According to the principle of Richter, as long as the material has a certain rigidity and can form a rebound, the accurate hardness of the Richter scale can be measured. However, many materials have no corresponding conversion relationship with the hardness of other systems, so the Leeb hardness tester is currently only installed. Conversion table for 9 materials. The specific materials are as follows: steel and cast steel, alloy tool steel, gray cast iron, ductile iron, cast aluminum alloy, copper-zinc alloy, copper-tin alloy, pure copper, stainless copper.
Error in data conversion
The error in the conversion of Richter hardness to other hardnesses includes two aspects: one is the measurement error of the Leeb hardness itself, which involves the dispersion in the test according to the method and the measurement error for multiple Terry's hardness testers of the same type. On the other hand, the error caused by the hardness measured by different hardness test methods is compared. 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.
Error caused by special materials
The conversion table stored in the hardness tester may be biased for the following steel grades: all austenitic steel heat-resistant tool steels and Leysite chrome steel (tool steel) hard materials cause an increase in the elastic modulus, thus making L The value is low. 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 make the L value low. When the hardened layer is larger than 0.8mm (0.2mm for the C-type impact device), the L value will not be affected.
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.
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.
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).
Effect of sample weight, roughness and thickness
The magnetic properties of the test piece should be less than 300 Gauss
Influence of other factors
When measuring the hardness of the pipe fittings, be careful: the pipe fittings should be firmly supported. The test point 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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