JPS6188952A - Method for adding alloy component to mold inside in continuous casting - Google Patents

Abstract

PURPOSE:To dissolve and mix quickly additives for adjusting alloy components and to improve the yield of drawing a target component ingot by providing brake devices which brake and disperse the molten metal discharged from an immersion nozzle and adding the above-mentioned additives between the discharge port and brake dispersion region. CONSTITUTION:Static magnetic field generators 10A, 10B are disposed on one long side of a casting mold 2 as the brake devices and static magnetic field generators 11A, 11B on the other long side on the sides opposite from each other with the immersion nozzle 1 in-between. The supply position of a supply device 4 which supplies the alloy additives 5 to the molten steel in the mold 2 is provided between the discharge port 1A of the nozzle 1 and the brake dispersion region 13A by the static magnetic field. The alloy additives 5 are therefore trapped into the jet-like discharge flow 12 of the molten steel discharged from the port 1A and are then quickly and uniformly stirred as the discharge flow near the region 13A is dispersed and stirred. The dissolution of the alloy additives 5 into the molten steel and the mixing thereof progress smoothly and the alloy components are uniformly dispersed into the ingot.

Description

[Detailed Description of the Invention] Industrial Application Field This invention is applicable to continuous casting of metal such as Y4.
The present invention relates to a method of adding additives for adjusting alloy composition to molten metal in the mold.

Conventional Technology As is well known, in the steel manufacturing process, yield strength, tensile strength, impact resistance, creep strength, fatigue strength, corrosion resistance, oxidation resistance, Various alloying elements are added to impart various physical and chemical properties such as electrical resistance and magnetic susceptibility. As a method for adjusting such alloy components during the steel manufacturing process, for example, when using a general converter steel manufacturing method,
Ni, Cr, and M are elements that are not oxidized or consumed in the furnace.
From the viewpoint of uniform melting, O is usually added into the converter at the same time as scrap is charged, but most of the other alloying components are usually added in a ladle during tapping. However, in the method of adding in a ladle at the time of tapping, the addition angle differs greatly due to the difference in affinity with oxygen, and Aβ, Ca, REM (rare earth elements), etc., which are particularly susceptible to oxidation, are added at the time of tapping. Ladle addition has the disadvantage that the yield fluctuates significantly, so special addition methods such as the wire feeder method or alloy bullet projection method are sometimes adopted. Addition in the steel stock during gas treatment or Ar gas bubbling, addition in the tundish during continuous casting, or addition in the mold are often adopted. Among these methods, the method of adding additives for adjusting alloy components such as ferroalloys in the mold during continuous casting is particularly effective when adding a small amount of additives containing alloy components that are highly oxidizable. It is known that there is.

In this way, in the continuous casting process, additives for adjusting alloy composition (hereinafter referred to as alloy additives) are added into the mold in a ladle or tundish (not shown) as shown in Figures 6 and 7. ) into the discharge stream of molten steel 3 supplied into the mold 2 through the immersion nozzle 1, an alloy additive rIJ5, for example, in the form of a wire is supplied by the alloy additive supply device 4, and the alloy additive 5 is melted to form a slab. 6 (Special rMF!7a57-168755J)
M) is 9Il. In addition, in Fig. 6, 7 is the melt r.
! A3 is the hot water level in the mold, and 8 is the solidified shell of the slab 6.

Problems to be Solved by the Invention In the conventional in-mold alloy addition method as described above, depending on the material and shape of the alloy additive, sufficient melting may not take place in the molten steel. Not only are there restrictions on the shape and material of the alloy additive, but also it is difficult to achieve sufficient uniform dispersion and mixing in the molten steel, resulting in the problem that alloy components tend to be unevenly distributed in the slab. In addition, since uniform dispersion of t\ in the molten steel of the alloy is not achieved quickly, for example, after the addition of alloying additives is started, it is not possible to achieve a state in which the alloying elements are actually uniformly dispersed over the entire transversely cut surface of the slab. It takes a considerable amount of time to achieve this, and therefore there is a problem that the yield of slabs containing the target components is low.

Therefore, this invention achieves rapid dissolution and uniform dispersion of alloy additives supplied into the mold, thereby reducing restrictions on the shape and type of alloy additives, and at the same time solving the problem of alloy composition for slabs. Means for Solving the Problems The method of the present invention involves supplying molten metal such as molten steel into a mold using an immersion nozzle to perform 3% continuous H forming, and adding additives (alloy component adjustment) to the molten metal in the mold. Additive)
In the method of adding molten metal, the mold is provided with a braking device for braking and dispersing the discharge flow of molten metal flowing out from the discharge port of the immersion nozzle, and the molten metal is dynamically dispersed from the discharge port into a dynamic dispersion area of the molten metal by the braking device. It is characterized in that the alloy additive is added at a position between. Here, the braking device may be any device as long as it can brake the discharge flow from the discharge port of the immersion nozzle and disperse the discharge flow, and typically applies a static magnetic field to the discharge flow. A static magnetic field generator that provides braking force can be used.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION FIGS. 1 and 2 show 3! !
! It shows the situation near the mold for each continuous casting, and the mold 2
Among the long sides 2A, 2A and the short sides 2'B, 2B, there are fixed gates t, , T (7
) 211fl (7) Shizu miu raw tlfflOA, 10B
; 11A and 11B are provided. These two sets of static magnetic field generators 10A, IOB:IIA, 11B are
This is for generating a static magnetic field at a position where the jet-like discharge flow of molten steel discharged from the discharge ports 1A and IB of the immersion nozzle 1 passes through, and one set of static magnetic field generators 10A and 10B and the other set A set of static magnetic field generators ff11
1A and 11B are arranged on opposite sides with the position of the immersion nozzle 1 in between, and one of each set is ↑OA; 11A is, for example, I
I, and the other one 10B, 11B of each pair is, for example, an S pole. Note that the positions of these two sets of D[1 field generators 10A, 1108; 11A and 11B are such that the discharge flow of molten steel discharged from the discharge ports IA and 1B of the immersion nozzle 1 does not immediately pass through the static magnetic field, but is located at the discharge ports. They are positioned so that jet-like discharge streams discharged from 1A and 1B travel a short distance and then enter the static magnetic field. The alloy additive supply device 4 for supplying 1P of alloy additive 5 into the molten steel in the mold 2 is located at its supply position (addition position).
is (ffli) between the discharge port 1A of the immersion nozzle 1 and the static magnetic field region 13A induced by one set of static magnetic field generators 10A and 10B (that is, corresponds to the damping dispersion region as described later). is positioned.

When performing continuous casting using the above-mentioned stage weight, the immersion nozzle 1 is
Molten steel is supplied into the mold 2 through the discharge ports 1A and IB of the immersion nozzle 1, as schematically shown in FIGS. 3 and 4.
When passing through the vi regions 13A and 13B of the static magnetic field induced by the static magnetic field generators 10A and 10B: 11A and 11B,
Due to the interaction between the flow of molten steel and the static magnetic field, the discharge flow 1
m VU till power F in the direction opposite to the direction of 2, that is, the direction that decelerates the discharge flow 12 of molten steel
receive b. The jet-like discharge flow 12 discharged from the discharge ports IA and 1B is forcibly dispersed as shown by the white arrows in FIGS. 3 and 4 by the electromagnetic braking force Fb in the braking regions 13A and 13B. The braking area 13
Waste agitation flow will occur near A and 13B. Therefore, the static magnetic field regions [13A and 13B can be rephrased as braking dispersion regions that apply a braking force to the discharge flow 12 to disperse the discharge flow 12. This not only reduces the downward penetration depth of the discharge flow, but also reduces the length in the pouring direction of the region where melt-closing flow and stirring occur, so the kinetic energy of the melt is transferred to the brake valve. ¥1. The kinetic energy is concentrated near the regions 13A and 13B, and the density of kinetic energy at that position increases.

Note that when no magnetic field is applied as described above, no braking force is applied to the jet-shaped discharge flow 12 discharged from the discharge ports 1A and 1B, as schematically shown in FIG. It penetrates deeply downward, and there is less stirring and flow in the upper part of the mold.

According to the experience of the present inventors, when a static magnetic field with a magnetic flux density of 2000 Gauss is applied, the mixing state of molten steel in the mold is improved by about 4 times compared to when no static magnetic field is applied. It has been confirmed that a magnetic flux density of 3200 Gauss can improve the magnetic field by a factor of 10.

Here, in the method of the present invention, as described above, the alloy additive 5 is added at a position between the discharge port 1A of the submerged nozzle 1 and the damping dispersion region 13A by the Shizuoka generator 10A, 108. Therefore, the alloy additive 5 is first trapped in the jet-like discharge flow 12 of molten steel discharged from the discharge port 1A, and then as the discharge flow is dispersed and stirred in the damping dispersion region 13Δ. Stir quickly and evenly. Therefore, the melting of the alloy additive 5 into the molten steel and the subsequent mixing thereof proceed in a circular manner, making it possible to uniformly disperse the alloy components into the slab. In other words, the discharge flow of the molten steel trapping the alloy additive 5 is caused by the braking dispersion class 1
In addition to being dispersed and stirred at j1 with 3△, as mentioned above, the stirring energy density at that position increases, and the molten alloy addition force 5 is rapidly and sufficiently mixed. Furthermore, even if the melting of the alloy additive 5 itself is interrupted, the alloy additive 5 supplied into the mold is trapped in the high-temperature discharge stream 12 with a short elapsed time after being discharged from the discharge port of the nozzle 1. and immediately after that, the first braking failure occurs.
Since the mixture is stirred near Ebisu 13A, the alloy additive 5 also dissolves quickly.

Actual example: After smelting in a 250-ton converter, A1 killed heat, which has been subjected to RH degassing treatment, is cast into a slab with a thickness of 220 mm using a continuous slab casting orifice.
When casting into a slab with a cross-sectional dimension of 1,600 mm and a width of 1,600 mm, 0.1 ma/! An experiment was conducted in which 4+n+n RE-17B alloy wire (REM 60 wt%, B 40 wt?6) was added to the outer layer covered with a thin soft disk. The casting speed is 1.2m/'in
n, and the alloy wire is added through the addition port B (7 (straight 20
As pl)m, the addition rate rN of alloy wire is 0.17 kg
/ It was refreshing. Then, as shown in Fig. 1 and Fig. 2, static El fQ generators 10A and 108:11A are installed on the long side of the mold.
, 11B, DC 800 kVA, a static magnetic field was applied so that the magnetic flux density of the melt in the mold was 2000 Gauss, and an experiment was conducted with no static magnetic field (1, alloy The dispersion state of the elements, especially the dispersion state of B, was investigated by taking samples from each part of the slab.When applying a static magnetic field, the addition position of the alloy additive was determined by the discharge port 1A of the immersion nozzle 1 and the static "jrli" F1 No Distributed Territories 1
It was between 3A and 3A. The results are shown in FIG. Furthermore, the fifth
In the figure, the starting point of the horizontal axis (Shizo taiken) indicates the starting position of alloy addition.

As is clear from Fig. 5, when a static magnetic field is not applied, that is, when no motion is given, the concentration transition of the alloy component (B) is not only M but also lower than the alloy concentration target ratio. A tendency to saturate at low values was observed. The reason for this phenomenon is that when no static magnetic field is applied, the penetration depth of the jet-shaped solute discharge flow into the unsolidified part of the slab is large, which causes the slope of the melt in the direction of injection of the slab. This appears to be because the target alloy concentration is not reached within the n-type. It was also found that when no static magnetic field is applied, the state in which the alloying elements are not uniformly dispersed in the slab continues for a casting length of at least 10 m.

On the other hand, when a static magnetic field is applied to brake the molten steel flow, the concentration transition of the alloy component (B) is extremely rapid, and the time it takes to reach the alloy grade (7) is short and the casting It is clear that the length of the slab is about 2 m, and the target value is uniformly reached on the surface and inside of the slab.

Effects of the Invention As is clear from the above explanation, the method of this invention has the following effects:
>2 Two v1 ribs are provided to brake the flow of FEl metal discharged from the discharge port of the Wi nozzle, and alloy additives are added between the discharge port and the braking region. By supplying the alloy, the alloy additives can be quickly melted and mixed, and slabs with uniformly dispersed alloy components can be quickly produced (q), thus increasing the sampling yield of slabs with the target alloy component concentration. At the same time, it is possible to reliably obtain slabs with no partition plates of alloy components, and the dissolution of alloy additives is also promoted, so there are fewer restrictions on the type and shape of the gold-added proboscis when used, etc. The effect of this can be obtained.

[Brief explanation of drawings]

Figure 1 is a top view of the vicinity of the mold of an M continuous casting machine showing the situation in which the method of the present invention is implemented, Figure 2 is a plan view of Figure 1, and Figure 3 is a diagram showing the method of the present invention. Figure 4 is a schematic diagram showing the flow of molten steel in the case of bumping, corresponding to Figure 1, and Figure 4 is a schematic diagram corresponding to Figure 2, showing the flow of molten steel when the method of this invention is actually applied. FIG. 5 is a line section showing the transition of 3 degrees of 8 as an alloy component of a slab in an actual example, based on the casting distance of the slab. Figure 6 is a west view of the area around the mold of the Enzoku Tozokuri, showing the situation in which the method of adjudication is actually practiced;
The figure is a plan view of FIG. 6, and FIG. 8 is a schematic diagram showing the flow of molten steel in FIG. 6.1... Immersion nozzle, 1. To, 1B...discharge port,
2...J type, 5...Alloy additive, 10A, 10
B; 11A, IIB...Static magnetic field generator as a braking device! , 12...discharge flow, 13. A, 13B...C1 subpart area → 1 field application area.

Claims (2)

[Claims] (1) In a method of continuously casting by supplying molten metal into a mold using an immersion nozzle, and adding additives for adjusting the alloy composition to the molten metal in the mold, the molten metal is discharged from the outlet of the immersion nozzle. A braking device is installed in the mold to brake and disperse the discharge flow of molten metal.
A method for adding alloy components in a mold in continuous casting, characterized in that the additive for adjusting the alloy components is added at a position between the discharge port and a braking distribution area by the braking device. (2) The method for adding alloy components in a mold in continuous casting according to claim 1, wherein a static magnetic field generator is provided as the braking device on the long side of the mold.