This standard specifies the properties of carburized steel self-tapping screws and the corresponding test methods. The thread should comply with GB/T 5280, and the thread specifications are ST2.2 to ST8. GB/T 3098.5-2000 Mechanical properties of fasteners Self-tapping screws GB/T3098.5-2000 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Mechanical properties of fastenersSelf-tapping screws
Mechanical properties of fastenersGB/T3098.5--2000
Tapping screws
Approved and issued by: State Administration of Quality and Technical SupervisionDate of issuance: September 26, 2000
Implementation date: February 1, 2001
145-1
ISO Foreword
ISC) (International Organization for Standardization) is a worldwide joint organization of national standards bodies (ISO member bodies) in various countries. The formulation of international standards is usually carried out through ISO's various technical committees. Each member group can also participate in the committee if it is interested in the project carried out by a technical committee. Governmental and non-governmental international organizations related to ISO may also participate in this work. ISO has close ties with the International Electrotechnical Commission (IEC) in the field of electrical standardization. Draft international standards adopted by the technical committee are distributed to all member groups for voting. Publication of an international standard requires approval by at least 75% of the member bodies voting for it.
International Standard ISO) 2702 was prepared by Technical Committee SC1, Mechanical Properties of Fasteners, ISO/TC2. The second edition is a technical revision of the first edition (ISO 2702: 1974) with deletions and additions.
ISO Introduction
The main purpose of this international standard is to ensure that self-tapping screws can tap threads that match the screw threads in the material, that the screw threads are not damaged during normal tightening, and that they do not break during installation or service. 1 Scope
This standard specifies the properties and corresponding test methods of carburizing steel self-tapping screws. The threads shall comply with GB/T5280 and the thread specifications shall be ST2.2 Sr8.
2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. The versions shown are valid at the time of publication of this standard. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest version of the following standards. G13/T4340.1—1999 Metal Vickers hardness test part: test method (eqvISO6507-1:1997) Part 1
GB/T 5030-1985
Metal small load Vickers hardness test method
GB/T 5280—1985
1478:1983)
3 Materials
Thread for self-tapping screws (idt[SO)
Self-tapping screws should be made of cold-headed, carburized steel. 4 Technical requirements
4.1 Metallographic structure and hardness
4.1.1 Surface hardness
The surface hardness of the screw after heat treatment shall be ≥450HV0.3.4.1.2 Carburized layer depth
The carburized layer depth of the screw shall comply with the requirements of Table 1. Table 1
Carburized layer depth
Thread specifications
ST2.2, ST2.6
ST2.9. ST3.3, ST3.5
ST3.9, SI4.2, ST4.8, ST5.5
ST6.3, ST8
4.1.3 Core hardness
The core hardness of the screw after heat treatment shall be: thread ≤ST3.9: 270~390HV5;
thread ≥ST4,2: 270~390HV10.
4.1.4 Microtexture
Depth of carburized layer
The microstructure between the carburized layer and the core shall not show banded hypoeutectoid ferrite. www.bzxz.net
4.2 Mechanical properties
4.2.1 Tightening performance
According to the provisions of 6.2.1, when the self-tapping screw is screwed into the test plate, it can tap out the internal thread matching it, and the thread of the screw shall not be damaged. 4.2.2 Breaking torque
When tested according to the provisions of 6.2.2, the breaking torque of the self-tapping screw shall be equal to or greater than the provisions of Table 3.
5 Acceptance
For routine acceptance tests, the expansion performance, torque and core hardness tests may be carried out, but for arbitration inspections, all technical requirements specified in this standard shall be met.
6 Test methods
6.1 Metallographic and hardness test
Surface hardness test
Vickers hardness test shall be carried out in accordance with GB/T5030. The surface hardness test shall be carried out on the plane, and preferably on the head. 6.1.2 Carburized layer depth (metallographic test)
The carburized layer depth test shall be carried out on the side of the thread, and the measuring point shall be half the distance between the top and the bottom of the tooth. However, for white tapping screws with specifications ≤ST3.9, the test shall be carried out on the bottom of the tooth. The arbitration test shall be carried out on the thread profile of the metallographic specimen using a micro-Vickers hardness test with a test force of 300g. The carburized layer depth shall be calculated from the point where the actual core hardness exceeds 30HV. 6.1.3 Core hardness test
The Vickers core hardness test shall be carried out in accordance with GB/T4340.1 and at the 1/2 radius of the cross section at a sufficient distance from the end of the screw (there should be a complete thread diameter).
6.1.4 Microstructure test
The microstructure test shall be carried out in accordance with the corresponding metallographic inspection standards. 6.2 Mechanical property test
6.2.1 Screwing property test
The screw specimen (coated or uncoated) shall be screwed into the test plate until a complete thread passes through the test plate. The test plate shall be made of low carbon steel with a carbon content of ≤0.23% and its hardness shall be 130~170HV (determined in accordance with GB/T 5030 and GB/T4340.1). The thickness of the test plate shall comply with the requirements of Table 2. Table 2
Thread specifications
Standard test
Plate thickness and hole diameter for penetration test
The test hole can be made by drilling or punching followed by drilling or reaming. The hole diameter is as specified in Table 2.
14—5- 3
Figure 1 Torque test device
1—opening and closing mold; 2—blind hole
The delivered screws are plated by the user (or commissioned by the user. The manufacturer is not responsible for the fracture caused by the coating. If the fracture occurs without any post-treatment, the manufacturer shall be responsible. Screws with peeled coating cannot be used as test pieces. 6.2.2 Destructive torque test
The shank of the screw test piece (coated or uncoated) shall be clamped in an opening and closing, threaded mold or other device that matches the screw thread; the clamping part of the screw shall not be damaged, and at least two complete threads shall extend out of the clamping device and at least two complete threads shall be clamped in the clamp except for the end of the screw. The clamping device shall have a blind hole clamp with internal thread (Figure 1), and the depth of the hole shall ensure that the fracture occurs outside the end of the screw. Use a calibrated torque measuring device to apply torque to the screw until it breaks. The screw shall meet the destructive torque specified in Table 3. 14-5- 4
Thread specification
Breaking torque
Breaking torque
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