GB/T 39432-2020 in English
VALIDNon-destructive testing—Ultrasonic testing—Specification for step wedge calibration block
- Issued on:2020-11-19
- Implemented on:2021-06-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
$97.00
《GB/T 39432-2020无损检测 超声检测 阶梯试块》由TC56（全国无损检测标准化技术委员会）归口，主管部门为国家标准化管理委员会。
Introduction
Interpretation of the core content of the standard
This standard is equivalent to the ISO16946:2017 international standard, which specifies the technical requirements for steel step test blocks used for the calibration of ultrasonic testing equipment. The test blocks are made of S355J0 grade steel (domestic equivalent grade Q355C) specified in EN10025-2, and the material is isotropic through a special heat treatment process.
Key technical indicators
| Parameters | Requirements | Testing methods |
|---|---|---|
| Dimensional accuracy | Length/width±0.1mm, step thickness-0.02mm | Three-coordinate measurement |
| Surface roughness | Ra≤0.8μm | Profilometer testing |
| Acoustic performance | Longitudinal wave velocity 5920±30m/s | Water immersion ultrasonic testing |
| Internal quality | Clutter is 50dB lower than the bottom wave | 10MHz straight probe scanning |
Main points of manufacturing process
Heat treatment process:The quenching and tempering process of 920℃ quenching + 650℃ tempering is adopted, and the surface layer of 2mm needs to be removed during machining. The practice of a certain shipbuilding enterprise shows that this process can reduce the attenuation coefficient of the test block by 15%.
Ultrasonic verification:A ≥10MHz probe must be used for full-area scanning, and the water immersion method is recommended to eliminate coupling differences. The test data of Dongfang Boiler shows that the water immersion method has a 20% improvement in measurement repeatability compared to the contact method.
Comparison with international standards
Compared with ISO7963, ISO2400 and other calibration block standards, the innovation of this standard is:
- For the first time, the ultra-high precision requirement of -0.02mm when the step thickness is ≤12.5mm is clarified
- Stress relief tempering at 650℃×3h is required after quenching
- A 50dB signal-to-noise ratio requirement for background clutter and bottom wave is added
Implementation suggestions
1. Purchase verification:Suppliers should be required to provide sound velocity test reports and heat treatment curve records
2. Periodic calibration:It is recommended to re-measure the sound velocity value with a standard probe every 6 months. If the drift is greater than 15m/s, it needs to be replaced
3. Use Specifications: The case of Bohai Shipyard shows that the storage temperature fluctuation of the test block should be controlled within ±5℃
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