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Factors affecting the accuracy of the Leeb hardness tester
Sep 25, 2018

Factors affecting the accuracy of the Leeb hardness tester

Let's talk about the factors that affect the accuracy of the Leeb hardness tester.

1. Errors caused by data conversion

The error in conversion of Richter hardness to other hardness includes two aspects: on the one hand, the measurement error of the Leeb hardness itself, which involves the dispersion in the test according to the method and the measurement error for several pairs of the same type of Leeb hardness tester. On the other hand, it is the error caused by the hardness measured by different hardness test methods. This is because there is no clear physical relationship between one of the various hardness test methods, and it is affected by the unreliable measurement in the comparison.

2, the error caused by special materials

The conversion table stored in the hardness tester may deviate from the following steel grades: all austenitic steels

Heat-resistant tool steels and Leysite chrome steel (tool steel) hard materials cause an increase in the modulus of elasticity, resulting in a lower L value. This kind of steel should be tested on the cross section. Local cooling hardening will cause the L value to be high. The magnetic steel will have a low L value due to the influence of the magnetic field. Surface hardened steel, soft matrix, will lower the L value. When the hardened layer is larger than 0.8mm (0.2mm for C-type impact device), the L value will not be affected.

3. Error in gear detection

Under normal circumstances, because the tooth surface is small, the test error is relatively large. For this, the user can design the corresponding tooling according to the situation, which will help reduce the error.

4. Influence of material elasticity and plasticity

In addition to the hardness and strength, the Richter value is more related to the elastic modulus. The hardness value is a characteristic parameter of the hardness and plasticity of the material, because the composition of the two must be jointly determined. In the elastic part, firstly, it is obviously affected by the E modulus. In this respect, when the static hardness of the material is the same, and the E value is different, the material with a low E value has a larger L value.

5. Error caused by hot rolling direction

When the workpiece to be tested is formed by the hot rolling process, if the test direction is consistent with the rolling direction, the test value is low due to the large elastic modulus E, so the test direction should be perpendicular to the hot rolling direction. For example, when measuring the hardness of a cylindrical section, it should be tested in the radial direction. (General cylindrical hot rolling direction is axial).

6, the test piece magnetic should be less than 300 Gauss

7. Influence of other factors When measuring the hardness of the pipe fittings, pay attention to the pipe joints. Pay attention to the stable support. The test points should be close to the support point and parallel to the supporting force. The pipe wall is thinner and the appropriate core is placed in the pipe.

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