Assimilate and harmful trace elements
The more common endogenous assimilates are tightly sulfides, silicates, oxides, and the like. Their number and composition in steel are related to the composition of the steel, the quality of the smelting, the casting history and the deoxidation techniques. Endogenous assimilation with high melting point, agglutination precedes the matrix metal, crystallization is unimpeded, appears as a ruled angular shape; endogenous assimilation with lower melting point, due to the limitation of the agglomerated metal, the shape is mostly spherical or strip, The dendrites are distributed along the grain boundaries. The silicate component with good sulfide and plasticity, when the steel ingot is deformed by forging, is elongated in the direction of main deformation and is strip-like.
The countermeasures are:
1) Vacuum treatment of molten steel, refining outside the furnace, controlling the quality of molten steel;
2) Clean the pouring to prevent external assimilation of pollution and the entry of different metals;
3) Reasonable casting deformation and improved assimilation.