SU1254036A1 - Bath furnace for heating in salt solution - Google Patents

Description

The invention relates to the heating of metals in the molten salt and can be used in the processes of heat treatment, forging and soldering children, as well as on assessing the surfaces of parts with metals, such as boronization.

The aim of the invention is to improve the reliability of the furnace.

The drawing shows an induction furnace - a bath for molten salts, a longitudinal section.

The furnace includes a housing 1 connecting the lower asbestos-cement slab 2 with the upper (also asbestos-cement) slab 3. Inductor A is mounted inside housing 1 with a concentric inner lined crucible 5, to the upper part of which a graphite heater 6 is suspended shown). The latter is made in the form of an annular cylindrical spring with the closing of the first coil 7, the graphite heater is immersed in molten salt 8 with a gap relative to the side walls of the crucible 5. The crucible 5 is filled with barium salt 8.

Induction furnace works as follows.

From a machine generator or a static frequency converter (inverter), a voltage of 2.5 kHz is applied to inductor 4. The energy of the electromagnetic field is transmitted to a graphite heater 6. The magnetic flux inductor Op 4 closes on the first coil 7, which has a closed loop. The interatomic potential induced by the electromagnetic field in the heater 6 through the cold

molten salt B does not close. Coil 7 heats up and heats the surrounding layer of salt 8. Due to the fact that the axial gap between the butt end of the coil 7 and the surface of the melt mirror is smaller than the gap between the lateral generatrix of the coil 7 and the side walls of the crucible 5, it expands. The volume of salt 8, which occurs during melts, first of all pierces the surface of the mirror of the melt and does not damage the wall of the crucibles. The axial clearance is in the range of 5-10 mm. As the melt is heated to depth, the inter-turn potential between the closed first coil 7 and the second coil 9 closes through the greedy (heated) layer of the melt in the inter-turn

BOM gap. All the energy from coil 7 is transferred to the melt, coil 9 and coil 7 are closed with the melt, and part of the current begins to be shunted by the melt due to its electrical conductivity. The melting between the turns of the heater 6 is faster than in the known furnace, since in the latter the heat is heated only due to radiation and heat transfer from the graphite sectors (heater). Radiation-convective heat transfer is less intense than with the passage of electric current.

When the heater 6, made in the form of a spring, the interturn potential is closed through the molten salt 8 along a helical line, which has a greater length than the length of the contour of the graphite sector in the known device, therefore tegshovalii occurs in a larger volume and over the entire height of the heater 6. This equalizes the temperature over the entire height of the melt, when the intrinsic temperature of the heater 6 tends to equilibrium, i.e. to the temperature of the melt, since the current during its passage through the melt in the inter-turn gap reduces the thermal intensity of neighboring turns.

The execution of the graphite coil with the first closed turn provides the starting heating of the melt purposefully, i.e. from the mirror of the bath deep into it sequentially from turn to turn, which eliminates the likelihood of cracks in the crucible and increases its durability and, consequently, the reliability of the furnace. The heater 6 is fastened with ceramic elements, since graphite burns in contact with air, thus eliminating the need to dismantle the crucible due to the failure of the fastening elements of the heater sectors to the crucible and the latter to float.

Ceramic holders of the spring heater, in addition, keep the latter in the melt from ascending.

The main criteria for choosing the frequency of the current are the efficiency of operation and the minimum capital cost. An indicator of the efficiency of operation is the electrical efficiency of the inductor-heater system. KSH at age

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The frequency research institute decreases due to increased losses in the copper and the steel of the furnace. Therefore, it is necessary that the power in the heater is sufficient to maintain the desired melt temperature at the lowest possible current frequency and acceptable efficiency.

In the proposed device, this is achieved by the fact that the first closed coil has ohmic resistance, greater than that of the sector of the known device by a number of times equal to n - the number of sectors constituting in aggregate the same Section Ring, in which the ohmic resistance is determined by the area of the ring ( known device-sector) and determines the length of the current loop (the current is always laid but the outer generatrix). The length of the contour of the ring (first turn of the heater) is naturally longer than the length of the contour of one sector in the known device. The cross-sectional area determines the possible penetration depth of the current. Sound frequencies have a greater depth of penetration, the radio frequency. Therefore, the proposed device can operate at audio frequencies. This means that when using inductor power sources operating at sound frequencies, this furnace is

Compiled by N. Kuzovkina Editor L. Povhan Tehred A. Kravchuk Proofreader I. Erdeyi

Order 4689/30 Circulation 552Subscription

Blimini-I USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

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five

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more economically, the likelihood of failure due to a power supply failure (frequent replacement of expensive generator lamps) is reduced, which increases the reliability of the furnace as a whole. This reduces maintenance costs, simplifies management.

In addition, heat, which has been taken per unit length of the graphite heater to the melt, is transmitted through radiation and heat transfer (convection). In this case, the velocity of the melt circulation in height is determined mainly by the gravitational component (the difference between the weight of the hot and the cold melt in a constant volume). The circulation rate provides a certain temperature equalization over the height of the melt. With increasing melt circulation intensity (stirring), its temperature uniformity in height increases. In the proposed device, the heating is performed by closing the electric current through the melt, and its conductivity is ionic. Consequently, in the process of heating the melt with a current, the melt ions participate in the movement of the current, this sharply increases the circulation and the melt temperature is rapidly equalized when heated.

Claims (1)

FURNACE BATH FURNACE SALT MELT containing an inductor, a concentric lined crucible with salt melt placed in it and a graphite heater installed in the crucible, characterized in that, in order to increase the reliability of the furnace, the graphite heater is made in the form of a cylindrical spring with a closed first coil immersed in molten salt with a gap relative to the side walls of the crucible. S 7 s s ABOUT OE ‘o ί