The presence of delta ferrite in a weld seam of the austenitic
steel allows the application of the method of the MMM testing.
The values of the strength of the RMF for austenitic steel weld
seams are much lower than those for weld seams of ferritic steels.
Therefore external disturbances (sources of the magnetic field,
closely located ferromagnetic objects) caneasilyandsub stantially
distort the measurement results. The magnetic image of the joint
is decided by the amount and distribution of delta ferrite. The
higher the amount of it, and the more uniform its distribution
in the weld seam, the higher the probability that disturbances
caused by the occurrence of defects will be seen in the image
of the RMF. If the distribution of delta ferrite happens to be non-
uniform, the distribution of the RMF is more often an image
of this non-uniformity rather than the result of the occurrence
of defects. This is clearly visible in the presented P12 joint—
Section 3.4.This does not exclude the use of the MMM method for