JP2012170995A - Measuring method of cast slab surface temperature in continuous casting machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely measure the surface temperature of a cast slab while accurately understanding an end part of the cast slab being cast, without affected by a secondary cooling water remaining on the surface of cast slab, the steam generated from the secondary cooling water, and the white plume resulting from condensation of the steam.SOLUTION: The measuring method of surface temperature of a cast slab measures the surface temperature of the cast slab 10 which is being continuously cast, using an infrared sensing type surface temperature measuring instrument 13. The infrared sensing type surface temperature measuring instrument is used in which the measurement direction of radiation energy from the surface of cast slab is tilted from the vertical line on the surface of cast slab by a range of 1-60° along cast slab width direction. The distance between a condenser lens of the infrared sensing type surface temperature measuring instrument and the surface of cast slab is 100-800 mm. The gas of 10 NL/mil or more is jetted toward the cast slab from the infrared sensing type surface temperature measuring instrument. The gas excludes the secondary cooling water and vapor from between the condenser lens and the surface of cast slab as well as from a temperature-measurement point of the cast slab.

Description

  The present invention relates to a method for measuring the surface temperature of a slab cast by a continuous casting machine using an infrared-sensitive surface temperature measuring device.

  In continuous casting of steel, the molten steel in the ladle is once poured into the tundish, and a predetermined amount of molten steel stays in the tundish, and the immersion steel is placed in the tundish at the bottom of the tundish. Through the mold. The molten steel injected into the mold is cooled to form a solidified shell on the contact surface with the mold, and this slab with the solidified shell as the outer shell and the unsolidified molten steel inside is a secondary provided below the mold. In the cooling zone, while being cooled by cooling water (also referred to as “secondary cooling water”) sprayed on the surface of the slab, it is continuously drawn below the mold, and eventually solidification to the center is completed. A slab which is a raw material for rolling is manufactured by cutting a slab that has been solidified to the center to a predetermined length.

  Maintaining the surface temperature of the slab during casting within the target range in the secondary cooling zone is a basic means of ensuring the quality of the slab and measures the energy of the emitted light emitted from the surface of the slab. It has been conventionally performed to measure the surface temperature of a slab during casting using a surface temperature measuring device such as a radiation thermometer that measures the slab surface temperature (see, for example, Patent Document 1). However, in the secondary cooling zone, slab support rolls for suppressing swell of the slabs due to the molten steel static pressure are arranged at intervals of 150 to 400 mm in the casting direction, and the interval between adjacent rolls is narrow. The secondary cooling water remained on the surface of the slab or steam was generated, so that the measurement accuracy of the surface temperature was not high. It was also difficult to measure stably over a long period of time.

  However, in recent years, with the demand for increased production and highly functional materials, there is a demand for a continuous casting machine having high functionality that enables dynamic control and active control. Therefore, it is important to measure the temperature of the slab surface accurately and stably in a continuous casting machine. Further, if the casting speed of the slab is increased for the purpose of increasing production, cracks are likely to occur at the corner of the slab, and temperature management at the corner of the slab becomes important. For this reason, it is important to accurately grasp the surface temperature two-dimensionally in the slab width direction in the continuous casting machine.

  Patent Document 2 discloses a method for solving an error caused by absorption of radiant energy by a treatment liquid such as cooling water present on the surface of a steel material when measuring the surface temperature of the steel material during cooling with a radiation thermometer. And patent document 3 is proposed. In the measurement methods proposed in Patent Document 2 and Patent Document 3, a water column as an optical waveguide is formed between a temperature-measured steel material and a radiation thermometer, and the light emitted from the surface of the temperature-measured steel material through the water column. Is detected by a radiation thermometer, and the surface temperature of the steel material to be measured is measured.

  In addition, as a device for measuring the slab surface temperature during continuous casting, Patent Document 4 discloses a light guide that has an opening at the tip thereof that faces the slab surface and takes in the radiated light from the slab surface. And a condensing unit comprising a condensing lens disposed on the basis thereof, and an electric light connected to the condensing unit via an optical fiber, and the radiated light collected by the condensing lens is related to the slab surface temperature. A surface temperature measuring device having a photoelectric conversion unit for converting into a signal and a purging unit for blowing gas into the light guide and ejecting the gas from the opening is proposed. A temperature sensor adapted to detect the gas, a purge gas system connected to the temperature sensor and supplying a purge gas for removing and rejecting slab surface residues monitored by the temperature sensor; With Surface temperature measuring device has been proposed.

Japanese Utility Model Publication No. 58-49236 Japanese Patent Application Laid-Open No. 59-1000022 JP 2008-164626 A JP-A-4-162949 JP 2007-296583 A

  When the surface temperature of a slab is measured in a non-contact manner using an infrared-sensitive surface temperature measuring instrument in a continuous casting machine, the following matters become a problem. That is, the secondary cooling water remaining on the surface of the slab refracts the radiated light, which hinders accurate temperature measurement. Moreover, since the water vapor | steam produced | generated from secondary cooling water by heat exchange with a slab absorbs infrared rays, this also becomes a hindrance to temperature measurement. Furthermore, white smoky smoke is generated during the cooling of the slab in the secondary cooling zone of the continuous casting machine. This is not water vapor, but water vapor is caused by dust and dust in the air as condensation nuclei. Although it is condensed and is referred to as “white water smoke” here, it also scatters light, which hinders temperature measurement by an infrared sensitive surface temperature measuring device.

  Also, when measuring the temperature distribution in the slab width direction while reciprocating the infrared sensitive surface temperature measuring instrument in the slab width direction, the slab end (the corner between the long side surface and the short side surface) The surface temperature is low, and the surface temperature measuring device detects the radiant energy from the short side of the slab even if it leaves the slab end, and it is difficult to distinguish the area where the slab does not exist and the slab end, When the surface temperature of the slab end cannot be accurately grasped, that is, when the distribution of the slab surface temperature cannot be accurately grasped.

  As a means for measuring the slab surface temperature in a continuous casting machine having such a problem, if Patent Documents 2 to 5 are verified, Patent Documents 2 and 3 that measure through a water column are added to secondary cooling. Furthermore, since the surface of the slab is cooled by water, and this causes an increase in unevenness of the slab surface temperature, it is not appropriate for measuring the surface temperature of the slab during casting. It is also difficult to measure two-dimensionally in the slab width direction.

  In Patent Documents 4 and 5, residual gas and steam on the surface of the slab are excluded and discharged by injecting a purge gas, but it is possible to measure the air flow rate and high accuracy for reliable purging. The distance between the slab and the surface temperature measuring instrument is not disclosed. If the flow rate of the purge air is insufficient, it is impossible to exclude the secondary cooling water on the surface of the slab, and if the surface temperature measuring instrument is too far from the slab, it will be purged. However, it is easily affected by steam, and the white water smoke condensed with water vapor may scatter the radiated light between the surface temperature measuring instrument and the slab, making measurement impossible. Furthermore, Patent Documents 4 and 5 do not describe a method for determining a slab end.

  The present invention has been made in view of the above circumstances, and its purpose is to provide secondary cooling water remaining on the surface of the slab while accurately grasping the end of the slab cast by a continuous casting machine. Another object of the present invention is to provide a method for accurately measuring the surface temperature of a slab with an infrared-sensitive surface temperature measuring instrument without being affected by water vapor generated from secondary cooling water and white water smoke condensed with water vapor.

The gist of the present invention for solving the above problems is as follows.
(1) A method for measuring a slab surface temperature in a continuous casting machine, wherein the surface temperature of a slab during continuous casting is measured by an infrared-sensitive surface temperature measuring instrument, the slab of an infrared-sensitive surface temperature measuring instrument Infrared sensitive surface temperature measurement using an infrared sensitive surface temperature measuring instrument whose radiant energy measurement direction from the surface is inclined in the range of 1 to 60 degrees in the slab width direction with respect to the vertical line of the slab surface The distance between the condenser lens and the slab surface is within a range of 100 to 800 mm, and a gas of 10 NL / min or more is jetted from the infrared-sensitive surface temperature measuring instrument toward the slab. Measuring the surface temperature of the slab with the infrared-sensitive surface temperature measuring device while discharging secondary cooling water and steam between the condenser lens and the surface of the slab and from the temperature-measured portion of the slab. In the continuous casting machine Of measuring the slab surface temperature of steel.
(2) The infrared-sensitive surface temperature measuring instrument is an infrared-sensitive surface temperature measuring instrument having two radiant energy measuring directions each inclined to the opposite side of the slab width direction. The measuring method of the slab surface temperature in the continuous casting machine as described in (1).
(3) The surface temperature of the slab is measured by reciprocating the infrared-sensitive surface temperature measuring instrument in the width direction of the slab, and the obtained temperature measurement value in the slab width direction is measured as a distance in the slab width direction or measured. Differentiating with time, determining the position of the maximum value of the differential value as the end of the slab and measuring the surface temperature distribution of the slab, as described in (1) or (2) above A method for measuring the slab surface temperature in a continuous casting machine.

  According to the present invention, an infrared ray whose radiant energy measurement direction from the slab surface of the infrared-sensitive surface temperature measuring device is inclined in the range of 1 to 60 degrees in the slab width direction with respect to the vertical line of the slab surface. Since a sensor-type surface temperature measuring device is used, when the temperature is measured from outside the range of the slab width toward the slab, the radiant energy from the short side of the slab is detected. The end of the slab with a low surface temperature can be reliably grasped. Further, the distance between the condensing lens of the infrared-sensitive surface temperature measuring instrument and the slab surface is set within a range of 100 to 800 mm, and a gas of 10 NL / min or more is jetted from the surface temperature measuring instrument toward the slab. However, since the surface temperature of the slab is measured, the secondary cooling water remaining on the surface of the slab, water vapor generated from the secondary cooling water, and white water smoke condensed with water vapor are not affected by accuracy and for a long time. Thus, it is possible to stably measure the surface temperature of the slab during continuous casting. Furthermore, since it is possible to measure the slab surface temperature accurately and stably over a long period of time, it is possible to prevent the occurrence of slab surface defects and to perform dynamic control using a surface thermometer. The secondary effect is also expressed.

It is the schematic of an example of the vertical bending type slab continuous casting installation with which this invention is applied. FIG. 2 is a schematic view of the infrared sensitive surface temperature measuring device shown in FIG. 1. It is a figure which shows the example of the measurement result of the slab surface temperature measured when the radiant energy measurement direction of a condensing lens is made to incline in the slab width direction with respect to the vertical line of a slab surface. It is the schematic of the other form of the infrared sensitive surface temperature measuring device used by this invention. It is a figure which shows the relationship between the absorption ratio of the infrared rays which passed the water vapor layer, and the wavelength of infrared rays. It is a figure which contrasts and shows the measured value of surface temperature, and the result of differentiating this measured temperature value by measuring time. In Example 1 of this invention, it is a figure which shows the temperature measurement value obtained when the infrared sensitive surface temperature measuring device was moved to the slab width direction. It is a figure which shows the result of differentiating the temperature measurement value shown in FIG. 7 by the slab width direction distance. In Example 2 of this invention, it is a figure which shows the temperature measurement value obtained when the infrared sensitive surface temperature measuring device was moved to the slab width direction. It is a figure which compares and shows the measurement result of the surface temperature distribution of slab by the example 2 of this invention, and the comparative example 1. FIG. It is a figure which compares and shows the measurement result when measuring temperature to the range where a slab does not exist in this invention example 2 and the comparative example 2. FIG.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic view of an example of a vertical bending type slab continuous casting equipment to which the present invention is applied, and FIG. 2 is a schematic view of an infrared sensitive surface temperature measuring device 13 shown in FIG.

  As shown in FIG. 1, a slab continuous casting machine 1 is provided with a mold 5 for injecting and solidifying molten steel 9 to form an outer shell shape of a slab 10, and a predetermined position above the mold 5. Is provided with a tundish 2 for relaying and supplying molten steel 9 supplied from a ladle (not shown) to the mold 5. On the other hand, a plurality of pairs of slab support rolls 6 including a support roll, a guide roll, and a pinch roll are arranged below the mold 5. A secondary cooling zone in which a spray nozzle (not shown) such as a water spray nozzle or an air mist spray nozzle is arranged is formed in the gap between the slab support rolls 6 adjacent in the casting direction. The slab 10 is cooled while being drawn out by cooling water sprayed from the nozzle (also referred to as “secondary cooling water”).

  A sliding nozzle 3 for adjusting the flow rate of the molten steel 9 is installed at the bottom of the tundish 2, and an immersion nozzle 4 is installed on the lower surface of the sliding nozzle 3. A plurality of transport rolls 7 for transporting the cast slab 10 are installed on the downstream side of the slab support roll 6. Above the transport roll 7, the cast slab 10 to be cast is provided. A gas cutting machine 8 for cutting a slab 10a having a predetermined length is disposed.

  An infrared-sensitive surface temperature measuring device 13 for measuring the surface temperature of the slab 10 is installed on the upper surface side of the slab 10 and in the gap between adjacent slab support rolls 6 in the secondary cooling zone. Yes. As shown in FIG. 2, the infrared-sensitive surface temperature measuring device 13 includes a converter 14 that is movably disposed with respect to a reciprocating slider 21 that is held by a support base 22 fixed to the segment frame 20, and a conversion device. An optical fiber 15 connected to the optical device 14, a condensing lens 16 connected to the other end of the optical fiber 15, a protective cover 17 whose upper end is in close contact with the converter 14, covers the optical fiber 15 and the condensing lens 16, and whose lower end is open It is equipped with. A gas introduction pipe 18 for introducing a purge gas is installed on the protective cover 17.

  That is, the radiated light emitted from the surface of the slab 10 is collected by the condenser lens 16, and the collected radiated light is sent to the converter 14 via the optical fiber 15, and the radiated light sent to the converter 14 is The intensity is detected by a synchrotron radiation detection element made of, for example, a Si semiconductor, which is arranged in the converter 14, and is converted into a slab surface temperature based on the detected intensity, and thus the surface temperature of the slab 10 is measured. It is like that. The protective cover 17 protects the optical fiber 15 and the condensing lens 16 and at the same time plays a role of ejecting the purge gas introduced from the gas introduction pipe 18 toward the slab surface.

  The infrared sensitive surface temperature measuring device 13 can measure the surface temperature of the entire width direction of the slab 10 by moving the reciprocating slider 21 left and right. The infrared sensitive surface temperature measuring device 13 is configured to be attached at an arbitrary position in the casting direction of the secondary cooling zone. In FIG. 2, only the upper surface side of the slab 10 is shown as a segment for supporting the slab 10, but the lower surface side of the slab 10 has a similar structure. In FIG. 2, reference numeral 19 denotes a tie rod for connecting the upper segment frame 20 and the lower segment frame (not shown) at a predetermined interval.

  In the present invention, the distance between the condenser lens 16 and the surface of the slab 10 is set within a range of 100 to 800 mm. This is in order to avoid white water smoke (those in which water vapor is condensed using dust and dust in the air as condensation nuclei) generated by secondary cooling. In continuous casting of steel, molten steel of 1500 ° C. or higher is handled, and the surface temperature of the slab 10 in the continuous casting machine is 600 to 1100 ° C. On the other hand, white water smoke is condensed when water vapor generated by secondary cooling becomes 100 ° C or lower under atmospheric pressure and dust or dust is condensed as condensation nuclei. No white water smoke is generated. Although it depends on the size of the slab 10, in a slab continuous casting machine that casts a general slab having a slab width of 900 mm or more, the atmospheric temperature is almost 100 ° C. or more if it is within 800 mm from the slab surface. It was. Based on this, the upper limit of the distance between the condenser lens 16 and the slab surface was set to 800 mm. On the other hand, the reason why the distance between the condensing lens 16 and the slab surface is 100 mm or more is to prevent the condensing lens 16 and the optical fiber 15 from being melted and deteriorated by heat from the slab 10.

  In the present invention, the flow rate of the purge gas ejected from the protective cover 17 is set to 10 NL / min or more. This not only excludes and rejects steam between the condenser lens 16 and the slab surface, but also ensures cooling water remaining on the slab surface, which is the location to be measured, and the scale peeled off from the slab surface. It is for blowing away. Naturally, if the flow rate of the purge gas is large, the effect of exclusion / rejection is high, and therefore the optimal flow rate of the purge gas is about 50 NL / min.

  Furthermore, in the present invention, the infrared ray detection in which the axial center direction of the condenser lens 16 is inclined in the range of 1 to 60 degrees in the slab width direction with respect to the vertical line Z of the slab surface (long side surface). A formula surface temperature measuring device 13 is used. That is, the measurement direction R of the radiant energy from the slab surface of the condenser lens 16 is inclined in the range of 1 to 60 degrees with respect to the vertical line Z of the slab surface when viewed from the casting direction of the slab 10. The infrared sensitive surface temperature measuring instrument 13 is used (which means that the angle formed between the vertical line Z and the measuring direction R when viewed from the casting direction is 1 to 60 degrees). In FIG. 2, the condensing lens 16 is inclined toward the right side of the drawing, but the inclination direction is not limited to this direction, and there is no problem even if it is inclined toward the left side. However, the present invention cannot be applied no matter how much tilted in the casting direction, unless tilted in the range of 1 to 60 degrees in the slab width direction.

  Thus, the reason why the radiant energy measurement direction R of the condenser lens 16 is inclined in the range of 1 to 60 degrees in the slab width direction with respect to the vertical line Z is as follows.

  That is, when the surface temperature of the slab 10 is measured by reciprocating the infrared-sensitive surface temperature measuring instrument 13 in the slab width direction, the infrared-sensitive surface temperature measuring instrument 13 is provided at the end of the slab (the slab 10 The temperature is measured by moving to the area off the slab end without stopping at the corner of the long side and the short side. Since the width of the slab 10 is changed even during continuous casting, such a surface temperature measuring method is adopted. On the other hand, the end portion of the slab 10 is cooled from two directions, that is, the slab long side surface side and the slab short side surface side, and both the long side surface side and the short side surface side are relatively relative to the surroundings. The surface temperature is lowered.

  By inclining the measurement direction R of the radiant energy, that is, the radiated light of the infrared sensitive surface temperature measuring device 13 with respect to the vertical line Z in the range of 1 to 60 degrees in the slab width direction, this infrared sensitive surface temperature measuring device When the temperature is measured by moving 13 in the width direction of the slab, the direction in which the measurement direction R faces is the same as the direction in which the infrared sensitive surface temperature measuring device 13 moves (the direction from the left side to the right side of the paper surface of FIG. 2). In this case, when the slab end portion passes from the side where the slab 10 does not exist toward the slab side, the short side surface of the slab 10 enters the measurement visual field. The radiant energy of the short side surface of the slab whose surface temperature is higher than that of the one end portion is detected, thereby increasing the measurement temperature. Thereafter, the measurement temperature is lowered by measuring the end portion of the slab, which is relatively cooler than the surroundings, and the measurement temperature rises again when the end portion of the slab is passed. That is, it becomes possible to grasp the slab end as the position of the minimum value of the measured temperature from the measured surface temperature distribution.

  However, when passing through the opposite slab end, the slab short side surface does not enter the measurement field of view, so the radiant energy of the slab short side surface is not detected, and the measurement temperature at the slab end is monotonous. The slab end cannot be clearly identified. Further, the infrared sensitive surface temperature measuring device 13 is directed in the reverse direction (the direction in which the measuring direction R is directed and the moving direction of the infrared sensitive surface temperature measuring device 13 is opposite, the direction from the right side to the left side in FIG. 2). 2, the radiant energy of the short side of the slab on the right side of the paper of FIG. 2 cannot be detected, and the radiant energy of the short side of the slab of the left side of FIG. 2 is detected. The

  However, since the width of the slab 10 can be known by inputting it to the converter 14 from the control computer of the continuous casting machine, if the position of one slab end can be accurately grasped, the other slab end Can also be grasped based on the moving speed of the infrared sensitive surface temperature measuring device 13. That is, by measuring the slab surface temperature in this manner, the width of the slab 10 can be accurately grasped, and the surface temperature distribution of the slab 10 can be accurately obtained.

  If the measurement direction R of the radiated light is not inclined and is parallel to the vertical line Z, the short side surface of the slab 10 does not enter the measurement field of view of the infrared sensitive surface temperature measuring device 13 and the infrared sensitive surface temperature measurement is performed. When the vessel 13 passes the slab end toward the slab side, the temperature distribution increases monotonously, while when the infrared-sensitive surface temperature measuring instrument 13 passes the slab end from the slab side, The temperature distribution decreases monotonously, and the position of the slab end cannot be accurately grasped. As a result, the surface temperature distribution of the slab 10 cannot be obtained accurately.

  If the measurement direction R of the emitted light from the slab surface of the condenser lens 16 is less than 1 degree in the slab width direction with respect to the vertical line Z, the slab short side surface does not sufficiently enter the measurement field, When it exceeds 60 degrees in the slab width direction with respect to the vertical line Z, the infrared sensitive surface temperature measuring device 13 is a device for measuring the emitted light on the long side of the slab, and the infrared sensitive surface temperature measuring device 13 The intensity of the radiant energy from the long side surface of the slab that is detected by this decreases, and the error of the temperature measurement value increases.

  FIG. 3 shows the measurement of the slab surface temperature measured when the measurement direction R of the emitted light of the condenser lens 16 is inclined in the slab width direction with respect to the vertical line Z of the slab surface (long side surface). An example of the result is shown. In FIG. 3, the measured value of the surface temperature indicated by the solid line is data when the condensing lens 16 is moved in the slab width direction with the direction of the measurement direction R facing the right side of the paper surface of FIG. The measured values of the surface temperature shown are data when the condensing lens 16A is moved in the slab width direction with the direction in the measurement direction R facing the left side of the paper surface of FIG. As shown in FIG. 3, the slab end (= end A) is clearly detected as the position of the minimum surface temperature, and the other slab end (= end B) is infrared-sensitive surface temperature measurement. It can be obtained from the moving speed of the vessel 13 and the slab width.

  Further, as apparent from FIG. 3, the slab 10 is obtained by using an infrared sensitive surface temperature measuring device including two condensing lenses 16 in which the direction of the measurement direction R of the emitted light is opposite. It is possible to grasp both the left and right end positions from the measured surface temperature. Similarly, it is also possible to install two infrared-sensitive surface temperature measuring devices 13 each having a condenser lens 16 in which the measurement direction R of the emitted light is opposite to each other in the slab width direction. It is possible to grasp both the left and right end positions from the measured surface temperature.

  FIG. 4 shows a schematic diagram of an infrared-sensitive surface temperature measuring device 13A including two condenser lenses 16 and 16A whose measurement direction R is opposite. In FIG. 4, the infrared-sensitive surface temperature measuring device 13 </ b> A is connected to a converter 14 movably disposed with respect to the reciprocating slider 21, an optical fiber 15 connected to the converter 14, and the other end of the optical fiber 15. The condenser lens 16 and a protective cover 17 whose upper end is in close contact with the converter 14, covers the optical fiber 15 and the condenser lens 16, and whose lower end is opened are provided as one radiant energy measurement path, and the converter 14 An optical fiber 15A to be connected, a condensing lens 16A to be connected to the other end of the optical fiber 15A, a protective cover 17A whose upper end is in close contact with the converter 14, covers the optical fiber 15A and the condensing lens 16A, and whose lower end is open, etc. As a radiant energy measurement path. A gas introduction pipe 18 for introducing a purge gas is installed on the upper part of the protective cover 17, and a gas introduction pipe 18A for introducing a purge gas is installed on the upper part of the protective cover 17A. Yes.

  That is, the radiant energy measured by the two condenser lenses 16 and 16A is input to one converter 14, and the surface temperature distribution in the slab width direction is obtained from the measurement data of the condenser lenses 16 and 16A. It is configured. In this case, two surface temperatures at the same location are measured by the respective condensing lenses 16 and 16A, but the measured value of the surface temperature is generally lower than the true surface temperature due to the influence of disturbance or the like. Therefore, the higher measured value may be the surface temperature of the part. The optical fiber 15A, the condensing lens 16A, the protective cover 17A, and the gas introduction pipe 18A have the same functions as the optical fiber 15, the condensing lens 16, the protective cover 17, and the gas introduction pipe 18 described above, and a description thereof is omitted. .

  In the present invention, as the infrared sensitive surface temperature measuring devices 13 and 13A, it is preferable to use infrared sensitive surface temperature measuring devices having a measurement wavelength of 5.0 μm or less and an infrared absorption rate of 20% or less. This is because the influence of water vapor becomes stronger when the measurement wavelength exceeds 5.0 μm, the measurement accuracy is lowered, and the influence of water vapor can be suppressed by using a wavelength region where the infrared absorption rate is 20% or less. by.

  In addition, in order to further improve the measurement accuracy, an infrared sensitive surface temperature measuring device having a measurement wavelength of 1.33 μm or less, 1.5 to 1.8 μm, 2.0 to 2.4 μm, 3.4 to 4.8 μm Is preferably used. FIG. 5 shows the relationship between the absorption ratio of infrared rays that have passed through the water vapor layer and the wavelength of infrared rays. FIG. 5 shows reference 1 (heat transfer engineering (bottom), original author: JP Hallman, author: Ken Hirata, publisher: Brain Book Publishing Co., Ltd., publisher: Maruzen Co., Ltd., September 1988). 3rd day, 1st edition, 5th printing, P. 308), measurement wavelength is 1.33 μm or less, 1.5-1.8 μm, 2.0-2.4 μm, 3.4- In the range of 4.8 μm, the absorption of infrared rays is low.

  In FIG. 5, the wavelength range from 0.8 μm to 4 μm is a measured value at a steam temperature of 127 ° C. and a water vapor layer thickness of 109 cm, and (a) the steam temperature is 127 ° C. when the wavelength is from 4 μm to 34 μm. , Measured value at a steam layer thickness of 109 cm, (b) measured at a steam temperature of 127 ° C., measured at a steam layer thickness of 104 cm, (c) measured at a steam temperature of 127 ° C. and a steam layer thickness of 32.4 cm (D) measured value at a steam temperature of 81 ° C. and a water vapor layer thickness of 4 cm, (e) measured value at room temperature and a water vapor layer thickness of 7 cm.

  By making the detection element of the radiated light from the slab 10 one of Si semiconductor, PbS semiconductor, and InGaAs semiconductor, the measurement wavelength of the infrared sensitive surface temperature measuring devices 13 and 13A can be within the above range. it can. In particular, Si semiconductors are preferable as a sensing element because they are well permeable to water vapor.

  Further, the converter 14 is a temperature measurement value in the slab width direction (slab slab) measured by reciprocating the infrared sensitive surface temperature measuring devices 13 and 13A in the width direction of the slab 10 over the slab width. The temperature of the slabs on both sides of the slab (including temperature measurement values) is differentiated by the slab width direction distance or measurement time, and the position of the maximum value of the differential value is determined as the end of the slab 10 have.

  For example, when the temperature is measured by reciprocating the infrared-sensitive surface temperature measuring instrument 13A in the width direction of the slab 10 over the slab width, a temperature measurement value as shown in FIG. 6A is obtained. Then, this temperature measurement value is differentiated by the slab width direction distance or measurement time, and the distribution of the differential value as shown in FIG. 6 (B) is obtained, and the positions of the two maximum values of the differential value, that is, This is a function of determining a position connecting 6 (A) and FIG. 6 (B) with a broken line as an end portion of the slab 10. In this case, the threshold value of the differential value is set to 10,000 or more in absolute value, and the position inside the maximum value exceeding the threshold value is determined as the end portion of the slab 10, so that the slab end portion can be determined more easily. . In the case of the infrared sensitive surface temperature measuring instrument 13 having only one condenser lens 16, only the maximum value on one side is obtained.

  The converter 14 refers to the information of the slab 10 measuring the temperature (the slab width in the case of FIG. 6 is 1400 mm), which is input from a control computer (not shown) of the continuous casting machine. The measurement value in the range indicated as “slab width” in FIG. 6A is output to a monitor (not shown) or a storage device separately provided as a temperature distribution in the width direction of the slab 10. That is, also from FIG. 6 (A), the position of the temperature minimum value where the temperature once decreases and then increases can be determined as the slab end, but by using the method of FIG. 6 (B) together, It becomes accurate and easy to determine the end of the single-layer slab. Thereby, the slab end can be grasped more accurately, and the surface temperature distribution in the slab width direction can be accurately obtained.

  Note that the converter 14 includes raw data (corresponding to FIG. 6A) of temperature measurement values measured by the infrared-sensitive surface temperature measuring devices 13 and 13A and differential values of the raw data (FIG. 6B). Is also configured to output to a monitor or storage device. FIG. 6B shows the result of differentiating the temperature measurement value shown in FIG. 6A with the measurement time (0.01 seconds), and the differential value is displayed as an absolute value. Further, the horizontal axis of FIG. 6 represents the count number corresponding to the moving distance when the infrared sensitive surface temperature measuring device 13A is moved from the left side to the right side of the reciprocating slider 21 over the range of the slab 10 or more. It is.

  In the slab continuous casting machine 1 having this configuration, the molten steel 9 is poured from the ladle into the tundish 2 so that a predetermined amount of the molten steel 9 is retained in the tundish 2, and then the molten steel 9 retained in the tundish 2 is immersed. It is injected into the mold 5 through the nozzle 4. A mold powder (not shown) that functions as a heat insulating agent, a lubricant, an antioxidant, or the like is added onto the molten steel in the mold.

  The molten steel 9 injected into the mold 5 is cooled by the mold 5 to form a solidified shell 11 and supports a plurality of pairs of slabs provided below the mold 5 as a slab 10 having an unsolidified phase 12 therein. While being supported by the roll 6, it is continuously pulled out below the mold 5 by the driving force of the pinch roll. The slab 10 is cooled in the secondary cooling zone while passing through these slab support rolls 6 to increase the thickness of the solidified shell 11 and eventually complete the solidification to the inside. The slab 10 that has been solidified to the inside is cut by the gas cutter 8 to become a slab 10a.

  In such a continuous casting operation, the surface temperature of the slab 10 is measured using the infrared sensitive surface temperature measuring device 13 or the infrared sensitive surface temperature measuring device 13A. At that time, the temperature may be measured while reciprocating the infrared sensitive surface temperature measuring devices 13 and 13A in the width direction of the slab, or the temperature may be measured while being fixed at a fixed position. This may be determined according to the purpose of measuring the surface temperature of the slab 10.

  When the surface temperature of the slab 10 is measured while reciprocating the infrared-sensitive surface temperature measuring devices 13 and 13A in the slab width direction over the slab width, the infrared-sensitive surface temperature measuring device 13 is used. , 13A, the temperature measurement value is differentiated by the slab width direction distance or the measurement time, the end position of the slab 10 is confirmed, the surface temperature distribution in the slab width direction is determined based on the confirmed slab end part, The determined surface temperature distribution in the slab width direction is output to a separately provided monitor or storage device.

  By measuring the surface temperature of the slab 10 in this way, the secondary cooling water remaining on the slab surface, the water vapor generated from the secondary cooling water and It is possible to accurately and stably measure the surface temperature distribution in the width direction of the slab 10 during continuous casting without being affected by the white water smoke condensed with water vapor over a long period of time.

  In FIG. 1, the infrared-sensitive surface temperature measuring devices 13 and 13A are installed at one location in the casting direction. However, two or more locations in the casting direction may be used, and an infrared ray having two condenser lenses. Instead of the sensing surface temperature measuring device 13A, two infrared sensing surface temperature measuring devices 13 whose radiant energy measurement directions are opposite to each other may be arranged side by side in the slab width direction at the same position. Further, the condensing lens 16 is configured to be rotatable by 180 degrees with respect to the vertical line Z on the surface of the slab, and the infrared sensing type so that the moving direction of the infrared sensing type surface temperature measuring device coincides with the radiant energy measuring direction. It is also possible to measure while rotating the condenser lens according to the moving direction of the surface temperature measuring device 13. Furthermore, the continuous casting machine shown in FIG. 1 is a vertical bending type continuous casting machine, but the present invention is not limited to the vertical bending type continuous casting machine, and even if it is a curved type continuous casting machine, the vertical type Even in a continuous casting machine, the present invention can be applied in the same manner as described above.

  In the slab continuous casting machine shown in FIG. 1, an embodiment of the present invention using the infrared sensitive surface temperature measuring device shown in FIG. 2 will be described.

  The equipment length of the used slab continuous casting machine is 45 m, and the equipment is capable of casting a slab slab having a thickness of 250 mm and a maximum width of 2000 mm. The distance from the upper end of the mold to the lower end of the mold is 1 m, and the range of 44 m from the position immediately below the mold to the end of the machine is the secondary cooling zone. Then, it was divided into four secondary cooling zones, a first cooling zone, a second cooling zone, a third cooling zone, and a fourth cooling zone, and cooling conditions were set for each secondary cooling zone. In FIG. 1, the range from the AA ′ position to the slab support roll immediately above the BB ′ position is the first cooling zone, and the range from the BB ′ position to the slab support roll immediately above the CC ′ position. Is the second cooling zone, the range from the CC ′ position to the slab support roll immediately above the DD ′ position is the third cooling zone, the range from the DD ′ position to the slab support roll at the end of the machine is the first 4 cooling zones. An air mist spray nozzle is disposed in each secondary cooling zone of the secondary cooling zone, and the slab is cooled by the air mist sprayed from the air mist spray nozzle.

  The present invention was applied when casting a slab slab having a width of 2000 mm at a casting speed of 1.2 m / min using the slab continuous casting machine having this configuration (Invention Example 1).

  Infrared sensing type surface temperature measuring device in which the detecting element of the radiated light from the slab is Si semiconductor (wavelength = 0.91 μm) is second cooled so that the distance between the condenser lens and the slab surface is 300 mm. The surface of the slab is placed between the zone and the third cooling zone, the flow rate of the purge air ejected from the protective cover is set to 30 NL / min, and reciprocates over the slab width in the slab width direction. The temperature was measured. The infrared-sensitive surface temperature measuring instrument used is an infrared-sensitive surface temperature measuring instrument in which the radiant energy measuring direction of the condenser lens is inclined 3 degrees in the slab width direction with respect to the vertical line of the slab surface. The infrared sensitive surface temperature measuring device was reciprocated in one way 10 seconds and one reciprocation 20 seconds.

  FIG. 7 shows the measurement result of the surface temperature of the slab corresponding to the portion injected into the mold at the time when 15 minutes have elapsed from the start of casting. FIG. 7 shows temperature measurement values obtained when the infrared-sensitive surface temperature measuring instrument was moved to positions on the left and right sides of the reciprocating slider about 1000 mm each centering on the center position of the slab width. Since the measurement direction of the radiant energy of the condenser lens is inclined 3 degrees in the slab width direction with respect to the vertical line of the slab surface, at the end of the slab opposite to the radiant energy measurement direction of the condenser lens, The radiant energy of the short side of the slab is detected, and as shown in FIG. 7, the end of the slab whose temperature is relatively lower than the surrounding can be clearly identified, and the position A, which is the position of the minimum temperature, is the end of the slab. I was able to confirm that In addition, in the area | region on the left side from the A position of FIG. 7, the infrared sensitive surface temperature measuring device is measuring the temperature of the short side surface of a slab.

  FIG. 8 is a diagram showing a result obtained by differentiating the temperature measurement value shown in FIG. 7 by a slab width direction distance (distance interval = 0.01 mm). The position A shown in FIG. 8 corresponds to the position A shown in FIG. 7, and the position of the maximum value of the differential value coincides with the slab end. It was found that by providing a threshold value for the differential value, it is possible to reliably detect the end portion of the slab. The differential values shown in FIG. 8 are absolute values.

  In the slab continuous casting machine used in Example 1, a slab slab having a width of 2000 mm was cast at a rate of 1.2 m / min using an infrared sensitive surface temperature measuring instrument having two condenser lenses shown in FIG. The present invention was applied when casting at a speed (Invention Example 2).

  Infrared sensing type surface temperature measuring device using a Si semiconductor (wavelength = 0.91 μm) as the detection element of the radiated light from the slab, so that the distance between each condensing lens and the slab surface is 300 mm. 2 between the cooling zone and the third cooling zone, the flow rate of the purge air ejected from each protective cover is 30 NL / min, while reciprocating over the slab width in the slab width direction, The surface temperature of the slab was measured. The infrared-sensitive surface temperature measuring instrument used is an infrared-sensitive surface in which the radiant energy measurement direction of each condensing lens is inclined 3 degrees on the opposite side of the slab width direction with respect to the vertical line of the slab surface. It is a temperature measuring instrument. The infrared sensitive surface temperature measuring device was reciprocated in one way 10 seconds and one reciprocation 20 seconds.

  FIG. 9 shows the measurement results of the surface temperature of the slab corresponding to the portion injected into the mold at the time when 15 minutes have elapsed from the start of casting. The lower diagram of FIG. 9 shows the measurement of the surface temperature measured by the condensing lens arranged on the left side of FIG. 4 when the infrared sensitive surface temperature measuring instrument is moved from the left side to the right side of FIG. 9 shows the surface measured by the condenser lens arranged on the right side of the paper of FIG. 4 when the infrared-sensitive surface temperature measuring instrument is moved from the right side of the paper of FIG. 4 to the left side. The measured value of temperature is shown. In this case, both the left and right end positions of the slab could be easily determined from the temperature measurement value.

  For comparison, when carrying out Example 2 of the present invention, a handy-type two-dimensional infrared radiation thermometer was used, and a gap between the second cooling zone and the third cooling zone was desired from above the slab. The surface temperature distribution was measured (Comparative Example 1). The measurement wavelength of this two-dimensional infrared radiation thermometer is 7.5 to 14 μm. One minute after the temperature measurement according to Invention Example 2, the surface temperature distribution of the slab was measured with this two-dimensional infrared radiation thermometer. In FIG. 10, the measurement result by the comparative example 1 is shown with a broken line together with the measurement result of the surface temperature distribution of the slab in Example 2 of this invention.

  As shown in FIG. 10, in Comparative Example 1, the surface temperature drops in some places compared to the water temperature and the residual cooling water on the surface of the slab, and the surface temperature drops in places. It was confirmed that measurement was possible without any influence on water vapor or cooling water.

  For comparison, the surface temperature was measured using an infrared sensitive surface temperature measuring device in which the radiant energy measurement direction of the condenser lens was parallel to the vertical line of the slab surface (Comparative Example 2). This infrared sensitive surface temperature measuring instrument has the same specifications as the infrared sensitive surface temperature measuring instrument used in Example 2 of the present invention, except that the radiant energy measurement direction of the condenser lens is parallel to the vertical line of the slab surface. Yes, at a position on the downstream side of the slab support roll from the infrared-sensitive surface temperature measuring instrument used in Example 2 of the present invention, so that the distance between the condenser lens and the slab surface is 300 mm, The flow rate of purge air ejected from the protective cover was set to 30 NL / min.

  FIG. 11 shows the temperature distribution when this infrared-sensitive surface temperature measuring device is used to measure up to a range where no slabs exist at the same time as Example 2 of the present invention. As shown in FIG. 11, in Comparative Example 2, the temperature measurement value monotonously increases or monotonously decreases even when passing through the slab end, and it is unknown which position is the slab end. there were. On the other hand, in Example 2 of this invention, the minimum value of the temperature at the time of passing through the slab end portion could be obtained, and the slab end portion could be clearly confirmed.

DESCRIPTION OF SYMBOLS 1 Slab continuous casting machine 2 Tundish 3 Sliding nozzle 4 Immersion nozzle 5 Mold 6 Casting piece support roll 7 Conveying roll 8 Gas cutting machine 9 Molten steel 10 Cast piece 11 Solidified shell 12 Unsolidified phase 13 Infrared sensing type surface temperature measuring instrument 14 Conversion 15 Optical fiber 16 Condensing lens 17 Protective cover 18 Gas introduction pipe 19 Tie rod 20 Segment frame 21 Reciprocating slider 22 Support base

Claims (3)

  A method for measuring a slab surface temperature in a continuous casting machine, wherein the surface temperature of a slab during continuous casting is measured by an infrared-sensitive surface temperature measuring device, wherein Using an infrared sensitive surface temperature measuring instrument whose radiant energy measuring direction is inclined in the range of 1 to 60 degrees in the slab width direction with respect to the vertical line of the slab surface, The distance between the optical lens and the slab surface is within a range of 100 to 800 mm, and a gas of 10 NL / min or more is jetted from the infrared-sensitive surface temperature measuring instrument toward the slab, and the light is condensed by the gas. The surface temperature of the slab is measured with the infrared-sensitive surface temperature measuring instrument while discharging secondary cooling water and steam between the lens and the slab surface and from the temperature-measured portion of the slab. Slab in a continuous casting machine Method of measuring the surface temperature.   The infrared-sensitive surface temperature measuring device according to claim 1, wherein the infrared-sensitive surface temperature measuring device has two radiant energy measuring directions inclined to opposite sides of the slab width direction. A method for measuring a slab surface temperature in the continuous casting machine described.   The surface temperature of the slab is measured by reciprocating the infrared-sensitive surface temperature measuring device in the width direction of the slab, and the obtained temperature measurement value in the slab width direction is differentiated by the distance or measurement time in the slab width direction. The position of the maximum value of the differential value is determined as the end of the slab and the surface temperature distribution of the slab is measured, and the continuous casting machine according to claim 1 or 2, Method for measuring the slab surface temperature.

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