JP2001239301A - Method of preventing warpage in temper rolling of metal strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of skin pass rolling by which a one-sided overdraft can be prevented without highly increasing equipment investment and decreasing the productivity. SOLUTION: When supplying skin pass rolling agents which are subtle liquid drops mixed with gas on the upper face and lower face of a metal in coil for skin pass rolling, an amount supplying skin pass rolling agents to the upper face and/or lower face is partially changed in the width direction in accordance with the overdraft in the longitudinal direction of the metal in coil by skin pass rolling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing one-sided warpage generated during temper rolling of a metal strip.

[0002]

2. Description of the Related Art For example, a cold-rolled steel strip is subjected to temper rolling at an elongation of about 0.5% to 3.0% after annealing. When it is cut into several sections, warpage in the longitudinal direction may occur. Since this warping causes trouble in handling, a steel strip having a small warpage is required.

As a countermeasure for warpage in temper rolling, a method of adjusting a difference in roughness between upper and lower work rolls and a method of adjusting a position of a pass line are known. These methods are effective for uniform longitudinal warpage in the width direction. However, if the warpage in the longitudinal direction is not uniform in the width direction due to uneven roll wear in the width direction or bending of the work roll in the horizontal plane, the warp cannot be prevented over the entire width. Hereinafter, uneven warpage in the width direction is referred to as one-sided warpage.

Various methods have been proposed as a countermeasure against this one-sided warpage.

For example, Japanese Patent Application Laid-Open No. Hei 3-138012 discloses that the widthwise surface of a work roll of a temper rolling mill is partially polished in accordance with one-sided warpage to partially reduce the widthwise roughness of the work roll. A method of changing is disclosed.

[0006] Japanese Patent Application Laid-Open No. 7-68301 discloses that
There is disclosed a method of supplying a larger amount of coolant at an edge portion of a steel sheet than at a portion other than the edge.

Further, Japanese Patent Application Laid-Open No. HEI 8-112601 discloses that a work roll having a wear-resistant surface treatment is used and the surface roughness of the work roll in the plate width direction at a portion corresponding to the inside of the plate width. A method is disclosed in which the Ra difference is set to 20% or less of the work roll roughness Ra, the iron powder concentration in the lubricating liquid is set to 20 ppm or less, and wet rolling is performed at a rolling reduction of 3% or more.

[0008]

However, the method disclosed in Japanese Patent Application Laid-Open No. Hei 3-138012 has a problem that the number of times of roll polishing is increased, so that the roll life is shortened and the polishing cost is increased. In addition, this method requires a new roll polishing machine, and has a problem that equipment costs are increased.

Although the method disclosed in Japanese Patent Application Laid-Open No. 7-68301 can make the flow rate uniform in the width direction, it is not sufficient as a countermeasure against partial partial warpage caused by uneven wear of the roll.

In addition, the method disclosed in Japanese Patent Application Laid-Open No. Hei 8-112601 has a problem that productivity is reduced due to control of roll roughness and concentration of iron powder in lubricating oil. Also,
This method is not enough as a countermeasure against warpage.

It is an object of the present invention to provide a method capable of preventing one-sided warpage without significant capital investment and a decrease in productivity.

[0012]

The inventors of the present invention disclosed in Japanese Patent Application Laid-Open No. Hei 8-215705 a mixture of a temper rolling agent and a gas to form droplets having an average diameter of 30 μm or less on the upper and lower surfaces of a metal strip. And a temper rolling method performed by spraying on it.

[0013] To solve the above-mentioned problems, the present inventors have
A method for preventing warpage based on the temper rolling method disclosed in the above publication was examined, and the following findings were obtained.

A. When supplying the temper rolling agent as fine droplets to the surface of the material to be rolled, if the supply amount of the temper rolling agent is changed, the amount of the temper rolling agent adhering to the material to be rolled changes,
The state of lubrication between the roll and the material to be rolled changes. Therefore, the lubrication state can be changed in the width direction by changing the supply amount of the temper rolling agent in the width direction.

B. By changing the supply amount of the temper rolling agent between the upper surface and the lower surface, the warpage in the longitudinal direction changes.

C. Therefore, by changing the supply amount of the temper rolling agent between the upper surface and the lower surface and partially changing the supply amount in the width direction, it is possible to suppress the occurrence of the warpage.

The present invention has been completed based on the above findings, and the gist thereof is as follows.

(1) In temper rolling performed by supplying a temper rolling agent, which is a mixture of gas and formed into fine droplets, to the upper and lower surfaces of the metal strip, warping in the longitudinal direction of the metal strip due to temper rolling. A method for preventing warpage in temper rolling of a metal strip, wherein the supply amount of a temper rolling agent to an upper surface and / or a lower surface is changed accordingly.

(2) The method for preventing warpage in temper rolling of a metal strip as described in (1) above, wherein the supply amount of the temper rolling agent is partially changed in the width direction.

(3) When the warpage is upward, the supply amount to the upper surface is increased and / or the supply amount to the lower surface is reduced. When the warpage is downward, the supply amount to the lower surface is increased and / or The method for preventing warpage in temper rolling as described in the above item (1) or (2), wherein the supply amount to the upper surface is reduced.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings, wherein a metal strip is a steel strip.

FIG. 1 is a schematic view of a temper rolling apparatus for explaining an embodiment of the present invention. Reference numeral 1 denotes a temper rolling mill, 2 denotes a work roll, 3 denotes a nozzle, 4 denotes a steel strip, and 5 denotes a gas. The pressure setting device 6 is a hydraulic pressure setting device.

As shown in FIG. 1, the temper rolling apparatus according to the present invention comprises a plurality of temper rolling mills 1 having work rolls 2 on the upper and lower sides with a steel strip interposed between the upper and lower sides and the width direction of the steel strip. Nozzle 3 is provided. Hereinafter, a work roll is also simply called a roll.

In the temper rolling by this temper rolling device, a temper rolling agent mixed with gas and formed into fine droplets is sprayed from the nozzle 3 onto the upper and lower surfaces of the steel strip 4 and supplied to the upper and lower surfaces. Do it.

In this embodiment, the steel strip after temper rolling is cut into several strips, the warp in the longitudinal direction of each strip is measured, and the warp is applied to the upper surface and / or lower surface according to the warp. Temper rolling is performed by partially changing the supply amount of the temper rolling agent in the width direction.

For example, when the warpage is upward warpage, the supply amount from the upper nozzle provided at the width direction corresponding to the upward warp to the upper surface is increased and / or the upward warpage occurs when the upward warpage occurs. The amount of supply from the lower nozzle provided at the position in the width direction to the lower surface is reduced. In the case of downward warpage, the amount of supply from the upper nozzle to the upper surface provided at the widthwise position corresponding to the downwardly warped strip is reduced and / or the widthwise position corresponding to the downwardly warped strip is reduced. The amount of supply from the provided lower nozzle to the lower surface is increased. As described above, by partially changing the supply amount to the upper surface and / or the lower surface in the width direction, it is possible to reduce the warpage after the temper rolling.

Next, the method of the present invention will be described by way of specific examples.

FIG. 2 shows that the upper roll has a uniform roughness in the width direction, the lower roll has a small roughness at both ends, and a large roll at the center. FIG. 4A is a graph showing the widthwise distribution of the amount of warpage after temper rolling is performed by spraying a temper rolling agent on the steel strip surface with nozzles provided at five locations at the top and bottom, respectively. FIG. (B), the supply amount from the upper nozzle at the width end is increased by the method of the present invention from the condition of (a).
This is the case when the supply amount from the other nozzles is the same as the condition (a). In addition, the amount of warpage is obtained by cutting a steel strip after rolling into several sections and measuring the warp height of each section.

In general, when rolling is carried out using a roll having an uneven roughness, it is difficult to expand on the high roughness side and easily on the low roughness side.
Therefore, if the roughness of the upper roll and the lower roll is partially different in the width direction, one-sided warpage occurs as shown in FIG.

On the other hand, by partially changing the supply amount, the lubrication state between the roll and the material to be rolled is partially changed, and the elongation can be partially adjusted.

Therefore, as shown in FIG. 2 (a), when upward warpage occurs at the width end, the supply amount from the upper nozzle at the width end to the upper surface is reduced by the lower nozzle at the width end. By performing rolling with a larger amount than the supply amount from the bottom to the lower surface, as shown in FIG. 2B, it is possible to reduce the warpage of the end portion.

That is, by partially changing the amount of supply to the upper surface and the lower surface in the width direction, it is possible to change the lubrication state between the roll and the material to be rolled at that portion, and to control the warpage. .

The temper rolling agent used in the present invention is a liquid used for lubricating the roll and the steel strip at the time of temper rolling.
An aqueous solution in which an organic lubricant is mixed with water at a concentration of several% to several tens% is used. Air is usually used as the gas mixed with the temper rolling agent in order to make the temper rolling agent into fine droplets, but other gases may be used. Droplet size is 3
It is good to be 0 μm or less.

In the present embodiment, an example is shown in which a temper rolling agent is directly sprayed on the steel strip surface at the entrance side of the temper rolling mill.
The present invention is not limited to this, and may be sprayed on the roll surface, or may be sprayed on both the steel strip surface and the roll surface. However, as shown in FIG. 1, a method in which a temper rolling agent is sprayed on the steel strip surface is desirable. On this occasion,
The interval between adjacent nozzles and the distance between the nozzle and the steel strip are preferably determined so that the temper rolling agents injected from adjacent nozzles do not interfere with each other.

In this embodiment, the example of the two-high rolling mill is shown as the temper rolling mill. However, the present invention is not particularly limited to the type of the rolling mill. For example, a work roll and a backup roll are provided. It may be a four-high rolling mill or a six-high rolling mill provided with an intermediate roll in addition to the work roll and the backup roll.

Next, embodiments of the present invention will be described in the following three cases.

Case 1: Rolling by Work Rolls with Partially Different Roll Roughness Rolls incorporated in a rolling mill by changing rolls are polished almost uniformly in advance, and the variation in roll roughness is small. Therefore, in the early stage of rolling, the occurrence of warpage due to the roughness of the roll hardly causes a problem.

In general, as the pressure elongation increases, the roll abrasion progresses, so that the roll roughness decreases. Usually, when the roll roughness level required for the steel sheet is satisfied, the roll is continuously used, and when the roll roughness falls below a certain value, the roll is replaced.

However, the reduction in roll roughness is affected by the pressure distribution and the lubrication state during rolling, and a difference in roll roughness occurs between the upper roll and the lower roll and at positions in the width direction. When this difference is equal to or greater than a predetermined value, the one-sided warpage increases.

According to the method of the present invention, the lubrication state of the upper surface and the lower surface can be partially adjusted in the width direction. Therefore, when uneven wear occurs on a part of the roll and the roughness of the roll decreases, the supply amount at that position is reduced as compared with the other parts. As a result, the coefficient of friction between the roll and the material to be rolled at that portion increases, and the residual stress difference between the upper and lower surfaces of the steel strip, which causes warpage, can be reduced. In addition,
The same effect can be obtained by increasing the supply amount at a position other than the unevenly worn portion and lowering the friction coefficient, but the former is more advantageous in terms of ease of control and the amount of the temper rolling agent used. .

Further, by reducing the supply amount to the unevenly worn portion, the thickness of the temper rolling agent at the unevenly worn portion is reduced, and the transfer rate of the roll roughness is increased. There is also an effect that the roughness difference is reduced.

Case 2: Rolling of a steel plate with poor flatness Generally, in temper rolling, in order to prevent narrowing at the entry side and prevent cross buckles at the exit side during rolling, the steel strip on the upper roll side is used. Is set smaller than the lower roll side, and the amount of the temper rolling agent supplied to the roll tool is different between the upper surface and the lower surface. Therefore, the lubrication state is different between the upper surface and the lower surface, and when temper rolling of a poorly flat steel sheet is performed, the lubrication state between the roll and the material to be rolled further becomes uneven in the width direction, and one-sided warpage easily occurs.

According to the method of the present invention, it is possible to partially adjust the lubrication state of the upper surface and the lower surface in the width direction. Can be.

Case 3: Rolling a steel sheet having non-uniform surface properties On the surface of a metal strip subjected to temper rolling, an oxide adheres or a thick layer of Si or Mn is formed. Sometimes. In addition, these oxides and concentrated layers may have a thickness distribution in the width direction due to a defect in the annealing step or the pickling step.

When such a metal strip is rolled, the lubricating state is different between the upper surface and the lower surface, and the lubricating state is not uniform in the width direction, so that one-sided warpage is likely to occur.

According to the method of the present invention, the lubrication state of the upper surface and the lower surface can be partially adjusted in the width direction. Therefore, even when a steel sheet having a non-uniform surface texture is rolled, the occurrence of the warpage can be prevented. Can be reduced.

Next, a method of adjusting the supply amount of the temper rolling agent in the present invention will be described.

FIG. 3 schematically shows the change in the amount of the temper rolling agent (hereinafter also referred to as the injection amount) and the diameter of the droplet when the liquid pressure and the gas pressure are changed in the method of the present invention. FIG.

As shown in FIG. 3, the injection amount can be adjusted by changing the liquid pressure and the gas pressure while keeping the droplet diameter in an appropriate range. Therefore, in order to change the supply amount in the width direction, the liquid pressure and the gas pressure of a plurality of nozzles provided in the width direction may be adjusted to change the injection amount of each nozzle.

FIG. 4 is a sectional view showing an example of a nozzle used in the present invention. 3 is a nozzle, 10 is a first injection pipe,
11 is a second injection pipe, 12 is a temper rolling agent, 13 is a gas, 1
4 is a droplet.

As shown in FIG. 4, the nozzle 3 has a structure having a second injection pipe 11 for injecting a temper rolling agent into the inside thereof and a first injection pipe 10 for injecting a gas to the outside thereof. The gas 13 can be mixed with the agent 12 and ejected as fine droplets 14.

In the embodiment of the present invention, the method of measuring the warpage in the longitudinal direction of the cut strip and controlling the one-side warpage by partially changing the supply amount according to the warp has been described. Is not limited to this. For example,
A warp detector is installed on the outlet side of the temper rolling mill, the distribution of warpage is measured in the width direction, and the feed rate is controlled by a method of feeding back a signal to a control device attached to the nozzle via an arithmetic unit, and online The warpage may be adjusted.

[0053]

EXAMPLE (Comparative Example) Diameter 500 of the basic configuration shown in FIG.
Using a two-stage temper rolling mill having a roll of mm and a temper rolling device equipped with a nozzle for spraying a temper rolling agent on the surface of the steel strip, under the conditions shown in Table 1, a sheet thickness: 0.8 mm, Board width:
1200mm bright finished plain steel coil (carbon:
Temper rolling of 0.01 to 0.03 mass%) was performed.

[0054]

[Table 1]

FIG. 5 shows the widthwise distribution of the surface roughness of the roll at the start of the temper rolling. For the rolls, the rolling distance is used for temper rolling at a distance of about 100 km. As shown in FIG. 5, the upper roll and the lower roll have the same surface roughness at the center of the width and wear at the end of the width. A roll having a significantly lower surface roughness than the upper roll was used.

On the upper and lower sides of the entrance side of the temper rolling mill, nozzles having an opening diameter of 0.2 mm having a structure shown in FIG.
The nozzles are arranged at five vertically symmetrical positions at both ends, both 1/4 width parts and the center part, and as shown in Table 2, all nozzles (A _U
~ E _U , A _{L to} E _L ).

[0057]

[Table 2]

The nozzle interval was 200 mm, the distance between the nozzle and the steel plate was 300 mm, and the nozzle opening was directed perpendicular to the steel strip. An aqueous solution containing 10% of an organic lubricant was used as a temper rolling agent, and air was used as a gas.

The steel sheet after temper rolling was cut at intervals of 150 mm in width, and the warp in the longitudinal direction of each of the cut steel sheets was examined.

FIG. 6 is a graph showing the distribution of longitudinal warpage in the width direction. As shown in the figure, warpage occurred at both ends.

(Example of the present invention) Based on the results of the temper rolling of the comparative example, the same temper rolling apparatus as used in the comparative example 1 was used, and the amount of injection from some nozzles was changed to perform the temper rolling. Carried out. Table 3 shows the air pressure, liquid pressure, and injection amount of each nozzle. The conditions other than the injection amount were the same as those of the comparative example.

[0062]

[Table 3]

As shown in the table, upper and lower nozzles (B _U , B _L ) at the center and upper and lower nozzles (C _U , C _L , D _U ,
D _L ) and the injection amount from the upper nozzle (A _U , E _U ) at the end were the same as in Table 2, and only the injection amount from the lower nozzle (A _L , E _L ) at the end was reduced.

The steel sheet after temper rolling was cut at an interval of 150 mm in width, and the warpage in the longitudinal direction of each of the cut steel sheets was examined.

FIG. 7 is a graph showing the distribution of longitudinal warpage in the width direction.

As shown in the figure, the degree of warpage in the longitudinal direction was significantly reduced as compared with the comparative example.

[0067]

According to the present invention, the lubricating state between the roll and the material to be rolled can be partially changed, and the warpage after temper rolling can be greatly reduced. For example, even if the surface roughness of the work roll partially decreases due to abrasion, it is possible to perform rolling in which the warpage is suppressed. Therefore, the frequency of changing rolls can be suppressed, and the productivity is greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a temper rolling device illustrating an embodiment of the present invention.

FIG. 2 is a graph showing a widthwise distribution of an amount of warpage after temper rolling. FIG. 2 (a) shows the case where the supply amount from each nozzle is the same in the conventional method, and FIG. This is the case when the supply amount is partially changed by the method of the present invention.

FIG. 3 is a diagram schematically showing changes in the amount of a temper rolling agent and droplet diameters ejected from a nozzle when the liquid pressure and the gas pressure are changed in the method of the present invention.

FIG. 4 is a sectional view showing an example of a nozzle used in the present invention.

FIG. 5 shows the width distribution of the surface roughness of the roll at the start of the temper rolling.

FIG. 6 is a graph showing a distribution of longitudinal warpage in a width direction.

FIG. 7 is a graph showing a widthwise distribution of longitudinal warpage.

[Explanation of symbols]

1: temper rolling mill, 2: work roll, 3: nozzle, 4:
Steel strip, 5: gas pressure setting device, 6: hydraulic pressure setting device, 10:
1st injection pipe, 11: 2nd injection pipe, 12: temper rolling agent, 1
3: gas, 14: droplet.

Claims (3)

[Claims] In a temper rolling performed by supplying a temper rolling agent into fine droplets by mixing a gas to an upper surface and a lower surface of a metal strip, according to a longitudinal warpage of the metal strip caused by the temper rolling. And changing the supply amount of the temper rolling agent to the upper surface and / or the lower surface. 2. The method according to claim 1, wherein the supply amount of the temper rolling agent is partially changed in the width direction. 3. When the warpage is upward, the supply amount to the upper surface is increased and / or the supply amount to the lower surface is reduced. When the warpage is downward, the supply amount to the lower surface is increased and / or the upper surface is increased. 3. The method for preventing skew in temper rolling according to claim 1 or 2, wherein the amount of supply to the steel sheet is reduced.