Investigations On Structure And Properties Of Upper Nozzle For Tundish In Special Steel Metallurgy

Since the corrosion resistance and thermal shock resistance of the Al2O3-C material for the tundish upper nozzle are not well in the process of continuous casting now, the increasing of its service life and the operation continuity during the continuous casting is limited. In this work, the effects of Spinel kind and content, carbon content on properties of normal temperature, corrosion resistance and thermal shock resistance of spinel-C material were studied by changing kind and content of spinel and content of carbon. Meanwhile, in this work, it was also investigated whether the thermal expansion of two materials matched in the composite material of spinel-C work lining material and Al2O3-C body material for upper nozzle. The results of experiment were as follows: (1) When kind and content of spinel in the MA-C material were changed, modulus of rupture of MA-C material changed evidently, however, variation of their apparent porosity and bulk density was small. (2)When carbon content was 5%~10% in the MA-C material, the modulus of rupture of materials was relatively high, and with increasing of carbon content, the bulk density of materials increased gradually, but its increasing was not distinct. If graphite content was too high, the graphite would agglomerate within materials. This would destroy structure of materials and would not be favor of the continuity of frame structure of resin carbon. If graphite content was too low in the materials, the work of fracture of material would decrease when fracturing of material and would not also bad to the continuity of bonded carbon. Seen from experiment results, with adding about 8% C, the strength of sample was higher during the thermal shock. With the increasing in the C content, residual strength of sample would decrease; (3) When the ratio of thickness between MA-C material and Al2O3-C material was 15, the thermal expansion of two materials matches well and could meet the need of continuous casting. On the base of proper kind and content of spinel chosen, adding proper carbon content and using composite technology, tundish upper nozzle refractory of the better properties and service performance would be produced...