Tungsten Carbide Button — Rockwell Hardness Testing

At present, there are several indentation hardness tests widely used, such as Rockwell hardness, Brinell hardness (HB), Vickers hardness (HV), Vickers hardness and so on. The biggest difference between Brinell hardness (HB) and Rockwell hardness is the material of indenter ball that Brinell hardness uses steel ball, Rockwell hardness uses diamond. So HB test standards are generally used in the steel before the material is relatively soft, such as when non-ferrous metals, heat treatment or after annealing; Vickers hardness is suitable for the test of large workpiece, deeper surface layer and thin plate; Rockwell hardness has been widely used in tungsten carbide button hardness testing.

Rockwell has no unit, which is a non-mechanical property of dimensionless pointers, the most common hardness scales have A, B, C three kinds, usually referred to as HRA, HRB, HRC. The hardness testing method of tungsten carbide button uses Rockwell hardness of HRA. Its initial pressure used was 98.07N (co 10kgf), using an apex angle of 120 ° diamond cone diamond indenter or ball diameter ball 1.59, 3.18mm then pressurized to 588.4N (co 60kgf), according to the final pressure mark depth to calculate hardness value. HRA measurement range is 20-88 HRA, in terms of the relationship between them is: 27HRA≈30HRB, 60HRA≈100HRB≈20HRC, 85.6HRA≈68HRC.

During the measurement, usually do not take the first value, but after taking the average of the three tests. The position of each measurement point distance should be more than 5mm, the error generally within 0.3HRA, the range expressed in the form beyond 0.3HRA. With the refinement of the raw material and the optimization of the manufacturing process, some carbide materials have reached 93-94 HRA, 20-88HRA beyond the measuring range, the project exceeded the highest HRA measurement range has become a norm. In addition, HRA ruler can be used for distinguishing the soft steel and hard steel, if the value is less than 60 HRB hardness can use HRB scale, when the hardness value is higher than 60HRA can use HRC ruler.

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