The life of the sintering zone lining of rotary kilns in firing of magnesite is comparatively low and varies from 60 to 290 days.An investigation of the character and mechanism of wear of chrome-magnesite and magnesite-chromite parts in the sintering zone of rotary kilns [i, 2] showed that the reason for wear is the formation of zonality in the refractories under the influence of a constantly acting temperature gradient across the lining thickness.The formation of a working zone with a weakened structure and reduced strength causes spalling of the refractory under the action of dynamic and static loads which occur in connection with the thermal stresses.The intensity of wear is determined by the formation on the sintering zone lining of the kiln of a protective layer. In the normal method of firing of magnesite without additions a thin protective layer of periclase-forsterite and periclase-monticellite compositions (MgO ~ 82%, Si02 ~ 8%) with a high porosity and low strength is formed.Such a layer cannot reliably protect the kiln lining from wear.A resistant protective layer is formed on the lining with the addition of siderite for a short time [3]. Into a kiln first heated after repair are fed successively siderite and a mixture of it with magnesite until the formation on the lining of a 70-160-mm-thick protective layer (Fig. i). During the kiln campaign siderite is added for a short time once or twice only if necessary to eliminate strong local wear of the protective layer and the lining itself with signs of heating of the kiln shell. During delivery of siderite to the kiln for a short time the magnesite powder obtained does not differ in chemical analysis from the normal.Siderite is used in the form of blast furnace scrap (TU 14-124-6-80). The grain sizeldistribution of the sinter-fired siderite scrap is 1% coarser than 8 mm fraction, 4% 8-5 mm, 6% 5-3 mm, 27% 3-1 mm, 22% 1-0.5 mm, and 40% finer than 0.5 mm.The chemical analysis of the scrap in wt.% is Si02 4.7, A1203 2.1, Fe=03 64.1, CaO 4.9, MgO 16.8, MnO 1.4, S03 0.5, and Amcalc 6.0.Investigation of the grains of sintered siderite under the microscope showed that they consist of finely dispersed magnesioferrite (Fig. 2) Magnesite Combine.

Types of and reasons for wear of the wall linings of tunnel kilns are studied. It is established that the aftereffect of plastic deformation and spalling and scouring in the working zones are the most important wear factors. In order to normalize the operation of tunnet kilns, it is recommended to use lining refractories with less than 1.5% SiO2 and less than 8% Cr203 in the total mass and melting temperatures exceeding 1700°C and to change the design of the inner layers of the linings.In papers [ 1 -4] we mainly gave consideration to investigating the roofs of high-temperature tunnel kills (HTK). However, long-term utilization of HTK at JSC Magnezit has shown that wall wear is decisive for their lifetime.We can distinguish the following types of wall lining failure:

The search for means of improvement of refractories for rotary kilns is pressing both in our country and abroad [I].One of the directions in decreasing wear of the sintering zone lining of rotary kilns for firing of magnesite is use for its lining of refractories with a low thermal conductivity and a sufficiently heat resistant structure. This refers to a full degree to aluminosilicate refractories, which in contast to magnesiospinellide ones, are as a rule, characterized by high resistance and low thermal conductivity. Experimental linings of fireclay (ShB) and periclase-spinellide (PKhTs) parts were tested in the high-temperature zone of Magnesite Combine rotary kilns.Normally in alternating laying of acid and basic refractories [2] the design strength of the lining drops, deformation in the form of twisting of the lining is observed, and continuity of the lining is disturbed 9 This occurs for the reason that the parts are located in longitudinal rows with bonding of the transverse joints and the whole sintering zone is made as a single large panel.For the purpose of increasing the service life of the lining and ease in the repairs made, an experimental lining in the sintering zone was made as rings with ShB and PKhTs refractories alternating in the circumference and length of the kiln. The advantage of the ring lining over a lining made as a single panel is that it is elastic, accepts deformations occurring in rotation of the kiln better, and makes it possible to make repairs in small areas [3]. Sintering zones 33 m long in a 75-m kiln starting with the first meter from the opening of the hot end and 18 m long in a 50-m kiln starting with the third meter were lined using the ring method. To compensate the axial thermal expansion, 5-mmtemperature joints filled with easily combustible sheet material were made between the zones in the lining.

Preparation technology, assimilation of production and application of a starting mix in steel-pouring assemblies of steel-pouring ladles, operating under conditions of steel pouring into molds and in CBCM are provided. The material developed is used successfully in a number of Russian metallurgical enterprises.A starting mix is an unmolded refractory material used in charging the channel of a stopper-dispensing device, through which discharge of molten metal is accomplished from a smelting or transport metallurgical unit. As is well known, a starting mix should flow out freely from the pouring channel on opening the gate without additional mechanical or other action, without force, burning, etc., and it should also be inert with respect to the melt in a ladle. As a starting mix steel-pouring ladles it is traditional to use various materials: quartz sand, veined quartz, stavrolite concentrate, aluminosilicate granules of a spherical shape, etc., normally with addition of a carbon component.OOO Gruppa Magnezit has developed technology for producing starting mix grade SST-Kh, and its use has been assimilated in metallurgical enterprises. The mixture is intended for filling channels in steel-pouring ladles of different capacity, including those where extra-furnace metal treatment is proposed (in aggregates of the furnace-ladle type), evacuation of metal, including with use of an RH vacuum unit, and also in ladles operating as transport, with a prolonged dwell time of metal in a ladle from 1.5 to 3.0 h, and sometimes more. The starting mix has been created in cooperation with OAO Zlatoustov Metallurgical Plant (OAO ZMZ) that in the first stages of developing the starting mix provided the possibility of proving it. Whereas in the open-hearth production of this enterprise the starting mix, consisting of quartz sand and coke breeze, had proved itself, under conditions of the electric steel smelting workshop (ESSW) a requirement arose for using qualitatively new materials. In the ESSW metal is poured from a 15-ton ladle, equipped with one slide gate. The pouring is siphon through one central mold in four of 2.7 ton each. The main disadvantages of the mix based on SiO 2 are their high tendency towards sintering in the steel-pouring channel, and reaction with the melt as a result of which there is closing of the steel-pouring channel and arch formation in the layer of mix above this channel [1]. In this case on opening the slide gate pouring was started on burning through sintered starting mix with oxygen in the steel-pouring channel. As a result of particles of mix falling with the melt into a mold, oxidation products of the metal increased the contamination of ingots by surface defects and the susceptibility of a cast billet to oxide inclusions. An unfavorable result of using the burning-through operation includes the possibility of distortion of the profile and melting of the edges of the channel plate of the slide gate.Workers of the research section of OOO Gruppa Magnezit have developed compositions for starting mixes....

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