JPS6340290Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to an improvement of a stirring device for pouring molten steel in continuous casting. In a casting method using a continuous casting machine, molten steel is generally supplied from a tundish into a continuous casting mold either directly or through a submerged nozzle. However, in conventional continuous casting, even if the inlet angle of the submerged nozzle and other settings are changed appropriately, the flow of molten steel injected into the continuous casting mold enters relatively deeply into the unsolidified casting area, so that Accompanying slag and air bubbles also penetrate deeply and are captured in the solidified shell, and the viscosity of the molten steel prevents them from floating onto the surface of the molten steel due to the difference in specific gravity between them and the molten steel. There was a problem that product quality deteriorated. Therefore, in order to solve this problem,
As disclosed in Japanese Patent No. 17356, a technique has been proposed in which the flow of molten steel in a continuous casting mold is decelerated using a static magnetic field to disperse and stir the molten steel. As shown in FIG. 1, at a position immediately after the molten steel flows into the continuous casting mold 1, an excitation means 2 consisting of a DC exciting electromagnet or a permanent magnet having magnetic poles sandwiching the molten steel is placed outside the continuous casting mold 1. The flow of the molten steel 5 is slowed down by applying a static magnetic field 6 to the molten steel 5 flowing into the continuous casting mold 1 from each inlet 4 of the immersion nozzle 3 in a direction crossing the flow direction. This produces an upward dispersion flow 7, thereby causing dispersion and stirring in the molten steel. According to this technology,
The generation of an upwardly dispersed flow of the molten steel 5 effectively prevents the entrainment of slag and air bubbles, and also reduces the penetration depth of the molten steel flow into the unsolidified casting region based on the deceleration of the flow, and the solidification of the molten steel flow. By preventing the collision with the shell 8, slag and air bubbles are prevented from floating up to the surface of the molten steel and being captured by the solidification shell 8, respectively. Note that 9 in FIG. 1 indicates a cooling box in the width direction of the continuous casting mold 1. However, according to such prior art, since the excitation means is fixed at a specific position, it is not only impossible to effectively deal with changes in casting width, but also, for example, to increase the immersion depth of the immersion nozzle or to change the casting speed. There was a problem in that it was not possible to cope with the increase in the flow velocity and penetration depth of molten steel, and as a result, the injected molten steel could not be sufficiently dispersed and stirred, resulting in a decline in product quality. This invention provides a stirring device for cast molten steel that advantageously solves the problems of the prior art.In particular, the excitation means arranged outside the continuous casting mold is expanded and contracted in the width direction of the continuous casting mold. , by making it movable in the height direction,
The excitation means is sufficiently adapted to changes in the casting width and the depth of penetration of the molten steel, so that the molten steel is constantly and reliably dispersed and stirred. This invention will be explained in detail below based on the drawings. FIG. 2 is a horizontal sectional view showing an embodiment of this invention. In the figure, 11 is an internally cooled copper continuous casting mold.
Reference numeral 12 indicates a guide frame adjacent to and sandwiching the continuous casting mold 11 in the thickness direction, and this guide frame 12 slidably accommodates excitation means consisting of a DC excitation electromagnet to be described later. Reference numeral 13 indicates a two-hole immersion nozzle that enters into the continuous casting mold 11, and 14 indicates a DC excited electromagnet each having a pair of magnetic poles, which is disposed within a guide frame 12 that sandwiches the continuous casting mold 11 in the thickness direction. These electromagnets 14 have opposing magnetic poles across the continuous casting mold 11. This electromagnet 14 consists of an iron core 15 that is approximately U-shaped facing the continuous casting mold 11 and a coil 16 wound around the middle part of the iron core 15. A half part 15a is divided into two in the length direction and has a fitting hole 17, and the other half part 15b has a protrusion 18 that fits into the fitting hole 17 and slides inside the hole.
It consists of. Therefore, the half portions 15a and 15b can be guided by the guide frame 12 and moved toward and away from each other in the axial direction of the fitting hole 17 and the projection 18. On the other hand, a half portion 15 from the outside of the guide frame 12
In order to effect such a relative displacement of rods 19a and 15b, rods 19a and 19b are attached to each of them, respectively, extending through the side wall of the guide frame 12 in the axial direction, so that the rods 19a and 19b are displaced from the guide frame 12. The protrusions are respectively connected to mutually synchronized first drive means 20a, 20b. Here, as the first drive means 20a, 20b, it is of course possible to use a rack and pinion, a cylinder device, or other known reciprocating drive means, but in this example, a female threaded member driven by an electric motor is used as the first drive means 20a, 20b. , 19b, ensuring smooth and accurate operation of the half portions 15a, 15b. The electromagnet 14 also connects to the aforementioned first driving means provided on the top of the guide frame 12 via rods 21 installed vertically in each half portion 15a, 15b, as shown in longitudinal section in FIG. 20a, 20b, and is connected to a second drive means 22 similar to 20a, 20b.
As is clear from FIG. 5, the driving means 22 of
By guiding the vertically elongated holes 23 provided in the side wall of the guide frame 12 in lifting and lowering the rods 19a and 19b passing therethrough, the electromagnet 14 is moved up and down as required. In addition, 24 in the figure indicates rods 19a, 19 that are fitted into the elongated hole 23 and pass through it.
Fig. 3 shows a flanged sleeve that guides the raising and lowering of b. In the apparatus configured in this way, if a direct current is passed through the coils 16 of each electromagnet 14 placed at appropriate positions depending on the width of the continuous casting mold 11 and the depth of penetration of molten steel therein, continuous casting will start. A static magnetic field 25 is generated between the magnetic poles sandwiching the mold 11. As described with reference to FIG. 1, this magnetic field 25 acts on the molten steel flow flowing into the continuous casting mold 11 from the injection port of the two-hole immersion nozzle 13, decelerating it and causing an upward dispersion flow. Since the electromagnet 14 disperses and stirs the molten steel flow, the properly positioned electromagnet 14 prevents slag and air bubbles from reaching the solidification shell, and provides sufficient floating of them to the surface of the molten steel. Here, for example, the width of the continuous casting mold 11 is set to the sixth width.
When it becomes necessary to widen the width from the position shown by the solid line to the position shown by the imaginary line in the figure, the excitation means is fixed and a static magnetic field is applied to the inflowing molten steel flow after widening. can not act properly to effectively prevent it from reaching the coagulation shell and to disperse it upwardly enough to prevent it from passing downwardly in the vicinity of the coagulation shell. On the other hand, according to this invention, in such a case, first, the electromagnet 14 is demagnetized, and then the first drive means 20a, 20b are operated to guide each half portion 15a, 15b of the iron core 15 on the guide frame 12. By separating the electromagnets 14 from each other under At this time as well, sufficient dispersion and stirring of the molten steel flow is provided. Furthermore, if it is necessary to deepen the immersion depth of the two-hole immersion nozzle 13 or increase the flow velocity of the molten steel flow, the electromagnet 14 is moved between the elongated hole 23 and the elongated hole 23 by operating the second driving means 22. sleeve 24
In cooperation with the guide frame 12, the molten steel flow can be guided down to the optimum depth, whereby the molten steel flow can be appropriately dispersed and stirred as in the case described above. Note that this excitation means 14 can be sufficiently operated based on the opposite operation of the first drive means 20a, 20b or the second drive means 22 even if a need opposite to each of the above-mentioned needs arises. Of course, it can perform its functions. Therefore, with such a device, it is possible to appropriately cope with changes in the casting width, the depth of the submerged nozzle, or the flow rate of molten steel, and always provide sufficient product quality. By the way, as a result of applying the device according to this invention to a curved two-strand slab continuous casting machine and operating it under the conditions shown in Table 1,

[Table] The pinhole index of the slab for cold-rolled steel sheets was as shown in Table 2.

[Table] This shows that the device according to this invention is twice as effective in improving the surface texture as compared to the conventional technology shown in Figure 1 with respect to changes in slab size and casting speed. be. Therefore, according to this invention, by making the excitation means consisting of a DC excitation electromagnet expandable and contractible in the width direction of the continuous casting mold and movable in the height direction, the acting position of the static magnetic field can be adjusted to the casting width. , changes in the depth of the immersion nozzle, changes in the flow rate of molten steel, etc. can be appropriately followed, so slag and air in the molten steel can be sufficiently eliminated to always obtain products of reliable quality.

[Brief explanation of drawings]

Figure 1a is a plan view showing a conventional example, Figures 1b and c
are sectional views taken along lines bb and c-c in Fig. 1a, Fig. 2 is a cross-sectional view showing an embodiment of this invention, Fig. 3 is an enlarged sectional view of the electromagnet, and Fig. 4 is a cross-sectional view taken along lines bb and c-c in Fig. 1a. A cross-sectional view taken along the - line in FIG. 2, FIG. 5 a is an explanatory diagram showing the lifting mechanism of the electromagnet, and FIG.
FIG. 6 is an explanatory diagram showing how the casting width is changed. 11... Continuous casting mold, 12... Guide frame, 1
3...2-hole immersion nozzle, 14...DC excitation electromagnet, 15...iron core, 15a, 15b...half portion, 16...coil, 17...fitting hole, 18...
Protrusion, 19, 19a, 19b, 21...rod,
20, 20a, 20b...first driving means, 22
...Second driving means.

Claims (1)

[Scope of utility model registration request] A pair of DC exciting electromagnets placed on each of the long side walls of the continuous casting mold, sandwiching the mold and having different magnetic poles, are used to control the flow of molten steel introduced into the mold through a two-hole immersion nozzle. The electromagnet is a stirring device that decelerates the speed, and the electromagnet has a two-part structure in which the iron core is fitted together, and a guide frame supporting the electromagnet has a side wall that controls the expansion and contraction of the electromagnet in the mold width direction. 1. A stirring device for pouring molten steel in continuous casting, characterized in that a first drive means is provided, and a second drive means for controlling the vertical movement of the electromagnet is provided on the top wall of the first drive means.