Development of Non Scale Technique on Slab Heating for Grain-oriented Silicon Steel

Abstract

Characteristics of a newly developed oxidation inhibitor composed of a refractory powder, SiO₂, SiC, synthetic mica, colloidal sillica, surface active agent and coking bond have been investigated.
When slab is exposed for a long period under rigorous heating condition which causes the slab to form slag, the grain-oriented silicon steel (3% silicon steel) coated with the inhibitor shows an exellent antioxidability as compared with non-coated steel.
In provision of coating weight of 1.5 kg/m² on the slab, the iron loss due to scale formation and slag mainly composed of fayalite (2FeO.SiO₂) is reduced to one-eightieth or one-hundredth.
The production test also shows that the inhibitor film on the heated slab can be removed completely by the subsequent scale breaker and that the steel sheets after hot rolling have surfaces without defects. In addition, a high yield of production of the rolled sheets has been obtained because of the minimum scale loss.
The thermal absorptivity and conductivity of the inhibitor film are very good, and so temperature distribution state of coated slab after heating has been nearly equivalent to non-coated slab.
Magnetically, both core loss W_17/50 (W/kg) and induction B₁₀ (T) of coated slab have been nearly equivalent to non-coated slab, too.