JP3318451B2 - Continuous casting method of multilayer slab - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method of a multilayer slab having different compositions of a surface layer and an inner layer, and more particularly to a continuous casting method capable of obtaining a multilayer slab having a uniform surface layer component distribution.

[0002]

2. Description of the Related Art Conventionally, as a technique for continuously casting multilayer cast pieces having different component compositions of an inner layer and an outer layer, for example, Japanese Patent Publication No.
As shown in JP-A-20295, an electromagnet is provided below a single rectangular cross-section casting mold to apply a DC magnetic flux in a direction crossing the thickness of the slab to the slab, and a static magnetic field band formed by the electromagnet is used as a boundary. There is known a method of manufacturing a multilayer slab by separately injecting metals having different compositions from above and below using two injection nozzles and solidifying each of them.

[0003] However, in this conventional method for continuous casting of a multilayer slab, a two intermediate pot and two nozzle system is used.
In addition, since the nozzle for injecting below the static magnetic field zone among the two nozzles is very long, the load on the equipment is large and at the same time, fine adjustment control is required also on the operation side. It is troublesome. In addition, the obtained cast slab was not sufficiently satisfactory in surface layer quality.

[0004]

SUMMARY OF THE INVENTION The present invention solves such a problem of the conventional casting method, and provides a uniform surface layer with simpler equipment and operation by using one intermediate pot and one casting nozzle. It is an object of the present invention to provide a continuous casting method capable of obtaining a multilayer slab having a component distribution.

[0005]

The gist of the present invention is as follows. (1) A molten metal is injected together with a lubricant into a water-cooled mold vibrating at a constant period in a vertical direction, and an electromagnetic force is provided in a vertical plane by an electromagnetic coil disposed around the mold, and a magnetic force below the electromagnetic coil is provided. In the continuous casting method of molten metal for applying a uniform static magnetic field in the width direction of the horizontal component with the electromagnet arranged in the mold installation range, in the molten metal pool above the electromagnet, contained in the lubricant The solute element is moved from the periphery of the molten metal to the center of the mold by the electromagnetic coil.
The upper agitating flow generated by the pinch force
Mix well with the molten metal in the pool and solidify it to form a surface layer .
A method for continuously casting a multilayer slab, wherein the inner layer is formed by solidifying while preventing a solute element from being mixed by the electromagnet in a molten metal pool below the electromagnet, while also performing a temperature compensating action . (2) Instead of including the solute element in the lubricant,
The above (1), which is supplied by solidifying in a wire form.
The continuous casting method as described.

[0006]

The details of the present invention will be described below. FIG. 1 shows an example of a casting facility for suitably implementing the casting method of the present invention,
Reference numeral 1 denotes a continuous casting mold having a rectangular cross section which is provided with vibrations of a predetermined cycle in a vertical direction and has a water-cooled structure, and 2 denotes a molten metal 4 from an intermediate pan (for example, a tundish) 3 in the mold.
No. 5 is an immersion nozzle for injecting, 5 is an electromagnetic coil for surrounding the mold 1 and applying an electromagnetic force having a component in a vertical plane to the molten metal 3 in the mold, 6 is a mold length below the electromagnetic coil 5. Electromagnets 7 arranged horizontally along the sides are lubricants injected onto the molten metal in the mold.

The electromagnetic coil 5 applies a single-phase alternating current to apply an electromagnetic force (pinch force) from the periphery of the molten metal toward the center of the mold, thereby raising the upper surface of the meniscus portion of the molten metal to a convex shape, and forming the mold and the solidified shell. At the same time, the lubricant 7 is well introduced into the gap, and at the same time, a stirring flow is generated as described later. Further, the electromagnets 6 The lower impart static magnetic field by uniform DC magnetic flux in the thickness direction of the molten metal, fulfills the action of the electromagnetic brake, the molten metal by the position of the electromagnet upper pool P ₁ and the lower pool P ₂ Divided into In the present invention, in this state, an appropriate solute element 8 is added so as to be included in the lubricant 7. The solute element is an element necessary to be added to the injected molten metal serving as a base to become an outer layer metal of a desired material. For example, C, Si, M
n and the like.

[0008] In the apparatus of FIG. 1, the molten metal 4 which is injected from the nozzle 2, a uniform plug flow in the lower pool P ₂ by the electromagnetic braking action of the uniform electromagnet in the width direction. On the other hand, the solute element 8 added to the upper pool P ₁
Is the uniform stirred flow K generated by the pinch force of the mold 1 surrounding the electromagnetic coil 5, it is mixed with good molten metal in the upper pool P _1, to form a solidified shell. The solute element 8 is not mixed downward from the interface B of the static magnetic field created by the braking action of the electromagnet 6. Therefore, the lower pool P ₂ below from the interface B, coagulation different components (component solute elements 8 is not included) and the upper pool P _1, the solidified shell has already been formed in the previous upper pool P ₁ Shell Is formed inside. In addition, the electromagnetic coil 5 also performs the temperature compensation function of the upper pool by Joule heat.
In FIG. 1, reference numeral 9 denotes a solidified portion of the surface layer, and reference numeral 10 denotes a solidified portion of the inner layer.

In casting the above-mentioned multilayer slab,
It is necessary to adjust the casting speed so that the mass of the drawn metal and the solidified metal can be balanced.

In the illustrated example, the solute 8 is contained in the lubricant and added. However, in the present invention, the solute is solidified in the form of a wire in the solid state instead of the solute. Alternatively, it can be added via a nozzle. In this wire-shaped addition method, a solute element is
It is possible to add a to the lower pool P ₂ side of the lower.

[0011]

【Example】

Casting conditions-Casting material: low carbon steel-Mold size: 250mm thickness x 1000mm width x 800mm height-Mold vibration: stroke 6mm, cycle 150cpm-Additive element: carbon (added as particles in lubricant powder)-Casting speed: 1 m / min lubricant, the main component _{C-CaO-SiO 2 -Al 2} O 3 -NaF
System ・ Viscosity 1 poise Electromagnetic force conditions ・ Coil height when the mold level and the top of the mold are −100 mm Coil level from the mold level to 200 mm below ・ Magnetic field Single phase alternating current 60 Hz 1200 gauss (maximum effective value) Uniform electromagnet Core height: 200 mm , Core position: 300 from meniscus
mm, maximum magnetic flux density: 3000 Gauss

As a result of casting the multilayer slab under the above conditions, the main components of the obtained composite slab are shown in Table 1, and
FIG. 2 shows the distribution of the surface layer thickness of the present invention and a comparative example (without an electromagnetic coil) in order to check whether a required surface layer portion containing C: 0.08% or more is formed.

[0013] According to Table 1, C is 0.1% on the surface layer side compared to the inner layer.
07% up (about 14.0 ° C / ton for 1% up), Si 0.18% up (about 1.2 ° C / ton for 1% up), Mn 0.9 % Up (1%
Up to about 1.2 ° C / ton. Therefore,
Since the casting speed is about 1.75 ton / min, a temperature compensation of about 6 ° C./min is necessary, but it can be sufficiently compensated because the temperature rise in the mold by the upper electromagnetic coil when it is not added is more than 10 ° C. Further, it can be seen from FIG. 2 that there is a large variation in the thickness without the electromagnetic force (broken line), whereas those with the electromagnetic force of the present invention having a constant thickness are almost uniformly distributed.

[0014]

[Table 1]

[0015]

As described above, according to the casting method of the present invention, it is possible to efficiently produce a multilayer slab having a uniform surface layer component distribution without performing a special operation in a normal one-pot, one-pan-type equipment. Can be manufactured well.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a casting facility for suitably implementing the method of the present invention.

2A is a diagram showing the effect of the embodiment of the present invention, that is, the component uniformity of the surface layer together with a comparative example, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Nozzle 3 Intermediate pan 4 Molten metal 5 Electromagnetic coil 6 Uniform electromagnet 7 Lubricant 8 Solute element 9 Surface layer 10 Inner layer

Continuation of the front page (72) Inventor Kenzo Sawada 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (56) References JP-A-3-243245 (JP, A) JP-A-7 JP-A-290195 (JP, A) JP-A-7-284879 (JP, A) JP-A-7-178521 (JP, A) JP-A-4-279249 (JP, A) JP-A-5-318063 (JP, A) (JP) B-20D (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/00 B22D 11/04 311 B22D 11/07 B22D 11/11 B22D 11/115 B22D 11/108

Claims (2)

(57) [Claims] 1. A molten metal is injected together with a lubricant into a water-cooled mold that vibrates at a constant period in a vertical direction, and an electromagnetic force is provided in a vertical plane by an electromagnetic coil surrounding the mold, and an electromagnetic force is applied to the vertical surface. In the continuous casting method of molten metal that applies a uniform static magnetic field in the width direction of the horizontal component with the electromagnet arranged in the lower mold installation range, in the molten metal pool above the electromagnet, the lubricant The contained solute elements are transferred from the periphery of the molten metal to the mold using an electromagnetic coil.
The uniform agitated flow created by the pinch force towards the heart
Above Te, and good molten metal and mixed by stirring to coagulate in the upper pool to form a surface layer portion, further by Joule heat
A continuous casting of a multilayer slab, characterized in that the molten metal pool below the electromagnet also solidifies while preventing the mixing of solute elements with the electromagnet while forming an inner layer portion. Method. 2. The continuous casting method according to claim 1, wherein instead of including the solute element in the lubricant, the solute element is solidified and supplied in a wire shape.