1) My understand from your reply is that :
a) the mill did not clear these minute (small) crack-lines during the production process.
these crack-line is not easily seen by naked eyes.
b) These crack-lines prolonged as time goes by due to internal accumulated stress; and
thus can be seen by the naked eyes.
c) There may be more such crack-lines.
d) Such crack-lines may be make worst during cutting, grinding, machining or
polishing processes.
e) Such crack-line will not affect the mechanical properties of the material.
2) So the mill solution is to:
a) Find any crack or crack-line that can be seen by the naked eye
b) Grind the crack or crack-line to determine the depth of the crack.
c) Cut off the area with the crack or crack-line. This will prevent further
expansion of the crack.
d) Disposed of those with crack-line
e) The balance of the material can be used.
3) Our question is:
a) How to determine how much and where to cut the material to
prevent further crack?
b) How to make a claim to the mill on those cut-off quantity that cannot be used?