Hardness to Tensile Correlation 2

[Hush]

Is there an ASTM spec that provides the relationship between hardness and tensile strength. I thought there was but I can't seem to find it.

In particular I'm trying to determine the minimum hardness to specify for 4140 ASTM A193 Gr B7. Hardness value will be used as a quality check. If I pick it too high I reject good material, too low and my part risks failure which will have somewhat disastorous consequences.

 

[butelja]

I'm not sure if there is an ASTM spec, but the "rule of thumb" is the tensile strength is 500 times the Birnell hardness reading. I've seen this in Machinery's Handbook, and a couple of machine design texts.

 

[TVP]

ASTM E 140 is the standard for hardness conversions, but unfortunately, it does not include tensile strength conversions. SAE J417, Hardness and Hardness Number Conversions includes approximations for tensile strength at a given hardness. The best reference if you have access to it is DIN 50150, Conversion of hardness values for metallic materials. FYI, hardness to tensile strength conversions are very good for steels in the hardened condition, worse for rolled products, etc.

 

[GRoberts]

ASTM A370 contains hardness conversions for
Austenitic and Non-Austenitic steels, with a column for approximate tensile strength also. Also, an easier way to do the brinell/tensile approximation, is to devide brinell by 2, and that is approx tinsile in KSI.

 

[GRoberts]

Just to clarify, the tensile strength approximations are only contained in the non-austenitic steel table, but this is the table you would be looking for anyway.

 

[Hush]

Thanks GRoberts, that was what I was looking for. Thanks also guys for the 2X rule of thumb.

 

[CoryPad]

If you are going to SPECIFY hardness, you should use the references TVP gave you. The rules of thumb are entirely inadequate for this purpose.

 

[Hush]

CoryPad,

Thanks for your concern but, unless I'm mistaken, the conversion charts in SAE J417 (70 USD)and DIN 50150 (150 USD) aren't likely to be more accurate than the one in ASTM A370 (8 USD).

 

[CoryPad]

Hush,

I was speaking about "tensile strength is 500 times the Birnell hardness reading" and "devide brinell by 2, and that is approx tinsile in KSI". The information contained in these quotes will not result in a well-designed part. The information contained within ASTM A 370 certainly can be used to properly specify material properties.