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Traditional hardness measurement equipment including Rockwell, Brinell, and Vickers is stationary that require fixed workstations in segregated testing areas or labs. Mostly, these hardness measurement methods are selective, which involves destructive tests on samples. With the help of individual results, it is possible to draw statistical conclusions for the entire batches. The portability of these Leeb hardness testers helps in achieving higher inspection rates without damaging the samples, which in turn streamlines the processes at the reduced cost.
The leeb hardness tester LH03 recently developed is equipped with high energy efficiency. It has a rechargeable battery that lasts long and charges effectively to give high performance.
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With its portability and ease of handling the LH02 can also measure hardness using other scales like the HRB, HL, HV, HB, and HS scales.
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LH01 is an advanced state-of-the-art palm sized metal hardness tester with many new features. It still used our dual-coil technology which makes LH01 to have extraordinary accuracy: +/-4 HL (or 0.3% @HL800) with high contrast colour TFT display and durable metal housing.
Read moreThe traditional methods of hardness testing are based upon properly defined physical indentation hardness tests. The hardest indenters of well-defined sizes and geometries are constantly pressed into the material with a particular force. Several deformation parameters like the indentation depth in the Rockwell method, are documented to give the measurement of hardness.
According to the Leeb principle, the hardness value is taken from the energy loss of a well-defined body by affecting the sample metal, similar to the Shore scleroscope. The Leeb quotient (vr/vi) is considered as the amount of the energy loss by plastic deformation, where the impact body recovers quickly from harder test samples compared to the softer ones. This results in delivering a greater value of 1000×vr/vi. A magnetic impact body allows the deduction of velocity from the voltage induced by the body while moving through the measuring coil. The quotient 1000×vr/vi is defined as the Leeb rebound hardness unit HL.
In the traditional static tests, apply the test force uniformly with increasing magnitude, where dynamic testing methods use an instantaneous load. This test takes merely 2 seconds using the standard probe D, which leaves an indentation of only ~0.5 mm in diameter on steel or steel casting having a Leeb hardness of 600 HLD. Comparatively, a Brinell indentation on the same material will be ~3 mm equivalent to the hardness value of ~400 HBW 10/3000, having a standard-compliant measuring time of approximately 15 seconds in addition to the time taken for measuring the indentation.
What are the applications of the Leeb Hardness Tester?
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There are varied testing standards for Leeb testers, which are listed below:
o ASTM A956 “Standard Test Method for Leeb Hardness Testing of Steel Products”
o ASTM E140 – 12be1 “Standard Hardness Conversion Tables for Metals Relationship Among Vickers Hardness, Brinell Hardness, Rockwell Hardness, Knoop Hardness, Superficial Hardness, Leeb Hardness, and Scleroscope Hardness”
o DIN 50156-1 “Metallic materials – Leeb hardness test – Part 1: Test Method”
o DIN 50156-2 “Metallic materials – Leeb hardness test – Part 2: Calibration and Verification of the testing devices”
o DIN 50156-3 “Metallic materials – Leeb hardness test – Part 3: Calibration of reference blocks”
o VDI/VDE Guideline 2616 Part 1 “Hardness testing of metallic materials”
o DGZfP Guideline “Mobile Härteprüfung”
o PrEN ISO 16859-1 “Metallic materials – Leeb hardness test – Part 1: Test method”
o PrEN ISO 16859-2 “Metallic materials – Leeb hardness test – Part 2: Calibration and Verification of the testing devices”
o PrEN ISO 16859-3 “Metallic materials – Leeb hardness test – Part 3: Calibration of reference test blocks”
o ISO/DIS 16859-1 “Metallic materials – Leeb hardness test – Part 1: Test method”
o ISO/DIS 16859-2 “Metallic materials – Leeb hardness test – Part 2: Calibration and Verification of the testing devices”
o ISO/DIS 16859-3 “Metallic materials – Leeb hardness test – Part 3: Calibration of reference test blocks”
The Leeb hardness test is a dynamic method that has the following characteristics:
The Leeb hardness test works as per the guidelines of ISO 16859. In this procedure, an impact device speeds up the impact body with the help of a spring force. This velocity of the impact body is classified into three phases:
The velocities are measured without any contact with the help of an induced voltage, produced by a moving magnet in a well-defined coil of the impact device. The induced voltage signal is noted electronically. The peak values, the point of the impact phase, as well as the point of the rebound phase, help in calculating the Leeb hardness. Consider the figure given below. The ratio of rebound velocity vr to impact velocity vi, multiplied by a factor of 1000, gives the measurement of Leeb hardness. The below mentioned formula is used for calculation.
HL = (Rebound velocity/Impact velocity) * 1000 = (vr/vi) * 1000
Legend:
A – Peak value of the approach phase
B – Peak value of the rebound phase
t – Time
U – Voltage
The individual hardness testing methods distinguish from each other with respect to:
The differences between the individual hardness testing methods can be seen in the following table:
Test method | Impact velocity [m/s] | Kinetic impact energy [mJ] | Rebound velocity [m/s] | Maximum distance between indenter ball and test surface [mm] | Material of indenter | Mass of impact body [g] | Spherical radius [mm] | Application range |
HLC | 1.4 | 3.0 | 0.49 – 1.344 | 2.00 | WC-Co | 3.1 | 1.5 | 350 – 960 HLC |
HLD | 2.05 | 11.5 | 0.615 – 1.8245 | 2.00 | WC-Co | 5.45 | 1.5 | 300 – 890 HLD |
HLDL | 1.82 | 11.95 | 1.1092 – 1.729 | 2.00 | WC-Co | 7.25 | 1.39 | 560 – 950 HLDL |
HLD+15 | 1.7 | 11.2 | 0.561 – 1.513 | 2.00 | WC-Co | 7.75 | 1.5 | 330 – 890 HLD+15 |
HLE | 2.05 | 11.5 | 0.615 – 1.886 | 2.00 | PCD | 5.45 | 1.5 | 300 – 920 HLE |
HLG | 3.0 | 90.0 | 0.9 – 2.25 | 3.0 | WC-Co | 20.0 | 2.5 | 300 – 750 HLG |
HLS | 2.05 | 11.4 | 0.82 – 1.886 | 2.00 | C | 5.40 | 1.5 | 400 – 920 HLS |
The Leeb test hardness value consists of three components:
The major new features of Leeb Portable Rebound Hardness Tester includes the integration of QualiTip, a portable hardness tester with statistic data display, huge storage capacity, backlight display to use in dark areas, USB interface for both data transfer to your PC or printer as well as recharging, and much more.
A spring present in the probe projects the tungsten carbide ball-tipped indenter at the test piece. The impact velocity is measured at once prior to impact followed by on rebound. The quotient is calculated and shown as the Leeb Hardness Value. On harder materials, the rebound velocity proves to be higher than softer materials, which will absorb more impact energy.
For the proper repetitive measurements, certain conditions listed below must be met:
There are two types of Leeb hardness testers namely, bench (stationary, classical) and portable (mobile, electronic).
Since portable devices are very useful and handy, they are considered as the best solution.
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