JP2007245168A - Method and apparatus for detecting completion of solidification in continuous casting, and method and apparatus for continuous casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the perfect solidified position of a cast slab through simple constitution. <P>SOLUTION: Rolling-reduction rolls 28E and 28I for a cast slab are arranged in the downstream side of a continuous caster, and based on the rolling-reduction of the cast slab when the rolling-reduction rolls 28E and 28I for the cast slab is rolling reduced with a prescribed rolling force, it is detected whether the solidification of the cast slab 12 is completed or not. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solidification completion detection method, apparatus, and continuous casting method and apparatus for continuous casting, and more particularly to continuous casting that can accurately know a solidification completion position (also referred to as a crater end) of a slab with a simple configuration. The present invention relates to a solidification completion detection method and apparatus, and a continuous casting method and apparatus using the same.

  In the continuous casting, as shown in FIG. 1, a molten metal, for example, molten steel 10 is supplied into a mold 24 from an immersion nozzle 22 provided at the bottom of the tundish 20, and the molten steel 10 is cooled with water. To a continuous cast slab (hereinafter simply referred to as a slab) 12 having a solidified shell 12a around it, and this slab 12 is transferred from the mold 24 to a number of slab support rolls (hereinafter referred to as slabs). Spray nozzles provided in the gaps between the rolls while being supported and guided by a slab support area (also referred to as a segment) formed by a slab support area (also referred to as a segment) 28 and pulled out by a pinch roll 36 disposed on the outlet side. (Not shown), cooling water is supplied to the slab 12 to perform secondary cooling, and solidification of the unsolidified portion (molten steel portion) 12b inside the slab is completed, and then cut to a predetermined length. Te, so that the continuous production of multiple slabs.

  In this continuous casting, the solidification completion position (also referred to as the solidification completion point) at which the unsolidified portion 12b in the slab 12 is completely solidified is in the segment that is the slab support area, that is, the end E of the continuous casting machine. It is necessary to be upstream. This is because if the solidification completion position is downstream of the machine end E, the static pressure of the molten steel acts on the unsolidified molten steel in the slab corresponding to the height from the molten metal surface position in the mold. The so-called bulging that mainly swells in the thickness direction in the thickness direction occurs, the shape of the slab is significantly deformed, and defects such as slab segregation, center porosity, or internal cracks occur at the center of the slab, resulting in slab quality. This is because it causes deterioration.

  Therefore, in the past, the solidification completion position at the steel type, casting speed, and cooling water amount is estimated from solidification analysis, past results, etc., and a margin of about 0.3 to 0.5 m is provided to ensure solidification is completed within the slab support area. The operation is carried out.

  As described above, the capacity of the continuous casting machine is determined by the secondary cooling, the roll pitch, and the length of the machine, but in order to maximize the equipment capacity, it is important to know the solidification completion position at the time of casting.

  Therefore, in Patent Document 1, the inter-roll displacement that occurs in each of a plurality of pairs of rolls that are rolled and sandwiched between the slabs is detected, and based on the respective detection results, in the slabs at the roll rolling positions of each pair. It has been proposed to determine whether or not any unsolidified portion remains, and to determine the complete solidification position of the slab based on the determination result.

  Moreover, in patent document 2, in the some roll arrange | positioned near the machine length end of the roller apron which supports and guides a slab, the load load of each roll is measured and the vanishing point of static iron pressure is based on these measured values. It has been proposed to determine a position and identify the position as a solidification completion position.

JP-A-2-229654 JP 2003-245762 A

  However, the methods described in Patent Documents 1 and 2 have large variations and cannot be detected with high accuracy.

  Ultrasonic and eddy current type crater end detection devices are also being studied. (1) The device becomes very expensive. (2) Since it is difficult to downsize the device, the main body of the continuous casting machine. It is necessary to make a major remodeling, and (3) the durability is low with respect to the environment during casting, and most of the existing examination techniques are not put into practical use.

  The present invention has been made to solve the above-mentioned conventional problems, and it is a first object to provide a solidification completion detection technique for continuous casting capable of accurately knowing the solidification completion position with a relatively simple configuration. It is an issue.

  The second object of the present invention is to provide a continuous casting technique to which the above technique is applied.

  The present invention provides a slab reduction roll on the downstream side of the continuous casting machine, and whether or not solidification of the slab is completed based on the slab reduction amount when the slab reduction roll is reduced with a predetermined reduction force. In this way, the first problem is solved.

  Further, the slab temperature in the vicinity of the reduction position by the slab reduction roll is detected, and the slab is excessively reduced by changing the reduction force of the slab reduction roll according to the detected slab temperature. An appropriate reduction force can be set.

  The present invention is also based on the slab reduction roll provided on the downstream side of the continuous casting machine and the slab reduction amount when the slab reduction roll is reduced with a predetermined reduction force. The present invention provides a solidification completion detection device for continuous casting, characterized by comprising means for detecting the presence or absence of completion of solidification.

  Further, a thermometer for detecting a slab temperature in the vicinity of a reduction position by the slab reduction roll is provided, and the reduction force of the slab reduction roll is changed according to the slab temperature detected by the thermometer. Thus, it is possible to set an appropriate reduction force that does not excessively reduce the slab.

  The present invention also provides at least two slab reduction rolls along the casting direction on the downstream side of the continuous casting machine, and the slab when the upstream slab reduction roll is reduced with a predetermined reduction force. At least one of the casting speed and the cooling speed is such that the reduction amount is not less than a predetermined value and the slab reduction amount when the downstream slab reduction roll is reduced with a predetermined reduction force is not more than the predetermined value. In this way, the second problem is solved.

  Further, the slab temperature in the vicinity of the reduction position by the slab reduction roll is detected, and when the detected slab temperature is not more than a predetermined value, the casting speed is reduced, and when the detected slab temperature is not less than the predetermined value. Can increase the cooling rate.

  The present invention is also provided when at least two slab reduction rolls provided along the casting direction on the downstream side of the continuous casting machine and the slab reduction roll on the upstream side are reduced with a predetermined reduction force. At least one of the casting speed and the cooling rate so that the slab reduction amount is not less than a predetermined value and the slab reduction amount when the downstream slab reduction roll is squeezed with a predetermined reduction force is not more than the predetermined value. And a means for controlling either one of them.

  Further, a thermometer for detecting the slab temperature in the vicinity of a reduction position by the slab reduction roll is provided, and when the slab temperature detected by the thermometer is equal to or lower than a predetermined value, the casting speed is reduced and the detected slab temperature is detected. When the half temperature is equal to or higher than a predetermined value, the cooling rate can be increased.

  According to the present invention, it is possible to accurately detect a solidification completion state (whether completely solidified or unsolidified portion is present) at a desired predetermined position (for example, the last end of the length) of the continuous casting machine with a simple configuration. Therefore, the margin can be reduced and the capacity can be increased by controlling so that the solidification completion position comes to the end of the continuous casting machine.

  In particular, at least two slab reduction rolls are provided on the downstream side of the continuous casting machine along the casting direction, and the slab reduction amount when the upstream slab reduction roll is reduced with a predetermined reduction force is predetermined. The casting speed and the cooling speed are controlled so that the amount of slab reduction when the downstream slab reduction roll is reduced by a predetermined reduction force is equal to or less than a predetermined value. In this case, the solidification completion position can be controlled so as to come between the two slab rolling rolls.

  The present situation is that the casting speed is 1.0 m / min, the production volume is 1.0 ton per month, and there is a problem that the solidification completion position goes out of the machine about twice a year. According to the report, even if the casting speed was increased to 1.1 m / min and the production volume was increased to 1.1 tons per month, there was no problem of missing the captain. Note that the increase in production volume takes into account only the increase in casting speed and does not take into account the decrease in trouble. Therefore, if the increase in operating time due to the decrease in trouble is taken into account, the production volume is expected to increase further.

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

  FIG. 2 (overall view), FIG. 3 (sectional view showing upstream segment 30M), and FIG. 4 (invention) of the first embodiment of the present invention are the same as the conventional casting machine shown in FIG. When the final roll 28E of the final segment 30E is provided with a reduction cylinder 40E to allow the slab 12 to be reduced, and the final roll 28E is reduced with a predetermined reduction force, as shown in FIG. Whether or not the slab has been solidified is detected based on the slab reduction amount.

  In the figure, 26 is a bending unit for bending the slab 12 directly below the mold 24, 32 is a slab cooling zone including a cooling spray 34 disposed between rolls 28, and 42 is a roll that can be displaced vertically. 4 is a thickness measuring device for measuring the thickness of the slab 12 after complete solidification.

  Since there is a relationship as illustrated in FIG. 5 between the unsolidified thickness in the slab and the slab reduction amount, when the reduction amount of the final roll 28E is a predetermined value, for example, 0.02 mm or more, Can be determined. FIG. 5 shows data for a rolling force of 60 tons and a slab thickness of 240 mm.

  When unsolidification is detected at the position of the final roll 28E, the cooling rate is increased by increasing the amount of cooling water from the cooling spray 34, or the slab drawing speed by the pinch roll 36 (see FIG. 1) is decreased. Thus, the casting speed can be reduced.

  Since the unsolidified thickness changes according to the slab temperature, a thermometer 46 is provided in the vicinity of the final roll 28E, and the reduction force applied to the reduction cylinder 40E is changed according to the temperature detected by the thermometer 46. Can do. Specifically, since there is a relationship as illustrated in FIG. 6 between the slab surface (corner) temperature in the medium charcoal material and the occurrence rate of the key crack at the time of rolling, depending on the temperature detected by the thermometer 46. The rolling force can be reduced so that an excessive rolling force is not applied to the slab 12.

  In addition, according to the first embodiment, it is possible to detect the presence or absence of complete solidification in the final roll 28E, but since it is measurement at one point, it is not easy to accurately control the complete solidification position. . Accordingly, a second embodiment of the present invention in which the complete solidification position can be maintained in the final segment 30E will be described next.

  In the present embodiment, in the continuous casting machine similar to the first embodiment, as shown in FIG. 7, a roll-down cylinder 40I is also provided on the roll 28I on the entry side of the final segment 30E to allow the slab to be reduced. The solidification completion position is controlled between 28I and the exit-side final roll 28E.

  Specifically, as shown in FIG. 8, the slab surface (corner) temperature is measured by the thermometer 46 in step S1, and when the slab surface temperature is a predetermined value, for example, less than 700 ° C., 700 ° C. or more. The cooling speed is shortened by increasing the drawing speed and increasing the casting speed.

  If the slab surface temperature is 700 ° C. or higher in step S2, in order to know the solidified state on the entry side of the final segment 30E, in step S3, a predetermined reduction force, for example 60 tons, is applied by the entry side reduction cylinder 40I. Then, the entry side roll 28I is reduced. When the reduction amount is less than a predetermined value, for example, 0.02 mm, the solidification has already been completely solidified on the final segment 30E entry side, and there is room for increasing the production rate by increasing the speed. And the process returns to step S3.

  When it is determined in step S4 that the reduction amount is 0.02 mm or more and there is an unsolidified portion at the position of the entry side roll 28I, the process proceeds to step S5, the entry side reduction cylinder 40I is opened, and the exit side reduction cylinder 40E. The final roll 28E is reduced. If it is determined in step S6 that the reduction amount is 0.02 mm or less, since the solidification is completed in the final segment 26E, the casting is continued as it is.

  On the other hand, if the reduction amount is less than 0.02 mm in step S6, it is determined from the output of the thermometer 46 whether the slab surface temperature is 700 ° C. or higher. When it is determined in step S7 that the slab surface temperature is 700 ° C. or lower, the speed is reduced and the process returns to step S5.

  On the other hand, when it is determined in step S8 that the slab surface temperature is 700 ° C. or higher, the amount of cooling water is increased, and the process returns to step S5 as strong cooling.

  According to the second embodiment, since the entrance side roll 28I and the exit side roll 28E of the final segment 30E are two slab pressing rolls, the complete solidification position can be reliably maintained in the final segment 30E, and production can be performed. Efficiency can be maximized. In addition, rolls other than the entrance side roll 28I and the exit side roll 28E can also be used as a slab reduction roll.

  In each of the above-described embodiments, the roll in the final segment 30E is provided with a reduction cylinder to form a slab reduction roll, so the configuration is simple. It is also possible to provide a slab pressing roll independent of the slab support roll 28 of the segment.

  Moreover, in the said embodiment, since all provided the thermometer, highly accurate control is possible. The thermometer can be omitted.

Sectional drawing which shows the whole structure of the continuous casting machine which is the object of this invention Sectional drawing which shows the structure of 1st Embodiment of this invention. Sectional drawing which shows the structure of the upstream segment used by 1st Embodiment Sectional view showing the configuration of the final segment The diagram which shows the example of the relationship between the unsolidified thickness which shows the principle of this invention, and slab reduction amount Diagram showing an example of the relationship between the slab surface (corner) temperature and the incidence of key cracks Sectional drawing which shows the structure of the last segment in 2nd Embodiment of this invention. Flow chart showing the processing procedure of the second embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Molten steel 12 ... Cast slab 24 ... Mold 28 ... Slab support roll 30 ... Segment 30E ... Final segment 32 ... Slab cooling zone 34 ... Cooling spray 40E, 40I ... Reduction cylinder 46 ... Thermometer

Claims (8)

A slab reduction roll is provided on the downstream side of the continuous casting machine,
A solidification completion detection method for continuous casting, characterized by detecting whether or not solidification of a slab is completed based on a slab reduction amount when the slab reduction roll is reduced with a predetermined reduction force. Detecting the slab temperature near the reduction position by the slab reduction roll,
The solidification completion detection method for continuous casting according to claim 1, wherein the rolling force of the roll for rolling down the slab is changed according to the detected slab temperature. A slab rolling roll provided on the downstream side of the continuous casting machine;
Means for detecting the presence or absence of solidification completion of the slab based on the slab reduction amount when the slab reduction roll is reduced with a predetermined reduction force;
A solidification completion detection device for continuous casting, comprising:   A thermometer for detecting a slab temperature in the vicinity of a reduction position by the slab reduction roll is provided, and the reduction force of the slab reduction roll is changed according to the slab temperature detected by the thermometer. The solidification completion detection device for continuous casting according to claim 3, wherein: On the downstream side of the continuous casting machine, at least two slab reduction rolls are provided along the casting direction,
The amount of slab reduction when the slab reduction roll on the upstream side is reduced with a predetermined reduction force is a predetermined value or more,
The slab reduction amount when the slab reduction roll on the downstream side is reduced with a predetermined reduction force so that the slab reduction amount is a predetermined value or less,
A continuous casting method comprising controlling at least one of a casting speed and a cooling speed.   The slab temperature in the vicinity of the reduction position by the slab reduction roll is detected. When the detected slab temperature is lower than a predetermined value, the casting speed is lowered, and when the detected slab temperature is higher than a predetermined value, cooling is performed. 6. The continuous casting method according to claim 5, wherein the speed is increased. On the downstream side of the continuous casting machine, at least two slab rolling rolls provided along the casting direction;
The slab reduction amount when the slab reduction roll when the upstream slab reduction roll is squeezed with a predetermined reduction force is greater than or equal to a predetermined value and the downstream slab reduction roll is squeezed with a predetermined reduction force Means for controlling at least one of a casting rate and a cooling rate so that the amount is equal to or less than a predetermined value;
A continuous casting apparatus comprising:   A thermometer for detecting a slab temperature in the vicinity of a reduction position by the slab reduction roll is provided, and when the slab temperature detected by the thermometer is equal to or lower than a predetermined value, the casting speed is lowered, and the detected slab temperature is detected. The continuous casting apparatus according to claim 7, wherein the cooling rate is increased when the value is equal to or greater than a predetermined value.

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