An aluminoborophosphate slag neutralizer

Abstract

The service of refractories in the lining of the VP-130 and ~SPTs vacuum degassers of Orsk-Khalilovo Metallurgical Combine is characterized by severe conditions of the aggressive action of slag containing 2-4% YeO, 3-5% TiO2, 4-7% A1203, 16-22% MgO, 1-3% Cr203, 27-36% CaO, and 18-28% SiO 2. The metal is superheated in the electric furance to 1750~ as the result of its subsequent teeming in a continuous casting machine [I]. The slag basicity of 1.6-1.9 favors the formation in it of dicalcium silicate which, as is known, penetrates into the pores of the refractory and destroys it as the result of expansion of the volume in the polymorphic transformation during cooling [2][3][4].In accordance with the normally used method for reducing the corrosive action of slag on the lining it is neutralized during treatment in the vacuum degasser by supplying a slag neutralizer to the vacuum chamber.A corundum slag neutralizer to Technical Specification 14-8-489-85 and also a ramming compound to Technical Specification 14-8-359-80 are used as the slag neutralizer in Orsk-Khalilovo Metallurgical Combine.However, these materials do not influence the polymorphic transformation of dicalcium silicate.At the same time a number of elements (boron, phosphorus, etc.) stabilizing the high-temperature phase of dicalcium silicate at low temperatures are known [2].Orsk-Khalilovo Metallurgical Combine and the All-Union Institute for Refractories have developed a corundum slag neutralizer containing oxides of boron and phosphorous which neutralizes the slag and stabilizes the high-temperature phase of dicalcium silicate in it. Aluminoborophosphate concentrate, which contains these elements, is simultaneously the binder for the mixture.Commercial-grade alumina to GOST 6972-74, Kumak clay to Technical Specification 14-8-338-80, and aluminoborophosphate concentrate to Technical Specification 113-08-10-17-84 were used for the production of this slag neutralizer.The alumina is supplied to Orsk-Khalilovo Metallurgical Combine in the form of a fine powder (with a residue on a No. 0088 sieve of not more than 30%) and it is not additionally treated.Clay from the existing production line in the form of powder with passage through a No. 054 sieve of not less than 65% was used.The aluminoborophosphate concentrate was used in the form of an aqueous solution with a density of 1.5-1.6 g/cm 3.First laboratory tests were made of four compositions of slag neutralizer on cylindrical specimens with a diameter of 36 m~n and a height of 50 mm formed on a hyraulic press. A mixture with a moisture content of 22-24% was prepared in a laboratory mill.The clay was added in the form of a slip. The compositions differed in the content of clay and aluminoborophosphate concentrate.The specimens of each form were dried in a drying chamber at 100~ and heat treated at 120, 700, and 1350~In determination of the physicomechanical properties the best results were obtained after heat treatment of the specimens of composition 4 at 1350~ (Table i). This composition was recommended f...