JP2008161875A - Casting nozzle suitable for achieving cast product having excellent surface property, method for manufacturing cast product using the same, and magnesium alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a casting nozzle which is most suitable for achieving a cast product having excellent surface property, and also to provide a method for manufacturing a plate cast product using the same nozzle, and further to provide the cast product having excellent surface property manufactured by the same method. <P>SOLUTION: The casting nozzle is fixed in a molten metal reservoir for storing the molten metal of magnesium alloy or aluminum alloy, and supplies the molten metal from the molten metal reservoir to twin rolls for continuous casting. The casting nozzle is made of a material which contains calcium silicate as a main component, and contains at least 1% or more of carbon fiber or alumina fiber in the nozzle, and is coated with a BN coating layer. The chemical reaction of the nozzle with the molten metal active to the nozzle is suppressed by the BN coating layer. As a result, the cast product having excellent quality of appearance can be achieved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a casting nozzle that is fixed to a sump for storing molten metal in a continuous casting of a magnesium alloy or an aluminum alloy, and supplies the molten metal from the sump to a twin roll for continuous casting. The present invention relates to a method for producing a cast material using, and a cast material obtained from the casting method. In particular, the present invention relates to a casting nozzle that is optimal for obtaining a cast material having excellent surface properties, and relates to a method for producing a cast material using the nozzle and a magnesium alloy.

Continuous casting is one of the main processes of metal processing, and is to heat a metal material at a temperature higher than the melting point to make a molten metal, and to make a semi-finished product of a certain shape from the molten metal.
Generally, casting is a process in which a molten metal melted at a high temperature is poured into a mold and cooled to form a lump (ingot). To produce a product, it is necessary to reheat and then lump it again. However, with this continuous casting method, a semi-finished product can be made directly from molten metal without going through a cooling / bundling process, and it is widely used because of its excellent productivity and energy saving, and various improvements have been made. It was.
Among them, a twin roll continuous casting and rolling method in which a molten metal is continuously supplied between a pair of twin rolls (rolling rolls), the metal supplied by the rolls is cooled and solidified, and formed into a thin plate while rolling ( Hereinafter, the twin roll method) is known.

Forming an aluminum alloy or the like into an alloy plate by a twin roll method has been actively performed, and the obtained alloy plate has been widely used as a member of various electric products, a vehicle material, and the like. Under such circumstances, the lightest magnesium alloy among practical alloys has been attracting attention due to recent demands for weight reduction for improving the fuel efficiency of automobiles, etc.
However, since magnesium is more active than aluminum and easily reacts when hot metal melt is supplied to the roll, the nozzle material that serves as the pouring spout must be selected with a material and shape that does not cause any reaction. I must. Therefore, improvement of the nozzle for casting suitable for manufacture of the magnesium alloy and the aluminum alloy containing magnesium has been desired.

In order to continuously supply the molten metal to the movable mold composed of rolls and belts, it is performed through a casting nozzle fixed to a hot water reservoir for storing the molten metal.
Examples of such casting nozzles include those described in Patent Documents 1 to 4. In Patent Documents 1 and 2, a felt layer made of a ceramic fiber is provided at the tip of a casting nozzle, and a nozzle used for a single roll as a movable mold is described. Patent Document 3 relates to an integrated immersion nozzle, and describes an alumina-graphite material as a nozzle material. Patent Document 4 describes a nozzle using a carbon-based material or a metal material at the tip of the nozzle.
JP 63-101053 A Japanese Patent Laid-Open No. 5-318040 Japanese Patent Laid-Open No. 11-5146 JP 2006-15361 A

In continuous casting and rolling, ceramics such as silica (silicon oxide (SiO ₂ ) and alumina (aluminum oxide (Al ₂ O ₃ )) are generally used as a refractory having low thermal conductivity in the nozzle portion. In the case of ceramics, it has been known that when a highly active molten metal such as a magnesium alloy is cast, the dissolved metal reacts with and bonds with oxygen atoms in the nozzle to produce a product on the nozzle surface layer. The product is magnesium oxide produced by bonding with oxygen and does not re-dissolve, so if mixed into the molten metal, solidification becomes non-uniform. It degrades the surface quality of the material and adversely affects the durability of the nozzle itself.
In particular, with the recent expansion of application fields for magnesium alloy products, the level of quality required for the products has increased, and there has been an increasing demand for improvement in appearance quality in addition to weight reduction and corrosion resistance improvement. However, for such material reasons, it is difficult for the conventional nozzles to satisfy the requirements concerning the appearance quality in particular.

  The nozzles made of ceramic fibers described in Patent Documents 1 and 2 are excellent in heat resistance but relatively low in strength. Therefore, if the tip of the outer peripheral edge of the nozzle is placed in contact with the movable mold, it is consumed during casting. As a result, a gap is formed between the movable molds at the tip, and there is a case in which a molten metal leaks from the gap, that is, a so-called hot water leak occurs. The alumina of the nozzle material described in Patent Document 3 is an oxide of aluminum, and the oxygen atom of the nozzle material reacts with the molten metal in the same manner as the above oxide-based ceramic, and a product is generated on the nozzle surface layer. End up. In the nozzle described in Patent Document 4, a carbon-based material or a metal material is used at the tip, but the metal material portion may be deformed and worn in contact with a high-temperature molten metal, and a layer such as a ceramic fiber sheet is formed. Even if it is interposed, there is a possibility that the layers may be peeled off in a layer structure made of materials having greatly different coefficients of thermal expansion, elasticity, tensile strength and the like.

  The present invention has been made in view of the above circumstances, and provides an optimum casting nozzle for obtaining a casting material having excellent surface properties, a casting method of the casting material using the casting nozzle, and It aims at providing the cast material obtained by this manufacturing method.

As a result of intensive studies, the present inventors have found that the reaction with the molten metal can be largely suppressed by applying a BN coating to at least the nozzle surface layer that comes into contact with the molten metal. And in order to achieve said objective, this invention employ | adopted the following structures.
(1) The invention according to claim 1 is a nozzle suitable for continuous casting of a magnesium alloy or an aluminum alloy, and at least a portion of the nozzle that contacts the molten metal is coated with a BN coating.
(2) The invention according to claim 2 is a method for producing a cast material, characterized by continuously casting a magnesium alloy or aluminum alloy plate using the casting nozzle.
(3) The invention according to claim 3 is a magnesium alloy obtained by the production method according to (2) and having a corrosion rate of 1.0 mg / cm ² / day or less when sprayed with salt water.

  As described above, according to the present invention, a nozzle suitable for continuous casting of a magnesium alloy or an aluminum alloy is formed with a sufficient thickness of the BN coating on the inner surface of the nozzle at least in a portion that comes into contact with the molten metal. And the reaction with the active molten metal, and there is an effect that a cast material with good appearance quality can be obtained. Further, since the reaction between the nozzle and the molten metal is suppressed, the nozzle is hardly deteriorated, which leads to improvement in durability.

  In addition, according to the manufacturing method of continuously casting a magnesium alloy or aluminum alloy plate using the casting nozzle, casting with good appearance quality can be achieved by the effect of using the casting nozzle with BN coating on the inner surface of the nozzle. The manufacturing method which can manufacture a material can be provided.

Further, according to the magnesium alloy obtained by the above manufacturing method and having a corrosion rate of 1.0 mg / cm ² / day or less when sprayed with salt water, due to the effect of using a casting nozzle having a BN coating on the inner surface of the nozzle. Further, it is possible to provide a cast material having a good appearance quality in which the reaction between the nozzle surface layer and the active molten metal is suppressed.

The casting nozzle in the present invention is preferably used when continuously casting a metal such as a magnesium alloy or an aluminum alloy. Specifically, in a continuous casting apparatus, it is used as a member for supplying molten metal from a sump to a movable mold.
For the nozzle body, it is preferable to use a fire-resistant and tough material that does not deform and wear even with a high-temperature molten metal. For example, a material mainly composed of calcium silicate used as a heat insulating board can be used. Furthermore, the material which contains 1% or more of carbon fiber or an alumina fiber at least in the said nozzle body is mentioned.
The BN coating applied to the nozzle is dried at 80-250 ° C. and preferably has a thickness of more than 3 μm, more preferably 5 μm or more. The upper limit is economically 100 μm.

The specific configuration of the continuous casting machine is as follows: a melting furnace that melts metal to form a molten metal, a hot water reservoir (tundish or trough) that temporarily stores the molten metal from the melting furnace, and a space between the melting furnace and the hot water reservoir And a movable mold for casting the molten metal supplied from the hot water reservoir. The nozzle of the present invention is preferably arranged with one end fixed to the sump and the other end (tip) in contact with the movable mold. In addition, a hot water weir (side dam) may be provided that is disposed near the tip of the nozzle and more effectively prevents the molten metal from leaking between the tip of the outer peripheral edge of the nozzle and the movable mold.
The melting furnace includes a crucible for storing molten metal and a heating means disposed on the outer periphery of the crucible for melting metal. In order to maintain the temperature of the molten metal, it is preferable to provide a heating means on the outer periphery of the transfer rod or nozzle.

The movable mold is, for example, 1. 1. It consists of a pair of rolls represented by the twin roll method (twin roll method). 2. It consists of a pair of belts represented by the twin belt method (twin belt method). Examples include a combination of a plurality of rolls (wheels) represented by a single-wheel belt method (belt-and-wheel method) and a belt. In movable molds using these rolls and belts, it is easy to keep the mold temperature constant, and the surface in contact with the molten metal appears continuously, so the surface condition of the cast material is smooth and constant. Easy to hold. In particular, the movable mold has a configuration in which a pair of rolls rotating in different directions are arranged opposite to each other, that is, the above-described 1. In the case of the configuration represented by (2), in addition to high mold production accuracy, it is preferable because the position of the mold surface (surface that contacts the molten metal) is easily held constant.
In addition, since the surface in contact with the molten metal appears continuously with the rotation of the roll, the release agent is applied and the deposits are removed before the surface used for casting comes into contact with the molten metal again. Can be performed efficiently, and equipment for performing such operations as application and removal can be simplified.

In the present invention, the magnesium alloy includes not only magnesium containing an additive element (additive element and the balance consisting of magnesium and impurities) but also pure magnesium consisting of magnesium and impurities. As magnesium containing an additive element, for example, AZ type, AS type, AM type, ZK type and the like in the ASTM symbol can be used.
In the present invention, an aluminum alloy includes aluminum containing an additive element (additive element and the balance consisting of aluminum and impurities), as well as pure aluminum consisting of aluminum and impurities. As the aluminum containing the additive element, for example, those selected from 1000 series to 7000 series of JIS symbols can be used.
In addition, it can be used for continuous casting of composite materials composed of magnesium alloy and carbide, composite materials composed of magnesium alloy and oxide, composite materials composed of aluminum alloy and carbide, and composite materials composed of aluminum alloy and oxide. Can do.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic diagram of a continuous casting and rolling apparatus according to a first embodiment of the present invention, and FIG. 2 shows a nozzle, a rolling roll, a first molten metal surface detecting unit and a continuous casting and rolling apparatus shown in FIG. The schematic diagram explaining a 2nd molten metal surface detection part is shown.
In addition, these figures are for demonstrating the structure of a continuous casting rolling apparatus, and the magnitude | size of each part shown, thickness, a dimension, etc. differ from the dimensional relationship of an actual continuous casting rolling apparatus.
Also, among the components shown in FIG. 2, the same components as those shown in FIG. 1 are denoted by the same reference numerals as those in FIG.
The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  A continuous casting and rolling apparatus 1 shown in FIG. 1 melts a magnesium alloy to obtain a molten magnesium alloy M, and temporarily stores the molten magnesium alloy M obtained in the melting furnace 2 and supplies it to a rolling roll 3. A trough 4 and a pair of rolling rolls 3a and 3b for producing a magnesium alloy plate 15 by continuously casting and rolling the magnesium alloy molten metal M and the magnesium alloy molten metal M obtained in the melting furnace 2 are pumped into the trough 4 and transferred. A molten metal transfer system 5 for hot water and a molten metal level control means 6 for controlling the molten metal level H1 of the molten magnesium alloy M in the trough 4 are provided.

  The melting furnace 2 is a container having heating means, and the upper side is an open surface. This open surface is sealed with a lid 7 except for a part, and an ingot insertion port 9 for supplying a magnesium alloy ingot 8 as a raw material is formed in the lid 7. By having the ingot insertion port 9, the magnesium alloy ingot 8 can be supplied into the melting furnace 2 without removing the lid 7. The magnesium alloy ingot 8 is attached to the ingot supply means 10 and is supplied into the melting furnace 2 at a desired speed and quantity by the operation of the ingot supply means 10. The ingot insertion port 9 is hermetically sealed by a lid (not shown) after the ingot is inserted.

The melting furnace 2 is connected to a molten metal transfer system 5 for transferring the magnesium alloy molten metal M obtained in the melting furnace 2 into the trough 4.
The molten metal transfer system 5 includes a molten metal pump 11 and a supply pipe 12. A suction port (melt suction port) 11 a of the melt pump 11 is inserted into the magnesium alloy melt M in the melting furnace 2, and one end of a supply pipe 12 is connected to the discharge port 11 b of the melt pump 11. The other end of the supply pipe 12 is connected to the upper wall 13 of the trough 4. A heater unit 14 is disposed around the supply pipe 12. Thereby, solidification of the molten metal moving in the pipe 12 is prevented.
In the molten metal transfer system 5, when the operation of the molten metal pump 11 is turned on, the molten magnesium alloy M obtained in the melting furnace 2 is pumped into the molten metal pump 11 and introduced into the supply pipe 12. . The molten magnesium alloy M introduced into the supply pipe 12 is pumped to the trough 4 side and supplied into the trough 4.

In this embodiment, an inverter-controlled pump that gives energy to the molten metal by rotating the impeller in the casing is used as the molten metal pump 11. The inverter-controlled pump has a casing having a suction port and a discharge port, an impeller that is rotatably disposed in the casing, and a motor that rotationally drives the impeller, and detects hot water detected based on laser light. The molten metal level control means 6 controls based on the surface level H1, and the amount of molten metal supplied to the trough 4 is controlled by changing the rotation speed of the impeller.
The molten metal level control means 6 includes a first molten metal level detector 25, a second molten metal surface detector 26, a controller 33, and a molten metal pump 11. 2 Based on the molten metal level H1 detected by the molten metal level detection unit 26, the supply amount of the magnesium alloy molten metal M into the trough 4 by the molten metal pump 11 is controlled, and the molten metal level H1 in the trough 4 is the target hot water level. It is configured to be maintained in a range close to the surface level.
The molten metal pump 11 is not limited to an inverter-controlled pump, and may be another electric motor-driven pump, an air-driven pump, or the like.

  The height (molten surface level H1) of the upper surface (molten surface S) of the magnesium alloy molten metal M supplied into the trough 4 by the molten metal transfer system 5 is close to the target molten metal level by the molten metal level control means 6. Maintained in range. Thereby, the magnesium alloy molten metal M is supplied to the gap between the rolling rolls 3a and 3b with a stable supply pressure, and the magnesium alloy sheet can be manufactured stably. The hot water level control means 6 will be described later.

The trough 4 includes a housing portion 4a that houses the molten magnesium alloy M, and an introduction path 4b that communicates with the housing portion 4a and introduces the magnesium alloy molten metal M into a gap between the pair of rolling rolls 3a and 3b. .
The accommodating part 4a is a space whose height is higher than the target hot water surface level, and is configured by being hermetically surrounded by a wall part having heat resistance. Among these, the upper wall portion 13 is provided with a through hole 16 into which a later-described third support shaft 41 is inserted in an airtight manner. Further, the upper wall portion 13 is configured by a heat-resistant plate material 13a that is transparent to the laser beam in a region that overlaps the beam path of the laser beam irradiated by a laser irradiation unit 29 described later. As the heat-resistant plate material 13a having transparency, for example, various heat-resistant glasses are preferably used.
The introduction path 4b extends from a portion lower than the target hot water surface level of the housing portion 4a to a gap between the pair of rolling rolls 3a and 3b. That is, the introduction path 4b is configured such that the height is lower than the target hot water surface level, the width is substantially the same as the accommodating portion 4a, and is hermetically surrounded by a heat-resistant wall. Yes.

The feature of the present invention is that, in the nozzle 17 forming the introduction passage 4b, BN coating is applied to the inner surface of the nozzle at least at the portion that comes into contact with the molten metal. The BN coating applied to the nozzle 17 is dried at 80 to 250 ° C. and has a thickness of, for example, 5 μm or more.
By this BN coating, when the magnesium alloy melt M passes through the introduction path 4b, the reaction between the active magnesium alloy melt M and the inner surface layer of the nozzle 17 is suppressed, and a cast material having a good appearance quality can be obtained. . Further, in order to suppress the reaction between the nozzle 17 and the molten magnesium alloy M, the nozzle 17 is hardly deteriorated, leading to an improvement in durability.

In addition, a return pipe 18 for discharging the molten metal to overflow and returning it to the melting furnace 2 is connected to the storage section 4 of the trough 4 above the side wall on the melting furnace 2 side. A heater unit 19 is disposed around the return pipe 18. Thereby, solidification of the molten metal moving in the pipe 18 is prevented.
The heater units 14 and 19 disposed around the supply pipe 12 and the return pipe 18 preferably have a temperature control mechanism. Thereby, the temperature of the magnesium alloy molten metal M moving in the pipes 12 and 18 can be kept substantially constant, and the molten metal temperature can be prevented from being lowered and solidified during the transfer.
Moreover, it is preferable that the heater parts 14 and 19 can heat the supply pipe | tube 12 and the return pipe | tube 18 to the temperature of 250 degreeC or more. Thereby, solidification of the magnesium alloy molten metal M which moves in the pipes 12 and 18 can be reliably prevented.

  The trough 4 is provided with a movable weir 20a that is moved up and down so as to open and close at least a part of a connection opening (discharge port) 20 to which the return pipe 18 is connected. By moving the movable weir 20a up and down, the lower limit height of the opening area of the discharge port 20 (area not closed by the movable weir) is adjusted. And by setting this movable weir 20a to a position where the lower limit height substantially coincides with the target hot water surface level, the magnesium alloy molten metal M supplied in excess of the target hot water surface level into the trough 4 is supplied. Then, it can be discharged from the discharge port 20 and returned to the melting furnace 2 through the return pipe 18. As a result, the molten metal surface level H1 of the molten magnesium alloy M in the trough can be brought close to the target molten metal surface level. Note that the control of the hot water level H1 by this overflow discharge is low in accuracy. In this continuous casting and rolling apparatus 1, the molten metal level control means 6 further precisely controls the molten metal level H1 of the magnesium alloy molten metal M in the trough 4 so as to be the target molten metal level.

Each of the melting furnace 2, the trough 4, the supply pipe 12, and the return pipe 18 communicate with each other, and this communicated space is a sealed space.
Further, inert gas supply pipes 21, 22, 23, 24 are connected to the melting furnace 2, the trough 4, and the supply pipe 12, respectively, and the inert gas supply pipes 21, 22, 23, 24 are connected to the inert gas. A supply device is connected. The inert gas supplied from the inert gas supply device passes through the inert gas supply pipes 21, 22, 23, 24, and is supplied into the melting furnace 2, the trough 4, and the first supply pipe 12, It is filled with a closed space. Thereby, it can prevent that the magnesium alloy molten metal M in this sealed space is exposed to the atmosphere and oxidized.

As the inert gas, a gas containing sulfur hexafluoride such as a mixed gas of SF ₆ (sulfur hexafluoride) and N _{2 or} a mixed gas of SF ₆ and CO ₂ can be used. Sulfur hexafluoride is a gas with a large mass. When it comes into contact with the molten magnesium alloy, a reaction of 4Mg + SF ₆ → 3MgF ₂ + MgS occurs, and a stable reaction product (protective film) is formed on the surface of the molten magnesium alloy. As a result, the molten magnesium alloy is cut off from the atmosphere, its oxidation and combustion are suppressed, and the generation of magnesium vapor is suppressed, making it possible to stably manufacture the magnesium alloy plate.

The pair of rolling rolls 3a and 3b are arranged in parallel so as to have a predetermined gap between the outer peripheral surfaces, and the discharge port of the introduction path 4b of the trough 4 and the gap between the rolls 3a and 3b correspond to each other. It is installed. The molten magnesium alloy M introduced between the pair of rolling rolls 3a and 3b after passing through the introduction path 4b is continuously cast and rolled by passing between the rolls 3a and 3b without being pressurized. It is formed on an alloy plate. The thickness of the magnesium alloy plate is preferably 2.5 to 7 mm.
A release agent spray 46 and a temperature sensor 47 are disposed in the vicinity of the rolling rolls 3a and 3b. The release agent spray 46 sprays and supplies the release agent to the outer peripheral surfaces of the rolling rolls 3a and 3b. Thereby, the mold release property with respect to the magnesium alloy plate of the outer peripheral surface of rolling roll 3a, 3b can be supplemented as needed. Moreover, the temperature sensor 47 detects the temperature of the outer peripheral surface of the rolling roll 3a. By detecting the temperature of the outer peripheral surface of the rolling roll 3a by the temperature sensor 47 and controlling the temperature condition based on the detected temperature, the conditions for continuous casting and rolling by the rolling rolls 3a and 3b can be stabilized.

<Manufacturing method of cast material>
The continuous casting method of the present invention will be described by taking the case of using the continuous casting apparatus shown in FIG. 1 as an example.
First, a magnesium alloy ingot 8 is prepared.
The magnesium alloy ingot 8 contains magnesium as a main constituent element and various metals added thereto.
Examples of the metal to be added include Al, Zn, Mn and the like, and one of them may be added, or two or more of them may be added.

Al is preferably added in the range of 1 to 6.5%, and more preferably in the range of 2 to 4%. Al is positively added for the purpose of improving mechanical properties such as castability and strength, and corrosion resistance. However, if the amount of Al exceeds 6.5%, workability in the rolling process decreases. To do. Moreover, if the addition amount of Al is less than 1%, sufficient castability, strength and corrosion resistance cannot be obtained.
Zn is preferably added in the range of 0.2 to 2.0%. Zn, like Al, contributes to improvement of mechanical properties such as castability and strength. However, if the added amount of Zn exceeds 2.0%, castability deteriorates. Further, if the added amount of Zn is less than 0.2%, the strength may decrease, and as a result, the press formability may decrease.
Mn is preferably added in the range of 0.1 to 0.5%. Mn has an effect of alleviating the influence of elements that lower the corrosion resistance. That is, by adding Mn, the influence of Fe, which is an impurity element that lowers the corrosion resistance, can be mitigated. And especially by adding in said range, the effect can be exhibited most, and when it exceeds 0.5%, a coarse intermetallic compound will produce | generate at the time of continuous casting rolling, and rolling property will deteriorate.

Next, the magnesium alloy ingot 8 is supplied into the melting furnace 2 from the ingot insertion port 9.
The magnesium alloy ingot 8 supplied into the melting furnace 2 is melted in the melting furnace 2 to become a magnesium alloy molten metal M. The magnesium alloy molten metal M is transferred into the trough 4 at a predetermined supply rate by the molten metal transfer system 5.
At this time, when the molten metal is supplied into the trough 4 in an amount larger than the amount of molten metal at the target molten metal surface level, the excess magnesium alloy molten metal M is discharged from the discharge port 20 and discharged to the return pipe 18. And then returned to the melting furnace 2. Therefore, by such a return path, the molten metal level H1 of the magnesium alloy molten metal M of the accommodating portion 4a of the trough 4 is maintained so as to substantially coincide with the target molten metal level.

  The molten magnesium alloy M in the trough 4 passes through the introduction path 4b, is supplied to the gap between the pair of rolling rolls 3a and 3b, and is continuously cast and rolled between the rolling rolls 3a and 3b. At this time, the molten metal level H1 of the accommodating portion 4a of the trough 4 is substantially coincident with the target molten metal level, so that the magnesium alloy molten metal is supplied to the pair of rolling rolls 3a and 3b at an appropriate supply pressure. A board can be manufactured stably.

  As described above, in the continuous casting and rolling apparatus 1, the detection value of the first molten metal surface detection unit that detects the molten metal surface S by capturing the reflected image of the laser light L reflected from the molten metal surface S is used to detect the inside of the trough 4. The molten metal supply amount to the trough 4 by the molten metal transfer system 5 is controlled so that the difference between the molten metal level H1 and the target molten metal level is eliminated. Here, since the detection of the molten metal surface S by the first molten metal surface detection unit 25 using the laser light L has high accuracy, by using this, the molten metal surface level of the magnesium alloy molten metal M in the trough 4 is determined. It is possible to control with high accuracy within a range close to the surface level. Thereby, the supply pressure of the magnesium alloy molten metal M supplied between the rolling rolls 3a and 3b can be accurately maintained at an appropriate value, and the magnesium alloy plate 15 can be obtained stably.

  In addition, when continuously casting and rolling a magnesium alloy, the activity of the molten magnesium alloy M is very high, so a film or dross is formed on the surface, which may affect the detection of the molten metal surface S using laser light. In this continuous casting and rolling apparatus 1, the second molten metal surface detection unit 26 that indirectly detects the molten metal surface S by the vertical movement of the float 42 disposed on the surface of the molten magnesium alloy M is used in combination. When it is determined that the control amount obtained based on the detection value of the first molten metal level detection unit 25 is an error, the molten metal transfer is performed according to the control amount calculated based on the detection value of the second molten metal level detection unit 26. System 5 is controlled. Therefore, even when a film or dross is formed on the surface of the molten metal by operating for a long time, the molten metal level H1 of the magnesium alloy molten metal M in the trough 4 is continuously controlled so as to become the target molten metal level. can do.

In addition, in the said embodiment, each process of each part which comprises a continuous casting rolling apparatus, and a continuous casting rolling method is an example, Comprising: It can change suitably in the range which does not deviate from the scope of the present invention.
For example, instead of floating the float on the molten metal surface using a balance unit, a float having a lighter specific gravity and fire resistance than the molten magnesium alloy is directly floated on the molten metal surface. You may make it detect the fluctuation | variation of the hot_water | molten_metal surface by imaging with a part. Thereby, the structure of a 2nd molten metal surface detection part can be simplified.

Hereinafter, the present invention will be described in more detail by way of examples.
Using the continuous casting and rolling apparatus shown in FIG. 1, a magnesium alloy plate was manufactured with a plate thickness set to 5.4 mm.
As for the composition of the magnesium alloy, Al is 3.0%, Zn is 0.9%, Mn is 0.32%, and the balance is Mg.
Further, during the operation of the apparatus, 2% SF 6 + CO ₂ was introduced as an inert gas into the melting furnace, the supply pipe and the trough at a flow rate of 5 L / min.
Moreover, the scale used what was attached | subjected to the scale at intervals of 5 mm in the range from 42 mm of the target hot-water surface level to +/- 15mm.

The obtained magnesium alloy plate had a uniform quality, and it was confirmed that the magnesium alloy plate can be stably produced by this continuous casting and rolling apparatus. Compared to the case where a nozzle without BN coating was used, the metallic luster was strong and the appearance quality was excellent.
In addition, as a result of comparing the inner surface of the nozzle after continuous rolling casting, a black product was generated on the entire surface from the rolling roll side to the trough side in the nozzle without the BN coating, whereas a BN coating with a thickness of 10 μm was applied. The produced nozzle produced almost no product.
As a result of the EPMA surface analysis of the cross section of the nozzle used, the formation of magnesium oxide and carbon was observed on the nozzle inner surface layer for the nozzle without the BN coating, whereas the nozzle with the BN coating was oxidized with magnesium. Production and carbon generation were also suppressed.
Furthermore, in the 5% salt spray test, the sample using the nozzle with BN coating (no polishing, as cast) had a corrosion rate of 0.56 mg / cm ² / day, whereas the nozzle without BN coating. The sample using was 1.2 mg / cm ² / day.

  The casting nozzle in the present invention is preferably used as a member for supplying molten metal from a sump to a movable mold when performing continuous casting of a magnesium alloy or an aluminum alloy. Moreover, the manufacturing method of the cast material in this invention is optimal for obtaining the cast material which is excellent in surface property. Furthermore, the cast material obtained by this manufacturing method can be used as a secondary processed material such as rolling.

Drawing 1 is a mimetic diagram showing one embodiment of a continuous casting rolling device. FIG. 2 is a schematic diagram illustrating a nozzle, a rolling roll, a first molten metal surface detecting unit, and a second molten metal surface detecting unit included in the continuous casting and rolling apparatus illustrated in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Continuous casting rolling apparatus 2 Melting furnace 3 Rolling roll 4 Trough 4a Accommodating part 4b Introduction path 5 Molten metal transfer system 6 Molten surface level control means 7 Lid 8 Magnesium alloy ingot 9 Ingot insertion port 10 Ingot insertion means 11 Molten metal pump 11a Inlet 11b Discharge port 12 Supply pipe 13 Wall part 14, 19 Heater part 15 Magnesium alloy plate 16 Through port 17 Nozzle 18 Return pipe 20 Connection opening 20a Movable weirs 21, 22, 23, 24 Inert gas supply pipe 25 First hot water surface detection Unit 26 Second hot water surface detection unit 33 Control unit 34 Balance unit 39 First support shaft 40 Second support shaft 41 Third support shaft 42 Float 43 Weight 44 Scale 45 Scale 46 Release agent 47 Temperature sensor M Magnesium alloy molten metal H1 hot water Surface level S

Claims (3)

  A nozzle suitable for continuous casting of a magnesium alloy or an aluminum alloy, wherein a BN coating is applied to the inner surface of the nozzle at least in a portion that comes into contact with the molten metal.   2. A method for producing a cast material, wherein the nozzle according to claim 1 is used to continuously cast a magnesium alloy or aluminum alloy plate. A magnesium alloy obtained by the method according to claim 2 and having a corrosion rate of 1.0 mg / cm ² / day or less when sprayed with salt water.

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