Introduction of rammed linings for 250-ton steel-teeming ladles at Makeevka Metallurgical Combine

Abstract

In recent years in the metallurgical plants of the country greater use is being made of monolithic rammed linings of steel-teeming ladles made with the use of sand slingers. Conversion of teeming ladles with a brick lining to a rammed lining makes it possible to increase the length of their campaign and to reduce the consumptionof ladle refractories and the costs of manual labor in lining work [1][2][3].In the open hearth shop of the Makeevka Metallurgical Combine the method of rammed llnings of the walls of 250~ton teeming ladles with the use of a UP-250 sand slinger designed by the All-Unlon Scientific-Research Institute for Mechanization in Ferrous Metallurgy has been introduced and mastered. The sand slinger is equipped with two throwing heads with a capacity of 60 mS/h of rammed mixture. The rate of rotation of the throwing head is 1490 rpm, the exit rate of the material 63 m/sec, and the rate of rotation of the sand-slinger platform controllable from 2 to 9 rpm. The machine time for ramming the lining of the walls of a single ladle (without auxiliary time) is 15-25 min.For the rammed lining of the ladles type MKG-I quartzite--clay mixture to Technical Specification 14-8-252--77 developed by the Ukrainian Scientific-Research Institute for Refractories and produced by Krasnogorovka Refractory Plant is used. The thickness of the rammed lining at the top of the ladle is 160-180 nun and at the bottom 190-220 nun. The consumption of ramming mixture for a single ladle is 21-22 tons. Practically uniform ramming over the height and perimeter of the ladle is obtained with a rate of rotation of the sand slinger platform of 6-7 rpm for the bottom of the ladle and 5-6 rpm for the top. The surface hardness of the rammed lining measured with a Model 071 hardness tester is 85 • 5 units.The rammed linings are~dried on special stands with the bottom of the ladle down with natural gas with a pressure of 0.3-0.4 MPa with a lO0-mm-diameter single line gas burner placed in the ladle to a depth of 2000 mm. To improve removal of moisture from the rammed lining in drying 12-mm-diameter steam holes located in checkerboard order with a spacing of 300-700 mm were drilled in the metal shells of the ladles. Eighty-four holes are drilled in the shell of a single ladle.With the use of KhA thermoelectric calibration transducers in combination with a KSP-4 secondary recorder, the optimum drying cycle was developed for the rammed ladle linings. The thermoelectric transducers were installed through the steam holes at the boundary between the brick reinforcing lining (base) and the rammed lining, in the center of the rammed lining, and 30-40 mm from the working surface at distances of i000, 2500, and 4000 mm from the bottom. Reaching of a temperature of ii0 • 10~ at the boundary between the reinforcing lining and the rammed layer was taken as the criterion of satisfactory drying. Satisfactory drying (without spalls, cracks, and collapsing of the lining) with the use of the burner equipment available in the shop was reached in 19-21 h with the ...