PRODUCTION AND EQUIPMENT UNMOLDED REFRACTORY MATERIAL PRODUCED BY OOO GRUPPA MAGNEZIT FOR FILLING THE STEEL DISCHARGE CHANNEL OF STEEL POURING LADLES

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 SiO2 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. Various starting materials are used: fuzed powder with a minimum impurity content that are inclined towards forming readily melting compounds, and also chromite ores from various deposits, differing in substance composition (ferrous Refractories and Industrial Ceramics Vol. 50, No. 6, 2009