JPS63264253A - Continuous casting method for thin cast slab - Google Patents

Abstract

PURPOSE:To prevent the development of solidified shell caused by sticking and cooling of molten metal supplied between a nozzle and a mold by burying electric conductive body at all round in inner part of end of the nozzle near the mold and conducting high frequency current. CONSTITUTION:The copper-made electric conductive tube 10, which is the electric conductive body, is buried at all round of inner part of the end part of the nozzle 7. At the time of conducting the high frequency current in the electric conductive tube 10, AC magnetic field H is generated in the mold 6 near the end part of the nozzle 7. Therefore, current (i) is induced in the molten metal in the mold 6 near the end,part o. the nozzle 7. In this result, by the induced current (i), the molten metal contacting with the end face of the nozzle 7 can be heated and the development of the solidified shell between the end face of the nozzle 7, and upper metal bloc. 2 and lower metal block 4 forming the mold 6 is not occurred.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a movable mold consisting of an endless band that moves in a fixed direction or a rotary mold consisting of a roll that rotates in a fixed direction. This invention relates to a continuous casting method for thin-walled slabs, which comprises supplying molten metal through adjacent nozzles, cooling and solidifying the molten metal through the mold, and continuously casting thin-walled slabs.

[Conventional technology and its problems]

As a method for continuously casting thin slabs, for example, the following block type continuous casting method is known.

A mobile mold is formed by at least a pair of upper and lower endless bands that move synchronously at the same speed and in the same direction, and a thin slab is cast by supplying molten metal through a nozzle into the mold, As the endless band moves, the slab is pulled out from the mold at the same speed and in the same direction as the endless band, thus continuously casting a thin slab.

FIG. 11 is a schematic side view showing an example of a continuous casting machine used in the conventional block type continuous casting method described above.

The continuous casting machine 1 is arranged below an upper endless band 3, which is composed of a plurality of upper metal blocks 2 continuous in an endless manner, and whose downstream ends are inclined downward in the longitudinal direction. . Like the upper endless belt 3, which is made up of a plurality of lower metal blocks 4 connected in an endless manner, it is made up of a lower endless belt 5 whose downstream end is inclined downward in the longitudinal direction. $12, As shown in the cross-sectional view in the figure, each of the plurality of upper metal blocks 2 constituting the upper endless band 3 has its -
Each of the plurality of lower metal blocks 4 forming the lower endless band 5 is formed into an L-shape with a side wall 4a at the other end. The upper metal block 2 forming the upper endless band 3 and the lower metal block 4 forming the lower endless band 5 meet to form a movable mold 6 having a rectangular cross section.

Each of the upper endless band 3 and the lower endless band 5 moves toward the downstream end at the same speed by a drive mechanism (not shown), as shown by arrows a and b.

Into the mold 6 on the upstream end side is inserted the tip of a nozzle 7 having an inner hole with a rectangular cross section and whose one end is connected to a tundish (not shown).

While moving the upper endless band 3 and the lower endless band 5 at the same speed in the directions of arrows a and b, 1. feeding molten metal in a tundish (not shown) into the mold 6 through the nozzle 7;
A thin slab 8 is cast by cooling and solidifying using a mold 6.

Thin slabs 8 are continuously cast by pulling the slabs 8 cast in this manner in the direction of arrow C as the upper endless band 3 and lower endless band 5 move.

The continuous casting method for thin-walled slabs described above includes an open casting method and a closed casting method. The open casting method is a casting method in which a predetermined cavity 9 is formed on the supply side to prevent the mold 6 from being filled with molten metal when the molten metal is injected into the mold 6 through the nozzle 7. be. On the other hand, the closed casting method is a method in which the mold 6 is filled with molten metal when the molten metal is poured into the cast M6 through the nozzle 7, and the mold 6 is cast without a cavity 9 formed on the supply side. The open casting method has the advantage that molten metal does not enter the gap between the nozzle 7 inserted into the mold 6 and the upper metal block 2 and lower metal block 4.

[Problem that the invention seeks to solve]

However, in the open casting method, it is difficult to maintain the level of the molten metal in the mold 6 at a constant position, and the level tends to fluctuate. As a result, there is a gap between the top surface of the molten metal and the upper metal block 2. , and ripples occur on the surface of the molten metal, making it difficult to stably cast slabs. Furthermore, if the rate at which the slab is pulled out is greater than the amount of molten metal supplied into the mold 6, there is a problem that the slab may break out.

On the other hand, according to the closed casting method, since the level of molten metal in the slab 6 does not fluctuate, the slab can be cast stably. However, as shown in FIG. 13, the molten metal supplied into the slab 6 through the nozzle 7 may not be able to meet the tip surface of the nozzle 7.

A solidified shell is formed by adhering to the upper metal block 2 or lower metal block 4 (not shown in FIG. 13) forming the mold 6 and being cooled. As a result, this solidified shell changes the surface texture of the slab. The problem arises that the metal deteriorates and the casting becomes unstable.

The above-mentioned problems are not limited to the block continuous casting method.
A belt-type continuous casting method that consists of supplying molten metal through a nozzle between two continuously moving belts placed one above the other with a predetermined spacing between them, and between a pair of rotating rolls placed with a predetermined spacing between them. This also occurs in the case of twin-roll continuous casting processes, which consist of feeding molten metal through a nozzle.

Therefore, an object of the present invention is to melt melting material by passing a nozzle whose tip end is close to the mold into a mobile mold consisting of an endless band that moves in a fixed direction or a rotary mold consisting of a pair or one roll rotating in a fixed direction. When continuously casting thin slabs by supplying metal and cooling and solidifying the molten metal by the mold, the supplied molten metal adheres between the tip surface of the nozzle and the mold and is cooled. The object of the present invention is to provide a method for stably and continuously casting thin slabs with excellent surface properties without producing solidified shells.

[Means for Solving Problem C] This invention provides melting through a mobile mold consisting of an endless band that moves in a fixed direction or a rotary mold consisting of rolls rotating in a fixed direction through a nozzle whose tip end is close to the mold. A continuous casting method for thin-walled slabs, which comprises supplying metal, cooling and solidifying the molten metal through the mold to cast a thin slab, and continuously drawing out the slab from the mold. A current-carrying body is buried inside the tip of the nozzle close to the mold over the entire circumference thereof.

A continuous casting method for thin-walled slabs, characterized in that the molten metal near the nozzle tip is heated by passing a high-frequency current through the current-carrying body, thereby preventing the formation of a solidified shell covering the nozzle tip surface and the mold. It is.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 is a schematic vertical sectional view of the vicinity of the nozzle tip in block type continuous casting showing one embodiment of the method of the present invention. As shown in FIG. 1, a movable mold 6 having a rectangular cross section is formed by an upper endless band 3 made up of a plurality of upper metal blocks 2 and a lower endless band 5 made up of a plurality of lower metal blocks 4. As in the conventional case, the tip of a nozzle 7 having an inner hole having a rectangular cross section is inserted therein.

In this invention, cooling water is circulated inside the 6 energizing tube 10 in which a copper energizing tube 10, which is a energizing body, is buried inside the tip of the nozzle 7 over its entire circumference. The current-carrying tube '10 is constantly cooled by the cooling water.

When a high-frequency current is passed through the current-carrying tube 10, a magnetic field is generated around the current-carrying VIO. That is, as shown in FIG.
When a current flows from the front to the back of the paper inside 0,
In the mold 6 near the tip of the nozzle 7.

An alternating magnetic field H is generated in the direction of the arrow. Therefore, a current l is induced in the molten metal near the tip of the nozzle 7 in the mold 6 from the back to the front of the page. As a result, this induced current i can heat the molten metal in contact with the tip surface of the nozzle 7, and as shown in the if diagram, the tip surface of the nozzle 7, the upper metal block 2 forming the mold 6, and the lower metal No solidified shell is generated between the block 4 and the block 4.

FIG. 3 is a plan view showing an example of a nozzle used in the method of the present invention, FIG. 4 is a side view thereof, and FIG. 5 is a front view thereof. As shown in FIGS. 3 to 5, a copper current-carrying tube 10 serving as a current-carrying body is buried inside the tip 7a of the refractory nozzle 7 over its entire circumference.
extends in the length direction along the surface of the nozzle 7, and its both ends protrude upward from the nozzle 7 near the rear end 7b of the nozzle 7, forming a cooling water supply pipe 11 and a cooling water discharge pipe 12. ing.

Each of the cooling water supply pipe 11 and the cooling water discharge pipe 12 is connected to a high frequency power source 14 by a conducting wire 13.

The current-carrying tube lO buried in the tip 7a of the nozzle i has a portion leading to the cooling water supply pipe 11 and a portion leading to the cooling water discharge pipe 12 overlapping each other so as to completely surround the entire circumference of the tip 7a. ing. In this way, it is possible to generate an electromagnetic force with a uniform magnetic flux density in the circumferential direction of the tip C of the nozzle 7. 15 is a flange provided at the rear end of the nozzle 7 for mounting.

FIG. 6 is a plan view showing another example of the nozzle used in the method of the present invention, FIG. 7 is a side view thereof, and FIG. 8 is a partial sectional view thereof. As shown in FIGS. 6 to 8, the tip 7a of the refractory nozzle 7 is formed to be thicker than other parts.

The outer circumference near the tip of the nozzle 7 following the tip 7a is coated with a non-magnetic austenitic stainless steel plate IB in order to improve the strength and prevent deviation of the magnetic field. The outer periphery of the other parts of the nozzle 7 is covered with a common steel plate 17 to improve strength. The arrangement of the current-carrying tube lO1 cooling water supply pipe 11, cooling water discharge pipe 12, conducting wire 13, high frequency power source 14, etc. is as described above.

A specific example of manufacturing a thin slab using a mobile mold made of an endless strip of metal blocks according to the present invention will be described below.

Low carbon aluminum killed steel (0.08XG) was cast using the thin slab production equipment shown in FIG. Mold size is 30+s■
It is thick and 800cm wide. A high-frequency induction heating coil was installed at the tip of the nozzle, and a high-frequency current of 100 KI (Z, 150 kW) was passed through it. The capacity of the high-frequency power supply connected to this was 150% 1. At a casting speed of 20 l in As a result of casting the carbon steel, slabs with extremely few surface defects could be stably cast.

FIG. 9 is a schematic vertical sectional view when the present invention is applied to a belt type continuous casting method. As shown in Fig. 9, it consists of two continuously moving metal belts 18.18 arranged vertically at a predetermined interval and two wooden metal belts (not shown) arranged left and right. Inside the tip 7a of the nozzle 7 inserted horizontally into the movable mold 18, an energizing tube 1O is embedded over the entire circumference. Therefore, no solidified shell is generated between the end face of the nozzle 7 and the metal bell 18.18.

FIG. 10 is a schematic vertical sectional view when the present invention is applied to a twin-roll continuous casting method. 5 As shown in Figure 10,
A rotary mold 2 consisting of a pair of rolls 20, 20 arranged at a predetermined interval and rotating in opposite directions at the same circumferential speed, and weirs (not shown) provided on both sides of the rolls! Inside the tip 7a of the nozzle 7 vertically inserted therein, a current-carrying tube 10 is embedded over the entire circumference. Therefore, no solidified shell is formed between the end face of the nozzle 7 and the roll 20.20.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a movable mold consisting of an endless band that moves in a fixed direction, or.

Molten metal is supplied to a rotary mold consisting of a pair of rotating rolls through a nozzle whose tip is close to the mold, and the molten metal is cooled and solidified by the mold to continuously cast thin slabs. Since a high-frequency current is passed through the tip of the nozzle, the supplied molten metal adheres between the tip of the nozzle and the mold and is cooled, creating a stable thin slab with excellent surface quality without forming a solidified shell. It can be continuously cast and has excellent industrial effects.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of the vicinity of the nozzle tip in a block continuous casting method showing one embodiment of the method of the present invention;
Fig. 2 is an explanatory diagram showing the state of generation of electromagnetic force in the method of this invention, Fig. 3 is a plan view showing an example of the nozzle used in this invention, Fig. 4 is its side view, and Fig. 5 is its A front view, FIG. 6 is a plan view showing another embodiment of the nozzle used in the present invention, and FIG. 7 is a side view thereof, and FIG. 8V! J is a partial vertical cross-sectional view, FIG. 9 is a schematic vertical cross-sectional view when the present invention is applied to a belt-type continuous casting method, and FIG. 10 is a schematic vertical cross-sectional view when the present invention is applied to a twin-row continuous casting method. 1... Continuous casting machine, 2... Upper metal block, '3... Upper endless band, 4...
・Lower metal block, 5... Lower endless band, 6... Mold, 7... Nozzle, 8... Slab, 9... Cavity, 10... Current carrying pipe, 11... Cooling water supply pipe, 1
2... Cooling water discharge pipe, 13... Conductor, 14... High frequency tS, 15... Flange, 18... Austenitic stainless steel plate, 17... Ordinary steel plate, 18
...Belt, 20...Roll, 19.21...Mold.

Claims (1)

[Claims] Molten metal is supplied to a mobile mold consisting of an endless band that moves in a fixed direction or a rotary mold consisting of rolls that rotate in a fixed direction through a nozzle whose tip is close to the mold, and the molten metal is cooled by the mold. In a continuous casting method for thin-walled slabs, which comprises solidifying and casting a thin slab, and then continuously pulling out the slab from the mold, inside the tip of the nozzle adjacent to the mold,
A continuous casting method for thin-walled cast slabs, characterized in that a current-carrying body is embedded over the entire circumference of the nozzle, and a high-frequency current is passed through the current-carrying body to heat the molten metal near the tip of the nozzle.