The concept, pre-material defect, has different meanings.
Depending on processing stage, it is always to understand something else by a pre-material
defect. For a drawer a rolling defect is a pre-material defect at the basic material
in front of the drawing. From the view of a worker in a rolling mill, defects which
are already available at the billet, for example scals or cracks at the corner,
are to describe as pre-material defects. These defects then are existing usually
furthermore at the ready rod wire or steel bar, if they are not too small so that
they could burn down in the formed scale of the material. In the following example,
cracks at the billet were responsible for the defect picture at the rod wire. Distinctively
for this kind of pre-material defect, is the amplified available and wedge shaped
appearing decarburization, in the environment of the defect and the strong branching
of the crack.
25,00 mm round - spheroidised