The mold cavity during the molding pressure and molding temperature, due to local plastic deformation caused by mold can not continue to use the phenomenon known as plastic deformation failure, common to the working surface of the die made of carbon steel and the infiltration of carbon tool steel, form of cavity surface wrinkling, local heap collapses or depression.
　Main causes of plastic deformation failure is insufficient strength of die materials, surface hardening layer is too thin and the working temperature is higher than the tempering temperature and tempering softening caused. The failure of non normal failure, generally through the better choice of mold material or the appropriate heat treatment strengthening method to avoid. Production, regardless of the die steel, in order to ensure the cavity surface has enough strength and hardness, generally they are quenched (for carbon structural steel), carburized layer thickness is generally greater than 0.8mm.