JPH0514152U - Vertical induction heating furnace - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a vertical induction heating furnace which can improve heating efficiency and expel oxygen from the furnace in a short time. [Configuration] A plurality of inert gas blowing nozzles or holes 43
Are provided on the metal tube column 42 along the column longitudinal direction. At least the furnace wall portion 41 between the tip or hole 43 of the nozzle and the inner peripheral surface of the furnace wall is permeable to air, and the inert gas supply device 45 installed outside the furnace is connected to the metal tube support 42. The inert gas supplied to the metal tube column 42 flows through the metal tube column 42 and is heated until it flows into the furnace through the furnace wall 41. Therefore, it is possible to prevent the temperature of the atmosphere inside the furnace from lowering due to the inert gas injection. At this time, oxygen remaining in the furnace wall 41 also mixes with the inert gas, flows out into the furnace 14, and is discharged outside the furnace together with the inert gas.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a vertical induction heating furnace, and more particularly, to a furnace wall of the vertical induction heating furnace and a metal tube column supporting the furnace wall.

[0002]

[Prior Art]

 Among induction heating furnaces, there is a vertical induction heating furnace in which the furnace chamber opens downward and has a hearth that can be raised and lowered. In a vertical induction heating furnace, for example, the hearth supports the material side surface from below such that the plate surface of the plate-shaped material is in a vertical posture, and the hearth rises to load the material into the furnace. The material is heated with the plate surface vertical. Such a vertical 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. By creating a non-oxidizing atmosphere in the furnace, generation of molten scale can be prevented.

When heating in a non-oxidizing atmosphere as described above, an inert gas is blown into the furnace. Japanese Unexamined Patent Publication No. 1-136928 discloses a technique of introducing an inert gas into the hearth, preheating the inert gas, and then blowing the gas into the furnace.

Further, generally, the furnace wall is composed of a heat-resistant board, a fire-resistant brick and a heat-resistant fiber in order from the outside. It is necessary to support refractory bricks to prevent them from falling, and steel pipes or ceramic rods with cooling water inside are used as supporting materials. Japanese Utility Model Laid-Open No. 61-98850 proposes a furnace wall made of a ceramic fiber-based refractory material.

[0005]

[Problems to be solved by the device]

 In the method of introducing an inert gas into the hearth, the inert gas is preheated to prevent the temperature of the atmosphere in the furnace from lowering and the heating efficiency can be improved. However, it is impossible to expel oxygen remaining in the furnace wall out of the furnace.

On the other hand, in the steel pipe support that allows cooling water to pass through, the cooling water is discharged to the outside of the furnace together with the heat from the furnace body, so that the furnace wall temperature decreases and the heating efficiency decreases. Even if a ceramic rod is used, it is impossible to blow down the inert gas directly into the furnace to lower the temperature of the atmosphere inside the furnace due to the inert gas and to expel oxygen remaining in the furnace wall in a short time. Is.

Furthermore, a furnace wall made of a ceramic fiber-based refractory material requires a furnace shell or a supporting column for holding the refractory material. These furnace shells or supporting columns need to be cooled in order to maintain their heat resistant strength, resulting in a decrease in heating efficiency.

The present invention aims to provide a vertical induction heating furnace which can improve the heating efficiency and can expel oxygen from the inside of the furnace in a short time.

[0009]

[Means for Solving the Problems]

 The vertical induction heating furnace of the present invention is an induction heating furnace in which the furnace wall is supported by a plurality of metal tube supports, and a plurality of inert gas blowing nozzles or holes are provided in the metal tube supports along the longitudinal direction of the support. ing. At least the furnace wall portion between the tip or hole of the nozzle and the inner peripheral surface of the furnace wall is permeable, and an inert gas supply device installed outside the furnace is connected to the metal tube support.

The number of the inert gas blowing nozzles or holes depends on the length of the metal tube support and the pitch of the inert gas blowing nozzles or holes, and the pitch is, for example, about 200 to 400 mm. Stainless steel pipes and other alloy pipes are used as the metal pipes used for the columns. Ceramic fiber-based refractory materials (Kauwool and Unifert; both are trademarks) and spongy refractory materials are used as materials that make up the furnace wall with air permeability. Argon gas, nitrogen gas, or the like is used as the inert gas. In addition, the inert gas supply device includes a container filled with an inert gas under pressure, a supply pressure adjusting device, and the like.

[0011]

[Action]

 When the inert gas supplied to the metal tube column cools the metal tube column heated by the furnace wall when flowing through the metal tube column, the inert gas itself is heated. The metal tube columns maintain their heat resistant strength by cooling the inert gas. The inert gas blowing nozzle or the inert gas that has exited the hole is further heated while passing through the furnace wall and into the furnace, and is blown into the furnace. Since the inert gas blows into the furnace at a temperature almost equal to the atmospheric temperature in the furnace, it is possible to prevent a decrease in the atmospheric temperature in the furnace due to the blowing of the inert gas. At this time, oxygen remaining in the furnace wall also mixes with the inert gas and flows out into the furnace. Then, the inert gas blown into the furnace is accompanied by oxygen and flows out of the furnace through the discharge port provided at the top of the furnace.

[0012]

【Example】

 A vertical induction heating furnace for heating a grain-oriented electrical steel slab will be described as an embodiment of the present invention. FIG. 4 schematically shows a vertical induction heating furnace that heats a slab. As shown in the drawing, the furnace body 12 of the vertical induction heating furnace 11 is opened downward, and a heating coil 19 is attached to the outer periphery of the furnace wall 13. The vertical induction heating furnace 11 includes a slab turning device 26 that turns the slab 1 from the horizontal posture to the vertical posture by 90 degrees, and the hearth 31 and the hearth that support the slab 1 in the furnace in the vertical posture. An electric winch 33 for raising and lowering 31 is provided. The slab turning device 26 includes a pawl 27 on which the slab 1 is placed, an arm (not shown) connected to the pawl 27, and a hydraulic cylinder 28 that turns the pawl 27 by 90 degrees via the arm. Further, the vertical induction heating furnace 11 includes a support shaft 35 that holds the slab 1 by pressing it from above. The support shaft 35 is moved up and down by an air cylinder 36. Further, a roller table 37 is provided along the slab transportation line L.

FIG. 1 shows a vertical section of a vertical induction heating furnace 11, and FIG. 2 shows a horizontal section thereof. As shown in these figures, the furnace wall 13 is constructed of ceramic fiber walls 41. A column 42 is inserted in the furnace wall 13. In this example, the furnace length is 11 m, the furnace height is 3 m, and the furnace width is 370 mm. The column 21 is a stainless steel pipe having a nominal diameter of 1 inch. The pitch between the columns is 500 to 600 mm, and the number of columns is 20. The furnace bottom is kept airtight by a sand seal 17.

Each strut 42 is provided with three argon gas blowing nozzles 43 at the same height position. Then, a set of three argon gas blowing nozzles 43 is arranged at a pitch of 300 mm along the longitudinal direction of the column. The nozzle length is 30 mm and the nozzle diameter is 8 mm.

Argon gas cylinders 45 are connected to both ends of the column 42 via pipes 46, respectively. A flow rate control valve 46 is attached to the pipe 46. Argon gas blown out of the ceramic fiber wall 41 must not directly impinge on the surface of the slab 1 to generate convective heat removal from the slab surface. For this reason, the flow rate is adjusted by the flow rate control valve 46 so that the argon gas is blown out from the ceramic wall 41 at a low speed. In this example, the source pressure of the argon gas is 2 kgf / cm ² .

The argon gas supplied to the support columns 42 cools the support columns 42 heated by the furnace wall 13 when flowing through the support columns 42, and the inert gas itself is heated. The column 42 is cooled by the argon gas and maintains heat resistance strength. The argon gas blown out of the argon gas blowing nozzle 43 is further heated while passing through the ceramic fiber wall 41 to reach the inside of the furnace, and blows out into the inside of the furnace. Since the temperature of the argon gas becomes almost equal to the temperature of the atmosphere in the furnace and is blown out into the furnace 14, it is possible to prevent the temperature of the atmosphere in the furnace from lowering due to the blowing of the argon gas. At this time, oxygen remaining in the ceramic fiber wall 41 is also pushed out by the argon gas and flows out into the furnace 14. Further, the argon gas blown into the furnace 14 flows out of the furnace along with the oxygen in the furnace 14 through the discharge port 15 provided at the furnace top.

Here, an example in which the electromagnetic steel slab manufactured by the continuous casting method is heated by the vertical induction heating furnace configured as described above will be described. The slab was preheated by a gas combustion type heating furnace (not shown) to 1150 ° C. at a relatively low temperature rising rate. The dimensions of the slab are 11000 mm in length, 1000 mm in width and 200 mm in thickness. The slab was then rapidly heated to 1350 ° C. The supply amount of argon gas was 1000 to 1200 Nm ³ / hr. The argon gas was heated from room temperature to 400 to 500 ° C. before being supplied to the support and blown into the furnace. Table 1 shows the results of the heating time and the time when the oxygen concentration in the furnace reached 1000 ppm.

[0018]

[Table 1]

As is clear from Table 1, the heating time was shortened by 15% and the 1000 ppm arrival time was shortened by 70% as compared with the conventional method.

FIG. 3 shows another embodiment of the present invention.

The furnace wall 13 is composed of a heat-resistant board wall 51, a refractory brick wall 52, and a ceramic fiber wall 53 in order from the outside. The heat resistant board wall 51 and the fire resistant brick wall 52 strengthen the furnace wall 13. The stainless steel pipe support 55 is provided in the refractory brick wall 52. The argon gas blowing nozzle 56 is open toward the ceramic fiber wall 53 at a position where the refractory brick wall 52 and the ceramic fiber wall 53 are in contact with each other.

In the above-mentioned two embodiments, the argon gas blowing nozzles 43 and 56 both fulfill the function of supporting the furnace wall.

[0023]

[Effect of the device]

 In the vertical induction heating furnace of the present invention, the inert gas supplied to the metal tube support flows through the metal pipe support and is heated until it flows into the furnace through the furnace wall. Therefore, it is possible to prevent the temperature of the atmosphere in the furnace from lowering due to the inert gas injection. At this time, the oxygen remaining in the furnace wall also mixes with the inert gas and flows out. As a result, heating efficiency is improved and oxygen can be expelled from the furnace in a short time.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a part of a vertical induction heating furnace according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a part of the vertical induction heating furnace shown in FIG.

FIG. 3 is a cross-sectional view showing a part of a vertical induction heating furnace according to another embodiment of the present invention.

FIG. 4 is a perspective view schematically showing the outline of a vertical induction heating furnace to which the present invention is applied.

[Explanation of symbols]

1 Slab (Heating Material) 42 Struts 12 Furnace Body 43 Argon Gas Blowing Nozzle 13 Furnace Wall 45 Argon Gas Cylinder 14 Inside Furnace 51 Fireproof Board Wall 15 Discharge Port 52 Fireproof Brick Wall 19 Heating Coil 53 Ceramic Fiber Wall 31 Stand 55 Strut 41 Ceramic Fiber Wall 56 Argon gas blowing nozzle

Claims (1)

[Scope of utility model registration request] 1. An induction heating furnace in which a furnace wall is supported by a plurality of metal tube columns, wherein a plurality of inert gas blowing nozzles or holes are provided in the metal tube columns along the column longitudinal direction, and at least nozzles are provided. The furnace wall portion between the tip or hole of the furnace and the inner peripheral surface of the furnace wall has air permeability, and an inert gas supply device installed outside the furnace is connected to the metal pipe support. Shape induction heating furnace.