JPH02255255A - Dummy bar for continuously casting plural layered cast billet - Google Patents

Abstract

PURPOSE:To produce the plural layered cast billet having the target component, composition at both of outer layer and inner layer from initial stage of starting the casting by arranging a weir surrounding a nozzle for lower layer at opening part of space part arranged to a dummy bar head. CONSTITUTION:A submerged nozzle 5 is inserted into inner part of the space part 10 and at the same time, molten metal 7, 6 is poured into a mold. The poured molten metal 6 is prevented from flowing into the space part 10 with the weir 12 and cooled and solidified into the mold, and the solidified shell 8a is grown. The molten metal 7 is filled up into the space part 10 in the dummy bar during this operation and until the time of sufficiently growing the solidified shell and becoming the space part 10 to zone magnetic field range by drawing, the molten metal is poured. Further, by drawing down the dummy bar 2, the molten metal 6 is allowed to flow into the space part 10 while flowing over the weir 12, but at this time, the space part 10 is shifted to below the static magnetic field, and back flow of the molten metal in the space part 10 into the mold does not develop. Therefore, as the mold 1 for continuous casting is filled up with the molten metal at the stage of starting the casting, the solidified shell 8a generated by cooling and solidifying the molten metal 6, is formed on inner wall of the mold 1 for continuous casting.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention is a method for continuously manufacturing multiple M-shaped pieces having surface layers with different compositions from a molten state. This relates to a dummy bar used when constructing.

(Prior art) As a method for manufacturing composite steel materials by continuous casting, two immersion nozzles of different lengths are inserted into a pool of molten metal in a mold, and the discharge holes of each nozzle are set at different positions in the casting direction. Japanese Patent Publication No. 44-27361 discloses a device in which molten metals of different types are injected.

Furthermore, Japanese Patent Publication No. 49-44859 discloses that a refractory partition wall is provided between different types of molten metals poured into a mold, and continuous IS casting is performed while preventing the different types of metals from mixing with each other. has been done.

Furthermore, Japanese Patent Publication No. 63-108947 discloses that a static magnetic field is used between different types of molten metals injected into a paving mold to prevent the two molten steels from mixing while manufacturing multilayer slabs. Disclosed. This creates a static magnetic field in which lines of magnetic force extend across the entire width of the slab in a direction perpendicular to the casting direction, and supplies different types of molten metal to the top of the field using this static magnetic field as a boundary. As a result, mixing of the upper and lower layers at the position where the upper and lower layers contact can be suppressed to a minimum.

(Problem to be Solved by the Invention) Even with the method of manufacturing a multilayer fence piece by preventing the mixing of two types of metals using a static magnetic field, mixing of different types of metals at the start of casting cannot be avoided. In order to pull out the slab, it is necessary to grow a solidified shell with a predetermined thickness on the inner wall of the mold. Figure 3 is a diagram explaining the state in which the solidified shell grows inside the mold at the start of casting. It is.

As shown in FIG. 3(,), a dummy bar 2 and a dummy bar head 3 are placed inside a continuous casting mold 1.

In this state, different types of molten metals 6.7 are respectively supplied into the continuous casting mold 1 from the immersion nozzles 4.5. These molten metals 6.7 are cooled and solidified by contacting the inner wall of the continuous casting mold 1, and a solidified shell 8 is formed on the inner wall. As the solidified shell 8 grows, the dummy bar 2 is lowered as shown by the arrow.

When the dummy bar 2 reaches a predetermined position, the immersion nozzle 5 is lowered as shown in FIG. 3(b) to form vertically separated molten metal baths 6a and 7a in the continuous casting mold 1. . When the dummy bar 2 is lowered in this state, the solidified shell 8a formed from the molten metal bath 6a becomes the outer wall, and a multilayer piece with a solidified shell 8b shaped like I# formed from the molten metal bath 7a is formed inside the outer wall. is obtained. At this time, a static magnetic field is applied by the magnet 9 near the interface between the molten metal baths 6a and 7a, and the flow of the molten metal 6.7 is braked.

However, a considerable amount of time is required until the solidified shell 8 formed from the mixed molten metal 6.7 is separated into solidified shells 8a and 8b. The slabs cast during this period do not have the desired multilayer fiber structure and are therefore discarded, resulting in a decrease in product yield.

In order to avoid this, the molten metal 7 forming the lower molten metal bath 7a is connected at the start of casting. When the state shown in FIG. 3(b) is reached, the immersion nozzle 5 is lowered without injecting the molten metal 7 into the mold 1, and when it reaches a predetermined position, the molten metal 7 is injected. Start. However, in this case, the problem arises that the injection cannot be started stably due to a phenomenon in which the air accumulated in the immersion nozzle 5 is ejected into the mold.

Further, the tip of the immersed nozzle 5 is pressed against a part of the dummy bar head 3, and the immersed nozzle 5 is lowered simultaneously with the lowering of the dummy bar 2, and when it reaches a predetermined position, it is cut off from the dummy bar head 3 and the injection of the molten metal 7 is started. There are other possible methods. However, even in this method, the immersion 7
There is a risk that the molten metal will be inserted between the tip of the X-ru 5 and the γ-dot 3 to the dummy bar or around the contact area and solidify, causing the immersion nozzle 5 to break when it is cut off from the rad 3 to the dummy bar. There is also.

Therefore, the inventor of the present invention proposes to suppress the mixing of molten metal during initial casting by using a dummy bar in which a space is formed to accommodate molten steel for the inner layer during initial casting. proposed in the issue. However, although this had some effect, it was necessary to stop the supply of molten metal 7 after the space inside the dummy bar was filled with molten metal, and it was also necessary to stop the supply of molten metal 7 in the space in the early stage of injection.
When the molten metal flows in, a problem arises in that the metal in the space overflows and mixes before the molten metal poured from the nozzle 4 for the outer layer sufficiently forms the solidified shell 8a of the outer layer 11.

(Means for Solving the Problems) The present invention cools and solidifies different types of molten metals that are divided and injected into the casting space in the mold in the vertical direction, and continuously casts multilayer slabs! ! A dummy bar for continuous casting of multilayer/I cast slabs, characterized in that a space is provided in the dummy bar head, and a weir surrounding a nozzle for the lower layer is attached to the opening of the space. It is a dummy bar.

(Function) Figure 1 shows a series of dummy bars according to the present invention. The state inserted into the mold 1 is shown. A dummy bar head 3 provided on the top of the dummy bar 2 has a space 1 for holding molten metal for the inner layer.
0, and a weir 12 is installed in the opening 11 so as to surround the immersion nozzle 5 for supplying molten metal for the inner layer. and,
The upper section of the space 10 is arranged near the interface between upper and lower molten metal baths formed inside the continuous casting mold 1.

At the same time as the immersion nozzle 5 is inserted into the space 10, molten metal 7.6 is injected into the mold.

The injected molten gold s6 is prevented from flowing into the space 10 by the weir 12, cools and solidifies within the mold, and a solidified shell 8a grows. During this time, the dummy bar internal space 10 is filled with the molten metal 7, and the molten metal 7 is poured until a sufficiently solidified shell is formed and the molten metal 7 is drawn out until it becomes a static magnetic field region. When the gummy bar 2 is further pulled down, the molten metal 6 crosses the weir 12 and flows into the space 10, but at this point, the space 10 has moved under the static magnetic field, and the space 10
No backflow of molten metal into the mold occurs.

Therefore, at the start of casting, the inside of the continuous casting mold 1 is filled with molten metal 6.
Therefore, a solidified shell 8a formed by cooling and solidifying the molten metal 6 is formed on the inner wall of the continuous casting mold 1.

Thereafter, while pulling down the gummy bar 2, molten metal 6.7 is injected from each submerged nozzle 4.5 at a constant pouring rate. Then, a static magnetic field by the magnet 9 is applied near the boundary of the molten metal 6.7 to exert a braking force and maintain the molten metal boundary.

In this way, according to the dummy bar of the present invention, the molten metal baths 6a are vertically separated from each other from the beginning of casting.
and 7a are maintained, the generation of the solidified shell 8 generated from the mixed molten metals 6 and 7 as described in FIG. 3 is suppressed. Therefore, the manufactured multi-layer slab also has a predetermined multi-layer structure substantially starting from the bottom piece, and the yield is significantly improved.

(Example) A continuous casting mold 1 having an internal space with a horizontal cross section of 250 x 980 mm, a weir with a height of 100 + am, and an internal volume of 20,000 e
A dummy bar 2 having a space 10 of ll' at its tip was inserted. A molten metal 7 having a common steel composition and a temperature of 1580° C. was poured into this space 10 from the immersion nozzle 5, and at the same time, a molten metal 6 having a 5US304 composition and a temperature of 1550° C. was supplied from the immersion nozzle 4.

The amount of molten metal 7 poured was adjusted so as not to exceed the internal volume of the space 10. Thereafter, the dummy bar 2 is lowered to form vertically separated molten metal baths 6a and 7a in the continuous casting mold 1, and a multilayer slab is formed at a casting speed of in/min.
I pulled it out of Type 1.

FIG. 2 is a diagram showing the change in the amount of Cr contained in the outer layer of the obtained multi-Mm piece along the casting direction.

As is clear from Fig. 2, in the multilayer slab obtained in this example, an outer layer with a predetermined Cr concentration was formed in a short time from the start of casting, and therefore the molten steel composition reached the target value. The part that was cut off was no more than 20 cm from the bottom of the slab.

On the other hand, when the normal dummy bar 2 shown in Fig. 3 is used, an outer layer with the target Cr content is finally formed at points 5 to 61 from the bottom of the slab, and this unsteady part is cut off. The yield was getting worse because of the

(Effects of the Invention) According to the dummy bar of the present invention, only the molten metal for the surface layer is cooled and solidified on the inner wall surface of the series II plexus type to form a solidified shell without mixing of both metals. As a result, it becomes possible to produce multilayer slabs with target components and compositions for both the outer layer and the inner layer with good yield from the beginning of casting.

[Brief explanation of drawings]

Figure PJ1 shows the state in which the dummy bar of the present invention is inserted into the continuous casting mold. FIG. 3 is a diagram showing changes in the amount of Cr contained along the fi force-forming direction, and FIGS.
) is a diagram showing the start of casting using a conventional gummy bar 6 1... Continuous casting mold, 2... Dummy bar 3... Gummy bar head, 4.5... Immersion 'iR nozzle , 6.7・
... Molten metal, 6a, 7a... Molten metal bath, 8.8a
, 8b... Solidified shell, 9... Magnet, 10... Space, 11... Opening, 12... Weir.

Claims (1)

[Claims] (1) In a dummy bar for continuous casting of multi-layer slabs, which manufactures multi-layer slabs by continuous casting by cooling and solidifying dissimilar molten metals injected vertically into the casting space in a mold, the dummy bar head 1. A dummy bar for continuous casting of multilayer slabs, characterized in that a space is provided in the space, and a weir surrounding a nozzle for a lower layer is attached to an opening of the space.