Influence of mold material selection and material on heat treatment deformation

One. Influence of mold materials
1. Selection of mold
From the consideration of simple material selection and heat treatment, a mold company chose a more complex mold with different cross-section dimensions and requiring less distortion after quenching when the T10A steel was manufactured. The hardness required was 56-60HRC. After the heat treatment, the hardness of the mold meets the technical requirements, but the mold has a large deformation and cannot be used, causing the mold to be scrapped. Later, the company used micro-deformed steel Cr12 steel, and the hardness and deformation of the mold after heat treatment met the requirements. Preventive measures: To produce molds that are sophisticated and complex and require less deformation, try to use micro-deformed steel, such as air-quenched steel.
2. Influence of mold material
A certain plant sent a batch of Cr12MoV steel to manufacture more complicated molds. The molds had round holes of Φ60mm. After the mold was heat-treated, some of the mold round holes appeared oval, causing the mold to be scrapped. In general, Cr12MoV steel is a micro-deformed steel and should not show large deformation. We performed metallographic analysis on severely deformed molds and found that the mold steel contained a large amount of eutectic carbides and was distributed in bands and blocks.
(1) Causes of mold ellipse (deformation)
This is because of the presence of uneven carbides distributed in a certain direction in the mold steel. The expansion coefficient of the carbides is about 30% smaller than that of the steel's matrix structure. It prevents the inner holes of the mold from expanding when it is heated, and prevents the inner holes of the mold from contracting when it is cooled. , Causing the inner hole of the mold to deform unevenly, so that the round hole of the mold appears oval.
(2) Preventive measures
① When manufacturing precision and complex molds, try to choose mold steel with small carbide segregation, not cheap, and choose steel with poor material produced by small steel mills.
② For die steel with severe segregation of carbides, reasonable forging should be performed to break the carbide ingots, reduce the level of uneven distribution of carbides, and eliminate anisotropy of performance.
③ The tempered heat treatment of the forged mold steel should be performed to obtain a uniform, fine and dispersed sorbite structure in carbide distribution, thereby reducing deformation after heat treatment of precision and complex molds.
④ For molds with large size or can not be forged, solid solution double thinning treatment can be used to make the carbides fine, uniformly distributed and rounded corners, which can reduce the heat treatment deformation of the mold.