JP2000225404A - Method for preventing indentation flaw on lower work roll in dry skinpass rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a preventing method for the indentation flaws on the lower work roll in dry skinpass rolling by which the generation of the indentation flaws on the lower work roll due to foreign mater stuck to the lower back-up roll when the work rolls of a dry skinpass rolling mill are changed is prevented efficiently and effectively. SOLUTION: At the time of changing the rolls of a dry skinpass rolling mill of a type in which at least lower back-up roll is driven, after incorporating the work rolls 1 and before executing reduction of the mill, the lower back-up roll 2B is rotated at the revolving speed N of >=20 rpm for >=10/(N-10) min. And/or that roll is rotated >=1 revolutions while abutting a sucking blade 3 on the surface of the roll.

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 lower work roll indentation in dry temper rolling of cold rolled steel sheet for tinplate and tin-free steel (TFS).

[0002]

2. Description of the Related Art Generally, in temper rolling of a tinplate original material mainly composed of a bright material, dry temper rolling is performed because gloss needs to be obtained after continuous annealing. The work rolls of the mill (skin pass mill) used for this rolling were changed in the following order: extracting the old work rolls, incorporating the new work rolls, and tightening the mill by rolling down. Often enter. The main reason is that foreign matter falls on the lower backup roll during work roll change, and this foreign matter is embedded in the backup roll with low surface hardness due to the contact and rotation of the lower work roll and lower backup roll. Roll 1
Indenting the lower work roll with each rotation. These indentation flaws are transferred to the rolled material and cause surface defects called roll marks. In the case of wet temper rolling, foreign substances are washed away by a tempering liquid sprayed on a steel plate or a roll, so that the above-mentioned flaws hardly occur.

The foreign matter once embedded in the backup roll hardly falls off spontaneously, and the same roll mark is generated again just by replacing the work roll. For this reason, conventionally, an operator enters the mill or pulls out the lower backup roll from the mill,
It is necessary to remove foreign matter, and there have been problems on safety and a decrease in the operation rate.

As means for solving this problem, Japanese Patent No.
Japanese Patent No. 2738632 proposes that when a work roll is replaced, the lower backup roll is rotated half a turn (180 ° rotation) after the work roll is incorporated and before the mill is screwed down.
As a result, an attempt is made to drop the foreign matter on the lower backup roll. In the case where the foreign matter has oil and sticks to the roll surface, the foreign matter is rotated halfway while being wiped by a scraper blade.

[0005]

However, there are many cases where foreign matter remains on the roll surface even if the lower backup roll is rotated half a turn according to the above proposal. Further, even if the foreign matter is once separated from the roll surface by wiping with the scraper blade, the foreign material remaining on the scraper blade may adhere to the roll surface again. In addition, when the scraper blade is disposed so as to contact the lower half of the lower backup roll, a roll outer peripheral portion that does not reach the scraper blade by a half turn is formed. For this reason, in the related art, it is not possible to completely prevent the lower work roll indentation flaws without any care by the operator.

The present invention has been made in view of the above-mentioned problems of the prior art, and has been made in consideration of the above-mentioned problems of the prior art. It is an object of the present invention to provide a method of preventing lower work roll indentation flaws in temper rolling.

[0007]

According to a first aspect of the present invention, at least when a roll of a dry temper rolling mill of a type that drives a lower backup roll is replaced with a lower backup roll after a work roll is incorporated and before the mill is screwed down. This is a method for preventing lower work roll indentation in dry temper rolling, wherein the roll is rotated at a rotation speed N of 20 rpm or more for 10 / (N-10) minutes or more.

According to a second aspect of the present invention, at least when a roll of a dry temper rolling mill of a type for driving a backup roll is changed, the lower backup roll is suctioned to the roll surface after the work roll is incorporated and before the mill is pressed down. This is a method for preventing lower work roll indentation flaws in dry temper rolling, wherein the blade is rotated at least one rotation while being in contact with the blade.

In a third aspect of the present invention, when a roll of a dry pass temper rolling mill for driving at least a lower backup roll is changed, the lower backup roll is placed on the roll surface after the work roll is incorporated and before the mill is pressed down. A lower work roll indentation prevention method in dry temper rolling, wherein the suction blade is rotated at a rotation speed N of 20 rpm or more for 10 / (N-10) minutes or more while being in contact with the suction blade.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the first invention, the lower backup roll is rotated at a rotation speed N of 20 rpm or more for 10 / (N-10) minutes or more after the work roll is incorporated and before the mill is screwed down. As a result, a centrifugal force of a certain magnitude or more is applied to the foreign matter that has adhered to the lower backup roll, particularly to a foreign matter that has a strong adhesive force and cannot easily be dropped only by the action of gravity. Can be separated from the roll surface.

FIG. 2 shows an example of an experimental result on which the first invention is based. This is because the lower backup roll is rotated by changing the rotation speed N and the rotation time τ after the work roll is incorporated and before the mill is screwed down, and the relationship between N, τ and the roll mark generation rate Z of the temper rolled product is investigated. From FIG. 2, it can be seen from FIG. 2 that when Z is rotated at N = 20 rpm for τ = 1 minute or more and then temper rolling is performed, Z becomes approximately 0%. Further, as N increases, the lower limit of τ until the roll mark disappears decreases. For example, at N = 30 rpm, Z is almost 0% after τ = 30 seconds or more
Becomes In order to organize this data and to make the foreign matter hardly remain on the lower backup roll, the lower backup roll is rotated at a rotation speed N: 20 rpm or more and the rotation time τ: 10 / (N-1
0) I found that it was necessary to rotate for more than a minute.

In the second invention, the lower backup roll is rotated one or more rotations while the suction blade is in contact with the roll surface after the work roll is incorporated and before the mill is pressed down.
Since the suction blade is used instead of the conventional scraper blade, the foreign matter wiped by the blade is sucked and carried away without staying in the blade. Therefore, the wiped foreign matter does not adhere to the roll surface again. In addition, since the rotation is set to one rotation or more instead of the conventional half rotation, the entire outer periphery of the roll can reach the suction blade regardless of the arrangement position of the suction blade. The suction blade may be configured such that the blade has a built-in suction path having the blade tip as a suction port. The suction blade may have a knife-like tip or a brush-like tip.

In the third aspect of the present invention, after the work roll is incorporated and before the mill is pressed down by the mill, the lower backup roll is brought into contact with the roll surface with a suction blade at a rotation speed N: 20 rpm or more.
Rotate for more than / (N-10) minutes. This is the first invention and the second invention
According to the present invention, the wiping / suctioning action is superimposed on the peeling action by gravity and centrifugal force, and the first and second inventions also hardly remove foreign matter which has adhered so strongly that they cannot be removed alone. Can be completely removed.

[0014]

FIG. 1 is a schematic side view of a dry skin pass mill embodying the present invention, wherein S is a rolled material, 1 is a work roll (1A is above, 1B is below), 2 is a backup roll (2A is above). , 2B are lower) and 3 is a suction blade that comes into contact with the lower backup roll 2B, and a brush 4 is provided at a suction port at the tip. The roll mark generation rate of the tinplate after temper rolling was compared with the comparative example in which the work rolls were changed under conditions outside the present invention for the examples in which the present invention was applied to the work roll changing work of the mill. Of the work roll change work variables of the working example and the comparative example, the number of rotations N and the rotation time τ of the lower backup roll according to the present invention, and whether the suction blade is used or not used are shown in association with the roll mark occurrence rate Z. It is shown in FIG.

[0015]

[Table 1]

According to Table 1, the roll mark generation rate was 0.4% in the comparative example, but in Example 1 (corresponding to the first invention).
It was 0.02% in Example 2 (corresponding to the second invention) and 0.03% in Example 3 (corresponding to the third invention), and the effect of preventing lower work roll indentation by the present invention was confirmed.

[0017]

As described above, according to the present invention, it is possible to efficiently and effectively prevent lower work roll indentation flaws caused by foreign matter adhering to the lower backup roll when changing the work roll of a dry skin pass mill. This eliminates the need for foreign matter removal work, thereby eliminating the problem of safety, and at the same time, has an excellent effect of increasing the mill operation rate and improving productivity.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a skin pass mill embodying the present invention.

FIG. 2 shows the rotation speed N and rotation time τ of the lower backup roll.
6 is a graph showing the relationship between the roll mark occurrence rate Z of a temper rolled product and a temper rolled product.

[Explanation of symbols]

 Reference Signs List 1 work roll 2 backup roll 3 suction blade 4 brush

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tadaaki Octagon 1 Kawasaki-cho, Chuo-ku, Chiba Kawasaki Steel Corporation Chiba Works

Claims (3)

[Claims] When the roll of a dry temper rolling mill of at least the type that drives the lower backup roll is changed, the lower backup roll is rotated at a rotation speed N: 20 rpm or more at 10 / ( N-10) A method for preventing lower work roll indentation in dry temper rolling, wherein the method is rotated for at least 10 minutes. 2. The method according to claim 1, wherein the lower back-up roll is brought into contact with a roll surface of the lower back-up roll on a roll surface of the dry-pass temper rolling mill at least after the work roll is inserted and before the mill is screwed down. A method for preventing lower work roll indentation in dry temper rolling, wherein the lower work roll is rotated one or more times. 3. At least when a roll of a dry temper rolling mill for driving a lower backup roll is driven, a suction blade is brought into contact with a roll surface of the lower backup roll after the work roll is inserted and before the mill is pressed down. A method for preventing indentation of lower work roll in dry temper rolling, wherein the number of rotations is at least 20 rpm for 10 / (N-10) minutes or more.