ASTM E140 2

[aiwa7777]

Hi All,

I am trying to convert HV1 to HV5 or HV10.

1. Table 1 of ASTM E140 shows vickers hardness as HV. What is the force value ? Is it HV1 or HV5 or HV10.

2. For a carbon steel material, is vickers hardness independent of force value ? i.e. 250 HV1 = 250 HV5.

3.How do you convert HV1 to HV5 or HV10.

Thank you in advance.

 

[redpicker]

The best you can say is that for the same material the HV1 hardness and the HV5 (or HV10) hardness is that they are "approximately equal".

rp

 

[Guest102023]

I have become more and more reticent about using E140. I will convert only when necessary, and always attach a qualifying statement to the effect that the result is approximate.

 

[mrfailure]

Theoretically, there is not supposed to be a difference relative to load as the difference is indent size is accounted for. However, I had the experience recently where I used a 100g load (to allow the microindenter to be placed closer to the material surface)and registered unacceptably high hardness. Switching to 500g (which we most typically use) lowered the hardness to be in spec. Our metallographer has had similar experiences over the years and cautions use of light loads.

Aaron Tanzer

http://www.lehightesting.com

 

[redpicker]

Theoretically, there is not supposed to be a difference relative to load as the difference is indent size is accounted for. However, I had the experience recently where I used a 100g load (to allow the microindenter to be placed closer to the material surface)and registered unacceptably high hardness. Switching to 500g (which we most typically use) lowered the hardness to be in spec.

This is not uncommon. I am not sure why, but I have seen it, too. I know of no way to account for this difference, except to use the "wiggle words" of "Approximately Equal" and, if you do run into a situation where it would result in out-of-tolerance results, to make a comment that the discrepancy may be because of the difference in hardness test methods.


rp

 

[Guest102023]

mrfailure,

There is a load effect with microindentation hardness testing. Vandervoort has a good discussion in his metallography text (I don't enter the lab without it).

Certainly I do not expect absolute hardness measurement with MHT; I consider microindentation hardness testing more useful in detecting differences within a sample or between samples, especially welds. For hardened surfaces I do comparison testing on calibration blocks of similar material and known hardness.