JP4263801B2 - Metal strip casting method and apparatus and twin roll casting apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal strip casting method and apparatus, and a twin roll casting apparatus, which are applied to cleaning a casting roll of a single roll casting apparatus and a twin roll casting apparatus.
[0002]
[Prior art]
In the case of a single roll casting apparatus, the molten metal is flowed to the upper part of the rotating cooling roll by a distributor such as an overflow weir and solidifies as a strip on the roll surface, which is pulled down to one side of the roll. In the case of a twin roll casting machine, molten metal is introduced into the roll gap of a pair of cooled horizontal casting rolls rotating in the mutual direction, the metal shell solidifies on the surface of the moving roll, and they are joined together by the roll gap. A solidified strip product is produced from the outlet. In this specification, the term “roll gap” refers to the entire region where the rolls are closest to each other. Molten metal can be introduced into the roll gap by a metal feeder and a metal feed nozzle located below the metal feeder and receiving a metal stream from the metal feeder and directing it to the roll gap.
[0003]
In order to prevent foreign matters such as metal oxides and slag from accumulating on the surface of the casting roll, a cleaning device that cleans the surface of the casting roll at a position away from the contact area between the casting roll and the molten metal is generally used. In the twin roll casting device, a cleaning device such as a brush or a cleaning belt is applied to the outer side in the longitudinal direction of the roll, and the roll surface can be continuously cleaned before reaching the position where the roll before the roll gap comes into contact with the molten metal. it can. Examples of cleaning devices that include brushes include Nippon Steel Corporation and Mitsubishi Heavy Industries, Ltd., 1991 Patent Publication No. 230849 and 1996 Patent Publication No. 29401, Applicants' United States Patent No. 5 307,861 and Australian Patent Application No. 24833/95 and U.S. Pat. No. 4,708,194 of Allied Corporation. Another type of on-site cleaning device that blows coarse particles onto the roll surface to adjust the surface of the roll, such as oxide removal, is the Kawasaki Steel Corporation's 1995 Patent Publication No. 75855, Amco Corp. (Armco Inc.) U.S. Pat. No. 5,651,413 and 1992 Utility Model Public Notice No. 21628 of Nippon Steel Corporation and Mitsubishi Heavy Industries, Ltd.
[0004]
[Problems to be solved by the invention]
However, even with such cleaning, certain surface defects, such as chatter marks, occasional lateral surface cracks, and eyebrow defects, remain in the as-cast strip. Currently, it is speculated that the major cause of such defects may be dust, particularly dust generated by roll cleaning brushes. This type of dust tends to accumulate on the various components of the casting apparatus including the brushed casting surface and the components placed directly above it. It has been found that as dust accumulates on these components, the accumulated dust can fall to the roll surface due to vibrations of the operation. It is presumed that components such as a reservoir seal header are a large source of dust falling on the roll surface. In particular, it has been found that dust tends to accumulate and stick to the lower part of the longitudinal end of the header. The accumulated dust tends to drop from the header end to the casting surface and be swept out to the interface between the molten metal and the casting surface, resulting in strip defects.
[0005]
Prior proposals to collect such foreign matter removed from the roll surface by the brush and dust produced in the cleaning process include providing a suction header type device that pulls the foreign matter away from the casting surface.
[0006]
However, these are not reliable. It has been found that dust accumulates and sticks to the longitudinal edges of these headers and the deposited dust tends to fall from the downstream edge to the casting surface.
[0007]
Further, since the conventional collecting device has a suction effect that can collect dust at a distance of about 50 mm, an excessive number of collecting nozzles are required to collect dust from a normal casting roll.
[0008]
In a casting apparatus having a 1500 mm long roll, an upward single row of 30 collection nozzles per roll is required.
[0009]
Furthermore, the collection nozzle becomes clogged with long-term use and becomes ineffective, which may exacerbate strip surface defects.
[0010]
Furthermore, the collection nozzle installation and maintenance costs tend to be expensive.
[0011]
The present invention provides an alternative cleaning technique that can achieve effective roll cleaning with a device that is very simple and robust and that can work reliably in harsh environments.
[0012]
[Means for Solving the Problems]
According to the present invention, the molten metal is supplied and brought into contact with the cooling surface of the rotating casting roll, the molten metal is solidified on the casting roll surface, the solidified metal is separated from the casting roll surface, and the roll rotation direction is determined. A brushing means is applied to the surface of the casting roll upstream from the position where the molten metal is brought into contact, and a blast of curtain-like gas flowing in the longitudinal direction along the roll is melted with the brushing means in the roll rotation direction. Foreign matter remaining on the surface of the casting roll after applying the brushing means toward the position between the metal contact position is swept away by gas blasting in the roll longitudinal direction from one end of the roll across the surface of the casting roll, and the molten metal is cast into the casting roll. is supplied to clean the foreign matter on the casting roll surfaces prior to contact with the surface, the metal strip casting method is provided .
[0013]
To a series of blast nozzles that are spaced apart in a line along the surface of the roll through the blast gas supply duct and are inclined in the direction along the length of the roll by a required angle from the radial direction with respect to the surface of the casting roll. It is preferable to establish a curtain through and to sweep out the roll surface with a foreign substance accompanying the gas flow along the roll .
[0014]
Preferably, foreign matter swept from the roll surface by the blasting can be collected at the other end of the roll .
[0015]
The gas blast can be at a sufficiently low pressure that it does not affect the pressure of the atmosphere above the molten metal .
[0016]
The present invention also comprises a casting roll,
Metal supply means for feeding molten metal to the casting roll surface;
Brushing means for brushing the casting roll surface upstream of the metal supply means in the roll rotation direction;
A blast of curtain-like gas flowing in the longitudinal direction along the roll with respect to the roll surface is directed to a position between the brushing means and the metal supply means in the roll rotation direction, and remains on the casting roll surface after brushing by the brushing means. It consists of gas blast nozzle means for sweeping out foreign matter by gas blast from one end of the casting roll surface in the longitudinal direction and cleaning the foreign matter on the casting roll surface before the molten metal is supplied to the roll surface by the metal supply means. A metal strip casting apparatus is provided .
[0017]
The gas blast nozzle means consists of a series of blast nozzles spaced in a line along the roll surface, each inclined from the radial direction to the casting roll surface by a required angle in a direction along the roll longitudinal direction. Is preferred .
[0018]
Preferably, the casting apparatus further comprises shroud means extending along the roll at the location of the gas blast nozzle means so that the gas blast nozzle means can blow gas blast into the shroud means, This foreign matter can be removed from the casting roll surface along with gas blasting .
[0019]
Furthermore, the present invention provides a pair of casting rolls forming a roll gap therebetween,
Metal supply means arranged above the gap between the casting rolls to feed the molten metal to the roll gap and onto the roll surface to form a casting pool;
Brushing means for brushing the surface of each casting roll upstream of the metal supply means in the rotation direction of each roll;
For each casting roll surface, a blast of gas in the form of a curtain flowing in the longitudinal direction along each roll is directed to a position between the brushing means and the metal supply means in the roll rotation direction, and casting is performed after brushing by the brushing means. From the gas blast nozzle means for sweeping out the foreign matter remaining on the roll surface by gas blasting from one end of the casting roll surface in the longitudinal direction and cleaning the foreign matter on the casting roll surface before the casting roll surface enters the casting pool A twin roll casting apparatus is provided .
[0020]
Gas blast nozzle means,
A series of blast nozzles spaced apart in a line along one casting roll surface, each inclined from the radial direction to the direction along the roll longitudinal direction by a required angle with respect to one casting roll surface;
A series of blast nozzles spaced apart in a line along the surface of the other casting roll and inclined with respect to the surface of the other casting roll in the direction along the length of the roll by a required angle from the radial direction. Is preferred .
[0021]
Preferably, the casting apparatus further includes a pair of shroud means extending one by one along each roll at the position of the gas blast nozzle means so that the gas blast nozzle means can blow gas blast into the shroud means. By doing so, the foreign substance on the roll surface can be accompanied by gas blasting and removed from the casting roll surface .
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.
[0032]
The present invention was born from the need to effectively clean a casting roll in a twin roll casting apparatus that continuously casts a steel strip. In such casting apparatus, the casting roll usually has a cast surface that is chrome plated, which can be smoothed and more usually textured based on the composition of the strip being cast. . Oxidation of the molten metal component during the casting process results in the roll casting surface being coated with a solid component such as a metal oxide. Typically, the coating can consist of a large proportion of various oxides such as Al ₂ O ₃ , MnO, SiO ₂ , FeO and small amounts of MnS and FeS. If this coating is not removed, the coating can dramatically affect the heat flux at the interface between the molten metal and the casting surface, resulting in localized peaks in the heat flux, which can result in casting defects. It has been found that effective continuous cleaning is required to maintain heat flux control, and it is necessary / desirable to prevent dust from accumulating on the cleaned casting surface and avoid casting defects.
[0033]
In an effort to develop an effective dust removal / minimization method, we have experimented with gas blasting to entrain typical oxide-coated dust from the test surface, resulting from such gas blasting at the test surface. The impact pressure was measured.
[0034]
Preliminary experiments were conducted to find out how fast air was needed to move the dust. Since it is difficult to obtain a large amount of roll oxide (particle diameter φ2 μm), several other types of dust were used. That is, aluminum filling (particle size: length 0.3-1 mm × thickness 0.1-0.3 mm) and sand (φ0.1 mm) were substituted. The particles were placed on a flat surface and air was blown horizontally over the dust to determine the air velocity at which the dust could not stay on the surface and was removed. A ratio of approximately 1 cc / 5S was found to be sufficient.
[0035]
Using a φ100 venturi supplied by a 1/8 ″ 500 kP air source, the minimum velocity of air from the venturi required to remove dust from the surface was found to be 5 m / S. Venturi up to 1100 mm However, only dust up to a distance of about 50 mm could be “sucked”. The theoretical speed required to remove very fine oxide dust is only 0.58 m / S.
[0036]
Surprisingly, a way has been found to easily solve the problem of dust accumulation in the casting zone of a twin roll casting apparatus, which includes our Australian patent application No. 24833/95 and US Pat. No. 5,807. , 861, a large amount of air is blown from one end of the roll to the other end by a mancooler type fan. This was attempted by using a 3000 L / S fan at the south position of the south roll S as shown in FIGS. 1, 2 and 3 and blowing air from west to east. A roll was used, a brush was used, and a side dam was used. Air velocity was measured at various points in the casting zone. The results are shown in FIG. 1, FIG. 2 and FIG. The transition piece was run online, a cold oxygen reading was taken, the reservoir purged nitrogen was turned on, and the cooler fan was turned off. The reading was 0.18% oxygen. Then, when the fan was turned on, the reading increased to 0.23% oxygen. It was also noted that the reservoir pressure during this trial was only 3 Pa, and that there was still 1 Pa in the reservoir pressure reading without the transition piece and without purification.
[0037]
When molten metal is placed in the reservoir, the reservoir pressure rises to approximately 8 Pa. Calculations show that in air at normal atmospheric conditions, a speed of 1 m / S causes a pressure of 0.5 Pa. Assuming that the maximum speed of measurement is 0.5 m / S in the fan reservoir, air will not enter the reservoir due to the cooler fan if there is molten metal.
[0038]
A dust collecting system that can be connected to the baghouse can be provided on the anti-fan side of the roll to enhance the dust removal effect of the preferred embodiment of the present invention.
[0039]
In these tests, the maximum pressure that could be generated by air blasting was 2.5 Pa, and the blasting pressure was up to 5 m / S.
[0040]
1, 2 and 3 show the results of the test, from the south side of the south roll S to the air velocity near the reservoir area caused by using a 3000 L / S capacity fan at the west end of the south roll S. Is displayed. The twin roll casting apparatus used in this test includes a roll cleaning brush 1 applied to each roll at a position away from the roll gap 32 (see FIGS. 5 and 6).
[0041]
FIG. 4 shows another embodiment of the present invention, and the cleaning brush is not shown. In this embodiment, the shroud 19 is applied to the side of the roll 11 to form a foreign matter removal chamber 21, in which foreign matter removal blast gas is blown from the blast nozzle 13 to the surface 14 of the roll 11. The foreign matter is scraped off from the surface 14 of the roll 11, and the dust is entrained in the blast gas curtain in the foreign matter removal chamber 21.
[0042]
The blast gas may be air, for example, or may be an inert gas such as nitrogen or argon.
[0043]
In the configuration shown in FIG. 4, the roll 11 is one of a casting roll of a single roll casting apparatus or a pair of rolls of a twin roll casting apparatus. In the latter case, the same foreign substance removing apparatus is applied to the other roll. Hit it. In practice, the blast gas needs to be in the form of an extended curtain that sweeps away in the longitudinal direction of the roll 11. This generally requires that a series of blast nozzles 13 produce an extended curtain that can be supplied with blast gas via separate blast gas supply ducts 12 connected to a common gas supply means. The curtain is formed by blowing a gas blast on the surface 14 of the roll 11 while inclining in a direction along the roll longitudinal direction by a required angle from the radial direction.
[0044]
5 to 7 show a twin roll casting apparatus comprising a pair of cast rolls 31 forming a roll gap 32, a molten metal casting reservoir 33 supported above the roll gap 32, and a solidified strip 34 being cast therefrom. The foreign substance removal apparatus of is shown. The casting pool 33 is made of molten metal supplied from a supply nozzle 35 and is formed by side dams or side plates 36.
[0045]
Each roll 31 includes a foreign substance removing device of the type shown in FIG. In this case, a series of blast nozzles 37 spaced apart along the roll 31 with an internal nozzle passage 38 (see FIGS. 6 and 7) shaped to provide a continuous curtain blast that the curtain blast sweeps along the roll 31. Produced. Blast gas is supplied to the blast nozzle 37 via individual blast gas supply ducts 39. The blast nozzle 37 provides gas blasting that sweeps the surface of the roll 31 with a foreign substance in the blast gas.
[0046]
Two sets of blast nozzles 37 are surrounded by a pair of shrouds 42 to form a foreign matter removal chamber 43 from which foreign material and scraped foreign matter are discharged at one end of the roll 31.
[0047]
In a typical twin roll casting apparatus, the casting roll 31 has a length of about 1,500 mm. This means that about 12 blast nozzles 37 spaced apart along each roll 31 are required to cover the roll width. The blast nozzle 37 can be arranged on a stand about 15 mm away from the surface of the casting roll 31. The gas blast speed should be about 27.5 m / s or less at the outlet from the blast nozzle 37 to avoid undue disturbance to the casting pool environment as described above with respect to FIG.
[0048]
The oxide scraped from the surface of the roll 31 is generally granular with a diameter of about 1 micron, and the gas velocity can be maintained at about 2.5 m / S if they are swept from the cleaned roll 31 surface.
[0049]
6 and 7 show the components of the preferred embodiment of the present invention in more detail. The gas blast curtain is produced by blowing gas from a blast nozzle 37 through a duct 44 disposed at one end of the roll 31. Since the internal nozzle passage 38 has a shape that is inclined from the radial direction of the roll 31 in a direction along the longitudinal direction of the roll 31 by a required angle, the inner nozzle passage 38 is swept from one end of the roll 31 to the other end from the opposite duct side end of the shroud 42. Create a gas blast curtain.
[0050]
The apparatus shown is simple and robust, and can operate reliably in the high temperature environment of a twin roll casting apparatus. Also, since the material scraped from the roll remains fully operational, it cannot land on the cleaned roll surface even if released into the environment as in a conventional brushing system. The operation of the device can be easily adapted and modified to provide a very effective cleaning under a range of casting conditions. However, this particular device is described merely as an example and can be modified in many ways. For example, the shroud of FIGS. 3, 4, 5 and 6 may be unnecessary depending on the embodiment. In the preferred embodiment, the roll cleaning brush is generally applied to the roll, and the roll foreign matter removing device of the present invention is applied to the downstream side of the roll cleaning brush with respect to the roll rotation direction. Accordingly, it is to be understood that the invention is in no way limited to the details of construction shown, and that many modifications and variations are possible within the scope of the invention.
[0051]
In the above-mentioned claims column and means for solving the problem, the expression “consisting of” means “including”, unless it is necessary to take another meaning in context. Is used in the sense that the feature can be associated with further features of the embodiment.
[0052]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably prevent foreign matters such as metal oxides and slag from accumulating on the surface of the casting roll, and it is possible to prevent the occurrence of strip surface defects. Can be played.
[Brief description of the drawings]
FIG. 1 is a plan view of a twin roll casting apparatus showing experimental results including measurement of pressure generated by gas blasting.
2 is an east side view of the casting apparatus of FIG. 1 and shows the results of gas blast pressure measurement experiments at various positions.
FIG. 3 is a west side view of the casting apparatus of FIG. 1, showing the results of gas blast pressure measurement experiments at various positions.
FIG. 4 schematically shows the operating principle of a device constructed according to a preferred embodiment of the invention.
FIG. 5 is a view showing a twin roll casting apparatus equipped with a cleaning device according to a preferred embodiment of the present invention.
6 is a plan view of the apparatus shown in FIG.
7 is a cross-sectional view taken along the line VII-VII in FIG.
[Explanation of symbols]
1 Roll cleaning brush (roll cleaning device)
DESCRIPTION OF SYMBOLS 11 Casting roll 12 Blast gas supply duct 13 Blast nozzle 19 Shroud 31 Cast roll 32 Roll gap 33 Casting reservoir 34 Solidification strip 35 Supply nozzle 37 Blast nozzle 39 Blast gas supply duct 42 Shroud

Claims (10)

Position where molten metal is supplied and brought into contact with the cooling surface of the rotating casting roll, the molten metal is solidified on the surface of the casting roll, the solidified metal is separated from the surface of the casting roll, and the molten metal is brought into contact with respect to the roll rotation direction. A brushing means is applied to the casting roll surface upstream of the roll surface, and a curtain-like gas blast flowing in the longitudinal direction along the roll is applied to the roll surface between the brushing means and the molten metal contact position in the roll rotation direction. The foreign matter remaining on the surface of the casting roll after applying the brushing means toward the position between them is swept away by gas blasting in the roll longitudinal direction from one end of the roll over the surface of the casting roll, and the molten metal is supplied onto the surface of the casting roll. A metal strip casting method in which foreign matter on the casting roll surface is cleaned before contact . To a series of blast nozzles that are spaced apart in a line along the surface of the roll through the blast gas supply duct and are inclined in the direction along the length of the roll by a required angle from the radial direction with respect to the surface of the casting roll. The metal strip casting method according to claim 1, wherein a curtain is established by passing through and a foreign substance is entrained in a gas flow along the roll to sweep out from the roll surface . The metal strip casting method according to claim 1 or 2 , wherein the foreign matter swept from the roll surface by the blasting is collected at the other end of the roll . The metal strip casting method according to any one of claims 1 to 3, wherein the gas blasting is at a sufficiently low pressure so as not to affect the pressure of the atmosphere above the molten metal . A casting roll;
Metal supply means for feeding molten metal to the casting roll surface;
Brushing means for brushing the casting roll surface upstream of the metal supply means in the roll rotation direction;
A blast of curtain-like gas flowing in the longitudinal direction along the roll with respect to the roll surface is directed to a position between the brushing means and the metal supply means in the roll rotation direction, and remains on the casting roll surface after brushing by the brushing means. It consists of gas blast nozzle means for sweeping out foreign matter by gas blast from one end of the casting roll surface in the longitudinal direction and cleaning the foreign matter on the casting roll surface before the molten metal is supplied to the roll surface by the metal supply means. , Metal strip casting equipment. 6. The gas blast nozzle means comprises a series of blast nozzles spaced in a line along the roll surface and each inclined relative to the casting roll surface from the radial direction in a direction along the roll longitudinal direction by a required angle. A metal strip casting apparatus according to claim 1. The casting apparatus is further provided with shroud means extending along the roll at the position of the gas blast nozzle means so that the gas blast nozzle means can blow gas blast into the shroud means, so that foreign matter on the roll surface can be removed. 7. The metal strip casting apparatus according to claim 6, wherein the metal strip casting apparatus is entrained by gas blasting and removed from the casting roll surface . A pair of casting rolls forming a roll gap therebetween;
Metal supply means arranged above the gap between the casting rolls to feed the molten metal to the roll gap and onto the roll surface to form a casting pool;
Brushing means for brushing the surface of each casting roll upstream of the metal supply means in the rotation direction of each roll;
For each casting roll surface, a blast of gas in the form of a curtain flowing in the longitudinal direction along each roll is directed to a position between the brushing means and the metal supply means in the roll rotation direction, and casting is performed after brushing by the brushing means. From the gas blast nozzle means for sweeping out the foreign matter remaining on the roll surface by gas blasting from one end of the casting roll surface in the longitudinal direction and cleaning the foreign matter on the casting roll surface before the casting roll surface enters the casting pool A twin roll casting machine. Gas blast nozzle means,
A series of blast nozzles spaced apart in a line along one casting roll surface, each inclined from the radial direction to the direction along the roll longitudinal direction by a required angle with respect to one casting roll surface;
9. A series of blast nozzles spaced apart in a line along the surface of the other casting roll and inclined with respect to the surface of the other casting roll from the radial direction by a required angle in a direction along the length of the roll. The twin roll casting apparatus described in 1 . The casting apparatus further comprises a pair of shroud means extending one by one along each roll at the position of the gas blast nozzle means so that the gas blast nozzle means can blow gas blast into the shroud means. The twin roll casting apparatus according to claim 8 or 9, wherein foreign matter on the roll surface is removed from the casting roll surface along with gas blasting .

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