Magnezit (Russia)

The working layer of a CBCM tundish lining provides unit operation for ten hours of metal pouring. Development stages are provided for second generation torcrete mix compositions of the trade mark Dalgun. Results are given for petrographic study of the working lining layer of periclase and periclase-forsterite compositions after service.

New developments are described from OOO Gruppa Magnezit and OAO Kombinat Magnezit concerning basic refractories, i.e. fluxes, starting mixes, hot repair mixes, backup materials, mortars, etc. A combined scheme for producing new forms of refractory materials, and also their physicochemical and operating properties are provided.

Experience of using OOO Gruppa Magnezit refractory materials in the lining of acid converters in Russia and the Ukraine is summarized briefly. Information is provided on the basis of results obtained in different metallurgical enterprises about the practice of using a set of measures promoting an increase in the operating life of converter linings.

Results are presented for a physicomechanical study of a refractory torcrete-mix grade PMT-86 produced by OOO Gruppa Magnezit. The wear intensity of a mix during operation in intermediate ladles is evaluated. Service properties are analyzed for torcrete-mix grade PMT-86 compared with imported analogs, and the high competitiveness of the mix and its attractive price and quality are demonstrated.

Specifics of the morphology, qualitative composition, and spatial extent of cryptocrystalline (pelitomorphic) magnesite deposits and manifestations confined in the weathering crust of ultrabasic rocks are described. It is noted that despite not very big resources, the magnesite material extracted from these deposits can be used for products with high technological properties that are in great demand. In this context, in prospecting minerals associated with ultrabasic rocks (chromites, nickel silicate), it seems expedient to pay special attention to the possibility of discovering industrial-scale deposits of magnesite in the weathering crust of these rocks, especially in vein rocks.

Physicomechanical properties of periclase-spinelid ceramics, in particular, the softening temperature under load and compressive strength, are shown to be controlled by the granular composition of the native ferriferous chrome spinelid. At relatively low concentration of CaO (0.51–0.88 wt.%), SiO2 (0.53–1.33 wt.%), and ratio CaO/SiO2 = 0.38–1.36, the incipient deformation temperature under load does not exceed 1700°C.

The sintering of a mixture of a caustic dust and an alumina dust collected from electric filters taken in MgO/Al2O3 ratios of 0.1, 0.28, 0.5, and 0.75 at 1650°C is studied. Materials with superior physicomechanical properties are obtained: open porosity, 1.2 – 8.4%; density, more than 3.5 g/cm3, and compressive strength, 160 – 410 MPa. High-density pellets (free of additions) are prepared at a MgO/Al2O3 ratio of 0.75, with compressive strength as high as 160 MPa.

Some special features of the mineral composition of magnesite from deep horizons of the Satkinskoe group of deposits is considered. Minerals that are paragenetically connected with magnesite and affect substantially the production process and quality of refractory products are described. It is established that the concentration of SiO2 in the magnesites increases regularly with increase in the depth of the horizon. Ways to solve the problem of fabricating quality magnesite for roasting are suggested.

Replacing fused periclase-chromite by sintered material in PShPKh batches did not adversely affect the level of their technical properties.