JPS58184053A - Method for controlling bending of roll of continuous casting machine - Google Patents

Abstract

PURPOSE:To obtain an ingot having uniform quality without giving any abnormal fluctuation in stress to the ingot, by detecting the fluctuation in the displacement of support rolls for the ingot, etc. and correcting the bending of the rolls in the direction where the rate and period of bending of the rolls are made uniform. CONSTITUTION:Displacement meters 1, 2 for the rear surfaces of support rolls 8, 9 for an ingot of a continuous casting machine which detect the bending of said rolls, load cells 4, 5, 6, 7 which measure the reaction in roll chock parts, a displacement meter 3 between the roll chocks which measures the fluctuation in the gap between the roll chocks, and a target 3' thereof, etc. are provided to detect the fluctuation in stress, the fluctuation in displacememnt or the rate relating to these fluctuations owing to the bending of the rolls. When the detected values exceed set values, cooling water is sprayed from cooling water headers 12, 13 for correcting upper and lower rolls to the projecting parts of the rolls 8, 9 during the time when the recesses of said rolls are in contact with the ingot 14 under drawing. The bending of the rolls is thus corrected and the gap between the rolls in the axial direction of the rolls is made roughly constant.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides continuous casting of molten metal in which the upper roll curve 9 and the lower roll curve of the slab support roll have different bending amounts and curves υ.
The present invention relates to a bending control method for correcting curves with different periods.

As is well known, in continuous casting, the molten metal injected into the mold is cooled by the caster 11 and forms a certain solidified shell, and then is drawn out while being cooled within a group of slab support rolls, and after completely solidified, the molten metal is poured into a mold. cut to length.

In such continuous casting operations, from the slab support roll,
Controlling the pressure applied to the slab is particularly effective in areas where there are still unsolidified parts inside the slab, which can prevent partial thickening and segregation of the slab.
This is extremely important in terms of slab quality control in relation to the occurrence of center cracks, etc.

Conventionally, the pressure applied to the slab from the slab supporting rolls is controlled by controlling the distance between a pair of opposing rolls to a certain constant value (hereinafter referred to as the positioning control method), or by using a movable roll within the pair of rolls. A method in which the pressing force applied to a non-fixed roll is controlled to a constant value (hereinafter referred to as a constant pressure control method) is generally used. When controlling the pressure of slabs like this, if there is no roll bending, it is possible to control the pressure uniformly in the roll axis direction, that is, in the width direction of the slab, but if there are roll bends, it is possible to control the pressure uniformly in the direction of the roll axis, that is, in the slab width direction. The pressure distribution in the width direction of the slab is not constant, and when the slab comes into contact with the convex side of the roll bend, the pressure applied to the center of the slab becomes excessive. If the above condition occurs, especially in areas where there are unsolidified parts inside the slab, the interaction with the bulging may cause center cracking or center segregation. There was a problem that partial concentration occurred. If the father roll and the lower roll are bent independently, for example, if the slab is caught between the upper and lower rolls and the drawing speed is reduced to a short stop, the upper roll will bend upwards when viewed from the surface of the slab, and the lower roll will bend. It should not be bent downward when viewed from one side.Afterwards, when drawing starts, the upper and lower rolls have a 180-degree difference in cycle.In other words, when the lower roll bends the convex portion upward (in the direction of the slab surface), the upper roll The convex part is located downward (in the direction of the slab surface), and the slab is periodically pressed down by the convex sides of the upper and lower rolls.The concave part reduces the pressing force of the slab. In order to prevent such a situation from occurring, it is necessary to control the bending of the upper and lower rolls so that both rolls are not bent. The above control method has already been filed as Japanese Patent Application No. 55-13870, but as a result of further studies on various practical control methods, the inventors determined that the curve υ period of the upper roll and lower roll Even if the rolls are bent, if the gears and f between the rolls are approximately uniform in the axial direction of the rolls, the purpose can be achieved without causing abnormal stress fluctuations to the slab. It was found that it is possible to obtain a slab with good internal structure.

The present invention detects the discrepancy signal in the amount and cycle of the upper roll and lower roll during drawing of the slab during the above-mentioned point Kf111, and detects the discrepancy signal in the amount and cycle of the upper roll and lower roll, and rolls the roll before and after the roll-related gear, f, due to the roll bending is almost maximum. To the roll water cooling installed outside.

By water-cooling one or both of the upper roll and lower roll with constant tying, the bends are corrected, and as a result, the amount and period of bending of the upper roll and lower roll are roughly adjusted. By keeping the gap gag almost constant over the entire roll axial direction regardless of roll rotation, the pressure applied to the slab during drawing is reduced to F! ! It is controlled so that it is uniform.

The invention will now be explained in more detail with reference to embodiments shown in the drawings. FIG. 1 shows the arrangement of a pair of opposing rolls and the arrangement of a roll bending detection sensor. In FIG. 1, 1 is a roll back displacement needle that detects a change in the upper roll's 80 bends, and 2 is a roll back displacement needle that detects a change in the lower roll's 90 bends. Also, 4, 5, 6, 7 is Rollch,
It is a device that measures the reaction force of each lower arm and puller with a load cell attached to the shoulder.The outputs of both are almost the same, and it is possible to use one as a representative. 1
2.13 is a water-cooled header for roll straightening to control the bending of the roll, 3 is a roll chute 1, a roll chute for measuring gag fluctuation, and a gag displacement needle, and 3' is a roll chute for 3. Upper roll 8 showing the target of the inter-displacement needle
If the lower roll 9 is bent, or if the lower roll 9 is bent, or if both are bent, when each roll generates a trigonometric stress or displacement change as it rotates, the diameter of each of the upper and lower rolls will change. Since they are almost the same, the output due to roll rotation is the roll bending K due to roll rotation of the lower roll.
Even if the phase of change in stress or displacement due to roll rotation of the upper roll is different from the phase of change in stress or displacement due to roll bending K due to roll rotation of the upper roll, the output of load cell 465.617
．． Each output of the distance displacement meter 3 is combined into one trigonometric function output and changes. The i-le back displacement meters 1 and 2 produce bending fluctuation outputs as the rolls rotate corresponding to the bends of the upper roll 8 and lower roll 9, respectively, and the sum of the displacement needles 1 and 26 output fluctuation values is the roll cho, The fluctuation value is approximately equivalent to the fluctuation value of the roll gap displacement meter 3 (hereinafter referred to as the roll gap displacement output). As mentioned above, each load cell 4, 5
, 6.7 and the inter-roll gear, the fluctuation of the displacement output is the result of combining the bending of the upper roll and the lower roll, and the form of the combined output is the same for both. An object of the present invention is to correct and control roll bending so that stress fluctuations or displacement fluctuations as a result of cough synthesis do not occur during slab drawing.

In the following, although it is possible to control equally with a load cell or with a displacement needle, the purpose is to equalize the stress fluctuations caused by roll bending on the slab, so the case using a load cell will be explained in more detail in 9. .

Figure 2 shows the stress fluctuation of the load torque output attached to the roll chock as the roll rotates. The point where the combined reaction force of the upper roll and lower roll is maximum, that is, the convex side of the equivalent maximum roll bending (hereinafter, the combined reaction force due to the bending of the upper roll and lower roll is referred to as equivalent roll bending) is on the slab surface. When touching t1 (t'l@t
When the peak point P snow (P's s v' snow...) is on the convex side of the equivalent roll curve] or on the opposite side of the slab, tl ( t/, s t
It corresponds to the roll reaction force at period T (T', T'...), and corresponds to the time required for one rotation of the roll or one rotation of the roll in a conventional manner. be. Also, the swing width P (P', P'...) is the roll reaction force when the convex side of the equivalent roll bends or is in contact with the slab surface, and the roll reaction force when the convex side of the equivalent roll -b is on the opposite side to the slab surface. This corresponds to the difference in roll reaction force when &C exists, and this corresponds to the magnitude of the resultant roll bending due to K of the upper and lower rolls.

On the other hand, the rotation angle of the roll depends on the slab drawing speed! , when the roll diameter is D, the rotation angle gh can be expressed as follows. Therefore, the starting point of the roll rotation angle is set as the aging time shown in Fig. 2 (t's et t%...), that is, when the convex side of the equivalent roll bend contacts the slab, and (1)
Cooling water is passed to externally cool the rolls during the time period when the rotation angle obtained by the formula is 1800 degrees θ (where θ is the range of roll rotation angles in which water is passed through to the roll water cooling, which will be described later). do. During this period, the equivalent roll bending t
! Since i'1: and II are on the casting side, the concave side expands due to heat transfer from the slab, and at this time, the convex side contracts due to external water cooling. By repeating this every time the roll rotates, stress roll bending will be corrected (at this time, external water cooling may be performed on the upper roll and lower roll at the same time with the same signal, and stress fluctuations due to equivalent bending) is the load gear, and when the fluctuation between ! exceeds a certain value, and when a convex part comes to a certain range on the opposite side of the slab, cooling the upper and lower rolls with water at the same time will cause the bending to be lower than when controlling the bending of the lower and upper rolls individually. and twice as fast *('
It is possible to make the fluctuation below a certain value by controlling the number of times A). If care is not taken to prevent the external cooling water of the upper roll from coming into contact with the slab, it may cause uneven cooling of the slab and cause quality problems, so in practice straightening control is performed only on the lower roll.)

Hereinafter, the present invention will be explained in the case of controlling only the lower roll.

Here, if the angle θ is 90° or less, there is a one-sheet straightening effect, but in practical terms, the straightening efficiency is higher when it is 45° or less. In other words, it is effective to pass the cooling water while the convex side of the equivalent roll bend is within an angular range of 90° (A=180° +45° in rotation angle) on the opposite side of the slab. If the stress fluctuation is controlled several times in the manner described above until it falls below a certain value, as a result, the amount and period of the lower roll's curvature will become stronger and the amount and period of the upper roll's curvature will become stronger as the roll rotates. This reduces the stress fluctuations caused by the rotation of the rolls, and the gear between the rolls does not fluctuate as the rolls rotate, ensuring good quality by keeping the stress fluctuations caused by roll bending in the slab internal to a certain value or less. Also, if you control too much, it will bend in the opposite direction, so either adjust the water amount according to the equivalent mb amount, or change the cooling angle range while keeping the water amount constant, or By appropriately selecting the minimum shortness of the neatness ability and repeating this several times, the control is controlled within the target value, and when the target value is exceeded, the control is resumed. Moreover, this control result is a result of controlling not only the thermal deformation of the roll but also the elastic tower electric current due to the reaction force of the roll. Next, the control flow shown in FIG. 3 will be explained with reference to FIG. 3 regarding the actual operation.

FIG. 3 shows an example of the control flow for one role. The amplitude P is detected from the output of the load cell every time the roll rotates, and the output of the load cell is performed from when the amplitude P exceeds a predetermined constant value (target value) until the roll makes one rotation (t is about 2 to 5). 1 -1 Ps (or 1
m) to calculate i periods T, and from this calculate the average period Ta. This average cycle Taw is used to determine the starting point (reset point) when calculating the roll rotation angle when stopping and restarting water flow for each roll rotation thereafter. On the other hand, the roll rotation angle A is calculated using the above equation (1) for each of the average periods TaV·, using the peak point pit detection time of the first rotation as the first starting point. When the calculated roll rotation angle fA reaches the water flow start point (=180'-#), the main water flow solenoid valve 15 is turned on to flow the water to the lower roll straightening water cooling to the water cooling shown in FIG. Cool the water roll externally. When the roll rotation angle A reaches the water flow stop point (=180010), water cooling is started and the water flow solenoid valve 15 is turned off to stop cooling.

This operation is repeated every time the roll rotates until the isometric roll curvature becomes less than a certain value (the swing width P is less than a certain value).

In this case, the control method is to control when a certain value is exceeded, and the ability to correct with one water cooling is done by making the minimum unit small, so that it will not be possible to bend in the opposite direction with one water cooling. The amount of water and water cooling angle should be adjusted accordingly.

The above control 70-) can be applied to each roll that requires straightening, but if there are many rolls, the roll with the largest equivalent roll is selected from the output of the load cell attached to each roll. Equivalent - If you apply the above water cooling control to the largest roll that bends and then repeat the same process at regular intervals, the calculation device in the control system will be shared by one device, and the device cost will be reduced. It may be configured to reduce the amount. However, the control in the above explanation can be performed even if a load cell is attached to either of the upper or lower rolls.Although one or more load cell outputs may be used to determine isometric roll bending, it is not practical. From the point of view of cost etc., it is sufficient to install one unit on one side of the lower roll.

Also, when measuring and controlling the displacement between rolls, it is practical to use 1
Both sites of paired rolls 1. It is possible to detect and control isometric roll curvature by measuring the displacement of the roll. For the drive roll, it is also possible to detect changes in the drive roll drive current or rotational torque, and to detect isometric roll deformation, but it is preferable to manage and control the stress exerted on the slab. For this purpose, it is preferable to use a load cell.

As described above, in the present invention, the combined isometric bending of the upper roll bending and lower roll bending of the supporting roll is detected during drawing of the slab, and one stub of force is set at a constant value ζ. When the convex side of the four-rule curve is away from the slab, water is temporarily passed through the roll water-cooling header installed outside the roll to straighten the roll automatically, and while the slab is being pulled out. The excellent effect of being able to always control the pressure fluctuations applied to the slab from the rolls to below a certain level can be achieved. Furthermore, by sticking, the stress fluctuations that occur as the roll rotates can be kept below a certain value in either the correction of one roll bend or the correction of roll bends on both sides.

[Brief explanation of the drawing]

Fig. 1 is a front view showing an example of an embodiment of the present invention, and shows a peripheral device of a pair of slab supporting rolls, Fig. 2 is a diagram showing an example of the waveform of an output signal of a load cell provided on the rolls, and Fig. The figure is 1
FIG. 3 is a diagram showing a water cooling control flow for two rolls. 1, 2:, Roll back displacement meter 3: Roll tip W, Link displacement needle 3': Roll tip displacement meter Tarr, To 4.5, 6,
7: Load cell 8: Upper roll 9: Lower roll 10. 11: Hydraulic cylinder 12: Upper roll straightening water cooling header 13 Two lower roll candles to water cooling, Dar 14: Slab 15. 16: To water cooling, Goo water flow solenoid valve Fig. 1 Fig. 2 □ Time Fig. 3 Continuation of page 1 0 Inventor: Hiroshi Nomura 0 Inventor: Masayuki Kobayashi Kimitsu type Kimitsu 1 Nippon Steel Corporation Kimitsu Works

Claims (1)

[Claims] When stress fluctuations or displacement fluctuations due to roll bending of a pair of opposing rolls or amounts related to the above fluctuations are detected during slab support rolls of a continuous casting machine and exceed the set value. The roll bending is corrected so that the amount of bending and the bending period of the bulk rolls are made equal, and the gag between the rolls in the roll axis direction is kept almost constant regardless of the rotation of the rolls, thereby making the stress fluctuation or displacement fluctuation that occurs in the slab constant. A method for controlling roll bending in a continuous casting machine, which is characterized by keeping the bending below a certain value.