Practical rockwell hardness chart series for small areas

◆ HRA is widely used to measure hardness of carbide alloy, quenched hardening steel after carbonized, hardened thin steel strip and plate, etc. For materials HRC > 67,  it is more likely to damage the diamond indenter if we use 1471 test force. For those materials, we had better choose HRC hardness scale which has small test force and indentation.

◆ HRB is suitable to test medium hardness materials such as low and medium carbon steel after annealing treatment, malleable iron, all kinds of brass, bronze, hard aluminum alloy after solution treatment and so on. The applicable scope is 20~100 HRB. when the material hardness is under 20HV, on account of the creep of metal the specimen deformation will last for a long time under the test force. The needle on indicator dial or optical projection scale moves slowly, causing difficulty in measuring precision. While when the material hardness exceeds 100 HV, the shallow indentation depth decreases sensitivity affecting measuring precision.

◆ HRC is most applicable to testing carbon steel after quenching or low tempering, alloy steel, tool steel, die steel, as well as chilled cast iron, titanium alloy and so on. Generally, we apply HRC scale to test materials HRB>100, and HRB scale to test materials HRC<20 avoiding influence caused by glide of indenter.