When pouring boiling steel in continuous die casting, due to the boiling of molten steel in the crystallizer, honeycomb bubbles are easily exposed and the molten steel overflows, affecting the surface quality of the cast slab and production safety.
Boiled steel has good surface quality and is cheap. Widely used in the production of sheets and other products.
However, boiling steel cannot be deoxidized with Si, but can only be deoxidized with a small amount of Al. Because Si is high, SiO2-MnO inclusions exist in the form of strips in hot-rolled coils, which affects the stretchability. Since Si is enriched on the surface, tempering defects are easily produced on the surface of the sheet during annealing.
In order to meet the requirements of continuous investment casting, steel types with the same quality as boiling steel have been developed:
(1) RIBAND steel, its composition is C<0.10%, Mn0.2~0.6%, Si0.03~0.08%, A10.004~0.015%:
(2) Quasi-boiling steel, its composition is C<0.10%, Si0.01%, Mn0.25%, A10.006%; (3) Aluminum-killed steel, its composition is C0.03~0.06%, Si<0.02 %, Mn<0.3%, A10.02～0.05%.