KR20010055476A - Device for venting the fume in twin roll strip casting machine - Google Patents

Abstract

PURPOSE: An apparatus for discharging fume of a twin roll strip casting machine is provided to prevent cracks of the surface of a strip and obtain even severity of quench in a roll width direction by discharging fume to the outside so that a contaminated mixed gas, fume, which is formed on the upper part of molten metal pool is not adsorbed on the surface of the twin rolls. CONSTITUTION: In a twin roll strip casting machine consisting of twin rolls (3,3a) each of which rotate in an opposite direction; edge weirs (4) installed at both ends of the twin rolls (3,3a) so as to form a molten metal pool (5); a molten metal surface cover (7) installed so as to form an environmental gas space on the upper part of the molten metal pool (5); first and second gas supplying holes (8,9) installed in the molten metal surface cover (7) for supplying non-oxidized gases to the sides of the twin rolls (3,3a) and the molten metal surface; and shielding curtains (11) installed at the molten metal surface cover (7) corresponding to the twin rolls (3,3a) so as to seal the environmental gas space, wherein a strip (20) is casted by passing molten steel through between the twin rolls (3,3a), the apparatus for discharging fume of a twin roll strip casting machine comprises a plurality of discharging holes (10) mounted on the molten metal surface cover (7) in a width direction of the rolls so that fume moving to the center part of the molten metal pool (5) can be discharged to the outside by the ejecting force of the non-oxidized gases which is ejected from the first and second gas supplying holes (8,9).

Description

Fume discharge device of twin roll sheet casting machine {DEVICE FOR VENTING THE FUME IN TWIN ROLL STRIP CASTING MACHINE}

In the present invention, in order to prevent oxidation of the molten metal in the twin-roll type sheet casting machine, the fume is moved out of the atmosphere so that the fume, which is a contaminated gas generated during casting, in the atmosphere gas space of the bottom space of the bottom surface of the bottom cover covering the surface of the molten metal is not moved to the twin roll side. The present invention relates to a fume discharge device of a twin-roll type sheet casting machine that can improve sheet quality by discharging.

Generally, as shown in FIG. 1, the twin roll-type sheet casting machine 100 rotates the molten steel of the tundish 1 in the opposite direction by a driving device not shown through the molten steel injection nozzle 2. (3) The molten pool 5 is formed between the paired rolls 3, 3a and the edge dam 3 which are injected and faced between the three rolls 3a, and through contact between the rotating rolls 3, 3a and the molten steel. It is a facility for casting a thin plate 20 while rapidly solidifying molten steel to form a solidified shell (6).

In order to prevent the molten metal from being oxidized due to the oxygen contained in the gas in contact with the molten metal of the molten metal pool 5 during casting, a part of the upper portion of the upper portion of the paired rolls 3 and 3a and the upper edge dams 4 are formed. In general, a method is provided in which a floor cover 7 is provided to cover the surface of the bath, and the space between the floor and the floor is replaced with a non-oxidizing gas.

In this case, the molten metal of the hot water surface is in contact with the non-oxidizing gas, thereby suppressing oxidation of the molten metal as much as possible, thereby casting the thin plate 20 having excellent quality.

Patents related to the bath surface cover, which is a device for forming a non-oxidizing atmosphere as described above, are disclosed in Japanese Patent Laid-Open No. 6-29711, Japanese Patent Laid-Open No. 7-204794, Japanese Patent Laid-Open No. 8-309489, Japanese Patent Laid-Open No. 9-29397, and the like. Is disclosed.

However, even if the atmosphere space on the surface of the molten pool 5 is filled with non-oxidizing gas, if any of the components of the molten steel are easily evaporated, such as manganese, zinc, and lead, the evaporating component is an atmospheric gas from the molten metal. With this, the atmosphere gas becomes contaminated with fume, a mixed gas in which vapor of evaporation component is mixed with pure non-oxidizing gas.

Despite such phenomena, Japanese Patent Application Laid-Open No. 6-29711 and Japanese Patent Application Laid-open No. 9-29397 only emphasize the mention of the supplied non-oxidizing gas and the sealing for blocking the ambient air. In the atmosphere, the gaseous fumes in the atmosphere gas space cannot escape to the outside.

On the other hand, in Japanese Patent Laid-Open Nos. 7-204794 and 8-309489, a gas discharge passage is illustrated, but there is a problem in the path.

Non-oxidative gas injected from the first gas supply port 8 to the pair of rolls 3 and 3a side and the second gas supply port 9 which are conventionally used in FIG. The supply and discharge paths of the non-oxidizing gas injected with the gas are shown.

That is, when the non-oxidizing gas is supplied through the first and second gas supply ports 8 and 9 mounted on the water surface cover 7, the non-oxidizing gas flows and is contaminated with the evaporated component coming out of the molten metal. Since the fume coming into the twin rolls (3) and (3a) during casting is condensed into solid again, the manganese oxide (MnO) is adsorbed on the roll surface while the fumes in contact with the surface of the twin rolls (3) and (3a) are condensed into solid again. ) Is also adsorbed.

As the fume continues to be adsorbed on the surface of the twin rolls (3) and (3a), it acts to hinder the heat transfer from the molten metal to the surface of the roll. As the casting progresses, the thickness of the solidified shell 6 of the thin plate 20 is generated. The uniformity was generated during thin plate solidification, while lowering the cooling ability of the double rolls 3 and 3a and causing a problem of decreasing the casting speed.

In addition, when the fume escapes to the double roll 3, 3a side, the fume is not discharged evenly over the width of the roll, and is discharged more quickly to the center portion than the edge of the double roll 3, 3a. Since the phenomenon of stagnation of the fume occurs at the edge of, the evaporation component is more easily adsorbed on the surface of the pair roll (3) (3a), there is a problem that the cooling ability of the edge of the roll is lower than the central portion.

Accordingly, the temperature of the edge of the thin plate to be cast is higher than the center portion, causing a cause of deterioration of the quality of the cast. In addition, there is a problem in that cracks are locally generated due to shrinkage occurring during solidification on the thin plate surface to be cast due to uneven adsorption of manganese on the surface of the pair rolls 3 and 3a.

Accordingly, the present invention has been made to solve the above problems, the object of the present invention is to discharge the contaminated mixed gas formed in the upper portion of the molten pool to the outside so as not to be adsorbed on the surface of the twin roll to uniformity between the solidified shell and the twin roll The present invention aims to provide a fume discharge device of a twin roll type sheet caster that can achieve surface heat cracking of a thin plate by obtaining a heat transfer and obtain even cooling ability in a roll width direction.

1 is a schematic view showing a state in which the fume is discharged from a typical double roll type sheet casting machine,

Figure 2 is a working state showing that the fume is discharged from the fume discharge device of the twin-roll sheet caster according to the present invention,

Figure 3 is a plan view showing a fume discharge device of the twin-roll sheet caster according to the present invention.

* Explanation of symbols for the main parts of the drawings *

3,3a ... double roll 4 ..... edge dam

5 ..... molten pool 6 ..... solidified shell

7 ...... Water cover 8,9 ... 1,2 gas supply port

10 ..... outlet 100 ... twin roll sheet casting machine

The present invention as a technical configuration for achieving the above object,

And a pair of rolls rotating in opposite directions, an edge dam provided at both ends of the pair of rolls to form a molten pool, and a bath surface cover provided to form an atmosphere gas space on an upper portion of the molten pool. The first and second gas supply ports for supplying non-oxidizing gas to the side, and the double roll type sheet casting machine for casting a thin plate by passing the molten steel between the two rolls and a shielding curtain so as to seal the atmosphere gas space in the cup cover corresponding to the double roll. In

A pair of the floor cover is provided with a plurality of outlets in the roll width direction in order to exhaust the fumes moved to the center of the melt pool by the injection force of the non-oxidizing gas injected from the first and second gas supply port to the outside By providing fume discharge device of roll type sheet casting machine.

Hereinafter, with reference to the accompanying drawings the present invention will be described in more detail.

2 is a working state diagram showing the discharge of the fume from the fume discharge device of the twin-roll sheet caster according to the present invention, Figure 3 is a plan view showing a fume discharge device of the twin-roll sheet caster according to the present invention.

2 and 3, the first and second gas supply ports 8 and 9 for supplying the non-oxidizing gas to the pair rolls 3, 3a and the hot water side, respectively, as shown in FIGS. ) And a double roll type sheet casting machine (100) provided with a shielding curtain (11) for forming an atmosphere gas space in the upper surface of the hot water by blocking the gap between the hot water surface cover (7) and the double roll (3) (3a). .

That is, the device 90 gas the fume moved to the center of the molten pool (5) by the injection force of the non-oxidizing gas injected from the first and second gas supply ports (8) (9) to the water surface cover (7) In addition, a plurality of outlets 10 are mounted in the roll width direction so as to be exhausted to the outside.

In this case, the shield curtain 11 is installed between the floor cover 7 and the pair rolls 3 and 3a so that the fumes generated while evaporating the components in the molten metal are the pair rolls 3 and 3a. Even if it comes to the side, the contact with the said pair rolls 3 and 3a is interrupted by the injection pressure of the non-oxidizing gas injected from the said 1st gas supply port 8 to the roll side.

The first gas supply port 8 replaces oxygen that may be attached to the surface of the roll while the non-oxidizing gas injected therefrom touches the surface of the pair of rolls 3 and 3a sufficiently, and the generated fume is discharged. It is preferable that the non-oxidizing gas supplied from the gas supply line, which is provided in close proximity to the pair rolls 3 and 3a so as not to be adsorbed on the roll surface, is sprayed directly onto the roll surface.

On the other hand, the second gas supply port (9) naturally gives a pressure gradient in the atmosphere gas space in which the fumes are generated to naturally lead the flow of the generated gas, such as fumes, gas to the center of the molten pool (5) on the injection nozzle (2) side The non-oxidizing gas may be injected at a gas supply amount smaller than that of the first gas supply port 8 that supplies the non-oxidizing gas to the pair rolls 3 and 3a.

Accordingly, when the supply amount of the non-oxidizing gas injected from the first gas supply port 8 is larger than the gas supply amount injected from the second gas supply port 9, the pressure of the roll side is the molten pool 5 having the nozzle side. As it is higher than the central part of the gas stream, the flow of gas such as fume and gas is naturally formed on the molten pool central part on the injection nozzle 2 side having a low pressure on the side of the high pressure double roll 3, 3a.

In addition, the generated fume may be discharged to the edge dam 4 side without discharging to the pair roll 3, 3a side, and discharged through the gap between the edge dam 4 and the bottom cover 7.

In addition, each outlet 10 is equipped with a valve member (not shown) which is electrically or manually opened and closed to measure the pressure in the atmosphere gas space as a pressure gauge to open the discharge passage when the measured pressure reaches a set pressure. do.

Referring to the operation and effect of the present invention having the above configuration is as follows.

In the case of casting austenitic stainless steel as a twin roll sheet casting machine 100, an alloy containing 18% Cr-8% Ni, specifically called 304 stainless steel, which contains manganese (Mn) The melting temperature of this element is 1244 ℃, and when the temperature of molten steel decreases, it evaporates and is discharged as fume. In addition, 100% nitrogen was used as the non-oxidizing gas injected through the first and second gas supply ports 8 and 9 into the space in the bath surface cover 7. Of course, the non-oxidizing gas may be used as a mixture of nitrogen and argon or argon alone.

First, before the start of casting, each valve member of the outlet 10 installed in the bottom cover 7 is closed and the discharge flow path is blocked, and the first and second gas supply ports 8 and 9 are provided in the bottom surface cover ( 7) When non-oxidizing gas is supplied into the lower atmosphere gas space, the atmosphere gas space is filled with non-oxidizing gas.

Subsequently, casting is started to supply molten steel between the pair rolls 3 and 3a through the injection nozzle 2 of the tundish 1 to form the molten pool 5, whereby fumes are generated and together with the generated fumes. When the internal pressure of the atmosphere gas space is greater than the set reference pressure by the non-oxidizing gas supplied into the atmosphere gas space, the discharge port (block) is blocked because the valve member is opened by the detection signal of a pressure gauge (not shown) that senses this. The discharge flow path of 10) is opened.

At this time, a shielding curtain 11 is installed between the pair rolls 3 and 3a and the bottom surface cover 7, and is continuously supplied to the pair rolls 3 and 3a through the first gas supply port 8. The supply amount of the non-oxidizing gas is higher than the supply amount of the non-oxidizing gas supplied to the water surface side through the second gas supply port 9 so that the pressure at the central side of the molten metal pool 5 in which the outlet port is installed in the atmosphere gas space rather than the roll side is low. Since the gradient is formed, the fume in the atmosphere gas forms the gas flow that moves to the center portion of the molten pool 5 without moving to the roll side as shown by the arrow shown in FIG. It is exhausted to the outside through.

According to the present invention as described above, the gas supply amount of the first gas supply port is provided with a plurality of discharge ports on the water surface cover corresponding to the central portion of the molten pool, and supply the non-oxidizing gas to the roll side so that a pressure gradient is formed in the atmosphere gas space. By supplying more than the gas supply amount of the second gas supply port for supplying non-oxidizing gas to the water surface side, the fumes mixed with the atmospheric gas do not flow to the twin rolls (3) (3a) side, but to the discharge port (10) side installed near the injection nozzle (2). Since it is possible to actively prevent the fumes adsorbed on the roll surface by being induced outside, the solidification of the twin rolls can be made uniform by preventing the fumes having manganese or manganese oxide components from adsorbing on the roll surface.

In addition, solidification cracks occurring on the surface of the thin plate 20 to be cast due to uniform solidification of the roll are significantly reduced, and manganese and manganese oxides that hinder the solidification are removed, thereby further improving the cooling ability of the twin rolls, thereby increasing the casting speed. It can be increased by 10 to 15%.

In addition, the temperature distribution in the width direction of the thin plate to be cast becomes uniform, and the effect of remarkably improving the quality of the cast metal sheet is obtained.

Claims (4)

Pair rolls 3 and 3a which rotate in opposite directions to each other, edge dams 4 provided at both ends of the pair rolls 3 and 3a to form a molten pool 5, and an upper portion of the molten pool 5 The first and second gas supply ports 8 having a bottom surface cover 7 installed to form an atmosphere gas space therein, and supplying non-oxidizing gas to the double surface 3 and 3a and the side surface of the floor surface cover 7. (9), the shielding curtain (11) is provided to seal the atmosphere gas space in the pair roll (3) (3a) and the corresponding water surface cover (7) to pass the molten steel between the pair roll (3) (3a) to form a thin plate ( In the twin roll type sheet casting machine for casting 20), The plurality of discharge ports are provided on the water surface cover 7 so as to exhaust the fumes moved to the center of the molten metal pool 5 by the injection force of the non-oxidizing gas injected from the first and second gas supply ports 8 and 9. A fume discharge device of a twin roll sheet caster, characterized in that a plurality of (10) are mounted in a roll width direction. The method of claim 1, The first gas supply port 8 replaces oxygen that may be attached to the surface of the roll while the non-oxidizing gas injected therefrom touches the surface of the pair of rolls 3 and 3a sufficiently, and the generated fume is rolled. A fume discharge device of a twin roll sheet caster, characterized in that installed in close proximity to the pair of roll (3) (3a) so as not to be adsorbed on the surface. The method of claim 1, The second gas supply port 9 provides a pressure gradient in the atmosphere gas space in which the fume is generated so as to naturally induce the flow of the generated gas such as the fume and the gas to the center of the molten pool 5 on the injection nozzle 2 side. The fume discharge device of the twin roll type sheet caster, characterized in that the non-oxidizing gas is injected with a gas supply amount less than the gas supply amount of the first gas supply port (8) for supplying the non-oxidizing gas to the pair roll (3) (3a) side. The method of claim 1, Each outlet 10 is equipped with a valve member which is electrically or manually opened and closed to measure the pressure in the atmosphere gas space as a pressure gauge to open the discharge passage when the measured pressure reaches the set pressure. Fume discharge device for roll type sheet casting machine.