First of all, we'd like to report you about it by our estimated content because we did not get
your defect sample. It is hard to have disproportion in hardness partially due to the problem of
heat treatment. After Quenching, the estimated hardness is about 56~62 HRC, and after
Tempering, it is about 28~34 HRC. It is rarely that the hardness value of only the specified
part was too high, because we have been usually proceeding the tempering process in batch
type furnace. When we got your defect on only specified part of too high hardness, we
carefully guess that it was gotten the strength or the heat on the specified part. It is difficult to
find the exact reason, without your defected sample but if this problem is by our fault, it is
presumed that it might be occurred any transform due to the friction between round bars and
straightening roller M/C.