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...

A DSP-IO0 electric arc furnace was placed in service in Orsk-Khalilova Metallurgical Combine in 1981. In accordance with the design the arched roof of the furnace is laid dry with PKhSE-3 and PKhSE-5 refractories.In the first campaigns the life of the roof was low (43 heats), which was the reason for conducting investigations on improving the lining.The work was done in two directions, by selection of the composition of mortar for the lining and by changing the method of lining and design of the roof.Four variations of the mortar composition were tested.All of the mixtures of powders were mixed with an aqueous solution of magnesium sulfate with a density of 1.25 g/cm s ~Table i).The introduction of even the first three variations of the mortar (series of campaigns No. 2-4) made it possible to increase the average life of the roof by i0 heats.The mortar with a filler of a mixture of magnesite powder and SMZh provided a further increase in life to an average of 84 heats.An increase in the rise of the roof from 920 to 1020 mm and laying the lining by the ring method made it possible to not only significantly reduce the bricklaying labor but also to increase the life of the roof to 103 heats per campaign.Ring lining of the roof was done in the following manner.Fourteen rings or parts placed on edge were laid and then two rings laid flat, after which the templates were placed in the electrode holes and two rows of parts were laid on edge around them.The laying was done using amortar of a mixture of magnesite powder and SMZh and the thickness of the joints was 3-5 mm. Between the second and third and the third and fourth rings joints 1-2 mm thick of roofing felt were laid.In 7 out of 55 cases there were failure of the roof support rings and flooding of the roof lining with water and, as the result, early failure of the roof.Therefore at present work is being done on selection of the optimum number of expansion joints and the points of their location.It should be noted that the new roof design operates under more severe conditions in relation to the period compared in connection with the introduction of vacuum treatment of the metal and the 20-25~ increase in the temperature of the steel before tapping.The wall lining was laid in two layers.The reinforcing layer was laid with KhM-I (GOST 5381-72) parts and the working layer with PKhS-23 and PKhS-17 (GOST 10888-76) parts 460 and 380 n~ thick, respectively.The wall life in the initial period was an average of 56 heats.To increase the wall life PKhP-80 (fused periclase--chromite) and KhPT-23 (heat resistant chromite-periclase) parts were used in nine campaigns for lining the working layer, which made it possible to increase the service life of the walls to 65-73 heats (Table 2).Orsk-Khalilova Metallurgical Combine.