JPS645987B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a horizontal continuous casting apparatus.

In conventional horizontal continuous casting equipment, the tundish nozzle made of refractory material and the water-cooled mold are fixed to each other in order to prevent molten metal from flowing out between the tundish nozzle and the water-cooled mold. It was configured. Therefore, the portion of the tundish nozzle adjacent to the water-cooled mold is cooled, and a solidified shell is formed at the molten metal contact area, which is fixed to the tundish nozzle. Furthermore, since the molten metal enters the pores of the refractory material constituting the tundish nozzle and solidifies as it is, the adhesion force increases. Therefore, when the cast body is pulled out, a so-called breakout, in which the solidified shell is torn, sometimes occurs.

In the prior art to solve this problem, a non-porous silicon nitride ring or boron nitride ring with excellent lubricity is hermetically connected between the tundish nozzle and the mold. These silicon nitride rings and boron nitride rings have a short lifespan and are expensive.
Moreover, even if these materials are used, although they have the effect of alleviating the sticking of the tundish nozzle and the coagulating shell, it is not possible to completely avoid the sticking of the mold tube and the coagulating shell.
As seen in 15332, intermittent extraction is forced.

In order to solve these drawbacks of the prior art, an electromagnetic field generating means that generates a higher magnetic flux density at the bottom than at the top of the molten metal is placed near the boundary between the tundish nozzle and the mold. A horizontal continuous casting facility has been proposed in which the casting is constricted near the boundary (Japanese Patent Application No. 56-94333). By squeezing the molten metal in this way, the molten metal does not come into contact with the tundish nozzle, preventing the solidified shell from sticking to the tundish nozzle as described above, and preventing continuous drawing. It becomes possible.
Furthermore, since it is not necessary to fix the tundish nozzle and the mold, it is possible to vibrate the mold, which also prevents the coagulation shell from sticking to the tundish nozzle or the mold.

However, since the amount of molten metal stored in the tundish changes, the static pressure acting on the surface layer of the molten metal in the tundish nozzle and the mold also changes. In particular, during unsteady conditions such as at the end of casting or when replacing the ladle, the liquid level of the molten metal in the tundish changes greatly, and the static pressure of the molten metal in the tundish nozzle and mold changes accordingly. In such a case, the position where the molten metal squeezed by the electromagnetic field generating means comes into contact with the inner surface of the mold moves in response to fluctuations in static pressure. As the position of contact of the molten metal with the inner surface of the mold changes, the total length of the cooling zone within the mold changes. Since the solidified thickness changes accordingly, it becomes impossible to obtain a good slab. Furthermore, in the mold, the static pressure is greater at the lower part of the molten metal, so even with the electromagnetic field generating means, the contact pressure of the molten metal against the inner surface of the mold tends to be greater at the lower part. Therefore, the cooling effect of the lower part of the molten metal becomes large and uneven cooling makes it impossible to obtain a good slab. This means that
The same is true in the prior art, as shown in Japanese Utility Model Application No. 52-160615, in which an electromagnetic force is generated to apply a restriction to the molten metal from a tundish nozzle toward the center.

Another prior art is Japanese Patent Application No. 53-76130. In this prior art, in order to perform gravity compensation of the molten metal, an electrode is immersed in the molten metal in a tundish nozzle, and a longitudinal current is passed through the molten metal.
It is configured to compensate for the gravity of the slab by generating a magnetic field perpendicular and horizontal to the longitudinal direction of the slab. In such prior art, the electrodes are immersed in the molten metal and a current is supplied to the molten metal, so maintenance thereof is troublesome.

An object of the present invention is to provide a horizontal continuous casting apparatus in which the thickness of the solidified shell produced on the surface layer of molten metal cooled on the inner surface of the mold is uniform along the circumferential direction.

The first invention is characterized in that a plurality of tundish nozzles are arranged in the circumferential direction at least near the boundary with the mold, are arranged more densely in the lower part than in the upper part of the molten metal, and extend in the axial direction of the tundish nozzle and the mold. It consists of a coil wound around a rod-shaped core, and the coil is excited by AC power.
This includes an electromagnetic field generating element that applies a larger electromagnetic force toward the center on the lower part of the molten metal than on the upper part, and a detection means that detects the upper and lower contact start positions of the reduced diameter molten metal on the inner surface of the mold. a first AC power source that excites the coil of the electromagnetic field generating element disposed below the molten metal; and a first AC power source that excites the coils of the remaining electromagnetic field generating elements other than the electromagnetic field generating element disposed below the molten metal. 2
an alternating current power supply, and a first and a second power supply in response to the detection output of the detection means, so that the detection output becomes a predetermined value.
The horizontal continuous casting apparatus is characterized in that it includes a control means for controlling excitation power of an AC power source.

Moreover, the second invention of the present invention provides that a plurality of tundish nozzles are arranged in the circumferential direction at least near the boundary with the mold, and are arranged more densely in the lower part than the upper part of the molten metal, and in the axial direction of the tundish nozzle and the mold. It is constructed by winding a coil around a rod-shaped core extending in the direction of the molten metal, and the coil is excited by alternating current power. a recirculating element, a detection means for detecting the thickness of the solidified shell above and below the cast body at the mold exit, a first AC power source for exciting a coil of an electromagnetic field generating element provided under the molten metal, and a molten metal. a second AC power source that excites the coils of the remaining electromagnetic field generating elements other than the electromagnetic field generating element arranged at the bottom of the second AC power source; , the first and second
A horizontal continuous casting apparatus is characterized in that it includes a control means for controlling excitation power of an AC power source.

According to the first invention of the present invention, the electromagnetic field generating elements, which are formed by winding a coil around a rod-shaped core extending in the axial direction of the tundish nozzle and the mold, are arranged more densely in the lower part than in the upper part. Therefore, gravity compensation of the molten metal can be reliably performed. The detection means detects each of the upper and lower contact start positions of the reduced diameter molten metal with the inner surface of the mold. Therefore, the contact start position where the molten metal contacts the inner surface of the mold can be adjusted to be approximately the same vertically, or so that the lower part of the molten metal is on the downstream side in the drawing direction rather than rising. Thereby, the thickness of the solidified shell of the cast body at the mold exit can be made approximately equal between the upper and lower parts.

Further, according to the second invention, the thickness of the solidified shell in the upper part of the cast body at the mold exit is detected, and thereby an even larger electromagnetic force is applied to the lower part of the molten metal toward the center. The thickness of the solidified shell can be made almost equal between the upper and lower parts of the cast body.

Thus, according to the present invention, the lower part of the electromagnetic field generating element is excited by the first AC power source, and the remaining coil is excited by the second AC power source, and by changing the excitation power, high Quality castings can be obtained.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall system diagram showing the basic configuration of the present invention. In this horizontal continuous casting equipment, the tundish 1 is
A heating device 2 is provided to stabilize the temperature of the molten metal within. Cast body 4 from mold 3
is pulled out from the cooling zone 5 by a drawing device 6 and cut by a cutting device 7 to obtain an ingot 9. This ingot 9 is conveyed by a roller table 10.

FIG. 2 is an enlarged sectional view of the vicinity of the mold 3 according to an embodiment of the present invention. The tundish 1 is lined with a refractory material 11 and stores molten metal 12. A tundish nozzle 14 made of a refractory material is fixed to the tundish 1 by a mounting hardware 13. The mold 3 has a coolant passage 15 in which a copper mold tube 33 is cooled, and a passage 16 for the cast body 4 of the mold 3 communicates coaxially with the tundish nozzle 14 . This mold 3 is fixed to a tundish nozzle 14. Near the boundary 17 between the tundish nozzle 14 and the mold 3, an electromagnetic field generating means 143 having a coil 141 surrounding at least the vicinity of the boundary 17 between the tundish nozzle 14 and the mold 3 is provided. Due to the electromagnetic field of the electromagnetic generating means 143, the molten metal 12 flowing near the boundary 17 is reduced in diameter and constricted radially inward. Therefore, near the boundary 17, the molten metal 12 is prevented from coming into contact with the portion of the tundish nozzle 14 near the mold 3. Therefore, the solidified shell is prevented from sticking to the tundish nozzle 14, and the cast body 4 can be continuously pulled out.

FIG. 3 is a simplified sectional view taken along the section line - in FIG. 2. Tandate nozzle 14
A plurality of electromagnetic field generating elements 142 each having a coil 141 wound around a rod-shaped core 140 extending in the axial direction of the mold 3 are arranged in the circumferential direction to constitute an electromagnetic field generating means 143. Moreover, the electromagnetic field generating elements 142 are arranged more densely in the lower part of the molten metal 12 than in the upper part, so that a large magnetic flux density is applied to the lower part of the molten metal 12. When a current flows through the coil 141 in the direction of the arrow 144, an eddy current is generated in the molten metal 12 in the direction of the arrow 145. The direction of the magnetic field generated by the electromagnetic field generating element 142 is indicated by reference numeral 146. In this way, an electromagnetic force directed radially inward acts on the molten metal 12, causing the diameter to be reduced.

In such an electromagnetic field generating means 143, each electromagnetic field generating element 142 is divided into a plurality of groups, for example, four groups 147, 148, 149, 150 on the upper, lower, left and right sides, and each group 147 to 150 is connected to a power source 151,
152, 153, and 154 are connected. Also, position detection means 155, 156, 157, 1 are provided in the mold tube 3 corresponding to each of the groups 147 to 150.
58 are provided. These position detection means 155
The contact start positions of the molten metal 12 detected by steps 158 to 158 are respectively input to the control means 159. The control means 159 controls the power supplied from each power source 151 to 154 so that each contact start position is in the same predetermined range along the axis of the mold 3.

Also in this embodiment, the cooling conditions for the molten metal 12 are uniform over the entire circumference, and a good slab can be obtained.

As shown in FIG. 2, the position detecting means 155 to 158 are provided to detect the position at which the molten metal starts contacting the upper inner surface and the lower inner surface at the end of the mold tube 33 near the tundish nozzle 14. These position detection means 155 to 15
8 is formed by, for example, embedding a plurality of thermocouples in the mold tube 33 at intervals in the axial direction. The contact start positions at the upper and lower parts of the molten metal 12 detected by the position detection means 155 to 158 are provided to the control means 159.

As described above, when the contact start position of the molten metal 12 to the inner surface of the mold tube 33 is maintained at the same position set at the upper and lower parts, both sides of the molten metal 12 are also necessarily at the same position. Therefore, the molten metal 12 starts to come into contact with the inner surface of the mold tube 33 at the same set position along the axial direction over the entire circumference of the inner surface of the mold tube 33. Thereby, mold tube 33
Since the length of the cooling zone in the molten metal becomes uniform over the entire circumference of the molten metal and the solidification thickness becomes uniform over the entire circumference, a good slab can be obtained.

As another embodiment of the present invention, a solidification thickness gauge may be provided at the exit of the mold 3 to measure the thickness of the solidified shell in the upper and lower surface layer portions of the molten metal 12. The values detected by these coagulation thickness gauges are given to the control means 159. In this way, the thickness of the solidified shell at the exit of the mold 3 is controlled by the control means 159, allowing more precise control. Note that a radiant surface thermometer may be used instead of the coagulation thickness gauge.

When the contact start position at the upper part is on the downstream side in the drawing direction (to the right in FIG. 2) than at the lower part, and when the thickness of the solidified shell is larger at the lower part than at the upper part, the lower group 148 is made smaller than the upper group 147. is also excited with a large amount of power. Therefore, a large electromagnetic force in the center direction acts on the lower part of the molten metal 12, and the contact start position can be moved downstream in the drawing direction, or the mold tube 33 at the lower part of the molten metal 12 can move.
The contact pressure with the inner surface can be reduced. In this way, the thickness of the solidified shell can be made equal in the upper and lower parts at the exit of the mold 3.

In another embodiment of the invention, the electromagnetic field generating means may be movable along the withdrawal direction 45. Thereby, the contact start position of the molten metal 12 can be changed, and the cooling conditions can be changed.

As a further embodiment of the present invention, as shown in FIG. 4 in a simplified manner, a contact start position 166 at the lower part of the mold tube 33 is controlled to a position further forward in the drawing direction 45 than a contact start position 167 at the upper part. You may also do so. In this way, the contact length of the molten metal 12 with the mold tube 33 is different in the upper and lower parts, and the contact length in the lower part is smaller, but the contact pressure with the mold tube 33 in the lower part of the molten metal 12 is greater. . Therefore, even if the contact length is relatively short, the cooling conditions are equal to the upper part,
Therefore, the solidified thickness can be made uniform over the entire circumference of the molten metal 12.

Further, in each of the above-described embodiments, the tundish nozzle 14 and the mold 3 have a rectangular cross-section perpendicular to the axis, but the tundish nozzle 14 and the mold 3 may have a circular cross-section perpendicular to the axis. The inner surfaces of the tundish nozzle 14 and the mold 3 may or may not be flush, that is, the inner diameter of the mold 3 may be increased.

As described above, according to the first invention, the excitation power of the coil is controlled so that the contact start position of the molten metal with the mold is a preset position, so that gravity compensation of the molten metal can be reliably performed. This makes it possible to always achieve cooling under stable cooling conditions regardless of fluctuations in the static pressure acting on the surface layer of the molten metal, and to obtain good slabs. Additionally, the position where the molten metal separates from the tundish nozzle is also maintained at the set position.
It is also possible to stably supply lubricant.

Furthermore, according to the second invention, the thickness of the upper and lower solidified shells of the cast body at the mold exit can be made almost equal, thereby making the solidified thickness uniform over the entire circumference of the molten metal. be able to. In this way, cooling can always be achieved under stable cooling conditions, and good slabs can be obtained.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram showing the basic structure of the present invention, and FIG. 2 is a mold 3 of an embodiment of the present invention.
3 is a simplified sectional view taken along the section line - in FIG. 2, and FIG. 4 is a simplified sectional view of another embodiment of the present invention. 3...mold, 12...molten metal, 14...
Tandate nozzle, 17... Boundary, 24...
Solidification shell, 45... Drawing direction, 143... Electromagnetic field generating means, 151, 152, 153, 154
...Power supply, 155, 156, 157, 158...
Position detection means, 159...Control means, 166,1
67...Contact start position.

Claims (1)

[Scope of Claims] 1 A plurality of tundish nozzles are arranged in the circumferential direction at least near the boundary with the mold, and are arranged more densely in the lower part than in the upper part of the molten metal, and in the axial direction of the tundish nozzle and the mold. It is constructed by winding a coil around an elongated rod-shaped core, and the coil is excited by alternating current power, thereby generating an electromagnetic field that exerts a larger electromagnetic force toward the center on the lower part of the molten metal than on the upper part. an element, a detection means for detecting each of the upper and lower contact start positions of the reduced diameter molten metal on the inner surface of the mold, a first AC power source that excites a coil of an electromagnetic field generating element provided under the molten metal; a second AC power source that excites the coils of the remaining electromagnetic field generating elements other than the electromagnetic field generating element disposed below the metal; and a second AC power source that responds to the detection output of the detection means and makes the detection output a predetermined value. so that the first and second
1. A horizontal continuous casting apparatus comprising: a control means for controlling excitation power of an AC power source. 2. A plurality of rod-shaped cores are arranged in the circumferential direction at least near the boundary with the tundish nozzle and the mold, are arranged more densely in the lower part than the upper part of the molten metal, and extend in the axial direction of the tundish nozzle and the mold, An electromagnetic field generating element consisting of a wound coil, the coil being excited by alternating current power to apply a larger electromagnetic force toward the center on the lower part of the molten metal than on the upper part, and an electromagnetic field generating element at the mold exit. a detection means for detecting the thickness of the solidified shells above and below the cast body; a first AC power source for exciting a coil of an electromagnetic field generating element disposed below the molten metal; and an electromagnetic field disposed below the molten metal. a second AC power source that excites the coils of the remaining electromagnetic field generating elements other than the generating element;
1. A horizontal continuous casting apparatus comprising: a control means for controlling excitation power of an AC power source.