Theory of heat treatment of resin-bonded refractories

Abstract

We studied the sublimation process of the volatile matter of a resin during the course of heating under laboratory conditions and its effect on the qualitative characteristics of the resin-bonded refractories. An uncompacted periciase--lime body mixed with the resin and cubic refractory specimens having an edge of I00 mm that were compacted at i00 N/mm ~ using the same body were studied. Their composition (wt. %) was as follows: magnesite powder (the minus 0.088 mm fraction 66%) 35, dolomite 60, pitch 5, and resin 6 (above 100%). The granulometric composition of the introduced dolomite was as follows: the minus i mm fraction 18.4%, 1-3 mm fraction 80.1%, and the plus 3 mm fraction 1.5%; the apparent density of the body and the specimens was i.72 and 2.91 g/cm ~, respectively; and the ultimate compressive strength of the specimens was found to be 3.72 N/mm 2.In order to prepare the specimens, we used coal tar supplied by the Donetsk KKhZ plant . It has a density of 1.246 g/cm ~ at 20~ a coking value of 50%, and a viscosity C~ = 81 sec.In the first series of experiments, a specimen and the uncompacted body were placed in a furnace and were held at 150~ they were weighed at intervals of i h. The weight loss (liberation of the volatile matter) was expressed as percentage of the weight of the resin. After a significant decrease in the rate of liberation of the volatile matter (after attaining virtually no change in the weight of the refractories), the specimen and the uncompacted body were held in the furnace at successively higher temperatures: 175, 200, 225, 250, 275, 300, 325, and 350~ Figure i shows the effect of the duration of holding of the refractories at a given temperature on the liberation (yield) of the fractions of the resin. An analysis of curves 1 and 2 indicates that at any given temperature, rapid liberation of certain fractions of the volatile matter of the resin occurs during the first 1-2 h of holding; from 2 up to 25 h (depending on the temperature), one observes a uniform decrease in the rate of liberation of the volatile matter followed by virtually complete cessation of this process. Mariupoi'sk institute of Metallurgy. Azovsta!' Complex.