Frequently Asked Questions
There is no direct, universally used correlation between the different hardness scales. However, a few national standards do list hardness conversion tables, and related equations. These have arisen from many hardness readings, the values have been plotted and a conversion established. Two such standards are BS EN ISO 18265:2013[1], and ASTM E140: 2012[2]. The conversions for these standards are not exactly the same, but are similar, incorporating Vickers, Brinell, Rockwell B, and Rockwell C hardness scales, and conversions for a limited number of material types. Some other hardness scales are included in the standards, but these are used less often.
A useful conversion used extensively in applications involving H2S is that 22 HRC (Rockwell C) is equivalent to 248 HV (Vickers), which is often rounded to 250 HV.
An earlier standard, BS 860:1967[3], which has been superseded by BS EN ISO 18265:2003 gives the following equation for hardness conversion between Brinell and Vickers scales.
HB = 0.95 HV
As with all conversions, it must be appreciated that the conversion between hardness scales is approximate, not absolute.
References
- BS EN ISO 18265:2013'Metallic materials - Conversion of hardness values'. BSI, London.
- ASTM E140: 2012'Standard hardness conversion tables for metals relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Superficial hardness, Knoop hardness Scleroscope hardness and Leeb hardness'. ASTM International, West Conshohocken, PA, www.astm.org.
- BS 860:1967'Tables for comparison of hardness scales' BSI, London.
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