JPH0465721B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for straightening edge drops of a metal strip produced by rolling by bending and tensioning.

(Prior Art) There is non-uniformity in the thickness distribution in the width direction of a metal strip manufactured by rolling, and the thickness tends to decrease rapidly especially near the edge, 10 to 50 mm from the edge. Such a rapid decrease in the thickness of the edge portion is called an edge drop, and the reduced portion is called an edge drop portion. Rolling technology continues to be developed to improve this edge drop.

On the other hand, as a method for improving edge drop, which is different from rolling, the present inventors have found that when a large plastic elongation is applied by bending and tension by passing a metal strip through a tension leveler while applying tension, the opposite effect of edge drop occurs near the edge. He discovered that an edge drop phenomenon occurs, in which the plate thickness near the edge is relatively thicker than other parts, and developed an edge drop correction method that applied this phenomenon in Japanese Patent Application Laid-open No.
No. 59-4924.

The characteristic of this phenomenon is that the amount of edge up increases as the elongation rate increases. Subsequent research by the present inventors revealed that the range of the edge up, that is, the distance in the width direction from the edge to the point where the edge up begins, increases as the roll pitch of the tension leveler used for bending and tension increases.
In addition, it has become clear that the size of the edge up range within a practical roll pitch range is about 15 to 40 times the plate thickness.

(Problem to be Solved by the Invention) By the way, if the range of the edge drop and the range of the edge drop match, the edge drop can be reduced by applying a predetermined plastic elongation by bending and tension, as shown in the above-mentioned patent publication. Although it can be straightened uniformly, if the plate thickness is thin like a cold-rolled steel plate, the edge up range will be smaller and it will not be possible to straighten uniformly. The reason for this is that the range of edge drop due to rolling has little to do with plate thickness and is determined mostly by the rolling roll diameter.
This is because the range of the edge up is about 40 times the board thickness or less, and the thinner the board, the smaller the range.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for correcting edge drops even in thin plates by bending and tensioning.

Another object of the present invention is to provide a method for correcting edge drops in metal strips having a thickness of 3 mm or less, where the range of edge drops is significantly different from the range of edge drops that occur when bending and tension is applied. It is to provide.

(Means for Solving the Problems) In order to solve the above problems, the present invention involves trimming a small amount near the edge of a metal strip manufactured by rolling, and then trimming the edge by a predetermined amount corresponding to the edge drop amount after trimming. This is a method for straightening edge drops of a metal strip, which is characterized by applying plastic elongation to the metal strip by bending and tensioning.

Here, the metal strip may be either a hot-rolled plate or a cold-rolled plate, and the plate thickness is not limited, but the present invention is particularly effective when the metal strip is 3 mm.
It is below that level.

(Function) As described above, according to the present invention, by trimming a small amount near the edge of the metal strip after rolling so that the range of the remaining edge drop becomes the same as the range of the edge up, the edge drop after trimming can be reduced. can be uniformly straightened by edge-up by bending and tension. Furthermore, since the amount of trimming is small, the yield is also improved.

The amount of trimming is not particularly limited and can be set as appropriate, but it must be as small as possible to prevent a decrease in yield, and at the same time, it must be sufficient to correct edge drops due to the amount of edge drop due to bending and tension processing. Furthermore, the specific aspects of trimming and bending/pulling are already well known to those skilled in the art, and will not be further discussed below in order to simplify the explanation.

Next, the present invention will be specifically explained using an example of an electromagnetic steel sheet to which the present invention is very effective.

Most electromagnetic steel sheets used for motors, transformers, etc. are approximately 0.5 mm thick, but the thickness accuracy is extremely strict, and the thickness deviation in the width direction is 0.005 mm.
(5μm) or less is required in some cases. On the other hand, the edge drop caused by cold rolling usually has an edge drop amount (thickness deviation) of about 0.04 mm (40 μm), and the edge drop range is nearly 40 mm, so in the end, each side is trimmed by about 40 mm and is called scrap. Become. For this reason, the yield is very poor, which is a big problem.

Even if you try to correct this edge drop (range 40 mm) by bending and tensioning the edge drop, the edge drop range is 4 times the plate thickness of 0.5 mm, that is, 20 mm.
This is the practical limit.

This relationship is as shown in FIG. Figure 1 shows the edge drop amount (represented by curve A) of a cold-rolled electrical steel sheet with a thickness of 0.50 mm, and the edge drop amount when it is subjected to bending and tensile processing with an elongation of 6% and 16%. This is a graph showing the added plate thickness changes (represented by curves B and C, respectively) versus the distance from the edge. As shown in FIG. 1, the plate thickness distribution after straightening becomes distorted, and a uniform plate thickness distribution cannot be obtained. In addition, curve C in Figure 1
The elongation rate required to almost straighten an edge drop of 0.04 mm is quite large at 16%, and large-scale equipment is required because the number of rolls and tension must be increased.

On the other hand, even in the above case, if the edge of the electrical steel sheet after cold rolling is trimmed by 15 mm on one side according to the present invention, the remaining edge drop range will be
It will be 25mm. This relationship is as shown in Figure 2. When trimming 15 mm on each side (the plate thickness change is shown by curve D), the edge drop range becomes 25 mm, and when bending and tensioning with an elongation of 6% is added to this, the edge drop range is 25 mm. , the thickness change becomes almost uniform as shown by curve E in the figure. As described above, according to the present invention, as shown in FIG. 2, almost uniform correction is achieved by the edge tap in the range of 20 mm. In this way, if the range of the edge drop is slightly larger than the range of the edge up, correction can be made sufficiently uniform in practice, and the amount of trimming can be reduced, resulting in an improvement in yield.

That is, according to the present invention, even if the conventional trimming amount of 40 mm on one side is reduced to 15 mm, a uniform plate thickness is obtained, and the yield is greatly improved.

Furthermore, since the remaining edge drop amount has been reduced to 0.015 mm (15 μm) by trimming 15 mm, the elongation rate for bending and tensile processing only needs to be 6%, which means that the number of rolls and tension is small compared to the case of 16% described above. It can be corrected with inexpensive equipment.

As already mentioned, the amount of trimming is not particularly limited in the present invention, but a general explanation of how to determine the amount of trimming is as follows.

First, due to equipment constraints (tension, number of leveler rolls, roll diameter, roll pitch, etc.), the edge up range for each plate thickness (15 to 40
The upper limit of the amount of trimming (times) and the amount of edge up is determined, but consider reducing the amount of trimming as much as possible within that range. For this reason, it is preferable to allow a sheet thickness distribution in which edge drops remain to a degree that does not cause any practical problems, and to set this as the target value. There are four cases as shown below, including the case where no trimming is required. In the following, the edge drop range is assumed to be l, and the edge drop amount is assumed to be e.

If l and e are both small (l is smaller than the edge up range and e is smaller than the edge up amount), it can be corrected as is, and no trimming is necessary.

If l is large and e is small, trim so that l is approximately the range of the edge up. However, if some residual amount is allowed, the amount of trimming can be reduced further.

If l is small but e is large, trim so that e is approximately the edge up amount. However, if some residual amount is allowed,
The amount of trimming can be reduced further.

When both l and e are large, trimming is performed so as to satisfy both the range of e≦edge up and e≦edge up amount. However, if some residual amount is allowed, the amount of trimming can be reduced further.

Based on the above ideas, equipment specifications, plate thickness,
Determine the optimal amount of trimming depending on the edge drop situation, etc.

Note that the edge up amount can be increased by passing the leveler a plurality of times, so when reversing or repassing the plate, there is no restriction on e and only l needs to be considered.

(Effects of the Invention) As explained above, according to the present invention, edge drops can be uniformly corrected even in thin objects, and can be corrected by bending and tensioning with a small elongation rate. It's advantageous.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the state of edge drop correction (changes in thickness distribution near edges) by the conventional method; and FIG. 2 is a graph showing the state of edge drop correction (changes in thickness distribution near edges) according to the present invention. This is a graph showing.

Claims (1)

[Claims] 1. A method for straightening edge drops in a metal strip, which comprises trimming a part of the edge drop portion of the metal strip after rolling, and then subjecting the metal strip to bending and tensioning.