JPS6250418A - Continuous electrical heating method for belt-like metal - Google Patents

Abstract

PURPOSE:To prevent the generation of flaws of a belt-like metal by providing a casing to enclose the bottom surface of a roll for conveying the belt-like metal in the lower stage in a furnace, forming a fluid layer of conductive grains in the casing and feeding electric power to the belt-like metal from an external power source via said layer to heat the belt-like metal. CONSTITUTION:The casing 6 to enclose the lower half surface of the roll 3 for conveying the belt-like metal S in the lower stage in the furnace is provided and an air permeable electrode 7 is provided to the inside surface thereof. The conductive grains 8 are packed into the casing 6 up to the position slightly higher than the lowermost surface of the roll 3. An inert gas is introduced from a gas blowing pipe 9 in the bottom of the casing 6 through a perforated supporting plate 10, a gas distributing plate 11 and the electrode 7 into the casing 6 to fluidize the particles 8. The electricity is fed through the particles 8 to the metal S when the electric power is fed from a feeder 12 to the electrode 7. The belt-like metal is thus heated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for heating a strip metal in a furnace for continuous heat treatment, and more particularly to a method for supplying power to a metal strip.

(Prior Art) Conventionally, heating methods for cold-rolled steel sheets in a continuous annealing furnace include a direct flame type non-oxidation heating method, a radiant tube heating method, and a radiant tube heating method.
Indirect electric heating methods are used, but since each of these methods uses heat transfer, the heating capacity per unit time is not very high, and in order to secure the required total amount of heat, the heating time is Therefore, the length of the heating zone will inevitably become longer. Also, from the viewpoint of maintaining a protective atmosphere in the heating zone, it is not possible to use high-temperature direct combustion gas.
Furthermore, the temperature of the resistance heating element for electrical heating cannot be raised to a very high temperature, so the heating capacity is restricted and the overall equipment tends to be long.

In contrast to such a heating method using heat transfer, a method has been proposed in recent years in which a metal strip in a furnace is heated by directly applying electricity to it. For example, as disclosed in Japanese Patent Publication No. 60-26818, there is a method in which electrode rolls are provided at the beginning and end of the furnace, and electricity is supplied from the electrode rolls to the cold rolled steel sheet to heat it.

(Problems to be Solved by the Invention) However, the conventional method of supplying power to a metal strip using such an electrode roll has the following problems in practical use. In other words, metal strips, such as cold-rolled steel plates, have a wide plate width, and the flatness in the width direction is not necessarily perfect.
The surface of the electrode roll and the surface of the plate may partially separate during sheet passing, and at this time an arc is generated, causing flaws on both the electrode roll and the plate, deteriorating the quality of the plate surface. let

Further, dust adhering to the electrode roll also tends to cause arcing.

An object of the present invention is to provide a novel power supply method that can solve the problems caused by the power supply method using electrode rolls as described above.

(Means for Solving the Problems) The method of the present invention for this purpose is a method of heating a strip metal with electricity in a continuous heat treatment furnace. set up,
A continuous current heating method for a metal strip, characterized in that a fluidized bed of conductive particles is formed in the casing, and the metal strip is heated by being supplied with electricity from an external power source through the conductive particles in the casing. This is a summary.

(Embodiments and Effects) The present invention will be described in detail below based on illustrated embodiments.

Figures 1 to 4 are diagrams showing the configuration of an apparatus in an embodiment of the present invention. Figure 1 is a diagram showing the arrangement of the electrode part on the conveyor roll in the furnace, and Figure 2 is a diagram showing the arrangement of the electrode part in the in-furnace conveyor roll. FIG. 3 is a cross-sectional view taken along the line A-A in FIG. 2, and FIG. 4 is a cross-sectional view showing another example of the structure of the electrode section.

In Fig. 1, a portion 1 surrounded by a dashed-dotted line indicates the inside of the furnace (in this example, the heating zone of the continuous annealing furnace), and a strip metal (in this example, a cold-rolled steel plate, hereinafter referred to as strip) S represents the drawing. Enter furnace 1 from the right side, exit from the left side, and enter the next furnace (soaking area). In the furnace 1, conveyor rolls are installed in two stages, upper and lower, and in this embodiment, electricity is applied to the strip area between the rolls 3-1 and 3-3 to heat it.

Therefore, in this embodiment, the lower roll 3-1.3-2°3
-3 respectively arrange electrode parts 5-1.5-2.5-3, upper roll 2-1.2-2 and lower roll 3-
2 is insulated to ground, and connected from the power source 4 to the electrode section 5-2.
〇 Electrode portion (5-1
~5-3) comprises a casing surrounding the lower surface of the rolls (3-1 to 3-3), conductive particles in the casing, a means for blowing gas into the casing to fluidize the conductive particles, and It consists of an electrode that supplies electricity to the conductive particles, and its specific configuration is shown in FIG.

In the figure, reference numeral 6 denotes a semi-cylindrical casing with ends that surrounds the lower surface of the roll 3. A breathable electrode (for example, copper wire formed in a mesh or lattice shape) 7 is provided on the inner surface, and a conductive electrode is provided inside the casing. Particles (for example, particle size 0.2-1.
Copper, niobium, zirconium boride, titanium boride, etc.) 8 are packed to a height somewhat higher than the bottom surface of the roll 3.

It is desirable that the casing 6 be provided with ground insulation, and if no ground insulation is provided, an insulator is interposed between the casing 6, the breathable electrode 7, and the conductive particles 8. The breathable electrode 7 is supplied with power from a power source (indicated by 4 in FIG. 1) through a power supply line 12.

The purpose of fluidizing the conductive particles 8 is to uniformly contact the conductive particles 8, which are not completely flat, to keep the power supply ability constant and prevent arcing, and to keep the conductive particles 8 uniformly in contact with the strips, fS, and to prevent arcing.
This is to prevent the occurrence of scratches, etc. The degree of fluidization is within the range of so-called initial fluidization, in which the particles are still in contact with each other. As a means for forming a fluidized bed of conductive particles 8, a gas blowing pipe 9 is provided at the bottom of the casing 6, and a gas (for example, an inert gas such as argon) that does not adversely affect the atmosphere in the furnace is injected from the gas blowing pipe 9. is gently blown into the casing 6 through the perforated electrode 70 from the porous gas distribution plate 11 supported by the perforated support plate 10 to form a fluidized bed of the conductive particles 8 inside the casing 6. . Note that the perforated support plate 10 may be provided if the gas distribution plate 110 has sufficient strength.

Next, the structure of the longitudinal end of the roll body of the casing 6 is
This will be explained with reference to FIG. Generally, in the range near the exit side of the heating zone, the shape of the IJ knob tends to be elongated in the middle, and the ears are slightly stretched.

Since the lugs easily conform to the roll surface, the end of the casing 6 should cover the lower end of the roll 3, as shown in FIG. The neck of the roll 3 is structured to be in sliding contact with the sealing device (for example, a burnable soft linear bundle of carbon fiber, copper wire, etc.) 13.
This prevents the conductive particles 8 from jumping into the roll bearing portion (not shown). In the configuration shown in FIG.

Even if the push S meanders or the degree of the elongated shape changes,
The fluidized conductive particles 8 fill the space between the breathable electrode 7 and the strip S to maintain a conductive state, and the ears of the strips and strips S are in close contact with the a-ru 3, so the strip S
The conductive particles 8 do not enter between the roll 3 and the roll 3, and no streaks or surface defects occur.

On the other hand, since the shape of the strip tends to have an ear wave shape in the range close to the inlet side of the heating zone, the casing structure is such that the width of the casing 6 is made smaller than the width of the strip f8, and the width of the strip 7'S is as shown in FIG. The structure is such that it slides into contact with the surface via a sealing tool 13.

In the configuration shown in FIG. 4, even if the edge of the strip S is separated from the roll 3, the conductive particles 8 will not enter between the roll 3 and the strip S.

(Effects of the Invention) According to the power supply method according to the present invention described above, it is possible to uniformly and stably supply power over a relatively wide area to the strip metal in the furnace. The amount of current per area, that is, the total amount of current that can be passed through the metal strip without making the current density very high, becomes larger, the required length of the heating zone for the required temperature increase can be shortened, and the electrode There is an excellent effect that arc flaws do not occur between the band-shaped metal and the occurrence of flaws in the band-shaped metal.

[Brief explanation of the drawing]

1 to 4 are diagrams showing the configuration of an apparatus in an embodiment of the present invention. FIG. 1 is a diagram showing the arrangement of the electrode section on the in-furnace conveyance roll, and FIG. 2 is a diagram showing the electrode section of FIG. 1. A sectional view showing the configuration of
FIG. 3 is a sectional view taken along the line AA in FIG. 2, and FIG. 4 is a sectional view showing another example of the structure of the electrode section. 1...Furnace interior, 2-1.2-2...Upper roll, 3
, 3-1 to 3-3...lower roll, 4...power supply, 5
-1 to 5-3... Electrode part, 6... Casing, 7.
... Breathable electrode, 8... Conductive particles, 9... Gas blowing pipe, 1o... Perforated support plate, 11... Gas distribution plate,
12... Power supply line, 13... Seal tool, S... Strip.

Claims (1)

[Claims] In a method of electrically heating a strip metal in the furnace of a continuous heat treatment furnace, a casing is installed that surrounds part or all of the lower surface of the lower conveyor roll in the furnace, and a fluidized bed of conductive particles is formed within the casing. A continuous current heating method for a metal band, characterized in that the metal band is heated by supplying power from an external power source through the conductive particles in the casing.