JPH05208247A - Horizontal continuous casting method - Google Patents

Abstract

PURPOSE:To prevent the generation of casting defect, such as blow hole, by supplying seal gas being soluble to a cast metal and casting. CONSTITUTION:A silicone rubber-made O ring is inserted in between an upstream side mold 19 and a downstream side mold 21, and a seal gas introducing pipe 28, piping 43 and gas cylinder 41 are brought into contact with a cooling water flowing passage in a corner block at the right angle. The high pressure gas of N2, etc., in the gas cylinder 41 is reduced to about 5kgf/cm<2> gage pressure through a pressure reducing valve 45. The seal gas is invaded into the gap between the inner peripheral surface of the molds 19, 21 and a solidified shell S and since the solid solution of the gas into a cast billet is easily developed, the casting defect, such as the blow hole, can not be developed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of sealing and casting a mold connecting portion in a horizontal continuous casting apparatus in which a plurality of water-cooled molds are connected along a slab drawing direction. The present invention is used for continuous casting of carbon steel, stainless steel, and billets of other metals.

[0002]

2. Description of the Related Art A horizontal continuous casting machine requires less equipment cost, installation area and operating cost than a vertical continuous casting machine,
Further, no stress is generated due to bending of the slab and the internal pressure of the slab is small, so that bulging is less likely to occur. Therefore, a slab having a good shape and quality can be produced, and the yield of maintenance and the like can be improved. Therefore, economical efficiency is particularly good in a small-capacity casting facility. Therefore, in recent years, a horizontal continuous casting apparatus has been put into practical use for casting billets and the like.

FIG. 6 shows a main part of a general horizontal continuous casting apparatus. As shown in the drawing, in the horizontal continuous casting apparatus, the tundish 11 and the mold 18 are connected via a nozzle 13. Tundish 11, nozzle 1
No. 3 is made of a normal refractory material such as zircon or alumina. The mold 18 is composed of an upstream mold 19 made of copper and a downstream mold 21 made of graphite, and is held by the frame 17. The upstream mold 19 and the downstream mold 21 are cooled by the cooling water W. A break ring 15 is attached to the inlet side of the upstream mold 19. Break ring 15
Is made of heat resistant ceramics such as boron nitride and silicon nitride.

The molten metal supplied from the ladle 10 to the tundish 11 is supplied to the mold 18 through the nozzle 13. The molten metal M supplied into the mold 18 is cooled by the inner peripheral surface of the mold to form a solidified shell S. The formation of the solidified shell S is started by the break ring 15. The break ring 15 prevents the solidified shell S from growing in the opposite direction, that is, on the nozzle 16 side. The slab formed by solidifying the molten metal M is intermittently drawn from the outlet side of the downstream mold 21 by a drawing device (not shown) such as a pinch roll.
When the cast slab C is pulled out intermittently, a void is created between the break ring 15 and the end of the solidified shell S, and the molten metal M newly flows into the void to generate a new solidified shell S.

By the way, since the void is in a negative pressure state and only the mold 21 and the break ring 15 are fitted to each other, air intrudes into the void from between the joint surfaces of the two. Air also enters between the inner peripheral surface of the mold and the solidified shell through the gap between the upstream mold 19 and the downstream mold 21. The invading air is entrained in the molten metal M and remains inside or on the surface of the slab to cause casting defects such as blow holes.

As a means for preventing air from contacting molten metal in continuous casting, there is "Continuous casting method and its apparatus" disclosed in JP-A-59-66959.
In this continuous casting method, the nozzle and the inlet of the liquid-cooled mold are gas-sealed with a layer of an inert gas that does not react with the molten metal. Furthermore, the slab coming out of the outlet of the liquid cooling type mold is gas-sealed with an inert gas. To gas seal the slab coming out of the liquid-cooled mold outlet with an inert gas, cover the slab with a tubular extension (sleeve) located on the extension line of the mold outlet, and Inert gas is supplied to the tubular extension near the end.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a horizontal continuous casting apparatus in which a plurality of molds are connected in the slab drawing direction. The conventional inert gas sealing method or apparatus is applied to a continuous casting apparatus in which the mold is composed of one block. Therefore, the above prior art does not suggest anything about the seal between the molds.

Since the horizontal continuous casting apparatus according to Japanese Patent Laid-Open No. 59-66959 uses an inert gas such as Ar as a seal gas, the inert gas is entrained in the molten steel to cause a casting defect such as a blow hole in a slab. Occurs. Therefore,
It is an object of the present invention to prevent the occurrence of casting defects such as blowholes in cast slabs caused by the sealing gas being entrained in molten steel.

[0009]

SUMMARY OF THE INVENTION The present invention is a casting using a horizontal continuous casting apparatus in which a plurality of water-cooled molds are connected along the slab drawing direction, and the entire circumference between the upstream mold and the downstream mold. It is characterized in that a seal gas that is soluble in the casting metal is supplied to the inside to cast. As the metal-soluble gas (hereinafter referred to as a soluble gas), one kind or a mixed gas of two or more kinds such as nitrogen gas, carbon dioxide gas, carbon monoxide gas, hydrogen gas, methane gas, propane gas, and ammonia gas is used. . The pressure of the soluble gas is slightly higher than the atmospheric pressure, for example, 0.5 to 3.0 kgf /
The pressure is about cm ² gauge pressure, and the supply amount is preferably about 50 to 300 l / min.

The seal gas supply device is composed of ordinary devices and members such as a gas cylinder, a pressure reducing valve, and piping. In order to supply the seal gas to the inside of the entire circumference between the molds, a gas introduction hole is provided in an end surface of the mold, a flange surface of the mold, a frame holding the mold, or the like, and a gas supply pipe is connected to or penetrates the gas introduction hole.

[0011]

1 to 3 show a first example of a device for carrying out the present invention, in which a square billet is continuously cast. The same members as those shown in FIG. 6 described above are designated by the same reference numerals, and detailed description thereof will be omitted. An O-ring 31 made of silicon rubber is inserted between the frame 17 and the downstream mold 21 of the upstream mold 19 so as to surround the slab C, and is sandwiched between the frame 17 and the downstream mold 21.

As shown in FIG. 3, the downstream mold 21 has four peripheral wall blocks 23 holding a graphite plate 22.
And a corner block 26 arranged between adjacent peripheral wall blocks 23. The peripheral wall block 23 and the corner block 26 are each made of steel and provided with cooling water flow paths 24 and 27. Further, a seal gas introduction pipe 28 penetrates the corner block 26 at right angles to the cooling water flow passage 27. Four seal gas introduction pipes 28
A gas cylinder 41 is connected to the via a pipe 43. The high pressure gas in the gas cylinder 41 is decompressed by the pressure reducing valve 45 to about 5 kgf / cm ² gauge pressure and supplied to the seal gas introducing pipe 28.

When the seal gas is supplied from the gas cylinder 41 to the corner block 26 in the mold connecting portion sealing device constructed as described above, a part of the seal gas goes to the upstream mold 19 and another part goes to the downstream mold 21. , Enters the gap g between the inner peripheral surface of the mold and the solidified shell. Since the pressure of the seal gas is higher than the atmospheric pressure, air does not enter the gap g.

The seal gas supplied to the inside of the O-ring 31 enters the gap between the inner peripheral surfaces of the molds 19 and 21 and the solidified shell S. Since the pressure of the seal gas is higher than the atmospheric pressure, air does not enter the void. Further, since the seal gas easily dissolves in the slab, casting defects such as blowholes do not occur. Dissolves in the slab C,
Alternatively, the sealing gas that has been consumed by flowing out from the inlet of the upstream mold 19 or the outlet of the downstream mold 21 to the outside is automatically replenished from the gas cylinder 41.

4 and 5 show a second example of a device for carrying out the present invention. A stainless steel hollow annular gasket 33 is inserted between the upstream mold 19 and the downstream mold 21 so as to surround the cast slab C,
It is sandwiched by both molds 19 and 21. The slit 34 is formed on the inner circumferential surface of the annular gasket 33 over the entire circumference.
Has been cut. A seal gas introduction hole 35 is provided at each of the four corners of the outer circumference, and a seal gas supply pipe 37 is connected to the seal gas introduction hole 35.

The seal gas supplied from the gas cylinder 41 into the annular gasket 33 is the slit 34 of the gasket.
And penetrates into the gap g between the inner peripheral surfaces of the molds 19 and 21 and the solidified shell S. Then, like the first embodiment, the invasion of air from the outside into the gap g is prevented.

In the above device example, the sealing device is provided between the upstream mold 19 and the downstream mold 21.
When a mold is further connected to the mold 21 on the downstream side, a sealing device may be provided between these molds, or may be omitted depending on the solidified state of the slab.

[0018]

EXAMPLE In Table 1, in the horizontal continuous casting of SUS304 stainless steel billet (150 mm square), the example of the present invention in which a soluble gas was supplied to the inside of the O-ring using the apparatus shown in FIG. A comparative example in which gas is supplied or gas is not supplied is shown.

[0019]

[Table 1]

[0020]

According to the present invention, the soluble gas soluble in the cast metal is supplied inside the entire circumference between the upstream mold and the downstream mold. The soluble gas that has entered the gap between the inner peripheral surface of the mold and the solidified shell is likely to form a solid solution in the slab, so that casting defects such as blow holes do not occur in the slab. Therefore, the quality of the slab and the yield are improved, and the scratch removal operation can be omitted.

[Brief description of drawings]

FIG. 1 is a sectional view around a mold, showing an example of an apparatus for carrying out the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a front view showing details of a downstream mold.

FIG. 4 is a cross-sectional view around a mold showing another example of the apparatus for carrying out the present invention.

5 is a cross-sectional view taken along the line VV of FIG.

FIG. 6 is a vertical sectional view of a general horizontal continuous casting apparatus.

[Explanation of symbols]

 10 Ladle 11 Tundish 13 Nozzle 15 Break Ring 17 Frame 18 Mold 19 Upstream Mold 21 Downstream Mold 22 Graphite Plate 23 Peripheral Wall Block 24 Cooling Water Flow Path 26 Corner Block 27 Cooling Water Flow Path 28 Seal Gas Inlet Pipe 31 O-ring 33 Ring Gasket 37 Seal gas introduction pipe 41 Gas cylinder g Void C Cast slab M Molten metal S Solidified shell W Cooling water

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Fujii 3434 Shimada, Hikari City, Yamaguchi Prefecture Nippon Steel Co., Ltd.

Claims (1)

[Claims] 1. In casting using a horizontal continuous casting apparatus in which a plurality of water-cooled molds are connected along the slab drawing direction, the casting metal is soluble inside the entire circumference between the upstream mold and the downstream mold. A horizontal continuous casting method, characterized in that a stable sealing gas is supplied to perform casting.