JPS61266155A - Method and apparatus for continuous casting of clad ingot - Google Patents

Abstract

PURPOSE:To cast efficiently and continuously a clad ingot having a specified cladding ratio and high joint power by bringing a different molten steel in a core mold into contact with a shell formed by cooling and solidifying the molten steel poured between an enclosing mold and core mold thereby solidifying the molten steel. CONSTITUTION:The molten steel A poured into the peripheral space 3 between the enclosing mold 1 and the core mold 1 is cooled 8, 9 to the solidified shell A2 which is delivered. The different molten steel B of the core mold 1 is then poured into such shell A2 and is solidified in contact therewith to form the solid clad ingot. The alloy layer C having the specified cladding ratio and the high joint power to the contact part is thus formed, by which the good clad ingot is efficiently and continuously cast.

Description

Detailed Description of the Invention "Object of the Invention" (Industrial Field of Application) The present invention involves first forming a hollow outer shell slab using molten steel for the outer shell, and then filling the hollow part of the outer shell slab with the molten steel for the outer shell. The present invention relates to a continuous casting method and an apparatus for continuously casting a clad slab in which the outer shell portion and the core portion are integrally joined by injecting the molten steel for the core material, which is of a different material from the molten steel for the outer shell.

(Conventional Continuous Casting Method and Apparatus) FIG. 3 is a front sectional view schematically showing a conventional continuous casting apparatus for manufacturing clad slabs.

The continuous casting device includes a tandish 20 and an immersion nozzle 21.
．． 22, a mold 23, etc. The tandish 20 has a partitioned layer 24 inside it,
Two types of molten steel, molten steel A for the outer shell and molten steel B for the core material, are prevented from mixing with each other. Further, on the lower surface of the tundish 20, the molten steel A for the outer shell is placed in a mold 23.
An immersion nozzle 21 for injecting the core material molten &DH3 into the mold 23 and an immersion nozzle 22 for injecting the core material molten &DH3 into the mold 23 are vertically arranged side by side. The immersion nozzle 22 for the core molten steel B extends further downward than the immersion nozzle 21 for the outer shell molten steel A, and an inverted dish-shaped weir body 25 is provided around the outlet end 22ail. has been done. A narrow channel 26 is formed between the outer circumferential wall of the weir body 25 and the inner circumferential wall 23a of the mold 23, through which the outer shell melt smA flows.

The situation in which clad slabs are manufactured using the above-mentioned continuous casting apparatus will be briefly explained.

The molten steel A for the outer shell is passed from the tundish 20 to the immersion nozzle 2.
1 and then poured into the mold 23. In the mold 23, the molten steel A for the outer shell temporarily stays on the weir body 25 in the immersion nozzle 22 of the molten steel B for the core material, and flows from the same flow path 26 formed around the weir body 25. mold 2
It sequentially flows down along the inner circumferential wall 23a of No. 3. Then, the portion along the inner circumferential wall 23a is cooled, and an outer solidified shell A is gradually formed. On the other hand, the molten steel B for the core material is poured into the mold 23 from the tundish 20 through the immersion nozzle 22. Therefore, the core material molten steel B flows through the same flow path 26.
The solidified outer shell Ax comes into contact with the inner surface of the solidified shell Ax and gradually solidifies. The thus formed slab is pulled out below the mold 23 through the spray zone to become a clad slab. The clad slab is later subjected to rolling, drawing, etc. to become a clad steel product.

(Problems to be Solved by the Invention) The above-mentioned conventional continuous casting apparatus can be used for outer shell, 1ilA, and core material by providing a divided layer 24 in the tundish 20, separate immersion nozzles 21, 22, and a weir body 25. Melt 5l
Although the molten steel A for the outer shell 81A is prevented from mixing with the molten steel B for the core material, eventually, before the entire molten steel A for the outer shell is solidified in the mold 23, the molten steel B for the outer shell 81A and the molten steel B for the core material are mixed.
As a result, the unsolidified bone of the molten steel A for the outer shell was mixed into the molten steel B for the core material. In other words, in the clad slab manufactured by this method, only a few fins thick part forming the outer shell is 18 m thick for the specified outer shell.
Besides A, most of the alloy material had a new composition, which was a mixture of molten steel A for the outer shell and molten steel B for the core material, and the mixing ratio was extremely unstable. Moreover, when such a rad slab is subsequently rolled or drawn, the metal layer constituting the outer shell is too thin and the degree of processing is extremely unevenly distributed in that part, and in some cases, this may cause the outer shell layer to become unevenly distributed. It was also a cause of peeling. In addition, immersion nozzle 2
1 and 22 are installed side by side in the mold 23, one or both of the immersion nozzles are offset from the center of the mold 23, especially when the molten steel A for the outer shell is used. could not be uniformly injected around the weir body 25 in the immersion nozzle 22. Furthermore, since the weir body 25 of the immersion nozzle 22 is always immersed in molten steel, there remains a major problem regarding the lifespan of the device.

The present invention has been made in view of the above circumstances, and the outer shell portion and the core portion are distributed with a predetermined cladding ratio, and the outer shell portion and the core portion are The joint interface becomes an alloy layer of the molten steel for the outer shell and the molten steel for the core material, and the surface of the alloy layer closer to the outer shell has a composition that gradually approaches the metal composition constituting the outer shell, and conversely, the surface closer to the core material has a composition that approaches the metal composition constituting the outer shell. is a new continuous casting method (hereinafter referred to as
The object of the present invention is to provide a continuous casting apparatus (hereinafter referred to as the apparatus of the present invention) and a continuous casting apparatus (hereinafter referred to as the apparatus of the present invention).

"Structure of the Invention" (Means for Solving the Problems) The gist of the method of the present invention is that the outer peripheral wall of the core mold and the inner peripheral wall of the surrounding mold installed surrounding the core mold Injecting molten steel for the outer shell into the gap, solidifying the molten steel for the outer shell and drawing it out as a hollow shell slab, and piercing the hollow part of the outer shell at the center of the core mold. The molten steel for the core material, which is of a different material from the molten steel for the outer shell, is injected through the heat-retaining flow path and solidified.

In addition, the gist of the device of the present invention is that there is a core mold in which a heat-retaining flow path for molten steel for the core material is passed through in the center, and a peripheral gap between the core mold and the molten steel for the outer shell is injected. and a surrounding mold formed and enclosed.

(Function) Molten steel for the outer shell is first poured into the gap between the outer peripheral wall of the core mold and the inner peripheral wall of the surrounding mold so as to be in contact with these walls, and is poured into the hollow outer shell mold. It is pulled out as a piece. Further, molten steel for the core material is injected into the hollow part of the outer shell slab that is being drawn out from the heat-retaining channel of the core mold. In other words, when the molten steel for the core material is tapped from the core mold, all of the molten steel for the outer shell is already solidified, and it is never possible for these re-molten steels to mix with each other more than necessary. do not have. Moreover, at the time when the molten steel for the core material is tapped from the core mold, the outer shell slab still has a temperature close to the melting point of the material, and the inner surface of the hollow part is in an unoxidized state. Furthermore, since the '1g steel for the core material is injected through the heat-retaining channel, the molten steel for the core material is not cooled and has a temperature considerably higher than the melting point of the material. In other words, when the molten steel for the core material is injected into the hollow part of the outer shell slab, even if the melting point of the molten steel for the outer shell is higher than that of the molten steel for the core material, the melting point of the molten steel for the core material is higher than that of the molten steel for the core material. The inner surface of the hollow part of the outer shell slab is remelted by the temperature of the molten steel, and an extremely good alloy layer is formed at the joint interface between them. The alloy layer has good affinity with both the outer shell slab and the core material, and therefore the bond between the outer shell slab and the core material is extremely good.

(Embodiment) FIG. 1 is a front sectional view schematically showing an embodiment of the apparatus of the present invention. First, the apparatus of the present invention will be explained based on the same figure. The most important parts of the apparatus of the present invention are the core mold 1 and the surrounding mold 5.

The core mold 1 is continuously installed vertically in the core tundish 4 that stores the molten steel B for the core, and inside the center is a fireproof material such as Sialon (silicon nitride) or BN (boron nitride). Object 10 is provided. A heat-retaining channel 2 is provided through the refractory 10 so as to communicate the interior of the core material tundish 4 with the lower region of the core mold 1. The core material tundish 4 is replenished with the core material molten mB by a ladle (not shown).

The surrounding mold 5 is installed so as to surround the outer peripheral wall 1a of the core mold 1, and between the inner peripheral wall 5a of the surrounding mold 5 and the outer peripheral wall 1a of the core mold 1, an outer shell melt is provided. A circumferential gap 3 is formed into which tMA is injected.

Further, a water pipe 8 for cooling the molten steel A for the outer shell is buried and installed inside the outer peripheral wall la of the core mold 1,
A water pipe 9 is buried inside the surrounding mold 5 near the inner peripheral wall 5a. The surrounding mold 5 is connected to the outer shell utilization tundish 7. The tundish 7 for the outer shell material stores the molten steel for the outer shell material, and acts like a condenser to pour the molten steel evenly over the entire circumference in the circumferential gap 3 between the surrounding mold 5 and the core mold 1. runs a business.

In addition, 6 is a ladle, and the f66mA for the outer shell is alternately replenished while the continuous casting operation continues.

A slab support roller 11 is installed in a cooling zone located at the lower part of the apparatus of the present invention, which comprises the core mold 1 and the surrounding mold 5. The slab support roller 11 supports the core mold 1
and a core material injected into the hollow part of the outer shell slab A, which is in contact with and supports the outer surface of the hollow outer shell slab A that is pulled out from the circumferential gap 3 between the outer shell slab A and the surrounding mold 5. This is to prevent the molten steel B from expanding outward due to static pressure (bulging phenomenon).

FIG. 2 shows the core material tundish 4 in FIG. 1. FIG. 2 is a plan view of the apparatus of the present invention, with the shell material tundish 7 and ladle 6 omitted. As shown in the figure, the outer shape of the core mold in this embodiment apparatus is rectangular, and the inner circumferential wall 5a of the surrounding mold 5 surrounding the cough core mold 1 is also formed in a rectangular shape. Therefore, the clad slab manufactured by this method has a rectangular cross-sectional shape.

In addition, although the heat insulation channels 2 of the core mold 1 in the apparatus of this embodiment are shown as having a plurality of heat insulating channels 2 lined up in the center of the refractory 10, the number of holes, opening shape, etc. It is not limited to the example, and may be changed as appropriate depending on the relationship with various casting conditions including the casting speed.

Next, the method of the present invention will be explained based on the embodiment apparatus shown in FIGS. 1 and 2.

The molten steel A for the outer shell material is injected into the circumferential gap 3 from the tundish 7 for the outer shell material. The molten SmA for the outer shell becomes a solidified shell from the part in contact with the inner peripheral wall 5a of the surrounding mold 5 and the part in contact with the outer peripheral wall of the core mold 1 within the circumference pJ3, and becomes a solidified shell below the surrounding mold 5. In this process, a hollow outer shell slab is formed. In addition, from the core material tundish 4 to the core mold 1
The core material molten steel B injected through the heat retaining channel 2 is poured into the hollow part of the outer shell slab. At this time, the outer shell slab A
.

For example, when the molten steel for the outer shell is 535G, the inner surface temperature of the hollow part is approximately 1400°C, and the temperature of the molten steel B for the core material is approximately 1490°C, for example when the molten steel for the core material is 5US304. There is. That is, 535
Since the melting point of G is 1470° C., the core molten steel B has a temperature sufficient to remelt the inner surface of the hollow part of the outer shell slab A. Therefore, an alloy layer C of these metals is formed at the joint interface between the inner surface of the hollow part of the outer shell slab A and the core material 11B. Of course, since the inner surface of the hollow part of the outer shell slab is not exposed to the outside air,
No oxide film is formed at the bonding interface. Also, even if an oxide film is formed on the inner surface of the hollow part of the outer shell slab A2, as mentioned above, the inner surface of the hollow part of the outer shell slab A2 is used as a core material! Since it is remelted by B, it is purified by this. Then, the core material molten steel B gradually solidifies and is cooled through a spray zone or the like (not shown) to become a clad slab.

Furthermore, after the formation of the outer shell slab, when the molten steel B for the core material is poured into the hollow part of the outer shell slab A2, the static pressure of the molten steel B for the core material will cause the outer shell slab to come out. At the same time, the outer shell slab A2 acts to shrink inward due to contraction accompanying solidification and cooling. In this way, the deformation direction of the outer shell slab A and the deformation direction of the core molten steel B are opposite, and these deformation effects cause the outer shell slab A
2 and the core material usage 611B are further strengthened.

Since the present inventor manufactured a clad slab by the method of the present invention, the specific numerical values regarding the manufacturing conditions at that time were
Table 〉 shows.

As is clear from the table below, it can be seen from the data on "interface shear strength" that the clad slab produced by the method of the present invention and the apparatus of the present invention has strong bonding strength.

(Margins below) Continued on next page (1A (Another form of frugality) If the core mold or surrounding mold is equipped with a well-known oscillation function, the friction with the outer shell slab will be reduced and stable casting will be achieved. However, the oscillation vibration is closely related to the inflow of powder, and in the method of the present invention, the degree of friction due to the influence of the molten steel for the core material is difficult to predict, so the intermittent drawing method is adopted. It is preferable that
In the above-mentioned example apparatus, the core mold and the IJ1 enclosure mold were formed into a rectangular shape, but by using those having a circular shape, a round bar-shaped clad slab can be manufactured. Needless to say, it can be done. As described above, the detailed structure of the method of the present invention and the structure and shape of the apparatus of the present invention can be changed as appropriate depending on the embodiment.

"Effects of the Invention" As is clear from the above explanation, according to the method and apparatus for continuous casting of clad slabs according to the present invention, a predetermined cladding ratio between the outer shell part and the core part can be maintained. At the same time, an alloy layer having strong bonding force is formed at the bonding interface, and an excellent clad slab can be manufactured.

[Brief explanation of the drawing]

Figures 1 and 2 schematically show the apparatus of the present invention, with Figure 1 being a front sectional view, Figure 2 being a partially omitted plan view, and Figure 3 being a conventional continuous casting apparatus. FIG.

Claims (1)

[Claims] 1. Injecting molten steel for the outer shell into the circumferential gap between the outer circumferential wall of the core mold and the inner circumferential wall of a surrounding mold installed surrounding the core mold, and solidifying the molten steel for the outer shell. The molten steel for the outer shell is made of a material different from that of the molten steel for the outer shell. A continuous casting method for clad slabs characterized by injecting and solidifying molten steel for the core material. 2. A core mold having a heat-retaining flow path for molten steel for the core material penetrated through the center, and an surrounding mold surrounded by forming a circumferential gap for injecting molten steel for the outer shell between the core mold and the core mold. A continuous casting device for clad slabs, characterized by comprising: