JP3016632B2 - Operation control method of twin roll continuous caster. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously casting a stainless steel sheet directly from a molten metal by a twin-roll continuous caster. More specifically, the present invention relates to a method for forming a twin solidified shell formed on a twin-roll surface. The present invention relates to a continuous casting method for a stainless steel thin plate, in which a pressing force when a roll is pressed at a narrowest portion of a roll is accurately detected, and the casting is performed with a small pressing load that does not cause cooling unevenness.

[0002]

2. Description of the Related Art A pair of internal cooling rolls rotating in opposite directions are opposed to each other in parallel with an appropriate gap therebetween, and a pool is formed on a roll circumferential surface above the gap (roll gap). A twin-roll type continuous casting machine that continuously casts a thin plate while pressing the solidified shell formed between the two rolls while cooling the hot water in the pool on the rotating rolls. It has been known. There have been proposals to apply such a twin-roll type continuous casting machine to continuous casting of steel to directly produce thin steel sheets from molten steel, and various proposals for improvement have been reported.

For example, JP-A-1-317660 discloses that one of the twin rolls is a movable roll and the other is a substantially fixed roll, and the movable roll is relatively moved toward the fixed roll to adjust the roll gap to fix the roll gap. An invention is disclosed in which the load of both rolls applied to the back side of the rolls is detected, and the pressing load applied to the plate is controlled by the load detection signal.

[0004] In order to make the crimping load applied to the plate more accurate, the inventors of the present invention have previously described Japanese Patent Application Nos. 2-214041 and 2-214041.
In 214042, etc., a first load detector that detects the load applied to the fixed roll from the movable roll and a second load detector that detects the entire load applied behind the fixed roll are installed. We proposed a method to control the rotation speed of both rolls so that the detected load difference, that is, the pressure load applied to the plate is within a predetermined range.

[0005]

The greater the pressure applied to the plate when passing through the narrowest portion of the roll, the greater the amount of heat removed to the cooling roll and the more uneven cooling on the plate surface. . In particular, with stainless steel such as SUS304, this uneven cooling causes uneven gloss of the final product.
The beauty of the surface significantly reduces the value of the required product.

According to the load detection method proposed in Japanese Patent Application Nos. 2-214041 and 2-124042, the pressure applied to the plate can be detected more accurately than in the case of Japanese Patent Application Laid-Open No. 1-317660.
However, even in these methods, if the frictional force generated when the roll chock moves along the frame guide is large, there is a problem that the frictional resistance makes the detected pressure load value inaccurate. This makes it difficult to precisely control the crimping load at a small crimping load level that does not cause uneven gloss.

Further, when a gap is easily generated between the guide and the chock as in the sliding guide system, a twisting load is generated, and as a result, a difference is generated between the crimping load applied to the rotation transmission shaft side and the idle rotation shaft side. Was. Due to this difference in the crimping load, significant meandering of the plate occurred during casting, and quality defects such as uneven glossiness occurred on the plate surface. The present invention seeks to solve the above problems.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a molten metal is injected into a gap above a pair of internal cooling rolls which rotate in opposite directions with their axes parallel to each other. In a twin-roll continuous caster in which the solidified shell of the metal formed above is pressed at the narrowest gap between the rolls and continuously cast into a thin plate, the shaft of one roll (movable roll) is connected to the other roll (fixed). The chocks of both rolls are supported by a frame guide so that they can be moved in parallel by a hydraulic cylinder on the side of the roll), and the movable roll is pressed against the fixed roll by a predetermined pressing force by the hydraulic cylinder during casting. Sometimes a first load detector that detects the load applied to the fixed roll from the movable roll and a second load detector that detects the total load applied behind the fixed roll are installed, and are detected by both load detectors The rotation speed of both rolls is controlled so that the weight difference falls within a predetermined range, and the frictional force associated with the movement of both rolls is reduced to a range satisfying the following formulas (1) and (2). An object of the present invention is to provide an operation control method for a roll type continuous casting machine. w · f <P · L (1) | F _D −F _w | <P · L (2) where P: crimping load value per unit plate width (N / mmW), L : Plate width (mm), f: Maximum friction coefficient between the frame guide and the roll chock, w: Force (N) by the frame guide through one roll chock, F _D : In the hydraulic cylinder on the rotary power transmission shaft side the sum of the frictional force between the frictional force and fixed Roruchiyokku and frame guide surface between the friction forces and the movable roll chock and the frame guide faces, F _w: frictional forces and the movable roll chock and the frame guide surface idler shaft side in the hydraulic cylinder The sum of the friction force between the fixed roll chock and the frame guide surface.

[0009] When casting a stainless steel sheet for which surface beauty is important, the above-mentioned crimping load value P per unit plate width is set to 2.0 (N / mmW) or more and 9.8 (N / mmW) or less. Then, the above control is performed.

[Detailed Description of the Invention] FIG. 1 is a plan view showing a twin-roll continuous caster to which the present invention is applied. In FIG. 1, reference numerals 1 and 2 denote internal cooling rolls, and these rolls 1 and 2 are arranged parallel to each other with their axes horizontal and rotate in opposite directions. Reference numerals 3 and 4 denote side dams provided on the sides of the pair of rolls. The molten metal in the pool 5 formed on the circumferential surface of the roll surrounded by the side dams 3 and 4 solidifies on the circumferential surface of the roll. , And both solidified shells are cast into a thin plate through the narrowest gap between the rolls. 6 shows a cross section of the thin plate corresponding to the narrowest gap.

In such a twin-roll type continuous casting machine, as a mechanism for adjusting the gap width of the narrowest gap between the rolls (referred to as a roll gap), the shaft 7 of one roll 1 is moved in the direction of the other roll 2. To move the shaft 7 with the chocks 8
The chocks 8a, 8b are moved in the direction of the other roll 2 by the pistons 9a, 9b. The pressing force of the pistons 9a, 9b is adjusted by hydraulic control of the hydraulic cylinders 10a, 10b. The hydraulic cylinders 10a, 10b are fixed to one frame 11. The roll 1 that directly receives this pressing force is called a “movable roll”.

On the other hand, the shaft of the roll 2 is also supported by the chocks 12a, 12b, and the gap width adjusting members 13a, 13b are interposed between the chocks 12a, 12b and the former chocks 8a, 8b. The detectors 14a and 14b are inserted. Also chocks 12a, 12b
The other end of the second load detector with respect to the other frame 15
They are connected via 16a and 16b. This second load detector 16a, 1
In order to detect the entire pressing force in 6b,
12a and 12b are also supported movably in the axial direction of the pistons 9a and 9b, but since the roll 2 is on the side receiving the load,
This is called a "fixed roll".

With this configuration, the hydraulic cylinders 10a, 10b
The first load detectors 14a and 14b can detect the load applied to the fixed roll 2 from the movable roll 1 while casting while pressing the movable roll 1 toward the fixed roll 2 by the control pressure. The entire load applied behind the can be detected by the second load detectors 16a and 16b.

The rotating power is applied to both shafts of the movable roll 1 and the fixed roll 2 from a motor 17 provided on one side of the two rolls. Conveyed through. The rotation speed of the motor 17 is controlled by a motor rotation speed control device 19.

In the twin-roll type continuous caster capable of controlling the roll gap, the equipment shown in FIG.
A relief valve 21 is attached to a main pipe 20 communicating with hydraulic pipes 20a and 20b to 10a and 10b, and a constant oil pressure is applied to both cylinders 10a and 10b by setting the opening of the relief valve 21.
In the example of FIG. 1, relief valves 21a and 21b are interposed in hydraulic piping 20a and 20b communicating with the hydraulic cylinders 10a and 10b, respectively, so that the hydraulic pressure can be controlled for each cylinder.

As the relief valves 21a and 21b, motor-operated valves for automatically controlling the hydraulic pressure release amount by hydraulic valve opening adjusters 24a and 24b are used. This hydraulic valve opening regulator 24a, 24b
, Detection signals from the second load detectors 16a and 16b are input as control signals for the hydraulic pressure release amount. Hydraulic valve opening regulator 24
a, 24b is the target value of the roll pressing force 1 / 2P ₀ (the pressing force of each cylinder is half of the target value P ₀ of the total pressing force)
And the detection signals P _D2 and P _W2 from the second load detectors 16a and 16b are compared, PI calculation is performed on the two, and a rotation amount command is output to the motors of the relief valves 21a and 21b so as to eliminate the difference. That is, feedback control is performed so that P _D2 and P _W2 fall within a certain narrow set value.

In FIG. 1, reference numeral 25 denotes an arithmetic processing unit _, 26 denotes a comparison arithmetic processing unit, and 27 denotes a speed pattern generator. The control mode in the apparatus of FIG. 1 is as follows. First, before casting, the gap width adjusting members 13a, 13b having a predetermined width are formed.
After the clearance is set, the hydraulic pressure applied to both cylinders 10a and 10b is set by setting the opening of the relief valve 21. During the casting, the load values P _D1 and P _W1 detected by the first load detectors 14a and 14b and the load values P _D2 and P _W2 detected by the second load detectors 16a and 16b are processed by the arithmetic processing unit 25. And based on these values, the arithmetic processing unit 25 executes the operation of the following equation,
And it outputs the calculated value P ₃ of the crimping load. _{P 3 = (P D2 + P} W2) - (P D1 + P W1)

That is, the difference between the detected values of the first load detector and the second load detector is determined. In the illustrated equipment, the first load detectors 14a, 14b and the second load detectors 16a, 16a, 16b
_Is the two lines on the roll _side, that is, the rotational power transmission side
(Drive side) and two groups of idle bearing side (Work side).
The difference between the total amount of 14a, 14b and the total amount of the second load detectors 16a, 16b is determined by the above equation.

The calculated value P ₃ is input to the comparison processing unit 26, where the difference between the crimping load target value P _A and P ₃ is calculated (for example, PI calculation), and the crimping load target value P _{A is} calculated. A difference ΔP between the measured value and the measured value is obtained, and this ΔP is output as a rotation speed command signal to the motor rotation speed control device 19, and the motor 17
Operate the rotation speed of. That is, if the crimping load is higher than the target value, the roll rotation speed is increased. Conversely, if the crimping load is lower than the target value, the roll rotation speed is reduced, and control is continued during casting so that the crimping load approaches the target value. . As a result, even if the pressing force applied to the cylinders 10a, 10b fluctuates for some reason, the actual pressing force is changed to the second load detector 16a,
It is measured by 16b, and based on the measured value, the crimping load is controlled to be constant, so that the fluctuation of the pressing force does not affect the fluctuation of the crimping load. The deceleration and acceleration patterns are set using the speed pattern generator.
Perform by 27.

By adopting such a control mechanism, the fluctuation of the crimping load is extremely reduced. However, when such precise control is performed, it is necessary to press the chock with a predetermined pressure using the hydraulic cylinders 10a and 10b. , Fixed roll chocks12
The larger the frictional resistance of the first load detectors 14a and 14b
There may be a difference between the load values of b and the second load detectors 16a and 16b by the amount of frictional resistance. Generally, the second load detector is compared with the load value of the first load detector 14a, 14b.
The load values of 16a and 16b are smaller by the frictional resistance. Also, if the frictional resistance between the rotating power transmission shaft side and the idler shaft side of the chocks of each roll is different, the prying load is likely to occur,
The crimping load on the rotating power transmission shaft side and the free rotation shaft side differs.

It is practically impossible to make such frictional resistance and difference zero. Therefore, the present invention has been made to find appropriate conditions for preventing the influence of the disturbance caused by such frictional resistance and the difference between them, and simultaneously examined the relationship between the crimping load on SUS304 and the degree of the uneven cooling pattern. The conditions for obtaining a product with good surface properties were studied.

FIG. 2 shows the result of examining the relationship between the degree (index) of the uneven cooling pattern and the pressure load in SUS304. This result indicates that the cooling unevenness pattern is reduced as the crimping load is reduced. In order to prevent the occurrence of gloss unevenness due to the cooling unevenness pattern in the final product (cold rolled product), the unit must be It was found that the crimping load applied per sheet width had to be very small, about 9.8 N / mmW or less. On the other hand, if the crimping load is reduced to about 2.0 N / mmW or less, the unsolidified area in the center of the sheet thickness becomes thicker, and immediately after the sheet separates from the roll, the sheet surface temperature rises significantly due to reheating, and It was found that cracks occurred, and if severe, they broke.

Therefore, in order to prevent the plate from cracking or breaking due to reheating and to suppress the occurrence of uneven gloss, it is necessary to control the pressure bonding load to a very weak and narrow range of 2.0 to 9.8 N / mmW. . Ideally, the frictional resistance between the roll chock and the frame guide should be made as small as possible to make the frictional resistance zero, but it is impossible to make the frictional force zero.

In order to enable control of the crimping load in the above narrow range, the force applied to the frame guide via one roll chock is w (N), the maximum friction coefficient between the frame guide and the roll chock is f, Assuming that the width of the obtained thin plate is L (mm), the maximum frictional resistance fw acting on the sliding surface between the roll chock and the frame guide is made smaller than the total crimping load PL in the plate width direction. It is necessary. That is, equation (1) must be satisfied. w · f <P · L (1) More practically, w · f is less than 2.0 · L obtained by substituting P = 2.0 N / mmW, which is the minimum value of the target control range, into equation (1). I have to be satisfied.

As described above, even if the crimping load can be controlled within the range of 2.0 to 9.8 N / mmW, the difference between the frictional force on the rotating power transmission shaft side and the frictional force on the idler shaft side is larger than P · L. If big,
An uneven cooling pattern occurs in the width direction of the thin plate obtained by casting. Therefore, if the sum of the frictional resistance in the hydraulic cylinder and the frictional force between the movable roll chocks and the fixed roll chocks with the guide surfaces is F _D on the rotational power transmission side and F _W on the idle shaft side, F _D and F _W Is the difference between the absolute values of (2)
The expression must be satisfied. | F _D -F _w | <P · L (2)

It should be noted that the constraints of the equations (1) and (2) are the minimum conditions, and in order to further facilitate the crimping load control, the values on the left side of the equations (1) and (2) must be It is better to be as small as possible.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the control mechanism of the twin-roll continuous caster shown in FIG. 1, in this embodiment, as shown in FIG.
The guide system between the lower frame 29a (29b) and the upper frame 30a (30b) for movably supporting the a (8b) and 12a (12b) employs a rail-circulating ball rolling guide system. FIG. 3 shows the idle shaft side, and reference numerals in parentheses indicate those on the drive shaft side. That is, track rails 31a (31b) and 32a (32b) are attached to frames 29a (29b) and 30a (30b), and ball rolling guides 28a (28b) rolling on these rails are connected to chocks 8a (8b).
Mounted on 12a (12b). Through this ball rolling type ball rolling, the chocks 8a (8b) and 12a (12b) can be moved along the track rails 31a (31b) and 32a (32b) with a small frictional resistance, and the prying load is almost completely reduced. It does not occur.

When a copper alloy sleeve roll having a roll diameter of 600 mmφ and a width of 300 mm was used, the force w applied to the frame guide surface through the chocks of one roll was measured to be 9000
N. The maximum coefficient of friction by the ball rolling guide was 0.025. Therefore, the maximum frictional resistance w
f was 9000N × 0.025 = 225N, and satisfied the total crimping load P · L in the sheet width direction of less than 2.0N / mmW × 300mm = 600N.

Hydraulic cylinders for D side and W side respectively
Table 1 shows the indicated values of the first load detector and the second load detector respectively when the pressure of 98 kN was applied to the D side and the W side. Pressure calculated from hydraulic pressure and cylinder area (cylinder pressure)
Although the indicated value of the first load detector is slightly lower by the frictional resistance in the cylinder, the difference between the indicated values of the first and second load detectors is 200N even on the larger side.
Was small. Further, the difference between the value of the load detector between the D side and the W side | F _D -F _w | is small as 100 N, a constraint of the difference between the frictional resistance force between the D side and the W side P · L Less than 60
Less than 0N was satisfied.

In such a twin-roll continuous caster, 18C
100 kg of r-8Ni stainless steel was cast into a thin plate of 2 mmt × 300 mmw. At this time, as shown in Table 1, the maximum frictional resistance between the guide of one roll and the chock is the target value of 600N.
(P · L = 2.0 × 300), so the change in pressure load per unit plate width applied to the plate during casting was 2.0 N / m.
Detected at mW level. As a result, the crimping load could be easily controlled within the range of 2.0 to 9.8 N / mmW except at the very beginning of casting. The difference in the crimping load between the D side and the W side was 10
0N or less.

There were no cracks on the surface of the cast plate obtained in this example, and the pattern of uneven cooling was very slight. The cast plate was annealed and cold rolled. As a result, there was no gloss unevenness due to the uneven cooling pattern.

[0032]

Comparative Example In a device having the same load detecting mechanism as that of the embodiment, a cast iron slide guide (with lubricating oil) was adopted as a guide system between the chocks of the fixed and movable rolls and the roll guide surface. The hydraulic cylinder used was a normal hydraulic cylinder. In this case, the force w applied to the frame guide was 9000N.

As in the embodiment, the hydraulic cylinder is set on the D side,
Table 1 shows the indication values of the first load detector and the second load detector for the D side and W side respectively when a pressure of 98 kN is applied to each of the W side.
It was shown to. The maximum coefficient of friction was 0.21 in this cast iron slide guide (with lubricating oil) system. Therefore, the maximum frictional resistance w · f is 9000N × 0.21 = 1890N, and P · L = 600N
Not less than. Further, the difference between the value of the load detector between the D side and the W side | F _D -F _w | is also 700N also lower, P ·
L was less than 600 N, and a pry load was generated.

In this twin-roll type continuous caster, 100 kg of 18Cr-8Ni stainless steel, which is the same as in the above embodiment, is 2 mmt × 300 mm.
W was cast into a thin plate. As a result, the crimping load during casting was 2.0
Because stable control was not possible within the range of ~ 9.8 N / mmW,
Cracks due to unsolidification occurred on the surface of the cast plate, and a clear cooling uneven pattern was observed even at the position where there was no crack.
The cast plate was annealed and cold rolled. As a result, uneven gloss was observed at the position where the cooling uneven pattern was clear.

[0035]

[Table 1]

[0036]

As described above, the stainless steel sheet casting method of the present invention makes it possible to detect a very small change in the crimping load during casting, thereby improving the control accuracy of the crimping load. Therefore, it is possible to stably produce a thin plate having no defect in surface quality.

[Brief description of the drawings]

FIG. 1 is an apparatus arrangement system diagram showing a crimping load detecting mechanism in a twin-roll continuous casting machine to which the method of the present invention is applied.

FIG. 2 is a diagram showing a relationship between a pressing load and a cooling uneven pattern.

FIG. 3 is a side view of a twin-roll continuous casting machine to which the method of the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Movable roll 2 Fixed roll 3, 4 Side dam 5 Pool 6 Roll gap (section of thin sheet to be cast) 7 Roll shaft 8a, 8b Chock of movable roll 9a, 9b Piston 10a, 10b Hydraulic cylinder 11, 15, Vertical frame 12a, 12b Chock of fixed roll 13a, 13b Gap setting member 14a, 14b First load detector 16a, 16b Second load detector 18 Reduction gear 19 Motor rotation speed control device 20a, 20b Hydraulic piping 21a, 21b Electric relief valve 23 Hydraulic pump 24a, 24b Hydraulic valve opening degree setting device 25 Arithmetic processing unit 26 Comparison arithmetic processing unit 27 Speed pattern generator 28 Rail circulation type ball rolling guide 29a, 29b Lower frame 30a, 30b Upper frame 31 Track rail

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-63650 (JP, A) JP-A-1-317660 (JP, A) JP-A-1-166686 (JP, A) JP-A-60- 83747 (JP, A) JP-A-60-64754 (JP, A) JP-A-4-94846 (JP, A) JP-A-4-94845 (JP, A) JP-A-3-254336 (JP, A) JP-A-3-72030 (JP, A) JP-A-64-107943 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/06 330 B22D 11/16 104

Claims (3)

(57) [Claims] 1. A molten metal is poured into a gap above a pair of internal cooling rolls rotating in opposite directions and disposed in parallel to each other with their axes parallel to each other, and the metal formed on the circumferential surface of the pair of rolls is melted. In a twin-roll continuous caster that continuously casts a thin plate by pressing a solidified shell at the narrowest gap between rolls, the axis of one roll (movable roll) is attached to the other roll (fixed roll) by a hydraulic cylinder. The chocks of both rolls are supported by a frame guide so that they can move in parallel, and when the movable roll is pressed against the fixed roll by the hydraulic cylinder with a predetermined pressing force during casting, the movable roll moves from the movable roll to the fixed roll. A first load detector that detects the applied load and a second load detector that detects the total load applied behind the fixed roll are installed so that the load difference detected by both load detectors falls within a predetermined range. Control the rotation speed of both rolls
And the frictional force associated with the movement of both rolls is given by the following equation (1) and (2)
An operation control method for a twin-roll continuous caster characterized by reducing the value to a range that satisfies the expression, w · f <P · L (1) | F _D −F _w | <P · L. (2) Here, P: Crimping load value per unit plate width (N / mmW), L: Plate width (mm), f: Maximum friction coefficient between frame guide and roll chock, w: Chock of one roll (N), F _D : The sum of the frictional resistance in the hydraulic cylinder on the rotating power transmission shaft side, the friction between the movable roll chock and the frame guide surface, and the friction between the fixed roll chick and the frame guide surface , F _w : the sum of the frictional resistance in the hydraulic cylinder on the idle shaft side, the friction between the movable roll chocks and the frame guide surface, and the friction between the fixed roll chocks and the frame guide surface. 2. The molten metal is a stainless steel molten steel, and a crimping load value P per unit plate width is 2.0 (N / mmW) or more and 9.8 (N / mmW).
The method for controlling the operation of a twin-roll continuous caster according to claim 1, which is maintained below. 3. The operation control method for a twin-roll continuous caster according to claim 1, wherein the chocks of both rolls are supported by a frame guide in a ball rolling guide system.