One of the main factors determining the service conditions of vacuum induction furnaces is the temperature conditions.The temperature distribution in crucible walls was studied in the 1.0 and 2.5-ton vacuum induction furnaces of "Elektrostal'" Plant. The furnace crucibles were prepared by the method layer-by-layer ramming with granular highly refractory materials consisting of fused periclase and corundum with the use of a metal template. The thickness of the water-cooled inductor coating was 5-10 mm. The temperature of the water leaving the inductor winding was 25-40~For the purpose of sintering and the formation of a sufficiently strong and metal resistant layer on the working surface of the crucible, cast iron was first melted at atmospheric pressure.The molten iron was heated to 1620-1640~ held for 30 min, and then poured at 1300-1400~The length of the cast iron heat was from 16 to 19 h. Then a wash heat of Armco iron was melted at 1600-1620~All subsequent heats were melted in vacuum (1.33-13.3 cPa). In the campaigns studied nickel base alloys were melted at 1520-1540~To determine the temperature conditions of the lining Chromel--Alumel (KhA) and PtRh--Pt (PP-I) thermocouples were placed at three levels in the height of the crucibles. The thermocouple junctions were passed through holes in the paronite packings between the inductor turns and the free ends passed from the furnace chambers outward through seals. The temperature was recorded with an ~PP-O9M3 electronic potentiometer with a short shut-down of the inductor. The method of placing the thermocouples in the vacuum induction furnace wall lining is shown in Fig. I.Data on the temperature distribution in the walls of a 1.0 ton furnace crucible during 16 heats and in the walls of a 2.5 ton furnace crucible during i0 heats is shown in Figs. 2 and 3. From Figs. 2 and 3 it follows that during the period of steady lining thermal conditions starting with the fourth heat the maximum and minimum temperatures stabilize and are repeated each heat.The temperature in the region of the 1.0 ton furnace crucible inductor coating is 265~ at the banks and 740~ at a distance of 350 mm from the bottom. For the 2.5 ton furnace these temperatures reach 250~ at banks and 360~ at a distance of 510 mm from the bottom.In all cases the rate of temperature change is less than l~The temperature in the center portion across the thickness of the 1.0 ton furnace crucible reaches II00~ at the banks and I120~ at a distance of 580 mm from the bottom. For the 2.5 ton furnace these temperatures are 950~ at the banks, 810~ at a distance of 510 mm, and 800~ in the upper portion of the crucible.The rate of temperature change is 3-4~At a distance of 20 mm from the working surface the maximum lining temperature at the banks is 1200~in the upper portion of the crucible 1400~ and the rate of temperature change is 9-11~The temperature gradient in this area is from 12 to 17~ for the 1.0 ton furnace and from 9 to 12~ for the 2.5 ton furnace.The high temperature gradient, shrinkage phenomena, and pro...
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