Periclase-carbon products for electric steel-melting furnaces

Abstract

At present magnesite-carbon products are being increasingly used industrially; they include essentially the following classifications: periclase-carbon, periclase-lime-carbon, carbon-periclase, spinel-carbon, forsterite-carbon, periclase-zircon-carbon, etc. [I]. The characteristic properties of these products are high metal and slag resistance, high thermal conductivity, low porosity, the absence of scaling in service, and as a result, an increased wear resistance in the linings of furnaces.The Eastern Institute of Refractories together with the Magnezit Combine and the OrskoKhalilovsk Metallurgical Combine (OKMC) have developed and tested a technology for the production of periclase-carbon articles grade PU-I16 using sintered periclase powders. This technology can also be used in factories making magnesia refractories: Panteleimonovsk, Nikitovsk, Zaporozhe, etc.The starting materials consisted of sintered periclase powder fractions 3-1 mm and minus 0,06 mm, Taiginsk or Zaval'evsk graphite, organic bond, and an additive in the form of antioxidant (Table i).In laboratory conditions these materials were mixed with the organic bond and the antioxidant, pressed into specimens of diameter and height 50 mm, dried at 120-170~ (24 h), and fired in an air atmosphere at 1600~ with a soak of 5 h.With increase in graphite content after firing there are increases in the gas permeability, mass loss, and the degree of combustion of carbon from the periclase-carbon specimens; the magnetic susceptibility of the articles is uniformly reduced (Fig. i). The gas permeability of the specimens is most sharply increased with a graphite content of more than 15%. After firing, the specimens with this content of graphite have a surface burnt-out zone 1-2 mm thick under which the graphite does not burn out from the specimens (Fig. 2).An experimental batch of periclase carbon articles grade PU-II6 containing 15% graphite was prepared at the Magnezit Combine.The components were mixed in a runner mill, and the articles were shaped on the PR-7 press at 130-150 MPa. The body weight of a single article was 13.6 kg, the dimensions 386 • 154 x 85 • 75 mm. In developing the "press-packet" technology some of the articles without drying were blocked into packets, and the remainder were dried at 180~ in tunnel driers (I day) and also packaged. The properties of the goods are shown in Table 2.The periclase-carbon goods before drying and after drying are quite strong, and have a low porosity. During drying about 3.4% of the volatiles are distilled off, and there is an increase in the magnetic susceptibility of the goods. The refractoriness under load is above 1700~Complex thermal analysis shows that at 250-300~ the organic bond starts | burn in the articles and at 580~ the graphite starts to burn (Fig. 3a). After firing at i~ 0~ (soaking for 5 h) in air the degree of combustion of the carbon is 42.1%, the gas permeability i0.2 ~m 2, the specific magnetic susceptibility 32.7.10 -6 cm3/g. The periclase-carbon articles were used to build the walls of two 10...