Krautkramer DynaPOCKET - Conversion of Hardness Values

Krautkramer DynaPOCKET Issue 03, 04/2005 7-3
Conversion of hardness values The rebound hardness testing method
7.2 Conversion of hardness
values
Please observe the following with regard to the con-
version of hardness values (ref. DIN 50 150 or ASTM
E 140):
Hardness values which are measured according to
different methods cannot be converted into one an-
other via generally applicable relations.
The reason for this lies, firstly, in the fact that the pen-
etration behaviour of a material is determined by its
stress-deformation behaviour. Secondly, the shape and
the material of the indenter, the size of indentation, and
consequently the zone measured differ according to
the hardness testing method.
You should therefore know that the conversion of hard-
ness values both into one another and into tensile
strength values can be inaccurate or unacceptable,
depending on the material, its treatment and surface
finish.
Indicate hardness values according to the scale deter-
mined experimentally with the hardness testing method
used (e.g. rebound method in HL).
Only carry out conversions:
❚ if the specified test method cannot be applied, e.g.
because there is no suitable instrument available,
❚ if it’s impossible to take the required samples for the
specified test method.
Special aspects related to the conversion in the
DynaPOCKET
In the default setting, the conversion of hardness values
into other scales, which you can select on the instru-
ment, is carried out according to the instrument-specific
conversion tables; however, you can also carry out a
conversion according to DIN 50 150 or ASTM E 140. All
limitations mentioned in these standards regarding the
conversion apply.
Moreover, please keep in mind that the conversions
according to DIN 50 150 and ASTM E 140 (for Rockwell
scales) only apply to the material group 1 (low-alloy/
unalloyed steel). The instrument-specific conversion is
used for other material groups after selecting DIN 50
150 or ASTM E 140.
DynaPOCKET provides 9 material groups from which
you have to choose the one corresponding to your test
material.