JPS62168644A - Method and apparatus for continuous casting - Google Patents

Abstract

PURPOSE:To surely connect a molten metal to a dummy bar and to prevent the breakage thereof by inserting the dummy bar into a tundish nozzle and supplying electric power between the molten metal in the tundish and the dummy bar to melt the front end of the dummy bar. CONSTITUTION:The dummy bar 66 and a connecting member 68 are inserted into the tundish nozzle 37 and a metallic material to be melted is thrown into the tundish 31. A coil for induction heating is energized by the electric power. A power source device is thereafter driven to impress a voltage between the dummy bar 66, a mold 38 and electrodes. The current flowing between the auxiliary electrode, the mold 38 and the electrodes flows through the member 68 and the dummy bar 66 and, the member 68 heats up. The molten steel in the tundish 31 melts when the heating-up and melting of the member 69 progress. The molten steel in the tundish 37 flows into the mold 38 through the nozzle 37 and a break ring 47 when the dummy bar 66 is intermittently pulled. The molten steel is cooled and molded by the mold 38 by which the desired ingot is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a continuous casting method and apparatus for continuously casting slabs, for example.

BACKGROUND ART FIG. 8 is a simplified sectional view of a continuous Ia feeding device 1 of the prior art. The continuous casting apparatus 1 includes a tundish 2 that heats and stores molten steel, and a water-cooled mold 3 fixed to the tundish 2.

A fireproof wall 4 is stretched over the inner wall surface of the tundish 2, and an induction heating coil 5 is provided. Molten steel 8 is injected and stored in the storage section 7 surrounded by the fireproof wall 4 of the tanditshu 2.
It is heated by the induced current generated by the induction heating coil 5 and maintained at a constant temperature.

A tundish nozzle 10 is provided near the bottom of the tundish 2 facing the mold 3, and is closely attached to the mold 3 via a break ring 11 made of a refractory material. The mold 3 includes an outer cylinder 14 that is coaxial with a mold cylinder 12 that is an inner cylinder and forms a cooling water passage 13 between the mold cylinders 12 . The outer cylinder 14 is provided with a water inlet 16 for injecting cooling water, and an outlet 17 for discharging the cooling water that has circulated through the passage 13 and has been heated. A partition member 18 is provided in the passage 13. The partition member 18 is the mold tube 12
It includes one right cylindrical part coaxial with the right cylindrical part, and a support part 20 provided along the circumferential direction on the outer periphery of one right cylindrical part over the entire circumference.

The molten steel 8 in the tandish nozzle 2 is transferred to the tundish nozzle 1
0 and the break ring 11, it flows into the mold 3, is cooled and molded, solidification cells grow radially inward from the outer periphery, and is taken out as a slab. The slab is placed on support rollers 21. Pinch rollers 22a supported by a, 21b, . . . , 21n and provided with the slab sandwiched therebetween.
+22t)+...+22m+7) Due to the rotational drive, it is pulled out intermittently, with one cycle consisting of pulling out in the direction of arrow A1, stopping 1 unit, moving backward in the direction of arrow A2, and stopping.

In the continuous casting apparatus 1 for manufacturing slabs in this manner, the molten steel 8 is generally melted in a melting furnace (not shown) and stored once in a ladle (not shown) or directly transferred from the melting furnace to the tundish 2. Supplied. Tanditshu 2
The molten steel 8 supplied into the mold 3 flows into the mold 3 through the tundish nozzle 10 and the break ring 11, and then flows into the connecting portion 24 formed at the tip of the dummy bar 23 inserted into the mold 3 on the tundish 2 side. stick.

Thereafter, the dummy bar 23 is intermittently drawn out as described above, and the molten steel 8 is cooled and formed to obtain a slab.

Problems to be Solved by the Invention In such a conventional continuous casting apparatus 1, the molten steel 8 injected into the tundish 2 flows into the mold 3 via the tundish nozzle 10 and the break ring 11. Like molten gA8 is Tanditshu 2
When injected into the atmosphere, the temperature drops as it comes into contact with the atmosphere. Further, the passage holes for the molten steel 8 in the tundish nozzle 10 and the break ring 11 have a small cross-sectional area perpendicular to the axis of the tundish nozzle 10, making them extremely easy to cool. Therefore, as described above, when starting the pulling operation, solidification starts in the tundish nozzle 10, and the tundish nozzle 10
Also, there was a problem that the inside of the break ring 11 etc. was blocked.

In order to prevent such a blockage from occurring, conventionally the temperature of the molten fa 8 was maintained relatively high to prevent it from solidifying near the tundish nozzle 10 and the break ring 11. For this reason, the life of the fireproof wall 4 of ■Tandish 2 will be shortened. ■In order to maintain the temperature of the molten steel 8 relatively high as mentioned above, the amount of gas contained in the molten steel 8 increases, and this gas remains in the obtained slab, resulting in a decrease in the quality of the product. I end up. (2) Since the set temperature is relatively high, new problems have arisen, such as the melting time of the molten steel 8 becoming longer.

In order to solve such problems, the tundish nozzle 10 is closed and the molten steel 8 injected into the tundish 2 is removed.
A stopper 25 that prevents water from flowing into the tundish nozzle 11 may be inserted into the tundish 2, or a so-called sliding date 26 may be provided between the tundish nozzle 10 and the break ring 11 as shown in FIG. A conceivable configuration is to prevent the molten steel 8 from flowing into the mold 3 via the break ring 11.

Although it is conceivable to produce slabs by keeping the molten steel injected into the tundish 2 at a relatively low temperature with such a configuration, the overall configuration of the continuous casting apparatus 1 becomes complicated and costs increase. In addition, in such a configuration, the tundish nozzle 10 or the break ring 11 cannot be preheated for 4 minutes, and when the molten steel 8 attempts to flow into the mold 3, it is unnecessarily cooled and the J-
As mentioned above, there is a problem in that blockage occurs.

The object of the present invention is to - solve the above-mentioned problems, prevent the molten metal from being cooled unnecessarily and cause undesirable pseudo-solid blockage, and set the temperature at which the molten metal is injected and stored in the tundish. It is an object of the present invention to provide a continuous casting method and apparatus capable of making the refractory of a tundish relatively low, extending the life of the refractory of a tundish, and significantly improving the quality of the cast product.

Means for Solving the Problems The present invention involves inserting a dummy bar into a tundish nozzle provided in a tundish where molten metal is stored, supplying electric power between the molten metal in the tundish and the dummy bar, This is a continuous casting method characterized by melting the tip of the dummy bar and pulling out the slab connected to the dummy bar intermittently or continuously.

Further, the present invention melts and refines the metal in the tundish by induction heating, inserts a dummy bar into the tundish nozzle provided in the tundish, and supplies electric power between the molten metal in the tundish and the dummy bar. This is a continuous casting method characterized by melting the tip of the dummy bar and pulling out the slab connected to the dummy bar intermittently or continuously.

Furthermore, the present invention provides a tundish for storing molten metal, a tundish nozzle provided in the tundish, a mold for cooling and molding the molten metal taken out from the tundish nozzle, and a dummy bar inserted into the dandy tush nozzles. , the tip of the gummy bar on the tundish side is made of a material with a high melting point and high electrical resistance, and the remaining part of the dummy bar is made of a material with low electrical resistance. .

Function The continuous casting apparatus according to the present invention basically includes a tundish, a mold, and a dummy bar. The tip of the dummy bar on the tundish side is made of a material with a high melting point and high electrical resistance, and the remaining portion of the dummy bar is made of a material with low electrical resistance. To carry out continuous casting according to the present invention, a dummy bar is inserted into the tundish nozzle. The metal in the tundish may be melted and refined by conductive heating, or the molten metal may be injected and stored and maintained at a constant temperature by conductive heating. Electric power is supplied between the molten metal in the tundish nozzle and the dummy bar to melt the tip of the dummy bar and connect it to the molten metal, and the gummy bar whose tip is connected to the molten metal in this way is Pull it out intermittently (or continuously).

The supply of electric power heats the tundish nozzle through which the dummy bar is inserted and its surrounding area, thereby preventing the molten metal that has come into contact with the tundish nozzle and its surrounding area from being unnecessarily cooled and solidified. I can do it.

Therefore, the molten metal is reliably connected to the dummy bar and is not solidified unnecessarily as described above, so that the molten metal and the dummy bar can be prevented from being cut off by the pulling operation. Further, since the molten metal is heated near the tundish nozzle by the power supply, the temperature of the molten metal stored in the tundish is set to be relatively low. Therefore, the head of Tanditshu is able to improve the quality of the products that are bid and cast.

Embodiment FIG. 1 is a simplified sectional view of a continuous casting apparatus 30 according to an embodiment of the present invention. With reference to FIG. 1, continuous casting apparatus 3
The basic configuration of 0 will be explained.

Inside the tundish 31 of the continuous casting device 30,
A fireproof wall 32 is formed of a fireproof material such as alumina or magnesia. This fireproof wall 32 also has electrical insulation properties. Molten steel 34, which is molten metal, is stored in a storage section 33 within the tundish 31, which is surrounded by the fireproof wall 32.

The molten steel 34 is heated by induction by an induction heating coil 35 provided in the tundish 31, and its molten state and temperature are maintained. A tundish nozzle 37 for taking out molten steel 34 is provided near the bottom 36 of the tundish 31. A mold 38 is also provided to be fixed to the tundish 31.

The mold 38 is a roughly right cylindrical inner cylinder, and includes three mold cylinders made of metal copper and a mold ff: J3.
The outer cylinder 41 is coaxial with the mold cylinder 9 and forms a passage 40 between the mold cylinder 39 and through which a cooling fluid such as cooling water flows. The electrode 52 is realized using a wide variety of good electrical conductors such as water-cooled metallic copper, the same material as the molten steel 34, or graphite.

The molded cylinder 39 and the outer cylinder 41 are constructed in a confidential manner, and the outer cylinder 4
1 is provided with a cooling water inlet 42 and a drain port 43.

Furthermore, a partition shrine 44 is provided within the passage 40 described above.

The partition member 44 has a right cylindrical part 45 coaxial with the mold cylinder 39.
and a support member 46 provided along the circumferential direction of the right cylindrical portion 45. The cooling water injected from the water inlet 42 is guided by the partition member 44, circulates through the passage 45 in the mold 38, and is discharged from the drain port 43. The end of the mold 38 having such a configuration on the tundish 31 side and the aforementioned tundish nozzle 37 are fixed to each other via a break ring 47. The tundish nozzle 37 and the break ring 47 each have holes 37a and 47b through which the molten steel 34 flows.

The molten steel 34 in the tundish 31 is cooled while passing through the mold 38, and pinch rollers 48a, 4 provided on the opposite side of the tundish 31 with respect to the mold 38
The slab 49 is held between the rollers 8b, . Also, between the mold 38 and the pinch roller 48, there is a slab 4
9 supporting rollers 50a, 501], ..., 50
n (collectively referred to by the reference numeral 50 when necessary) are provided. Here, the shaded area in the slab 49 near the mold 38 is a solidified shell 51 in which the molten steel 34 is cooled and solidified by the mold 38. Here slab 49
Between the billet size D1 and the inner size D2 of the tundish nozzle 37 and the break ring 47,
D 1 and D2 are determined so that the following formula holds true.

Di>D2 (1) An electrode 52 made of, for example, the same material as the molten steel 34 is provided on the upper part of the tundish 31.

Further, although the mold tube 39 is made of metallic copper, other materials having high thermal conductivity such as various copper alloys or graphite may be used. A rack 54 is formed on the support member 53 fixed to the electrode 52, and this rack 54 meshes with a pinion 56 which is rotationally driven by a driving means 55. The surface of the molten steel 34 in the tongue tissue 31 is lowered as continuous casting progresses, so the structure consisting of the rack 54 and the pinion 56 displaces the electrode 52 in the direction of displacement of the molten metal surface, so that the electrode 52 is constantly The tip is kept immersed in the molten steel 34 at a constant depth.

An auxiliary electrode is provided on the downstream side of the mold 38 in the direction in which the slab 49 is pulled out (in the direction of arrow C1 in FIG. 1), and includes a spring member 57 and a power supply roller 58 that is elastically pressed against the slab 49 by the spring member 57. 59 is provided. The mold 38 and the auxiliary electrode 59 have the same polarity as the polarity of the electrode 52. A power supply device 6o is provided between these electrodes 52, the mold 38, and the auxiliary electrode 59.

This power supply device 60 is controlled by a control device 62 that receives a signal derived from a temperature detection means 61 that detects the temperature of the slab 49 near the mold 38 and derives a control signal. Here, the output of the power supply device Go may be a direct current current with the electrode 52 side as a positive electrode and the mold 38 and auxiliary electrode 59 sides as a negative electrode.

The Maroku-tandish 31 is equipped with a t.m temperature sensor that detects the temperature of the molten steel 34 that is being heated and melted.
is placed. A signal corresponding to temperature detection T', stage 63 or detection I7 temperature is led to a control device 671, and control device 64 controls the output of device 65 to supply electric current to coil 3I]. . The t-
For example, a radiation thermometer is preferably used in Toebo thermocouple or temperature detector l:, '2614, by realizing the power supply device 60 as a device that generates alternating current.
Melting of electrode 52 or electrode 52 of iron molecules in molten steel 34
and ; Precipitation of U solid cells 51.＼ is also prevented 9,
That is, such melting and gas precipitation may cause wear of the electrode 52, deterioration of the compositional quality of the slab 49, and segregation of the molten steel 34 during solidification.

FIG. 2 is an enlarged sectional view of the vicinity of the break ring 4 fin τ1 in the continuous casting apparatus 30 of FIG. 1 at a stage before the molten steel 34 (see FIG. 1) is injected into the tundish 31. The configuration around the break ring 47 will be described in more detail with reference to FIG. 1 and FIG. riS2.

This was explained with reference to FIG. L sea urchin tanditshu 31
The molten steel 34 in the mold 3 is solidified by cooling and is manufactured as a slab 49.
4, after a metal such as iron is melted and refined in a melting furnace, it is once stored in a ladle and then poured into the tundish 31, or the metal is directly put into the tundish 31 and melted and refined.

Prior to the injection of the molten steel (4), a dummy bar 66 made of a low electrical resistance material such as a metal alloy or a II4 alloy is inserted into the mold 38. The dummy bar 66 may have, for example, an axis-perpendicular cross section corresponding to the inner circumferential surface of the three (1ζ).

A threaded hole 67 with an internal thread having an internal diameter D3 is provided at the tip of the dummy DE-66 on the tundish 31 side. This screw hole 67 is made of, for example, nickel-chromium steel or Kanthal alloy (copper-aluminum-iron alloy).
A threaded portion 69 with an external thread of a connecting member 6;) made of a 4.41° 4.

The connecting member 68 is coaxial with the threaded portion G9 and has the inner diameter D.
The connecting member main body 70 is provided with an external thread having an outer diameter D4 which is larger than the inner diameter D2 of the tundish 7 nozzle 37 and smaller than the inner diameter D2 of the tundish 7 nozzle 37. The end of the connecting member main body 70 opposite to the threaded portion 69 is formed into a T-shaped conical shape. At this time, when the threaded part G9 is screwed into the threaded hole 67, the stepped part 71 between the threaded part 69 and the main body 70 comes into contact with the end of the dummy bar 66 on the tundish 31 side, and the dummy bar 66
and the connection member 68 are fixed to each other by 6 degrees. When the end of the gummy bar 66 on the tundish 31 side and the plate ring 47 are opened, the melt X 34 in the tundish 31 is opened.
A sealing member 72 is provided to prevent the liquid from flowing into the mold 38 from the gap between the tongue tissue/spool 37 and the connection 8IS material main body MAO. This sealing member 72 is made of, for example, an asbestos material.
, and the quality of the connecting member main body 70 of the connecting member 68 is as follows:
A dummy with a connecting member 68 fixed thereto as shown in FIG.
The bar 66 is connected to the break ring 4 through the seal member 72 17.
7, the connection member main body 70 is selected so that it protrudes from the hole 37a of the tundish 7 slot 37 into the inner nozzle of the tundish 31.

Figure fIS3 is a graph illustrating the intermittent pulling operation of the slab 49 described in reference to Figure 1. Figure 1--
See Figure 31. Now, the l-penalty omission drawing operation will be explained. @Time L1 in Figure 3. = At t2, the pinch roller 48 shown in the first figure is rotated in the direction of arrow C3 so that the slab 4.9 advances in the direction of arrow C1. The area of the region S1 obtained by 1-1 is the amount of rotation in the direction of arrow C3. Next, from time 12 to L3, the pinch roller 48 stops, and from time ill t 3 to +4, the pinch roller 48 is rotated in the direction of arrow C4 so that the pieces 49 move backward in the direction of arrow C2. Here, the area of the region S2 indicated by diagonal lines A and J in FIG. 3 is the amount of rotation in the direction of arrow C2.

Next, at time 14 to t5 in Figure i2, the pinch roller 48
stops. In this way, the pinch roller 48 is
The operation from time t1 to time t5 is repeated as one cycle, and the slab 49 is intermittently pulled out by repeating a cycle of advancing, stopping, retreating, and stopping.

When performing the intermittent drawing operation of the slab as explained with reference to FIG. This will hinder the pulling out operation.

Therefore, in starting such a pulling operation, the tundish nozzle 37 and the break ring 47 are preheated by heating the connecting member 68 shown in FIG. 2, and the connecting member main body 70 is melted in the following manner.

FIG. 4 is a graph explaining the current conduction mode between the auxiliary electrode 59, the mold 38, and the electrode 52 shown in FIG.
The figure is a graph showing changes in resistivity of molten steel 34 with temperature.

With reference to FIG. 1, FIG. 2, FIG. 4, and FIG. 5, the energization mode of the continuous casting apparatus 30 of this embodiment will be described.

As shown in FIG. 2, a dummy bar 66 and a connecting member 68 are inserted into the tundish nozzle 37. The dummy bar 66 is held and fixed by the pinch roller 48. A metal material to be melted, such as steel, is placed in the tundish 31, and the induction heating coil 35 is energized. Metal materials are melted by induction heating and refined by injecting inert gas, etc.

Thereafter, the power supply device 60 is driven to apply a voltage (indicated by line no. 1 in FIG. 4) between the dummy bar 66, the mold 38, and the electrode 52 from time t1 in FIG. 4, and the voltage is set to the first constant voltage V1. do. As mentioned above, dummy bar 6
6 is made of a material with low electrical resistance, and the connecting member 68 is made of a material with a smaller cross section and higher melting point than the dummy bar 66 and with high electrical resistance. In addition, the auxiliary electrode 59 and the mold 3
8 and the electrode 52.
Since the refractory wall 32 and tundish nozzle 37 of 1 are made of electrically insulating material, the connection 19 flows through the member 68 and the dummy bar 66.

Therefore, the temperature of the connecting member 68 increases quickly.

That is, the voltage that has increased from time 1 to t2 in FIG. 4 is maintained at the first constant voltage 1 from time 2 to t3. While the voltage V1 is applied, the temperature of the connecting member 68 rises and heats the tundish nozzle 37 and the break ring 47, so to speak, preheating them prior to the casting operation to be described later. Here, since the voltage between the electrode 52 and the mold 38 is rising from time 1 to t2, the load current IL (
The line in Figure 4! 2) also increases. At this time, it is known that the resistivity of a metal such as the connecting member 68 changes linearly with respect to temperature. That is, the connection member 68
is heated by resistance heat, so the temperature rises and the load resistance also rises from time t1 to t3. Therefore, the load current decreases as shown by line 2.

Between times t1 and t3, the tundish nozzle 37 and the break ring 47 are preheated to an appropriate temperature as described above, and after time L3, the load voltage is increased and set to the constant voltage 2 of tjS2. While the load voltage is a constant voltage V2, the connection member 68 continues to melt due to this load current. Connection member 6
8 is further heated by the load current IL and melting progresses, the line g2 after time t3 in FIG.
．． , +p3, the load resistance increases depending on the temperature, whereas the load current decreases. As the temperature rise and melting of the connecting member 68 progresses, the load resistance rapidly increases at time L4 after the time L3, and therefore the load current IL rapidly decreases. After this time t4, the dissolution of the connecting member 68 starts and progresses.

The time t4 at which the connecting member 68 starts to melt is detected as a temperature change near the connecting member 68 by a temperature sensor t! realized by, for example, a thermocouple. Detected by i73. This detection operation may be realized by providing an ammeter or the like in the power supply device 60 and detecting a sudden decrease in the load current after time t4.

At time L5 when the connection member 68 has been melted to a predetermined extent, the load voltage is decreased and a third constant voltage of 3t is set. Since the load voltage is decreased from time 15 onward, the load current decreases.

After time t6 when the load voltage becomes a constant voltage 3, the voltage applied between the auxiliary electrode 59, the mold 38 and the electrode 52 is the same as that of the molten steel 3 in the holes 37a and 471 in FIG.
4 is selected as a voltage value that maintains a constant temperature. Therefore, the load resistance is also constant and the load current is also constant.

After time 14 as described in 11, the connecting member 6
8 starts dissolving, inside the tanditush 31'
f, m, 34 hmmL, ! ¥S21F7Lin 3
7a, 471+ is filled with molten steel. However, the area near the stepped portion 71a with the dummy bar 66 is not melted and remains as it is because it is cooled by the mold tube 39+. Next, after the time +5, the dummy bar 66 is intermittently pulled out as described with reference to FIG. dummy bar 6
As the molten steel 34 in the tundish 31 is pulled out in the direction of the arrow C1 in FIG.
7 and break ring 47 into mold 38 . On the other hand, as described above, the area around the tundish nozzle 37 and the break ring 47 is heated by the application of load current to prevent the molten steel 34 from being unnecessarily cooled and solidified and causing blockage, so that such a drawing operation is performed smoothly. can be carried out.

Here, the amount of current required to melt the connection member 68 as described above will be explained.

(1) Amount of heat required to melt the connecting member 68 Q 1 [kc
Consider all. The connecting member 68 is long! , the description will be made assuming a cylindrical shape with an axis-perpendicular cross-sectional area S. At this time, the following formula holds true regarding the amount of heat Q1.

Ql-γ5) CpΔTtenγSlK ... (2) γ[
kg/m's: specific weight Cp [kcal/kB°C]; specific heat ΔT of the connecting member 68
r'C]: Temperature difference "melting temperature - initial temperature" K [kca
l/kg]; Latent heat of melting (2) Calorific value when the connecting member 68 is energized Q 2 [
Let's consider kcall. The electrical resistance 1 value R(T) [Ω] of the connecting member 68 generally depends on the temperature,
R(T)=ρ(T)a/S...(
3) ρ(T); expressed as resistivity [Ωm]. Therefore, if the load voltage is constant,
The load current I(T) is I(T)=V/R(T)...(
4), and the minute time d in the energization period t[5ecl
The calorific value dQ2 at 1.1 is dQ2= (I(T)2R(T)/(4,2X 1.
0')ldt (5), and when this is integrated with respect to the energization period t, the following is obtained. Therefore, in the i2 formula and the sixth formula, C3<02...(7
), the connecting member 68 will be melted.

That is, the power supply device 60 shown in FIG.
Apply a voltage that dissolves the

As described above, in this embodiment, the power supply 60 causes a current to flow between the auxiliary electrode 59, the mold 38, and the electrode 52 to raise the temperature of the connecting member 68 and heat the tundish nozzle 37 and the break ring 47. At the same time, before starting to pull out the dummy bar 66, the connecting member 68
The molten steel 34 in the tundish 31 and this connecting member 68 were connected by melting. Therefore, even if the pulling operation of the dummy bar 66 is started, the molten steel 34 will not be unnecessarily cooled and solidified near the tundish nozzle 37 and the break ring 47, and such a pulling operation can be performed smoothly. .

In addition, by raising the temperature of the connecting member 68, undesired cooling and solidification of the molten steel 34 is prevented, so there is no need to set the temperature of the molten steel 34 in the tundish 31 unnecessarily high as explained in the prior art. temperature can be set relatively low.

Therefore, the life of the fireproof wall 31 can be lengthened, the amount of gas in the molten steel 34 can be reduced, and the quality of the cast product can be improved.

Furthermore, the connection member main body 70
Since the molten steel 34 is inserted sufficiently inside the tundish 31, when the molten steel 34 is injected into the tundish 31, it is prevented from solidifying at the entrance of the tundish 37 and becoming unable to conduct electricity. Moreover, the time for dissolving the metal material can be shortened.

Further, in this embodiment, as described above, a current is passed between the electrode 52, the five auxiliary electrodes, and the mold 38, and the molten steel in the vicinity is 34 is heated.

On the other hand, the molten steel 34 in the tundish 31 is heated by a coil 35 to a predetermined constant temperature. Here, in a case where the temperature of the molten steel 34 deviates from the predetermined constant temperature, the detection of the temperature change and the working operation of the fill 35 based on the detected temperature difference will be described.

Generally, the electrical resistance of metal changes according to temperature changes, and the resistance value R(L) is expressed by the following formula.

R(1:T)=R(0)(1+αt)・
...(8) R(0); Resistance value at melting temperature R(T): Electrical resistance t at temperature T'C; Hot water temperature"
Difference between C and melting temperature ('C) α; temperature coefficient of resistance (in the case of iron, α = 60 x 10 'deg-') As mentioned above, the electric power between the electrode 52, the five auxiliary electrodes, and the mold 38 The voltage is energized so that the voltage therebetween is constant. Therefore, due to the temperature change of the molten steel 34,
The electrical resistance value of the molten steel 34 changes according to the above-mentioned formula 8, and the value of the current flowing through the molten steel 34 also changes.

Here, tanditshu nozzle 37, brake ring 4
The shape of the molten steel 34 etc. near 7, as described above, is the length!
The following description will be made assuming a cylindrical shape with an axis-perpendicular cross-sectional area S. If the metal has such a shape and has a resistivity ρ, the resistance value R(0) at the melting temperature is R(0)=ρJ2/S...(
9).

First, the tanditsch nozzle 37 and the brake ring 4
The electrical resistance value at the melting temperature is determined as a fixed value R(0) based on the shape of 7 and the physical property values of molten metal such as molten steel 34. Next, the molten steel 34 passes through the tundish nozzle 37 and the break ring 47 per unit time.
The amount of current to be passed between the electrode 52, the five auxiliary electrodes, and the mold 38 is determined by the desired temperature adjustment range for the molten steel 34. From the above, the necessary load voltage is determined in the continuous casting apparatus 30. On the other hand, the current actually flowing through the melt #434 is determined by the following formula.

A=E/R(0)(1+αt)...(10
)E: Constant voltage As shown in the above equation 10, the temperature change of the molten steel 34 in the tundish 31 can be read as a change in the electrical resistance value of the molten steel 34 in the tundish nozzle 37 and the break ring 47. Such a change in the electrical resistance value can be detected, for example, in the power supply device 60 as a change in the flowing current value I, as shown in Equation 10 below.

Therefore, the power supply device 60 reads the change in the current value according to Equation 10, calculates the temperature of the molten steel 34, and if the temperature is different from the desired temperature, adjusts the temperature of the molten steel 1:11 to the desired temperature. The coil 35 is controlled. In this way, the temperature of the molten steel 34 in the tundish 31 can be controlled to a constant temperature.

FIG. 6 is an enlarged sectional view of the vicinity of the break ring 47 of a continuous casting apparatus 30a according to another embodiment of the present invention. This embodiment is similar to the previous embodiment, and corresponding parts are designated by the same reference numerals.What is noteworthy about this embodiment is that in the connecting member 68, the connecting member body 70 is provided with external threads. and threaded part 6
9, the billet size D1a of the dummy bar 66a
For example, a cylindrical intervening member 74 having the same outer diameter is integrally formed.

The connecting member 68 according to this embodiment has an inner size D2a of the tundish nozzle 37 that is relatively smaller than the inner size of the tundish nozzle 37 in the first embodiment, and is used when casting small diameter bars. In other words, when the inner size D2a of the tundish nozzle 37 is relatively small, when the connecting member 68 is heated and melted by applying a load current as in the first embodiment, the connecting member 68 is excessively melted and the dummy bar is formed. It is assumed that even the threaded portion 69 screwed onto the thread 66a will be dissolved. In such a case, the melt inside Tanditshu 31! If the X434 is not sufficiently connected to the dummy bar 66a and an attempt is made to pull out the dummy bar 66a, there is a risk that the dummy bar 66a may be disconnected from each other.

In order to avoid the possibility of such cutting, the intervening member 74 is provided, and even if the connecting member main body 70 continues to melt, the intervening member 74 is cooled by the mold cylinder 39, and this melting does not reach the threaded portion 69. Prevent it from progressing. With such a configuration as well, it is possible to realize an operation similar to the casting operation described in the previous embodiment, and it is also possible to realize effects similar to those described in the previous embodiment.

FIG. 7 is an enlarged sectional view of the vicinity of the break ring 47 of a continuous casting apparatus 301 according to another embodiment of the present invention. This embodiment is similar to the previous embodiment, and corresponding parts bear the same reference numerals. The noteworthy point of this embodiment is that the connecting member 68
In this case, the distance between the end surface 47b of the break ring 47 and the stepped portion 71 of the connecting member 70 is set to 5, and a space is formed therebetween. In this state, the molten steel 34 is poured into the tundish 31, and a voltage is applied between the molten steel 34 and the dummy bar 661) as described in the first embodiment. Furthermore, the dummy bar 661] can be pressed with a constant force in the direction of C2 in FIG. 1 by the pinch roller 48.

That is, in the fIS1 embodiment, the molten steel 34 and the dummy bar 6G
+), there is a risk of local heating and melting, resulting in a short circuit. In order to avoid such a possibility, the dummy bar 665
7 side with a constant force until the connecting member main body 70 is completely melted to prevent a short circuit.

Of course, when the molten steel 34 is poured into the tundish 31, the tip of the connecting member main body 70 before melting partially solidifies and is fixed to the tundish 7 and the nozzle 37.

According to the present invention as described in "Effect" 2, before storing molten metal in the tundish, a dummy bar is inserted into the tundish nozzle provided in the tundish, and the molten metal flows through the tundish nozzle to the tundish. Prevents it from flowing into the mold fixed to the nozzle. A metal material may be placed in such a tundish and melted and refined by induction heating.

Next, power is supplied between the molten metal in the tundish and the dummy bar. The tip of this dummy bar on the tanditsu side is made of a material with a high melting point and high electrical resistance.
The remainder of the gummy bar was formed from a low electrical resistance material. Therefore, the tip of the dummy bar is melted by the power supply and is fused with the molten metal. By intermittently or continuously pulling out the dummy bar whose tip is molten, the molten metal flows into the mold and is cooled and formed into the desired slab! ! I can leave you with 32 things.

[Brief explanation of drawings]

Figure fIS1 is a system diagram showing the configuration of a continuous caster 30 according to an embodiment of the present invention, Figure 2 is an enlarged sectional view showing the configuration around the break ring 47 of the continuous caster 30, and Figure 3 is a continuous caster. A graph explaining the casting operation of the device 30, FIG. 4 is a graph explaining the energization mode of the power supply device 60, FIG. 5 is a graph explaining the temperature characteristics of the electrical resistance of molten metal, and FIG. FIG. 7 is an enlarged sectional view of the vicinity of the break ring 47 of the continuous casting apparatus 30a of another embodiment of the present invention, FIG. 8 is an enlarged sectional view of the vicinity of the break ring 47 of the continuous casting apparatus 30b of another embodiment of the present invention, and FIG. FIG. 9 is an enlarged sectional view illustrating the second prior art. 30... Continuous FR manufacturing equipment, 31... Tanditshu, 34...? Il, 35...Coil, 37...Tandish 7 coil, 38...Mold, 47...
・Break ring, 49... Slab, 52... Electrode,
5...Auxiliary electrode, 60.65...Power supply device, 61
, 63.73...Temperature detection means, 66.66a...
Dummy bar, 68... Connection member, 69... Threaded part,
70...Main body, 74...Intervening member agent Patent attorney Number of strokes Keiichi Figure 2 Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) Insert a dummy bar into a tundish nozzle provided in a tundish where molten metal is stored, and supply power between the molten metal in the tundish and the dummy bar to melt the tip of the dummy bar, A continuous casting method characterized in that a slab connected to a dummy bar is pulled out. (2) The metal in the tundish is melted and refined by induction heating, a dummy bar is inserted into the tundish nozzle provided in the tundish, and electricity is supplied between the molten metal in the tundish and the dummy bar. A continuous casting method characterized in that the tip of the dummy bar is melted and the slab connected to the dummy bar is pulled out. (3) A tundish in which molten metal is stored, a tundish nozzle provided in the tundish, a mold for cooling and molding the molten metal taken out from the tundish nozzle, and a dummy bar inserted into the tundish nozzle. A continuous casting apparatus comprising: a tip of the dummy bar on the tundish side is made of a material with a high melting point and high electrical resistance, and the remaining part of the dummy bar is made of a material with low electrical resistance.