JPH04351250A - Method for continuously casting strip - Google Patents

Abstract

PURPOSE:To prevent the development of the pattern caused by uneven cooling by measuring surface temp. distribution in a strip continuously coming out in the parallel direction to roll axis and controlling revolution speed of rolls so as to be in the setting range. CONSTITUTION:Molten metal in pouring basin 2 is cooled with a pair of the rolls 1a, 1b to continuously cast the strip 3. The surface temp. of strip 3 is detected with a camera 8 and converted into the digital signal of the temp. with a signal-trestment part 9. This digital signal is received by a control circuit 21 and compared with the setting value and the control circuit instructs a speed controller 22 so as to make slow revolution to a motor 18 in the case it is higher and to make quick revolution to the motor 18 in the case it is lower. Just after starting the casting, the pressing load of the rolls 1a, 1b is measured with load cells 14, 17 and the motor 18 is controlled so that the pressing load becomes the prescribed value or lower, and after becoming the stationry condition, this is switched to the control keeping the surface temp. of strip 3. The strip 3 without having uneven cooling pattern can be produced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in a twin-roll continuous casting method for continuously casting thin plates directly from molten metal.

0002

[Prior Art] A pair of internal cooling rolls rotating in opposite directions are arranged facing each other in parallel with an appropriate gap, and a pool is formed on the circumferential surface of the rolls above this gap (roll gap). BACKGROUND OF THE INVENTION A twin-roll continuous casting machine is known in which hot water in a pool is continuously cast into a thin plate through a gap between the rolls while being cooled by the circumferential surface of a rotating roll. Proposals have also been made to apply such twin-roll continuous casting machines to continuous casting of steel to directly manufacture thin steel sheets from molten steel, and numerous reports have been published on improvements to equipment and operating methods for this purpose. ing.

0003]

[Problems to be Solved by the Invention] In twin-roll continuous casting machines, it is inevitable that the shell solidified on the circumferential surface of the rolls will have some degree of uneven thickness. For this reason, when both shells formed on the surfaces of the pair of rolls pass through the roll gap, some parts come into close contact with the rolls and others do not. Furthermore, if unevenness occurs on the roll surface due to thermal expansion or the like, the roll gap will not be constant in the width direction and circumferential direction of the roll, and this will also cause non-uniformity in the degree of adhesion between the thin plate to be cast and the roll. If such a difference in the degree of adhesion occurs in the width direction or longitudinal direction of the thin plate, the thin plate will be strongly cooled by the rolls in the areas where there is strong adhesion, and the areas where it is not tightly cooled will be slowly cooled. This cooling unevenness appears as a cooling uneven pattern on the surface of the thin plate. The uneven cooling pattern that occurs in the thin slab remains as uneven gloss on the surface of the cold-rolled sheet after annealing, pickling, and cold rolling, which poses a quality problem.

[0004] This uneven cooling pattern becomes more noticeable as the pressure load (pressure applied from the roll surface to the solidified shell passing through the roll gap) increases, and the unevenness of gloss in cold-rolled sheets and the like also becomes more noticeable. Previous studies have revealed that this uneven cooling pattern can be reduced by reducing the crimping load. Based on this knowledge, the crimping load is controlled (the crimping load can be controlled by the roll rotation speed).
Attempts were made to prevent uneven cooling, but it was found that the crimp load must be controlled to a very small value in order to completely prevent uneven gloss that occurs in cold-rolled sheets. However, even if it were possible to control the crimping load to a very small value, in this case, the plate would pass through the roll gap with a large amount of unsolidified molten metal remaining in the center of the plate thickness. Problems arise in that troubles such as swelling and breakouts occur. This is a drawback of the method of controlling the roll rotation speed using only the crimping load as a management index.

[0005] As a solution to the problem that the edge of the plate breaks out when the crimp load is reduced to near zero, there is a method of making the thickness of both ends of the thin plate to be cast thinner than the thickness of the center part. be. This method is effective in suppressing breakout at the edge of the sheet, but when the crimp load is small, the crimp load is applied only to both ends of the sheet, so the crimp load at the center of the sheet, which is important for control, is reduced. There is a problem that accurate detection is difficult. The present invention aims to solve this problem in the twin-roll continuous sheet casting method.

0006]

[Means for solving the problem] Molten metal is supplied to a pool formed above a pair of internal cooling rolls that rotate in opposite directions, and the hot water in the pool is passed through a gap between the pair of rolls to form a thin sheet. In order to solve the above-mentioned problems in a thin plate continuous casting method in which continuous casting is performed, the present invention has the following features: Measurement is carried out in a direction parallel to the roll axis, and the roll rotation speed is controlled so that this surface temperature distribution is within a set range. The surface temperature distribution of the thin plate that continuously emerges from the gap between the roll pairs is measured in a direction parallel to the roll axis at a predetermined position from the gap, and immediately after the start of casting, the pressure bonding load is kept below a predetermined value. After controlling the rotational speed of the roll and after the pressure bonding load becomes less than a predetermined value, the roll rotational speed is controlled so that the surface temperature distribution is within a predetermined range;
) At the same time, measure the pressure bonding load that the thin plate receives from both rolls, and at the same time measure the surface temperature distribution of the thin plate continuously emerging from the gap between the pair of rolls at a predetermined position from the gap in a direction parallel to the roll axis. The method is characterized in that the rotational speed of the rolls is controlled so that the maximum temperature of the thin plate surface is below a predetermined value and the crimping load is close to the preset value.

In cases (1) and (2), continuous casting can be performed so that the thickness of both ends of the thin plate is thinner than the thickness of the center of the thin plate. In the case of (3), the set value of the crimp load means a crimp load value that does not cause uneven gloss on the cold-rolled sheet after the thin sheet is cold-rolled.

[Detailed Description of the Invention] The present inventors cast steel by changing the crimp load applied to the plate during casting in a twin-roll continuous casting machine, and obtained plates with various levels of uneven cooling patterns. , the level of the uneven cooling pattern of this as-cast plate is ranked A, B, C, and D in the order of the crimp load and the clear cooling uneven pattern.
classified into. Then, the thin plates with each level of uneven cooling pattern were annealed and pickled in the laboratory, and then cold rolled. As a result of investigating the relationship between the gloss unevenness observed on the surface of the sheet after cold rolling and the level A to D of the cooling unevenness pattern observed on the as-cast thin sheet,
It was confirmed that when the cooling uneven pattern level was set to D, uneven gloss did not occur in the cold-rolled sheet.

On the other hand, the surface temperature of the thin plate continuously coming out from the rolls was measured using thermography at a predetermined distance from the roll gap, and the surface temperature distribution and the uneven cooling pattern observed on the thin plate surface after casting were measured. We investigated the relationship between As a result, it was found that the degree of uneven cooling pattern corresponds well to the unevenness of the thin plate surface temperature. It was also found that when the pressure bonding load during casting is large, the surface temperature of the thin plate decreases overall, and at the same time, the distribution of the surface temperature fluctuates (the unevenness becomes significant) and the uneven cooling pattern becomes clearer.

[0010] Figure 1 shows the process of casting a thin plate of SUS304 stainless steel using a twin-roll continuous casting machine of the embodiment described below.
The results show the results of continuously measuring the maximum and minimum temperatures in the sheet width direction at a position 320 mm below the roll gap, and investigating the relationship between this temperature difference and the uneven cooling pattern of the thin sheet. From FIG. 1, it can be seen that the smaller the temperature difference is, the lighter the uneven cooling pattern becomes, and when the minimum temperature is 1270° C. or higher, the above-mentioned level D (an uneven cooling pattern that does not cause uneven gloss after cold rolling) is obtained. However, the maximum temperature is 1400
When the temperature exceeded ℃, cracks and blisters were observed on the surface of the plate after casting. This is thought to be due to the fact that the plate surface temperature rose to the brittle region, causing cracks and blisters. This result shows that SUS
In the case of 304, the surface temperature 320mm below the roll gap must be such that the minimum temperature is 1270℃ or higher and the maximum temperature is 1270℃ or higher.
This shows that if the casting conditions are controlled to be within the range of 400°C, it is possible to obtain a plate with no defects such as cracks or blisters, and with a slight uneven cooling pattern that does not result in uneven gloss.

[0011] Similarly, for other steel types, it is possible to determine the appropriate control temperature range, that is, the maximum temperature at which cracks or blisters do not occur, and the minimum temperature at which uneven gloss due to uneven cooling patterns does not occur after cold rolling. . For example, under the above measurement conditions, the highest temperature of SUS309S was 1350°C and the lowest temperature was 1250°C.

As described above, the surface temperature (temperature difference) of the thin plate directly under the roll gap, which retains the influence of the temperature during crimping while passing through the roll gap, is a control factor, and this surface temperature difference is controlled within a predetermined range. It was discovered that by manipulating the casting conditions to achieve the desired results, it is possible to stably obtain plates without uneven cooling patterns and defects such as cracks and blisters. Specifically, the control operation of the casting conditions using the detected temperature as a control factor can be performed as follows.

[0013] If the surface temperature in the width direction of the thin sheet is measured at multiple points at a predetermined position immediately after passing through the roll gap and the temperature distribution is determined, the non-uniformity of the adhesion between the thin sheet and the roll can be determined from the temperature distribution. In this case, nonuniformity in temperature in the width direction of the plate can be detected from the temperature distribution at each measurement point, and nonuniformity in the longitudinal direction of the plate can be detected from changes over time at each measurement point. In other words, it is possible to read the two-dimensional temperature distribution of the plate. Fluctuations in this temperature distribution are detected online, and if the fluctuations deviate from the set temperature range, automatic control is implemented to manipulate the casting conditions so that the temperature returns to the set temperature range. As described above, the rotational speed of the rolls may be used as the operational factor for the casting conditions. This is because there is a correlation between the rotational speed of the roll and the crimping load, and a correlation between the crimping load and the surface temperature of the thin plate. For example, if there is a spot on the surface of a thin plate that is insufficiently cooled and the temperature at that spot rises above a predetermined temperature, the roll rotation speed is controlled to slow down to restore the temperature distribution to its normal value. On the other hand, if the cooling is too strong and the minimum temperature falls below the specified temperature,
The temperature distribution is restored to its normal value by controlling the rotation speed of the roll to be faster.

[0014] Furthermore, if the thickness of the plate being cast is relatively thick, breakout is likely to occur, so a means for suppressing breakout is to cast the plate so that the thickness at both ends is thinner than the thickness at the center. However, in such cases, a thin plate with good surface quality can be manufactured by performing the above-mentioned control on the remaining areas excluding the thin parts at both ends of the plate.

On the other hand, since the temperature of the thin plate surface changes rapidly immediately after the start of casting, and the surface temperature measurement position is located below the roll gap point, the information on the thin plate surface temperature is not accurate at the actual cooling point. It will be a little later than that. Therefore, in the case of unsteady conditions immediately after the start of casting,
If control is performed only based on surface temperature measurements from the beginning, control that responds to changes in uneven cooling on the thin plate surface will be delayed, and this will also result in inappropriate roll rotation speed, making it difficult to smoothly transition to steady-state casting. There's a problem. Therefore, in unsteady conditions such as immediately after the start of casting, the crimp load, which is real-time information at the roll gap point, is detected and controlled so that the crimp load is within a predetermined value range.
After the crimping load has decreased to a certain extent and entered a steady state,
In other words, when the crimp load becomes smaller than a predetermined value, switching from control that uses the crimp load as a control factor to control that uses the thin plate surface temperature as a control factor will result in a faster transition to a casting state where uneven cooling patterns do not occur. can. The pressure bonding load can be detected by measuring the pressure applied between the rolls, specifically by using a load cell.

The predetermined value of the crimping load can be determined based on the following criteria. If the crimping load is excessive, the thin plate will cool too much, resulting in uneven cooling patterns. on the other hand,
If the crimping load is too low, the thin plate will not be cooled enough and the surface temperature of the thin plate will become higher than ZST due to heat recovery immediately after it is released from the rolls, causing cracks to occur. Here, ZST is the temperature at which the strength of the thin plate becomes zero (Zero Strength
Temperature). A crimping load at which neither of these phenomena occurs is set as a predetermined value. In other words, in actual control, ZST is determined by high-temperature tensile tests or Greeble tests on the desired steel type.
is determined in advance, and the crimping load is controlled so that the surface temperature of the thin plate due to recuperation does not exceed ZST.

[0017] The control pattern of the roll rotation speed from the unsteady state immediately after the start of casting to the steady casting state, that is, immediately after the start of casting, at the point when the crimping load becomes smaller than a predetermined value, control is changed from control based on the crimping load to control based on the thin plate surface temperature. It is also possible to determine in advance the appropriate rotational speed of the roll corresponding to the process of switching to control for the steel type, and to control this by programming it.

[0018] Furthermore, the roll rotation speed may be controlled by combining the measured value of temperature and the measured value of pressure bonding load. In this case, it is possible to prevent uneven cooling by keeping the maximum temperature on the surface of the thin sheet below a predetermined value and by controlling the crimp load to be close to the set value that is required to prevent uneven gloss after cold-rolling the thin sheet. Cast plates can be obtained.

[0019]

[Example] Figure 2 shows an example of a twin-roll continuous casting machine to which the method of the present invention is applied, in which a pair of internally cooled rolls of the same diameter are arranged facing each other with parallel axes and rotate in opposite directions. A pool 2 of molten metal is formed in contact with the circumferential surfaces of the rolls 1a and 1b, and the molten metal in this pool 2 is cooled on the circumferential surfaces of the pair of rolls 1a and 1b, and is formed on both circumferential surfaces. The solidified shell is continuously cast into a sheet 3 through a roll gap 6. 4a
, 4b indicate side dams for forming a pool 2 on the circumferential surface of the roll pair 1a, 1b. In the illustrated example, both ends of the roll pair 1a, 1b have a stepped portion 5 with a larger diameter than the center, and therefore, the thin plate 3 to be cast is cast so that both edges Y are thinner than the center portion X. . Note that the method of the present invention can also be applied to a twin-roll continuous casting machine without this stepped portion.

In the present invention, in such twin-roll type continuous thin sheet casting, the camera 8 of the thermography device is installed as close as possible to the roll gap 6 to capture the radiant heat from the continuously cast thin sheets. A sensor (InSb) in the camera 8 of the thermography device continuously receives light and converts it into an electromotive force signal.

FIG. 3 is a schematic side view of the twin roll continuous casting machine of FIG. 1, including the roll support mechanism, and FIG. 4 is a schematic plan view of the same. In these figures, 10
a, 10b are roll shafts, and these roll shafts 10a, 1
0b is received by roll chocks 12a and 12b arranged so as to be movable in parallel within the frame 11. A roll gap adjuster 13 is interposed between the roll chocks 12a and 12b, and a load cell 14 is installed between the roll chocks 12a and 12b.
is interposed. In the illustrated example, a cylinder 15 applies pressure from the side of one roll 1b to the side of the other roll 1a. Reference numeral 17 is a load cell that detects the back pressure on the entire pair of rolls using the cylinder 15. Each roll shaft 10 is provided with rotational power from a motor 18.

As mentioned above, the surface temperature of the thin plate is continuously detected by the camera 8, and the signal from the camera 8 is converted into a digital temperature signal in the signal processing section 9 of the thermography device, and is displayed online on the color display 2.
0 in two dimensions, allowing direct monitoring of temperature unevenness on the surface of the thin plate. While directly monitoring the thin plate surface temperature displayed on the display 20, the rotation speed of the motor 18, which is the drive source for the rolls, can be manually controlled so that the thin plate surface temperature is within the set value range. . Further, automatic control can be performed as follows. In addition, in FIGS. 3 and 4, 19 indicates a motor speed pattern generator.

For automatic control, a digital temperature signal from the thermography device is input to the control circuit 21. The control circuit 21 compares the input value with the maximum temperature set value and the minimum temperature set value, and if the temperature deviates from the set value range to a higher temperature, the motor speed control device 22 is sent to slow down the rotation speed of the motor. Give the output signal as,
Conversely, if the temperature deviates from the set value to a lower value, the opposite signal is given.

[0024] In addition to this surface temperature control, crimp load control is used in combination, and as described above, from the unsteady state immediately after the start of casting to the steady state, the roll rotation speed control is switched from crimp load management to thin plate surface temperature management. is preferable, and a flowchart of the logic circuit in this case is shown in FIG. In this embodiment, the surface temperature of the thin plate is continuously measured by the camera 8 of the thermography device, and at the same time, the crimp load is directly measured by the load cells 14, 14' and 17, 17' shown in FIG. Load cell 17, 17'
The detected value P1 obtained from the load cells 14 and 14' is inputted into the crimp load calculator 24, and the calculation of (P1-P2=P3) is sequentially executed to determine the crimp load P3 that the thin plate receives. seek. This P3 can be output to the recorder 25 or the like so that it can be checked from the outside. At the start of unsteady casting when the molten metal level has not yet reached the predetermined height, the casting start operator sets the crimp load value P3.
is monitored, and the rotational speed of the roll is controlled so that P3 is equal to or less than a predetermined value P0 of the crimping load. After controlling P3 to below P0 and casting transition to a steady state, the thin plate surface temperature, which was measured at the same time as the crimp load, is displayed on the display 20.
The method is to monitor the temperature on the screen and control the rotational speed of the rolls so that the surface temperature of the thin plate falls within a predetermined temperature range.

Furthermore, as one aspect of the present invention, both the maximum surface temperature of the thin plate and the pressure bonding load value PD at which uneven gloss does not occur on the cold-rolled plate may be used as management values for roll rotational speed control. Here, the crimp load value PD that does not cause uneven gloss on the cold-rolled sheet is the one that prevents uneven gloss from occurring in sheets that are cast at various crimp load values below the predetermined crimp load value P0, annealed and pickled, and then cold-rolled. The degree is investigated and determined in advance for each type of steel to be cast.

FIG. 6 shows that the roll rotation speed is controlled only by the compression load value in the unsteady state immediately after the start of casting, and after the transition to a steady state, the maximum temperature of the surface temperature of the thin sheet and the uneven gloss of the cold rolled sheet are controlled. A flowchart is shown for the case where the crimping load value does not occur.

As shown in FIG. 1, when the control of the present invention is applied to a casting method in which the thickness of both ends of the plate is made thinner than the thickness of the center part to prevent breakout, The above-mentioned control is performed in the remaining area (Y area) excluding the thin parts (X area) at both ends of the plate.

[Operation example 1 of the method of the present invention] 400mmφ×3
A twin-roll continuous casting machine consisting of 00 mmW copper alloy internal cooling rolls (however, the step part 5 on the roll surface shown in Figure 1)
(continuous casting machine consisting of flat rolls of equal diameter),
500 kg of US304 molten steel was cast. Casting plate thickness is 2.
0mm, and the average casting speed in steady state is 30m/
It was min. The surface temperature in the width direction of the plate at a point extending 320 mm from the roll gap was measured by thermography. Extract the indicated values at 10 points from the width direction temperature distribution,
These were used as management indicators. The control range for the thin plate surface temperature was a maximum temperature of 1,370°C (a margin of 30°C was taken because breakout would occur if it exceeded 1,400°C), and a minimum temperature of 1,270°C.

While monitoring the thermographic output display, the roll drive motor voltage was increased or decreased to control the roll rotation speed so that the surface temperature distribution satisfied the controlled temperature range. As a result, the level of the uneven cooling pattern of the cast thin plate was below D except for the area up to 10 m from the tip. Also, the plate bulges due to non-solidification.
A thin plate with good surface quality was obtained without any cracks or cracks. In addition, the obtained thin plate, except for 10 m from the tip, was annealed and pickled and then cold rolled. As a result, a cold rolled plate with a uniform surface condition without uneven gloss was obtained.

[Example 2 of operation of the method of the present invention] In this example, the roll rotation speed immediately after the start of casting was controlled using the pressure bonding load value detected from the load cell as a management index, as shown in FIG. In other words, in an unsteady state immediately after the start of casting, the roll rotation speed is controlled so that the crimping load is 2.5 kgf/mmW or less, and the crimping load is 2.5 kgf/mmW or less.
After the following conditions were achieved and a steady state was achieved, roll rotation speed control was switched to using the thin plate surface temperature as a management index based on the detection signal from the thermography. Other conditions were the same as in Example 1.

As a result, the lowest temperature of the surface temperature distribution in the width direction of the plate increased from 1270°C to 1370°C earlier than in Example 1.
I was able to keep it within the following range. As a result, the defective area extending from the tip of the thin plate was only 3 meters long. As a result of annealing, pickling, and cold rolling the obtained thin plate except for 3 m from the tip, a thin plate with a uniform surface without uneven gloss was obtained.

[Operation Example 3 of the Invention] In this example, as shown in FIG. 1, a casting method was used in which a roll having stepped portions 5 at both ends was used to make both ends of the thin plate thinner than the center. The thickness of the cast plate at this time was 3.0 mm, and the average roll rotation speed during casting in a steady state was 20 m/min. In addition, the widthwise range for surface temperature measurement was 220 mm, excluding both ends (10 mm/one side) where the thickness of the cast plate was thin. Other conditions were the same as in Example 1. In addition, as in Example 2, in the unsteady state immediately after the start of casting, the roll rotation speed is controlled so that the crimping load is 2.5 kgf/mmW or less, and the crimping load is 2.5 kgf/mmW or less. Once this was achieved, the roll rotation speed was controlled using the surface temperature of the thin plate as a control value.

As a result, although the plate thickness obtained was relatively thick at 3 mm, there was no breakout from the edge of the plate, and the cooling unevenness level was below D except for 3 m from the tip of the plate, which was caused by non-solidification. A thin plate with good surface quality was obtained without any bulges or cracks. 3 from the tip of the obtained board
As a result of annealing and pickling the thin sheet except for up to m, a cold-rolled sheet with a uniform surface condition without uneven gloss was obtained.

[Example 4 of operation of the method of the present invention] Using the same twin-roll continuous caster as in Example 1, 500 kg of SUS304 molten steel was cast. The thickness of the cast plate was 2.0 mm, and the average casting speed in steady state was 30 m/min. The conditions for measuring the temperature distribution on the thin plate surface were also the same as in Example 1. The target value for controlling the surface temperature of the thin plate after transition to a steady state was set at a maximum temperature of 1370°C. On the other hand, the management target value for the crimping load value is 1.0±0.2kg.
f/mmW. The roll rotation speed was controlled so that the maximum temperature of the surface temperature distribution and the crimp load value satisfied the set conditions while monitoring the crimp load value detected by the load cell through the thermograph output display and the computer.

[0035] As a result, the level of the uneven cooling pattern of the cast thin plate was below D except for the area up to 10 m from the tip. In addition, a thin plate with good surface quality was obtained without any bulging or cracking due to unsolidified material. As a result of annealing and pickling the obtained thin plate except for 10 m from the tip, a cold rolled plate with a uniform surface condition without uneven gloss was obtained.

[Comparative Example 1] Using the same twin-roll continuous casting machine as in Example 1, 500 kg of SUS304 molten steel was cast. The thickness of the cast plate was 2.0 mm, and the average casting speed in steady state was 30 m/min, but the roll rotation speed was controlled using only the crimp load value as a management index. In other words, the crimp load value is consistently 2.5k from the start of casting to the end of casting.
The roll rotation speed was controlled to be less than gf/mmW, and the roll rotation speed was not controlled at all using the thin plate surface temperature as a management index.

[0037] As a result, when only the pressure bonding load value was managed, the surface temperature of the thin plate was often below 1270°C, and the uneven cooling pattern level of the thin plate was C or B. As a result of cold rolling after annealing and pickling except for 3 m from the tip of the obtained thin sheet, uneven gloss occurred in the cold rolled sheet.

[Comparative Example 2] 500 kg of SUS304 molten steel was cast using the same twin-roll continuous casting machine as in Comparative Example 1. The thickness of the cast plate was 2.0 mm, and the average casting speed in steady state was 35 m/min. The measurement conditions for the thin plate surface temperature distribution were the same as in Example 1. However, in the first half of casting, the roll rotation speed was controlled using only the maximum temperature on the surface of the thin sheet as an index value, and in the second half of casting, the roll rotation speed was controlled using only the minimum temperature at which the surface of the thin sheet was formed as an index value. In other words, during the first half of casting, the roll rotation speed was controlled to be reduced when the maximum temperature on the sheet surface exceeded 1370°C, but the roll rotation speed was not adjusted even when the sheet surface temperature decreased. . As a result, uneven cooling patterns appeared on the thin plate.

On the other hand, in the latter half of casting, the rotational speed of the rolls was controlled to be increased when the minimum temperature on the surface of the thin sheet fell below 1270°C, but even if the surface temperature of the thin sheet increased, the rotational speed of the rolls was controlled. I didn't. the result,
A breakout occurred and I was unable to cast until the end.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between thin plate surface temperature and uneven cooling pattern.

FIG. 2 is an overall perspective view showing an example of a twin-roll continuous casting apparatus to which the method of the present invention is applied.

FIG. 3 is a schematic side view showing an example of a twin-roll continuous casting apparatus to which the method of the present invention is applied.

FIG. 4 is a schematic plan view showing an example of a twin-roll continuous casting apparatus to which the method of the present invention is applied.

FIG. 5 is a flowchart of a logic circuit for controlling roll rotation speed according to the present invention.

FIG. 6 is a flowchart of a logic circuit for controlling roll rotation speed according to the present invention.

[Explanation of symbols]

1a, 1b Internal cooling roll 2 Water reservoir 3 Thin plates 4a, 4b to be cast Side dam 6 Roll gap 8 Thermography camera 9 Thermography signal processing unit 10
Roll axis 12 Roll chock 13 Roll gap adjuster 14 Load cell 17 Load cell 18 Motor 19 Motor speed pattern generator 20
Display 21 Control circuit 22 Motor rotation speed control device 24 Crimping load calculation device 25 Recorder

Claims (4)

[Claims] [Claim 1] Molten metal is supplied to a pool formed above a pair of internal cooling rolls that rotate in opposite directions, and the hot water in the pool is continuously cast into a thin plate through the gap between the pair of rolls. In the twin-roll continuous thin plate casting method, the surface temperature distribution of the thin plate that continuously emerges from the gap between the pair of rolls is measured in a direction parallel to the roll axis at a predetermined position from the gap, and this surface temperature distribution is within the set range. A thin plate continuous casting method characterized by controlling the roll rotation speed so that the [Claim 2] Molten metal is supplied to a pool formed above a pair of internal cooling rolls that rotate in opposite directions, and the hot water in the pool is continuously cast into a thin plate through the gap between the pair of rolls. In the twin-roll continuous thin plate casting method, the compression load that the thin plate receives from both rolls is measured, and at the same time, the surface temperature distribution of the thin plate continuously emerging from the gap between the rolls at a predetermined position from the gap is measured parallel to the roll axis. Immediately after the start of casting, the rotational speed of the rolls is controlled so that the crimping load is below a predetermined value, and after the crimping load is below the predetermined value, the surface temperature distribution is within the set range. A thin plate continuous casting method characterized by controlling the roll rotation speed. 3. The thin plate continuous casting method according to claim 1, wherein the thin plate is cast so that the thickness at both ends thereof is thinner than the thickness at the center of the thin plate. 4. Molten metal is supplied to a pool formed above a pair of internal cooling rolls that rotate in opposite directions, and the hot water in the pool is continuously cast into a thin plate through a gap between the pair of rolls. In the twin-roll continuous thin plate casting method, the pressure load that the thin plate receives from both rolls is measured, and at the same time the surface temperature distribution of the thin plate continuously emerging from the gap between the rolls at a predetermined position from the gap is measured parallel to the roll axis. A thin plate continuous casting method characterized in that the rotational speed of the rolls is controlled so that the maximum temperature of the thin plate surface is below a predetermined value and the crimping load is close to the set value.