SU1133307A1 - Convector ring for heating charge in hood furnaces - Google Patents

Abstract

A CONVECTOR RING FOR HEATING THE GARDENS IN BULK OVENS, containing supporting discs with a central hole and radial circulation channels, and radial stiffeners between the discs, characterized in that the radial circulation channels in the discs are made in the form of diffusers in the direction from the periphery to the center, while the area of the channels in the horizontal section is 0.0250, 2 of the area of the supporting disc. po 00: o

Description

The invention relates to metallurgy, in particular, to sheet-rolling production, and improves the annealing process of cold-rolled strip steel. The known design of a convector ring, containing a zeitral disk with confused circulation channels, is formed by radial support ribs, on which the upper and lower support 1e are rigidly mounted with evenly spaced holes in their planar holes, sumarn area of 0.1 -0.15 from the whole area of the supporting disc. The annealing of coils in a bell-type furnace with such a design of a convector ring is particularly important as follows. At the stand, a stack of three to four rolls is formed, placing convector rings between them. A stop is muffled with a muffle, a cold purge of the muffle space is carried out with a protective gas, the circulation fan is turned on, and a heating cap is placed. In the process of heating, the circulating ventilator sucks the shielding gas from the inner cavity of the coil's foot and, under overpressure, supplies it through the exhaust slot into the annular gap between the muffle and the coil's foot. Moving through the annular gap, the protective gas heats up from the muffle, and when convector rings pass through the channels into the internal cavity of the foot, it transfers heat to the ends of the rolls. After the metal is heated to an annealing temperature, for example, 690–7 C, and the corresponding holding, the heating cap is removed and the process of cooling the rolls under the muffle is carried out. During the cooling process, the protective gas removes heat from the coils and transfers it to the muffle, and from it to the surrounding space LO. The disadvantages of annealing coils using this design of a convector ring are the low productivity of the annealing process and the unsatisfactory quality of the annealed sheet. The productivity of the annealing process is low due to the fact that the shielding gas transfers heat to the coils mainly through the supporting disks, i.e. through the screens. This type of heat transfer is inefficient. The presence of holes in the supporting discs with a diameter of the order of 50100 mm does not allow a significant improvement in heat transfer from the circulating protective gas to the ends of the coils. Gas does not radiate heat. And convection heat transfer is extremely low, since with a height of confused channels of the convector ring of about 50 mm and an angle of opening the protective gas jet 18-26, it practically does not wash the end surface of the roll above the hole. In addition, during annealing of rolls of tin with such a design of a convector ring, there is an unevenness of mechanical properties along the length of the strip, caused by overheating of the outer turns of the roll. The overheating of the coils is influenced by radiation directly from the muffle, heat transfer in the radial direction and the fact that the area of the living section of the ring is the same in terms of the thickness of the winding. Accordingly, the outer turns get beat-heat in the axial direction. Closest to the invention by technical essence is a convector ring for heating the set in bell-type furnaces, which contains supporting disks with a central hole, radial circulation channels and radial stiffening ribs between the disks .2. A disadvantage of the known convector ring is the considerable non-uniformity of the heating of the charge in the bell-type furnaces. This is due to the fact that the ends of the coils are washed by the circulating coolant, the passage through the radial channels in the disks, while the relative contact area of smoke and metal at the inner layers of the charge is insufficient to supply the additional heat necessary to compensate for the heat transfer to the metal by radiation from the muffle. The purpose of the invention is to increase the uniformity of heating. This goal is achieved by the fact that the convector ring for heating the charge in bell-type furnaces, containing supporting discs with a central hole and radial circulating channels, and radial stiffening ribs between the disks, the radial circulation channels in the disks are made in the form of diffusers in the direction from the periphery to the center, while the area of the channels in the horizontal section is 0.025-0.2 of the area of the supporting disk. The use of the convector ring of the proposed structure allows an increase in the intensity of the heat supply to the ends of the rolls located closer to the furnace axis. This makes it possible to heat the cac more evenly, i.e. more intensive heat supply to the inner ends of the coils compensates the heat transfer by radiation from the muffle to the outer layers of metal in the coils. FIG. 1 shows a convector ring, general view; in fig. 2, section A-A in FIG. 1. A convector ring consists of a central disk 1 with radial ribs 2 fixed on its surface of the supports, forming between them confused 3 and diffuse 4 channels. On the supporting radial ribs 2 rigidly installed the upper 5 and lower 6 supporting discs. Radial diffuser circulation channels 7 are made in supporting disks 5 and 6, which coincide in shape and location with diffuser channels 4. Moreover, the area of radial diffusion circulation channels 7 is 0.025-0.2 of the area of the supporting disk. Annealing of the coil foot in the coppack oven with the proposed design of the convector ring is carried out as follows. At the stand, a stack of three four rolls is formed; convector rings are installed between the rolls. The stack is covered with a muffle, cold purged, the circulation fan is turned on, and the heating cap is placed. In the process of heating, the circulating fan sucks in protective gas from the inside of the foot of the coils and, under overpressure, serves the annular gap between the muffle and the coil's foot. the cavity of the foot rolls and the suction of the fan. Circulating through confused channels 3, the protective gas transfers heat to the upper 5 and lower 6 support disks, from which heat is transferred by thermal conductivity to the ends of the rolls. The protective gas circulating through the di1) fusor channels 4 and the corresponding diffuser channels 7 directly transfers heat by convection to the ends of the coils. Part of the heat of the roll-. Our feet are transmitted by radiation from a muffle. After the stack of sheet metal is heated to an annealing temperature, for example 580-600 ° C, and an appropriate exposure is carried out, the heating cap is removed and the metal under the muffle is cooled to a temperature of, for example, 120-180 ° C. When cooled, the protective gas picks up heat both from the supporting discs and directly from the ends of the rolls and transfers it to the muffle. The area of the diffuser channels in the horizontal section is 0.025-0.2 of the area of the supporting disc. With an increase in the ratio of areas of more than 0.2, the coils of the charge coil are welded due to their wear as a result of high specific loads on the end of the coils. With a decrease in the area ratio of less than 0.025, the non-uniformity of temperatures along the radius of the charge rolls significantly increases, which leads to a deterioration in quality and a decrease in furnace productivity. The use of the convector ring of the proposed design in bell-type furnaces improves the uniformity of the heating of the charge, which improves the quality of heating of the metal and increases the productivity of the furnace.

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Claims (1)

CONVECTOR RING FOR HEATING A CARTRIDGE IN A CAPPER FURNACE, containing support disks with a central hole and radial circulation channels, and radial stiffeners between the disks, characterized in that, in order to increase the uniformity of heating, the radial circulation channels in the disks are made in the form of diffusers in the direction from the periphery to the center, while the area of the channels in the horizontal section is 0.0250.2 of the area of the support disk.