JP2500730Y2 - Induction heating furnace seal device - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing device for an induction heating furnace, and more particularly to a sealing device between the bottom of the furnace body and the hearth.

[0002]

2. Description of the Related Art Among induction heating furnaces, there is an induction heating furnace in which a furnace chamber is opened downward and which has a hearth that can be moved up and down.
In this type of induction heating furnace, for example, the furnace floor supports the material side surface from below so that the plate surface of the plate-shaped material is in a vertical posture, and the furnace floor rises to load the material into the furnace. The material is heated in a posture where the plate surface is vertical. Such an induction heating furnace is used, for example, to heat a grain-oriented electrical steel slab to a high temperature of 1200 ° C. or higher in a non-oxidizing atmosphere. The oxidizing atmosphere is used in the furnace because the slab surface is oxidized and the oxide scale is melted at a high temperature of 1250 ° C. or higher. The molten scale damages the furnace body and the hearth, and causes surface damage of the product and damage to the rolling roll during hot rolling. The induction heating furnace is equipped with a sealing device to maintain the inside of the furnace in a non-oxidizing atmosphere. Conventionally, a sand seal device has been widely used as a seal device. (See, for example, Japanese Utility Model Laid-Open No. 1-129248).

[0003]

The above-mentioned sand seal device has the following problems. That is, the molten oxide scale and dust dropped from the heating material adhere to the sand portion to solidify the sand. Also, the knife edge is exposed to high temperatures and deforms during handling of the heated material. For these reasons, the sealing performance is lost and the atmosphere enters the furnace through the sealing portion. Further, since the sand seal portion is provided, it is difficult to clean the hearth and maintenance work of the hearth is difficult.

This invention intends to provide a sealing device for an induction heating furnace which has excellent sealing performance and facilitates hearth maintenance.

[0005]

A sealing device for an induction heating furnace according to the present invention comprises a furnace body bottom portion and a hearth floor of an induction heating furnace having a furnace chamber that opens downward and has a vertically movable furnace floor. In the sealing device that maintains the airtightness between the gaskets, the gasket is provided at the bottom of the furnace body along the entire circumference of the furnace chamber, and extends all the way around the outer circumference of the hearth bottom wall, and the tip projects toward the gasket. A knife edge, a flexible sealing plate that extends over the entire circumference along the inner peripheral surface of the furnace bottom, is fixed at a position below the gasket at the bottom of the furnace body, and adheres closely to the outer peripheral surface of the knife edge, and of the furnace bottom. A device for supplying an inert gas is provided between the inner peripheral surface and the seal plate.

The gasket is made of fibrous heat resistant elastic material such as kao wool and asbestos. The knife edge and seal plate are made of metal plate such as stainless steel. Nitrogen gas is suitable as the inert gas, and is supplied from a cylinder or the like that is stored under pressure.

[0007]

When the hearth on which the heating material is placed rises to the material heating position and is stopped, the tip of the knife edge lightly contacts the gasket to keep the furnace airtight. Further, the sealing plate is brought into close contact with the outer peripheral surface of the knife edge to form a closed space surrounded by the inner peripheral surface of the furnace bottom, the gasket surface and the sealing plate. The sealed space is shielded from the outside air by a seal plate. Inert gas above atmospheric pressure is supplied to the closed space to prevent atmospheric air from entering the furnace.

[0008]

EXAMPLE An example will be described by taking a sealing device for an induction heating furnace for a grain-oriented electrical steel slab as an example. The induction heating furnace is provided adjacent to the hot rolling line, and heats the slab preheated in the gas combustion type heating furnace to a high temperature. The high temperature heated slab is subsequently rough-rolled and finish-rolled.

FIG. 1 is a schematic vertical sectional view of an induction heating furnace of the present invention. As shown in the drawing, the furnace body 2 of the induction heating furnace 1 has a box shape and opens downward. Side wall 3
A heating coil 9 is provided on the outside of the. Also, the furnace body 2
A hearth 11 is arranged below the. The hearth 11 has a support 13 made of heat-resistant alloy steel attached to the top of a hearth body 12 made of a refractory (castable). The lower part of the hearth is a hearth bottom wall that projects outward from the hearth body. The hearth 11 is moved up and down by a lifting drive device (electric winch; not shown). The hearth 11 supports the side surface of the slab from below so that the upper and lower surfaces of the slab are in a vertical posture, and charges the slab S into the furnace through the opening 8. Airtightness is maintained between the furnace bottom 5 and the hearth 11 by the sealing device 21.

FIG. 2 shows details of the sealing device 21 between the bottom 5 of the furnace body and the hearth 11. A gasket holder 22 is attached to the bottom 5 of the furnace along the inner circumference of the furnace chamber 7 over the entire circumference. The gasket holder 22 includes a gasket groove 23 that opens downward. A gasket 24 made of kaool is inserted in the gasket groove 23. The hearth bottom wall 14 is provided with a knife edge 26 that extends around the entire circumference along the outer circumference. The knife edge 26 is made of a stainless steel plate and has a tip protruding toward the gasket 24. A dust collecting groove 28 is formed on the hearth bottom wall 14 between the hearth body 12 and the knife edge 26.

A seal plate 31 made of stainless steel is fixed to a portion extending downward of the gasket holder 22 with a bolt 31. The seal plate 31 is slightly curved toward the inner peripheral surface of the furnace chamber 7 and extends along the entire inner peripheral surface of the furnace bottom 5 along the entire circumference.

Nitrogen gas supply pipe 3 opening to the enclosed space 34
6 is provided on the bottom 5 of the furnace body. Nitrogen gas supply pipe 3
A nitrogen gas cylinder 37 is connected to 6 via a pressure control valve 38. The nitrogen gas cylinder 37 stores pressurized nitrogen gas.

The electromagnetic steel slab S is preheated in a gas combustion type heating furnace and then transferred from the hot rolling line to the furnace floor by a transfer device. Then, the hydraulic cylinder is driven to raise the hearth 11 to the slab heating position. The slab S is heated to a high temperature while the hearth 11 is stopped at the slab heating position.

In the sealing device 21 constructed as described above, when the hearth 11 rises to near the slab heating position, the sealing plate 31 slides on the outer peripheral surface of the knife edge 26 and comes into close contact therewith. As a result, a closed space 34 surrounded by the inner peripheral surface of the furnace body bottom portion 5, the gasket 24 surface and the seal plate 31 is formed. The sealed space 34 is shielded from the outside air by the seal plate 31. When the hearth 11 rises to the slab heating position, the tip of the knife edge 26 is brought into light contact with the gasket 24 to keep the furnace chamber 7 airtight. Further, nitrogen gas is supplied from the nitrogen gas supply pipe 36 into the closed space 34. The pressure of nitrogen gas in the closed space 34 is 0.1 kgf /
It is about cm ² , which prevents the atmosphere from entering the furnace. Molten oxide scale and dust from the slab fall into the dust reservoir groove 28 and are deposited there. Therefore, even if the molten oxide scale or the like falls, the airtight performance is not impaired unlike the sand seal device.

Here, a specific example of actually heating the slab will be described. The electromagnetic steel slab was preheated by a gas combustion type heating furnace to 1150 ° C. at a relatively low heating rate.
The preheated slab was roughly rolled and then charged into an induction heating furnace. Then, after purging the air in the furnace with nitrogen gas, the slab was rapidly heated to 1350 ° C. At this time, the oxygen concentration in the furnace was 100 ppm or less. On the other hand, in an induction heating furnace equipped with a sand seal device,
The oxygen concentration reached a maximum of 1000 ppm.

[0016]

Since the gasket is provided on the furnace body and the knife edge is provided on the bottom wall of the hearth, the sealing performance is not impaired by the molten oxide scale and dust. Further, since the inert gas at atmospheric pressure or higher is supplied to the closed space formed by the inner peripheral surface of the bottom of the furnace body, the gasket surface and the seal plate, the invasion of the atmosphere into the furnace can be prevented. Therefore, the sealing device of the present invention exhibits excellent sealing performance. Further, since there is no sand part on the bottom wall of the hearth, hearth maintenance is easy.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an example of an induction heating furnace provided with a sealing device of the present invention.

FIG. 2 is a vertical cross-sectional view showing a part of a sealing device according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Induction heating furnace 21 Sealing device 2 Furnace body 22 Gasket holder 3 Furnace side wall 24 Gasket 5 Furnace body bottom 26 Knife edge 7 Furnace chamber 28 Dust collecting groove 9 Heating coil 31 Seal plate 11 Furnace 34 Closed space 12 Furnace body 36 Nitrogen Gas supply pipe 13 Supporting hardware 37 Nitrogen gas cylinder 14 Hearth bottom wall S slab

Claims (1)

(57) [Scope of utility model registration request] 1. A sealing device for maintaining an airtightness between a bottom of a furnace body and a hearth of an induction heating furnace having a hearth which can be moved up and down, the furnace room being opened downward. Along the entire circumference of the bottom of the furnace body, around the outer circumference of the hearth bottom wall, the knife edge with the tip protruding toward the gasket, and the entire circumference of the bottom of the furnace body And a flexible seal plate that is fixed at a position below the gasket at the bottom of the furnace body and that adheres closely to the outer peripheral surface of the knife edge, and an inert gas is supplied between the inner peripheral surface of the bottom of the furnace body and the seal plate. And a device for controlling the induction heating furnace.