A batch of Cr12MoV complex mould steel, wire drawing die with ￠60 mm round hole, the diamond die after heat treatment, part of the mould hole appear oval, cause mould scrap.Generally speaking, Cr12MoV steel is microdeformed steel and should not be deformed.The metallographic analysis of severely deformed molds shows that there are a lot of eutectic carbides in the die steel, and they are banded and block-shaped.
(1) the causes of wire drawing die ellipse (deformation) this is because the wire drawing die steel in a certain direction of the distribution of the existence of uneven carbide, carbide expansion coefficient is smaller than the steel matrix was about 30%, heating it prevent mold inner hole expansion, cooling and prevent mold inner hole shrinkage, uneven deformation in the mold inner hole, make the mould of the round hole appear oval.
(2) the precautionary measures shall be adopted for the manufacture of precision and complex molds, and for the use of small carbide segregation stenciled steel, rather than for the sake of being cheap, the products produced by small steel mills shall be of poor quality.The mold steel with serious segregation of carbide should be properly forged to break the carbide crystal block, reduce the grade of uneven distribution of carbide and eliminate the anisotropy of performance.
(3) after forging of the wire drawing die steel for tempering heat treatment, make the carbide distribution uniform, fine and dispersion of sorbite tissue, thus reducing the sophisticated mould heat treatment after deformation.(4) for larger size or forging mould, can use solid solution double refining processing, make the carbide refining, uniform distribution, rounded edges and corners, can achieve the goal of reducing mold heat treatment deformation.