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Rockwell Hardness Tester (view source)
Revision as of 03:08, 18 January 2018
, 03:08, 18 January 2018no edit summary
Copied from Wikipedia. See Wikipedia for additional background
Copied from Wikipedia. See Wikipedia for additional background
==Scales and values==
There are several alternative scales, the most commonly used being the "B" and "C" scales. Both express hardness as an arbitrary [[dimensionless number]].
{| class="wikitable" border="1"
|+ Various Rockwell scales
|-
! Scale !! Abbreviation !! Load !! Indenter !! Use
!N
!s
|-
| A || HRA || 60 [[Kilogram-force|kgf]] || 120° diamond spheroconical<sup>†</sup> || [[Tungsten carbide]]
|100
|0.002mm
|-
| B || HRB || 100 kgf || {{convert|1/16|in|mm|adj=mid|-diameter|3}} steel sphere || Aluminium, brass, and soft steels
|130
|0.002mm
|-
| C || HRC || 150 kgf || 120° diamond spheroconical || Harder steels >B100
|100
|0.002mm
|-
| D || HRD || 100 kgf || 120° diamond spheroconical
|
|100
|0.002mm
|-
| E || HRE || 100 kgf || {{convert|1/8|in|mm|adj=mid|-diameter|3}} steel sphere
|
|130
|0.002mm
|-
| F || HRF || 60 kgf || {{convert|1/16|in|mm|adj=mid|-diameter|3}} steel sphere
|
|130
|0.002mm
|-
| G || HRG || 150 kgf || {{convert|1/16|in|mm|adj=mid|-diameter|3}} steel sphere
|
|130
|0.002mm
|-
| colspan=5 | <sup>†</sup>Also called a ''brale indenter''
|
|
|}
* Except for testing thin materials in accordance with A623, the steel indenter balls have been replaced by tungsten carbide balls of the varying diameters. When a ball indenter is used, the letter "W" is used to indicate a tungsten carbide ball was used, and the letter "S" indicates the use of a steel ball. E.g.: 70 HRBW indicates the reading was 70 in the Rockwell B scale using a tungsten carbide indenter.<ref>E18-08b Section 5.1.2.1 & 5.2.3</ref>
The ''superficial'' Rockwell scales use lower loads and shallower impressions on brittle and very thin materials. The 45N scale employs a 45-kgf load on a diamond cone-shaped Brale indenter, and can be used on dense [[ceramic]]s. The 15T scale employs a 15-kgf load on a {{convert|1/16|in|mm|adj=mid|-diameter|3}} hardened steel ball, and can be used on [[sheet metal]].
The B and C scales overlap, such that readings below HRC 20 and those above HRB 100, generally considered unreliable, need not be taken or specified.
===Typical values===
* Very hard steel (e.g. chisels, quality [[List of blade materials|knife blades]]): HRC 55–66 (Hardened High Speed Carbon and Tool Steels such as M2, W2, O1, CPM-M4, and D2, as well as many of the newer powder metallurgy Stainless Steels such as S30V, CPMS-154, ZDP-189, etc.)<ref>[https://web.archive.org/web/20080531085629/http://www.cutleryscience.com/reviews/blade_materials.html Knife blade materials]</ref>
* [[Axe]]s: about HRC 45–55
* Brass: HRB 55 (Low brass, UNS C24000, H01 Temper) to HRB 93 (Cartridge Brass, UNS C26000 (260 Brass), H10 Temper)<ref>[http://www.matweb.com matweb.com], accessed 2010-06-23</ref>
Several other scales, including the extensive A-scale, are used for specialized applications. There are special scales for measuring [[Case hardening|case-hardened]] specimens.
== Operation ==
== Operation ==