Monolithic linings in steel ladles wear out because of several factors: thermal, chemical, and mechanical.Differences in ladle service conditions make it necessary to improve existing ramming compounds and develop new ones [1][2][3][4][5][6][7][8].The authors have developed a method of testing these linings in the ladle.Blocks made of sand-slung rammings were used. They were prepared on a sand-slinger ring based on model 296-M2 with a slinger-head diameter of 670 mm. The blocks are trapezoidal in shape and correspond to the outline of linings in the slag belt of a 150-ton steel ladle. The block dimensions in the upper part are 500 • 480 • 150 mm, in the lower 480 • 460 • 150 mm, and the height is 320 mm.Blocks were made of Chasov-Yar loamy sand grade PO-16 and lean river sand from the Kaidaksk port in Dnepropetrovsk.Graphite waste, chromite, and zircon were added to the Chasov-Yar sand ramming bodies with various amounts of DN-I clay to the river-sand body. Aqueous solutions of MgSO~-7H20, H3PO~, aluminochromophosphate (TU MKhP6-78-166-73) and sulfire lye were used as binders.Blocks were tested in the slag belt of 150-ton ladles in the Petrovskii open-hearth shop. The ladles were linked with KShU-39 firebrick.The steel-discharge temperature was 1610-1620~ the metal stayed 60-90 min in the ladle during casting, and the slag basicity was ].9-2.2.The average wear of Chasov-Yar sand blocks without additives was 10.2 mm for one pouring.Adding 15% chromite and 10% graphite waste to the Chasov-Yar sand reduced the resistance. When 30% zircon was added the average block, wear per pouring dropped from 10.2 to 8.0 mm. When solutions of MgSO4o7H20 and sulfite lye were used as binders, the resistance diminished. Using orthophosphoric acid and aluminochromophosphate did not markedly increase the resistance.Blocks based on Kaidaksk river sand showed much less wear in one pouring.Their resistance increased with a fall in added clay content, i.e., when the Na20 and K20 contents were reduced.Thus, a reduction in the alkalis from 1.28 to 0.35% reduced the block wear from 10.2 to 3.4 mm per pouring.Petrographic study of the blocks after service showed that they developed zone formation when a temperature gradient and molten slag and metal were present.* The least-changed zones in most specimens showed slight cracking and surface cristobalite formation of the quartz grains. As a result of interaction between silica and the impurities in the sand with the binder and under the temperature action, the least-changed zones formed a cryptocrystalline substance, which was less frequently glassy.Combustion of organic or carbonaceous constituents (when they were present) occurs in the transition zones, and in most cases the cryptocrystalline material is converted into glassy.There is some increase in the amount of metacristobalite in the quartz grains.The working zones are very dense, have an enhanced amount of glass in the bond, much cracking, and cristobalite formation in the quartz grains; the grain surfaces are covered, and the cracks fi...
chamotte. Close to the working surface of the specimens from the slag belt we noted helenite had formed. The amount of calcium hexaaluminate in the working zones of the linings made of compound I amounted to up to 1~o; from compound II 20-25%. The maximum amounts (up to 30%) of CaO-2A1203 and CaO. A1203 were present in the working zones of the linings made of compound I. Figure 1 shows the microstructure of the working zones of the lining specimens after service in the slag belt, in the middle, and in the lower part of the ladle.During service under the action of slag and metal, we note a reduction in the refractoriness and sintering of the working zones of the ladle linings. The open porosity of the working zones was about 107o.The results of petrographic analysis indicate that in the rammed linings of the ladles made of aluminous bodies under the action of synthetic slags there forms not anorthite, but refractory calcium aiuminates. The platelike crystals of calcium hexaaluminate growing in the glass phase strengthen the surface layer of the lining, which increases its service resistance.
In the open hearth shop of Azovstal' Plant the 230-ton steel teeming ladles are being converted from a brick lining to a rammed lining with the use of a sand slinger and using type MKG-I quartz--clay compound according to Technical Specification 14-8-252--77 and developed in the Ukrainian Sclentific-Research Institute of Refractories [i].For the purpose of developing the optimum parameters for producing the rammed lining of the ladles, an investigation of the relationship of the properties of rammed samples to the production parameters of the process was first made on a laboratory sand slinger unit. The plan of the laboratory sand slinger unit is shown in Fig. I.The sand slinger unit consists of a model 296-M2 double-chute sand slinger fastened to a base, a bunker for the ramming compound, and belt feeders for supplying the compound to the sand slinger.For the purpose of eliminating hanging up of the compound, the bunkers are equipped with vibrators.Using the laboratory sand slinger unit, 500 • 400 • 150 mm rammed blocks were prepared from MKG-I quartz--clay compound produced by Krasnogorsk Refractory Plant. The bulk weight of the original material for ramming was about 1.4 g/cm 3. The ramming was done in a sectional mold.The influence on the properties of the blocks of the output of the sand slinger, the rate of movement of the sand-sllnger head relative to the surface being rammed, the distance from the sand-slinger head to the mold, and the moisture of the ramming compound were studied. The quality of the rammed blocks was evaluated on the basis of their surface hardness measured with a model 071 hardness tester, the open porosity, the apparent density, and the bend strength of samples sawed from blocks after firing at 800=C with a 2 h hold. The bend strength ~ was determined on an MII-100 tester on samples in the form of 40 • 40 • 160 nun beams.In conducting the investigations the technical parameters were varied within the following limits: sand-sllnger output, from 20 to 50 tons/h; rate of movement of the sand-slinger head, from 0.3 to 0.9 m/sac; distance from the sand-slinger head to the mold, from 1.5 to 4.5 m; and moisture of the compound, from 4 to 12%.It was established that the optimum moisture content of the quartz--clay compound was 8-10%.In ramming a compound with a moisture of 4-6% significant dust formation was observed, and after removal of the mold the angles of the blocks crumbled; their Obend did not exceed 0.03-0.05 MPa. With a compound moisture content of 12% the Sbend of the blocks was 0.1-0.2 MPa and during drying the blocks frequently cracked.An increase in the distance from the sand-sllnger head to the mold from 2.0 to 4.5 m has practically no detrimental influence on the properties of the blocks.This confirms the data of [2], in which it was shown that the rate of flight of the compound decreases by no more than 2% at a distance of 5 m from the sand-slinger head. With a distance from the sandslinger head to the mold of less than 1.5 m there is significant rebounding of the compound, as...
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