JP5807499B2 - Continuous cold rolling method of steel strip - Google Patents

Description

  The present invention relates to a method for continuously cold-rolling a steel strip such as a hot-rolled steel strip, and more particularly to a method for continuously cold-rolling a steel strip using a tandem rolling mill.

  A tandem rolling mill used when continuously rolling a steel strip has a plurality of rolling stands arranged in the longitudinal direction of the steel strip, and a pair of upper and lower rolling rolls (workpieces) provided on each of these rolling stands. It is also configured to roll a steel strip with a roll). When a steel strip is continuously cold rolled using such a tandem rolling mill, if the thickness of the trailing steel strip is different from the preceding steel strip, the thickness of the tandem rolling mill is set to the thickness of the trailing steel strip. It is necessary to change between runs to match.

As a method of changing the sheet thickness of the tandem rolling mill, when the sheet thickness change point reaches the first rolling stand, the roll reduction position of the rolling stand (position where the rolling roll reduces the steel strip) and A method of simultaneously changing the roll rotation speed of a rolling stand located upstream from the first rolling stand is known (see Patent Document 1).
However, with this method, when the plate thickness is changed between runs, the tension between the stands of the steel strip fluctuates greatly, causing the steel strip to break or squeeze, so the plate thickness can be increased without increasing the tension between the stands. In order to change the running distance, there is a problem in that it is necessary to limit the amount of change in the plate thickness. Therefore, a method has been proposed in which the roll reduction position of each rolling stand is sequentially changed before the leading end of the trailing steel strip passes through each rolling stand of the tandem rolling mill (see Patent Document 2).

Japanese Patent Publication No. 48-17145 Japanese Patent Laid-Open No. 60-221109

  However, the roll reduction position of the first rolling stand is changed to the direction in which the roll interval is expanded before the tip of the succeeding steel strip passes through the first rolling stand arranged at the most upstream among the rolling stands of the tandem rolling mill. Then, the taper part 2 as shown in FIG. 6 occurs in the welded part between the preceding steel strip 1a and the following steel strip 1b. For this reason, in the method described in Patent Document 2, although the plate thickness can be changed between runs without limiting the change in the plate thickness, the material of the trailing steel strip is softer than the preceding steel strip or the rear When the plate thickness of the row steel strip is thicker than that of the preceding steel strip or when the plate width of the follower strip is narrower than that of the preceding steel strip, the tapered portion 2 is downstream of the first rolling stand as shown in FIG. Combined with a drop in tension due to material and size changes when passing through a rolling stand, the tension between the steel strip stands significantly lower than expected, and the steel strip breaks or squeezes in the tandem rolling mill. Therefore, there is a problem that continuous cold rolling of the steel strip cannot be performed stably.

  The present invention has been made paying attention to the above-mentioned problems, and when the material of the subsequent steel strip is softer than the preceding steel strip or when the plate thickness of the subsequent steel strip is thicker than the preceding steel strip, or An object of the present invention is to provide a continuous cold rolling method for a steel strip that can stably carry out continuous cold rolling of the steel strip even when the plate width of the subsequent steel strip is narrower than that of the preceding steel strip. .

  In order to achieve the above object, the present invention provides a tandem rolling machine having a plurality of rolling stands in which a steel strip in which the tip of a subsequent steel strip is welded to the tail end of a preceding steel strip is arranged in the longitudinal direction of the steel strip. A method of continuous cold rolling of steel strips that are continuously cold rolled by a machine, wherein each of the rolling stands excluding the most upstream first rolling stand among the plurality of rolling stands is divided into the preceding steel strip and the subsequent steel strip. Before the welded portion passes, the roll reduction position of each rolling stand excluding the first rolling stand is changed in the direction in which the roll interval is increased, and the tip of the subsequent steel strip passes through the first rolling stand. Immediately thereafter, the roll reduction position of the first rolling stand is changed in a direction in which the roll interval is increased.

  According to the present invention, immediately after the leading end of the trailing steel strip passes through the first rolling stand, the roll rolling position of the first rolling stand is changed in a direction in which the roll interval is increased, so that the preceding steel strip and the trailing steel are changed. The taper portion is not generated in the welded portion with the belt, and as a result, when the welded portion between the preceding steel strip and the succeeding steel strip passes through each rolling stand except for the first rolling stand, the tension between the steel strip stands. Therefore, if the material of the trailing steel strip is softer than the preceding steel strip, or if the thickness of the trailing steel strip is thicker than the preceding steel strip, or Even when the steel strip is narrower than the preceding steel strip, continuous cold rolling of the steel strip can be performed stably.

It is a figure which shows an example of the cold rolling equipment used when implementing this invention. It is a flowchart for demonstrating one embodiment of this invention. Immediately after the leading end of the trailing steel strip passes through the first rolling stand of the tandem rolling mill, the roll strip position of the first rolling stand is changed to the direction in which the roll interval is increased, and the preceding steel strip and the trailing steel strip It is a figure which shows a welding part. The figure which shows the tension | tensile_strength change of the steel strip between the 1st rolling stand and the 2nd rolling stand at the time of changing the roll reduction position of a 1st rolling stand immediately after the front-end | tip of a subsequent steel strip passes a 1st rolling stand. It is. It is a figure which shows the success rate of the board thickness change in this invention method and the conventional method. Before the leading end of the trailing steel strip passes through the first rolling stand of the tandem rolling mill, when the roll reduction position of the first rolling stand is changed in the direction in which the roll interval is increased, It is a figure which shows a welding part. The figure which shows the tension | tensile_strength change of the steel strip between the 1st rolling stand and the 2nd rolling stand at the time of changing the roll reduction position of a 1st rolling stand before the front-end | tip of a subsequent steel strip passes a 1st rolling stand. It is.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing an example of a cold rolling facility used when practicing the present invention, and FIG. 2 is a flowchart for explaining an embodiment of the present invention. The cold rolling facility shown in FIG. Pays off the steel strips 1a, 1b, the payoff reels 3a, 3b, the tail end of the preceding steel strip 1a paid out from the payoff reel 3a, and the tip of the succeeding steel strip 1b paid out from the payoff reel 3b. Welding machine 4, tandem rolling machine 6 for rolling steel strips 1 a and 1 b supplied from welding machine 4 through looper 5, and tension for winding steel strips 1 a and 1 b that have passed through tandem rolling mill 6 into a coil shape And a reel 7.

  The tandem rolling mill 6 includes a plurality of (for example, four) rolling stands 8a, 8b, 8c, and 8d arranged in the longitudinal direction of the steel strips 1a and 1b. These rolling stands 8a to 8d are provided with the steel strips 1a and 1b. A pair of upper and lower rolling rolls 9a and 9b to be rolled, a pair of upper and lower backup rolls 10a and 10b to back up the rolling rolls 9a and 9b, and a plurality of backup rolls 10a and 10b and a plurality of rolls disposed between the rolling rolls 9a and 9b. Each has an intermediate roll 11.

  Further, the cold rolling equipment shown in FIG. 1 is output from a through-hole detection device 12 that optically detects a through-hole formed in the vicinity of the welded portion of the steel strips 1a and 1b, and the through-hole detection device 12. And a control device 14 for controlling the rolling stands 8a to 8d of the tandem rolling mill 6 based on the calculation result of the calculation device 13. The control device 14 is configured so that the material of the trailing steel strip 1b is softer than the preceding steel strip 1a, the plate thickness of the trailing steel strip 1b is thicker than the preceding steel strip 1a, or the plate of the trailing steel strip 1b. When the width is narrower than the preceding steel strip 1a, the rolling stands 8a to 8d are controlled according to the flowchart shown in FIG.

That is, when the tip of the succeeding steel strip 1b is welded to the tail end of the preceding steel strip 1a by the welding machine 4 in step S1 shown in FIG. 2, the control device 14 takes in the calculation result of the arithmetic device 13 and welds the steel strip. The position information of the part is acquired (step S2). And the control apparatus 14 position of the steel strip welding part which acquired whether the front-end | tip of the succeeding steel strip 1b reached | attained the 1st rolling stand 8a arrange | positioned most upstream among the rolling stands 8a-8d in step S2. Judgment is made from the information (step S3).
When it is determined that the leading end of the trailing steel strip 1b has reached the first rolling stand 8a, the control device 14 immediately after the leading end of the trailing steel strip 1b passes through the first rolling stand 8a. Is changed in a direction in which the roll interval is increased (step S4).

  If the leading end of the trailing steel strip 1b has passed through the first rolling stand 8a, the control device 14 is configured so that the welded portion between the preceding steel strip 1a and the trailing steel strip 1b is disposed downstream of the first rolling stand 8a. It is judged from the positional information on the steel strip welded part acquired at step S2 whether or not it has reached the vicinity of the two rolling stands 8b (step S5). Here, when it is determined that the welded portion between the preceding steel strip 1a and the succeeding steel strip 1b has reached the vicinity of the second rolling stand 8b, the controller 14 welds the preceding steel strip 1a and the succeeding steel strip 1b. Before passing the second rolling stand 8b, the roll reduction position of the second rolling stand 8b is changed in the direction in which the roll interval is increased (step S6).

  If the welded portion between the preceding steel strip 1a and the succeeding steel strip 1b has passed through the second rolling stand 8b, the controller 14 causes the welded portion between the preceding steel strip 1a and the succeeding steel strip 1b to become the second rolling stand 8b. It is judged from the position information of the steel strip welded part acquired at step S2 whether or not the third rolling stand 8c arranged downstream is reached (step S7). Here, if it judges that the welding part of the preceding steel strip 1a and the succeeding steel strip 1b has arrived near the 3rd rolling stand 8c, the control apparatus 14 will weld the preceding steel strip 1a and the succeeding steel strip 1b. Before passing through the third rolling stand 8c, the roll reduction position of the third rolling stand 8c is changed in the direction in which the roll interval is increased (step S8).

  If the welded portion between the preceding steel strip 1a and the succeeding steel strip 1b has passed through the third rolling stand 8c, the control device 14 determines that the welded portion between the preceding steel strip 1a and the following steel strip 1b is the third rolling stand 8c. It is judged from the position information of the steel strip welded part acquired at step S2 whether or not it has reached the vicinity of the fourth rolling stand 8d arranged downstream (step S9). Here, when it is determined that the welded portion between the preceding steel strip 1a and the succeeding steel strip 1b has reached the vicinity of the fourth rolling stand 8d, the controller 14 welds the preceding steel strip 1a and the following steel strip 1b. Before passing through the fourth rolling stand 8d, the roll reduction position of the fourth rolling stand 8d is changed in the direction in which the roll interval is increased (step S10).

The preceding steel strip 1a and the subsequent steel strip 1b when the roll reduction position of the first rolling stand 8a is changed in the direction in which the roll interval is increased immediately after the leading end of the trailing steel strip 1b passes through the first rolling stand 8a. The welded part is shown in FIG.
When the roll rolling position of the first rolling stand 8a is changed in the direction in which the roll interval is enlarged immediately after the leading end of the trailing steel strip 1b passes through the first rolling stand 8a, the taper portion 2 leads as shown in FIG. It turns out that it does not generate | occur | produce in the welding part of the steel strip 1a and the succeeding steel strip 1b.

Next, immediately after the tip of the trailing steel strip 1b passes through the first rolling stand 8a, the roll rolling position of the first rolling stand 8a is changed between the first rolling stand 8a and the second rolling stand 8b. The change in tension of the steel strip is shown in FIG.
When the roll reduction position of the first rolling stand 8a is changed immediately after the tip of the trailing steel strip 1b passes through the first rolling stand 8a, as shown in FIG. 4, the leading steel strip 1a and the trailing steel strip 1b It can be seen that when the weld passes through the second rolling stand 8b, the tension between the stands of the steel strip is not greatly reduced.

  Therefore, in one Embodiment of this invention mentioned above, immediately after the front-end | tip of the following steel strip 1b passes the 1st rolling stand 8a, changing the roll reduction position of the 1st rolling stand 8a to the direction where a roll space | interval expands. Thus, the taper portion 2 does not occur in the welded portion between the preceding steel strip 1a and the succeeding steel strip 1b, so that the welded portion between the preceding steel strip 1a and the following steel strip 1b is downstream from the first rolling stand 8a. When passing through the rolling stands 8b to 8d, the timing of the tension drop due to the material or size change and the tension drop due to the taper rolling can be made different, and the tension between the stands of the steel strip is prevented from greatly decreasing. Therefore, when the material of the trailing steel strip 1b is softer than the preceding steel strip 1a, or when the plate thickness of the trailing steel strip b is thicker than the preceding steel strip 1a, or the plate of the trailing steel strip 1b The width is the preceding steel strip Strip 1a even narrower than a, a continuous cold rolling 1b can be stably performed.

FIG. 5 is a diagram showing the success rate of changing the running plate thickness in the method of the present invention and the conventional method. As shown in FIG. 5, it can be seen that the method of the present invention has a higher success rate of changing the running plate thickness than the conventional method, and as is clear from this, the method of the present invention has the following steel strip. Even if the material is softer than the preceding steel strip, the thickness of the trailing steel strip is thicker than the preceding steel strip, or the plate width of the trailing steel strip is narrower than the preceding steel strip, the steel strip is continuously cold. Rolling can be performed stably.
In the above-described embodiment of the present invention, the tandem rolling mill has four rolling stands, but the number of rolling stands is not limited to four, for example, two to three. It may be 5 or more.

Moreover, although the thing which has an intermediate | middle roll between a rolling roll and a back roll was illustrated as a rolling stand of a tandem rolling mill, you may use what the intermediate roll is not arrange | positioned between a rolling roll and a back roll. .
Also, it is possible to incorporate a model that calculates the amount of decrease in tension due to the width drop of the notch near the rolling schedule change point from the width drop length, and calculates the increase in reduction reduction from the mill constant for that amount of tension drop. .

DESCRIPTION OF SYMBOLS 1a ... Leading steel strip 1b ... Subsequent steel strip 2 ... Tapered part 3a, 3b ... Payoff reel 4 ... Welding machine 5 ... Looper 6 ... Tandem rolling mill 7 ... Tension reel 8a ... 1st rolling stand 8b ... 2nd rolling stand 8c 3rd rolling stand 8d 4th rolling stand 9a, 9b Rolling rolls 10a, 10b Backup roll 11 Intermediate roll 12 Through-hole detection device 13 Arithmetic device 14 Control device

Claims (1)

A steel strip in which the tip of a subsequent steel strip is welded to the tail end of a preceding steel strip is continuously cold-rolled by a tandem rolling mill having a plurality of rolling stands arranged in the longitudinal direction of the steel strip. A continuous cold rolling method,
The rolls of the respective rolling stands excluding the first rolling stand before the welded portion between the preceding steel strip and the succeeding steel strip passes through the rolling stands other than the first upstream upstream rolling stand among the plurality of rolling stands. The rolling reduction position is changed in the direction in which the roll interval is increased, and immediately after the tip of the succeeding steel strip passes through the first rolling stand, the roll reduction position in the first rolling stand is changed in the direction in which the roll interval is increased. A method for continuous cold rolling of steel strips.

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