Microdur MIC-10 Hardness Tester - Discrepancy with ASTM E140

[Guest102023]

Ten days of trying to contact GE customer service have been in vain, so I am throwing this out to the universe:

Microdur's internal conversion between Brinell and Vickers shows a difference of about 9-11 in the region of 180~220HV, the brinell number being lower.
ASTM E140 conversion tables (table 2) by contrast indicates the numbers are identical over the Rockwell B range of hardness for non-austenitic steels.

Can anyone kindly explain this?

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

 

[Duwe6]

Sounds like a software "Feature" - as salesmen describe a 'bug' in the software. Since the machine's method of operation is closer to Vickers than Brinell, I'd record HV and later use ASTM E140 to convert by hand. It is possible what you are seeing is a rounding of a very long digital measurement; MIC-10 scans optically, and reports as a rounded off digital number. Real-World, hardness is analog. The internal, extended numbers may have been on the cusp of a change in the digital display, with HV rounding one way and BHN rounding the opposite.

 

[EdStainless]

In spite of what the theorists will suggest, hardness is an function of load and indenter style.
My internal specs require reporting of hardness in the original units, I want to know if it has been converted.
And trust me, on audit I will look at your procedure for conversion, and it's NIST traceability.

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

 

[Guest102023]

Ed,
I concur completely, I use E140 only when forced to do so, but always specify the method and equipment used to get the original result.
The ongoing train wreck referred to as field hardness testing (>80% of it is done wrong) starts with refinery gurus who still specify hardness in Brinell, a method that should be scrapped entirely IMHO.
However, my question concerns the apparent discrepancy between the instrument and ASTM.

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

 

[kjell123898]

hi,
Conversion tables are not always correct. Be aware that Vickers HV measurements are most suitable for testing of macro/microsamples for welding qualification purposes and a fixed Vickers HT machine will generate far more precise measurements than these portable instruments having a lot of conversion opportunities. A good advice is to be aware of when using portable hardnesses of materials with assumed higher values ​​which are at the limit of acceptable levels
this is not an easy matter but think that you should read and study the explanation given by Tinius Olsen.

 

[Guest102023]

I'll repeat my question, which is a very narrow one:

why the apparent discrepancy between the Microdur instrument and ASTM?

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

 

[SteveHooker]

Krautkramer use DIN 50 150 conversion tables. It is a European company.

 

[Guest102023]

So the discrepancy is between DIN 50150 and ASTM E140.
This is really quite a rabbit-hole.
Why has there not been a diplomatic row over this?

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

 

[SteveHooker]

That is why the source of hardness conversions should always be stated, and agreed on between contracted parties. Other countries have their own conversion equivalencies, as guided by their own standards professionals and administrators.

 

[EdStainless]

You left out that the Microdur is not measuring Vickers.
It measures its own units, then converts them, and then converts again.

IF you really care get a set of Ref blocks that span this range (four would be nice).
Test them using real machines (both Brinell and Vickers, maybe a couple of diff loads) and using the portable.
Then you will know where the shift lies.


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

 

[3DDave]

Hi brimstoner,

I think the forest has obscured the tree - your machine is capable of reporting *both* Brinell and Vickers.

The ASTM E140 tables that do the same conversion don't match the Microdur conversion.

Were it up to me to solve it, I'd start, as you did, with the manufacturer to supply a reason. I'd probably call sales, as they are the most sensitive part of the organization to customer concerns.

The next step is to wonder why these values would be identical over any range. While there is typically an intersection point between different scales of measure, matching them is unusual. To solve why this is true for the table in ASTM E140, contacting the ASTM or responsible group may be the only solution.

As other posters have noted, field measurements are always more difficult to make reliably, but that has obscured your case that it isn't the result that's the problem, it's the discrepancy between unit system conversions.

 

[Guest102023]

#DDave,

Your suggestion is what I finally followed; I just trusted the internal conversion, as it agreed with many of the conversion tables I was able to google, as well as DIN 50150.

3+ weeks later I have given up on GE customer service. Once upon a time when it was still Krautkramer I contacted them and got the answer I needed same day.

BTW my experience with the MIC-10 has shown me not to expect better than +/- 10 point accuracy (in the range of 150~230 HV), and that is AFTER averaging the minimum 6 readings that remain after rejecting the high and low extremes. I don't blindly trust the accuracy of any equipment just because it has a digital display.

Thanks to all. This thread may expire by the time GE answers, so I may have to start up a new one to updat.

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