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
20、specimens or photographs for this requirement shall conform to QS9000 record retention requirements. 3.8 SURFACE INTEGRITY For referee purposes, surface integrity shall be in accordance with WA 990. Acceptability of thread discontinuities not applicable to thread forming threads and lead area. 4. TE
21、ST METHODS 4.1 DECARBURIZATION Longitudinal sections shall be taken through the thread axis approximately one nominal diameter from the end of the screw. The specimen shall be suitably mounted and prepared for metallographic examination at not less than 100 x magnification. Prior to examination the
22、sample shall be etched in 2% Nital solution. 4.2 SURFACE HARDNESS TEST The surface hardness shall be measured using the Vickers Hardness Testing Procedure in accordance with ISO 6507. The surface hardness shall be performed on the head after removal of any finish and suitable preparation (1200 grit
23、grinding or better). Care should be taken to remove as little material as possible. For referee purposes, a micro-hardness instrument with a Vickers indenter and a 300g load shall be used. In such cases, measurements shall be made on the thread profile of a suitably prepared longitudinal metallograp
24、hic specimen. 4.3 THREAD FORMING CAPABILITY A mating thread must be formed by driving the sample screw into the test plate until a minimum of one pitch of the screw, excluding the tapered lead threads, extends beyond the plate. The axial load to ensure commencement of the thread forming process shal
25、l not exceed 90N. 4.3.1 TEST PLATE. The test plate shall be of low carbon rolled steel having a hardness of 115 to 150 HV30. Plate thickness shall be equivalent to the nominal screw diameter. Hole sizes shall be as given in Table 3. Table 3 Test Plate Thickness and Hole Sizes Nominal Thread Size and
26、 Plate Thickness (mm) 6 8 10 12 Hole Dia. (mm) Min. 5.42 7.30 9.20 11.10 Max. 5.45 7.34 9.24 11.15 NOTE: Plate thickness tolerance in accordance with ISO 5954 (for rolled plate) WORLDWIDE FASTENER STANDARD WD 952 2013-08-30 Printed copies are uncontrolled Copyright 2013 Ford Global Technologies, Inc
27、. Page 4 of 5 Copyright Ford Motor Company Provided by HIS under license with FORD No reproduction or networking permitted without license from IHS 4.4 INDUCTION HARDENING TEST The hardness test of the induction hardened zone may for routine control purposes be carried out on the screw end using a V
28、ickers 5 kg load. As an alternative or where this method is not applicable, a Vickers micro-hardness test with a 300g load may be used on a suitably mounted and prepared specimen. This method shall be a referee in case of dispute. The extent of the induction hardened zone shall be determined by visu
29、al examination of a longitudinal section taken through the induction hardened portion and etched in accordance with standard metallurgical practice (See Figure 1). Figure 1 Induction Hardened Zone (Pictorial Representation) CA style (Pictorial Representation) NOTE: The location of the induction hard
30、ened zone shall be beyond the nut anchorage point by a minimum of six full form threads in the threaded hole, to reduce potential stress cracking failures. Thus, ensuring that the induction hardened zone always passes out of the back of the nut member. 5. MARKING 5.1 SYMBOLS Marking symbol is 010 (S
31、ee Table 4). Table 4 Marking Symbol Property Class and Marking Symbol ISO 898/1 Equivalent Property Class 010 10.9 5.2 IDENTIFICATION Through hardened and carbon restored thread rolling screws with induction hardened points shall be marked by indenting or embossing with the marking symbol 010 as def
32、ined in Table 4. Marking is obligatory for hexagon screws with nominal diameters of 5mm or greater and for other products where the shape permits, preferable on the head. 5.3 TRADE (IDENTIFICATION) MARKING The trade (identification) marking of the manufacturer is mandatory on all products which are
33、required to be marked with the marking symbol. WORLDWIDE FASTENER STANDARD WD 952 2013-08-30 Printed copies are uncontrolled Copyright 2013 Ford Global Technologies, Inc. Page 5 of 5 Copyright Ford Motor Company Provided by HIS under license with FORD No reproduction or networking permitted without
34、license from IHS 6. PILOT HOLE SIZING Table 5 Recommended Pilot Hole Sizes for TAPTITE 2000Screws in Steel Duty ClassBasic Percentage of ThreadNominal Thickness Thickness Thickness Thickness ThicknessSize mm mm mm mm mm+0.03 +0.03 +0.03 +0.03 +0.03- 0.07 - 0.07 - 0.07 - 0.07 - 0.07+0.04 +0.04 +0.04
35、+0.04 +0.04- 0.08 - 0.08 - 0.08 - 0.08 - 0.08+0.05 +0.05 +0.05 +0.05 +0.05- 0.10 - 0.10 - 0.10 - 0.10 - 0.10+0.06 +0.06 +0.06 +0.06 +0.06- 0.11 - 0.11 - 0.11 - 0.11 - 0.110.3 x Screw Diameter 0.5 x Screw Diameter 0.75 x Screw Diameter 1.0 x Screw Diameter 1.25 x Screw DiameterLight* Medium-Light Med
36、ium-Heavy Full Strength Extended90% 80% 70% 65% 60%MR6 x 1.0 1.2-2.4 5.42 2.4-3.6 5.484.6-6.9 7.435.613.6-4.9 5.55 4.9-6.9 5.58 6.9-8.1MR8 x 1.25 1.6-3.1 7.27 3.1-4.9 7.35MR10 x 1.5 1.9-3.9 9.12 3.9-5.9 9.227.4-10.55.9-8.3 9.32 8.3-10.9 9.37MR12 x 1.75 2.4-4.9 10.98 4.9-7.4 11.09Pilot HolemmPilot Ho
37、lemm11.2 10.5-14.5 11.26 14.5-17.0 11.3110.9-12.9 9.416.9-8.9 7.47 8.9-10.9 7.51Pilot HolemmPilot HolemmPilot HolemmNOTES: 1) Suggested hole sizes are for mild steel, HV 115 (HRB 65) to HV 250 (HRB 100); D&R Engineers should consult with Fastener Engineering for steel applications with higher hardne
38、ss or application in light metals. *2) Not recommended for use in thread engagement less than 0.3 X screw dia. or in cast iron, consult with Fastener Engineering. 7. SUMMARY OF REVISIONS 2013 08 30 Moved Table 1 to Table 4 Moved Table 2 to Table 1 Added Clause 3.5 to the new Table 1 Moved Table 3 to
39、 Table 2 Removed Section 4.5 (Torque Wrenches) Moved Table 4 under Section 4.3.1 and relabeled Table 3 Added Section 6 (Pilot Hole Sizing) and Table 5 2010 07 20 Para 2 Delete reference to minimum tempering temperature 2009 12 08 Para 1.1 Added references Para 2 Revised material callout description and Table 1 Para 3.3 Added footnote 1 to table 3 Para 4.4 Added CA style to pictorial in Fig. 1 Para 5.3 Updated Table 4 Para 3.7 Added Para 3.8 Added
