JPH04313447A - Method for continuously casting complex layer cast slab - Google Patents

Abstract

PURPOSE:To provide a method, in which a complex layer cast slab having different compositions, i.e., chemical components in surface layer part and inner layer part is continuously and industrially produced from molten metal in low cost. CONSTITUTION:In the continuous casting method for the complex layer cast slab by giving DC magnetic flux over the whole width in crossing direction of thickness of the cast slab in a continuous casting mold and supplying the molten metal having different compositions in the upper and lower parts as making the boundary of static magnetic field zone formed in the mold casting direction with this DC magnetic flux, by combining two kinds of the metal compositions so that the relation between liquid density sigma1 for the upper side metal in the above static magnetic field zone and liquid density rho2 for the lower side metal becomes rho1-sigma2<=0.1(g/cm<3>), the complex cast slab is industrially and efficiently obtd. in the low cost.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing a composite metal material from molten metal whose surface layer portion and inner layer portion have different compositions, that is, chemical components.

0002

2. Description of the Related Art As shown in FIG. 2, a direct current magnetic flux is applied across the entire width of a continuous casting mold 1 in a direction that crosses the thickness of a slab 2.
JP-A-1089-1089 discloses a continuous casting method for composite metal materials in which molten metals having different compositions are supplied above and below the static magnetic field zone 3 formed in the vertical direction of the mold by the DC magnetic flux.
This is disclosed in Publication No. 47 and the like.

0003

[Problems to be Solved by the Invention] The above-mentioned conventional techniques show the basic concept of a continuous casting method for composite metal materials that utilizes a static magnetic field formed by direct current magnetic flux.
Depending on how the different metals are combined, convective mixing may occur in the mold based on the density difference, and the DC magnetic flux may not be able to sufficiently suppress the mixing of the two types of molten metals, making it difficult to achieve good separation of these metals. The research conducted by the present inventors has revealed that this problem does not occur.

0004

[Means for Solving the Problems] The present inventors have conducted various studies to solve the above-mentioned problems, and as a result, have discovered the following means. That is, the present invention applies a DC magnetic flux in a direction that crosses the thickness of the slab within the continuous casting mold over the entire width, and creates magnetic fields above and below the static magnetic field zone formed by the DC magnetic flux in the casting direction of the mold as a boundary. In a continuous casting method for a multi-layer slab in which two types of molten metals having different compositions are supplied, the relationship between the liquid density ρ1 of the metal above the static magnetic field band and the liquid density ρ2 of the metal below the static magnetic field band is ρ1 −ρ2 This is a continuous casting method for multi-layer slabs characterized by combining the compositions of two types of metals so that ≦0.1 (g/cm3).

[0005]

[Function] The present invention will be explained in detail below along with its function.

[0006] In order to solve the above-mentioned problems in the conventional technology, the present inventors conducted a detailed study on the relationship between the density difference between two types of metals and the state of separation thereof in the obtained multilayer slab.

FIG. 1 shows the density difference ρ1 −ρ2 between two types of metals.
The relationship between the separation index and the separation index defined by the following equation (1) is shown.

Separation index = (C1-C2)/(C10-C20
) ...(1) C
1: Solute concentration in the slab surface layer C2: Solute concentration in the slab inner layer C10: Solute concentration in the molten steel supplied to the surface layer C20: Solute concentration in the molten steel supplied to the inner layer Note that the molten metal injected above the static magnetic field zone forms the surface layer of the obtained slab, and the molten metal injected below the static magnetic field band forms the inner layer of the obtained slab.

It can be seen from FIG. 1 that the larger the density difference ρ1 - ρ2, the smaller the separation index. This is considered to be because convective mixing occurred based on the density difference, and the effect of suppressing the mixing of the two types of molten metals by DC magnetic flux could not be sufficiently exerted.

[0010] In addition, the critical separation index in order to enjoy composite properties without impairing the properties of the two metals (base metals) corresponding to the surface layer and the inner layer is set to 0.80 according to the research conducted by the present inventors. In order to obtain a good separation that exceeds this critical separation index, the intensity of the DC magnetic flux must be adjusted to 0.0, which is the maximum intensity that can be obtained at an industrially practical level, as shown in Figure 1.
It can be seen that under the condition of 8 to 1.0 Tesla, ρ1 - ρ2 ≦0.1 (g/cm3). Note that the lower the strength of the DC magnetic flux, the lower the separation index.
Since there is a tendency for improvement, this formula is valid even at less than 0.8 Tesla.

[0011] By combining the compositions of two types of metals as described above, it becomes possible to industrially and stably produce multilayer slabs.

0012

[Example] Separate submerged nozzles 4, 4' as shown in FIG.
Two types of molten steel having different compositions were injected into the upper and lower parts of the static magnetic field zone 3 in the continuous casting mold 1 using a molten steel.

[0013] The shape of mold 1 is 250 mm (thickness) x 120
The width was 0 mm, and the casting speed was 1.0 m/min. The position of the static magnetic field zone 3 is 450 mm from the meniscus 6 in the mold 1.
~700mm below, and the strength of the DC magnetic flux is 0.8 and 1
．． The two levels were set at 0 tesla.

Table 1 shows the combinations of two types of cast steel and the densities at each casting temperature.

[0015] Thereafter, the solute concentration distribution in the thickness direction of the cast slab was investigated, and the separation index defined by equation (1) was determined.

FIG. 1 shows the relationship between the density difference ρ1 -ρ2 and the separation index between two types of steel. When ρ1 - ρ2 ≦0, the separation is good and the separation index hardly changes, but when ρ1 - ρ2
It can be seen that at >0, as ρ1-ρ2 increases, the separation index rapidly decreases and the separation condition worsens.

[0017] Furthermore, in order to obtain good separation with a critical separation index of 0.8 or more in order to enjoy composite properties without impairing the properties of the two types of steel (base metal) corresponding to the surface layer and the inner layer,
It can be seen that the compositions of the two types of metals may be combined so that the density difference ρ1 - ρ2 between the two types of steel is 0.1 or less.

[0018]

[Table 1]

[0019]

[0020]

[0021]

[Effects of the Invention] As described above, according to the present invention, it is possible to industrially produce multilayer slabs with different compositions, that is, chemical components, in the surface layer and the inner layer at a low cost and efficiently. Become.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between density difference and separation index, showing the effects of the present invention.

FIG. 2 is a schematic diagram of mold injection.

[Explanation of symbols]

1 Mold 2 Slab 3 Static magnetic field zone 4 Immersion nozzle for surface layer 4’ Immersion nozzle for inner layer 5　Surface solidified shell 5’　Inner layer solidified shell 6 Meniscus

Claims (1)

[Claims] 1. Direct current magnetic flux in the direction across the thickness of the slab is applied to the continuous casting mold over the entire width, and the composition is applied above and below the static magnetic field zone formed by the direct current magnetic flux in the casting direction of the mold. In a continuous casting method for a multi-layer slab in which two types of molten metals having different values are supplied, the relationship between the liquid density ρ1 of the metal above the static magnetic field band and the liquid density ρ2 of the metal below the static magnetic field band is ρ1 −ρ2 ≦ 1. A continuous casting method for multilayer slabs, characterized by combining the compositions of two types of metals so that the composition becomes 0.1 (g/cm3).