A batch of Cr12MoV steel sent by a factory is rather messy mould with ￠60m round hole. After heat treatment, some mould round holes appear ellipse, forming mould waste.

Generally speaking, Cr12MoV steel is a slightly deformed steel and should not show a large deformation.

The metallographic analysis of the severely deformed die shows that there are many eutectic carbides in the die steel, which are distributed in bands and blocks.

Precision grinding machine processing jig grinding machine mould ellipse (deformation) of the reason is due to the die steel in a certain direction spread the existence of uneven carbide, carbide expansion coefficient is smaller than the steel matrix arrangement of around 30%, heating it stop mold inner hole expansion, the cooling and obstruct dongguan precision mold processing inner hole shortened, uneven deformation of the mold inner hole attacks, make the mould of the round hole presents ellipse.