JP3858807B2 - Cold tandem rolling mill - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cold tandem rolling mill, and more particularly to a cold tandem rolling mill capable of rolling a steel strip such as a tin plate or a galvanized plate at a high speed.
[0002]
[Prior art]
A cold tandem rolling mill in which rolling mills are arranged in a plurality of tandems is used for cold rolling of a steel strip such as a metal strip, for example, a tin plate or a galvanized plate. As a cold tandem rolling mill for rolling such a steel strip at a high speed, there is known one employing a direct rolling lubricant supply system as shown in FIG.
[0003]
The rolling lubrication oil supply system of the direct system generally sprays a nozzle 5 for spraying rolling lubricant for lubricating between the steel strip 1 and the work roll 2 and cooling water for cooling the rolled steel strip 1. The metal strip cooling nozzle 8 and the roll cooling nozzle 9 for spraying the cooling water for cooling the work roll 2 are provided, and the rolling lubricating oil and the cooling water are supplied by different systems.
[0004]
FIG. 3 is a schematic diagram showing a main part of a rolling lubricant supply system in a conventional cold tandem rolling mill, wherein reference numeral 1 denotes a steel strip that is a metal strip, and reference numeral 2 denotes a work roll. . The work roll 2 is assembled vertically with a steel strip 1 sandwiched between stands (not shown). Reference numeral 3 denotes a backup roll, and the backup roll 3 reinforces a work roll 2 that rolls the steel strip 1. Reference numeral 4 is an auxiliary roll installed between the stands, and the auxiliary roll 4 is cold for restricting the height direction pass line position of the steel strip 1 or measuring the tension of the steel strip 1. The steel strip 1 is in contact during rolling.
[0005]
Further, reference numeral 6 in FIG. 3 denotes a rolling lubricating oil supply pipe, and a nozzle 5 is connected to the rolling lubricating oil supply pipe 6 so that the rolling lubricating oil can be sprayed from the nozzle 5 toward the steel strip surface. Reference numeral 10 is an arrow indicating the rolling direction of the steel strip 1. A plurality of nozzles 5 for spraying the rolling lubricating oil are arranged along the width direction of the steel strip 1 above and below the steel strip 1 on the entry side of each stand. The nozzle 8 is a strip cooling nozzle that cools the steel strip by spraying cooling water onto the steel strip 1, and the strip cooling nozzle 8 is downstream of the nozzle 5 that sprays the rolling lubricating oil, and A plurality of steel strips 1 are arranged along the width direction of the steel strip 1 above and below the steel strip 1 on the entry side of each stand. The nozzle 9 is a roll cooling nozzle that cools the work roll 2 by spraying cooling water onto the work roll 2, and the roll cooling nozzle 9 extends along the width direction of the work roll 2 in the immediate vicinity of the entry side of each stand. Are arranged.
[0006]
In a cold tandem rolling mill in which a plurality of such nozzles are arranged, when cold rolling the steel strip 1, rolling lubricant is sprayed onto the surface of the steel strip from the nozzle 5 on the entrance side of each stand. A cold-rolled steel sheet having a desired thickness is obtained by rolling down the steel sheet with the work roll 2 sequentially from the upstream side while performing lubrication between the work roll 1 and the work roll 2 and cooling the steel strip 1 and the work roll 2. can do. At that time, in the cold tandem rolling mill employing the direct rolling lubricant supply system, the supply of the rolling lubricant contributing to the lubrication between the metal strip and the work roll 2, the cooling of the metal strip, and the cooling of the work roll Because it is performed in a separate system, seizure due to insufficient lubrication between the metal strip and the work roll, called heat scratch, is difficult to occur, and after spraying on the metal strip surface, it mixes with cooling water. In addition, the used rolling lubricant is not reused and is reused as a rolling lubricant after separating the oil so that foreign matter such as roll abrasion powder and iron powder is within the control range.
[0007]
For this reason, it is said that it is suitable for cold-rolling steel strips such as tin plate and galvanized plate that have strict requirements on surface properties.
Recently, in cold tandem rolling mills that employ a direct rolling lubricant supply system, indentation defects sometimes occur on the surface of the cold-rolled steel strip. FIG. 4 is a plan view showing the position of the indentation defect generated on the surface of the cold-rolled steel strip, where A indicates the generation range of the indentation defect and B indicates the width of the cold-rolled steel strip.
[0008]
The present inventors diligently investigated the cause of the indentation defect generated on the surface of the cold-rolled steel strip, and found out that this indentation defect was a surface defect caused by smudge accumulated on the surface of the auxiliary roll. . That is, as a recent trend, the thickness of the material supplied to the cold tandem rolling mill has increased, while the product thickness has decreased, so that the reduction rate at each stand has increased, and the work roll has been changed. Work roll wear powder generated by sliding friction between the work roll and the steel strip due to the use of a work roll with a rough surface in the front stand to increase the amount of rolling processing until The amount of iron powder on the surface of the steel strip increased, and these foreign substances adhered to the surface of the auxiliary roll and deposited, forming smudge. It was found that this smudge adheres to the surface of the steel strip that comes into contact with the auxiliary roll during cold rolling, and is pressed down by the work roll as it is to cause an indentation defect.
[0009]
In order to prevent indentation defects caused by the smudge formed on the auxiliary roll, conventionally, the surface of the metal strip is washed by washing away the smudge attached to the surface of the metal strip with the cooling water sprayed from the nozzle 8 for cooling the metal strip. I was trying to improve the properties.
However, in a cold tandem rolling mill, if the spray pressure of the cooling water that cools the metal strip is increased to remove the smudge adhering to the surface of the metal strip, the rolling lubricant adhering to the surface of the metal strip will be washed away. There is a problem in that the rolling efficiency has to be lowered because the adhesion efficiency of the rolling lubricating oil is deteriorated and seizure due to insufficient lubrication referred to as heat scratch is generated. Also, in a stand that is prone to insufficient lubrication in a cold tandem rolling mill, supply the rolling lubricant at a temperature of 80 ° C or higher, drain water between the rolling lubricant supply device and the roll bite inlet, or roll A cold tandem rolling method that employs one or more means to prevent heat scratches occurring on the surface of the metal strip is disclosed (for example, for supplying rolling lubricant to the work roll from the machine exit side (for example, Patent Document 1).
[0010]
[Patent Document 1]
JP 2000-218305 A [0011]
[Problems to be solved by the invention]
However, the cold tandem rolling method described in Japanese Patent Application Laid-Open No. 2000-218305 has a possibility of greatly affecting the surface properties of the metal strip because the lubrication state between the work roll and the metal strip is changed. Was difficult.
Therefore, the present invention is to solve the above-mentioned problems of the prior art, and while maintaining the rolling speed, the present invention is a cooling capable of preventing surface defects such as heat scratches and indentation defects that occur on the surface of the metal strip. An object is to provide an inter-tandem rolling mill.
[0012]
[Means for Solving the Problems]
The present inventors have intensively studied and used a device for spraying cleaning oil on the surface of the auxiliary roll as a means for preventing foreign matter adhering to the surface of the metal strip, which is the root cause of the indentation defect, from accumulating on the surface of the auxiliary roll. The present invention was completed by obtaining the knowledge that the indentation defects can be effectively suppressed by providing them. At that time, it has also been found that spraying warm water on the surface of the auxiliary roll has a very small effect of suppressing foreign matter adhering to the surface of the metal strip from accumulating on the surface of the auxiliary roll and becoming smudge.
[0013]
The present invention is as follows.
1. A cold tandem rolling mill in which auxiliary rolls are installed at a plurality of locations along a metal strip pass line, wherein at least one of the auxiliary rolls has cleaning oil directed toward the roll surface. And a nozzle of the auxiliary roll cleaning device is provided to face a body length direction portion of the auxiliary roll corresponding to an end in the width direction of the metal strip. A cold tandem rolling mill characterized by that.
2. The auxiliary roll cleaning device includes a nozzle and a branch pipe connected to the nozzle, and the branch pipe is connected to a lubricant supply pipe for sending rolling lubricant, and the rolling lubricant can be sprayed toward the auxiliary roll. The above 1. is characterized in that The cold tandem rolling mill described in 1 .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the case where this invention is applied to the cold tandem rolling mill which cold-rolls a steel strip is demonstrated using FIG.
FIG. 1 is a schematic diagram showing the main part in the vicinity of the first and second stands of a cold tandem rolling mill comprising six stands according to the embodiment of the present invention, and FIG. 2 is a diagram showing the cold parts shown in FIG. It is a layout of an auxiliary roll cleaning device installed on an auxiliary roll between stands of the inter-tandem rolling mill. The cold tandem rolling mill shown in FIG. 1 is a cold tandem rolling mill that employs a direct rolling lubricating oil supply system, and the same reference numerals are used for the same parts as the conventional cold tandem rolling mill shown in FIG. The description is omitted.
[0015]
In FIGS. 1 and 2, the auxiliary roll 4 is positioned along the path line of the steel strip 1 above and below the steel strip 1 in order to regulate the vertical position of the pass line of the steel strip 1 that is a metal strip. It is installed at the location. The auxiliary roll 4 that regulates the vertical position of the pass line of the steel strip 1 is between the second and third stands, between the third and fourth stands, between the fourth and fifth stands, and between the fifth and sixth stands. Is also installed in the same position. These auxiliary rolls 4 are rotatably supported at the same peripheral speed as the speed of the steel strip 1 between the stands while being in contact with the steel strip 1 during cold rolling. Reference numeral 7 denotes a nozzle of an auxiliary roll cleaning device installed in an auxiliary roll between the first and second stands. The nozzle 7 is connected to the branch pipe 7A, and the branch pipe 7A sends the rolling lubricant to the steel strip 1. It is connected to the lubricating oil supply pipe 6 so that the rolling lubricating oil can be sprayed as cleaning oil.
[0016]
Here, the reason why the auxiliary roll cleaning device is provided in the auxiliary roll 4 installed between the first and second stands is that the surface roughness of the work roll of the first stand is rougher than other stands, and the reduction rate is also low. Due to the high amount of wear powder of the work roll and the iron powder on the steel strip surface generated by the sliding friction between the work roll of the first stand and the steel strip, the foreign matter on the steel strip surface on the first stand exit side is the auxiliary roll. This is because it tends to deposit on the surface and become smudge. Further, the nozzle 4 of the auxiliary roll cleaning device is provided to face the body length direction portion of the auxiliary roll 4 where foreign matter on the steel strip surface tends to adhere and become smudge. In this case, the spray nozzle 4 is provided to face the roll surface of the trunk length direction portion of the auxiliary roll 4 corresponding to the width direction end of the steel strip 1. In this way, it is preferable to provide an auxiliary roll cleaning device only for the auxiliary roll 4 installed between the stands where foreign matter on the surface of the steel strip adheres and easily becomes smudge, and further, a spray nozzle of the auxiliary roll cleaning device More preferably, 4 is provided opposite to the body length direction portion of the auxiliary roll 4 corresponding to the width direction end of the steel strip that is liable to be smudged due to foreign matter on the surface of the steel strip. The reason for this is that foreign matter adhering to the surface of the metal strip, which is the root cause of indentation defects, can be prevented from accumulating on the surface of the auxiliary roll without greatly changing the lubrication state between the work roll and the metal strip.
[0017]
Further, the reason why it is preferable to provide an auxiliary roll cleaning device that includes a nozzle 4 and a branch pipe 7A connected to the nozzle 4 and is connected to a lubricant supply pipe 6 that feeds the rolling lubricant to the steel strip 1 is provided. When spraying rolling lubricant as cleaning oil, the length of the newly installed pipe can be shortened, and a separate tank for storing rolling lubricant used as cleaning oil, and rolling lubrication as cleaning oil from the tank This is because a pump for sending oil to the nozzle 4 becomes unnecessary. The reason why it is preferable to use rolling lubricant as the cleaning oil is that lubrication between the work roll and the metal strip can be achieved even when the rolling lubricant sprayed from the nozzle 4 toward the surface of the auxiliary roll adheres to the surface of the steel strip. This is because the state is not changed. Here, in FIG. 2, reference numeral 11 denotes a spray range on the steel strip surface of the rolling lubricant sprayed from the nozzle 5, and reference numeral 12 denotes a steel strip of cooling water sprayed from the metal strip cooling nozzle 8. Shows the spray area on the surface.
[0018]
As the cleaning oil used in the auxiliary roll cleaning device of the cold tandem rolling mill according to the present invention, any oil that does not greatly change the lubrication state between the work roll and the metal strip can be used. Moreover, as an auxiliary roll cleaning apparatus of the cold tandem rolling mill according to the present invention, an apparatus that is not connected to the rolling lubricating oil supply system shown in FIG. 1 and includes a cleaning oil tank, a pump, and a cleaning oil supply pipe separately. You can also
[0019]
【Example】
As shown in FIGS. 1 and 2, the present invention is applied to a 6-stand cold tandem rolling mill that cold-rolls steel strips such as tin plate and galvanized plate. In addition, surface defects and indentation defects called heat scratches are observed by visually observing the surface of the cold-rolled steel strip that has been cold-rolled with a cold tandem rolling mill on an inspection line. The presence or absence of surface defects caused by this was investigated.
[0020]
In this cold tandem rolling mill, rolling lubricating oil mainly composed of palm oil and fat is used, and during cold rolling, hot water and rolling lubricating oil are mixed to form an emulsion having a concentration of 5 to 25 vol%, and steel is introduced at the entrance of each stand. It sprayed from the nozzle 5 toward the belt surface. During cold rolling, rolling lubricant was sprayed from the nozzle 7 toward the auxiliary roll 4 at a pressure of 0.2 to 0.8 MPa. The steel strip used in the 6-stand cold tandem rolling mill has a thickness of 1.6 to 3.0 mm and is cold rolled to a thickness of 0.10 to 0.80 mm. The rolling speed is the same as before applying the present invention. did. As a result, since the present invention was applied to the 6-stand cold tandem rolling mill, no indentation defect due to smudge on the surface of the auxiliary roll and metal strip surface defect called heat scratch were recognized, and the present invention was applied. It was possible to cold-roll at the same rolling speed as before. On the other hand, before applying the present invention to a 6-stand cold tandem rolling mill, the primary defect rate of indentation defects due to smudge on the surface of the auxiliary roll was 0.14%. From this, it can be seen that by applying the present invention, it is possible to prevent the occurrence of heat scratches, indentation defects and the like while maintaining the rolling speed, and to manufacture an ultrathin steel strip having a good surface property.
[0021]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it can suppress effectively that a foreign material accumulates as a smudge on the surface of an auxiliary roll, without changing the lubrication state between a work roll and a metal strip. As a result, while maintaining the rolling speed, it is possible to prevent the occurrence of heat scratches, indentation defects, and the like, and it is possible to produce a metal strip with good surface properties.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a cold tandem rolling mill according to an embodiment of the present invention.
FIG. 2 is a layout view of an auxiliary roll cleaning device for the cold tandem rolling mill shown in FIG. 1;
FIG. 3 is a schematic diagram showing a configuration of a conventional cold tandem rolling mill.
FIG. 4 is a plan view showing a position of a surface defect of a metal strip generated due to smudge accumulated on the surface of an auxiliary roll.
[Explanation of symbols]
1 Metal strip (steel strip)
2 Work roll 3 Backup roll 4 Auxiliary roll 5, 7, 8, 9 Nozzle 6 Rolling lubricant supply pipe
7A branch piping
10 Arrow indicating rolling direction
11 Spray range of rolling lubricant sprayed from nozzle 5 on steel strip surface
12 Spray range A on the steel strip surface of the cooling water sprayed from the metal strip cooling nozzle 8 Indentation defect occurrence range B Steel strip width

Claims (2)

A cold tandem rolling mill in which auxiliary rolls are installed at a plurality of locations along a metal strip pass line, wherein at least one of the auxiliary rolls has cleaning oil directed toward the roll surface. And a nozzle of the auxiliary roll cleaning device is provided to face a body length direction portion of the auxiliary roll corresponding to an end in the width direction of the metal strip. A cold tandem rolling mill characterized by that. The auxiliary roll cleaning device includes a nozzle and a branch pipe connected to the nozzle, and the branch pipe is connected to a lubricant supply pipe for sending rolling lubricant, and the rolling lubricant can be sprayed toward the auxiliary roll. The cold tandem rolling mill according to claim 1, wherein the cold tandem rolling mill is provided .

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