JPH064894B2 - Method for correcting meandering of steel strip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to continuous annealing of a steel strip and a metal strip, and when the steel strip meanders to the operating side and the driving side of a continuous annealing furnace, the roll width The present invention relates to a meandering straightening method for allowing a steel strip to pass straight through the center.

[Prior Art] In metal strips, particularly steel strips, it has become common to use continuous annealing for annealing after cold rolling.
The continuous annealing furnace is a huge line with an inlet and outlet facility and a furnace in the center, and is composed of many rolls.

In this line, the steel strip being annealed is on the operating side and the driving side (left and right).
If the steel strip slips (meanders), the stability of the strip is not only lost, but also the steel strip collides with the wall of the furnace and scratches the steel strip, or in severe cases, the steel strip breaks. This meandering occurs not only when there is a clear left-right asymmetrical cause in the width direction of the steel strip, such as a one-sided shape defect in the steel strip entering the continuous annealing furnace, but also a factor of asymmetrical left-right concealment to some extent. If the steel strip has a narrow width, when the steel strip is threaded, when the strip speed is increased, or when the strip tension is lowered,
This is likely to occur when the convex crown of the roll is made small.

It is a well-known fact that a convex crown roll having a bulge at the center of the width, which has a self-correcting effect of meandering, is used as a roll in the current continuous annealing line.

This utilizes the phenomenon that when the steel strip 1 is wound around a taper roll 2 as shown in Fig. 2, the plate climbs to the thick side of the roll, and the side with the larger roll diameter comes first. This phenomenon occurs because it tries to proceed.

In FIG. 2, γ is a taper angle, R is a roll radius, θ is a roll rotation angle, and Δу is a movement amount.

In the case of a convex roll, the taper rolls are approximately combined in the center of the width, so the plates at the ends of the plates on both sides try to move closer to the center of the width, and when they are pressed together, the equilibrium state is reached. Will keep. This pressing force, that is, the restoring force is considered to be proportional to the frictional force between the roll and the plate, that is, the friction coefficient and the surface pressure due to the tension. When meandering for some reason, the width of the left and right plates in the taper part changes.
Since the frictional force of the steel strips on the left and right taper portions is larger on the meandering side, a restoring force that returns to the original is generated. Therefore, if only a sufficiently large convex crown roll can be adopted, the meandering straightening device in the continuous annealing furnace becomes unnecessary.

However, in practice, when a large convex crown roll is used in a continuous annealing furnace, a squeezing flaw called a heat buckle occurs, so that the size of this convex crown is strictly limited. In a continuous annealing furnace that is practically used, the size of the convex crown is reduced to the limit where heat buckle does not occur, and the strong meandering prevention effect of the convex crown roll cannot be expected so much. For this reason, when the shape of the steel strip is disturbed, a left-right asymmetric force is generated, which causes an inconvenience that immediately leads to meandering.

Therefore, the continuous annealing furnace is provided with a mechanism for correcting the meandering so that the steel strip passes through the center on the inlet / outlet side of the furnace or inside the furnace. Currently, the meandering straightening device that is practically used is a roll tilting method that tilts the roll to the left or right, or back and forth, but for the reason to be described later, the meandering straightening device in the furnace is
Almost unusable.

The principle of meandering correction by roll tilting is that the winding direction of the steel strip disappears at a right angle to the roll rotation axis (the steel strip moving direction and the roll surface velocity direction are not parallel and has an angle), which is a winding effect. In other words, the effect of winding the steel strip while moving toward the direction where the angle between the steel strip and the rotation axis becomes smaller than the right angle is used.

Although the roll tilting method has a large meandering correction capability, the tension difference between the left and right of the steel strip becomes large during the meandering correction, and in extreme cases, either the left or right side will float up and only one side will come into contact with the roll. In a continuous annealing furnace where the steel strip is softened due to a high temperature, the steel strip is easily scratched and cannot be practically used in a high temperature furnace.

On the other hand, demands for softening, thinning, and widening are increasing as the materials and dimensions made by continuous annealing are diversified. In order to anneal such a material, from the viewpoint of preventing damage to the steel strip called heat buckle that occurs in a high-temperature furnace, a decrease in the convex roll crown, low strip tension, etc. are required,
It is becoming more and more easy to meander, and there is a need for a meandering prevention measure that can be used even in high-temperature furnaces.

[Problems to be solved by the invention]

The present invention has a high ability of a meandering straightening device for steel strips in a continuous annealing furnace, and is intended to straighten meandering by a method that does not cause flaws even when applied to a high temperature soft steel strip.

[Means for solving problems]

The present invention, in the continuous annealing furnace, a nozzle for blowing gas adjacent to the hearth roll is provided at both ends in the width direction of the steel strip, and at least from the nozzle on the side where the steel strip is close to the roll end,
The gist of a steel strip meandering method is characterized by straightening the meandering of the steel strip by blowing gas into the contact area between the steel strip and the roll so that the amount of gas blown in is larger than at the nozzle at the other end. To do.

In the present invention, unlike the meandering correction function by roll tilting,
The roll itself remains parallel, and the gas is blown with a distribution in the width direction between the roll and the steel strip (gas is blown on only one side of the steel strip, or when it is blown on both sides, the amount of gas blown left and right By changing), the contact state between the roll and the steel strip is made asymmetrical in the width direction, thereby correcting the meandering.

Most of the gas blown between the roll and the steel strip escapes from the steel strip end or the blown portion, and some gas is thought to escape from between the steel strip rolls to the roll exit side, Since the blowing of gas is asymmetric on the left and right, a force that moves the steel strip in the width direction is generated.

First, due to the reaction of the gas that escapes from the end of the steel strip, a force is generated that pushes the steel strip from the side where the gas is blown to the side where there is no blowing.

Next, due to the gas blowing pressure, the steel strip is lifted a little, so that the tension on the blowing side is increased, and a tension difference between the left and right sides is generated, which gives the steel strip a rotational moment. If the steel strip is lifted up by the blowing pressure, the position at which the roll and the steel strip start contacting can be changed left and right.

If a thin air film is formed between the roll and the steel strip, the friction coefficient between the steel strip and the roll may decrease. , The force that moves the steel strip may act on the person who blows the gas.

It is thought that there are forces other than these, but theoretically it is difficult to predict which force is large and in which direction the steel strip moves in the left and right directions. However, it is sufficient for the meandering correction device to utilize the asymmetry of the left and right sides, reproducibly and consistently moving the steel strip in the width direction. Therefore, the meandering correction ability of the present invention was investigated using the experimental apparatus shown in the examples.

It was confirmed that the result always moves to the opposite side to the gas blown regardless of whether the meandering correction part is driven by the roll, whether the roll is a convex crown, flat, or whether the gas pressure to blow is large or small. It was

That is, a gas drawing device is provided in the width direction of the steel strip, and when the steel strip meanders and deviates from the center line, gas is blown into the contact portion between the steel strip and the roll from the side closer to the roll end. Then, it is possible to correct the meandering and keep the steel strip at the width center.

This gas temperature is when the meandering correction is performed outside the furnace, and
Room temperature is acceptable where the steel strip can be cooled, but it is necessary not to disturb the temperature distribution of the steel strip in a high temperature furnace.
In addition, when correcting the meandering of the steel strip in the furnace, it is of course necessary to use a gas composition that does not oxidize, for example, an atmospheric gas (nitrogen gas, hydrogen gas, etc.). Gas such as exhaust gas may be used. Although a plurality of nozzles for blowing gas are provided, only one nozzle may be used as long as it is a slit-shaped nozzle or the like.

The amount of gas may be constant, but the amount of gas may be increased to quickly correct the meandering.

Example of Invention

In continuous annealing of a soft steel strip for processing having a thickness of 0.6 mm and a plate width of 1400 mm, a meandering correction in the soaking zone is performed by the method according to the present invention in a continuous annealing equipment having a hearth roll diameter of 800 mm and a roll body length of 2000 mm. did. (Fig. 1) The soothing hearth roll 6 is a cylindrical roll with a width of 600 mm at the center of the width.
It is a so-called convex crown roll which is a taper roll whose diameter is reduced by 0.5 mm between mm. All the rolls are driven, and the strip running speed is 120 m / min.

In the experiment, an industrial television (ITV) 9 capable of observing the position of the steel strip inside the furnace was used to detect meandering, and based on the meandering detection, the atmospheric gas 8 was blown. As the atmosphere gas 8, the furnace gas at the relevant location was used as it was, and it was considered that the temperature distribution of the steel strip would not be disturbed by the temperature drop.

The atmosphere gas nozzle 7 had a steel strip width of 1500 mm and was installed only at the end portions of 500 mm on both sides. Gas nozzle 7 is 1
A plurality of 3 mm holes were provided at intervals of 0 mm and the gas pressure was changed in the range of 0.1 to 1.5 atm so that the gas flow rate could be changed.

Experiment 1 (Fig. 3) shows the relationship between the meandering amount by ITV and the traveling amount of the steel strip. The meandering of the steel strip is 40 mm on the driving side.
At the place where it occurred (point A in Fig. 3), as a result of flowing the atmospheric gas from the meandering driving side to each nozzle at 40 / min, the meandering was corrected and the result returned to the original center line. Was given. Further, at point B in FIG. 3, when the gas flow rate per nozzle was set to 60 / min, the meandering correction was too tight, and the meandering to the operating side was made this time. At point C in FIG. 3, when the blowing of the atmospheric gas was stopped, the meandering to the drive side started at the same speed as the meandering when the experiment was started.

Experiment 2 (Fig. 4) is the result of flowing the atmospheric gas from point A in Fig. 4 with the gas pressure on the operating side set to 1.5 atm without the meandering. Was measured.

As shown in this example, it has indeed been shown that the method of the invention allows the meandering to be freely controlled.

In the present embodiment, the meandering is detected by ITV and the blowing of the atmospheric gas is manually changed, but it is easy to automatically detect and control this.

In this embodiment, the meandering correction function was carried out at a steel strip temperature of 750 ° C., but the steel strip could be freely moved to the left and right without the occurrence of flaws or heat buckles. With the conventional roll tilting method at 750 ° C., the meandering correction at the furnace entrance side is only possible because the flaws are present in the steel strip, so it is not possible to directly correct the meandering inside the furnace as in the present invention. Met.

〔The invention's effect〕

(1) Since the meandering can be freely controlled in a high temperature state in the continuous annealing furnace, the meandering is likely to occur in the furnace roll, but the flat roll is less likely to cause the heat buckle, and
Rolls with a small crown can be used. Therefore, the manufacturable range of the continuous annealing line can be expanded to a thin material, a wide width, and a soft side.

(2) Since the meandering correction according to the present invention is a method of blowing gas into the contact portion between the steel strip and the roll, the possibility of scratching the steel strip is low, and the conventional roll tilting method has a problem in high temperature. The meandering correction has become possible.

(3) Since only the gas nozzle is placed near the roll, and there is no moving part other than the pump for flowing the atmospheric gas, the reliability in the high temperature furnace is high.

(4) The response is quick because the control is performed by opening / closing the gas.

(5) In the present invention, the gas can be used only when the meandering correction is necessary. Therefore, the running cost can be reduced as compared with the method of passing the steel strip in front by the gas for the purpose of preventing roll flaws and heat buckle. Moreover, it is very advantageous. Further, the meandering correction mechanism is not required for all rolls, and has an advantage that the equipment cost can be reduced.

(6) The meandering correction according to the present invention is not limited to the continuous annealing furnace,
It can be applied to equipment that handles ordinary steel strips.

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of the present invention, and FIG. 2 is an experiment for determining the centripetal action of a steel strip by a taper roll. The rotation of the roll and the steel strip when the steel strip and the roll are prevented from slipping. Fig. 3 and Fig. 4 showing the relationship in which the sheet moves to the thick side of the roll are the results of the experiment for correcting the meandering, where the horizontal axis is the moving distance of the steel strip and the vertical axis is the amount of meandering of the steel strip. Are shown respectively. The symbols in the figure are: 1: Steel strip 2: Tapered roll, radius: R (mm) 6: Hearth roll 7: Nozzle for meandering correction 8: Atmosphere gas (equal to furnace temperature)

Claims (1)

[Claims] 1. In a continuous annealing furnace, nozzles for blowing gas adjacent to a hearth roll are provided at both ends in the width direction of the steel strip, and at least from the nozzle on the side where the steel strip is close to the roll end to the other end. Blow gas to the contact area between the steel strip and the roll so that the amount of gas blown is larger than that of
A method for straightening a meander of a steel strip, which comprises correcting the meander of a strip.