JPH08219897A - Determining method for heat storage quantity of ladle - Google Patents

Abstract

PURPOSE: To provide a determining method for heat storage quantity of a ladle which does not need connection at the time of measurement, of which measurement workability is excellent, and which has high mechanical and thermal durability, can be used safely, and carries out highly precise determination. CONSTITUTION: A determining method is to determine a ladle heat storage quantity in a ladle 14 and for which a plurality of metal rods 11, 12 having different length are buried in refractory lining 13 and one ends of the metal rods 11, 12 are so arranged as to face to the inner face of the ladle 14 and at the same time the other ends are exposed to the outer face of the ladle 14 and the temperature at the end faces of the metal rods 11, 12 exposed to the outer face of the ladle 14 is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is effective in controlling the temperature of molten steel in a ladle that holds molten iron accumulated in a carrier container or molten steel produced in a refining furnace such as a converter or an electric furnace. It relates to a method for determining the amount of heat stored in a pot.

[0002]

2. Description of the Related Art Molten steel melted in a refining furnace is held in a ladle after the refining process, and necessary processing such as secondary refining is performed. Depending on the temperature and the amount of heat storage, the temperature of the molten steel received in the ladle changes, so it may not be possible to process the molten steel at an appropriate temperature.
This is a cause of poor yield of molten steel. Conventionally, such ladle temperature and heat storage amount management has been performed empirically by controlling molten steel temperature depending on the operating conditions of the ladle such as the elapsed time from the previous steel reception of the ladle and the preheating time of the ladle. There is. However, such empirical management cannot be quantitatively controlled, and a veteran operator's judgment occupies a large weight, so that stable and accurate management of molten steel temperature is difficult. Further, in JP-A-1-246313, the temperature of the refractory in the ladle is measured by a thermocouple embedded in the refractory, and the degree of temperature decrease of the ladle refractory is estimated based on the measured data. Has proposed a method of controlling the temperature of molten steel.

[0003]

However, in the method described in Japanese Patent Laid-Open No. 1-246313,
In a ladle that is repeatedly used for receiving molten steel, treating molten steel, and discharging molten steel, it is necessary to connect a measuring device, etc. to measure the temperature of the ladle, and workability is poor, and it is difficult to operate like a thermocouple. When a thin wire with low durability is used, it is easy to be broken or damaged by a mechanical external force during use, and it is difficult to use it for general purpose under the environment of high temperature and mechanical shock. The present invention has been made in view of the above circumstances, does not require wiring at the time of measurement, has excellent workability in measurement, has high mechanical and thermal durability, and can be used safely. At the same time, it is an object of the present invention to provide a method for determining the amount of heat stored in a ladle that enables highly accurate determination.

[0004]

A method according to the above-mentioned object.
The method for determining the amount of heat accumulated in the ladle described above is a method for determining the amount of heat accumulated in the ladle in a ladle formed by burying a plurality of metal rods each having a different length in the refractory lining of the ladle. One end is arranged toward the inner surface of the ladle, the other end is exposed to the outer surface of the ladle, and the temperature of the end surface of the metal rod exposed to the outer surface of the ladle is measured. ing. According to a second aspect of the present invention, there is provided a method for determining the amount of stored heat in a ladle, which is configured to measure the end surface temperature of the metal rod by using a non-contact type thermometer.

Here, as the metal rod, it is possible to use a metal rod such as iron, steel, stainless steel, alloy iron, copper and other alloys having a higher thermal conductivity than the refractory which is the lining material of the ladle. it can. Further, the metal rod may be embedded by pouring a castable refractory or other indeterminate refractory into the pot after the metal rod is placed at a predetermined position in the ladle, or a furnace material made of a regular refractory in advance. It is also possible to place it by inserting a metal rod into it after perforating it. A plurality of metal rods having different lengths and made of the same kind of material are embedded in a plurality of places in the refractory lining. Regarding the length of the metal rod, the tip position of the metal rod embedded in the ladle lining is separated from the steel receiving surface of the refractory lining by at least about 10 cm in consideration of the melting loss of the refractory. It is desirable for safety to set up to the maximum position.
Further, exposing the other end of the metal rod to the outer surface of the ladle means a state in which the end surface of the metal rod can be seen from the outside of the furnace wall of the ladle. It means a state in which the end face of the metal rod which is accordingly projected and is exposed is covered with a refractory material such as metal or oxide. Ladle heat storage amount, the temperature distribution of the refractory in the ladle is estimated by the temperature measurement, in the spatial coordinate system shown in the temperature distribution diagram,
It can be determined by integrating the specific heat, weight and temperature of the refractory lining. The temperature of the exposed end surface of the ladle of the metal rod may be measured by a non-contact temperature sensor such as a thermo sensor or a radiation thermometer. If necessary, use a thermocouple to expose the end surface of the metal rod. Alternatively, the thermocouple may be fixedly or detachably installed to measure.

[0006]

In the method for determining the amount of heat accumulated in the ladle according to the first and second aspects, since the temperature of the end face of the metal rod exposed on the outer surface of the ladle is measured, the high temperature is maintained even under the severe environment of use of the ladle. It is possible to perform stable measurement up to the region. Therefore,
Estimating the temperature distribution in the ladle lining based on the measured temperature of the end face allows easy and safe determination of the ladle heat storage amount. Further, in the method for determining the amount of stored heat in the ladle according to claim 2, since a non-contact type thermometer is used, there is little risk of disconnection as in the case of using a thermocouple, and maintenance is further safe. And easy to do.

[0007]

Embodiments of the present invention will now be described with reference to the accompanying drawings to provide an understanding of the present invention. FIG. 1 is a schematic explanatory view of an apparatus to which a method for determining a ladle heat storage amount according to an embodiment of the present invention is applied, and FIG. 2 is a schematic view showing a time course of end face temperature of a metal rod to which the same method is applied, FIG. 3 is a schematic diagram showing the time course of the end surface temperature difference between two metal rods to which the same method is applied.

The outline of the apparatus shown in FIG. 1 will be described. In the apparatus, two metal rods 11 and 12 are made of a refractory lining 13.
It comprises a ladle 14 embedded therein and a temperature measuring device 10 comprising a radiation thermometer for measuring the temperature of the end faces of the metal rods 11 and 12 exposed on the outer surface of the ladle 14. The ladle 14 is composed of a cylindrical iron container having an outer diameter of 4 m, a height of 4.5 m, and a steel shell 15 having a thickness of 30 mm, the refractory lining 13 has a thickness of 20 cm, and the meltable steel capacity that can be processed is about 175 t. . The metal rods 11 and 12 have a diameter of 3 cm and a length of 13 cm and 8 cm, respectively, and a thermal conductivity of 28 kca.
Using stainless steel rods of 1 / m · h · ° C., one end of these stainless steel metal rods 11 and 12 is 0.4 m (a) and 0.3 m (b) high from the bottom of the ladle 14. At one position, one end was exposed toward the outer surface, and the other end was horizontally arranged on the inner surface side of the ladle 14 and embedded in the refractory lining 13. Construction of the refractory lining 13 is performed by adding 6 Wt% of water to a mixture containing 93 Wt% of alumina component, 3 Wt% of magnesia component, 2 Wt% of CaO component and a small amount of silica component.
About 22 tons of castable added was poured into the container of the pot 14, and the average thickness of the refractory lining 13 made of castable was set to 17 to 20 cm, and the thermal conductivity after drying was set to 2 kcal / m · h · ° C. .

Here, as shown in FIG. 1, lengths y ₁ , y
End surface temperature T _a of the two metal rods 11 and 12 is ₂ at positions exposed to the outer surface of the ladle 14, by measuring the T _b, the refractory lining 13 of the corresponding metal rod 11 and 12 An example of a method for determining the ladle heat storage amount for obtaining the temperatures T ₁ and T ₂ at a certain terminal position will be described below. At least two or more metal rods made of iron or the like having high heat conductivity and heat resistance in the use environment are provided in the refractory lining 13 at any position of the ladle 14 so that the heat conductivity is higher than that of the outer surface. A certain metal rod 1
Each temperature T _a of the end surface of 1,12 to measure T _b. Since this temperature reflects the end temperatures T ₁ and T ₂ of the metal rods 11 and 12 in the refractory lining 13, the ladle 14
It is possible to measure the temperature difference at each end by measuring the end surface temperature of the metal rod on the outer surface. For example, the thermal conductivities λ and λ ′ of the refractory lining 13 and the metal rods 11 and 12 are constant, respectively, and the heat transfer amount (Q) in the refractory lining 13 at the positions of the metal rods 11 and 12 and the metal rod 11 are the same. The following equations (1) and (2) are established by assuming that the heat transfer amount (Q ′) in each of Nos. 12 and 12 is constant. _{Q = Sλ (T-T 1} ) / x 1 = Sλ (T-T 2) / x 2 ··· (1) Q'= Sλ' (T 1 -T a) / y 1 = Sλ' (T 2 -T _b ) / y ₂ (2) Furthermore, it can be considered that the following approximate expression holds for each temperature T ₁ , T ₂ , T _a , and T _b . T ₁ −T ₂ = T _a −T _b (3) where Q is the amount of heat transfer in the refractory, λ is the thermal conductivity of the refractory lining 13, T is the surface temperature of the refractory lining 13, T ₁ and T ₂ are the temperatures at the end positions in the refractory lining of the metal rods 11 and 12, x ₁ and x _{2, respectively.}
Is the length from the ends of the metal rods 11 and 12 to the refractory lining surface, and S is the heat transfer area. Further, Q'is the heat transfer amount of the metal rod, y ₁ and y ₂ are the lengths of the metal rods 11 and 12, and λ'is the thermal conductivity of the metal rod. Therefore, T ₁ and T ₂ can be calculated based on the equations (1) to (3) and the like, and by assuming the temperature distribution of the refractory lining 13, the ladle container can be calculated based on the temperature distribution. Refractory,
And the ladle heat storage amount can be calculated from the specific heat data. Further, the heat storage amount of the ladle 14 and the temperature drop of the molten steel accumulated in the ladle 14 have a clear relationship with the heat transfer amount Q, and by estimating and calculating the heat transfer amount Q, Pot 1
The temperature of the molten steel held in No. 4 can be accurately controlled. Furthermore, by measuring the molten steel temperature and T _a and T _b at the timing after the secondary refining treatment, which is approximated to reach the thermal equilibrium by allowing the molten steel to stay in the ladle 14, The temperature distribution can be assumed, and the lining residual thickness can be estimated based on the temperature distribution to control the lining thickness of the ladle refractory.

First, the ladle 14 after castable construction is dried to remove water in the castable, and then the ladle 14 is removed.
Preheating was performed for about 6 hours until the surface temperature (T) of the refractory lining 13 reached an average of 800 ° C. by a preheating burner (not shown) provided on the lid. Where dry,
The average specific heat of the refractory lining 13 after preheating is 0.13c
al / g · ° C, average thermal conductivity is 2 kcal / m · h · ° C
And the end face temperatures T _a and T _b of the metal rods 11 and 12 at the heights (a) and (b) measured by the temperature measuring device 10 at this time are 440 ° C. and 260 ° C., respectively. The average temperature of the iron shell 15 was 80 ° C. Therefore, the cooling temperature 25 of the ladle 14 calculated as the product of the average refractory temperature derived from the lining thickness and the heat transfer amount in refractory lining thickness management and the specific heat of the lining refractory 25
The heat storage amount calculated by setting the heat storage amount at 0 ° C to zero is about 2.79 per refractory area, with the specific gravity of the refractory being 3.2.
It was calculated to be kcal / cm ² . Here, ladle 1 having a temperature of 1680 ° C. and a weight of 173 tons that has been refined in a converter is ladle 1.
After receiving the steel in No. 4 and treating the molten steel, the molten steel was poured into a tundish and cast. About 2.5 hours to discharge from受鋼of the molten steel, the height immediately after the molten steel discharge (a), (b) an end surface temperature T _a of the metal rod 11 and 12 in position, T _b is a 850 ° C., respectively 540 ° C., the surface temperature (T) of the refractory lining 13 became 1490 ° C., and the heat storage amount of the ladle 14 at this time was calculated to be about 4.95 kcal / cm ² based on 25 ° C.

Next, when the empty ladle 14 was left for about 5 hours, the metal rod 11 at the height (a) and (b) positions,
The end face temperatures T _a and T _b of 12 are 230 ° C. and 140, respectively.
C., and the surface temperature (T) of the refractory lining 13 was 400.degree. The heat storage amount of the ladle 14 calculated from the above is 1.62 kcal / cm ^2, which is 1.17 from the previous value.
Since kcal / cm ² low, the end face temperature T _a of the metal rod 11 and 12, as T _b is 450 ° C. and 270 ° C., respectively, the adjustment of the preheating of the ladle 14 by a burner or the like for pre-heating of the ladle 14 After maintaining the heat storage amount of the ladle 14 at the target level, the following molten steel treatment was performed. As a result of performing management to keep the heat storage amount of the ladle 14 constant as described above,
Fluctuation of molten steel temperature is suppressed, inclusion floating failure due to temperature decrease or casting trouble is reduced, product yield is improved, and refractory lining thickness control of ladle 14 becomes possible. The life of the refractory lining 13 could be improved by about 12% as compared with the case where the heat storage amount control was not performed.

FIG. 2 is a schematic diagram showing the time course of the end surface temperatures T _a and T _b of the metal rods 11 and 12 of the ladle 14 in the above-described ladle operation, and the time difference between the end surface temperatures T _a and T _b. A schematic diagram showing the progress is shown in FIG. 3. By using the end surface temperature difference as shown in FIG. 3 as a management index, the change tendency of the heat storage amount of the ladle 14 can be easily estimated and predicted. At the same time, an abnormality in the lining of the ladle 14 can be detected at an early stage to prevent casting trouble.

In the above embodiment, the case where two metal rods 11 and 12 having different lengths are embedded in the refractory lining 13 has been described in detail.
By increasing the number of metal rods embedded in 3 and taking more measurement points, it is possible to improve the measurement accuracy of the temperature distribution in the refractory lining 13. In the above examples, stainless steel having a relatively low thermal conductivity was used as the metal rod, but when using high thermal conductivity iron, copper, etc., the measurement accuracy can be further improved, and It is preferable to coat the periphery of the metal rod with a metal or alloy having high heat resistance and high heat insulation properties from the viewpoint of improving durability or measuring accuracy.

[0014]

According to the method for determining the amount of heat accumulated in the ladle according to the first and second aspects, the temperature distribution in the refractory lining is calculated by measuring the temperature of the end surface of the metal rod exposed on the outer surface of the ladle. In order to estimate and determine the heat storage amount of the ladle, the measurement can be performed reliably, and the work is simple and safe.
Further, as a result of suppressing an abnormal temperature drop in the ladle at the final stage of casting, it is possible to prevent defective floating of inclusions or casting trouble due to temperature drop, and improve product yield.
Furthermore, the device itself composed of the metal rod is robust, there are no troubles during operation and maintenance, and temperature control can always be performed in a stable state. Particularly, in the method for determining the amount of heat stored in the ladle according to claim 2,
Since it is a non-contact measurement, it is less affected by environmental conditions such as dust and heat radiation, and there is no need to wire the ladle as in the past when moving the ladle, maintenance is simple, and automation is automatic. Can be easily dealt with.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of an apparatus to which a method for determining a ladle heat storage amount according to an embodiment of the present invention is applied.

FIG. 2 is a schematic diagram showing a time course of an end surface temperature of a metal rod to which the same method is applied.

FIG. 3 is a schematic view showing a time course of an end surface temperature difference between two metal rods to which the same method is applied.

[Explanation of symbols]

 10 Temperature Measuring Instrument 11 Metal Rod 12 Metal Rod 13 Refractory Lining 14 Ladle 15 Iron Crust

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // B22D 41/02 B22D 41/02 B

Claims (2)

[Claims] 1. A method for determining the amount of heat stored in a ladle in which a plurality of metal rods having different lengths are embedded in a refractory lining of the ladle, wherein one end of the metal rod is connected to the ladle. A ladle heat storage amount characterized by arranging toward the inner surface, exposing the other end to the outer surface of the ladle, and measuring the temperature of the end surface of the metal rod exposed to the outer surface of the ladle. Judgment method. 2. The method for determining the amount of heat accumulated in a ladle according to claim 1, wherein the end surface temperature of the metal rod is measured using a non-contact type thermometer.