RU2114186C1 - Bell-type furnace - Google Patents

Abstract

FIELD: devices for heat treatment of strips in coils. SUBSTANCE: furnace has heating hood, muffle, stand with fan, bottom plate, convection rings. Convection ring installed at coil bottom found at the half of stack is made with a definite ratio of total area of cross-section of channels to convection rings installed over height of coil stack. EFFECT: higher productivity of furnace, and increased quality of rolled products, and savings in energy carriers. 1 dwg , 1 tbl

Description

 The invention relates to a device for the heat treatment of strip products and strips in tightly-wound rolls and can be used in the metallurgical and engineering industries.

 Known bell furnace, including the cover of the foot of the rolls, which is a flat disk with a Central hole for the circulation of protective gas [1].

 The disadvantage of this analogue is low productivity, increased energy consumption and reduced quality of annealed metal due to the unevenness of the temperature field in the volume of the charge, associated with the irrational distribution of the heat flow under the furnace muffles.

 The closest analogue is a bell furnace containing a stand with a circulation fan, a muffle, a heating cap, a cover in the form of a flat disk, convector rings made identical with passage channels of variable cross section [1].

 A disadvantage of the known bell furnace is the low productivity and reduced quality of the annealed metal, which is caused by the heterogeneity of the temperature field over the volume of the charge due to the irrational distribution of the heat flow, since the upper part of the muffle does not participate in intensive heat transfer during periods of heating and cooling of the metal.

 The purpose of the invention is to increase the performance of the bell furnace, improving the quality of the annealed metal, saving energy.

 The proposed bell furnace solves the technical problem - it intensifies the heat transfer process during heating and cooling while increasing the uniformity of the mechanical properties of the annealed metal and saving energy.

 A positive result is achieved in that in a bell furnace containing a heating hood, a muffle, a stand with a circulation fan, a tray for the foot of the rolls, a cover of the foot in the form of a flat disk with evenly spaced support ribs forming passage channels of the cross-section, convector rings with passage rings located between the rolls channels of variable cross-section, tapering from the periphery to the center with a given total area of the average cross-sections of the channels, depending on the location of the rings in the foot of the rolls, convector The ring placed below the roll, installed at half the height of the foot, is made with a total area of the middle sections of the passage channels, comprising 1.3-2.2 and 2.1-3.5 of the total area of the middle sections of the passage channels individually of each of the other convector rings in the foot and foot cover rolls respectively.

.Let us denote the total area of the middle sections of the circulation channels of the convector ring, which is installed from the bottom of the roll at half the height of the foot, S _{Σ increased.} , for the remaining identical convection rings in the foot of the roll S _{Σ norms.} Then according to the invention

.

.Through S _{Σ roofs.} we denote the total area of the average cross sections of the passage channels of the cover of the foot of the rolls. Then according to the invention

.

замедляется прогрев второго и третьего рулона снизу стопы (5-я рулонная стопа), что приводит к ухудшению качества металла (большой разброс свойств), к повышенному расходу энергоносителя и снижению производительности колпаковой печи.With respect

the heating of the second and third rolls from the bottom of the foot is slowed down (5th roll foot), which leads to a deterioration in the quality of the metal (large variation in properties), to an increased energy consumption and a decrease in the performance of the bell furnace.

 When the value of the mentioned ratio is more than 2.2, the heating of the fourth and fifth rolls slows down, the unevenness of heating along the height of the foot increases, which leads to a large heterogeneity of the mechanical properties of the annealed metal; the achievement of the uniformity of properties specified by the standards leads to an increase in the duration of annealing, which entails a decrease in furnace productivity and an increase in energy consumption.

 The ratio of the total area of the middle sections of the circulation channels of the convector ring, installed below the roll, located at half the height of the foot, to the total area of the middle sections of the cover of the foot of the rolls is 2.1-3.5.

 With a ratio of less than 2.1, the flow of protective gas circulating under the muffle in the upper part of the cage is reduced, which slows down the heating and especially cooling of the entire cage, which reduces the productivity of the furnace and increases energy consumption.

происходит перераспределение потока защитного газа, большая его часть проходит через каналы крышки и осевую полость стопы рулонов, уменьшается поток защищенного газа, проходящий через конвекторные кольца, что замедляет нагрев и охлаждение, снижает производительность печи при одновременном увеличении неоднородности механических свойств отожженного металла.With respect

redistribution of the flow of protective gas occurs, most of it passes through the lid channels and the axial cavity of the foot of the rolls, the flow of protected gas passing through convector rings decreases, which slows down heating and cooling, reduces the productivity of the furnace while increasing the heterogeneity of the mechanical properties of the annealed metal.

In the manufacture of a bell furnace with a cover foot of rolls in the form of a flat disk and convector rings with the same total area of the average cross-sections of the circulation channels, regardless of the position of the convector ring in the foot, according to [2], selected as a prototype, and the test of such a furnace obtained the following results: the spread of the tensile strength of 190 N / mm ² along the height of the stack of rolls during annealing of 08ps steel to the “soft” state according to GOST 503-81; specific consumption of equivalent fuel 82 kg per 1 ton of annealed metal, the capacity of the bell furnace in the cycle of heating + cooling - 0.64 t / h.

 To substantiate the declared limits in achieving a positive result, experiments were conducted.

 In the bell furnace used the cover of the claimed design and the cover of the foot of the rolls, made according to the prototype. Annealed rolls weighing 10 tons, strip width 450 mm, the number of rolls in the foot - 5 pieces.

,
а отношение

.During the experiments, the uniformity of the temperature field of rolls of the 1st, 3rd and 5th, counting from the pallet, with the area of thermocouples laid in the channels drilled in the rolls (for details, see the example) was determined, furnace productivity and specific fuel consumption were determined . In addition, on the annealed metal, the spread of the tensile strength values along the stack height of coils of 08ps steel was determined, and the chemical composition was in accordance with GOST 1050-80. Altogether, 4 series of experiments A, B, C, and D were performed. In series A, the ratio

,
and attitude

.

значения отношения S_{Σ увел.}:S_{Σ норм.} составили соответственно 1,3; 2,2; 2,5.In experiments of series B, C, and D with the same range of ratios

the values of the relation S _{Σ increased.} : S _{Σ norm.} amounted to 1.3, respectively; 2.2; 2.5.

 All experimental data are tabulated.

As shown by the data of a pilot test, as a result of using the proposed bell-type furnace, the spread in the tensile strength of steel grade 08ps state “soft” according to GOST 503-81 is reduced by an average of 100 N / mm ² in comparison with the prototype; furnace productivity increases by 3-5%, fuel consumption - by 8-11%.

 The table shows the data of experiments performed to justify the selected parameters of the proposed bell furnace.

 The drawing shows a bell furnace.

 The proposed bell-type furnace comprises a stand 1, a pallet 2 for forming rolls 3 on it outside the limits of stand 1, a heating cap 4, a muffle 5, convector rings 6, 7, 8, 9, a cover 10 of the foot of the rolls; the total area of the middle sections of the passage channels of the convector ring 7 is 1.3-3.2 and 2.1-3.5 times larger than the total area of the average sections of the passage channels of the convector ring individually of each of the other convector rings 6, 8, 9 and the cover 10 of the foot of the rolls 3 respectively. The furnace is equipped with burners 11, a circulation fan 12.

 The inventive bell furnace operates as follows.

 On the stand 1, a pallet 2 is installed with the stack of rolls 3 formed on it, with convector rings 6, 7, 8, 9 between the rolls and the cover 10 on top of the foot. Then the stack of rolls is covered with a muffle 5 and a heating cap 4, with burners 11.

 In the process of heat treatment of the rolls 3, the shielding gas circulates under the muffle 5 using the stand fan 12. The protective gas, heating from the muffle 5, transfers heat to the rolls 3, passing through the channels of the cover 10 of the stack of rolls and through the channels of the convector rings 6, 7, 8, 9.

Claims (1)

 A bell furnace containing a heating cap, a muffle, a stand with a circulation fan, a tray for the foot of the rolls, a foot cover in the form of a flat disk with evenly spaced support ribs forming passage channels of cross section, convector rings placed between the rolls with passage channels of variable cross section, tapering from the periphery to the center with a given total area of the average cross-sections of the channels, depending on the location of the rings in the stack of rolls, characterized in that the convector ring placed below a roll installed at half the height of the foot is made with a total area of the average sections of the passage channels of 1.3 - 2.2 and 2.1 - 3.5 of the total area of the average sections of the passage channels individually of each of the other convector rings in the foot and cover foot rolls respectively.

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