This International Standard specifies the method and apparatus
— the measurement of the delta ferrite content, expressed
as Ferrite Number (FN), in largely austenitic and duplex
ferritic-austenitic stainless steel1) weld metal
through the attractive force between a weld metal sample and a
standard permanent magnet;
— the preparation and measurement of standard pads for
manual metal arc covered electrodes. The general method is also
recommended for the ferrite measurement of production welds and for
weld metal from other processes, such as gas tungsten arc welding,
gas shielded metal arc welding and submerged arc welding (in these
cases, the way of producing the pad should be defined);
— the calibration of other instruments to measure FN.
The method laid down in this International Standard is intended
for use on weld metals in the as-welded state and on weld metals
after thermal treatments causing complete or partial transformation
of ferrite to any non-magnetic phase. Austenitizing thermal
treatments which alter the size and shape of the ferrite will
change the magnetic response of the ferrite.
The method is not intended for measurement of the ferrite
content of cast, forged or wrought austenitic or duplex
ferritic-austenitic steel samples.
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