GB/T 3098.23-2020 in English
VALIDMechanical properties of fasteners—M42～M72 bolts, screws and studs
- Issued on:2020-03-31
- Implemented on:2020-10-01
- File Format:PDF
- Delivery:Via email within 5 business days
$418.00
《GB/T 3098.23-2020紧固件机械性能 M42～M72螺栓、螺钉和螺柱》由TC85（全国紧固件标准化技术委员会）归口，主管部门为中国机械工业联合会。
Introduction
Analysis of the core content of the standard
GB/T3098.23-2020, as the 23rd part of the series of standards for mechanical properties of fasteners, specifically regulates the mechanical properties requirements of large-size bolts, screws and studs from M42 to M72. This standard is applicable to the key connection parts of heavy equipment such as wind turbine towers and engineering machinery.
Material Technical Requirements
| Performance Grade | Carbon Content(%) | Alloy Element Requirements | Tempering Temperature(℃) |
|---|---|---|---|
| Grade 8.8 | 0.20-0.55 | Cr≥0.30% or Ni≥0.30%, etc. | ≥500 |
| Grade 10.9 | 0.30-0.55 | Compound alloy content≥70% total | ≥500 |
The standard places special emphasis on hardenability requirements, requiring the core of the threaded section to obtain about 90% martensite structure in the hardened state, which is crucial to the reliability of large wind power bolts.
Mechanical performance indicators
Key performance comparison
- Tensile strength: 8.8 grade ≥830MPa, 10.9 grade ≥1040MPa
- Yield strength: 8.8 grade ≥660MPa, 10.9 grade ≥940MPa
- Elongation after fracture: 8.8 grade ≥12%, 10.9 grade ≥9%
- Impact energy (-20℃): both ≥27J
Taking M64×4 bolts as an example, the minimum tensile load of 10.9 grade is 2965kN, and the guaranteed load is 2366kN.
Test method system
| Test type | Applicable objects | Core parameters |
|---|---|---|
| Wedge load test | Full load capacity bolts | Fracture position, ultimate load |
| Proof load test | Thread length ≥2d | Permanent deformation ≤12.5μm |
| Decarburization inspection | All heat treated parts | Non-decarburization layer height ≥1/2H1 |
Engineering application suggestions
Application Cases in Wind Power Industry
A 5MW wind turbine tower connection uses M64×4 10.9 grade bolts. Note the following during implementation:
- Strictly monitor the tempering temperature to avoid exceeding the hardness standard
- Use ultrasonic testing to check for hydrogen embrittlement risks
- Use hydraulic tensioners during installation to ensure uniform preload
The standard specifically points out that materials experts should be consulted when the operating temperature exceeds 150°C. This is especially important for harsh environments such as offshore wind power.
Technology Evolution Analysis
Compared with the previous version, the 2020 version has the following major updates:
- Added technical requirements for M72×6 specifications
- Strengthened low-temperature impact performance indicators
- Improved the decarburization layer measurement method
- Increased the arbitration status of the re-tempering test
These changes reflect the industry's increased reliability requirements for large fasteners, especially the demand for 20 years of maintenance-free wind power equipment.
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