No abstract

At present the lower structure of the walls, the support belt, and the burner hatches of soaking pits are lined with scarce chromite-periclase brick. The remainder of the working chamber, except for the cover, is made of refractory concrete blocks. The use of a brick lining together with blocks reduces the level of industrialization of repair of soaking pits.To increase the industrialization of repair of heating equipment and reduce the time for it, work has been done on selection of that composition of concrete which would answer the requirements of service conditions (possess increased resistance to iron slags and refractoriness). Forsterite and magnesiosilicate [1][2][3][4][5] refractories and concrete answer these requirements.The production of such parts requires the use of a material in short supply, magnesite. For the purpose of obtaining forsterite compositions and use of production waste investigation of compositions in the system of used iron-contaminated scrap of magnesia and magnesiospinellide refractories, finely ground quartzite, is of special practical value.Used iron-contaminated scrap of magnesia and magnesiospinellide refractories (38.2%* MgO, 7.35% Cr2Os, 1.2% Feme t) was crushed in a laboratory jaw crusher and then a portion of the material was ground in a ball mill. Finely ground Ovruch quartzite (97% SiO 2) was sifted through a No. 008 sieve.The 36-mm-diameter 50-mm-high cylindrical specimens were formed by semidry pressing under a pressure of 30 N/mm 2 (imitating the process of ramming of parts) from mixtures the compositions of which are given in Table i.With an increase in finely ground quartzite content to 30% there is an increase in the linear dimensions of the specimens, which is caused by formation of forsterite. In addition their apparent density continuously increases. The open porosity has a minimum with a 10% content of finely ground quartzite in the mixture and within the limits of the experiment remains quite high (29-35%).With an increase in quartzite content the strength of the specimens at the temperature of aging of concrete increases insignificantly. After drying at II0~ with a 10% quartzite content in the mixture there is a significant increase in compressive strength and then with an increase in quartzite content practically no change in it. The character of change in the strength of specimens after firing at 1400~ is completely different. With addition of 10% quartzite the strength increases sharply and then there is also a sharp decrease with 30% quartzite. Apparently such a character of the change in strength may be explained by the fact that 10% SiO 2 is sufficient to combine all of the free MgO into forsterite and further addition of quartzite leads to weakening of the material as the result of polymorphism of the quartz.Petrographic: investigations % established that after firing at 1400~ the sample is a specimen of brow, color with a glassy luster and a fragmented structure. The fragments are *Here and subsequently wt.% is shown. %V. I. Deryabina participated in th...

Refractory concrete compounds, parts, and especially large concrete blocks play an important role in acceleration of scientific and technical progress in ferrous metallurgy [i]. In connection with this, an increase in the level of mechanization of production of silica concrete blocks as the most massive form of aprts produced by Khristoforov Refractory Block and Concrete Plant and Pervoural'sk Dinas Plant is a pressing problem.At present, in these plants silica concrete parts are produced by manual pneumatic ramming from semidry dinas-quartzite mixture [2]. The significant disadvantages of this method of production are low productivity, the impossibility of production of parts of complex configuration and thin-walled parts (the wall thickness is comparable to the thickness of the ramming heel), nonuniform compaction of concrete mixture within the limits of the whole block (as the result of layer-by-layer ramming), which in some cases leads to a layer structure, and the harmful action of vibration on the body.The method of formation of dinas-quartzite concrete parts with the use of paired rams reduces the vibration on the hand of the worker but does not eliminate the disadvantages of manual pneumatic ramming [2].Forming of concrete parts from semidry mixtures may be mechanized with the use of floating vibrocompaction [3]. The machine has not found use because of the impossibility of forming assembly loops and laying parts. One of the latest designs of a machine for mechanized ramming of blocks is the design of the Scientific-Research Institute for Mining [4]. A number of significant omissions were revealed in introduction of the machine in Khristoforov Refractory Block and Concrete Plant.Other methods of production of dense concrete blocks are also known [5-9] but for various reasons they are not used in production.In connection with the above, we have developed a method of mechanismed forming of dinas-quartz concrete parts* from semidry mixturest for parts of simple forms and from fluid mixtures for thin-walled parts and those of complex configuration.Below are considered the results of investigations related to development of the method of production of vibroformed dinas-quartzite concrete parts.A method of production of vibroformed parts of high-flow and liquid concrete mixtures with an increased water glass content (18-20%) is known [2]. However, the production of large concrete parts using this method is difficult since the formation on their surface in drying of the parts of a dense crust enriched with sodium silicate prevents migration to the surface of moisture evaporating from the inner portion of the part, which leads to formation of a damp core, deformation of the parts during drying, and a sharp reduction in their strength.