi, 1800 F Solution Heat Treated, Aged Before Roll Threading, Procurement Specification AS8879 Screw Threads - UNJ Profile
17、, Inch, Controlled Radius Root with Increased Minor Diameter 2.1.2 U.S. Government Publications Available from the Document Automation and Production Service (DAPS), Building 4/D, 700 Robbins Avenue, Philadelphia, PA 19111-5094, Tel: 215-697-6257, http:/assist.daps.dla.mil/quicksearch/.MIL-PRF-7808
18、Lubricating Oil, Aircraft Turbine Engine, Synthetic Base SAE INTERNATIONAL AS7251C Page 3 of 24 2.1.3 ASME Publications Available from American Society of Mechanical Engineers, 22 Law Drive, P.O. Box 2900, Fairfield, NJ 07007-2900, Tel: 973-882-1170, www.asme.org.ASME B46.1 Surface Texture (Surface
19、Roughness, Waviness, and Lay) ASME Y14.36M Surface Texture Symbols 2.1.4 ASTM Publications Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, Tel: 610-832-9585, www.astm.org.ASTM E140 Standard Hardness Conversion Tables for Metals Relationship
20、Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Superficial Hardness, Knoop Hardness, and Scleroscope Hardness ASTM D3951 Commercial Packaging Standard Practice for ASTM E1417/E1417M Standard Practice for Liquid Penetrant Testing 2.1.5 AIA Publications Available from Aerospace Industrie
21、s Association, 1000 Wilson Boulevard, Suite 1700, Arlington, VA 22209-3928, Tel: 703-358-1000, www.aia-aerospace.org.NASM 1312-6 Fastener Test Methods, Method 6, Hardness 2.2 Definitions BURR: A rough edge or ridge left on the metal due to a cutting, grinding, piercing, or blanking operation. DEFECT
22、: Any nonconformance of the unit of product with specified requirements. DEFECTIVE: A unit of product which contains one or more defects. PRODUCTION INSPECTION LOT: Shall be all finished parts of the same part number, made from a single heat of alloy, heat treated at the same time to the same specif
23、ied condition, produced as one continuous run, and submitted for vendors inspection at the same time. ROOM TEMPERATURE: Ambient temperature (68 F approximately). TIGHT BURR: A burr closely compacted and binding in the periphery of a part without any loose ends and is within the dimensional limits of
24、 the part. Refer to AS1310 for definitions related to fastener torque. 2.3 Unit Symbols degree, angle F degree, Fahrenheit C degree, Celsius lbf pound-force SAE INTERNATIONAL AS7251C Page 4 of 24 in2 square inch psi pound-force per square inch in Ra microinch, roughness average lbfin pound-force inc
25、h, torque HRC hardness, Rockwell C scale % percent (1% - 1/100) cpm cycles per minute 3. TECHNICAL REQUIREMENTS 3.1 Material Shall be AMS5731, AMS5734, or AMS5853. 3.2 Design 3.2.1 Dimensions The dimensions of finished parts, after all processing, including plating, shall conform to the part drawing
26、. Dimensions apply after plating.3.2.2 Geometric Tolerances Part features shall be within the geometric tolerance specified on the part drawing when tested by conventional measuring methods, except for bearing surface squareness shall be measured as noted in 3.4.1. 3.2.3 Surface Texture Surface text
27、ure of finished parts, prior to plating, shall conform to the requirements as specified on the part drawing, determined in accordance with ASME B46.1. Surface texture symbols per ASME Y14.36 3.3 Construction Each nut shall be a self-contained unit including the self-locking device. The locking devic
28、e shall not operate by means of separate movement from the installation and shall not depend on pressure on the bearing surface for the locking action. The locking device shall be set to meet the locking torque requirements of 3.9.3 when used with external threads that meet the requirements of 3.10.
29、 Tool marks resulting from producing the locking feature shall blend smoothly without abrupt change. 3.4 Threads UNJ thread form and dimensions in accordance with AS8879. SAE INTERNATIONAL AS7251C Page 5 of 24 3.4.1 Bearing Surface Squareness The bearing surface shall be square (flat to concave) wit
30、h the thread pitch cylinder axis within the limits specified on the part drawing. Bearing surface shall not be convex. Bearing surface squareness shall be tested using a table squareness gage and feeler gage. The squareness requirement shall apply to the complete bearing surface of the nut except th
31、at, for nonfloating plate nuts having a bearing surface exceeding 1.5 times the thread major diameter, the squareness requirement shall, unless otherwise specified on the part drawing, apply only to the portion of the bearing surface of the nut contained within a diameter equal to 1.5 times the thre
32、ad major diameter. The nuts to be inspected shall permit at least three complete turns of engagement on the thread arbor of the squareness gage; plating or coating may be stripped, if necessary, to meet this requirement. Multipiece floating plate nuts shall have the nut element removed from the reta
33、iner for checking thread squareness. 3.4.2 Plating Internal thread plating or coating allowance shall be as specified in AS8879, unless otherwise specified on the part drawing. 3.5 Heat Treatment The nuts shall be precipitation heat treated after forming to meet the performance requirements specifie
34、d. 3.5.1 Hardness Unless otherwise specified on the part drawing, the core hardness after heat treatment as in 3.5 shall be no greater than 46 HRC (see 8.1), determined in accordance with MIL-STD-1312-6 (in accordance with NASM 1312-6). The minimum limit is controlled by the axial tensile strength r
35、equirement in 3.9.1. 3.6 Fluorescent Penetrant Inspection Prior to any required plating or coating and following all forming, deformation and heat treatment, parts shall be subject to fluorescent penetrant inspection in accordance with ASTM E1417/E1417M, Type I, Sensitivity Level 2 minimum.Acceptanc
36、e criteria of surface discontinuities shall be in accordance with AS3071. 3.7 Plating Nuts shall be silver plated in accordance with AMS2411, unless otherwise specified on the part drawing. On nuts with thread sizes 0.250 inch and larger, the plating thickness shall be not less than 0.0002 inch when
37、 measured on the thread pitch diameter. Microscopic measurement on a sectioned nut shall be used as a referee method. Nuts with thread sizes 0.190 inch and smaller shall show complete plate coverage on the thread. Plating on other surfaces shall be 0.0003 to 0.0006 inch thick. 3.8 Lubrication The nu
38、ts may be provided with a wax type coating (such as cetyl alcohol) which will prevent nut-bolt seizure at initial installation provided such treatment is applicable to all production nuts of the same part number. 3.9 Performance Unless otherwise specified on the part drawing, nuts shall conform to t
39、he applicable requirements of Section 3. All tests shall be conducted on representative nuts assembled on bolts of any convenient length and on which the nuts will assemble freely, with the fingers, up to the self-locking device. SAE INTERNATIONAL AS7251C Page 6 of 24 3.9.1 Axial Tensile Strength No
40、t less than four nuts in the as-received condition and four nuts which have been heated to 1200 F 15 F, held at heat for 6 hours 0.25 hours and cooled to room temperature, shall be assembled on alloy steel bolts hardened and tempered to not lower than 40 HRC, and having threads in accordance with 3.
41、10. Each nut-bolt assembly shall be tested at room temperature in axial tension, using a bearing plate to grip the nut. The bearing plate hole diameter shall be 0.010 to 0.034 inch greater than the bolt thread basic major diameter. Bearing plate hole edges shall be broken 0.010 to 0.015 inch. Axial
42、tensile strength of the nut shall be not lower than the load values specified in Table 1 and the nuts shall not crack during test; tests need not be run to failure. The axial tensile load shall be applied to the nut slowly at a maximum rate equivalent to: 2D00078lbf/minuteLoad, u (Eq. 1) where: D =
43、Nominal major diameter of thread 3.9.1.1 Shank Nuts Nuts with shanks designed to be flared at assembly (see Figure 1) shall be tested as in 3.9.1 except that the bearing plate hole shall be 0.004 to 0.008 inch greater than the maximum allowable shank diameter. It is not necessary to flare the shank
44、for this test. The bearing plate hole shall be chamfered sufficiently to clear the shank nut bearing surface-to-shank maximum fillet.FIGURE 1 - FLANGE ASSEMBLY, FLARED SHANK NUT 3.9.2 Wrench Torque This test is applicable to wrenching nuts with hexagon or double hexagon wrenching feature. For this t
45、est only, all nuts shall be cleaned to remove all traces of any supplemental lubricant (such as wax, cetyl alcohol, etc.). At least three nuts shall be tested at room temperature for wrench torque by assembling a nut on an alloy steel bolt having sufficient strength. The nut shall be tightened again
46、st a bushing with a hole diameter as in 3.9.1 and having hardness not lower than 40 HRC, and surface roughness of 63 microinches Ra. Nuts shall withstand 12 successive applications of the torque specified in Table 2 without destroying the wrenchability of the nut. Wrenches used for this test can be
47、open ended type or socket type. 3.9.3 Locking Feature Torque The locking feature torque shall be measured and recorded for not less than 10 new nuts, selected at random from the lot, for each of the tests required in 3.9.5. Loading and conditioning for the five-cycle test of 3.9.5.2, shall be in acc
48、ordance with3.9.3.1. Test bolts shall conform to 3.10 or equivalent threaded parts. Test fixtures shall conform to 3.9.3.1.2. Tests shall beconducted at room temperature. The end of the bolt shall extend a minimum of 1.5 thread turns through the top of the nut at the start of the test. Test shall be
49、 run in such a manner that a dependable measure of torque will be obtained. The increase in temperature of the nuts during the test shall not exceed 74 F. The maximum prevailing and minimum breakaway torque (see AS1310) shall not exceed the values specified in Table 3 as required by the reusability tests in 3.9.5. SAE INTERNATIONAL AS7251C Page 7 of 24 TABLE 1 - AXIAL TENSILE LOAD Nut Axial Tensile Load
