JPH08155613A - Continuous casting method for molten metal - Google Patents

Abstract

(57) [Abstract] [Purpose] In order to refine the metal structure, various small-diameter oxides generated in the molten metal are dispersed uniformly, and the structure is refined during the rolling and heat treatment in the subsequent process. The object is a continuous casting method for molten metal. [Structure] A water-cooled mold for injecting molten metal is subjected to continuous vibration in a vertical direction and electromagnetic force is applied in a vertical plane by an electromagnetic coil surrounding the mold to continuously perform molten metal casting. In the method, casting is performed while adding a deoxidizing element or oxide to the molten metal in the mold from at least one location.

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 for molten metal, and more particularly to a continuous casting method for uniformly dispersing an oxide in molten metal in order to refine the metal structure.

[0002]

2. Description of the Related Art For example, in the case of continuous casting of steel, molten steel is injected into a mold having a water-cooled structure and a lubricant (powder) is added to the surface of the molten steel so that the mold is vertically vibrated at a constant cycle. However, the molten steel was solidified from the periphery of the molten steel and pulled out downward to obtain a slab. In this casting, in order to obtain a slab with good surface properties, an electromagnetic coil is placed around the position corresponding to the molten steel meniscus portion of the mold, and a pinch force is applied to the molten steel by the electromagnetic force, and the molten steel surface is A technique is widely known in which the lubricant is smoothly inserted between the slab and the mold by raising it (see Japanese Patent Publication No. 57-21408).

In general, non-metallic inclusions of 50 μm or more in the steelmaking process cause product defects and internal defects.
Although it has been considered desirable to remove as much as possible, recently, in the steelmaking process, a large number of small oxides of several μm or less are uniformly dispersed in the steel, and after solidification of the steel, these oxides serve as nuclei for sulfides and carbon.・ A technique has been developed and introduced to control the material properties of steel by diffusing a large number of precipitates such as nitrides to dramatically improve the properties of steel (“Nippon Steel Technical Report No. 351 1993, 64 to 6
(See "Advances in Oxide Metallurgy Technology" on page 9).

[0004]

DISCLOSURE OF THE INVENTION The present invention is to uniformly disperse various small-diameter oxides formed in molten metal in order to miniaturize the above-described metal structure, and to form a structure during rolling and heat treatment in the subsequent process. It is an object of the present invention to provide a continuous casting method for molten metal in which the metal is refined.

[0005]

SUMMARY OF THE INVENTION The gist of the present invention is to vertically oscillate a water-cooled mold for injecting molten metal together with a lubricant with a constant period of vibration in the vertical direction and to vertically arrange the electromagnetic coil surrounding the mold. In a method of continuously casting a molten metal by applying an electromagnetic force to the inside of the mold, the molten metal in the mold is cast while adding a deoxidizing element or an oxide from at least one location. It is in a continuous casting method. By the action of the electromagnetic force, the coarse oxide in the molten metal is levitated, and the fine oxide is uniformly dispersed in the molten metal to obtain a metal slab in which the fine oxide is dispersed.

[0006]

The details of the present invention will be described below with reference to the drawings. Fig. 1 shows the case of continuous casting of molten metal, such as steel, when an alternating current is applied to a single-phase coil placed in the mold so as to surround the outer circumference of the meniscus of the molten steel, and an electromagnetic force is applied to the molten steel toward the center of the mold. FIG. In the figure, 1 is a mold having a water-cooled structure to which a constant vibration is applied in the vertical direction, 2 is a single-phase electromagnetic coil arranged in the mold 1, 3 is molten steel injected into the mold through a nozzle, Reference numeral 4 is a lubricant (powder) that is put on the surface of the molten steel, and 5 is a solidified shell. The coil 2 is wound so as to surround the molten steel, and gives the molten steel a pinch force toward the center of the mold.

As shown, the coil 2 is driven by electromagnetic force.
A flow F ₁ is formed from the mold toward the center of the mold cross section, and two spirals F ₂ and F ₃ that circulate vertically are formed. Under such a flow condition, in the present invention, one or more kinds of deoxidizing agents such as Al, Ti, Zr, Ca, and Mg, or direct oxides from the surface of the molten steel in the mold to the molten steel. Add particles 6. Since oxygen remains in the molten steel after refining, an oxide can be easily generated by adding the deoxidizer, and this serves as a nucleation site for precipitates.

The deoxidizing agent or oxide is at least 1
It may be added in a number of places, but if possible, it is preferable to add it to the surface of the molten steel evenly at a plurality of locations. As a method of addition, a particulate deoxidizer or an oxide may be filled into a thin wire, and the wire may be added by charging it into molten steel,
In some cases, it is possible to add the wire to the injection flow by using an injection nozzle.

The deoxidizer particles react with oxygen in molten steel to form oxides. At this time, oxides in molten steel are distributed from fine ones of submicron to large ones of several hundreds of microns, but if this is left as it is, that is, if a forced flow is not given, the oxide concentration distribution will change. Since there is a difference, and as described above, the large oxide also causes defects, it is necessary to remove it.

However, when the electromagnetic coil 2 is used to force a uniform flow into the molten steel as in the present invention, harmful coarse oxide particles (about 10 μm to 300 μm) of the oxide particles 6 are used.
The a travels along the flow F ₂ from the center of the molten steel toward the solidification shell side, and when the flow reverses downward, it is discharged to the outside of the molten steel by the centrifugal force and trapped in the lubricant 4. In addition, useful minute (several μm or less to submicron) oxide particles 6
b is retained in the molten steel along with the flow as it is, and solidifies in the course of solidification, and is trapped in the solidification shell 5 or precipitated at the solidification interface, so that the oxide approaches a fine and uniform distribution. It is expected that the oxide thus obtained will serve as a site for controlling the structure during rolling and heat treatment in the subsequent process, that is, as a site for forming sulfides and carbon / nitrides that have a great influence on the material properties of steel.

It is sufficient that the amount of the deoxidizing agent such as Al or Ti or the oxide added is about 0.01% by weight to 0.02% by weight.

[0012]

【Example】

Casting conditions-Casting material: Weakly deoxidized aluminum-Mold size: 150mm x 800mm height-Mold vibration: Stroke 6mm, cycle 300cpm
(5Hz) ・ Pulling speed: 2000mm / min ・ Additive: Add 0.01% Al ・ Adding position: Add wire in the immersion injection nozzle Electromagnetic force condition ・ Coil: From melt level (meniscus) to melt level 300mm downward ・ Frequency: 60Hz, sine wave, maximum effective value 1200 gauss

Under each of the above conditions, continuous casting was carried out in the cases of applying a single phase of electromagnetic force (invention example using downward 1-hole nozzle) and not applying electromagnetic force (comparative example using downward 15 ° 4-hole nozzle). went. At this time, the relationship between the oxide particle size and the oxide number index, and the slab circumferential direction positions (A to D are 30 mm average positions in the thickness direction from the approximate midpoint of each side of the mold cross section) and the oxide The relationship with the number index is shown in comparison with FIG. 2 and FIG. As can be seen from the figure, in all cases, the particle size was smaller when the electromagnetic force was applied, and when the electromagnetic force was not applied, the oxide was scattered at the circumferential position of the slab, but when applying the electromagnetic force, It shows a stable index.

[0014]

As described above, according to the casting method of the present invention, various small-diameter oxides formed or added in the molten metal can be dispersed in an optimum state, that is, evenly dispersed. High-quality metal products with a refined structure can be easily obtained by rolling and heat treatment.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of a casting mold portion for carrying out the casting method of the present invention.

FIG. 2 is a diagram showing the results of the present invention and showing the relationship between the oxide particle diameter and the oxide number index.

FIG. 3 is a diagram showing the results of the present invention and showing the relationship between the position of the slab in the circumferential direction and the oxide number index.

[Explanation of symbols]

 1 Mold 2 Electromagnetic Coil 3 Molten Steel 4 Lubricant 5 Solidifying Shell 6 Deoxidizer or Oxide Particles

Front Page Continuation (72) Inventor Kenzo Sawada 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd.

Claims (1)

[Claims] 1. A molten metal in which a water-cooled mold for injecting molten metal together with a lubricant is vertically vibrated with a constant period and an electromagnetic coil is provided to surround the mold to apply an electromagnetic force in a vertical plane. The method for continuous casting of molten metal, wherein the casting is performed while adding a deoxidizing element or oxide from at least one location to the molten metal in the mold.