1. Indenters Selection for Rockwell / Superficial Rockwell Hardness
The indenters should be selected according to the hardness range of testing materials.
Select diamond indenters for tempered steel, quenched steel, surface hardening steel and carbides; ball indenters for soft metals; small ball indenters for harder metals; big ball indenters for softer metals and bigger ball indenters for even softer metals.
When the hardness of test samples cannot be estimated, a diamond indenter should be used first to test HRC or HRN scale. When the hardness value is smaller than a certain relevant testing range, the ball indenter can be applied.
The following requirements should also be taken into account:
a. Do not use the ball indenter to test quenched steel and carbides.
b. Choose the suitable ball indenters based on the hardness of test pieces when testing soft materials so as to make the test results lie within the test range of relevant scales.
c. Prevent the indenter from damaging the anvil when testing thin materials.
d. The diamond indenter and the diamond spot anvil can not be used at the same time.
2. Test Force Selection for Rockwell Hardness / Superficial Rockwell Hardness
The test force should be selected according to the thickness of the test piece.
Apply big test force to thick test pieces, small test force to thin test pieces and use superficial Rockwell hardness tester to test thinner specimens.
Also follow the principles below when choosing test forces:
a. When different test forces are applicable for a certain test piece, choose the biggest test force among them, because big test force can make deep indentations and the accuracy will be higher.
b. When testing thin specimens, no visible deformation trace should be observed on the back side of specimens, otherwise, it means the test force is overloaded with measuring anvil effect and it should be reduced.
c. Do not use C scale with the big test force to test carbides. Otherwise, the diamond indenter will be damaged.
3. Anvil Selection
The anvil should be selected according to the shape of the test piece.
Flat anvils are adopted by flat specimens.
V-shape anvils are used to test specimens with a cylindrical surface thick wall pipes, round bars and wires.
For tubings with inner diameter > 30mm, apply the regular hardness tester and use the spot anvil by inserting its left side into the tube to test the external surface hardness, or by exchanging the positions of indenter and anvil to test its internal surface hardness.
For tubings with inner diameter < 30mm, cut one piece from the test piece and use the flat anvil to test its internal surface.
For the thin-wall tubings with inner diameter > 4.8mm, use the model HR-1ST superficial Rockwell hardness tester.
The spot anvil can be applied to test small test pieces and those with uneven bottom surface. For small-size, deformed punching parts, the slender spot anvil can be selected.
For the bent sheets, use the flat anvil or the spot anvil and have the convex surface rest on the anvil.
For such thin and soft metal sheets as tinplates, cold-rolled thin steel sheets and thin copper strips, the best choice is diamond spot anvil.