Yield Strength from Hardness Test

[engpes]

Is there a specified method for determining a materials yield strength and tensile strength from a hardness test?

This material is in the field and I do not have any MTR's on it.

Thank you.

 

[JStephen]

I seem to recall seeing a table of relationship between the two, but it's approximate at best, and wouldn't normally be used to confirm a particular yield strength.

 

[metengr]

No. There is no standard table for hardness to YS approximation. It would be better to determine the UTS from a standard table of hardness to ultimate tensile strength conversion and use a knock down factor of between 50 to 70% to approximate the YS.

 

[drawoh]

engpes,

My old college metallurgy text has a table showing hardness numbers related to tensile stress, which I assume to be ultimate. The table describes the relations as approximate, and it states that everything is for steel.

--
JHG

 

[weldstan]

For carbon and low alloy steels, Brinell hardness has been shown to provide a strong relationship to ultimate tensile strength but not yield strength. Because of the close relationship between Vickers and Brinell hardness, the same can be said for Vickers and UTS (up to a point)

 

[zeusfaber]

The same thing stops being true for many (but not all) high alloy steels.

A.

 

[tbuelna]

What is the material? Is it a metal? If it is a steel alloy, what heat treatment (if any) has it been put through? A steel alloy that has been case hardened will have a large difference between the case and core properties.

 

[RolMec]

assuming steel:
If you don't know the materials denomination or are not sure provide PMI positive material identification (by a handheld device)for the chemical composition.
Hardness test: can indicate the tensile strength
--> metallurgist or metlab could give you a more specific answer to a possible YS range for the US found
but there are at least 2 variables:
surface hardening
heat treatment (esp. for mechanical parts from steel)

In case of a safety relevant part I'd try to find a stocked spare & have it tested and then re-manufactured asap.

 

[racookpe1978]

Is this table in ASME Section IX, or in any of its appendices?
(Didn't see it in the Index, but there are hardness references for face hardness welding.)

 

[weldstan]

The ASM Metal's Handbook has appropriate Reference Tables

 

[LittleInch]

Even if you find something you can hang your hat on, it won't be of sufficient "strength" to actually do anything with. As noted above how do you really know if the external hardness is representative of the entire thickness? Does the material change somewhere along your line?

In these cases, your only real option is to assume some basic level of "nominal" strength base don year of manufacture, essentially A106 for pipe and Grade B for pipelines.

I can't think of a single reason for anyone in authority to sign this off based on a couple of hardness tests.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[weldstan]

engpes,
Since you have an undetermined material in the field and it is currently in use, I assume, you will need to perform a chemical check first. Hardness testing and the chemical check will only provide limited information to determine potential material grade/specification.

Is the material pipe or plate or forging or casting or structural shape? Material type will provide further limiting information.