JP2001137930A - Manufacture of steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a trouble-free and stable manufacturing method of a steel strip by preventing both of generation of the reduction of area and roll marks in a skin pass mill which are problems when a weld point passes through and generation of roll marks when the weld point passes through leveler rolls. SOLUTION: While the weld point of the steel strip 1 passes through the skin pass mill 5 and a tension leveler 8, a stage where skin pass rolling is executed by constant tension control is provided. In this stage, while the weld point of the steel strip passes through at least the skin pass mill, the rolling force of the skin pass mill is reduced lower than the rolling force in the normal state and while the weld point passes through at least the tension leveler, intermesh of leveler rolls of the tension leveler is reduced lower than the intermesh in the normal state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for temper rolling a metal steel strip by continuously arranging a skin pass mill and a tension leveler. It relates to a manufacturing method.

[0002]

2. Description of the Related Art An ordinary metal steel strip, for example, a cold-rolled steel strip, is subjected to soft annealing after cold rolling, and then to a skin pass mill or a tension leveler for adjusting the material quality and improving flatness. It becomes a product after passing through rolling equipment.
As a skin pass mill, a single four-high rolling mill is generally used for sheet materials such as steel strips for automobiles, and usually 0.2 to 1% to avoid yield point elongation during press working.
A degree of elongation is imparted to the cold rolled steel strip. The tension leveler gives plastic elongation to a cold-rolled steel strip by giving bending deformation in a state where tension is applied. 2 ~
O. It gives an elongation of 5% or more.

[0003] In these temper rolling facilities, in order to continuously process cold-rolled steel strips, welding is generally performed by overlapping the ends of the steel strips on the entry side of a continuous line. However, in this case, since the thickness of the welded portion is larger than the thickness of the base metal, the set conditions before and after the welding point of the cold-rolled steel strip passes through the temper rolling equipment, that is, in the steady state (hereinafter, this In the specification, the steady state refers to a state before and after the welding point of the cold-rolled steel strip passes through the temper rolling equipment.) By causing excessive deformation, there is a risk of plate breakage. Also, the quality of the product may be deteriorated due to the occurrence of flaws on the rolls of the temper rolling equipment, and the flaws are transferred to the steel strip. For example, Japanese Patent Publication No. 3-12970, For example, in Japanese Patent No. 41717, a proposal relating to a driving method of a tension leveler is made.

[0004] Japanese Patent Publication No. 3-12970 discloses that the tension acting on the strip is reduced after the intermesh of the leveler roll has been opened or reduced before the non-leveling portion typified by the welded portion passes through the leveler. Switching from high tension to low tension and switching from low tension to high tension after the weld has passed through the leveler. In addition, JP
-41717, before the weld reaches the leveler,
The elongation or the tension is changed for a predetermined distance to pass through the tension leveler.

[0005] In the case of only a skin pass mill or a tension leveler, the above technique is used, but
Recently, in order to further improve the quality of the cold rolled steel strip, a skin pass mill and a tension leveler have been used together. Mainly, in the skin pass mill, at the same time as the material adjustment and the provision of appropriate surface roughness are performed, while securing a certain degree of flatness, by passing through a tension leveler, it is possible to obtain a completely flat cold-rolled steel strip and Warpage correction has been performed. Generally, a bridle roll is arranged between a skin pass mill and a tension leveler for the purpose of reducing interference between the two. In some cases, the arrangement reduces equipment costs and makes the equipment more compact.

[0006]

SUMMARY OF THE INVENTION In a temper rolling mill in which the skin pass mill and the tension leveler, which are the objects of the present invention, are continuously arranged to reduce the size of the equipment, the operation method when passing through a welding point is described above. Tokuho 3-129
The following problems occur when the technology disclosed in Japanese Patent Application Laid-Open No. 70-17 / 1990 and Japanese Patent Application Laid-Open No. 2-41717 are applied.

In the welding point passing method described in Japanese Patent Publication No. 3-12970, in order to prevent the breakage of the welding point, the line tension is switched from high tension to low tension, and the intermesh of the leveler roll is changed. There is a need to reduce or release from the steady state. On the other hand,
In the welding point passing method described in -41717, it is necessary to reduce the elongation or the tension for a predetermined distance and pass the welding portion. Reducing the elongation value does not substantially reduce the tension, but in any case, when the welding point passes through the tension leveler, the line tension must be reduced from the steady state. It has been.

[0008] The operation method at the time of passing the welding point according to such a method is that in a normal tension leveler, bridle rolls are arranged before and after the leveler, and the tension of the tension leveler can be controlled to a target value. It is considered that this is effective in preventing breakage of the welded portion and preventing flaws in the leveler roll. However, in the continuous equipment of the skin pass mill and the tension leveler which is the object of the present invention, it is impossible to control only the tension of the tension leveler alone. Therefore, when the tension of the leveler portion is changed, the skin pass is inevitable. The tension in front of or behind the mill will change. In this case, a particular problem is that lowering the tension in front of or behind the skin pass mill causes an operation trouble called mill drawing on a steel strip having a rolling width. This is a phenomenon in which the steel strip bites so as to overlap between the rolls of the skin bath mill, and the rolls of the skin pass mill are flawed and the sheet breaks, resulting in a significant decrease in productivity. Will be invited.

As described above, as a method of passing a welding point in a temper rolling facility in which a skin pass mill and a tension leveler are continuously arranged, an operation method for an independently arranged tension leveler cannot be directly applied. The present invention has been made in view of such a situation, and in a temper rolling mill in which the equipment is made compact by continuously arranging a skin pass mill and a tension leveler, a skin pass which becomes a problem when passing a welding point. An object of the present invention is to provide a method for producing a metal steel strip in which both the occurrence of drawing and roll flaws in a mill and the occurrence of roll flaws when passing through a leveler roll are prevented.

[0010]

Means for Solving the Problems In order to solve the above problems, an invention according to claim 1 is a method for temper rolling a metal steel strip by continuously arranging a skin pass mill and a tension leveler, While the welding point of the metal steel strip passes through the skin pass mill and the tension leveler, a step of performing temper rolling by constant tension control is provided.
While the welding point of the metal steel strip passes at least through the skin pass mill, reduce the skin pass mill rolling force from the rolling force in the steady state, and at least while passing the tension leveler, intermesh the leveler roll of the tension leveler. A method for manufacturing a metal steel strip, characterized in that the metal mesh is reduced compared to an intermesh in a steady state.

The invention of claim 2 is to reduce the rolling force of the skin-pass mill from the steady-state rolling force while the welding point of the metal steel strip passes through the skin-pass mill and the tension leveler. 2. The method for manufacturing a metal steel strip according to claim 1, wherein said intermesh is reduced as compared with the intermesh in a steady state.

Furthermore, the invention according to claim 3 is characterized in that, while the welding point of the metal steel strip passes through the skin pass mill, the rolling force of the skin path mill is reduced from the rolling force in a steady state, and
2. The method for producing a metal steel strip according to claim 1, wherein the intermesh of the leveler roll is reduced from the intermesh in a steady state during the passage through the tension leveler.

When the tension leveler is operated alone, the present inventors consider the occurrence of roll flaws when the welding point, which has become thicker than the steady portion due to lap welding, passes through the leveler portion, under various tensions and inter-changes. The setting of the mesh was investigated, and the results shown in FIG. 5 were obtained. From this figure, it can be seen that the occurrence of roll flaws can be prevented by reducing one of the tension and the intermesh as compared to the setting in the steady state. The present invention is based on such a novel finding, and differs from the conventional finding that it is necessary to reduce both the tension and the intermesh, or at least to reduce the tension. That is, according to the present invention, even if the tension at the time of passing through the welding point is maintained at the same value as in the steady state, it becomes clear that no roll flaw is generated by reducing the intermesh, and the tension of the skin pass mill is reduced. The occurrence of mill drawing due to the decrease can be prevented.

When the welding point passes through the skin pass mill, the local height generated between the work roll and the metal steel strip is maintained if the rolling force is maintained at the same level as the steady state setting. Although the surface pressure causes flaws in the work roll, in the present invention, when the welding point passes through the skin pass mill, the rolling force is reduced in advance compared to the setting in the steady state, so the surface pressure is reduced. No flaws are observed.

[0015] From the above knowledge, by lap welding,
When a weld point thicker than the other parts passes through the skin pass mill, the mill tension can be prevented by maintaining the line tension at the same value as the steady state setting, and the By reducing the rolling force, flaws in the rolling roll can be prevented. Furthermore, by reducing the intermesh when passing through the leveler, it is possible to prevent the leveler roll from being damaged.

Next, the reason why the temper rolling is performed by the constant tension control while the welding point of the metal steel strip passes through the temper rolling equipment will be described. Normal temper rolling is performed by elongation rate control that performs control so that the sum of the elongation rates of the skin pass mill and the tension leveler matches the target value. In elongation rate control, in order to compensate for the decrease in elongation rate in the mill caused by reducing the rolling force of the skin pass mill, it is necessary to increase the tension, even when the elongation rate of the leveler part is controlled Similarly, the decrease in elongation caused by reducing the intermesh must be compensated for by increasing the tension. Therefore, if the welding point is passed while the elongation rate is being controlled, a large change in the tension accompanies the operation, which is not preferable in terms of operation stability. In some cases, hunting of tension or elongation may occur due to a delay in the response of the control system to a change in the rolling force of the skin pass mill or a change in the intermesh of the roll leveler. Therefore, as in the present invention, while the welding point of the metal steel strip passes through the skin pass mill and the tension leveler, it is necessary to perform temper rolling by constant tension control.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a temper rolling facility for cold rolled steel strip according to one embodiment of the present invention. This is a line for continuously processing the steel strip 1, and on the upstream side of the entry-side pride roll 2, there is a line for connecting a payoff reel for discharging the cold-rolled steel strip and the cold-rolled steel strip. Equipped with a welding machine. When installed in a continuous annealing line, an annealing furnace is arranged following the welding machine, and a cold rolled steel strip is supplied to the entrance bridle roll 2. Downstream of the entrance bridle roll 2, a skin pass mill 5, a tension leveler 8, and an exit bridle roll 9 are arranged. Since the pride roll is not installed between the skin pass mill 5 and the tension leveler 8, only the tension leveler 8 is installed on the mountain side of the existing skin path mill 5 to realize the temper rolling equipment targeted by the present invention. can do.

In order to measure the tension and elongation of the skin pass mill 5 and the tension leveler 8, a tension meter 3 is used.
a, 3b, 3c and steel strip speed detectors 4a, 4b, 4c are installed. The tension meter 3a and the steel strip speed detector 4a determine the book force T0 between the entrance bridle roll 2 and the skin pass mill 5 and the steel strip speed.
V0 is measured, and the tension meter 3b and the steel strip speed detector 4b determine the tension T1 between the skin pass mill and the tension leveler and the steel strip speed.
Measure V1. The tension meter 3c and the steel strip speed detector 4c are used to measure the tension T2 between the tension leveler and the outgoing bridle roll.
And the steel strip speed V2. At this time, the elongation εM of the skin pass mill can be obtained from the ratio to the steel strip speeds VO and V1, and the elongation 8L of the tension leveler 8 is V1, V
It can be calculated from 2. Further, the sum εT of the elongation percentages of the skin pass mill and the tension leveler is expressed by the steel strip speed VO, V
It can be obtained from the ratio of 2.

On the other hand, with respect to the elongation rate control using such a measuring instrument, several methods are possible, one example of which is described below. As the elongation rate control in the steady portion, the rolling position S of the skin pass mill is changed such that the sum εT of the elongation rates of the skin pass mill and the tension leveler matches the target value while keeping the tension leveler intermesh at a constant value. By changing the rolling position S,
The rolling force in the skin pass mill changes, and the elongation εM of the skin pass mill is mainly corrected. At the same time, when the steel strip speed V1 and the tension T1 change, the elongation rate εL of the tension leveler also changes at the same time.

The line speed VO is controlled by the rotation speed M2 of the entrance bridle roll 2, and the tension TO is determined by a skin pass mill.
Controlled by a roll rotation speed M5 of 5. Furthermore, tension T
1 is controlled by the rotation speed M9 of the output bridle roll, which is the case where the tension T2 is controlled by the rotation speed M9 of the output bridle roll 9. As an embodiment of the present invention, a method for independently controlling the elongation rate εM of the skin pass mill 5 and the elongation rate εL of the tension leveler 8 is described in JP-A-9-85341 or JP-A-7-68319. A method may be used.

According to the above method, before and after the welding point passes through the skin pass mill and the tension leveler, a cold-rolled steel strip is manufactured by controlling the elongation, and while the welding point of the cold-rolled steel strip passes through the skin pass mill and the tension leveler. That is, the control method is switched from the point A of the entrance bridle roll 2 to the point B of the exit bridle roll 9 to constant tension control. When the control is switched to the constant tension control, as in the case of the elongation control method, the TO is set to the roll rotation speed M5 of the skin pass mill 5.
And T1 or T2 is controlled by the rotation speeds M2 and M9 of the entrance and exit bridle rolls. However,
Since the elongation rate control is not performed, the rolling position of the skin pass mill can be freely changed, and the rolling force when passing through the welding point can be reduced as compared with the steady portion. In addition,
These control methods are changed based on the tracking information of the welding point, and when the welding point reaches a certain distance before passing through the skin pass mill, the control is switched from the elongation rate control to the constant tension control, and the welding is performed. After the point passes through the tension leveler, the control is switched again from the constant tension control to the elongation rate control. The switching between the elongation rate control and the tension control as described above, the setting of the target values of the tension and the elongation rate, the setting of the intermesh of the tension leveler 8, and the like are performed by the control device 13.

A more specific control method will be described with reference to FIG. The figure shows a control method accompanying the passage of the welding point. When the welding point reaches the point A of the entrance-side bridle roll 2, switching from the elongation rate control to the constant tension control is performed. Thereafter, when the welding point reaches the skin pass mill 5, the rolling force is changed in advance so that the rolling force is sufficiently reduced. At the same time, the intermesh of the tension leveler 8 is passed through the welding point in a reduced state. When the welding point passes through the tension leveler 8, the skin pass mill 5 and the tension leveler 8 are returned to the set values, and then, when the point B of the exit side bridle roll 9 is reached, the tension is returned from the constant tension control to the elongation rate control. .

On the other hand, as shown in FIG. 3, the rolling force is reduced only while the welding point passes through the skin pass mill 5, and after the passing, the rolling force is restored. By reducing the intermesh only during the passage, the length of the off-tempered portion and the off-leveler portion near the welding point can be reduced, and the yield can be improved.

As an embodiment of the present invention, an example in which a skin pass mill and a tension leveler are arranged in this order has been described. However, the present invention is not limited to this order. It also works effectively for rolling mill trains. Further, the form in which the skin pass mill and the tension leveler are continuously arranged means that there is no equipment such as a bridle roll for positively controlling the tension of the cold-rolled steel sheet therebetween. Therefore, it does not matter whether there is a measuring instrument such as a tensiometer or an auxiliary roll such as an anti-cross roll. Although the cold rolled steel strip is described as an example in the embodiment of the present invention, the present invention may be applied to a method for manufacturing a high-performance thin steel strip such as a hot-dip coated steel strip or an electromagnetic steel strip.

[0025]

EXAMPLE An example according to the present invention will be described with reference to the results obtained by the control method shown in FIG. 2 using the temper rolling equipment shown in FIG. In this example, a cold rolled steel strip having a thickness of 1.2 mm and a width of 1250 mm softened by cold rolling and continuous annealing was continuously temper rolled. The skin pass mill 5 is a single four-high rolling mill, and has a work roll diameter of 500 mm. The tension leveler 8 is composed of an extension unit 11 and a warp straightening unit 12. The work roll diameter of the extension unit 11 is φ35 mm, and the work roll diameter of the warp straightening unit 12 is φ35.
45 mm.

The operating conditions in the steady state are as follows. For a line speed of 150 mpm, the rolling force of the skin pass mill 5 is 3 on average.
50kN, elongation is 0.8%. At this time, the tension T0 between the entrance side bridle roll 2 and the skin pass mill 5 is 68MP.
a, tension T between skin pass mill 5 and tension leveler 8
1 is controlled at 70MPa. Also, tension leveler
The intermesh of the elongation unit 11 of 8 is set to 5 mm, and the intermesh of the warp straightening unit 12 is set to 8 mm, and the elongation at the leveler is 0.5%. As actual control, control is performed so that the sum of the elongation percentages of the skin pass mill 5 and the tension leveler 8 is 1.3%.

By operating the skin pass mill alone and examining the rolling force at which flaws occur on the rolls of the skin pass mill when passing through the welding point, if the rolling force per sheet width is 1200 kN / m or less, It was found that there was no flaw on the rolling roll. Therefore, in the present embodiment, the setting was made so that the rolling force in the skin pass mill when passing through the welding point was 1500 kN or less.

Based on such conditions, the operation using both the skin pass mill and the tension leveler is performed. Before the welding point reaches the skin pass mill, switching from the elongation rate control to the constant tension control is performed. , A test in which the tension T1 and the intermesh of the tension leveler were variously changed. The result is shown in FIG. From the figure,
This indicates that roll flaws are likely to occur when the intermesh and the tension T1 are large. However, even if the tension is high, if the intermesh is small, a roll flaw is not generated, or if the tension is small even if the intermesh is large, no roll flaw is generated.
However, when the tension T1 was small, the cold-rolled steel strip was squeezed in the skin pass mill, resulting in an operation trouble.

From the above, in order to prevent the occurrence of roll eaves in the skin pass mill and the tension leveler and eliminate operational troubles in the skin pass mill, the tension at the time of passing through the welding point should be the same as that of the steady portion, or the extent that no mill drawing occurs. And the rolling force of the skin pass mill is reduced.
It is necessary to set the roll gap so as to be 1500 kN or less and to set the tension leveler intermesh to 2 mm or less. By the way, the lower limit of the intermesh in this case is preferably 0 mm, and it is not preferable to completely open the leveler. This means that even if the intermesh is 0 mm, bending deformation corresponding to the thickness of the cold-rolled steel strip occurs, and the roll and the cold-rolled steel strip maintain a contact state, When the leveler is opened, there is a difference that the roll does not come into contact with the steel strip.In general, the roll of the tension leveler is not driven,
The reason for this is that when re-reduction is performed after the release of the reduction, the stopped roll comes into contact with the moving steel strip and a flaw is generated.

By adopting the welding point passing method as described above, stable operation can be realized without troubles such as roll flaws and mill drawing, but roll flaws are generated on the cold rolled steel strip. The intermesh is not always an appropriate value because it changes depending on conditions such as strength and the thickness of the welded portion, but as a result of the investigation by the present inventors, the welding point was set at the same tension as in the steady state. It has been found that when passing, the intermesh is set so as to be equal to or less than a value obtained by triple the ratio of the plate thickness of the steady portion to the plate thickness before passing through the tension leveler, so that roll flaws of the leveler can be prevented.

[0031]

As described above in detail, according to the present invention, the skin-pass mill rolling force is reduced from the steady-state rolling force at least while the welding point of the metal steel strip passes through the skin-pass mill, and at least the tension is reduced. By reducing the intermesh of the leveler roll of the tension leveler during passing through the leveler from the intermesh in the steady state, it prevents mill drawing and roll flaws that occur near the welded portion of the continuously passing metal steel strip. As a result, stable production of metal steel strips without troubles becomes possible.

[Brief description of the drawings]

FIG. 1 is a view showing a temper rolling facility of a cold-rolled steel strip for carrying out the present invention.

FIG. 2 is a diagram showing an example of a welding point passing method according to the invention.

FIG. 3 is a diagram showing another example of the welding point passing method according to the invention.

FIG. 4 is a diagram showing an operation result according to the present invention.

FIG. 5 is a diagram showing a relationship between operating conditions of a tension leveler and a state of occurrence of roll flaws.

[Explanation of symbols]

1: steel strip, 2: entrance side bridle roll, 3a, 3b, 3c: tension meter roll, 4a, 4b, 4c: plate speedometer, 5: skin pass mill, 6: sub-unit, 7: intermesh setting signal, 8: tension leveler, 9: exit bridle roll, 10: anti-cross roll, 11: extension unit, 12:
Warp straightening unit, 13: Temper rolling equipment control device, M2: Rotation speed of entrance bridle roll, M5: Roll rotation speed of skin pass mill, M9: Rotation speed of exit bridle roll, A point, B point: Tension control Switching position

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Madate 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Akihiro Nagahiro 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun Inside the Kokan Co., Ltd. (72) Inventor Osamu Uehara 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. F-term (reference) 4E002 AD06 BC03 BC04 BD20 CB03 CB09 4E024 BB10 CC02 EE01 FF04

Claims (3)

[Claims] 1. A method for temper rolling a metal steel strip by continuously arranging a skin pass mill and a tension leveler, wherein a tension is applied while a welding point of the metal steel strip passes through the skin pass mill and the tension leveler. A step of performing temper rolling by constant control, in this step, while the welding point of the metal steel strip passes at least through the skin pass mill, reduce the skin pass mill rolling force than the steady state rolling force, and at least tension. A method for manufacturing a metal steel strip, wherein the intermesh of a leveler roll of a tension leveler is reduced from that in a steady state while passing through a leveler. 2. While the welding point of the metal steel strip passes through the skin pass mill and the tension leveler, the skin pass mill rolling force is reduced from the steady state rolling force, and
The method for manufacturing a metal steel strip according to claim 1, wherein the intermesh of the leveler roll is reduced as compared with the intermesh in a steady state. 3. While the welding point of the metal steel strip passes through the skin pass mill, the rolling force of the skin pass mill is reduced from the rolling force in a steady state, and the intermesh of the leveler roll is reduced while passing through the tension leveler. The method for producing a metal steel strip according to claim 1, wherein the metal steel strip is reduced compared to an intermesh in a steady state.