Q&A about UCI hardness tester.
1. How big is the indentation on the surface of the workpiece to be tested?
Corresponding relationship between hardness value (HV), test force F (N) and indentation depth h (μm)：
h=0.062*√F/HV (GB/T34205-2017)
|
10N |
20N |
50N |
|
|
300HV |
11.3 |
16 |
25.3 |
|
600HV |
8.0 |
11.3 |
17.9 |
|
800HV |
6.9 |
9.8 |
15.5 |
Corresponding relationship between hardness value (HV), test force F (N) and indentation diagonal arithmetic mean value d (μm)：
HV≈0.1891*F/d²
|
10N |
20N |
50N |
|
|
300HV |
79.4 |
112.3 |
177.5 |
|
600HV |
56.1 |
79.4 |
125.5 |
|
800HV |
48.6 |
68.8 |
108.7 |
2. What are the requirements for the roughness of the surface to be measured?
The ultrasonic hardness tester has requirements on the surface roughness of the workpiece, especially when the loading force is small, the impact is more obvious. If the workpiece is too rough, the measured value will be low, or even no value. In this case, an abrasive material can be selected to improve the surface roughness of the workpiece and re-measure. The surface of the workpiece should also be clean without oil and rust.
Maximum allowable surface roughness Ra of the workpiece：
|
Test Force |
Maximum surface roughness Ra（μm） |
|
10N |
0.5 |
|
50N |
0.8 |
3. What occasions are probes with different loading forces suitable for?
The loading force of the probe depends on the hardness of the sample, the surface roughness and the thickness of the coating (plating) layer and the surface hardening layer.
Typical usage scenarios for loading force
|
Loading Force |
Typical usage scenarios |
|
10N |
Lon nitride layer of stamping dies, forgings. |
|
20N |
Flanges, gears, stamping parts, dies, crankshafts, turbine rotors, etc. |
|
50N |
Induction hardened layer and carburized layer of machine tool parts, such as camshafts, turbines, welds and heat affected zones. |
4. What is the smallest size of the workpiece that can be measured?
The thickness of the workpiece is generally not less than 5mm and the mass is not less than 300g.
For samples with a thickness of 2mm to 5mm, it is recommended to use coupling or bonding.
The thickness t of the coating (plating) layer and the surface hardening layer should not be less than 10 times the depth of the indentation.
5. Compared with the Leeb hardness tester, what are the characteristics of the ultrasonic hardness tester?
1)Ultrasonic hardness tester has a small indentation size and is less destructive to the surface of the test piece.
Comparison of indentation size between ultrasonic hardness tester 10N probe and Leeb D head
|
Hardness |
Leeb indentation depth |
UCI indentation depth |
Leeb indentation diameter |
UCI indentation diagonal |
|
300HV |
24μm |
11μm |
540μm |
