FORD WD 952-2013 Mechanical and Performance Requirements of Through Hardened and Carbon Restored Thread Rolling Screws with Induction Hardened Points.pdf
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1、 WORLDWIDE FASTENER STANDARD WD 952 2013-08-30 Printed copies are uncontrolled Copyright 2013 Ford Global Technologies, Inc. Page 1 of 5 Copyright Ford Motor Company Provided by HIS under license with FORD No reproduction or networking permitted without license from IHS Mechanical and Performance Re
2、quirements of Through Hardened and Carbon Restored Thread Rolling Screws with Induction Hardened Points 1. SCOPE This standard specifies the requirements for high performance through hardened and carbon restored thread rolling screws with induction hardened points which have performance capabilities
3、 beyond those normally expected of other types of tapping screws. The standard relates to screws with the standard 60 degree thread form, ranging from sizes M6 to M12 and for use in applications where fastener toughness is a prime consideration. As partial or complete decarburization of the thread o
4、f thread forming screws seriously impairs the thread rolling properties of the screw, this condition is not permitted. Decarburization as permitted by ISO 898/1 is replaced in this standard by a requirement for carbon restoration as detailed in Clause 3.2. Fasteners produced to this standard possess
5、 mechanical properties in line with ISO 898/1 property class 10.9 (010) except surface hardness. Clause 3.4 defines thread forming capability in steel up to a hardness of 150 HV and thickness equal to the screw diameter. The parameters of material hardness and thread engagement may be varied by anal
6、ysis of joint requirements and it is therefore recommended that the specific application be investigated to determine joint criteria. NOTE: Lubrication approved by Ford is permitted on parts to which this specification is applied unless otherwise specified. 1.1 REFERENCES ISO 262 General purpose met
7、ric screw threads - Selected sizes for screws, bolts and nuts ISO 898/1 Mechanical properties of fasteners - Part 1: Bolts, screws and studs. ISO 898/2 Mechanical properties of fasteners - Part 2: Nuts with specified proof load values. ISO 6157-3 Fasteners Surface Discontinuities ISO 6507-1 Metallic
8、 Materials Vickers Hardness, Part 1: Test Method SAE/USCAR-8 Grain Flow Pattern for Bolts and Screws WSS-M99A3-A Embrittlement Avoidance 2. MATERIALS Screws shall be made from cold heading quality fully killed, fine grain, spherodized annealed steel wire. Material shall meet the chemical composition
9、 limits for PC10.9 per ISO 898 Part 1. 3. MECHANICAL PROPERTIES Mechanical properties defined in ISO 898/1 apply except as detailed in Table 1. Table 1 Mechanical Properties Criteria Clause Test Reference Wedge Tensile Strength 3.1 ISO 898/1 Decarburization 3.2 4.1 Surface Hardness 3.3 and Table 3 4
10、.2 Thread Forming Capability Point Hardness 3.4 3.5 4.3 4.4 WORLDWIDE FASTENER STANDARD WD 952 2013-08-30 Printed copies are uncontrolled Copyright 2013 Ford Global Technologies, Inc. Page 2 of 5 Copyright Ford Motor Company Provided by HIS under license with FORD No reproduction or networking permi
11、tted without license from IHS 3.1 WEDGE TENSILE STRENGTH Finished screws shall be hardened and tempered to achieve the minimum tensile strength for the applicable equivalent property class detailed in ISO 898/1 (See Table 4). 3.2 DECARBURIZATION During the hardening process the carbon potential of t
12、he atmosphere shall be maintained at a level slightly in excess of the carbon content of the screws being processed. This process of carbon restoration is designed to eliminate partial and total decarburization of the screw thread form. Partial or complete decarburization of the screw thread form wo
13、uld seriously impair the thread rolling properties of the screw. Carbon enrichment up to 0.1mm maximum from the surface of the screw is permitted as a result of the carbon restoration process when tested in accordance with Clause 4.1. 3.3 SURFACE HARDNESS The minimum tempering temperatures are speci
14、fied in ISO 898/1. When tested in accordance with Clause 4.2, the hardness levels as given in Table 2 shall be achieved. Table 2 Surface Hardness PROPERTY CLASS SURFACE HARDNESS (HV) 010 340 4301)1)Surface hardness shall not be more than 30 Vickers points above the measured core hardness on the prod
15、uct when the readings of both surface and core are carried out at HV 0.3. 3.4 THREAD FORMING CAPABILITY The screw shall, without permanent deformation of its own thread when viewed at 10x magnification, form a mating thread in a test plate in accordance with Clause 4.3. The thread formed by the scre
16、w in the test plate shall be capable of accepting a fastener threaded in accordance with ISO 262 tolerance class 6g and shall resist a proof load test in accordance with ISO 898/2 property class 8. 3.5 POINT HARDNESS The lead threads shall be induction hardened to achieve a minimum hardness of 450 H
17、V on one to three full threads to a depth of 0.2mm below the root as shown in Figure 1. Following induction hardening the part shall be stress relieved to 200C - 230C for one hour at temperature. 3.6 EMBRITTLEMENT All through hardened and carbon restored thread rolling screws shall meet the requirem
18、ents of WSS-M99A3-A. WORLDWIDE FASTENER STANDARD WD 952 2013-08-30 Printed copies are uncontrolled Copyright 2013 Ford Global Technologies, Inc. Page 3 of 5 Copyright Ford Motor Company Provided by HIS under license with FORD No reproduction or networking permitted without license from IHS 3.7 GRAIN
19、 FLOW Grain flow shall be verified in accordance with SAE/USCAR-8. This verification should be conducted at job setup, or whenever tooling or raw material changes are made that affect grain flow. The sample size and frequency should be identified in the manufacturers Control Plan. All records, test
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