The influence of the composition and structure of alumina-containing slide plates on their failure and service

Abstract

One of the basic problems in the service of ladles with slide gates is the necessity of increasing the number of uses of the set of refractory parts of the sliding assembly includ~ ing the most important refractory part, the slide plate.Among the factors determining the number of uses of slide plates the most important are the stability of the stream of teemed metal, the absence of leakage occurring as the result of an increase in the diameter of the steel teeming channel and incomplete closure of it, and also the absence of wear of the contact surface of the plates. As a rule these processes depend upon the corrosion and erosion action of the metal being teemed on the refractory and to a significant degree are determined by the capacity of the molten metal to penetrate into it.A study of the structure of mineral composition of type KP-95 corundum plates to Technical Specification 14-8-385-81 after service in 160-ton ladles in teeming of metal into molds made it possible to reveal the basic physicotechnical parameters responsible for their corrosion and erosion resistance.In inspection of plates a zonal structure of them was observed in the zone of contact. The little-changed zone (largest portion of the plate) has a light gray color while the dense reaction zone up to I nun wide is grayish brown. The petrographic investigation showed that the little changed zone has a practically single-mineral composition consisting of corundum in the form of prismatic or lamellar crystals with a length of 0.007-0.02 mm. The narrow intervals between them are filled with glass, which constitutes less than 1% of the volume.The composition of the reaction zone indicates intense interaction of the refractory with the metal and the slag. The main portion of the zone (50-60% of the area) consists of long prismatic or acicular crystals of brownish color with an index of refraction n~ varying from 1.83 • 0.01 to 1.96 • 0.01*,.10-30% of the area of the specimen surface is occupied with crystals of spinellide with n = 1.60 • 0~ and in some places it is crystallized into dendrites with n -1.64 • 0.02, apparently of the gehlenite series.