JPH04258344A - Method and device for horizontal continuous casting - Google Patents

Abstract

PURPOSE:To cast a cast billet having no blow hole by reducing the pressure of a gap part between an upstream side mold and a downstream side mold and casting, and in the casting by using horizontal continuous casting device connected with plural water cooling molds along the drawing direction of the cast billet. CONSTITUTION:This device is a horizontal continuous casting device, where a tundish and the molds are communicated with each other through a nozzle 13 and plural water cooling molds are connected along the drawing direction of cast billet. A silicone rubber-made O-ring 31 is inserted between the frame 17 of the upstream side mold 19 and the downstream side mold 21 so as to surround the cast billet C. The pressure is reduced by a gap (g) between the upstream side mold and the downstream side mold to execute the casting. By this method, as the pressure at the inside of the O-ring is reduced, the generation of the casting defect in the cast billet, such as blow hole, caused by air intruding inside of O-ring into the gap between the inner peripheral face of the mold and a solidified shell, is suppressed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal continuous casting method in which a plurality of water-cooled molds are connected along the direction of drawing a cast slab, and to a device for reducing pressure at a mold connection part in a horizontal continuous casting apparatus. This invention is utilized for continuous casting of billets of carbon steel, stainless steel, and other metals.

0002

[Prior Art] Horizontal continuous casting equipment has lower equipment costs, installation area, and operating costs than vertical continuous casting equipment.
In addition, there is no stress caused by bending the slab, and since the internal pressure of the slab is low, bulging is less likely to occur, and it is particularly economical for small-capacity casting equipment. Therefore, in recent years, horizontal continuous casting equipment has been put into practical use for casting billets and the like.

FIG. 6 shows the main parts of a general horizontal continuous casting apparatus. As shown in the drawings, in the horizontal continuous casting apparatus, a tundish 11 and a mold 18 are in communication via a nozzle 13. Tundish 11, nozzle 13
are made of conventional refractories such as zircon or alumina, respectively. The mold 18 is the upstream mold 1 made of copper.
9 and a downstream mold 21 made of graphite, which is held by a frame 17. The upstream mold 19 and the downstream mold 21 are cooled by cooling water W. A break ring 15 is attached to the inlet side of the upstream mold 19. Break ring 15 is
It is made of heat-resistant ceramics such as boron nitride and silicon nitride.

[0004] 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 and forms a solidified shell S. Formation of the solidified shell S is started from the break ring 15. The break ring 15 prevents the solidified shell S from growing in the opposite direction, that is, toward the nozzle 16 side. A slab formed by solidifying the molten metal M is intermittently pulled out from the exit side of the downstream mold 21 by a pulling device (not shown) such as a pinch roll. Slab C
When the break ring 15 and the solidified shell S are pulled out intermittently, the break ring 15 and the solidified shell S
A gap is created between the ends of the molten metal M, and a new molten metal M flows into the gap to generate a new solidified shell S.

By the way, since the above-mentioned gap is under a negative pressure state and the mold 21 and the break ring 15 are only fitted together, air enters the gap from between the joint surfaces of the two. Furthermore, air also enters between the inner peripheral surface of the mold and the solidified shell from the gap between the upstream mold 19 and the downstream mold 21. The air that has entered is drawn into the molten metal M and remains inside or on the surface of the slab, causing casting defects such as blowholes.

[0006] As a method for preventing air from coming into contact with molten metal in continuous casting, there is a ``Continuous Casting Method and Apparatus'' disclosed in Japanese Patent Laid-Open No. 59-66959. This continuous casting method gas-seals the nozzle and the entrance to the liquid-cooled mold with a layer of inert gas that does not react with the molten metal. Furthermore, the slab coming out of the liquid-cooled mold is sealed with inert gas. To gas-seal the slab emerging from the exit of a liquid-cooled mold with an inert gas, cover the slab with a tubular extension (sleeve) placed in the extension of the exit of the mold, and close the exit of the tubular extension. 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 along the direction of drawing out a slab. The above-mentioned conventional sealing method or device using an inert gas 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 sealing between molds.

Furthermore, in the above-mentioned prior art, the tubular extension (
If the sleeve is the downstream mold, the prior art requires a metal tube to cover the tubular extension. As a result, the structure becomes complicated and the cooling efficiency is low because the slab is not directly water-cooled by the cooling pipe. Therefore, this invention seals the mold connection part of a simple structure that does not hinder the cooling of the mold in a horizontal continuous casting machine,
It reduces the pressure.

[0009]

[Means for Solving the Problems] The horizontal continuous casting method of the present invention uses a horizontal continuous casting device in which a plurality of water-cooled molds are connected along the slab drawing direction. It is characterized by casting by reducing the pressure in the gap between the mold and the downstream mold.

Further, in the horizontal continuous casting apparatus of the present invention, the tundish and the mold communicate with each other through a nozzle, and a plurality of water-cooled molds are connected along the direction of drawing the slab. an annular gasket inserted between an upstream mold and a downstream mold so as to surround the annular gasket, a gas suction hole communicating with the inside of the annular gasket, and a gas suction device connected to the gas suction hole. It is characterized by

[0011] As the annular gasket, an ordinary material having appropriate elasticity and heat resistance (for example, an O-ring made of silicone rubber) is used. To attach the annular gasket, attach the end faces of both molds, the flange face of the mold,
Alternatively, an annular gasket may be sandwiched between frames that hold the mold.

[0012] The gas suction device is composed of ordinary devices and members such as a vacuum pump, filter, and piping. To reduce the pressure inside the annular gasket, provide a gas suction hole that leads to the inside of the annular gasket on the end face of the mold, the flange surface of the mold, or the frame that holds the mold, and connect the gas suction hole to the gas suction device. do. The flow area of the gas suction hole should be large enough to achieve the desired pressure. Furthermore, in order to make the decompression effect of the suction device as effective as possible, it is preferable to seal all the parts that structurally communicate with the outside, such as the contact surfaces of the assembly mold. When implementing the above-mentioned measures, the pressure inside the annular gasket is preferably at least 200 Torr or less, although the closer it is to vacuum, the better.

[0013]

[Operation] By reducing the pressure inside the annular gasket, the air between the inner peripheral surface of the mold and the solidified shell becomes extremely thin. Therefore, it is possible to suppress the occurrence of casting defects such as blowholes in the slab.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 3 show a first embodiment of the present invention, in which square billets are continuously cast. In addition,
Members similar to those shown in FIG. 6 described above are given the same reference numerals, and detailed explanation thereof will be omitted. An O-ring 31 made of silicone rubber is inserted between the frame 17 of the upstream mold 19 and the downstream mold 21 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 graphite plates 22.
and a corner block 26 arranged between adjacent peripheral wall blocks 23. The peripheral wall block 23 and the corner block 26 are made of copper and steel, respectively, and are provided with cooling water passages 24 and 27. Further, a gas suction hole 28 penetrates the corner block 26 at right angles to the cooling water flow path 27. Gas suction holes 28 are provided at each of the four corners, and the total flow area is 200 m.
m2. A gas suction device 41 is connected to the gas suction hole 28 via a pipe 43.

The joint between the peripheral wall block 23 and the corner block 26 is completely sealed using a silicone sealing material 50. The cavity 29 communicates with the outside through the gap between the solidified shell S and the graphite plate 22, so air or nitrogen purged to the outside flows through this gap during suction, but the suction capacity is very low compared to the amount of inflow. Since the pressure is large, the pressure in the cavity 29 is reduced to 200 Torr or less. Therefore, the air existing in the gap between the solidified shell S and the mold 19 becomes extremely diluted, and the occurrence of blowholes is suppressed.

FIGS. 4 and 5 show a second embodiment of the invention. Stainless steel hollow annular gasket 3
3 surrounds the slab C and the upstream mold 19
and the downstream mold 21, and both molds 19
, 21. A slit 34 is cut on the inner peripheral surface of the annular gasket 33 over the entire circumference. Furthermore, gas suction holes 35 are provided at each of the four corners of the outer periphery, and gas suction pipes 37 are connected to these holes.

The flow path area of the slit 34 and the gas suction hole 35 was set to 2000 mm 2 as in the first embodiment. 1st
As in the embodiment described above, the cavity 29 communicates with the outside through the gap between the solidified shell S and the graphite plate 22, so that air or nitrogen purged to the outside flows through this gap during suction. However, since the suction capacity is very large compared to the inflow amount, the pressure in the cavity 29 is reduced to 200 Torr or less. Therefore, the air in the gap between the solidified shell S and the mold 19 becomes very thin, and the generation of blowholes is suppressed.

In the above embodiment, a sealing device is provided between the upstream mold 19 and the downstream mold 21, but if another mold is connected following the downstream mold 21, the sealing device is provided between these molds. A sealing device may be provided.

[0020]

[Example] Table 1 shows SUS303 stainless steel billet (
An example of the present invention in which the inside of an annular gasket was depressurized using the apparatus shown in FIG. 1 in horizontal continuous casting of a 150 mm square) and a comparative example in which depressurization was not performed are shown.

[0021]

[Table 1]

[0022]

According to the present invention, the pressure inside the annular gasket inserted between the upstream mold and the downstream mold and arranged to surround the slab is reduced. This prevents air inside the annular gasket from entering the gap between the inner peripheral surface of the mold and the solidified shell, and causing casting defects such as blowholes in the slab. Furthermore, the mold connection sealing device is simple and the invention can be easily implemented in existing equipment.

Note that when the inside of the annular gasket is purged with nitrogen gas, even if the nitrogen gas enters the gap between the inner circumferential surface of the mold and the solidified shell, the nitrogen gas will be removed even if the steel type is SUS304.
In such cases, it is easy to form a solid solution in the slab, so casting defects such as blowholes do not occur in the slab. However, when the steel type is SUS303 or ordinary steel, nitrogen gas is difficult to form a solid solution in the slab, resulting in blowholes. Therefore, in the case of such steel types, the pressure must be reduced using the present invention. By producing slabs without blowholes, the quality and yield of slabs can be improved, and flaw removal work can be omitted.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the invention, and is a sectional view around a mold.

FIG. 2 is a sectional view taken along line II-II in FIG. 1.

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

FIG. 4 shows another embodiment of the invention, and is a sectional view around the mold.

FIG. 5 is a sectional view taken along line V-V in FIG. 4;

FIG. 6 is a vertical sectional view of a general horizontal continuous casting apparatus to which the present invention is applied.

[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 Gas suction hole 29 Vacancy 31 O-ring 33 Annular gasket 37 Gas suction pipe 41 Gas suction device g void C Slab M Molten metal S Solidified shell W Cooling water

Claims (2)

[Claims] Claim 1: In casting using a horizontal continuous casting device in which a plurality of water-cooled molds are connected along the direction of drawing a slab, casting is performed by reducing the pressure in the gap between an upstream mold and a downstream mold. Characteristic horizontal continuous casting method. [Claim 2] In a horizontal continuous casting device in which a tundish and a mold communicate through a nozzle, and a plurality of water-cooled molds are connected along the slab drawing direction, the upstream mold and the downstream mold surround the slab. A horizontal continuous casting device comprising: an annular gasket inserted between the mold and the annular gasket; a gas suction hole communicating with the inside of the annular gasket; and a gas suction device connected to the gas suction hole. Mold connection pressure reducing device.