Obviously rusty spots could be seen at this plate surface.
The material should be solution annealed. A microsection examination showed an
austenitic structure with ca. 2% delta ferrite and a grain size of 7 - 8 . The
increased quantity of carbide precipitations in the microstructure allowed the
assumption that it is a not sufficient solution anneal of the plate. A nearer examination
of the structure at the surface showed amplified tiny carbide precipitations on
the grain boundaries. By the carbide precipitations the resistance against corrosion
has been reduced drastically because of the chromium withdrawal in the environment
of the carbides. Corrosion was the consequence.
mm thick - solution annealed , pickled