JPS6327412B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a hearth roll for a continuous heat treatment furnace for metal strip, and in particular to a hearth roll that reduces the temperature difference in the axial direction and enables stable conveyance of the metal strip. It is.

[Conventional technology]

In general, continuous heat treatment furnaces for metal strips include:
A large number of hearth rolls are used for conveying metal strip. For example, in a vertical continuous annealing furnace as shown in FIG. roll 6
Due to the conveying action, the metal strip 1 moves in the direction of arrow A.
From then on, it passes through an annealing furnace in the direction of arrow B, and a predetermined heat treatment is performed during the passage.

In such a heat treatment furnace, the metal strip 1 may meander depending on its shape, tension balance, temperature conditions, etc.
When this meandering becomes large, a metal strip 1 is formed on the furnace wall.
The edges of the metal strip 1 may be rubbed, and the metal strip 1 may even break, resulting in serious damage. Further, when the metal strip 1 meanderes, the stress in the width direction becomes non-uniform and the metal strip 1 may buckle. Therefore, measures have been taken to prevent the metal strip 1 from meandering, such as installing an in-furnace steering device, improving the roll roughness, or improving the roll profile. In particular, the roll profile is closely linked to the meandering of the metal strip 1, and unless the roll crown has a sufficient centering effect, the center of the hearth roll 6 as shown by the arrow in FIG. The force directed toward the metal strip 1 loses its balance on the left and right sides, resulting in meandering.

In addition, if the crown amount of the hearth roll 6 is increased to prevent meandering, the centering force of the metal strip 1 will increase.
buckles in the width direction, causing a so-called heat buckle. Therefore, the ability to properly correct meandering and the ability to prevent the occurrence of heat buckles appear to be contradictory, but the reality is that in order to obtain a hearth roll 6 that has both of these abilities, the amount of crown is determined empirically. be.

On the other hand, inventions have been disclosed in which metal strips are conveyed in a stable state by controlling the crown amount of hearth rolls. For example, in JP-A No. 57-177930 and Utility Model Application No. 58-10546, the amount of crown is controlled by heating and cooling the hearth roll, and in Utility Model Application No. 55-172359, a bending device is installed to adjust the crown. It is proposed to do so.

[Problem that the invention seeks to solve]

However, since the thermal influence on the hearth roll is not constant in the heat treatment furnace, the crown of the roll is adversely affected. For example, in the heating zone and soaking zone, the temperature at the center of the hearth roll is lower than the temperature at both ends of the hearth roll. This is thought to be because the metal strip blocks the radiant heat from the furnace at the center of the roll, and at the same time, the metal strip removes heat from the roll. Then, the thermal crown reduces the initial crown of the hearth roll, weakening the centering effect of the roll. On the other hand, in the cooling zone, the opposite decrease will strengthen the centering effect.

As described above, since the roll crown changes depending on the degree of thermal influence, it is not possible to completely prevent meandering or heat buckling by taking measures only on the roll profile.

In addition, regarding methods for controlling roll crown, in order to apply these methods to actual operations, means for measuring and controlling the amount of crown must be provided for each roll, and many problems remain in terms of cost and other aspects. There is.

Furthermore, recently, soft materials and ultra-thin materials have become popular as metal strips.
If you were to transport this using a conventional hearth roll,
The above problems are further exacerbated.

This invention was made by focusing on the above-mentioned conventional problems, and provides a roll suitable for correcting the meandering and heat buckling of metal strips without causing heat buckles, which occur due to the influence of thermal crowns. The purpose is to obtain a hearth roll that can maintain the amount of crown.

[Means for solving problems]

The hearth roll of the present invention achieves the above object by enclosing molten metal in the internal space of the roll body.

(Function) As the molten metal moves inside the roll body due to the rotation of the hearth roll, this molten metal acts as a heat medium, making the temperature distribution in the axial direction of the hearth roll more uniform, thereby ensuring that the roll is properly adjusted. Maintain crown amount.

The molten metal is preferably a metal that is liquid during operation, such as tin (melting point 239.1°C, boiling point 2270°C),
Lead (melting point 327.4℃, boiling point 1737℃), bismuth (melting point
271℃, boiling point 1477℃), etc. are suitable.

If the initial crown of the hearth roll is appropriate, the temperature difference ΔT between the center of the roll and both ends of the roll is
As shown in Figure 7, it has been found that smooth operation can be achieved by keeping the temperature within ±30℃, and according to this invention, the temperature difference between the center and both ends of the hearth roll can be kept within this range. It is possible to store it.

It is not clear how the heat conduction is in the hearth roll of this invention, but for example, in the heating zone, heat flows in and out of the roll body as shown by the arrows in Figure 2, and the whole hearth roll is It can be assumed that the temperatures are balanced.
Note that since the molten metal inside moves violently due to the rotation of the hearth roll, the temperature distribution in the axial direction of the hearth roll becomes approximately uniform.

〔Example〕

Figures 1a and 1b show a hearth roll 6 according to an embodiment of the present invention.
consists of a roll body 6a and molten metal 7 sealed in its internal space 6b. Although tin is used as the molten metal 7, lead, bismuth, etc. can be widely used as long as it is a metal that is liquid during operation of the continuous heat treatment furnace.

FIG. 3 shows another embodiment, in which fins 8 are provided protruding from the internal space 6b of the roll body 6a, and are intended to promote the movement of the molten metal 7 when the hearth roll 6 rotates. It is. Since the fins 8 are for promoting the movement of the molten metal 7 as described above, their shape, position,
Conditions such as the posture, number, and dimensions are determined in accordance with conditions such as the dimensions of the hearth roll 6 and the amount and properties of the molten metal 7. Note that the inner surface of the roll body 6a may be coated with ceramics.

Further, although the molten metal 7 is sealed in a part of the internal space 6b in both of the above embodiments, it is also possible to fill the entire internal space 6b with the molten metal 7.

The inventors used the hearth roll 6 shown in FIG. 1 as the hearth roll 6 of the vertical continuous annealing furnace shown in FIG.
Annealing was performed using the heat pattern shown in the figure. The material of the roll body 6a of the hearth roll 6 is SCH22. In Figure 6, the solid line is metal strip 1.
The broken line shows the temperature inside the furnace. The reason why the temperature inside the furnace is stepped is that the vertical continuous annealing furnace has a heating zone, a soaking zone, a slow cooling zone, and a rapid cooling zone, which are arranged so that their temperatures decrease sequentially. The hearth roll 6 shown in FIG. 1 was used because
The hearth rolls used in the heating zone, soaking zone, and slow cooling zone are of the conventional type. In addition, the roll drive has a temperature of 300°C, which sufficiently melts tin.
The process was carried out at a furnace temperature of ℃ or higher to prevent roll eccentricity. Also, the line speed is 150m/
min (roll rotation speed approximately 1.1 times/sec).

FIG. 4 shows the temperature distribution of the hearth roll 6 in the heating zone, and FIG. 5 shows the temperature distribution of the hearth roll 6 in the slow cooling zone.
In both cases, the solid line represents the hearth roll 6 of this embodiment, and the broken line represents the conventional hearth roll temperature. The size of the metal strip when measuring the temperature distribution in Figure 4 was 0.9 mm x 934 mm, and the size of the metal strip when measuring the temperature distribution in Figure 5 was 1.15 mm x 934 mm.
It was 952mm.

In the case of this embodiment shown by solid lines in FIGS. 4 and 5, the temperature distribution in the axial direction of the hearth roll 6 was within ±30° C., and neither meandering nor buckling of the metal strip 1 occurred. I also tried increasing the line speed to 600m/min, but
Even at this speed, the temperature distribution, meandering, and buckling were the same as above.

In this example, the present invention was applied to the hearth roll of the vertical continuous annealing furnace shown in FIG. 9, but it can also be applied to an annealing furnace including an overaging treatment zone.
Of course, it can be used in all continuous heat treatment furnaces.

〔Effect of the invention〕

As explained above, according to the present invention, since the temperature distribution in the axial direction of the hearth roll can be made nearly uniform, deformation due to local expansion or contraction of the hearth roll can be suppressed, and the metal strip can be Meandering and heat buckling can be prevented. Therefore, stable operation is possible without reducing yield, and this has the effect of greatly contributing to improved productivity, quality, etc.

[Brief explanation of the drawing]

Fig. 1a is an axial cross-sectional view showing one embodiment of the present invention, Fig. 1b is a radial cross-sectional view of Fig. 1a, Fig. 2 is a schematic diagram of heat conduction to a hearth roll, and Fig. 3 is a diagram showing other examples. 4 and 5 are graphs showing the temperature distribution of the hearth roll, respectively.
The figure is a graph showing the relationship between the temperature inside the furnace and the temperature of the metal strip. Figure 7 is a graph showing the relationship between the temperature difference in the hearth roll, the meandering of the metal strip, and the occurrence of heat buckles. Figure 8 is the centering effect on the hearth roll. FIG. 9 is a schematic diagram of a typical vertical continuous annealing furnace. 1...Metal strip, 6...Hearth roll, 6a
... Roll body, 6b... Internal space, 7... Molten metal,
8... Huynh.

Claims (1)

[Claims] 1. A hearth roll for a continuous heat treatment furnace, characterized in that the internal space of the roll body is filled with molten metal.