Learn More About Rockwell Hardness Testing
The Rockwell Hardness Test is generally a non-destructive test performed on samples when it is necessary to determine how hard a material is. Hugh M. Rockwell (1890–1957) and Stanley P. Rockwell (1886–1940) from Connecticut co-invented the first tester and a patent was granted in 1919. The Rockwell Hardness test is generally considered easier to perfom compared to other methods suck as Vickers or Brinell.
Hardness is defined as a material’s resistance to permanent indentation. Current Rockwell Hardness test methods are specified in ASTM E-18 and anyone wishing to perfrom a Rockwell Hardness test should become familiar with this test standard.
Test Procedure
Each time a test is performed two loads are applied to the sample being tested. First, a preload (Minor Load) is applied and then a large (Major Load) is applied to the same spot on the material being tested. The difference between the Minor Load and Major Load is measured and this value is converted to a dimensionless number which corresponds to one of the Rockwell Hardness scales such as HRA, HRB, HRC, etc. The last letter indicates the Rockwell Hardness scale being referenced.
There are several different Rockwell Scales each denoted by a single letter. Each scale requires different loads or indenters, so careful consiuderation should be given to which scale you are working with when evaluating results.
Scale
Abbreviation
A
HRA
B
HRB
C
HRC
D
HRD
E
HRE
F
HRF
G
HRG
H
HRH
K
HRK
Superficial Scales
The Rockwell Hardness test also uses superficial scales. These use lower loads and shallower indentions when a sample may be too brittle or thin for a standard Rockwell Hardenss Test.
Superficial Rockwell hardness tester: 15N, 30N, 45N, 15T, 30T, 45T, 15W, 30W, 45W, 15X, 30X, 45X, 15Y, 30Y, 45Y
Polymer/Plastic Scales
There are also Rockwell Hardness Scales used for polymers and plastics. Those are scales R, L, M, E and K. Like other scales different sized indenters are used depending on the scale.
United's TRU-BLUE II Rockwell Hardness Tester is available in a variety of configurations depending on your requirements. The TB II Meets all NIST, ISO, CE, ASTM requirements and is capable of perfroming a variety of Rockwell Hardness tests including 15 Regular scales: A, B, C, D, E, F, G, H, K, L, M, N, P, S, V and 15 Superficial scales: 15N, 30N, 45N, 15T, 30T, 45T, 15W, 30W, 45W, 15X, 30X, 45X. 15Y, 30Y, 45Y
