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Technical Discussions
Pankaj Malwe
Pankaj Malwe
04:29 Apr-19-2018
Hardness Testing Method

Hi All,

We are testing hardness of Hardox 500 plate after water jet cutting. We observed difference in reading when we check with Bench hardness testing machine and Portable hardness testing machine.

What is your openion on method. How much diff we get when we go for portable.

Br- Pankaj

 
 Reply 
 
Neil Burleigh
Sales
Krautkramer Australia Pty Ltd, Australia, Joined Dec 2002, 158

Neil Burleigh

Sales
Krautkramer Australia Pty Ltd,
Australia,
Joined Dec 2002
158
07:37 Apr-19-2018
Re: Hardness Testing Method
In Reply to Pankaj Malwe at 04:29 Apr-19-2018 (Opening).

Hello Pankaj,
There are a number of methods for determining hardness of materials and you have not listed any so it is quite difficult to give an opinion.

Just as a quick note portable hardness testers can be quite reliable if you used correctly and within the limitations of that particular hardness testing method. For example when using LEEB rebound hardness testers a minimum wall thickness of 20 mm is required.

Regards

Neil Burleigh

 
 Reply 
 
Pankaj
Pankaj
08:07 Apr-19-2018
Re: Hardness Testing Method
In Reply to Neil Burleigh at 07:37 Apr-19-2018 .

Yes, I can more clarify,
Specified hardness -450-500 BHN over Hardox 500 Plate.( Thickness 50, 65, 25, 32mm )
Now when I checked with Brinell Hardness tester with 3000 KG, 10mm tungsten ball, after proper preparation of face got hardness within range.

But when our customer was checked with portable hardness tester rebound type, got hardness from 250-350 BHN.

Now its our call to demonstrate customer at site location with portable hardness tester.
So I need your suggestion about testing method, whether poratable will give proper result?

 
 Reply 
 
Bruce McPherson
Consultant
MFL Services, United Kingdom, Joined Mar 2009, 26

Bruce McPherson

Consultant
MFL Services,
United Kingdom,
Joined Mar 2009
26
09:58 Apr-23-2018
Re: Hardness Testing Method
In Reply to Pankaj at 08:07 Apr-19-2018 .

Your Brinell tester is almost certainly giving a more accurate measurement than the rebound tester.
The accuracy of a rebound tester is heavily dependant on the thickness of the sample and the surface condition of the sample.
The level of surface preparation is directly related to the size of indentation produced by the hardness tester
For testers which produce large indentations (such as your 3000Kg Brinell with 10mm ball), the level of surface preparation is not particularly critical, while testers which use a small indenter or very light loads (such as most rebound testers) require a much higher level of surface preparation.
It's quite probable that your client has tested the Hardox plate without first preparing the surface to a smooth enough finish and is therefore obtaining inaccurate readings with his rebound tester

Regards

Bruce McPherson

 
 Reply 
 

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