Billet is the final product of rolling production line. The quality of billet reflects the maturity of production technology. Today, Judian will introduce the internal quality of billet.
The internal quality of billet refers to whether the billet has correct solidification structure, segregation degree, internal cracks, inclusion content and distribution.
During the solidification process of molten steel, due to the redistribution of solute elements in the solid and liquid phase, the chemical composition of casting billet is not uniform, and the content of C, P and S in the central part is significantly higher than that in other parts, which is the central segregation.
Central segregation is often accompanied by central porosity and shrinkage, which deteriorates the mechanical properties of steel, reduces the toughness and corrosion resistance of steel, and seriously affects the quality of products.
In order to reduce the center segregation of billet, the following measures can be taken:
Reduce the content of easily separated elements P and S in steel. The pretreatment process of molten iron or desulfurization of steel barrel should be adopted to reduce the content of S below 0.01%.
The solidification structure of billet can be controlled by controlling the casting of low superheat and reducing the width of columnar strip.
Using electromagnetic stirring technology, the "bridge" of columnar crystal is eliminated, the width of central equiaxed crystal zone is increased, the central segregation is reduced or eliminated, and the quality of billet is improved.
To prevent the billet from bulging bulging deformation, for this reason, the clamping roller in the second cooling area should be strictly on the arc; The clamping roller of wide slab is better used to avoid deformation of clamping roller.
In order to compensate the shrinkage of the final solidification of the billet, the flow of residual molten steel is inhibited, and the central segregation is reduced or eliminated.
A forced cooling zone is set at the solidification end of the billet. It can prevent bulging, increase the center equiaxed crystal zone, and greatly reduce the center segregation. The effect is no less than the light pressure technology. The length of forced cooling zone and water supply can be adjusted according to pouring needs.
This is our share today and we hope it can be helpful to you. Welcome to pay attention to Luoyang Judian for more information about steel rolling production line.
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