Convert Hardness to Tensile Strength Aprx

Tensile Strength (Approximation)
An approximate relationship between the hardness and the tensile strength (of steel) is, TS(Mpa)=3.55*HB (HB=<175) else 3.38*HB (HB>175) TS(Psi)=515*HB (HB=<175) else 490*HB (HB>175) where HB is the Brinnell Hardness of the material, as measured with a standard indenter and a 3000 kgf load.

Hardness
Symbol	Amount	Name	Suggested Range
HB (3000)	408	Brinell 10 mm Standard 3000 kgf	80~445
HB (500)	>>	Brinell 10 mm Standard 500 kgf	89~189
HB (Tungsten 3000)	408	Brinell 10 mm Tungsten 3000 kgf	80~620
HB (Indentation)	3.04 mm	Brinell Indentation	6~2
HK	452	Knoop	97~920
HM	4	Mohs	1~10
HRA	72	Rockwell A-Scale	59~86
HRB	>>	Rockwell B-Scale	41~100
HRC	44	Rockwell C-Scale	19~69
HRD	58	Rockwell D-Scale	39~77
HRF	>>	Rockwell F-Scale	88~100
HR-15N	82	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	58	Shore Scleroscope	17~97
HV	432	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.

Source: efunda.com