The Leeb hardness tester is a critical tool used in quality assurance and failure analysis. Choosing the right model is essential for users to ensure accurate and reliable results. This guide will help you understand the key factors when selecting a Leeb hardness tester, how to identify its quality, and what standards it should meet.
1. **Imported or Domestic?**
Swiss company PROCEQ introduced the Leeb hardness tester in 1977, setting global benchmarks. Many countries, including China, have adopted PROCEQ’s technical standards as their national measurement guidelines. Their testers are known for versatility, with one main unit supporting up to seven different impact devices. While imported models offer superior performance, they come at a higher cost—typically around ¥80,000 for a D-type configuration. Maintenance can also be less convenient. In contrast, domestic models are more affordable (around ¥10,000 for a similar setup), but buyers must carefully evaluate their quality and reliability before purchasing.
2. **How to Assess Quality?**
A genuine Leeb hardness tester meets international and national standards, ensuring interchangeability and accuracy. However, not all manufacturers produce high-quality units. Some may use modified designs that fall short of true Leeb standards. A real Leeb tester has several key features:
- **Interchangeable impact devices**: One main unit can work with multiple types of hammers.
- **Replaceable punches**: The tips of the impact device can be swapped without affecting readings.
- **No factory adjustments**: Once calibrated, the tester shouldn’t require manual tweaking.
- **Consistent error margins**: Measurement accuracy remains within acceptable limits across the full hardness range.
3. **Choosing the Right Model**
To select the best Leeb hardness tester, consider the following:
- Understand the size, thickness, and surface condition of the workpiece.
- Different materials (e.g., aluminum, steel, copper) affect test results due to variations in rebound modulus.
- Decide which hardness scale you need—HL, HB, HRC, HRB, HV, HS—and choose a tester that supports those measurements.
4. **Calibration and Conversion**
Leeb hardness testing is relatively new compared to traditional methods like Brinell, Rockwell, and Vickers. Although widely used, converting Leeb values to other scales requires careful calibration. The conversion depends on the material and the impact device used. Establishing these relationships often involves extensive testing to ensure accuracy.
5. **Standards and Specifications**
Several national and industry standards govern the Leeb hardness tester:
- **ZBN71010-90**: Defines technical conditions, testing methods, and calibration requirements.
- **JJG747-1999**: A national metrological standard outlining verification procedures and conversion values.
- **GB/T17394-1998**: Specifies testing principles, sample preparation, and conversion tables for various materials.
- **GB/T1172-1999**: Provides hardness-to-strength conversion data for ferrous metals.
Since the 1980s, Chinese manufacturers like Time Testing Instruments have developed and distributed Leeb testers nationwide. Their conversion charts comply with both national and international standards, ensuring accurate and consistent results for users worldwide.
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