JP2022031063A - Continuous temperature measurement probe for converter or molten metal ladle using cermet protective tube - Google Patents

Abstract

To provide a temperature sensor having both durability to withstand an impact load of charged scrap or molten metal flow and high thermal conductivity to the molten metal as a means for continuous temperature measurement of molten metal in a container such as a converter or a ladle.SOLUTION: By incorporating a cermet protective tube having high thermal conductivity and high temperature durability inside the refractory sleeve, the cermet protective tube acts as an aggregate and exhibits high strength, and at the same time, by improving temperature measurement accuracy by the high thermal conductivity of the cermet protective tube, the continuous temperature measurement of molten metal in the ladle is made possible.SELECTED DRAWING: Figure 1

Description

The present invention relates to a temperature sensor for continuously measuring the temperature of molten metal such as hot metal in a converter and molten steel in a ladle in the field of metal casting.

Refining in a converter in steelmaking is carried out for the purpose of decarburizing carbon contained in hot metal, heating to the target steel output temperature, separating impurities such as silicon, phosphorus and manganese as slag and removing them. ing.
In this step, the hot metal is refined into molten steel, hot water is discharged into a molten steel ladle, and then secondary refining such as LF, RH, CAS, and REDA is performed, and finally casting is performed.

In the refining in the converter, oxygen is blown based on the blowing model consisting of the raw material composition, temperature, secondary combustion ratio of exhaust gas, etc., and the oxygen blowing amount is measured from the measurement results of the carbon content and temperature by the sublance. A dynamic control method is widely used in which the amount of oxygen is adjusted, the estimated value until the carbon content reaches the target value is calculated, and the blowing is automatically terminated.
Therefore, it is clear that measuring the temperature of hot metal and molten steel in the converter is an indispensable work in refining in the converter.

The molten steel discharged from the ladle is heated, slag-zipped, and desulfurized by LF treatment, and degassed and component adjusted by treatment such as RH, CAS, and REDA.
In each treatment, batch temperature measurement of the molten metal is carried out using a consumable thermocouple probe before the treatment, and batch temperature measurement is performed multiple times as needed during the treatment, and the required treatment time is required. , The amount of heat rise, the implementation of alloy addition, etc. have been decided.

As described above, temperature measurement of molten metal is indispensable in the secondary refining process in the converter and ladle, but in both the converter and ladle refining processes, the process is completed before, during, and after the process. Batch temperature measurement using a consumable thermocouple is performed at the timing before and after the end. From the temperature measurement value, the subsequent processing is determined by a method based on the conventional results, but the treatment is performed by estimating the temperature at the time of processing from the temperature at the time when the temperature is measured. In addition to the estimated value, control is also performed by judgment based on the operator's experience.
However, this estimated value does not always match because it constantly changes depending on the degree of wear of the converter and the ladle and the material of the molten metal to be refined.

When proceeding with the process based on batch temperature measurement, it is controlled by estimated value and experience, but if the temperature of the molten metal during the process is always continuously measured and reflected in the system and operator in real time, it will be at the time of the process. Since it reflects the state of the converter and the pan, and the temperature of the molten metal itself in the pan, more accurate and efficient processing can be realized, but this technology has not been established even now. ..

For continuous temperature measurement of molten metal, the temperature of molten metal is measured by embedding a temperature sensor such as sheath thermocouple in the refractory such as porous slag of the ladle in the past and measuring the temperature inside the furnace wall material. Although it has been verified whether it can be estimated, metal and slag adhere to or wear on the surface of the surrounding refractory due to the progress of operation and the accumulation of the number of times the converter and ladle have been used. As a result, the distance to the measurement target and the heat transfer characteristics constantly change, making correction difficult.

JP 2009-41069

The temperature measurement accuracy can be improved by directly contacting the molten metal with the temperature sensor ensuring an appropriate outer diameter and length, but the sheath thermocouple can be easily contacted with the molten metal. fall into disrepair. In order to prevent this, if the contact portion with the molten metal is covered with a protective tube made of a refractory material, early damage due to temperature can be prevented to some extent.
On the other hand, regarding mechanical damage, refractories have low high-temperature strength and have a shape in which a predetermined length protrudes from the inner wall of the converter or ladle. It cannot withstand the impact load of the molten metal flow received during receiving and steel receiving, and there is a concern that it will be crushed.

Although the mechanical strength increases by increasing the wall thickness of the refractory part, the slag adhesion area increases due to the increase in size of the temperature sensor due to the increase in wall thickness. In addition, due to the thickening of the wall, the influence of the low thermal conductivity of the fire-resistant material becomes high, so that the heat of the molten metal is removed from the surrounding fire-resistant material before it reaches the temperature measurement point of the sensor. This makes it difficult to capture the temperature of the molten metal. In particular, alumina-magnesia refractories, which are generally considered to have high durability in molten steel ladle, have a high degree of influence because of their low thermal conductivity.

The present invention has been made in view of the above circumstances, and it is possible to measure the true molten metal temperature instead of the correction value in the state of being in direct contact with the molten metal, and at the same time, scrap, receiving metal, and receiving steel. It has been difficult to provide a temperature sensor that is strong enough to withstand the impact load of the molten metal flow that is sometimes received.

In order to solve the above problems, the continuous temperature measuring probe according to the present invention uses a cermet protective tube having toughness, thermal shock resistance, high temperature strength, and high thermal conductivity inside, so that the cermet protective tube surrounds the periphery. By acting as an aggregate for the refractory sleeve that covers it, it has the strength to withstand impacts that cannot be withstood by a refractory-only protective tube. To provide a continuous temperature measuring means having good temperature measuring accuracy.

According to the present invention, the continuous temperature measuring probe can be made stronger than the probe using the refractory-only protective tube, and is exposed inside the converter or the ladle in a state of being in direct contact with the molten metal. Even if it is not damaged, it is possible to continuously measure the temperature while maintaining good temperature measurement accuracy.

In the present invention, it is a figure which shows the structure of the continuous temperature measuring probe which can be exchanged even in the hot state where the refractory heat is stored, such as after the ladle is preheated and the pouring is completed. Durability is increased by increasing the wall thickness of the refractory compared to the continuous temperature measuring probe shown in Fig. 1, and intermediate repair is performed by replacing bricks in a cold state and thickening the worn part due to the amorphous refractory. It is a figure which shows the structure of what was supposed to be exchanged at times. It is a figure which shows the state which the continuous temperature measuring probe as shown in FIG. 1 or FIG. 2 is attached to the ladle of molten metal. It is a figure which shows the result of having measured the molten metal temperature in a ladle obtained by the Example of this invention.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is an example of a continuous temperature measuring probe for a converter or a molten metal ladle using a cermet protective tube according to the present invention. It should be noted that the examples are merely for the purpose of facilitating the understanding of the invention, and are not limited to the conditions of the examples. As shown in FIG. 1, the continuous temperature measuring probe is connected to a protective sleeve 2 made of a refractory, a cermet protective tube 1 fixed inside the refractory and having a thermocouple incorporated therein, and a cermet protective tube 1. It is composed of a metal pipe 9 having a structure for protecting a thermocouple, ensuring the required total length, and connecting to an external connector. The continuous temperature measuring probe is inserted into the mass brick 4, which is a functional brick having a tapered hole inside, and the insertion length is adjusted by the holding brick 10 and the adjusting iron plate 11 from the lower part, and then by the fastening jig 12. Fix it by pressing it toward the inside of the pan.

The cermet protective tube is preferably formed by a cold isotropic pressure method and sintered in a sintering furnace to have a high sintering density in order to secure thermal conductivity and hot strength at high temperatures. If it is assumed that the protective sleeve will be worn out due to melting or erosion and the continuous temperature measuring probe will be replaced before the cermet protective tube is exposed inside the pan, the cermet molded and sintered by extrusion molding. A protective tube may be adopted.

Brick 3, brick 5, brick 6, and brick 7 differ depending on the type of molten metal to be carried by pouring hot water into the ladle, but in particular, the brick 3, the protective sleeve 2, and the mass brick 4 come into contact with the molten metal. Since the temperature rises, it is preferable to use a material having a similar linear expansion rate and thermal conductivity. In the example, since the brick 3 was an alumina-magnesia castable, the protective sleeve 2 also adopted a precast sleeve formed by pouring a similar castable. The materials include those made of black refractory materials such as alumina-carbon, spinel-carbon, magnesia-carbon, zirconia-carbon, and silicon carbide-carbon, and alumina and alumina, depending on the usage environment of the continuous temperature measuring probe. -A protective sleeve made of silica, alumina-spinel, alumina-magnesia, magnesia, or the like, but using either or both of them may be adopted.

Since the metal pipe 9 is easy to remove, a one-touch type connector component is fixed to the tip by welding.

Utility model

Utility model registration No. 3211664 For this connector, instead of the one-touch type connector parts, a stainless steel hose is connected, a thermocouple wire is passed through the inside, and a metal connector or a ceramic connector is attached to the tip. good.

As shown in FIG. 3, the continuous temperature measuring probe 15 is fixed to the mass brick 4 fixed to the floor of the ladle 14, the metal pipe 9 is exposed to the outside of the pan, and the thermocouple extension cable 16 is connected to the tip thereof. did. This cable is connected to the heat insulating box 17 attached to the outside of the ladle, the electromotive force is read into the wireless transmitter 18 set inside the heat insulating box 17, and the temperature data is transmitted.

An example in which the temperature of the molten metal is continuously measured on a trial basis with such a configuration will be described below.
When the continuous temperature measuring probe having the structure shown in the example was attached to the ladle in operation and the temperature was measured, the temperature measurement data as shown in the graph of FIG. 4 was obtained. The temperature measurement point is 90 mm from the bottom of the pan. As shown in this figure
The continuous temperature measuring probe detects the temperature inside the ladle from the time of preheating, and compares it with the temperature measurement value of the batch temperature measurement by the consumable thermocouple probe performed during the LF treatment and RH treatment of the secondary refining. However, it can be seen that they capture almost the same temperature.

In the embodiment, the continuous temperature measuring probe having a structure capable of hot exchange in FIG. 1 is used, but in order to reduce the frequency of exchanging the continuous temperature measuring probe and the risk of steel leakage, it is cooled. A continuous temperature measuring probe with a structure as shown in Fig. 2 is placed in the pan on the premise that the bricks will be replaced in the interim state, the damaged part will be thickened by the amorphous refractory, and it will be used until the intermediate repair. It may be incorporated. With this shape, the diameter of the hole to be drilled can be made smaller than when the holding brick 10, the adjusting iron plate 11, and the fastening jig 12 as shown in FIG. 1 are used, and it takes time and effort to attach the continuous temperature measuring probe. Can also be reduced.

As described above, according to the present invention, there is a continuous temperature measuring probe that has the strength to withstand the impact load of the molten metal flow received during steel receiving even if it is exposed inside the ladle, and also has good temperature measurement accuracy. Is now possible.

1 Cermet protective tube 2 Protective sleeve 3 Brick 4 Mass brick 5 Brick 6 Brick 7 Brick 8 Iron skin 9 Metal pipe 10 Pressing brick 11 Adjusting iron plate 12 Fastening jig 13 Protective sleeve 14 Ladle 15 Continuous temperature measuring probe 16 Thermocouple extension Cable 17 Insulation box 18 Wireless transmitter

Claims (4)

In a continuous temperature measuring probe that is fixed to a converter or a ladle that transports molten metal such as hot metal, molten steel, and molten metal and can continuously measure the temperature of the molten metal, a protective sleeve made of refractory material and a thermoelectric inside it. A continuous temperature measuring probe consisting of a cermet protective tube incorporating a pair and a metal pipe extending a predetermined length from the cermet protective tube. Alumina-carbon, spinel-carbon, magnesia-carbon, zirconia-carbon, silicon carbide-carbon, and other black refractories.
The continuous temperature measuring probe according to claim 1, further comprising a protective sleeve using any or both of white goods such as alumina, alumina-silica, alumina-spinel, alumina-magnesia, and magnesia. By covering the circumference of the cermet protective tube with the protective sleeve according to claim 2, the cermet protective tube has a function as an aggregate of the protective sleeve, and the high thermal conductivity of the cermet protective tube is used for measurement. The continuous temperature measuring probe according to claim 1, which has improved temperature accuracy. In order to enable hot replacement, a structure in which a mass brick, which is a functional brick, is fixed to a ladle, a protective sleeve is inserted into the tapered hole, and a holding brick, an adjusting iron plate, and a fastening jig are used to fix it. The continuous temperature measuring probe according to claim 1, wherein the shape of the protective sleeve is a combination of a truncated cone and a prism so that it can be used up to the middle of the ladle.

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