JP5804384B2 - Method and apparatus for measuring temperature of continuous casting mold copper plate - Google Patents

Description

  The present invention relates to a method and an apparatus for measuring the temperature of a mold copper plate constituting a continuous casting mold for molten metal (molten steel or the like) using ultrasonic waves. In particular, the present invention provides an ultrasonic reflection source having a hole that opens on the surface of the mold copper plate facing the molten metal and faces the molten metal, and has a hole extending inside the mold copper plate. Regardless, the present invention relates to a method and apparatus that can accurately measure the temperature of a cast copper plate.

  Conventionally, a thermocouple is embedded in a mold copper plate of a continuous casting machine used in a steelmaking process, and monitoring and control in the mold is performed by measuring the temperature of the mold copper plate with the thermocouple. More specifically, the temperature measured by the thermocouple is used to estimate the quality of the slab, as well as to predict and detect the breakout of the molten steel in the mold. Moreover, it is utilized also as a parameter | index for controlling the electromagnetic stirring apparatus and electromagnetic brake apparatus which were provided in the casting_mold | template. In general, the thermocouple is provided with a hole (a back surface of the mold copper plate (proximity to the molten steel) provided in the mold copper plate so that the temperature measuring point is located 5 to 20 mm away from the surface of the mold copper plate adjacent to the molten steel. It is opened in a surface facing the surface) and is installed in a hole) that extends into the interior of the mold copper plate.

  However, the attachment position of the thermocouple is adjacent to the path of the cooling water for the mold, and the mold is constantly exposed to vibration called oscillation. For this reason, the protective tube of the thermocouple may be corroded by the cooling water, or the cooling water may enter the thermocouple insertion hole, resulting in a large temperature measurement error.

  Further, the more thermocouples are installed, the more convenient the temperature (temperature distribution) of the mold copper plate can be measured in detail. In other words, if the temperature of the mold copper plate can be measured in detail, it is possible to predict and detect the breakout of molten steel more reliably, improve the estimation of the flow state of the molten steel and the estimation of the shell thickness. The effect that estimation accuracy improves can be expected. However, the installation of a large number of thermocouples causes a problem that the frequency of failure of the thermocouple increases. Especially in recent years, the quality of the slabs formed in the mold has been controlled by the electromagnetic stirring device and electromagnetic brake device provided in the mold, and because physical interference with these facilities occurs, Replacing and repairing a broken thermocouple has become extremely difficult.

  Furthermore, in order to measure the heat flux in cooling with the mold copper plate, it is necessary to measure the temperature at a point where the thickness direction of the mold copper plate (direction opposite to the molten steel) is different. It is necessary to accurately install thermocouples at different points in the thickness direction. However, the measurement accuracy by the thermocouple may deteriorate due to the influence of an induced current or the like by the electromagnetic stirring device or the electromagnetic brake device provided in the mold.

  For the purpose of solving the problems as described above, for example, a method for measuring the temperature of a mold copper plate as described in Patent Document 1 has been proposed. Specifically, Patent Document 1 shows a problem when measuring the temperature of the mold copper plate with a thermocouple, and particularly a problem when an electromagnetic stirrer is provided. A method is described in which an insertion hole opened at the upper surface and extending into the mold copper plate is provided, and a thermocouple is inserted into the insertion hole to measure the temperature at a predetermined position inside the mold copper plate.

Generally, as a thermocouple, a sheathed thermocouple having an outer shape of about φ3 mm to φ5 mm is used from the viewpoint of required mechanical strength, corrosion resistance, responsiveness, and the like. In order to install this thermocouple inside the mold copper plate, as shown in FIG. 1 of Patent Document 1, it is necessary to accurately open a narrow and deep insertion hole using a drill or the like.
However, it is difficult to make a deep insertion hole with a small diameter as described above. At least from the specifications of commercially available carbide drills and the like, when an insertion hole of about φ3 mm is opened in the mold copper plate, a depth of about 50 mm to 60 mm at most seems to be the limit. As shown in FIG. 1 of Patent Document 1, even when an insertion hole slightly larger than the thermocouple is opened from the upper surface of the mold copper plate, if the insertion hole is too large, the heat conduction of the mold copper plate is hindered. For this reason, for example, if an insertion hole of φ6 mm is opened, a depth of about 90 mm seems to be the limit. In other words, the temperature measuring point of the thermocouple inserted into the insertion hole is limited to a position higher than a position about 90 mm away from the upper surface of the mold copper plate.
In general, since a stable value cannot be obtained at the molten steel surface level due to the undulation of the molten steel surface, the temperature measurement region is a position that is lowered by several cm to 10 cm from the molten metal surface and a position below it. For this reason, for example, when a temperature measuring point is provided at a position 90 mm from the upper surface of the mold copper plate, the molten steel surface is at least several centimeters higher than the position, so that when a slight molten metal surface fluctuation occurs or in an unsteady state The risk of the molten steel overflowing from the mold increases. Further, the temperature measuring point is limited to a position higher than a position about 90 mm away from the upper surface of the mold copper plate. For this reason, the temperature at a position further lower than the position 90 mm away from the upper surface of the mold copper plate cannot be measured, and it may be insufficient for detecting a breakout of molten steel in the mold.
As described above, the method described in Patent Document 1 has the following problems.
(A) It is difficult to open an insertion hole having an appropriate depth, and the feasibility is poor.
(B) The temperature measuring point is limited to a range of about 90 mm downward from the upper surface of the mold copper plate. For this reason, there is a problem that there is a risk of overflow of the molten steel and that the breakout of the molten steel at a position below the temperature measuring point cannot be detected.

  In order to solve the problems as described above, the present inventors have proposed a method for measuring a temperature of a mold copper plate described in Patent Document 2. That is, the method described in Patent Document 2 is a method for measuring the temperature of a mold copper plate constituting a mold for continuous casting of molten metal, and is a first procedure in which an ultrasonic wave reflection source is provided inside the mold copper plate. And a second procedure for propagating ultrasonic waves from the ultrasonic transmitter / receiver toward the reflection source in a direction substantially parallel to the proximity surface of the mold copper plate with the molten metal, and reflected by the reflection source and And a third procedure for calculating the temperature of the mold copper plate based on the ultrasonic echo detected by the ultrasonic transceiver. More specifically, in the method described in Patent Document 2, as a reflection source provided in the first procedure, an opening is made on a surface of the mold copper plate facing a surface close to the molten metal, and the inside of the mold copper plate is opened. An extending hole is used.

The ultrasonic wave transmitted from the ultrasonic transmitter / receiver spreads by scattering during propagation in the mold copper plate. For this reason, in order to obtain a sufficient ultrasonic echo intensity, the reflection source provided far away from the ultrasonic transmitter / receiver has its area (projected area viewed from the ultrasonic propagation direction) according to the distance from the ultrasonic transmitter / receiver. ) Must be increased.
FIG. 1 is a diagram showing an example of a result of an actual investigation on a relationship between a distance from an ultrasonic transmitter / receiver to a reflection source, a projection area of the reflection source viewed from the ultrasonic wave propagation direction, and whether ultrasonic echoes can be detected. It is. The data plotted with “●” shown in FIG. 1 indicates that the intensity of the ultrasonic echo from the reflection source is sufficiently larger than the noise intensity, and the data plotted with “×” indicates the intensity of the ultrasonic echo from the reflection source. Shows the case where the noise intensity could not be distinguished from the noise intensity. As shown in FIG. 1, it can be seen that in order to obtain sufficient intensity of the ultrasonic echo from the reflection source, it is necessary to increase the projection area of the reflection source in accordance with the distance from the ultrasonic transceiver.
In particular, when transmitting and receiving ultrasonic waves from one ultrasonic transmitter / receiver to a plurality of reflection sources, the depth of the hole as a reflection source (dimension in the thickness direction of the mold copper plate) according to the distance from the ultrasonic transmitter / receiver Therefore, the position of the center of the reflection source (the position in the thickness direction of the casting copper plate) changes depending on the distance from the ultrasonic transceiver.

FIG. 2 is a diagram showing the relationship between the temperature distribution in the thickness direction of the mold copper plate and the center position of the reflection source. The “molten metal surface” shown in FIG. 2 means a surface of the mold copper plate close to the molten metal, and the “cooling surface” means a surface in contact with the cooling water for the mold copper plate.
If the ultrasonic echo is reflected from the entire surface of the reflection source facing the ultrasonic transducer and the temperature of the mold copper plate is measured using the entire reflected ultrasonic echo, the method described in Patent Document 2 When the center position of the reflection source is changed, the position in the thickness direction of the temperature-measured mold copper plate is changed. Therefore, as shown in FIG. 2, even if the temperature distribution in the thickness direction of the mold copper plate is uniform in the height direction of the mold copper plate, the position of the reflection source from the ultrasonic transceiver (the height direction of the mold copper plate). The temperature measurement value will be different depending on the position of. In the example shown in FIG. 2, the temperature calculated by the ultrasonic echo from the reflection source R1 is different from the temperature calculated by the ultrasonic echo from the reflection source R2 provided farther than this. More specifically, since the center position of the reflection source R2 is closer to the proximity surface to the molten metal than the center position of the reflection source R1, the temperature calculated by the ultrasonic echo from the reflection source R2 is reflected. It becomes higher than the temperature calculated by the ultrasonic echo from the source R1.

Japanese Patent No. 3797088 JP 2009-78298 A

  The present invention was made in order to solve such problems of the prior art, and is a method and apparatus for measuring the temperature of a mold copper plate constituting a mold for continuous casting of molten metal using ultrasonic waves, As an ultrasonic reflection source, when a hole is formed on the surface of the mold copper plate facing the surface close to the molten metal, and a hole extending inside the mold copper plate is provided, the mold is accurately obtained regardless of the depth of the hole. It is an object to provide a method and an apparatus capable of measuring the temperature of a copper plate.

In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, the mold copper plate and the mold copper plate determined by the temperature of the mold copper plate calculated using ultrasonic waves, the position of the center of the reflection source, and the cooling condition of the mold copper plate. The thickness direction of the mold copper plate (molten metal) based on the heat transfer coefficient with the cooling water for the mold, the casting width of the slab by the mold copper plate, the temperature of the cooling water on the inlet side of the mold copper plate and the temperature of the cooling water on the outlet side of the mold copper plate It was found that the temperature distribution in the opposite direction) can be estimated. Then, the present invention has been completed by conceiving that the problem can be solved by correcting the calculated temperature of the mold copper plate using the temperature distribution in the thickness direction of the mold copper plate.
That is, the present invention is a method for measuring the temperature of a mold copper plate that constitutes a mold for continuous casting of molten metal, and as a reflection source of ultrasonic waves, the surface of the mold copper plate facing a surface close to the molten metal. A first step of opening and providing a hole extending inside the mold copper plate; and toward the reflection source, the ultrasonic wave is transmitted in a direction substantially parallel to the proximity surface of the mold copper plate with the molten metal of the mold copper plate. Based on the second procedure for propagating the sound wave, the propagation time of the ultrasonic echo reflected by the reflection source and detected by the ultrasonic transceiver, and the temperature dependence of the propagation speed of the ultrasonic wave, the temperature of the mold copper plate For the mold copper plate and the mold copper plate determined by the temperature of the mold copper plate calculated in the third procedure, the position of the center of the reflection source, and the cooling condition of the mold copper plate. Heat transfer coefficient with cooling water, the casting Based on the casting width of the slab by the copper plate, the temperature of the cooling water on the mold copper plate entrance side, and the temperature of the cooling water on the mold copper plate exit side, the temperature distribution of the mold copper plate in the direction facing the molten metal is estimated, the third temperature of the mold copper plate, which is calculated in the procedure, using the temperature distribution the estimated, the fourth correcting the temperature of any position in the opposing direction of the molten metal in the mold copper plate And a temperature measuring method for a continuous casting mold copper plate.

According to the present invention, by executing the first to third procedures, the temperature of the casting copper plate (the average temperature from the incident point of the ultrasonic wave to the casting copper plate to the reflection source) can be calculated. . However, the calculated temperature of the mold copper plate is affected by the depth of the hole as a reflection source (the dimension in the opposing direction of the mold copper plate and the molten metal). Therefore, in the present invention, in the fourth procedure, first, the calculated mold copper plate temperature, the position of the center of the reflection source, and the mold copper plate determined by the cooling condition of the mold copper plate and the cooling water for the mold copper plate are used. Estimate the temperature distribution in the direction of the mold copper plate facing the molten metal based on the heat transfer coefficient, the casting width of the slab by the mold copper plate, the temperature of the cooling water on the inlet side of the mold copper plate and the temperature of the cooling water on the outlet side of the mold copper plate (Linear approximation). Next, the calculated temperature of the mold copper plate is corrected using the estimated temperature distribution. Thereby, it is possible to calculate the temperature at an arbitrary position in the thickness direction of the casting copper plate (direction facing the molten metal) regardless of the depth of the hole serving as the reflection source.

Further, in order to solve the above-mentioned problems, the present invention constitutes a mold for continuous casting of molten metal, and a hole that opens at a surface facing a surface close to the molten metal and extends inside is provided as an ultrasonic reflection source. An apparatus for measuring the temperature of the mold copper plate, the ultrasonic transceiver for propagating ultrasonic waves in a direction substantially parallel to a surface near the molten metal of the mold copper plate toward the reflection source, A calculation means for calculating a temperature of the mold copper plate based on a propagation time of an ultrasonic echo reflected by a reflection source and detected by the ultrasonic transceiver and a temperature dependence of an ultrasonic propagation speed; The means includes the calculated temperature of the mold copper plate, the position of the center of the reflection source, the heat transfer coefficient between the mold copper plate and the cooling water for the mold copper plate determined by the cooling condition of the mold copper plate, the mold copper plate Casting width of slab by, before Based on the temperature of the cooling water on the mold copper plate entry side and the temperature of the cooling water on the mold copper plate exit side, the temperature distribution of the mold copper plate facing the molten metal is estimated, and the calculated mold copper plate is calculated. The temperature of the mold is corrected to a temperature at an arbitrary position in the facing direction of the mold copper plate with respect to the molten metal using the estimated temperature distribution. Is done.

  According to the method and apparatus for measuring the temperature of a continuous casting mold copper plate according to the present invention, an opening is formed on the surface of the mold copper plate facing the proximity surface of the molten metal of the mold copper plate, and extends into the mold copper plate. When a hole is provided, it is possible to accurately measure the temperature of the mold copper plate regardless of the depth of the hole.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings, taking as an example a case where the molten metal is molten steel, the continuous casting mold is a rectangular tube shape, and the mold copper plate is a flat plate shape.

FIG. 3 is a diagram schematically showing a configuration example of a temperature measuring device for a continuous casting mold copper plate according to the present invention (hereinafter, abbreviated as “temperature measuring device” as appropriate). FIG. 3A is a diagram showing the schematic configuration of the temperature measuring device viewed from the width direction of the mold copper plate, and FIG. 3B is the schematic configuration of the temperature measuring device facing the back side of the mold copper plate (facing the surface close to the molten steel). 3 (c) shows a schematic configuration of the temperature measuring device viewed from above the mold copper plate. In FIG. 3A, the reflection sources R1 to R7 and the thermocouple TC are shown. In FIG. 3C, the light is transmitted through the reflection sources R1 to R7. In FIG. 3B and FIG. 3C, the transmission / reception control device 2 and the arithmetic control device 3 are not shown.
As shown in FIG. 3, the temperature measuring apparatus 100 according to the present embodiment is a mold copper plate in which a hole opened as a surface C2 facing the proximity surface C1 with the molten steel M and extending inward is provided as an ultrasonic reflection source R. This is a device for measuring the temperature of C. On the facing surface C2, cooling water channels WC for cooling the mold copper plate C are provided at a predetermined pitch. The temperature measuring apparatus 100 according to the present embodiment has an ultrasonic transmitter / receiver 1 that propagates an ultrasonic wave U in a direction substantially parallel to a proximity surface C1 with the molten steel M of the mold copper plate C toward the reflection source R; Calculation means for calculating the temperature of the mold copper plate C based on the propagation time of the ultrasonic echo reflected by the reflection source R and detected by the ultrasonic transceiver 1 and the temperature dependence of the propagation speed of the ultrasonic wave is provided. .

  As shown in FIG. 3, the temperature measurement apparatus 100 according to the present embodiment drives and controls the transmission / reception control apparatus 2 that controls transmission / reception of the ultrasonic wave U by the ultrasonic transmission / reception element 1, and the transmission / reception control apparatus 2. Computation control means 3 for computing the output signal from the transmission / reception control device 2 is provided. In the present embodiment, the calculation unit included in the calculation control device 3 functions as the calculation means described above.

Specific configurations of the ultrasonic transmitter / receiver 1 and the transmission / reception control device 2 are the same as those described in Patent Document 2 described above. The specific configuration of the reflection source R is also the same as the configuration described in Patent Document 2 described above. For this reason, the description about these specific structures is abbreviate | omitted here.
Hereinafter, the calculation contents in the calculation unit (calculation means) of the calculation control device 3 will be sequentially described.

The calculation unit of the calculation control device 3 includes a distance L from the ultrasonic transmitter / receiver 1 to the reflection source R (a distance from the upper surface of the mold copper plate C to the reflection source R, which is an ultrasonic incident point) L, and a previously obtained mold copper plate. The temperature dependence of the ultrasonic wave propagation speed in C (correspondence between propagation speed and temperature) is stored in advance.
Based on the echo signal output from the transmission / reception control device 2, the calculation unit calculates the propagation time T of the ultrasonic echo reflected by the reflection source R and detected by the ultrasonic transceiver 1.
Next, the calculation unit obtains the ultrasonic wave propagation speed by the following equation (1) based on the calculated propagation time T and the distance L from the ultrasonic transceiver 1 to the reflection source R.
Ultrasonic propagation speed = (distance L to the reflection source R) × 2 / propagation time T (1)
Finally, the calculation unit calculates the temperature of the mold copper plate C based on the propagation speed and the temperature dependence of the ultrasonic propagation speed stored in advance. This calculated temperature corresponds to the average temperature from the ultrasonic incident point (the upper surface of the casting copper plate C) to the reflection source R.
As a method for obtaining the temperature dependence of the ultrasonic wave propagation speed in the mold copper plate C, a method similar to the method described in Patent Document 2 described above can be used.

  After calculating the temperature of the mold copper plate C as described above, the calculation unit of the calculation control device 3 uses the calculated temperature Cu of the mold copper plate C and the cooling condition of the mold copper plate C for the mold copper plate C and the mold copper plate C. The heat transfer coefficient α with the cooling water, the casting width W of the slab (molten steel M) from the mold copper plate C, the temperature Ti of the cooling water on the inlet side of the mold copper plate C, and the temperature To of the cooling water on the outlet side of the mold copper plate C Based on the estimated temperature distribution Tmp of the mold copper plate C facing the molten steel M (the thickness direction of the mold copper plate C), the temperature distribution Tmp of the calculated mold copper plate C is corrected.

FIG. 4 is an explanatory diagram for explaining a method for estimating the temperature distribution Tmp in the direction of the mold copper plate C facing the molten metal (molten steel M) (the thickness direction of the mold copper plate C).
The mold copper plate C plays a role of transferring heat from the molten steel M to the cooling water for the mold copper plate C. For this reason, when estimating the temperature distribution Tmp in the thickness direction of the mold copper plate C, it is necessary to estimate the amount of heat in the mold copper plate C. The amount of heat input per unit time from the molten steel M to the mold copper plate C varies depending on the temperature of the molten steel M and the casting speed. On the other hand, the amount of heat removed from the mold copper plate C per unit time varies depending on the amount of cooling water for the mold copper plate C, the temperature Ti of the cooling water on the inlet side of the mold copper plate C, and the temperature To of the cooling water on the outlet side of the mold copper plate C. To do. Further, the heat removal amount also varies depending on the casting width W of the slab. Temporarily, the maximum casting width Wmax of the slab which can be cast with a mold is 2000 mm, and a cooling water channel WC for cooling the mold copper plate C is provided over 2000 mm in the width direction of the mold copper plate C to cope with this. Suppose that In this case, since the cooling water channel WC that actually contributes to heat removal changes between the case where the actual casting width W of the slab is 2000 mm and 1000 mm, the amount of heat removed from the mold copper plate C also changes. . For this reason, for example, even if the difference between the cooling water temperature Ti on the mold copper plate C entry side and the cooling water temperature To on the mold copper plate C exit side is 5 ° C., the temperature distribution Tmp in the thickness direction of the mold copper plate C is It will be very different.
Therefore, in order to estimate the temperature distribution Tmp in the thickness direction of the mold copper plate C, the amount of cooling water for the mold copper plate C (in other words, the heat transfer coefficient α between the mold copper plate C and the cooling water for the mold copper plate C). The casting width W of the slab (molten steel M) from the mold copper plate C, the cooling water temperature Ti on the mold copper plate C entry side, and the cooling water temperature To on the mold copper plate C exit side are required.

Based on the idea as described above, specifically, as shown in FIG. 4, the distance (distance in the thickness direction of the mold copper plate C) Z from the adjacent surface C1 to the molten metal (molten steel M) is represented by the horizontal axis. When the temperature T of the mold copper plate C is the vertical axis, the temperature distribution Tmp of the mold copper plate C is approximated by a straight line passing through two points (Zu, Tu) and (Zb, Tw). More specifically, the temperature distribution Tmp is expressed by the following formulas (2) to (6).
Tmp = aa × Z + bb (2)
aa = G1 (Tw−Tu) / (Zb−Zu) + G2 (3)
Tw = (Ti−To) × Wmax / W (4)
Zb = f (α) + G3 (5)
bb = Tw−aa × Zb (6)
Here, Zu means the center position of the reflection source R (position in the thickness direction of the mold copper plate C), and Tu means the temperature Tu of the mold copper plate C calculated as described above. Zb means the position in the thickness direction of the mold copper plate C where the temperature Tw is considered to be obtained, and the cooling conditions of the mold copper plate C (the amount of cooling water, the depth of the cooling water channel WC, the pitch, and the molten steel M It is represented by a function f (α) of the heat transfer coefficient α determined by the distance from the proximity surface C1). Furthermore, G1, G2, and G3 are constants (in the embodiment described later, G1 = 1, G2 = G3 = 0).

  In order to obtain Zb, for example, the following method can be considered. First, various cooling conditions of the mold copper plate C are changed offline (that is, the heat transfer coefficient α is changed to various values), and a plurality of positions different in the thickness direction of the mold copper plate C by the thermocouple TC are set. Measure the temperature. Next, heat transfer calculation such as a difference method is performed using these temperature measurement results, and a position Zb in the thickness direction of the mold copper plate C at which the temperature Tw is obtained is determined for each heat transfer coefficient α. Finally, regression calculation is performed using the determined position and the heat transfer coefficient α when the position is obtained as parameters, and the relationship between the two is calculated. That is, Zb is expressed as a function of the heat transfer coefficient α.

The heat transfer coefficient α is expressed by the following formula (7).
α = Nu × λ / L (7)
Here, Nu is the Nusselt number, λ is the thermal conductivity of water, and L is the representative length of the cooling water channel WC. Specifically, L is represented by the following formula (8).
L = 4 × (cross-sectional area of cooling water channel WC) / (wetting edge length of cooling water channel WC) (8)

The Nusselt number Nu is expressed by the following equation (9) (Colburn equation) in the case of turbulent pipe flow.
Nu = 0.023 × Re ^4/5 × Pr ⁿ (when cooling, n = 0.3) (9)
Here, Re is the Reynolds number, the flow rate of cooling water in the cooling water channel WC is U, the kinematic viscosity coefficient of water is ν, and the representative length of the cooling water channel WC is L as described above, the following equation: It is represented by (10). Pr means the Prandtl number.
Re = U × L / ν (10)

  As described above, if the temperature distribution Tmp in the thickness direction of the mold copper plate C is estimated, the calculated temperature Tu of the mold copper plate C is the position where the distance from the proximity surface C1 to the molten steel M is Zu (of the reflection source R). Even if the center position is the temperature at Zu), it is possible to correct the temperature at an arbitrary position Z in the thickness direction of the mold copper plate C. That is, the temperature Tmp at the position Z can be calculated by substituting the position Z where the temperature is to be calculated into the above-described equation (2).

Hereinafter, an example of a result obtained by performing a continuous casting test using a vertical bending type continuous casting machine and measuring the temperature of the mold copper plate C using the temperature measuring apparatus 100 according to the present embodiment will be described.
As shown in FIG. 3, a total of seven ultrasonic transceivers 1 are installed on the upper surface of the mold copper plate C, and the reflection sources R (R1 to R7) are included in the propagation path of the ultrasonic wave U transmitted from each ultrasonic transceiver 1. ) Are provided one by one. In the reflection sources R1 and R2, the distance from each other in the width direction of the mold copper plate C was set to 20 mm, and the distance from the upper surface of the mold copper plate C was set to 200 mm. In addition, the reflection sources R3 to R5 have a distance of 20 mm from each other in the width direction of the mold copper plate C and a distance from the upper surface of the mold copper plate C of 300 mm. Further, in the reflection sources R6 and R7, the distance from each other in the width direction of the mold copper plate C is set close to 20 mm, and the distance from the upper surface of the mold copper plate C is set to 500 mm. The center position of the reflection sources R5 and R7 (position in the thickness direction of the casting copper plate C) was 13 mm from the proximity surface C1 with the molten steel M. The center position of the reflection sources R1, R4, and R6 (position in the thickness direction of the mold copper plate C) was set to 18 mm from the proximity surface C1 with the molten steel M. Furthermore, the center position of the reflection sources R2 and R3 (position in the thickness direction of the mold copper plate C) was 23 mm from the proximity surface C1 with the molten steel M.
Further, in order to compare and verify the temperature measurement results obtained by the temperature measuring device 100, a thermocouple TC was installed in the vicinity of each reflection source R. The temperature measuring point of the thermocouple TC (the tip of the thermocouple TC) was placed 18 mm from the proximity surface C1 with the molten steel M.

Results of calculating the temperature of the mold copper plate C based on the ultrasonic echoes reflected from the respective reflection sources R1 to R7 and detected by the respective ultrasonic transceivers 1 (conditions 1 to 7), and calculated according to the conditions 2, 3, 5, and 7. Table 1 shows the results (conditions 8 to 11) of correcting the calculated temperature using the estimated temperature distribution Tmp.

  As shown in Table 1, the center position of the reflection source R1 (position in the thickness direction of the mold copper plate C) is equal to the temperature measuring point of the thermocouple TC (both are 18 mm from the proximity surface C1 with the molten steel M). The temperature measurement value is almost the same as the instruction of the thermocouple TC. However, in the condition 2 where the center position of the reflection source R2 is farther from the proximity surface C1 with the molten steel M than the temperature measurement point of the thermocouple TC (23 mm from the proximity surface C1 with the molten steel M), the temperature measurement value is that of the thermocouple TC. Lower than indicated.

On the other hand, in the condition 8 in which the temperature calculated in the condition 2 is corrected using the estimated temperature distribution Tmp, the temperature measurement value is almost the same as the instruction of the thermocouple TC.
The procedure for correction under condition 8 is specifically as follows.
First, when the above-described equation (5) was obtained (G3 = 0) based on an off-line test performed by variously changing the cooling conditions of the mold copper plate C, the following equation (5) ′ was obtained.
Zb = 2.62 × 10 ⁻⁵ × α × 14.38 (5) ′
When the heat transfer coefficient α derived from the above-described equations (7) to (10) from the cooling condition of the mold copper plate C under the condition 2 (the same cooling condition as the condition 8) is substituted into the above equation (5) ′. Zb = 28.4 mm was obtained.
In condition 2, the center position Zu of the reflection source R2 is 23 mm, and the temperature measurement value Tu is 67 ° C.
Furthermore, in Condition 2 (Condition 8 is the same), the temperature difference Ti-To = 38 ° C., the maximum casting width Wmax = 1250 mm, and the actual casting width W = 1200 mm of the cooling water on the inlet side and the outlet side of the mold copper plate C. From the above-described formula (4), Tw = 36 ° C.
Substituting the above Tw = 36 ° C., Tu = 67 ° C., Zb = 28.4 mm, and Zu = 23 mm into the above-described equation (3) (G1 = 1, G2 = 0), aa = −5.74 is obtained. Obtained. Moreover, when Tw = 36 ° C., aa = −5.74, and Zb = 28.4 mm were substituted into the above-described formula (6), bb = 199 was obtained.
Accordingly, the temperature distribution Tmp is estimated by the following equation (2) ′ from the above equation (2).
Tmp = −5.74 × Z + 199 (2) ′
In this equation (2) ′, when Z is 18 mm, which is equal to the temperature measuring point of the thermocouple TC, Tmp = 96 ° C.
As described above, the condition 8 is obtained by correcting the temperature measurement value in the condition 2 to a temperature at a position equal to the temperature measurement point of the thermocouple TC using the temperature distribution Tmp. It can be seen that the temperature measurement value is almost the same as the instruction of the thermocouple TC. Similarly, Condition 9 is a temperature measurement value under Condition 3, Condition 10 is a temperature measurement value under Condition 5, and Condition 11 is a temperature measurement value under Condition 7, using the estimated temperature distribution Tmp. It is corrected to the temperature at a position equal to the temperature measurement point of TC, and it can be seen that the temperature measurement value after correction is almost the same as the instruction of the thermocouple TC.

  FIG. 5 shows an example of the temperature measurement result of the mold copper plate C when 250 tons of molten steel M is continuously cast. The conditions 1, 2 and 8 shown in FIG. 5 (the position of the reflection source R) are the same as those shown in Table 1 described above. As shown in FIG. 5, there is a large difference in the measured temperature value depending on the position of the reflection source R between the condition 1 and the condition 2, but the temperature measurement value Tmp is used for correction (condition 8 is corrected) (Temperature measurement value)), it can be seen that the difference in temperature measurement value hardly occurs.

FIG. 1 is a diagram showing an example of a result of an actual investigation on a relationship between a distance from an ultrasonic transmitter / receiver to a reflection source, a projection area of the reflection source viewed from the ultrasonic wave propagation direction, and whether ultrasonic echoes can be detected. It is. FIG. 2 is a diagram showing the relationship between the temperature distribution in the thickness direction of the mold copper plate and the center position of the reflection source. FIG. 3 is a diagram schematically showing a configuration example of a temperature measuring device for a continuous casting mold copper plate according to the present invention. FIG. 4 is an explanatory diagram for explaining a method for estimating a temperature distribution in a direction in which the mold copper plate faces the molten metal. FIG. 5 shows an example of the temperature measurement result of the mold copper plate when 250 tons of molten steel M is continuously cast.

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic transmitter / receiver 2 ... Transmission / reception control apparatus 3 ... Calculation control apparatus (calculation means)
100 ... Temperature measuring device C for mold copper plate for continuous casting C ... Mold copper plate M ... Molten metal (molten steel)
R ... Reflection source
U ... Ultrasonic

Claims (2)

A method for measuring the temperature of a mold copper plate constituting a continuous casting mold for molten metal,
As a reflection source of ultrasonic waves, a first procedure is provided in which a hole is opened on a surface of the mold copper plate that faces a surface close to the molten metal and extends into the mold copper plate;
A second procedure for propagating ultrasonic waves from the ultrasonic transmitter / receiver toward the reflection source in a direction substantially parallel to a surface near the molten metal of the mold copper plate;
A third procedure for calculating the temperature of the mold copper plate based on the propagation time of the ultrasonic echo reflected by the reflection source and detected by the ultrasonic transceiver and the temperature dependence of the propagation speed of the ultrasonic wave;
The temperature of the mold copper plate calculated in the third procedure, the position of the center of the reflection source, and the heat transfer coefficient between the mold copper plate and the cooling water for the mold copper plate determined by the cooling condition of the mold copper plate, Based on the casting width of the slab by the mold copper plate, the temperature of the cooling water on the mold copper plate entrance side and the temperature of the cooling water on the mold copper plate exit side, the temperature distribution in the direction of the mold copper plate facing the molten metal And the temperature of the mold copper plate calculated in the third procedure is corrected to a temperature at an arbitrary position in the direction of facing the molten metal of the mold copper plate using the estimated temperature distribution. And a temperature measurement method for a continuous casting mold copper plate. A device for measuring the temperature of a mold copper plate, which comprises a mold for continuous casting of molten metal, and has a hole opened as a reflection source of ultrasonic waves, which is opened at a surface facing a surface close to the molten metal and extends inside,
An ultrasonic transmitter / receiver for propagating ultrasonic waves in a direction substantially parallel to a surface near the molten metal of the mold copper plate toward the reflection source;
Based on the propagation time of the ultrasonic echo reflected by the reflection source and detected by the ultrasonic transceiver and the temperature dependence of the propagation speed of the ultrasonic wave, the calculation means for calculating the temperature of the mold copper plate,
The calculation means includes the calculated temperature of the mold copper plate, the position of the center of the reflection source, and the heat transfer coefficient between the mold copper plate and the cooling water for the mold copper plate determined by the cooling condition of the mold copper plate, Based on the casting width of the slab by the mold copper plate, the temperature of the cooling water on the mold copper plate entrance side and the temperature of the cooling water on the mold copper plate exit side, the temperature distribution in the direction of the mold copper plate facing the molten metal And the calculated temperature of the mold copper plate is corrected to a temperature at an arbitrary position in the direction of facing the molten metal of the mold copper plate using the estimated temperature distribution. Temperature measuring device for mold copper plate.

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