JPH09201666A - Method for controlling temperature of molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contribute to the improvement of the quality of a cast block as the product by estimating the temp. drop in a high accuracy according to the molten metal tapping from a furnace and accurately matching the molten metal temp. at the time of pouring the molten metal into a mold to a suitable temp. SOLUTION: The temp. dropping degree arithmetic part 31 reads the operational conditions from an operational condition file 34 and these operational conditions are applied to a specified arithmetic formula and a specified dropping degree ΔT1 of molten steel temp. after tapping to casting time, is obtd. and given to a dropping degree correcting part 32. The dropping degree correcting part 32 uses the temp. measured value Tcc of the inner wall refractory of a ladle completing the casting and the operational conditions read out from the operational condition file 34, and the dropping degree of the molten steel temp. by heat conduction of the inner wall refractory at the time of tapping is calculated. Further, a time needed to the steel tapping is obtd. by using the operational conditions related to the steel tapping time read out from the operational condition file 34 and the dropping degree of the molten steel temp. by heat radiation during steel tapping is calculated. A ΔT1 is corrected with the calculated result and the dropping degree ΔT of the molten steel temp. is obtd. and given to an objective temp. setting part 33 for setting the objective temp. at the time of tapping the molten steel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, in a steelmaking process for producing a steel ingot as a raw material for steel plates, steel pipes, etc. The present invention relates to a temperature control method that is carried out to maintain an appropriate temperature when pouring.

[0002]

2. Description of the Related Art Molten steel (molten metal) produced in a steelmaking furnace such as a converter or an electric furnace is tapped in a ladle through a tapping opening (a tap opening) which is opened in a part of the steelmaking furnace. Steelmaking process, which is carried out to obtain a steel ingot (ingot) corresponding to the shape of the mold by pouring the molten metal into a mold of a continuous casting facility or an ingot-making facility after transporting it along a predetermined path. In the above operation, in order to stably obtain a high quality product steel ingot, it is important to keep the temperature of the molten steel proper at the time of pouring the molten metal into the mold.

The molten steel in the steelmaking process is adjusted in temperature by blowing control in a steelmaking furnace to be tapped in a ladle, and is radiated to the atmosphere during transportation by the ladle, and in the middle of the transportation route. Due to heat loss associated with various treatments in the secondary refining device, the temperature is gradually lowered to reach the pouring position in the mold, where it is poured into the mold through the tundish for storing molten steel. The ladle that has finished pouring is returned to the front of the steelmaking furnace to be preheated and reused to receive the next tapping.

An arithmetic expression for determining the amount of molten steel temperature drop that occurs during transportation by a ladle has been established as a function of operating conditions, including the time required in each processing step during transportation, and in operating the steelmaking process. Applies the operating conditions adopted in the operation to the above calculation formula to obtain the predicted drop in molten steel temperature that occurs between the time of tapping in the steelmaking furnace and the pouring into the mold. By determining the target temperature at the time of tapping from the steelmaking furnace in addition to the appropriate temperature during hot water, and by performing blowing control to achieve the obtained target temperature,
A method of controlling the molten steel temperature of the entire steel making process is adopted.

[0005]

However, even when the target temperature at the time of tapping, which is determined as described above, is correctly realized, the molten steel temperature at the time of pouring into the mold, which is the final stage, matches the appropriate temperature. Often not, in this case
In addition to the difficulty in ensuring the quality of the product steel ingot, when the molten steel temperature at the time of pouring is too high, damage to the refractory material lined in the tundish that stores the molten steel before pouring into the mold is accelerated, resulting in high frequency. When it was forced to change, the productivity was lowered, and when the molten steel temperature at the time of pouring was too low, the coolant was used unnecessarily for the temperature control in the blowing control in the steelmaking furnace. Therefore, there is a problem that the steelmaking cost is increased.

The above inconsistency in molten steel temperature is due to the fact that the temperature drop due to tapping from the steelmaking furnace to the ladle is not taken into consideration. The ladle that receives the steel output from the steelmaking furnace and conveys it to the mold is in a state where it is cooled by contact with the atmosphere during the empty pan period until it is returned to the front of the steelmaking furnace after the pouring is completed. The molten steel tapped from the steelmaking furnace is heated by the contact with the inner wall refractory material lined in the ladle when it flows into the ladle, and the temperature is lowered. As mentioned above, the ladle is preheated before the tapping is received, but the temperature of the molten steel tapped from the steelmaking furnace is sufficiently higher than the temperature of the inner wall refractory of the ladle after preheating, It does not prevent the temperature drop at.

Japanese Patent Laid-Open Nos. 1-246313 and 3-161161
Japanese Patent Publication proposes a molten steel temperature management method that solves the above-mentioned problems by taking into account the temperature drop during tapping and correcting the target temperature at tapping determined as described above. Has been done.

According to the method disclosed in Japanese Patent Laid-Open No. 1-246313, a plurality of thermocouples are embedded in a ladle for conveying molten steel, the temperature of the refractory on the inner wall at the time of receiving the tapped steel is measured, and the measured result is used to measure the inner wall. This is a method in which the amount of heat removed by the refractory is obtained, the amount of temperature drop of molten steel that occurs during tapping is estimated, and the target temperature for tapping determined as described above is corrected based on this estimation result.

However, in this method, it is necessary to embed a thermocouple in each of the plurality of ladles that circulate between the steelmaking furnace and the mold, which requires a great amount of initial cost for maintenance work. There is a problem that it is troublesome and impractical. Furthermore, since the temperature measurement result immediately before tapping is used to correct the tapping temperature, it cannot be used for setting the target temperature for the relevant charge, and is used for setting the target temperature for the next charge using another ladle. Therefore, the obtained target temperature includes the error due to the individual difference of the ladle,
There was a problem that the setting accuracy of the target temperature was low.

On the other hand, in the method disclosed in Japanese Patent Laid-Open No. 3-161161, the surface temperature of the refractory on the inner wall of the ladle is radiated before the preheating of the ladle, which is carried out as described above in preparation for receiving the tapped steel. Measure with a ladle thermometer such as a thermometer, calculate the heat storage amount of the ladle from this measurement result, and calculate the heat supply amount and heat radiation amount expected in each process of preheating, tapping, transportation and secondary refining. This is a method of sequentially adding and subtracting to determine the target temperature at the time of tapping, which is necessary to bring the molten steel temperature at the time of pouring to an appropriate value.

In this method, the temperature of the refractory on the inner wall of the ladle may be measured under the condition of an empty ladle, and a single ladle thermometer placed in front of the preheating device is commonly used. Although it has the advantage that it can be heated and is easy to carry out, the temperature of the molten steel is controlled in each subsequent process by relying only on the temperature measurement value of the ladle before preheating, so it is estimated in each process. There is a problem that the accuracy of the final estimation result decreases due to the accumulation of errors. Further, the thermal behavior of the refractory on the inner wall of the ladle differs depending on the past use history such as the number of uses involving contact with molten steel, the presence or absence of repair, etc. There is a problem that the accuracy of the estimation result further deteriorates because the ladle is uniformly estimated.

Further, the temperature drop of molten steel at the time of tapping from the steelmaking furnace is caused not only by the heat removal due to the contact with the ladle mentioned above but also by the heat radiation to the periphery from the start to the end of tapping. However, this temperature drop is not considered in the conventional method, and an error due to this temperature drop may occur in the molten steel temperature at the time of pouring the molten metal into the mold, which may reduce the accuracy of matching to the proper temperature. It was

The above problems occur not only in the steel making process but also in the same kind of process for manufacturing other metals.

The present invention has been made in view of such circumstances, and accurately estimates the temperature drop of the molten metal due to tapping from the furnace, and sets the temperature of the molten metal at the time of pouring the molten metal to an appropriate temperature. It is an object of the present invention to provide a method for temperature control of molten metal which can contribute to the quality improvement of a product ingot by making a correct match.

[0015]

A method for controlling the temperature of molten metal according to the present invention is one in which molten metal produced in a furnace is tapped into a ladle via a tap hole and is poured into a mold after being conveyed by the ladle. While pouring the molten metal to obtain the desired ingot, preheat the ladle after pouring and return it to the front of the furnace to accept the new molten metal during operation of the molten metal temperature during pouring. In order to maintain a predetermined temperature, the temperature drop amount of the molten metal that occurs between the tapping and the pouring is calculated by a predetermined calculation formula,
In addition to the predetermined temperature of this calculation result, in the temperature control method of the molten metal for determining the target temperature at the time of tapping, the temperature of the inner wall refractory of the ladle is measured after the pouring is completed, and this measurement result And a first correction value indicating a temperature drop amount of the molten metal caused by heat removal of the inner wall refractory at the time of tapping, based on a usage history of the inner wall refractory and a scheduled time until the next tapping. And a second correction value indicating the amount of temperature drop caused by heat dissipation during the tapping is calculated based on the planned amount of molten metal tapped in the ladle and the usage history of the tapping port. Then, the temperature drop amount calculated by the arithmetic expression is corrected by the first and second correction values.

In the present invention, the amount of temperature drop that occurs between the pouring of the hot water from the furnace and the pouring of the molten metal into the mold is calculated by a predetermined arithmetic expression, and the result is extracted when the refractory on the inner wall of the ladle is discharged. The corrected temperature drop amount is corrected by the first correction value indicating the temperature drop amount due to heat and the second correction value indicating the temperature drop amount due to heat radiation to the surroundings during hot water discharge. In addition to the proper temperature to be achieved at the time of pouring, the target temperature for tapping is determined.

The first correction value is the temperature of the inner wall refractory material measured after the completion of pouring into the mold and the use history of the inner wall refractory material of the ladle (the number of times of use, the presence or absence of repair, the degree of repair, etc.). After the completion of the pouring, the scheduled time from the start of the next hot water, specifically, the scheduled time from the completion of pouring to the start of preheating, the time required for preheating, and the completion of preheating. It is calculated based on the scheduled time required to wait until the start of hot water. This correction value is obtained at the time of completion of pouring, and can be used for temperature control at the time of the next hot water discharge after a certain time.

The second correction value is calculated by estimating the time required for tapping on the basis of the planned amount of tapping at each tapping time and the use history of the tapping mouth, and using this estimated time. The area of the tap hole increases as the number of times of use increases due to the melting damage that occurs each time tapping occurs due to contact with the melt. The usage history of the hot water outlet is used to estimate the area of the hot water outlet at the time of tapping, and the amount of hot water discharged is divided by this area to obtain the time required for hot water outlet.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a schematic diagram showing the overall construction of a steelmaking process in which a method for controlling the temperature of molten metal according to the present invention (hereinafter referred to as the method of the present invention) is carried out.

In the figure, 1 is a converter as a steelmaking furnace for producing molten steel, 2 is a continuous casting machine, and between the converter 1 and the continuous casting machine 2, there is a circulation between them. Is provided with a plurality of ladles 4, 4 ... Which are movable along the conveyance path 3.

In the converter 1, main raw materials such as hot metal and scrap iron and a solvent medium such as mill scale and iron sand are charged, and these are ignited by blowing high-pressure oxygen, and then quicklime, iron ore, The molten steel 5 having a desired composition is produced by performing blowing in which the amount of the high-pressure oxygen blown in is adjusted while introducing an auxiliary material such as fluorite. During this blowing, a part of the auxiliary material acts as a coolant, and the temperature of the molten steel 5 produced in the converter 1 is adjusted by the amount of high-pressure oxygen blown and the amount of coolant introduced. . This adjustment is performed by the operation of the blowing control unit 10 attached to the converter 1.

The converter 1 is a barrel-shaped container having an input port for raw materials and auxiliary raw materials on the upper surface, and has an tapped hole 1a with an opening in the upper half of the peripheral wall thereof. The generated molten steel 5 is transferred from the converter 1 tilted around a horizontal axis as shown by a broken line in the figure to the ladle 4 stopped at a corresponding position on the transfer path 3 via the tap hole 1a. The steel is tapped inside and is conveyed toward the continuous casting machine 2 by the movement of the ladle 4.

A secondary refining section 6 is formed in the middle of the moving path of the ladle 4 from the converter 1 to the continuous casting machine 2.
The molten steel 5 conveyed along with the movement of the ladle 4 has its components adjusted while being passed through the secondary refining section 6 by treatments such as addition of various additives and bubbling for removing inclusions, and continuous casting. The type of steel meets the requirements of the machine 2 and reaches the position where the continuous casting machine 2 is installed.

The continuous casting machine 2 is equipped with a sliding nozzle 21 continuously provided at the bottom of a tundish 20 as a molten steel container.
Has a structure in which it is extended downward and is inserted into a cylindrical mold 22 having upper and lower openings for an appropriate length. Molten steel 5 in ladle 4
After being supplied to the inside of the tundish 20 and temporarily stored therein, the amount is adjusted by adjusting the opening degree of the sliding nozzle 21, and the molten metal is poured into the mold 22, and the outside is contacted with the water-cooled inner wall of the mold 22. The slab 50 is cooled from the outside and becomes a slab 50 whose outside is covered with a solidification shell, which is continuously drawn out below the mold 22, and solidified to the inside by cooling during this drawing, and successively to a predetermined length. The product steel ingot is obtained by cutting.

The ladle 4 which has been poured into the continuous casting machine 2 is
It further moves along the conveying path 3, reverses its direction to the converter 1, passes through the corresponding position of the converter 1 and then reverses direction again to receive the next tapped steel. Returned to the front of the furnace. A temperature measuring station 7 is provided near the continuous casting machine 2 and a preheating device 8 is provided near the converter 1 in the middle of the transfer path 3 from the continuous casting machine 2 to the converter 1.

The temperature measuring station 7 is provided with a ladle thermometer 70 such as a radiation thermometer, and the ladle 4 which has become an empty pot by pouring the continuous casting machine 2 is moved to the converter 1. In the meantime, it is stopped at the temperature measuring station 7. During this period, the ladle thermometer 70 measures the surface temperature of the refractory material lined in the ladle 4, and outputs the result to the process control unit 30. The process control unit 30 recognizes the temperature T _{cc of the} refractory on the inner wall of the ladle 4 after the pouring is completed by the input from the ladle thermometer 70.

The preheating device 8 preheats the refractory on the inner wall of the ladle 4 which is cooled by heat radiation to the atmosphere during the transportation from the continuous casting machine 2 before receiving the tapped steel from the converter 1 and outputs it. It serves to suppress the temperature drop of the molten steel 5 caused by heat removal from the inner wall refractory during steel. This preheating, as shown,
The upper opening of the ladle 4 is covered with a cover plate 80, and the flame is emitted from a burner protruding inward from the cover plate 80 for a predetermined time in accordance with an operation command from the process control unit 30.

The output of the process control unit 30 is also given to the blowing control unit 10 of the converter 1, and the temperature of the molten steel 5 generated inside the converter 1 is an operation command from the process control unit 30. It is adjusted according to.

FIG. 2 is a block diagram showing the internal structure of the process control unit 30. The process control unit 30 includes a temperature drop amount calculation unit 31, a drop amount correction unit 32, a target temperature setting unit 33, and an operation condition file 34. The operating condition file 34 stores the operating conditions for each charge of the steelmaking process, including the proper temperature T _a required for the molten steel 5 at the time of pouring the molten metal into the continuous casting machine 2. It is adapted to be given to the drop amount calculation unit 31, the drop amount correction unit 32, and the target temperature setting unit 33.

The temperature drop amount calculation unit 31 has an operation formula for obtaining the predicted drop amount ΔT ₁ of the temperature of the molten steel 5 which occurs after the steel is tapped from the converter 1 and is poured into the continuous casting machine 2. I remember it. This arithmetic expression is, for example, the processing time and processing content in the secondary refining section 6, the time required for pouring the molten metal into the continuous casting machine 2,
It is given as a function of operating conditions A _i , a _{i in} each process during the transfer from the converter 1 to the continuous casting machine 2 as shown in the following equation.

ΔT ₁ = ΣA _i × t ₁ + Σa _i (1)

A _i is an operating condition in which the influence on the molten steel temperature is related to the required time t ₁ for the transportation, and a _i
Are operating conditions that have no effect on the required time t ₁ on the molten steel temperature. These are the operating condition files.
Stored in 34. The temperature drop amount calculation unit 31 reads the operating condition of the charge from the operating condition file 34 prior to the operation of each charge in the steelmaking process, and applies this to the calculation formula to calculate the predicted drop amount ΔT ₁ , This result is given to the descent amount correction unit 32.

Predicted fall amount ΔT ₁ obtained by the equation (1)
Indicates the amount of temperature drop of the molten steel 5 that occurs after the steel is tapped out of the converter 1 and before pouring into the continuous casting machine 2 is completed. It also occurs during tapping from the ladle to the ladle 4. The drop amount correction unit 32 obtains a correction amount ΔT ₂ indicating the temperature drop of the molten steel 5 that occurs during the tapping, corrects the predicted drop amount ΔT _{1 based} on this result, and the molten steel 5 that occurs in the entire steelmaking process. The temperature drop amount ΔT is calculated and the result is given to the target temperature setting unit 33.

ΔT = ΔT ₁ + ΔT ₂ (2)

The target temperature setting unit 33 adds the temperature drop amount ΔT given from the drop amount correction unit 32 to the proper temperature T _a of the molten steel 5 at the time of pouring the molten steel into the continuous casting machine 2 and then from the converter 1. The target temperature T of the molten steel 5 at the time of tapping is determined and the result is given to the blowing control unit 10.

T = T _a + ΔT (3)

The feature of the method of the present invention is that the fall amount correction unit 32 is used.
The calculation procedure of the correction amount ΔT ₂ in FIG. FIG. 3 is a flowchart showing this calculation procedure. The correction amount ΔT ₂ is calculated by the predicted drop amount ΔT ₁ in the temperature drop amount calculation unit 31.
Similar to the above equation, the operating condition B _i , in which the influence on the molten steel temperature is related to the time t ₂ required for tapping from the converter 1, and the operating condition b, in which the influence on the molten steel temperature is independent of the time t _2. It is performed using the following equation including _i and.

ΔT ₂ = ΣB _i × t ₂ + Σb _i (4)

The second term of the equation (4) represents the amount of temperature drop caused by the molten steel 5 discharged from the converter 1 being taken out by the refractory on the inner wall lined in the ladle 4. The temperature drop amount is estimated and calculated based on the temperature _TL of the inner wall refractory of the ladle 4 at the time of tapping, which is represented by the following equation.

T _L = f (T _cc , t _k , t _y , L _k ) (5)

T _cc in the equation (5) is the surface temperature of the refractory on the inner wall of the ladle 4 which has become an empty pot by pouring the molten metal into the continuous casting machine 2. This temperature is measured by the ladle thermometer 70 installed in the temperature measuring station 7 and is given to the process control unit 30.
Using the input from 70, the calculation of equation (5) is performed.

[0042] (5) t _k in the formula, the time the ladle 4 is in the empty pot state, that is, ladle 4 finishing the pouring of the continuous casting machine 2
Is the time required until the steel is returned to the front of the converter 1 along the conveying path 3 and the steel output from the converter 1 is received, and during the transfer from the continuous casting machine 2 to the converter 1. It is used to calculate the temperature drop of the refractory on the inner wall of the ladle 4 caused by heat dissipation to the atmosphere.
Further, t _y is a time required for preheating the inner wall refractory material performed by the preheating device 8 during this return, and is used for calculating the temperature rise of the inner wall refractory material of the ladle 4 caused by the preheating. The t _k and t _y are stored in the operating condition file 34 as the operating conditions for the corresponding charge.

In addition, heat loss of the refractory on the inner wall of the ladle 4 is necessary for calculating the temperature drop and the temperature rise as described above. L _k in the equation (5) is a state quantity that affects the heat loss, and includes the number of times the molten steel 5 is received, whether or not the molten steel 5 is repaired, and the like.
Includes usage history of refractories on the inner wall of. Further, before preheating by the preheating device 8, as shown by the broken line in FIG.
Measures for preventing heat radiation may be taken by covering the upper opening of the above with the upper lid 4a, and whether or not the upper lid 4a is used is also included in the above L _k . The above state quantities are stored in the operating condition file 34 as the operating conditions for the corresponding charge.

The drop correcting unit 32, when the surface temperature T _cc of the inner wall refractory of the ladle 4 measured by the ladle thermometer 70 is given to start the operation according to the flowchart shown in FIG. 3, first, the The measured value of the surface temperature T _cc is taken in (step 1), and then the expected time t _k required for the relevant ladle 4 to move to the converter 1, the expected time t _y required for preheating in the preheating device 8, and The state quantity L _k related to the usage history of the inner wall refractory is read from the operating condition file 34 (step 2), and these are applied to the equation (5), and the temperature _TL of the inner wall refractory of the ladle 4 at the time of tapping. Is calculated (step 3).

The calculation of T _L is carried out by first determining the heat loss of the inner wall refractory based on L _k , which represents the usage history of the inner wall refractory, and moving the ladle 4 under the condition of the obtained heat loss. This calculation is performed by calculating the temperature decrease amount generated in the inner wall refractory during t _{k and} the temperature increase amount generated in the inner wall refractory during the preheating time t _y in the preheating device 8 and adding or subtracting these to and from T _cc. From the result, the first correction value representing the amount of temperature drop caused by the molten steel 5 tapped from the converter 1 being removed by the refractory on the inner wall of the ladle 4 is calculated (step 4).

The above T _cc is a temperature measurement value obtained after pouring the molten metal into the continuous casting machine 2 at the temperature measurement station 7, and this measurement is made to face the inside of the ladle 4 in the empty pot state. The ladle thermometer 70 such as a radiation thermometer can be commonly used for each of the ladles 4, 4, ... On the transport path 3. Another variable is a value stored in the operating condition file 34, and is the temperature _{TL of the} refractory on the inner wall of the ladle 4 at the time of tapping.
The calculation of is immediately after the molten steel 5 conveyed in the precharge by the target ladle 4 is tapped into the continuous casting machine 2, that is, sufficiently before the tapping from the converter 1 in the charge. At the point of time. Therefore, the amount of temperature drop caused by the molten steel 5 tapped from the converter 1 being taken out by the refractory on the inner wall of the ladle 4 can be obtained with high accuracy by the estimation calculation for the corresponding ladle 4.

On the other hand, the first term of the equation (4) represents the amount of temperature drop caused by heat dissipation to the surroundings until the molten steel 5 tapped from the converter 1 is transferred into the ladle 4. And B _i
Is a state quantity related to the heat dissipation such as the initial temperature of the molten steel 5 and the temperature of the surrounding atmosphere. Further, t ₂ is the time required for tapping from the converter 1, and in the method of the present invention, this time t ₂ is estimated and calculated by the following equation.

[0048]

[Equation 1]

This equation shows that the area of the tap hole 1a opened in the converter 1 for tapping molten steel 5 increases as the number of times N of use increases due to the accumulation of melting loss due to tapping, Assuming that the tapped amount per unit time at the tapped outlet 1a increases,
It is formulated using the material balance of molten steel 5. Since each value in the formula is given as a stored value in the operating condition file 34, the tapping time t ₂ to the ladle 4 at each charge is given.
Can be predicted with high accuracy by the formula (6) before the actual tapping is started.

The descent amount correction unit 32 determines the weight W _{st of the} molten steel 5 to be tapped in the charge, the density ρ of the molten steel, and the tapping mouth.
The initial diameter D _{0 of} 1a and the number of times N of tapping tap 1a used until the charge are read from the operating condition file 34 (step 5), and these values are applied to the equation (6) to tapping time t.
₂ is calculated (step 6), and from this result, a second correction value representing the amount of temperature drop that occurs in the molten steel 5 due to heat dissipation during tapping is obtained (step 7), and this is calculated in step 4. The correction amount ΔT ₂ indicating the temperature drop of the molten steel 5 due to the tapping is calculated by adding it to the calculated first correction value (step 8).

As described above, in the method of the present invention, the temperature T _{L of the} refractory on the inner wall of the ladle 4 at the time of tapping is determined by the formula (5), and the time t ₂ required for tapping to the ladle 4 is (6 ), The correction amount ΔT ₂ indicating the temperature drop of the molten steel 5 which occurs during the tapping is accurately predicted according to the equation (4). The temperature drop amount ΔT calculated and obtained by correcting the predicted drop amount ΔT _{1 based} on this result respectively reflects the current state of the ladle 4 that actually accepts tapping and the present state of the converter 1 that performs tapping. It is a highly accurate predicted value.

Therefore, ΔT is added to the proper temperature T _a of the molten steel 5 at the time of pouring into the continuous casting machine 2 to obtain the target temperature setting unit 33.
The target temperature T output at the time of tapping is a target value that accurately predicts the temperature drop of the molten steel 5 due to tapping, and is output from the converter 1 by the operation of the blowing control unit 10 according to this target temperature T. by controlling the temperature of the molten steel 5 which is steel, so that the proper temperature T _a in the pouring time is properly implemented.

As a result of carrying out the method of the present invention as described above in the actual steelmaking process, the probability that the temperature of the molten steel 5 at the time of pouring the molten metal into the continuous casting machine 2 falls within an error range of ± 10 ° C. with respect to the proper temperature T _a . The (hit rate) is about 75% when the conventional method is used, while it is around 85% when the method of the present invention is used. It was confirmed that it would be greatly improved.

In the above embodiments, application examples in the steel making process have been described, but the method of the present invention can be applied to the same kind of process for producing other metals, and similar effects can be obtained. It goes without saying that it will be done.

[0055]

As described in detail above, in the method of the present invention, the measured value of the surface temperature of the inner wall refractory of the ladle, which is actually measured after pouring into the mold, is used to determine the use history of the inner wall refractory of the ladle,
Based on the estimated time required to move the ladle from the mold to the furnace and the estimated time of preheating performed during this time, determine the temperature drop of the molten metal caused by the removal of heat from the inner wall refractory of the ladle when tapping from the furnace. , Is calculated sufficiently before the time of tapping, and the temperature drop of the molten metal caused by heat dissipation during tapping is calculated accurately based on the planned tapping amount and the history of tap opening use, Based on these calculation results, the target temperature at the time of tapping is determined by correcting the temperature drop of the molten metal that occurs during the transfer to the mold. They can be matched with each other, the quality of the product ingot can be improved, and the productivity can be improved. Further, the required surface temperature of the refractory material on the inner wall can be measured in an empty pot state and is easy to carry out.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the overall structure of a steelmaking process in which the method of the present invention is carried out.

FIG. 2 is a block diagram showing an internal configuration of a process control unit that performs an operation according to the method of the present invention.

FIG. 3 is a flowchart showing a procedure for calculating a correction amount indicating a temperature drop of molten steel that occurs during tapping.

[Explanation of symbols]

 1 Converter 1a Steel tap 2 Continuous casting machine 3 Conveyor path 4 Ladle 5 Molten steel 6 Secondary refining section 7 Temperature measuring station 8 Preheating device 10 Blowing control section 30 Process control section 31 Temperature drop calculation section 32 Fall correction Part 33 Target temperature setting part 34 Operating condition file

Claims (1)

[Claims] 1. A molten metal produced in a furnace is tapped into a ladle via a tap hole, and the molten metal is poured into a mold after being conveyed by the ladle to obtain a desired ingot. In order to keep the temperature of the molten metal at the time of pouring at a predetermined temperature during the operation of the process in which the pan is preheated and returned to the front of the furnace to accept new tapping, In the method for managing the temperature of the molten metal, the amount of temperature drop of the molten metal that occurs is calculated by a predetermined arithmetic expression, and the result of this calculation is added to the predetermined temperature to determine the target temperature at the time of tapping. The temperature of the object is measured after completion of the pouring,
Based on this measurement result, the use history of the inner wall refractory material, and the scheduled time until the next tapping, a temperature drop amount of molten metal caused by heat removal of the inner wall refractory material during tapping A second correction value indicating the amount of temperature drop caused by heat dissipation during the tapping, based on the expected amount of molten metal tapped into the ladle and the usage history of the tapping port. Is calculated, and the temperature drop amount calculated by the arithmetic expression is corrected by the first and second correction values.