KR100838842B1 - Control method for preventing center mark in skin pass mill of continuous annealing line - Google Patents

Abstract

The present invention relates to a temper rolling process of a continuous annealing line, and more particularly, to a coil welding part while preventing a center mark generated by a weld part connecting the front and back coil materials in the temper rolling process. The present invention relates to a method of interlocking control of the speed and rolling load of a temper mill when the welding part approaches the temper mill in order to prevent material defects in the wire and the rear end.

Continuous Annealing, Center Mark, Temper Rolling, Cold Rolling, Relief Mode

Description

Control method for preventing center mark in skin pass mill of continuous annealing line

1 is a schematic view showing the configuration of a cold rolling continuous annealing line.

2 is a graph showing the relationship between stress and strain in the tensile test of cold-rolled products.

3 is a block diagram of a conventional temper rolling equipment and a controller.

4 is a graph showing a change in control characteristics according to a conventional control method.

5 is a view showing a change in mechanical properties for each product position according to the conventional control method.

Figure 6 is a rough rolling equipment and a controller configuration in accordance with the present invention.

7 is a graph showing a change in control characteristics according to the control method of the present invention.

8 is a graph showing the change in mechanical properties of yield strength for each product according to the control method of the present invention.

9 is a view showing a change in mechanical properties for each product location according to the control method of the present invention.

<Description of the symbols for the main parts of the drawings>

1: pay off reel 2: welder                 

3: electrolytic cleaner 4: entry looper tower

5: Furnace 6: Exit looper tower

7: skin pass mill 8: oiler

9: tension reel 10: work roll

11, 12: lower, back up roll

13: intermediate roll 14, 26: load cell

15, 16: entry, exit tension bridle roll (entry, exit tension bridle roll)

17, 21: Business Computer (BC)

18, 25: Supervisor Control Computer (SCC)

19, 27: roll force controller

20, 28: hydraulic cylinder

22, 23: pulse generator

24: actual entry speed

29: roll force reference

30 elongation measurement

The present invention relates to a temper rolling process of a continuous annealing line, and more particularly, to a coil welding part while preventing a center mark generated by a weld part connecting the front and back coil materials in the temper rolling process. The present invention relates to a method of interlocking control of the speed and rolling load of a temper mill when the welding part approaches the temper mill in order to prevent material defects in the wire and the rear end.

Generally, in the continuous annealing line during the cold rolling process, as shown in FIG. 1, a cold rolled coil inserted into the payoff reel 1 is welded in the welding machine 2, and (5) is continuously passed through a heat treatment, and rolled in a skin pass mill (7) to impart the appropriate mechanical properties to the cold rolled product.

Figure 2 shows the relationship between the stress and strain appear in the tensile test of the annealed cold rolled sheet.

Referring to this, when the initial tension occurs, the yield point stretching phenomenon occurs as it falls from the upper yield point (A) to the lower yield point, and if the tension continues at the point (B) where the yield point stretching ends, the stress gradually increases, reaching the point C. Breakage will occur.

As shown in FIG. 2, the purpose of temper rolling is to give an elongation (EL: elongation) of about 0.5 to 1.5% to the annealed cold rolled sheet, and to produce a strain strain during product processing by yield point stretching. It is to prevent surface defects, to correct the shape of the annealed steel sheet, and to provide the appropriate roughness on the surface of the steel sheet to secure the paintability for use.

Elongation (EL: elongation) at this time can be determined by the following equation when the initial thickness of the steel sheet and the thickness of the steel sheet after rolling, respectively, T, t.                         

El = {(T-t) / T} X 100 (%)

On the other hand, briefly described the temper rolling process installed on the continuous annealing line exit as follows.

In general, the temper rolling mill is composed of a six-stage rolling machine, as shown in FIG.

The work cylinder and the drive shaft of the back up roll 11 respectively have a push cylinder to control the roll gap, the work roll 10 and the intermediate roll 13 Bender control is carried out as a choke cylinder of, and the intermediate roll 13 can shift from side to side.

A load cell 14 may be installed on the working shaft and the driving shaft of the upper reinforcement roll 12 to measure the rolling load, and before and after the temper rolling mill, an entry tension bridle roll 15 may be used. ) And an exit tension bridle roll 16 are provided to impart proper tension to the rolling mill entry and exit, and a tension gauge (not shown) is provided therebetween.

In the conventional operation method, when material information (thickness, width, steel grade, target elongation) to be worked on in the business computer (BC) 17 is transmitted, the supervisor control computer (SCC) 18 In order to secure the target elongation, the appropriate rolling load and the entry / exit tension are calculated.

The calculated rolling load is controlled by a hydraulic cylinder 20 in a roll force controller 19 to give a corresponding appropriate rolling load.

By the way, when the work of the preceding material is finished and the following material proceeds, when the welding portion connecting the preceding material and the following material passes through the temper rolling mill, the weld center mark is applied to the work roll 13 by the rolling load. The weld mark generated on the work roll 13 continues to transfer the weld mark to the material surface while rotating, thereby deteriorating the surface quality.

In order to solve this problem, conventional methods have introduced a relief mode system that reduces the rolling load when passing through the weld, thereby reducing the weld mark on the surface of the work roll 13.

This control process, as shown in Figure 4, for example, when working with low to medium carbon steel (thickness: 1.0mm, width: 1,100mm) as a material, can be described in the following steps.

Step 1: When the weld is detected by the weld detector, the temper rolling speed is reduced from 300mpm to 30mpm.

Step 2: The rolling load is relief from 2 tons before the weld passes through the temper rolling mill to reduce from 250 to 150 tons, and after 2 seconds after the weld passes through the roll of the temp rolling mill, the rolling load is 250 tons again. The original shape is restored to prevent the center mark generated by the welding portion due to the reduction of the rolling load.

Step 3: By the way, when the weld passes through the temper rolling mill, the change in elongation is maintained, maintaining 1.0% at exit speed 300mpm, and increasing to 1.3% as the exit speed decreases, and the rolling load is relief. Esau recovered to 1.0% and then increases back to 1.3% at the end of the relief.

Step 4: After the weld passes through the temper mill, in order to empty the storage stored in the entry looper as the temper mill decelerates, it accelerates to 400mpm higher than the center speed of 300mpm, in which case the elongation is maintained at 0.9%. If it runs at a constant speed of 300mpm, it converges at 1.0% of elongation.

The center mark can be prevented by this method, but as the weld portion is decelerated while passing through the temper mill, as the elongation exceeds the reference value by increasing the rolling load before and after the weld portion which is not affected by the relief mode, There was a disadvantage in that material defects occurred at the front and rear ends of the coil.

Looking at Figure 5, the yield strength (yield strength) at the leading end and the rear end of the material with the rolling load increase in accordance with the deceleration and low-speed operation at the leading end of the material exceeded the 280 MPa in spring, showing the actual 300 MPa, It is showing that this is happening.

The present invention was devised to solve the above problems, and to accelerate and decelerate in the temper rolling process in order to prevent material defects caused by the increase in yield strength of the center mark and the front and rear ends of the material during the temper rolling. The purpose is to provide a method of feedback control by interlocking the plate speed and rolling load during low speed operation.

Other objects and advantages of the invention will be described below and will be appreciated by the practice of the invention. Furthermore, the objects and advantages of the present invention can be realized by means and combinations indicated in the appended claims.

Control method for preventing the temper rolling center mark of the cold rolling continuous annealing line of the present invention for achieving the above object, the welding portion connecting the preceding material and the trailing material in the cold rolling continuous annealing line rough rolling machine (13) As a method to prevent center marks that are transferred to the rolls while passing through them and periodically generated on the surface of the work that is being rotated, the operation management provides the material information including the steel grade, thickness, and target elongation of the materials. Process management computer for calculating the rolling load according to the material information provided from the computer 21 and the operation management computer 21 and the speed of the temper mill input and detected and input by the pulse generator 22 attached to the temper mill entrance ( 25), and when the entrance temperature of the temper mill measured by the process management computer 25 is fed back, the center mark is released. And, the appropriate rolling load value for preventing the material leading end material defects is calculated in real time is input to the rolling load regulator 27, the rolling load regulator 27 according to the input appropriate rolling load is the hydraulic cylinder for pressing down ( 28) to be imposed on the lower reinforcement roll of the temper mill.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

6 shows the configuration of the temper rolling equipment and the controller according to the present invention.

Referring to this, an operation control computer (BC) 21 which provides material information such as steel grade, thickness, width, and standard elongation of a material in real time, and an entry-side tension bridging device of a temper rolling mill to measure elongation of a material Rolled according to the change in actual elongation and entrance velocity (24) calculated by the speed measured in pulse generators (22, 23) installed in tension bridle rolls to monitor the speed of the material flow. The supervisory control computer (SCC) 25 for calculating the load and the load cell 26 for measuring the rolling load of the work roll in real time and the rolling load measured at the load cell are compared with the reference rolling load. Compensating for the difference, the rolling load controller 27 for matching the actual rolling load to the reference rolling load and the hydraulic cylinder 28 whose rolling load is controlled by the indication values of the rolling load controller 27 are obtained. It is.

When data related to the material information, that is, the steel grade, thickness, width and target elongation of the material are input from the operation management computer (BC) 21 to the operation management computer (SCC) 25, The rolling load for producing the target elongation according to the tension on the entry and exit side of the rolling mill is calculated as follows.

There have been many theories for calculating the rolling force under rolling conditions, and Orowan's theory does not assume sliding friction or constant yield stress during rolling.The most rigorous analysis or its interpretation is complicated, Apply the approximate Bland Ford's formula.

On the other hand, roll flatness uses the Hitchcock equation.

R ′ = R [1 + 2Co {P / (b * Δh)}]

Co = 8 (1-m * m) / (πE)

Where R ': flat roll radius, R: roll radius, Co: elastic modulus, P: rolling load, b: average plate thickness, Δh: plate thickness difference value (entrance to exit), m: Poisson Ratio (= 0.3), π: circumference (= 3.14), E: Young's Modulus (= 2.1 * 10 ⁴ kgf / mm ² ).

Then, by applying the hitchcock equation, the rolling load for producing the target elongation is calculated as follows.

P = K (1-σi / K) * (R´ (Hi-Ho)｝ ^1/2 * f5 (arb)

Where P is the rolling load, K is the average yield stress of the material,? I is the roll inlet tension, Hi is the plate thickness, Ho is the plate thickness, and f5 (arb) is the reduction function.

The calculated rolling load 29 is imposed on the backup roll by operating the hydraulic cylinder 28 in the rolling load regulator 27.

When the work of the preceding material is finished and the trailing material passes, the welding part connecting the preceding material and the following material enters, and as the speed of the material passing through the temper mill decreases, the pulse generator attached to the temper mill inlet 22 When the elongation rate 30 calculated by the difference between the speed detected at the step and the speed detected at the entry and exit of the temper mill is fed back to the operation management computer (SCC) 25, the change of the strip speed by the above Equation 4 is performed. According to the instantaneous rolling load value 29 is calculated, the calculated rolling load is applied to the appropriate rolling load by controlling the hydraulic cylinder 28 in the rolling load regulator 27.

Example

Figure 7 shows the operating conditions by real time when producing a low-low carbon steel (thickness: 0.8 ~ 1.2㎜, width: 1,100㎜) material in the actual line for one month.

As the preceding material, which was initially fixed in the range of 250 ~ 350mpm in the center speed, is decelerated to 30mpm at the end of the work, the rolling load is also reduced in conjunction with the rolling mill rolling speed. By reducing the occurrence of the center mark and maintaining a constant elongation of 0.8 ~ 1.2%, it is possible to prevent material defects after welding failure.

Once the weld passes through the temper mill, the temper mill speed is accelerated, and the deceleration speed is increased to 350-450mpm over 250-350mpm to reduce the material stored in the looper, and the looper When the stored material is exhausted, it will return to the constant speed of 250 ~ 350mpm.

At this time, the speed of the temper mill is measured by the pulse generator and fed back to the process management computer (SCC) 18 to control the appropriate rolling load.

Figure 8 shows the distribution of yield strength (YS: Yield Strength) according to the product thickness.

Referring to this, the yield strength is distributed lower than the reference value of 280 MPa in the front end and the rear end of the material, showing good material performance.

In addition, referring to Fig. 9 showing the change in mechanical properties according to the product position, the same results in the leading end and the rear end of the material under the same elongation (1.0%) showed a good performance of less than the reference value 280MPa, the difference between the material center and 10MPa It is judged that this is due to the material deviation of the location of the input material hot coil (hot coil).

Here, the Tensile Strength (TS) shows 320 ~ 340MPa within the standard range (270≤TS≤400MPa), showing stable performance, and the elongation exceeding the standard value of 40 ~ 42. Indicating% indicates good performance.

As mentioned above, although this invention was demonstrated by the limited embodiment and drawing, this invention is not limited by this, The person of ordinary skill in the art to which this invention belongs, Of course, various modifications and variations are possible within the scope of the claims to be described below.

According to the present invention, when the welding portion connecting the preceding material and the following material passes through the rough rolling mill, the welding speed is transferred to the work roll by interlocking the rolling load in the operation management computer by detecting the change in the rough rolling speed in the pulse generator. Due to the generated center mark and the increase in the rolling load due to the acceleration and deceleration and the low speed operation, it is possible to prevent material defects at the front and rear ends of the material, thereby reducing various costs required to remove the defective parts and improving productivity.

Claims (1)

In the cold rolling continuous annealing machine, the welded part connecting the preceding material and the following material in the temper rolling mill is transferred to the roll while passing through the work roll 13, and prevents the center mark which is periodically generated on the surface of the work material as the roll rotates. As a way to Sensing and measuring at the operation management computer 21 which provides the material information including the steel grade, the thickness and the target elongation of the material, the material information provided from the operation management computer 21 and the pulse generator 22 attached to the entrance of the temper mill. The process control computer 25 for calculating the rolling load according to the temper rolling mill entrance speed When the tempered mill entrance speed measured by the process management computer 25 is fed back and input, the appropriate rolling load value for preventing the center mark and preventing material defects in the front and rear ends of the material is calculated in real time, and thus the rolling load regulator 27. Of the cold rolling continuous annealing line, characterized in that the rolling load regulator 27 controls the hydraulic cylinder 28 for pressing according to the input appropriate rolling load so as to be imposed on the lower reinforcement roll of the temper rolling mill. Control method to prevent temper rolling center mark.

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