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1. The content of inclusions increases
Inclusions in steel are the origin of cracks inside the tooling tool.
In particular, inclusions such as brittle oxides and silicates do not undergo plastic deformation during hot working, causing brittle fractures to form microcracks. In further heat treatment and use, the cracks further cause cracking of the mold.
2. Failure caused by uneven distribution of carbides
Cr12, Cr12MoV, Cr12Mo1V1 and other lees-type die steels have a large number of eutectic carbides. When the forging ratio is small or the pouring temperature is not properly controlled, the segregation of banded or meshed carbides in the steel is easy to cause the die parts to be quenched Sometimes cracks occur along the serious parts of the belt or network carbide, or the internal cracks further expand during use to cause failure.
3. Failure caused by poor forging quality
The quality of steel forging directly affects the service life of the mold.
Improper heating system and deformation process of forging will cause defects such as over-burning, surface cracking, internal cracking and corner cracking of steel.
These will reduce the service life of the mold, and even scrap directly. For the high carbon and high chromium leesite steel, due to poor thermal conductivity, if the forging heating speed is too fast, the holding time is insufficient, resulting in a large temperature difference between the inside and outside of the billet during forging, and internal cracks.
4. Poor surface quality
If the surface of the alloy die steel is severely decarburized, after machining, there is still a residual decarburized layer, so that during the final heat treatment of the die, due to the difference in the structure of the inner and outer layers, obvious stress is caused, which leads to the quenching crack of the die; on the other hand After the quenching, the hardness of the mold surface layer is low, and the cross-sectional hardness distribution is uneven, which reduces the service life of the mold.
