Use of liquid pig iron in electric-arc furnaces

Abstract

A technology for making steel in electric-arc fumaces with the use of molten pig iron [1][2][3] has come into wide use here and abroad, due to the shortage of well-prepared, high-quality scrap and a desire to shorten the heat and reduce the consumption of electric power and electrodes.The Kuznetsk Metallurgical Combine has developed and introduced a technology for making steel in the DSP-10017 furnace in electric steelmaking shop No. 2. The technology involves the replacement of part of the scrap metal by molten pig iron in accordance with the following scheme. After being filled and weighed, the hot-metal-car ladle is transported to the pouring bay of shop No. 2. It is then moved by an overhead-travelling crane to the hot-metal car, which takes the ladle to the furnace bay. The overhead-travelling crane that services the furnaces moves the ladle to the furnace. A total of 60-75 tons of pig iron (for two heats) is poured into the ladle. A total of 4--6 tons of lime, up to 5 tons of ore, and up to 10 tons of sinter are introduced into the furnace during the cold charge and the secondary addition of scrap. The carbon is oxidized by oxygen fed through a top lance at a rate of 2600-3000 m3/h and a Fuchs-made lance at a rate up to 3000 m3/h. The steel is dephosphorized by adding iron ore and lime to the furnace in batches of 100-200 kg. Immediately after the hot metal has been added, slag is discharged through the working door into a cinder pot. The pig iron used in the heats contains 4.1-4.6% C, 0.46-1.21% Si, 0.35--0.55% Mn, 0.08% P, 0.015-0.030% S, 0.01% Cr, 0.01% Ni, and 0.02% Cu.We studied the change in the temperature of the first batch of pig iron (30--40 tons) poured into the furnace after the pig was held in a 90-ton ladle for a long period of time and its surface was wanned with coke fines. It was determined that the pig could be kept in the ladle for up to 8-10 h without crystallization taking place. The temperature of the pig decreases at a rate of 0.5~ during the first hour in the ladle, 0.3~ during the second hour, and 0.26~ during the third hour. On the whole, the change in temperature t (~ during the holding period x (min) is described by the equation: t = 1/(-577.43.10-12x 2 + 319.93.10-9x -787.9.10-6), or by the simplified linear equation: t = 1264.6732 -0.3359x.On the average, the temperature of the pig iron decreases at a rate of 10~ over a period of 9-10 h. In light of these findings, it was decided that a mixer would not be built for shop No. 2.Three variants of the technology for making steel with the use of liquid pig iron were developed: 1) pouring of the pig iron into the furnace after melting of the cold charge, complete melting of the material in the well, and "jostling" of the secondary scrap charge (operation of the furnace with a cold charge and a secondary charge of scrap);2) pouring of the pig iron into the furnace after complete melting of the well portion of the cold charge and "jostling" of the cold charge (operation with just the cold charge);3) pouring of the pig iron after comple...

Factor analysis of the specific consumption of graphitized electrodes

“…In April 2009, Novokuznetsk Metallurgical Integrated Works (NMIW) performed shutdown of a blast furnace, which determined transfer to steelmak ing in electric arc furnaces without liquid cast iron. Therefore, the energetic technological conditions of steelmaking and furnace charge preparation were optimized to decrease the production costs.The optimization was performed on a DSP 100N10 furnace having bay window tapping and water cooled walls and roof and equipped with a 95 MV A transformer, an ArCos NT (Vatron) arc power regulator, and a BSE melting intensification system (which consists of 3 MW four wall fuel-oxy gen tuyere burners and three injectors for coke dust blowing.It should be noted that the technology of steelmak ing with the application of up to 50% of liquid cast iron for 40 and 100 t DSP furnaces that was developed by us and widely applied at NMIW demonstrated high tech nical-economical characteristics [1][2][3][4][5][6][7][8][9][10][11][12][13]. The subse quent activities on the optimization of the electric and operating modes of the melting intensification system (air-gas tuyere-burner, coke dust injectors) and the development and implementation of new flowcharts of bucket charge preparation and feeding sequences of slag forming materials did not result in the specific con sumption of graphitized electrodes comparable with the values achieved for operation with liquid cast iron (see table).…”

“…It should be noted that the technology of steelmak ing with the application of up to 50% of liquid cast iron for 40 and 100 t DSP furnaces that was developed by us and widely applied at NMIW demonstrated high tech nical-economical characteristics [1][2][3][4][5][6][7][8][9][10][11][12][13]. The subse quent activities on the optimization of the electric and operating modes of the melting intensification system (air-gas tuyere-burner, coke dust injectors) and the development and implementation of new flowcharts of bucket charge preparation and feeding sequences of slag forming materials did not result in the specific con sumption of graphitized electrodes comparable with the values achieved for operation with liquid cast iron (see table).…”