1、 WORLDWIDE ENGINEERING STANDARDS Material Specification GMW15170 Material and Performance Requirements for Induction Hardened Type TR (Thread Rolling) Tapping Screws Copyright 2013 General Motors Company All Rights Reserved January 2013 Page 1 of 7 1 Scope This standard covers material and performan
2、ce requirements applicable to Type TR (thread rolling) tapping screws, heat treated to achieve properties comparable to GMW25, property class 10.9 screws with induction hardened points, in sizes 5 mm and larger. 1.1 Material Description. 1.1.1 Material Identification. When selecting the length of sc
3、rew for any application, it should be an objective to locate the induction hardened zone beyond the exit side of the mating component as depicted in Figure 1, or to maintain a minimum length of thread engagement equal to four full form non-induction hardened threads as illustrated in Figure 2. The p
4、erformance values specified in this standard are not valid for design use unless all conditions of the application are identical to the combination of laboratory conditions described in the testing procedure. 1.2 Symbols. Not applicable. 1.3 Typical Applications. The screws covered by this specifica
5、tion are suitable for use in general engineering and structural attachments. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. ASTM E140 SAE J423 ISO 898-1 SAE J864 2.2 GM Standards/Specifications. 9986167 GMW3059
6、GMW25 GMW3179 2.3 Additional References. TMC003 Material Safety Data Sheet guidance documents (available at ). 3 Requirements 3.1 Material and Process. Screws shall be made from cold heading quality, killed steel, spheroidize annealed (60% minimum spheroidization) wire conforming to medium carbon al
7、loy steel per ISO 898-1 property class 10.9 requirements. The material shall be capable of producing fasteners free of chemical segregation, porosity and micro cracks during cold working. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo repro
8、duction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15170 Copyright 2013 General Motors Company All Rights Reserved January 2013 Page 2 of 7 Figure 1: Thread Engagement Requirements Figure 2: Thread Engagement Requirements 3.1.1 Heat Treatment. Screws s
9、hall be heat treated in a neutral atmosphere furnace. Carbon restoration of the surface to an extent not exceeding that of the core by more than 30 HV 0.3 points (3 HRC), not exceeding 393 HV 0.3. 3.1.1.1 Microstructure. Screws shall show no decarburization of the surface as determined by metallogra
10、phic examination at 100x. Partial or complete decarburization of screw thread would seriously impair the thread rolling properties of the screw. 3.1.1.2 Tempering Temperature. The minimum tempering temperature shall be 425 C. 3.1.1.3 Induction Hardening. The end portion of screws shall be induction
11、hardened to achieve a minimum surface hardness equivalent to 445 HV 0.3 (HRC 45) after stress relief. The pattern of the induction hardening shall conform to the limits designated in Figure 3, unless otherwise specified on the detail drawing. 3.1.1.4 Stress Relief. Subsequent to induction hardening,
12、 screws shall be stress relieved at 230 C minimum. Screws shall be held at the stress relieve temperature continuously for 1 h minimum. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from
13、 IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15170 Copyright 2013 General Motors Company All Rights Reserved January 2013 Page 3 of 7 3.1.2 Finish. Electroplated and coated screws shall be suitably treated subsequent to plating or coating to avoid hydrogen embrittlement in accordance with the resp
14、ective finish specification. Figure 3: Induction Hardened Point Detail Table 1: Mechanical and Performance Requirements for Thread Rolling Screws (Metric (SI) Units) Nominal Screw Size and Pitch (mm) Tensile Fracture Load (kN) Torsional Torque to Fracture (Nm) Drive Torques Finish/Lubrication GMW317
15、9 Code A Phos and oil (Nm) All Other Finishes (Nm) All Finishes with 9986167 Lubrication (Nm) minimum minimum maximum maximum maximum 5 x 0.80 14.8 9.3 4.8 6.0 4.0 6 x 1.00 20.9 16.0 7.5 9.2 6.0 8 x 1.25 38.1 40.0 16.0 20.0 13.0 10 x 1.50 60.3 81.0 28.0 35.0 23.0 12 x 1.75 87.7 143.0 46.0 55.0 35.0
16、14 x 2.00 120.0 231.0 56.6 75.1 48.0 7/16-20 77.2 125.0 39.0 47.0 30.0 Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15170 Copyright 20
17、13 General Motors Company All Rights Reserved January 2013 Page 4 of 7 3.2 Mechanical and Performance Requirements (Finished Screws). 3.2.1 Hardness. 3.2.1.1 Surface Hardness. Induction hardened threads shall have hardness equivalent to 450 HV 0.3 (HRC 45) minimum when tested as specified in 3.3.2.1
18、.1. The surface hardness outside the induction hardened zone shall not exceed the core hardness by more than 30 HV 0.3 (3 HRC) points, or exceed 392 HV 0.3 (HR15N80), when tested as specified in 3.3.2.1.2. 3.2.1.2 Core Hardness. Screws shall have core hardness beyond the induction hardened portion o
19、f 320 HV to 380 HV 0.3 (HRC 32 to HRC 39), when tested as specified in 3.3.1. 3.2.1.3 Induction Hardened Pattern. The extent of the induction hardened pattern shall be determined as specified in 3.3.2.1.3. 3.2.2 Tensile Strength. Screws, which have lengths equal to or longer than three times the nom
20、inal screw diameter, shall have tensile strengths not less than those specified in Table 1, when tested in accordance with 3.3.3. Screws of shorter lengths shall not be subjected to tensile testing. 3.2.3 Torsional Strength. Screws, which are not subject to tensile testing, shall not fail upon appli
21、cation of a torque less than the torsional value specified for the respective screw size in Table 1, when tested in accordance with 3.3.4. 3.2.4 Drive Torque. Screws shall, without deforming their own thread, form a mating internal thread in a test plate upon application of a torque equal to or less
22、 than the drive torque specified in Table 1 for the applicable screw size and finish, when tested in accordance with 3.3.5. 3.2.5 Ductility. There shall be no crack developed or separation of head from shank of screw when a permanent deformation of 10 degrees is induced between the plane of the unde
23、rhead bearing surface and a plane perpendicular to the axis of the screw, when tested in accordance with 3.3.6. 3.2.6 Hydrogen Embrittlement. Screws shall withstand without failure the hydrogen embrittlement test when tested in accordance with 3.3.7. 3.3 Test Methods. 3.3.1 Core Hardness. The core h
24、ardness shall be measured, using a HRC test, at the mid-radius of transverse section through the screw taken at a minimum distance equivalent to three times the thread pitch beyond the induction hardened portion. 3.3.2 Induction Hardened and Micro Hardness Pattern. A micro hardness instrument with K
25、noop or diamond pyramid indenter and a 500 g load shall be used. Measurements shall be made on the thread profile of a properly prepared longitudinal metallographic specimen. 3.3.2.1 For routine quality control purposes, the following methods shall be considered permissible. 3.3.2.1.1 Induction Hard
26、ened Surface. The surface hardness on induction hardened threads may be checked via file hardness testing per ASTM E140 or SAE J864. 3.3.2.1.2 Non-Induction Hardened Surface. Where the geometry of the screw head permits, the hardness may be measured on the head using a HR15N scale. Hardness tests sh
27、all be made directly on plain finish screws and on bared surfaces of plated or coated screws following removal of the finish. 3.3.2.1.3 Induction Hardened Pattern. The extent of the total induction hardened pattern shall be determined by visual inspection of a longitudinal cross section taken throug
28、h the hardened portion and etched in accordance with standard metallurgical practices (Reference SAE J423). 3.3.3 Tensile Strength Test. The sample screws shall be tested in accordance with the wedge tensile test procedures set forth in ISO 898-1 specifications for externally threaded fasteners. The
29、 angle of wedge shall be 6 degrees for screws on which the threads extend to within one diameter or closer to the underside of head and 10 degrees for all other screws. The tensile strength of the screw shall be the maximum load occurring coincident with or prior to screw fracture (that is, screw br
30、eakage into two or more parts). 3.3.4 Torsional Strength Test. The sample screw shall be securely clamped by suitable means (Figure 4) such that the threads in the clamped length are not damaged, and that at least two full threads project above the clamping device, and that at least three full form
31、non-induction hardened threads are held within the clamping device. A blind hole may be used in place of a threaded clamping device, provided the parameters stated above are fulfilled. By means of a suitably calibrated torque-measuring device, torque shall be applied to the screw until failure of th
32、e screw occurs. The torque required to cause failure shall be recorded as the torsional strength torque. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERI
33、NG STANDARDS GMW15170 Copyright 2013 General Motors Company All Rights Reserved January 2013 Page 5 of 7 Figure 4: Torsional Test 3.3.5 Drive Test. The sample screw shall be driven into the hole in a test plate until an internal thread of full major diameter is formed completely through the full thi
34、ckness of the plate or until the screw head comes into contact with the plate, whichever occurs first. The speed of driving shall not exceed 500 rpm. (For referee purposes the speed of driving shall not exceed 30 rpm.) The axial force required to initiate threading shall not exceed 25 N for screws u
35、p to and including size 6 mm, 30 N for size 8 mm, 35 N for size 10 mm and 40 N for size 12 mm and larger. The maximum torque occurring during the test shall be recorded as the drive torque. If threading is not initiated with the axial force specified, failure to pass drive test shall be considered f
36、ailure. 3.3.5.1 Test Plate. Test plates shall be low carbon cold rolled steel having a hardness of 125 HV to 170 HV (HRB 70 to HRB 85). Test plate thicknesses and hole sizes are given in Table 2. Test holes shall be drilled or punched and redrilled, or reamed, to plus or minus 0.025 mm of the hole s
37、izes specified in Table 2. 3.3.6 Ductility Test. The sample screw shall be inserted into a hole in a hardened 10 degree wedge block, or other suitable device. The hole shall be 0.5 mm to 1.0 mm larger than the nominal screw diameter. An axial compressive load shall be applied against the top of the
38、screw head and continued until the plane of the under head bearing surface is bent permanently through 10 degrees with respect to a plane perpendicular to axis of the screw. 3.3.7 Hydrogen Embrittlement Test. Plated or coated screws shall be installed into a steel test plate as described in 3.3.5.1
39、with the head of the screw seated against a standard steel flat washer for protruding style heads or against a mating countersunk steel spacer for flat and oval style heads. Additional washers should be used under the bearing washer or spacer as necessary to provide a minimum stack thickness corresp
40、onding to the maximum unthreaded length of screws threaded full length. For longer screws having an unthreaded shank portion, cold rolled steel spacers, of a length which will insure full form thread engagement is maintained within the test plate thickness, shall be used and/or the bearing washer or
41、 countersunk spacer. The screws shall be tightened to a torque equivalent to 80% of the failure torque as determined per 3.3.7.1. The screws shall be allowed to remain in this tightened state for a period of 24 h. The original embrittlement test torque shall then be reapplied and the screws shall be
42、 disassembled by the allocation of removal torque. There shall be no evidence of failure of the screws. 3.3.7.1 Torque Failure. The failure torque shall be the average of test values obtained by tightening a minimum of five screws, assembled with washers or spacers under the head as described in 3.3
43、.5, to failure (that is, screw breakage into two or more parts). In case of thread stripping thicker plate may be used. See Table 2. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IH
44、S-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15170 Copyright 2013 General Motors Company All Rights Reserved January 2013 Page 6 of 7 Table 2: Test Plate Thicknesses and Hole Sizes for Drive Torque and Hydrogen Embrittlement Tests (Metric (SI) Units) Nominal Screw Size mm Thickness, mm Hole Diameter
45、mm 0.025 Maximum Minimum 5 x 0.8 5.5 5.0 4.55 6 x 1.0 6.5 6.0 5.40 8 x 1.25 8.6 8.0 7.30 10 x 1.5 10.7 10.0 9.20 12 x 1.75 12.8 12.0 11.00 14 x 2 12.8 12.0 12.85 7/16-20 11.7 11.0 10.50 4 Manufacturing Process 4.1 Marking. All thread rolling tapping screws conforming with this specification, except
46、slotted and recessed head styles, shall be marked permanently and clearly with the manufacturers identification and the symbol. See Figure 5. 10 Figure 5: Manufacturers Identification and Symbol 4.1.1 The symbol shall be located on the top of head and on metric screws raised 0.1 mm minimum above the
47、 surface and have a minimum overall height of 1.5 mm for the 5 and 6 mm sizes, 2.3 mm for the 8 and 10 mm sizes, and 3.2 mm for the 12 and 14 sizes. 5 Rules and Regulations 5.1 Legal Regulations. All materials must satisfy applicable laws, rules, regulations and recommendations valid in the country
48、of usage. 5.2 Language. In the event of conflict between the English and domestic language, the English language shall take precedence. 5.3 Inspection and Rejection. Samples of components or materials released to a GM material specification shall be tested for conformity with the requirements of thi
49、s material specification and approved by the responsible Engineering department prior to commencement of delivery of bulk supplies. A new approval must be received for any changes, e.g., properties, manufacturing process, location of manufacture, etc. If not otherwise agreed, all testing and documentation normally required for initial release must be completed. It is the responsibility of the supplier
