Hardness Value HV5 convert to HV10

[Thuhuongengineer]

Hi Friends,
My spec require hadness value 310 HV10 but The laboratory have been tested at HV5. My client reject this result and require to Re-Test hardness at HV10. I know that HV5 or HV10 is same result. You can share to me some standards or guide books to convert HV5 to HV10. Thanks you so much

 

[cloa]

What was size of the sample and size of the indentation?

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[kingnero]

I know that HV5 or HV10 is same result.

Not necessarily, although no one will say that there isn't a strong correlation. As cloa is asking, where you near the limits of HV5?

If spec asks for HV10 measurements, client is correct when they want HV10 results, not converted values from another test method.

As an answer to your question though, there is a certain code that gives (indicative ?) conversion tables.
I'll search to see if I can find the reference or the code, it's been a while since I had anything to do with destructive testing...

 

[TVP]

There is some information in ISO 18265 about uncertainty related to conversions between scales. There is some information showing uncertainty when converting HV5 or HV10 to HV30, but it is limited to cold working tool steels, albeit across a wide hardness range. Personally, I would have some reservations about using something like HV1 or smaller if I had specified HV10, but HV5 will be practically indistinguishable from HV10. I bet that there is more variation in the samples than in the measurements.

 

[EdStainless]

Considering that 20 years ago they would have specified an HV and no load sounds like someone is a paper pusher.
If the part is small or thin you could tell them that they used 5 in order to not exceed recommended loads, otherwise it is a slip up.
Take one piece and have ti retested a number times in both scales and show that the values are the same.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[SteveHooker]

In homogenous materials the hardness will be the same. However, the effects of surface work hardening and surface compositional variances will influence the result either way because of the depth of penetration into the material. These effects obviously cannot be generalised in conversion tables.
The customer is within their rights to enforce their contractual requirements, and your laboratory should have sought a variation in advance before taking it upon themselves to use a different test load. Of course, if you did not inform the laboratory of the contractual requirements, you will have to accept liability for the retests.
It may be possible to retest a small sample using both test loads to verify that the materials are homogenous, and satisfy your customer that the results to date are valid for that product.

 

[Guest102023]

If HV5 results are comfortably within specification, your customer is being unreasonably rigid. I am wary of conversions across hardness scales and especially to UTS, but the difference here will be minimal, certainly less than the measurement error. With hardness testing, especially on weld sections, I always keep a close eye on outside laboratories; they have a habit of carelessly and cavalierly doing hardness conversions.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[mrfailure]

Note that the differences in loads really only applies to ferritic steels, which I assume you are using. George Vandervoort wrote a paper on this very topic where he did some round robin testing at labs and found great variability in Vickers hardness when using low loads (<100g), but did not see such changes at higher loads.

Aaron Tanzer

 

[CoryPad]

Or materials with gradient structure/properties like carburizing, nitriding, induction hardening, etc. or with inhomogeneous deformation from surface to core (e.g. strain hardened bar).