JPS6338409B2 - - 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 of the metal strip 1, the metal strip 1 passes through the annealing furnace in the direction from the arrow A to the arrow B, and is subjected to a predetermined heat treatment 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 a metal strip is conveyed in a fixed state by controlling the crown amount of a hearth roll. 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 centering effect is strengthened due to the opposite phenomenon.

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, crown amount measurement means and control means must be provided for each roll, which leaves many problems in terms of cost and other issues. 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 has been 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 powder and granules in the internal space of the roll body and stirring the powder and granules when the roll body rotates.

[Effect]

When the powder or granules move inside the roll body due to the rotation of the hearth roll, or by being forced to move, the powder becomes a heat medium and uniformizes the temperature distribution in the axial direction of the hearth roll. , thereby maintaining an appropriate amount of roll crown.

The powder is preferably a substance that is stable even during operation, such as A ₂ O ₃ , SiC, ZrO ₂ , SiO ₂ and the like.

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 6, it has been found that smooth operation can be achieved by keeping the temperature within ±30°C, 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.

〔Example〕

FIG. 1 shows a hearth roll according to an embodiment of the present invention, which consists of a roll body 6a and a powder 7 enclosed in its internal space. Here, the internal space of the roll main body 6a includes a space 8 having an I-shaped cross section, which is composed of a center hole 8a formed in the center of the roll and large diameter parts 8b and 8c communicating with both ends thereof, and a space 8 having an I-shaped cross section, and A circulation path is formed by a spiral space 9 that is provided nearby and communicates between the large diameter parts 8b and 8c, and in these spaces, powder and granular material (here, A
₂ O ₃ is used. ) is encapsulated in a flowable manner.

Therefore, as the hearth roll 6 rotates, A ₂ O ₃ becomes a heat medium and circulates within the roll body 6a along the spiral space 9 while being stirred.

FIG. 2 shows another embodiment of the present invention, in which a partition plate 6b is provided in the center of the roll body 6a, and two powder storage chambers 10 for storing powder and granule 7 are formed.
a, 10b, each powder storage chamber 10a, 1
A screw shaft 11 whose inclination is opposite in each chamber is disposed at the center position in the longitudinal direction of 0b. Here, the screw shaft 11 may be fixed to the roll body 6a, or may be rotated by a motor or the like in a direction opposite to the rotational direction of the hearth roll 6.

Also in this embodiment, by rotating the hearth roll 6, each powder storage chamber 10a, 10
The powder 7 in b becomes a heat medium and is forcibly flowed along the outer periphery of the roll body 6a while being stirred.

The inventors used the hearth roll 6 shown in FIG. 1 or 2 as the hearth roll 6 of the vertical continuous annealing furnace shown in FIG. Annealing was performed using the heat pattern shown. The material of the roll body 6a of the hearth roll 6 is
It is SCH22. In FIG. 5, the solid line shows the temperature of the metal strip 1, and the broken line shows the temperature inside the furnace. The temperature inside the furnace is graded in the heating zone, soaking zone, slow cooling zone, and rapid cooling zone of the vertical continuous annealing furnace.
This is because the arrangement is such that the temperature thereof decreases sequentially.

Further, the line speed was 400 m/min (roll rotation speed was approximately 3 times/sec).

FIG. 3 shows the temperature distribution of the hearth roll 6 in the heating zone, and FIG. 4 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 3 is 0.25mm x 934mm, and the size of the metal strip when measuring the temperature distribution in Figure 4 is 0.30mm x 934mm.
It was 952mm.

In the case of this embodiment shown by the solid line in FIGS. 3 and 4, 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. We also tried increasing the line speed to 600 m/min, but even at this speed, the temperature distribution, meandering, and buckling remained the same as above.

In addition, in this example, this invention is described in the eighth example.
Although the present invention is applied to the hearth roll of the vertical continuous annealing furnace shown in the figure, it can of course be applied to annealing furnaces including an overaging treatment zone, as well as to continuous heat treatment furnaces in general.

〔Effect of the invention〕

As explained above, according to the present invention, the temperature distribution in the axial direction of the hearth roll can be made nearly uniform, thereby suppressing the deformation of the hearth roll due to local expansion or contraction, and 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]

1 and 2 are axial cross-sectional views showing an embodiment of the present invention, FIGS. 3 and 4 are graphs showing the temperature distribution of the hearth roll, and FIG. 5 is a graph showing the temperature distribution in the furnace and the metal strip. Figure 6 is a graph showing the relationship between the temperature difference in the hearth roll, the meandering of the metal strip, and the generation of heat buckles. Figure 7 is an explanatory diagram of the centering effect in the hearth roll. Figure 8 is It is a schematic diagram of a typical vertical continuous annealing furnace. 1...Metal strip, 6...Hearth roll, 6a
...roll body, 7...powder, 8, 9...internal space,
10a, 10b...powder storage chamber, 11...screw shaft.

Claims (1)

[Claims] 1. A hearth roll for a continuous heat treatment furnace, characterized in that a particulate material is enclosed in an internal space of a roll main body, and the particulate material is stirred when the roll main body is rotated.