1, the impact of heating rate

Mold heat treatment deformation is generally considered to be caused by cooling, which is not correct. Mold is correct or not particular tend to produce complex mold, the mold processing of large deformation impact, compared to some of the mold heating process is apparent, heating faster, often have a greater deformation.

(1) Deformation of reasons:

Any metal to be expanded when heated, because the steel during heating within the same mold, uneven temperature throughout (i.e., uneven heating) is bound to cause expansion of various parts of the mold of the inconsistency, by heating to form a uneven internal stress. In the following phase transition point of steel temperature, uneven heating mainly produce thermal stress, uneven heating over the phase transition temperature, will produce unequal organization transformation, produces both organizational stress. Therefore, the faster the heating temperature of the mold surface and the core part of the greater difference, the greater the stress, deformation after heat treatment mold is greater.

(2) preventive measures:

Complex mold below the phase transition point should be heated slowly heated, in general, mold vacuum heat treatment deformation is much smaller than the salt bath furnace heating quenching. ? Preheating, low-alloy steel for the mold can be a preheated (550-620 C?); For high-alloy steel mold should be preheated secondary (550-620 C and 800-850 C??).

2, the heating temperature of the impact

Some manufacturers in order to ensure the mold to achieve high hardness, consider it necessary to increase the quenching temperature. But Practice shows that this approach is not appropriate for complex molds, as is the use of normal heating quenching temperature heating, heat treatment deformation than the maximum allowed temperature after heating in the minimum allowed temperature of the heated heat distortion much greater.