JP2684152B2 - Metal strip thickness control method for reciprocating mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate thickness control method for metal strips such as steel strips in reciprocating rolling mills.

[0002]

2. Description of the Related Art Generally, when a metal strip such as a steel strip is rolled in a reciprocating rolling mill, the total reduction ratio from the base plate thickness (plate thickness before rolling) to the finished thickness (plate thickness after rolling) is determined. Rolling is performed for the number of rolling passes. At that time, in order to accurately roll to the target finished thickness, automatic plate thickness control (hereinafter referred to as AG
(Also referred to as C) is usually performed.

FIG. 2 is a block diagram of automatic plate thickness control using a 12-high cluster rolling mill for steel strip as an example. S is a steel strip, 1 is a roll stand, 11 is a work roll, 12 is an intermediate roll, and 13 is Backup roll, 14 load cell, 15 hydraulic pressure reduction device,
2a and 2b are plate thickness gauges, 3 is a deflector roll, 4 is a tension reel, 51 is an FB-AGC, 52 is an FF-AGC, and 53 is a hydraulic pressure reduction control device.

In this figure, assuming that the steel strip S is rolled from right to left, the strip thickness of the strip S before this pass rolling measured by the X-ray strip thickness gauge 2a on the right side, that is, the entrance side, A feed-forward automatic plate thickness control (FF-AGC) 52 that gives a deviation position command to the hydraulic pressure reduction control device 53 to obtain a deviation from the input side set plate thickness and cancels the deviation and an X-ray plate thickness gauge on the left side, that is, the output side A feedback automatic plate which gives a hydraulic pressure reduction control device 53 a reduction position command for obtaining the deviation between the thickness of the steel strip S after this pass rolling measured in 2b and the output side setting thickness and making it zero A thickness control (FB-AGC) 51 (also called a monitor AGC) is used.

[0005] After the start of rolling in each pass, when the rolling speed rises above a certain value, the AGC starts control, and when the rolling speed falls below a certain value, the control of the AGC is stopped. Further, in the configuration of FIG. 2, the function of correcting the plate thickness is based on the pressure reduction position control by the hydraulic pressure reduction device 15.
There is also a method of controlling the plate thickness by combining this with the rolling tension by the tension reel 4, and various AGCs are known depending on the combination of the rolling position and the rolling tension.

However, when the strip thickness accuracy of the entry side steel strip is not good, the AGC operates to correct the strip thickness deviation and the rolling position changes greatly, and the rolling load detected by the load cell 14 accordingly. Also changes greatly. When the rolling load changes, the deflection of the rolling roll changes, and the shape of the steel strip changes with the thickness of the steel strip. Therefore, in a normal rolling mill, a shape control function such as a roll bender is added to correct this shape change. However, there is a large variation in the thickness of the steel strip on the inlet side, and a large change in hardness,
If the rolling load fluctuates with a sharp steel plate shape change that cannot be corrected by shape control, or if the rolling load change exceeds the shape control range, the shape of the steel strip deteriorates and operation troubles such as narrowing occur. there's a possibility that.

In particular, in the rolling of the first pass, in which the variation of the plate thickness generated up to the previous process must be corrected in principle, the variation of the load due to AGC is larger than that in the second and subsequent passes. Further, in the first pass, the rolling tension on the entry side cannot be made too high. This is because if the coil is rewound with a tension higher than the winding tension in the previous step, the coil will be tightened and the surface of the steel plate will be rubbed to cause a crimp flaw. Therefore, if rolling is unavoidably performed with a low tension, problems such as narrowing down tend to occur when the shape of the steel strip deteriorates.

FIG. 3 shows an example of a conventional plate thickness control method. In this figure, the horizontal axis is the elapsed time after the start of rolling, and the vertical axis is from the top (a) entrance side plate thickness, (b) exit side plate thickness, (c) AGC on / off, (d) rolling load, (e) The operation state of the roll bender and (f) the shape of the steel strip are shown. After the time t _{0 has} elapsed after starting the rolling with the AGC turned on, the inlet side plate thickness has increased as shown in (a), so this is corrected by the operation of the AGC to keep the outlet side plate thickness at the target value. As shown in (d), the rolling load during this period is increasing. As shown in (e), the roll bender acts to prevent the shape of the steel strip from becoming elongated when the rolling load increases, but after the time t ₃ when the roll bender reaches the limit,
As shown in (f), the edge of the steel strip begins to grow without being restrained, and in extreme cases, narrowing of the plate occurs and time t ₄
Rolling is interrupted by.

As described above, since troubles such as narrowing are likely to occur in the first pass rolling, depending on the kind of rolled material, AGC is not used in the first pass, and AGC is turned on in the second and subsequent passes. It is rather common practice to control the strip thickness by rolling, and the rolling speed could not be sufficiently increased not only in the first pass but also in the second pass, which markedly hindered productivity.

[0010]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and uses a stable AGC from the first pass in a reciprocating rolling mill in which problems such as narrowing due to deterioration of shape are likely to occur. The purpose of the present invention is to provide a technique capable of rolling by rolling.

[0011]

A method for controlling the strip thickness of a metal strip in a reciprocating rolling mill according to claims 1 and 2 of the present invention is based on the rolling load when automatic strip thickness control is started. If the upper limit and the lower limit are set, and during each pass rolling, if the rolling load is between the upper limit and the lower limit, automatic plate thickness control is continued, and if the rolling load deviates from the upper limit or the lower limit. Is characterized by interrupting the automatic strip thickness control, and more preferably, after suspending the automatic strip thickness control, the automatic strip thickness control is restarted when the rolling load returns to the midpoint between the set upper and lower limits. It is characterized by doing.

Further, the method for controlling the strip thickness of the metal strip in the reciprocating rolling mill according to claims 3 and 4 of the present invention is provided when the rolling load deviates from the upper limit value or the lower limit value set in the above strip thickness control method. It is characterized by performing plate thickness control with a constant rolling load using the upper limit value or the lower limit value, and more preferably, the automatic plate thickness control is restarted when the rolling load returns to an intermediate value between the set upper limit value and lower limit value. It is characterized by

[0013]

[Operation] According to the present invention, the upper and lower limit values are set for the rolling load at the start of AGC, and the AGC is cut off when the rolling load exceeds the upper and lower limit values. A load variation that causes a shape change that exceeds the shape control capability does not occur, and problems such as shape deterioration and narrowing can be prevented.

[0014]

EXAMPLES An example of cold rolling an austenitic stainless steel strip (SUS 304) using a 12-high cluster rolling mill according to the present invention is shown in FIG. In this figure, the horizontal axis represents the elapsed time after the start of rolling, and the vertical axis represents (a) the entry side plate thickness,
It shows (b) exit side plate thickness, (c) on / off of AGC, (d) rolling load, (e) operating state of roll bender, and (f) shape of steel strip.

After the time t _{0 has} elapsed after starting the rolling with the AGC turned on, the thickness of the inlet side plate becomes large as shown in (a).
Since this was corrected by the operation of the GC to keep the delivery side plate thickness at the target value, the rolling load increased as indicated by (d). When the rolling load increases, the roll bender acts as shown in (e) and (f) to correct the tendency of the shape of the steel strip to become elongated. Since the rolling load exceeded the set upper limit value, at this time t ₁ , the AGC was turned off as shown in (c) and the delivery side plate thickness deviated from the target value as shown in (b). It was possible to prevent the shape from being extremely deteriorated and the occurrence of narrowing.

Since it is not preferable to roll the pass to the end with the AGC turned off, the deviation in strip thickness on the entry side becomes small and the rolling load falls below the upper limit.
At t ₂ , the AGC is turned back on again. Note that it is at the time t ₁ exceeds the upper limit rolling load is set, remains in its upper limit rolling load as shown in (d), the also make rolling and held at a constant value. In this case, as shown in (b), the deviation of the outgoing side plate thickness may be further increased, but since the rolling load remains at a constant value, the roll bender effectively acts, and (f) results. As shown in the figure, the shape of the steel strip can be maintained in a good state and the narrowing can be prevented.

The upper and lower limits of the rolling load to be set cannot be unconditionally determined because it depends on the type and specifications of the rolling mill, but for example SUS 304, the upper limit is set at +30.
The ton and lower limit may be set to around -30ton. Also,
In the above embodiment, the case where the rolling load exceeds the set upper limit value has been described, but the same applies when the rolling load falls below the lower limit value.

The present invention is not limited to the type of rolling mill, but can be applied to all reciprocating rolling mills whose control items are the rolling position or rolling load.

[0019]

According to the present invention, in a reciprocating rolling mill in which troubles such as narrowing are likely to occur due to deterioration of shape, stable rolling can be performed using AGC from the first pass, and the productivity is remarkably high. It has the excellent effect of improving.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of the present invention.

FIG. 2 is a configuration diagram showing a reciprocating rolling mill according to the present invention.

FIG. 3 is a graph showing a conventional technique.

[Explanation of symbols]

 1 roll stand 11 work roll 12 intermediate roll 13 backup roll 14 load cell 15 hydraulic pressure reduction device 2a, 2b plate thickness gauge 3 deflector roll 4 tension reel 51 FB-AGC 52 FF-AGC 53 hydraulic pressure reduction control device S steel strip

Claims (4)

(57) [Claims] 1. A method for controlling the strip thickness of a metal strip in a reciprocating rolling mill, wherein an upper limit value and a lower limit value of the rolling load are set with reference to the rolling load at the time when the automatic strip thickness control is started, and at each pass rolling. When the rolling load is between the upper limit value and the lower limit value, the automatic plate thickness control is continued, and when the rolling load is out of the upper limit value or the lower limit value, the automatic plate thickness control is interrupted. A method for controlling the thickness of a metal strip in a reciprocating rolling mill. 2. The method for controlling the strip thickness of a metal strip in a reciprocating rolling mill according to claim 1, wherein the automatic strip thickness control is once interrupted, and then the rolling load returns to an intermediate value between the set upper limit value and lower limit value. A method for controlling the thickness of a metal strip in a reciprocating rolling mill, characterized in that automatic thickness control is restarted at a point of time. 3. When the rolling load deviates from the set upper limit value or lower limit value, the plate thickness control is performed with the rolling load constant by using the upper limit value or the lower limit value.
A method for controlling the thickness of a metal strip in a reciprocating rolling mill described in 1. 4. When the rolling load deviates from the upper limit value or the lower limit value set, plate thickness control is performed with the rolling load constant using the upper limit value or the lower limit value, and the rolling load is set between the upper limit value and the lower limit value. The plate thickness control method for a metal strip in a reciprocating rolling mill according to claim 1, wherein the automatic plate thickness control is restarted at the time of returning to the above.