JPH04200904A - Cold rolling method of strip metal - Google Patents

Abstract

PURPOSE:To enable preventing the break of sheet by scarifying the shape of sheet in the part where edge crack is generated by adjusting the target shape of downstream or upstream stand from that stand when the length of edge crack longer than a prescribed value is detected. CONSTITUTION:At the time of cold rolling a strip metal with a cold rolling mill which is provided with plural rolling stands, the length of edge crack and shape in the width direction in the end parts of sheet are detected on at least the outlet side 2 of a 1st rolling stand. When the length of edge crack is longer than the reference value, the break of sheet due to the development of edge crack can be prevented by controlling tension that is applied to the end parts of sheet by rolling the shape on the outlet side of the rolling stand on the downstream side or upstream side from that stand into the shape of edge wave.

Description

[Detailed Description of the Invention] 11+ Industrial Application Field The present invention relates to a method for cold rolling a metal strip, and more specifically, rolling is carried out into an elongated shape depending on the state of occurrence of edge cracks, and the plate breaks during rolling. It relates to a method of preventing this.

BACKGROUND ART Generally, in a tandem mill, the shape of the plates between the stands is set using a shape control actuator, such as a bender, so as to have a flange of 1 to 1. This is because constriction is likely to occur if the shape is extremely elongated at the edges or at the belly.

Further, in cold rolling, the hot coil is cold rolled as it is, but the plate ends are I-rimmed and then cold rolled.

However, when cold rolling is performed in this manner, edge cracks occur at the edge of the plate due to microcracks existing at the edge of the plate of the hot coil and work hardening during trimming, and if the edge crack becomes large, the plate breaks. However, it is almost impossible to predict such edge cracks before rolling, and plate breakage may reduce the operating rate of the equipment by 10% or more.

From this point on, Tokukai Showa 5! As described in IJ-33006, a method in which the length of an edge crack is detected on the downstream side of a rolling mill stand where the 1-tal rolling reduction exceeds 60%, and low-tension rolling is performed according to its appearance. is proposed.

However, this rolling method is a method in which the shape of the plate is set to 1~ on the exit side of the rolling mill stand, and with this method, the tension distribution in the width direction becomes almost uniform, resulting in sharp edge cracks. In some cases, crack propagation cannot be prevented. Furthermore, since the tension distribution in the width direction is not taken into consideration, in the case of a flattened shape, tension is concentrated at the edge of the plate, and even if the total eye strength is reduced, it is not possible to prevent the development of ear cracks.

Invention 1f Problem to be Solved The present invention detects the edge crack length at the end of the metal strip at each rolling stand or at least on the exit side of the first rolling stand, and when an edge crack length exceeding a predetermined value is detected. , a cold rolling method that can ensure overall high rolling efficiency by adjusting the target shape of the rolling stand downstream or upstream and sacrificing the shape of the plate where edge cracks occur to prevent plate breakage. provide.

If it is a means to solve the problem, it will act on the O. In the conventional method, the tension distribution in the width direction of the plate is not taken into consideration, whereas the method of the present invention can be applied to a cold rolling mill having a plurality of rolling mill stands. When cold rolling a metal strip, the edge crack length and the shape in the width direction of the plate edge are detected on the exit side of the first rolling stand, and the edge crack length is the Ml value, that is, If the standard re-crack length is better than the standard re-crack length set according to the rolling conditions, the shape of the exit side of the rolling stand on the downstream or upstream side is rolled into an H-stretched shape to reduce the tension applied to the plate end. This is a method to prevent plate breakage due to the development of edge cracks.

However, in the method of the present invention, for example, the length of the edge crack is detected at the exit side of the first rolling stand in a 4-high or 6-high rolling stand, and based on this result, the shape of the work roll bender etc. is determined. Using a control means, the shape of the edge of the metal strip on the exit side of the rolling stand is controlled to an edge elongation shape that is higher than the H elongation shape steepness limit value that prevents the growth of edge cracks, thereby avoiding tension concentration at the edge of the plate and preventing edge cracks. Furthermore, the shape detector detects the aperture that occurs when the plate shape is made to have an edge, and this shape measurement signal is fed back to prevent the aperture.

EXAMPLE The method of the present invention will be explained in more detail through an example of cold rolling a steel strip in a tandem mill consisting of five stands.

First, Figure 1 is a graph that does not show the ratio of unit tension between rolling mill stands to the deformation resistance of the material, that is, the relationship between the tension level and the incidence of plate breakage, in this case 1.
The barrel reduction ratio was 80.2%, and the fracture occurrence rate was #4 to 5 stands. In Figure 1, there is no clear correlation between the fracture occurrence rate and tension, but at tension level 1 in Figure 1,
The relationship between decline and fracture occurrence rate of the #4 stand work roll bender is shown in Figure 2.Increasing the decline bender load means that the plate shape is in an elongated shape. As is clear from Figure 2, when the decrease bender is set to 201 hens or less, the incidence of fracture decreases.The inventors further researched this phenomenon and found that the The relationship between the freeze bender and the steepness of the 4Qmm portion of the plate edge is as shown in Figure 3.As shown in Figure 3, the steepness of the plate edge increases with the decrease in the decrease bender, and as shown in Figure 2. The steepness of the plate edge exceeds 0.5% for day freeze benders of 20 tons or less, where the incidence of breakage is reduced.

Therefore, as shown in Fig. 4, for example, in a 5-bus continuous rolling mill, the plate shape at the exit side of each rolling mill stand is maintained at a steepness of 0.8%, and a case where the steepness at the root end is maintained at 0.2%.
When compared, the degree of development of the depth of the ear crack was found to be greater when the sharp V1 degree at the plate edge was set to 0.8% than when it was set to 0.2%. It was found that there were few

In short, from the above, if the shape of the root end on the exit side of the rolling mill stand is set to a value equal to or higher than the edge elongation shape steepness limit value that prevents the development of edge cracks, the development of edge cracks can be minimized. Breakage can be prevented.

This limit value can be determined experimentally based on the rolling stand, material to be rolled, plate thickness, rolling conditions, etc. In the case of copper strips, the content is selected in the range of 0.1 to .1.0% depending on the steel type.

Additionally, as shown in Figure 5, most of the edge cracks occur in the first stand, regardless of the total reduction rate, and become deeper downstream from the second stand onwards, so edge cracks can be detected. This purpose is not necessarily carried out on the exit side of each rolling mill stand, but the purpose can be achieved even if it is installed only on the exit side of at least the first rolling mill stand. Further, the method of the present invention can be easily carried out using, for example, a four-high rolling mill shown in FIG.

First, FIG. 6 is a layout diagram of an example of an apparatus for implementing the method of the present invention, and this continuous rolling mill is equipped with five rolling mill stands, and a work roll pentameter 8 is provided corresponding to each of these rolling mill stands. .9.10.11.12 is installed. In this rolling equipment, the edge crack length detection device 1 is installed on the exit side of the #1 rolling mill stand where the incidence of edge cracks is highest, and The edge crack length is detected and it is examined whether this length is equal to or greater than the reference length.A shape detection device 2.3.4.5.6 is installed on the exit side of each rolling mill stand. , this measured shape signal is sent to the shape controller 7
sent to. In order to match the shape signal at the shape controller roller 7 with the target shape determined according to the rolling conditions,
Feedback signal to work roll vendor 8.9.10
, sent on 11.12. In addition, the code 13.14.15.1
6.17 is the work roll of the rolling mill stand, 19.20
indicate payoff reel and tension reel, respectively.

When rolling in a rolling machine with this configuration, usually
The target shape of the exit side of each rolling mill stand is set on the stand as shown in FIG. Roll it. However, when the edge crack length detector 1 detects an edge crack that exceeds a standard value determined by the rolling conditions etc. on the exit side of the #1 rolling mill stand, the edge crack length detector 1 detects an edge crack that is larger than the standard value determined by the rolling conditions, etc. The seventh
Benders #2 to #5 rolling mill stand 9.10.
11.12 is feedback controlled. At the same time, the target shape of the #1 rolling mill stand was changed to the shape of the #1 rolling mill stand with the edge elongated as shown in Fig. 7(b) until the rolling of the coil with the edge cracking was completed. vendor 2
feedback control. In this way, it is possible to prevent the plate from breaking due to the development of edge cracks, and also to prevent the occurrence of edge cracks.

That is, as shown in FIG. 8, if the shape of the exit side of the rolling mill stand is always flat (a), and if the shape of the exit side of the rolling mill stand is always an H-elongated shape (b), the method of the present invention Comparing case (d), plate breakage is only the same as when the exit side of the rolling mill stand is always extended, but the reduction in operating efficiency due to throttling is significantly reduced, resulting in an overall high rolling efficiency. is obtained.

<Effects of the Invention> As explained in detail above, the method of the present invention detects small (■) cracks on the exit side of the first rolling mill stand of a continuous rolling mill, and detects cracks when the H cracks reach a standard value or higher. Next, rolling is performed while controlling the target shape of the exit side of each rolling mill stand to be an elongated shape.

Therefore, the incidence of breakage is kept to a minimum, and
Decrease in operating efficiency due to throttling is reduced.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between tension between rolling mill stands and fracture occurrence rate, Figure 2 is a graph showing the effect of reducing root end tension by changing the work roll bender, and Figure 3 is a graph showing the effect of reducing the root end tension by changing the work roll bender. Figure 4, a graph showing the change in the steepness of the plate edge by changing the plate edge, shows that the degree of expansion of the depth of the edge crack on the exit side of the rolling stand can be reduced by increasing the steepness of the plate edge. Graph, FIG. 5 is a graph showing the number of ear cracks that occur for each bus, FIG. 6 is a layout diagram of an example of a device for implementing the present invention, and FIGS. Each explanatory diagram of an example of the target plate shape in the method, FIG. 8, is a graph showing the relationship between the target shape between rolling mill stands and the down time. Code 1...Ear crack depth detector 2...#1 Rolling machine stand outlet shape detector 3.
...#2 Rolling mill stand outlet shape detector 4...
...#3 Rolling mill stand outlet shape detector 5...
・#4 Rolling mill stand outlet shape detector 6...#
5 Rolling mill stand outlet shape detector 7...Bender controller 1 Roller 8...#1 Rolling mill stand Work roll bender cylinder 9...#2 Rolling machine Stand work roll bender cylinder 10...#3 Rolling machine stand work roll bender cylinder 11...#4 Rolling machine stand work roll bender cylinder 12...#5 Rolling machine stand work Roll bender cylinder 13...#1 Rolling mill stand work roll 14
...#2 rolling mill stand work roll 15...
... #3 rolling mill stand work roll 16 ...
...#4 Rolling mill stand work roll 17...
#5 Rolling machine stand Work roll 18...Ear crack depth detector controller 19...Payoff reel 20...Tension reel ￥-$1'l shelf ＃＊“Wealth/Imari) 1j-time 1gki-41 愼Fig. 7 υ Bi Medium length Fig. 8

Claims (1)

[Claims] 1) In continuous rolling in which a metal strip is cold rolled in a cold rolling mill equipped with a plurality of width direction shape control means, at least the first
The length of the edge crack at the end of the metal strip is detected at the exit side of the rolling stand, and the steepness of the edge of the metal strip is detected at the exit side of the rolling stand downstream of the rolling stand where the edge crack exceeding a predetermined value is detected. A method for cold rolling a metal strip, characterized in that the cross-sectional shape in the width direction is controlled so that the edge elongation shape exceeds a limit value that prevents the growth of edge cracks. 2) At the exit side of the rolling stand upstream of the rolling stand where an edge crack of a predetermined value or more is detected, the steepness of the edge of the metal strip is such that the edge elongates to a shape that is more than a limit value at which an edge crack does not grow. , a method for cold rolling a metal strip, characterized by controlling the cross-sectional shape in the width direction.