The refractories division of the Nizhni Tagil Metallurgical Combine (NTMC) has begun to produce forsterite brick. The dunite used for the brick is fired in a rotary kiln [1].Dunites are an ultrabasie mineral of magmatic origin. The chemical composition of the Nizhni Tagil dunites is as follows: 33.12% SiO2, 0.92% A1203, 6.36% Fe20~, 0.07% CaO, 41.71% MgO, calcination loss 16.1% [21 .The dunite is fired in the rotary kiln at 1500~ sintering is accompanied by complex physicochemieal processes so that the kiln lining is subjected not only to large thermal loads but at the same time also to the chemicomechanical action of the material being fired, the result being that the lining is rapidly eroded [3].The durability of the lining can be increased by means of a protective layer. Earlier experiments showed [4] that the formation of a protective layer on the refractory lining of the firing zone of a kiln depends on the physicochemical properties of the material being fired, on the refractory lining, etc. The protective layer is usually formed as a result either of a build-up of the fine, readily sintered fractions of the material being fired or of the presence of low-melting components in the material.No protective layer is formed spontaneously during the firing of dunite because in the process in a rotary kiln dunite is less prone to spontaneous dispersion than magnesite, for example. The grain-size distribution of dunite undergoes only marginal changes in the firing process. The fine dustlike fractions of dunite resulting from its dehydration and abrasion in the rotating kiln are carried away from the high-temperature zones to the less hot sections of the kiln where the temperature is not high enough for the fusion and adhesion of the particles r the lining. Furthermore, owing to its content of nondehydrated particles, the dunite dust is not highly active and not prone to sintering.The sintering of dunite proceeds mainly by virtue of the recrystallization of the minerals in the solid state with the participation of a small amount (12-15%) of a ferrous magnesia--silicate melt of a complex composition so that the material is not fused and is not deposited on the lining.The temperature of the kiln lining, more particularly in the sintering zone, undergoes cyclic changes because under the material being fired it is 150-200~ lower than in the direct interaction of the lining with the combustion products of the fuel. The frequent changes in the temperature produce stresses in the lining which give rise to spalling with the result that bricks drop out of the masonry.The durability of the lining is influenced, moreover, also by the stability of the thermal cycle of the kiln, the length of the flame, the draft, etc. The creation of a protective layer is a significant contributing factor in the durability of the lining. The layer must be dense, strong, and abrasion-resistant and it :must adhere firmly to the kiln lining. To this end, use was made of a composition which contained 20-25% chromite ore and fired dunite of a partic...
The stress -strain ~Eiaracteristics of MgO single crystals in compression are investigated in the temperatxre range from -196 "C to 2400 "C o n samples of the same shape and size. It is shown that the stress -strain curves may bc subdivided into three basic types, cach of them corresponding to the definite temperature range. The work hardening rate a t stage I is tempcrature independent and a t stage T I lineary decrcases with temperature increase in overall temperature range where work hardening is observed. The high temperat,urc maximum in the temperature dependence on the proportional limit is found which is not due to the effects of impurities. The cffect of geometrical form of spccimens on stress-strain parameters and the local true strain distribution i n compressed specimens have been studied.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.