eFunda: Convert Hardness: Rockwell C-Scale

Rockwell C-Scale Hardness
Brale indenter, 150 kgf load

Symbol:

HRC

The Rockwell Hardness Test presses a steel or diamond hemisphere-conical penetrator against a test specimen and measures the resulting indentation depth as a gage of the specimen hardness. The harder the material, the higher the HR reading.

In the test, a minor load (10 kgf) is first applied, and the test dial (measuring the indention depth) is reset to zero. Then a major load (60, 100, or 150 kgf) is applied to create the full indention. The major load is reduced back to the minor load, and the indention depth measurement is taken.

The penetrator is usually 1/16 inch in diameter, although larger diameters (such as 1/8 inch) may be used for softer metals. Choosing the proper penetrator and the corresponding load requires experience. Some commonly used combinations are summarized below:

Scale	Condition	Application
A	Brale indenter 60 kgf load	Thin, hard sheet materials, such as tungsten carbide.
B	1/16 in diamond ball 100 kgf load	Medium/low hard materials, such as annealed carbon steels.
C	Brale indenter 150 kgf load	Materials harder than HRB 100.
D	Brale indenter 100 kgf load	Case-hardened materials.
F	1/16 inch Brale indenter 60 kgf load	Soft materials, such as bearing metals.
N	1/16 inch Superficial Brale indenter 15, 30, or 45 kgf load	Unhardened materials, such as metals softer than hardened steel or hard alloys, or where shallow indentations are desired.
T	1/16 inch diamond ball 15, 30, or 45 kgf load	Unhardened materials, such as metals softer than hardened steel, or where shallow indentations are desired.

HRC 44 approximately* =

Hardness
Symbol	Amount	Name	Suggested Range
HB (3000)	411	Brinell 10 mm Standard 3000 kgf	80~445
HB (500)	>>	Brinell 10 mm Standard 500 kgf	89~189
HB (Tungsten 3000)	411	Brinell 10 mm Tungsten 3000 kgf	80~620
HB (Indentation)	3.02 mm	Brinell Indentation	6~2
HK	456	Knoop	97~920
HM	4	Mohs	1~10
HRA	73	Rockwell A-Scale	59~86
HRB	>>	Rockwell B-Scale	41~100
HRD	59	Rockwell D-Scale	39~77
HRF	>>	Rockwell F-Scale	88~100
HR-15N	83	Rockwell Superficial 15N	69~94
HR-15T	>>	Rockwell Superficial 15T	77~93
HR-30N	63	Rockwell Superficial 30N	41~85
HR-30T	>>	Rockwell Superficial 30T	53~82
HR-45N	48	Rockwell Superficial 45N	19~76
HR-45T	>>	Rockwell Superficial 45T	28~71
HS	59	Shore Scleroscope	17~97
Approx. TS	1434 MPa	Tensile Strength (Approx.)	390~2450
HV	436	Vickers	20~1800

Legend
<<	The hardness value is below the acceptable range of the particular hardness scale.
>>	The hardness value is above the acceptable range of the particular hardness scale.
###	The hardness value is near the limit (within 15%) of the acceptable range of the particular hardness scale.

*	The many hardness tests listed here measure hardness under different experimental conditions (e.g. indenters made in different sizes, shapes, and materials, and applied with different loads) and reduce their data using different formulae. As a result, there is NO direct analytic conversion between hardness measures. Instead, one must correlate test results across the multiple hardness tests. This calculator is based on hardness data compiled from ASM Metals Reference Book 3rd ed, published by ASM International, and Machinery's Handbook 25th ed, published by Industrial Press. The calculator curve-fits multiple hardness data onto a common polynomial basis and then performs an analytic conversion. The accuracy of the conversion depends on the accuracy of the provided data and the resulting curve-fits, and on the valid ranges spanned by the different hardness tests. Converted hardness values should be used for comparative purposes only.