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Rockwell test procedure.

INFORMATION.

Rockwell hardness test, a differential-depth method, the residual depth of the indent made by the indenter is measured. 

The deeper a defined indenter penetrates at a defined test force into the surface of a workpiece (specimen), the softer the tested material.

In the Rockwell method, the total test force is applied in two stages. This allows the impact of specimen surface roughness (e.g. grooves in the specimen) and measuring errors caused by backlash in indentation depth measurement to be eliminated.

THE INDIVIDUAL ROCKWELL METHODS ARE DISTINGUISHED FROM EACH OTHER AND.

The five resulting Rockwell methods use five different indenters (diamond cone with 120o curvature or a hard metal ball made from tungsten carbide with diameters of: 1/16",1/8",1/4",1/2") and six different total test forces (15, 30, 45, 60, 100, 150 kgf)..

This results in 30 different - standardised according to ISO 6508 and ASTM E18 – Rockwell scales (e.g. A, B, C, 30N, 15T) and test methods (e.g. HRA, HRBW, HRC, HR30N, HR15TW), each covering different hardness ranges and consequently the widest variety of materials and application areas (see table below and poster "Hardness testing of metallic materials").

How to select the test method


There are four main hardness tests, each with their own set of benefits and requirements. There are different standards for these tests, which explain the procedures and application of the hardness test in detail. 

When selecting a hardness test method, important considerations include: 
  • The type of material to be hardness tested
  • Whether compliance with a standard is required
  • The approximate hardness of the material
  • The homogeneity/heterogeneity of the material
  • The size of the part
  • Whether mounting is necessary
  • The number of samples to be tested
  • The required accuracy of the result
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