JP3302838B2 - Light reduction amount control method in continuous casting - 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 controlling the amount of light reduction in continuous casting, which reduces the slab having an unsolidified portion in a continuous casting facility to prevent the generation of center segregation and center porosity.

[0002]

2. Description of the Related Art Central segregation of continuously cast slabs is caused by the flow of concentrated molten steel due to solidification shrinkage. Therefore, in order to improve central segregation, the flow of concentrated molten steel is suppressed, and It is important to prevent the accumulation of On the other hand, the center porosity is generated because solidification progresses at the center of the slab, and when the hot water supply property in the solid-liquid coexisting phase is lost, the volume decrease due to solidification shrinkage is not compensated. It is known that, in improving the center segregation and the center porosity of the continuous cast slab, light rolling at the end of solidification, in which the continuous cast slab having an unsolidified portion is reduced, is effective.

[0003] Under the final solidification light pressure in continuous casting, if the amount of reduction is insufficient, the prevention of generation of center segregation and internal defects becomes insufficient. Therefore, it is necessary to control the amount of reduction in an appropriate range.

[0004] As a light reduction control method using a guide roll segment, Japanese Patent Laid-Open No. 5-8004 discloses a method in which a position control cylinder is disposed for each roll bearing of a light reduction segment disposed at the end of solidification. A method is disclosed in which a reduction amount calculator for controlling the amount of movement of the cylinder is provided, and the rod movement amount of the cylinder is set for each roll at least by the sum of the actual slab reduction amount, the frame deformation amount, and the roll deformation amount. However, it does not describe where to set the reference point of the position control cylinder. Further, there is no description about the change in the actual slab thickness, the roll wear, and the play of the pressing mechanism depending on the casting site. Further, there is no description of a case where the actual slab reduction amount, that is, a value obtained by subtracting the slab thickness after reduction from the slab thickness before reduction varies due to variation in slab deformation resistance or the like.

Japanese Patent Laid-Open No. Hei 5-13125 discloses that
A load cell is installed on each roll bearing part of the upper segment to measure the roll reaction force, obtain the amount of strain corresponding to the roll reaction force from the load-strain amount characteristic, and move the roll by this amount of strain to obtain a constant reduction amount. A method of obtaining is disclosed. However, this method requires load cells and distortion amount calculation devices for the number of rolls under rolling by the multi-stage rolls, resulting in large equipment costs.

[0006]

In the light reduction amount control method in which the reduction amount is set by the rod movement amount of the position control cylinder, the actual reduction amount of the slab, that is, the thickness of the slab after reduction from the thickness of the slab before reduction. It is indispensable to strictly control the value obtained by subtracting the value of, and as in the method described in Japanese Patent Application Laid-Open No. 5-8004, the amount of cylinder rod movement to be reduced by correcting the amount of frame deformation and the amount of roll deformation is required. Setting is not enough. That is, in the light rolling device in which the rolling amount is set by the rod movement amount of the position control cylinder, in addition to the frame deformation amount and the roll deformation amount, the slab cross-sectional size varies depending on the casting site, the wear amount of each roll, the rolling reduction mechanism. It is necessary to have a correction technique capable of following the backlash, the fluctuation of the slab thickness or the slab surface position on the entry side of the light reduction device, and the variation of the slab deformation resistance.

The present invention provides these correction techniques to enhance the effect of improving the internal quality, which was not always sufficient in the conventional light reduction amount control method, and to stably produce a slab having a good internal quality. A method for controlling a light reduction amount is provided.

[0008]

The present invention provides the following:
It is as follows.

1) The first invention is a method for controlling the amount of reduction of the light reduction roll by a position control cylinder attached to a bearing of the light reduction roll disposed near the end of solidification of the continuous cast slab. moth of the mechanical system of the soft reduction roll to the slab surface
This is a method of controlling the amount of light reduction in continuous casting, wherein the cylinder is pressed once to such an extent that it kills, and a cylinder target position for obtaining a desired reduction amount is set using the cylinder position at that time as a reference point.

2) The second invention is the first invention , wherein
Measure the slab surface position or slab thickness at the side of the light pressure roll
And a method for controlling a light reduction amount in continuous casting, wherein the cylinder target position is corrected according to the value .

[0011] 3) The third invention is the first shot Akira,
This is a method for controlling the amount of light reduction in continuous casting, characterized by actually measuring the slab surface position or slab thickness on the exit side of the light reduction roll and correcting the cylinder target position according to the measured value.

[0012] 4) The fourth invention is the first shot Akira,
Measure the slab surface position , slab thickness , or slab width on the entrance side and exit side of the light pressure roll, and cast from the difference in the slab shape on the entry and exit sides.
A method for controlling a light reduction amount in continuous casting, wherein a single actual reduction amount is obtained, and a cylinder target position is corrected according to a difference between the actual reduction amount of the slab and a predetermined reduction amount.

[0013] 5) The fifth invention is the first shot Akira,
The light slab at the entrance and exit of the roll
Measure the amount of drawing movement, and use the measured values to reduce the slab
The elongation of the slab is determined from the elongation, and the cylinder target position is corrected according to the difference between the actual slab reduction and the predetermined reduction. It is a quantity control method.

6) A sixth aspect of the present invention is to provide a method for producing a continuous cast slab near the end of solidification.
For position control attached to the bearing of a light pressure roll installed next to it
How to control the amount of reduction of the light reduction roll by cylinder
In the method, the light pressure roll is once brought into contact with the slab surface.
The cylinder position at the time of contact as a reference point.
Set the cylinder target position to obtain the reduction amount, measure the amount of drawing movement of the slab per unit time on the entrance side and exit side of the light reduction roll, and calculate the elongation percentage of the slab due to slab reduction from both measured values. A method of controlling a light reduction amount in continuous casting, wherein a slab actual reduction amount is obtained from the elongation percentage, and a cylinder target position is corrected according to a difference between the slab actual reduction amount and a predetermined reduction amount. .

[0015]

The present inventor has found that, in order to improve segregation and center porosity without generating internal cracks under light pressure at the end of solidification, there is an appropriate range for the reduced portion and the amount of reduction applied to the slab. ing. In particular, in order to obtain a stable internal quality improvement effect, it is indispensable to accurately control the amount of reduction substantially applied to the slab, that is, the actual amount of reduction of the slab. Then, a light reduction roll is disposed near the end of solidification of the continuous cast slab, and a position control cylinder is provided for each roll bearing to control the roll reduction position to obtain a desired slab reduction amount. In order to accurately control the actual slab reduction by the control method, at least the following measures are required in addition to the correction of the frame deformation and the roll deformation.

First, the thickness change due to solidification shrinkage and bulging of the slab in the light reduction segment is obtained by model calculation or actual measurement to grasp the position of the slab surface facing the light reduction roll. Is set as a reference point of the position control cylinder of each light reduction roll, it is necessary to take measures to correct the variation of the slab cross-sectional size due to the casting position.

Second, the amount of wear of each light pressure roll was measured.
It is necessary to take measures to correct and set the rod movement amount of the position control cylinder.

Third, it is necessary to measure and correct the play of the screw-down mechanism to set the rod movement amount of the position control cylinder.

Fourth, it is necessary to grasp the thickness of the slab or the surface position of the slab on the side of the light reduction device, and to set the rod movement amount of the position control cylinder of each light reduction roll according to the thickness. .

Fifth, when the actual slab reduction amount fluctuates due to variations in slab deformation resistance or the like, this is quickly detected and the rod movement amount of the position control cylinder is adjusted so that the target reduction amount can be obtained. Needs to be corrected.

Therefore, first, when setting the rod moving amount of the position control cylinder, the roll under the light pressure is once brought into contact with the surface of the slab, and the inner position of the slab is determined using the cylinder position at the time of contact as a reference point. By providing the amount of reduction for improvement, it is possible to substantially eliminate the variation in the cross section size of the slab and the wear of each roll due to the casting site.

Secondly, when setting the rod movement amount of the position control cylinder, a light pressure roll is once pressed against the surface of the slab to such an extent as to loosen the play of the pressure reduction mechanism, and the cylinder position at that time is set as a reference point. By providing the amount of reduction for improving the inside quality of the piece, it is possible to substantially eliminate backlash and roll wear of the reduction mechanism.

Thirdly, when setting the rod movement amount of the position control cylinder, the surface position or thickness of the slab on the light-roll-down roll entry side is actually measured, and the rod movement amount is corrected by following the value. An appropriate amount of reduction can be given by following the surface position or thickness of the slab before light reduction.

Fourthly, when the amount of movement of the rod of the position control cylinder is set, if the surface position or the thickness of the slab on the light reduction roll entry side is very small, the slab on the light reduction roll exit side is small. By measuring the surface position or the slab thickness, estimating the actual slab reduction amount from the value, and correcting the rod movement amount according to the value, an appropriate reduction amount can be secured.

Fifth, when setting the rod movement amount of the position control cylinder, the slab width, the slab surface position, or the slab thickness is actually measured on the entrance side and the exit side of the light pressure roll to enter and exit. Calculate the actual slab reduction from the side slab shape difference, and if there is a difference between that value and the target reduction to improve the slab internal quality, change the rod movement amount and if it approaches the target reduction amount , It is possible to secure an appropriate reduction amount.

Sixth, when setting the amount of rod movement of the position control cylinder, the amount of withdrawal movement of the slab per unit time is measured on the entrance and exit sides of the light pressure roll, and the slab is determined from the measured values. Obtain the elongation of the slab due to the reduction, obtain the actual reduction of the slab from the relational expression of the elongation and the change of the slab thickness, there is a difference between that value and the target reduction to improve the slab internal quality In this case, if the rod movement amount is changed to approach the target reduction amount, an appropriate reduction amount can be secured.

Further, in this method, when the slab is reduced by a multi-stage light reduction roll, the slab is drawn out per unit time on the light reduction roll entrance side and the discharge side regardless of which light reduction roll reduces the slab. Since there is a difference in the amount, the reduction amount applied to the slab without response delay can be obtained, and the slab width, the slab surface position, or the slab thickness is measured on the light reduction roll entrance and exit sides, It is possible to eliminate a response delay inevitably occurring when the actual reduction of the slab is obtained from those results.

According to the method of the present invention, a light reduction roll is disposed near the end of solidification of a continuous cast slab, a position control cylinder is provided for each light reduction roll bearing, and the roll reduction amount is controlled to achieve a desired casting. A cylinder position reference point control means and a cylinder position reference point setting means for at least once bringing the light reduction roll into contact with the cast slab or once pressing the light reduction device for obtaining the single reduction amount, and a slab surface position on the light reduction roll entry side. Or means for actually measuring the slab thickness, means for obtaining the target total reduction from casting information, etc., means for obtaining the slab actual reduction, means for correcting the target total reduction by the slab actual reduction, and cylinder Can be performed by an apparatus equipped with a means for calculating and setting the target position of the slab. Piece Variation of the surface position can be realized highly accurate soft reduction control with a correction function for the variations in slab deformation resistance.

[0029]

An embodiment of the present invention will be described below with reference to FIG.

In the present invention, the number of stages of the light reduction rolls is not particularly limited, and the number of stages may be one or more. FIG. 1 shows an example in which a pair of upper and lower light reduction rolls are arranged in three stages. Slab 1
The lower rolls 21, 22, 23 are arranged on the lower and upper surfaces of the cylinder, and the upper rolls are cylinders 31, 32, 33 for position control.
And the position control cylinders 31, 32, 33
Is fixed to the light reduction segment 10 and the reduction force of the position control cylinders 31, 32, 33 is applied to the slab 1 to control the cylinder position to obtain a desired reduction amount of the slab.

The rod movement amounts of the position control cylinders 31, 32, and 33 are measured by cylinder position meters 41, 42, and 43, and converted into continuous cylinder position signals by cylinder position converters 51, 52, and 53. 61, 62, 6
Enter 3 The cylinder target position is input to each of the controllers 61, 62, 63 as a set value from each cylinder target position calculation setting unit 103, and an operation signal calculated so as to match the cylinder position signal with the cylinder target position is provided by the hydraulic solenoid valve 71. , 72, 73. Hydraulic solenoid valve 7
1, 72 and 73 drive the position control cylinders 31, 32 and 33 in accordance with the input operation signals, but may use servo valves or proportional control valves. In addition, as long as the position control cylinders 31, 32, 33 can be driven, not only hydraulic equipment but also pneumatic or electric operating equipment may be used.

It is important to set a reference point for the cylinder position to obtain a desired rolling reduction. That is, if the surface position of the slab before reduction facing the light reduction roll is set as the reference point, the rod movement amount of each cylinder itself becomes a value close to the desired reduction amount, and further, the deflection of the segment and the roll, the amount of backlash is corrected. Then, if the rod movement amount of each cylinder is set, a desired reduction amount can be obtained with high accuracy.

In this embodiment, before starting the reduction of the slab 1, the hydraulic solenoid valve 71,
Rolls 2 and 3 on the surface of the slab 1
Rolls 21, 22, 23 on the surface of the slab 1 to the extent that the cylinder position at the time of contact is used as a reference point, or to the extent that mechanical play is eliminated.
Is once pressed, and the cylinder position at that time is set as a reference point. The determination of the contact or pressing time of the light reduction rolls 21, 22, and 23 is performed by the reference setting device 105. The determination is performed by capturing the time when the change of each input cylinder position signal becomes substantially zero during the reduction, Cylinder position converter 5
A zero reset signal is issued to 1, 52 and 53 to instantly replace the cylinder position signal with zero. After that,
The position signal of each cylinder is indicated by a value with the slab surface before the start of rolling down as a reference point. In this way, the cylinder position signal is reset to zero as it includes all the changes in the actual slab thickness, the roll wear, and the play of the rolling down mechanism depending on the casting site, so that the correction is automatically made, and each cylinder set after that The rod movement amount contributes to the reduction of the cast slab. Furthermore, if the set value of the rod movement amount of each cylinder is corrected by calculating the deflection of the segment frame and the roll, a desired reduction amount can be obtained with high accuracy.

The rolling condition calculation / setting unit 100 calculates the total amount of rolling, the number of rolling, the number of rolling, and the like based on the casting information 2 such as steel type (component composition), size (width, thickness), casting speed, slab temperature, and segment opening. Roll No. Is calculated and the total reduction amount is calculated via the total reduction amount correction calculator 101,
Roll No. Is set directly in the lower cylinder target position calculation setting unit 103. Each cylinder target position calculation setting device 103 sets the total roll amount, the number of rolls, and the leading roll No. Calculate the rod movement amount of each cylinder to obtain the desired reduction amount according to the above formula, and set it for each cylinder. For example, the total reduction amount is 2 mm, the number of reductions is 2,
Roll No. Is 22, the target position of the cylinder of the light reduction roll 21 is 0 mm,
Is set to 1 mm, and the cylinder target position of the light pressure roll 23 is set to 2 mm.

Since the position signal of each cylinder uses the slab surface position before the start of rolling down as the reference point by the zero reset function of the reference point setting unit 105, the thickness of the slab on the light roll side of the roll changes and the zero reset point If the slab surface position is different from the slab surface, the actual slab reduction will change with the slab thickness variation while keeping the rod position of each cylinder fixed, and stable and good quality cannot be secured. .
Therefore, if the surface position or thickness of the cast slab on the light reduction roll entry side is actually measured and the target cylinder position is preliminarily compensated by each cylinder target position calculation setter 103 according to the measured value, the appropriate reduction amount can be given. it can.

Further, when the actual slab reduction amount fluctuates due to variations in slab deformation resistance, etc., the slab width, the slab surface position, and the slab thickness are measured on the light pressure reduction roll entrance and exit sides.
From these results, the actual reduction of the slab can be determined.
For example, an entry-side thickness or surface position meter 81 is provided on the entry side of the light reduction roll 21 and an exit-side thickness or surface position meter 82 is provided on the exit side of the light reduction roll 23. Of the slab actual reduction amount, or an entry side slab speedometer 91 is provided on the light reduction roll entry side and an exit side slab speedometer 92 is provided on the exit side. The elongation percentage is determined from the difference between the measured values on the side and the delivery side, and the actual reduction amount of the slab can be determined by the reduction amount calculator 102 from the relational expression between the elongation percentage and the reduction amount.

The method of calculating the elongation and the actual reduction of the slab is given by Equation 1. Incoming slab speed MR ₀ , outgoing slab speed MR
_{1. The} elongation percentage was ε, the actual reduction of the slab was Δd, and the calculation constants determined depending on the steel type were a, b, and c.

[0038]

１ = ((MR ₁ −MR ₀ ) / MR ₀ ) × 100% Δd = aε ² + bε + c

If there is a difference between the determined actual slab reduction amount and the target reduction amount, the cylinder target position is changed by the total reduction amount correction calculator 101, and if the cylinder reduction position approaches the target reduction amount, the cylinder is stabilized without response delay. As a result, an appropriate reduction amount can be secured with high accuracy.

In the comparative example, according to the method described in Japanese Patent Application Laid-Open No. 5-8004, the rod movement amount of the cylinder is calculated by adding the target value of the slab reduction and the predicted value of the frame deformation and the predicted value of the roll deformation of the lightly reduced segment. Was set. Before casting, the degree of light rolling segment opening corresponding to the thickness of the slab under non-light rolling was set, and the cylinder position at this time was set as a reference point.

Both the examples and the comparative examples were carried out using S45C equivalent steel having the composition shown in Table 1. Table 2 shows the correspondence between the examples and the present invention, and Table 3 shows the casting conditions and the light reduction conditions. Basically, the conditions other than the method of controlling the reduction amount were the same. The low pressure rolls were nine stages of 400 mm upper rolls installed in the horizontal part near the end of solidification.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

Table 4 shows the control accuracy and quality of the actual slab reduction. The control accuracy of the actual slab reduction is expressed by the difference between the target reduction and the actual slab reduction. EP rating) and internal crack rating evaluated by sulfur print (SP) of the slab longitudinal section. EP
The larger the rating and the number of internal cracks are, the worse the center segregation or internal cracking is.

[0046]

[Table 4]

As is clear from Table 4, the control accuracy of the actual reduction of the slab and the quality were improved in the example compared to the comparative example. In particular, Example 8 was remarkable.

[0048]

According to the present invention, the variation in the effect of improving the internal quality and the occurrence of internal cracks due to the variation in the reduction amount can be significantly improved, and a cast slab having an excellent internal quality can be stably manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cast piece 2 Casting information 10 Light reduction segment 21, 22, 23 Light reduction roll 31, 32, 33 Position control cylinder 41, 42, 43 Cylinder position meter 51, 52, 53 Cylinder position converter 61, 62, 63 Adjustment Total 71, 72, 73 Hydraulic solenoid valve 81 Inlet thickness or surface position meter 82 Outlet thickness or surface position meter 91 Inlet slab speedometer 92 Outlet slab speedometer 93 Elongation rate calculator 100 Rolling condition calculation setter Reference Signs List 101 Total reduction amount correction calculator 102 Reduction amount calculator 103 Each cylinder target position calculation setting device 104 Cylinder position reference point control device 105 Reference point setting device

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mitsuru Nikaido 12 Nakamachi, Muroran-shi, Hokkaido Inside Nippon Steel Corporation Muroran Works (56) References JP-A-1-202350 (JP, A) JP-A-62 JP-A-5-240620 (JP, A) JP-A-5-237620 (JP, A) JP-A-1-91945 (JP, A) JP-A-62-212048 (JP, A) JP-A-5-8004 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B22D 11/20 B22D 11/128 350 B22D 11/16 104

Claims (6)

(57) [Claims] 1. A method for controlling the amount of reduction of a light reduction roll by a position control cylinder attached to a bearing of a light reduction roll disposed near the end of solidification of a continuous cast slab. A method for controlling a light reduction amount in continuous casting, wherein the cylinder is once pressed to one side to the extent that mechanical backlash is killed, and a cylinder target position for obtaining a desired reduction amount is set using the cylinder position at that time as a reference point. 2. A measuring the slab surface position or slab thickness of soft reduction rolls entry side, soft reduction in the continuous casting according to claim 1 Symbol placement and corrects the cylinder target position according to the value Quantity control method. 3. actually measured slab surface position or slab thickness of soft reduction roll exit side, soft reduction in the continuous casting according to claim 1 Symbol placement and corrects the cylinder target position according to the value Quantity control method. 4. A slab surface position, a slab thickness, or a slab width is actually measured on a light reduction roll entrance side and an exit side, and an actual slab reduction amount is determined from a difference in the slab shape on the entrance and exit sides. soft reduction rate control method in the continuous casting according to claim 1 Symbol placement and corrects the cylinder target position according to the difference of the single actual pressure amount and the predetermined pressure under volume. 5. The amount of drawing movement of the slab per unit time is measured on the entrance side and the exit side of the roll under light reduction, and the elongation percentage of the slab due to the slab reduction is determined from both measured values. determine the actual reduction ratio, soft reduction rate control method in the continuous casting according to claim 1 Symbol placement and corrects the cylinder target position according to the difference between the template piece actual reduction ratio and a predetermined pressure under volume. 6. A light cast disposed near the end of solidification of a continuously cast slab.
With the position control cylinder attached to the rolling roll bearing
In the method of controlling the amount of reduction of the light reduction roll,
The light pressure roll is once brought into contact with the slab surface,
A system to obtain the desired amount of reduction using the cylinder position of the point as a reference point.
Set the target position of the cylinder and enter the roll
Measures the amount of drawing movement per unit time of the slab on the outlet side
Then, the elongation percentage of the slab due to the slab reduction from both measured values,
The actual reduction of the slab is determined from the elongation, and the actual reduction of the slab is determined.
Correct the cylinder target position according to the difference from the constant pressure reduction amount
A method for controlling a light reduction amount in continuous casting.