JPS6333153A - Cast starting method for multi-connecting electromagnetic casting - Google Patents

Abstract

PURPOSE:To automate the casting start and to execute the stable casting by keeping molten metal in a casting spout at the prescribed height, supplying simultaneously the molten metal in molten metal accomodating recessed parts from each nozzle and controlling each nozzle opening as allowing to coincide each molten surface height till reaching to the opening height of recessed part. CONSTITUTION:Under control of a molten metal supplying controller 26 based on command of a main controller 24, the molten metal 6 is led to the casting spout 4 and level of the molten metal 6 in the spout 4 is ascended. Next, at the time of detecting to become to the setting level H by a sensor 28, all nozzles 8 is opened at the constant opening, to pour the molten metal 6 into each molten metal accomodating recessed part 32 on the base table 10 of EMC mode 2. And, when the molten 6 has gone round at the bottom face of recessed part 32, the molten metal supplying controller 22 controls the work of nozzle stoppers 18 based on level signal from sensors 30. And, the main controller 24 observes each EMC mold 2 and controls, so as to become to minimize each difference of the molten metal levels in EMC molds 2. Further, it controls to nearly coincide the height of molten surface in each EMC mold 2 till reaching to opening height of molten surface level in the molten metal accomodating recessed part 32.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a casting start method for multiple casting of metal by electromagnetic casting, particularly for multiple casting of aluminum or its alloy by electromagnetic casting. This provides an initial casting method.

(Prior art and its problems) Traditionally, in continuous casting (including semi-continuous casting; the same applies hereinafter) of metals such as aluminum or its alloys, multiple casters have generally been used for the purpose of improving productivity. The molds (casting units) are placed below the casting gutter,
A multiple casting method is used to continuously form multiple ingots at the same time by supplying a predetermined amount of molten metal to each of these molds from nozzles provided at the bottom of the casting trough, cooling and solidifying the metal. It has been adopted.

On the other hand, in a casting method using a normal cylindrical mold (DC casting), the molten metal is cooled by directly contacting the inner wall surface (mold surface) of the cylindrical mold, and then directly cooled by a jet of cooling water. Since solidification occurs when the mold surface is cooled, various surface defects such as seizure, cracking, sweating, hot cracking, etc., and alloy segregation occur. Electromagnetic casting methods that do not involve physical contact are attracting attention. This electromagnetic casting method was
As disclosed in Japanese Patent Publication No. 37267, Japanese Patent Publication No. 50-27807, etc., a predetermined molten metal column is held on a base using an electromagnetic field, and is continuously cooled and solidified to form the desired rod shape. Although this type of electromagnetic casting method uses a plurality of casting units to perform such casting, multiple castings are continuously performed using the above-mentioned multiple installation system. A method for obtaining lumps at the same time is being considered.

By the way, in such a continuous metal casting method, the supply of molten metal to the mold from the casting trough is described, for example, in Japanese Patent Application Laid-open No. 5
As shown in Japanese Patent No. 7-160556, this is done using a nozzle and a float, and the molten metal level in the mold is controlled by the buoyancy of the float. In this case, the level difference between each mold is It is difficult to make the molten metal level uniform in all molds because it is affected by the size of the float, variations in nozzle length, distortion of the gutter, etc., and as a result, there are various problems inherent in performing stable casting. It was.

For this reason, in JP-A-56-68570, each mold is equipped with a sensor that detects the level of the molten metal, and based on the detection, the amount of molten metal supplied to each mold is determined by the nozzle at the initial stage of pouring. It is controlled by 0N-OF operation with a constant opening degree, and halfway through it is shifted to PID control.
A method has been disclosed in which the level of molten metal in each mold is controlled by controlling it with a nozzle stopper, but this method can be applied directly to the molten metal level in each casting unit in multiple casting using the electromagnetic casting method described above. This method could not be applied to surface level control.

However, in the electromagnetic casting method, due to the specificity of its casting form, the level of the molten metal in each mold is simply controlled as described above, and it is the level of the molten metal during steady pouring work (
This is because a method that attempts to achieve uniformity until reaching height): h is insufficient. In other words, in the electromagnetic casting method, when the molten metal is continuously supplied and the molten metal level exceeds the depth of the molten metal storage recess (hlI) in the bottom, it enters the molten metal holding area by electromagnetic force (field), and at this stage, each If the molten metal level in a casting unit is different, the electromagnetic force to be supported must be changed, but it is extremely difficult and expensive to control the electromagnetic force individually in each casting unit, which is impractical. Moreover, problems such as destabilization of the initial shape of the obtained ingot may occur.

Regarding the method of controlling the level of the molten metal in the mold, Japanese Patent Application Laid-Open No. 57-195572 describes a method that can be applied to electromagnetic casting, in which the level in the mold during casting needs to be the same level in all molds. As a technology, a method has been disclosed in which each mold (casting unit) is equipped with a sensor that detects the level of the molten metal, and the level of the molten metal in each mold is controlled according to the detection by the sensor. According to the above, the level level bell of each mold at the start of casting is controlled separately by each mold, and the final level level for regular casting work is h(
Since the bases of all molds are lowered after reaching a certain level, the amount of molten metal in each mold differs from mold to mold during the initial stage of casting, which causes warping and distortion to vary from mold to mold, making casting unstable. There are still inherent problems such as.

In addition, in this method where the level of the hot water in each mold is detected and controlled using a sensor, the level of the hot water is the same for each mold when the bottom platform starts to descend.
The solidification time up to that point differs between molds located on the molten metal holding furnace side and molds located away from it, depending on the installation location of each mold with respect to the casting tank that leads the specified molten metal from a molten metal holding furnace such as a heat retention furnace. , there is a difference in the degree of solidification shell growth within the mold, which causes a difference in the degree of warping of the ingot as it solidifies, causing problems such as insufficient amount of molten metal. Because it will disappear.

(Solution Means) Here, the present invention has been made to solve the above-mentioned problems, and its characteristics are as follows: While holding a predetermined molten metal column on a base using an electromagnetic field, ,
A plurality of casting units that are designed to continuously cool and solidify the metal are arranged below the casting tank, and a predetermined molten metal is supplied to each casting unit from a nozzle provided at the bottom of the casting tank. In multiple electromagnetic casting, in which a plurality of ingots are continuously formed by casting each ingot, (a) the molten metal is guided from the molten metal holding furnace into the casting trough to reach a predetermined level. (b) When the height of the molten metal in the pouring gutter reaches the set height: H, the stoppers of each nozzle are operated to open the nozzles at the same time. (C
1) After the molten metal has sufficiently spread over the bottom surface of the molten metal storage recess in the bottom of each casting unit, detecting the height of the molten metal column rising in the molten metal storage recess, respectively,
(d) controlling the opening degree of the nozzle with a stopper so that the molten metal level heights substantially match each other by the time they reach the opening height of the molten metal storage recess; A process of raising the molten metal level of the molten metal column on the bottom of the casting unit at a uniform rising speed to a predetermined molten metal level height: h required during regular casting work,
e) After the molten metal level of the molten metal column in each casting unit reaches the predetermined height h, the bottom table is lowered while maintaining the height h to perform regular casting work. The present invention is configured to include a step of starting the process.

That is, in the present invention, in multi-unit electromagnetic casting, it is practically extremely difficult to raise the molten metal level in each casting unit to completely match the level from the start of casting. In the initial stage of casting, the depth of the molten metal storage recess provided on the top surface of the bottom of each casting unit into which a predetermined molten metal is poured: h,
Within the range of this depth h, the melt level is controlled so as to absorb the variation in the melt level on the bottom of each casting unit, and after exceeding this depth h, in other words, When the molten metal surface height exceeds the height of the opening of the molten metal storage recess, the molten metal surface height in each casting unit is controlled so that it is always the same. In other words, until it enters the holding space.

Since the level of the molten metal in each casting unit is equalized by the time the height exceeds This made it possible to stabilize the flow rate and start casting smoothly.

(Specific Description/Examples of Configuration) Hereinafter, in order to clarify the present invention more specifically, the configuration of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 schematically shows a casting apparatus having five 2MC (electromagnetic casting) molds, in which five 2MC molds 2 serve as casting units.
It is provided below the casting tank 4 and along it. A predetermined molten metal (aluminum or its alloy molten metal) 6 contained therein is supplied to the casting tank 4 from the direction of the arrow in the figure from a molten metal holding furnace such as a heat insulating furnace (not shown). ing.

In addition, each 2MC mold 2 is constructed by supplying molten metal 6 onto a bottom table 10 through a nozzle 8 provided at the bottom of a casting tank 4, and forming a molten metal column 1 on top of the nozzle 8, as is well known.
An annular coil 14 arranged around 2
have. By energizing this coil 14, an electromagnetic field (electromagnetic force) is generated, which holds the side surface and forms a molten metal column similar to the coil shape, while a cooling water jacket is placed on the side of the molten metal column. Cooling water is discharged from the molten metal column 16 to cool and solidify (solidify) the molten metal column 12, thereby forming the desired ingot, and this generated ingot is further transferred to the base 1.
It is designed so that it is continuously pulled downward by the descent of zero.

Then, each 2MC mold 2 of the molten metal 6 in the casting gutter 4
The supply of the nozzle onto the base 10 is controlled by the degree of opening of the nozzle 8 by each nozzle stopper 18, and the operation of such nozzle stopper 18 is performed by a drive device 20. -ing

Further, this drive device 20 is controlled by a pouring controller 22. Furthermore, each pouring controller 22 is connected to a main controller 24 and controlled by this main controller 24.

In addition, the main controller 24 is configured to start a melt discharge amount controller 26 that controls the discharge amount of the heat retention furnace in order to guide a predetermined molten metal 6 into the casting trough 4.
The discharge amount controller 26 is controlled according to the level signal 1 from the gutter level sensor 28 for detecting the molten metal level in the casting gutter 4, and when the level of the molten metal 6 in the gutter reaches a predetermined level: H. , actuating the nozzle stopper 18 by the driving device 20 through the pouring controller 22, and supplying the molten metal 6 in the casting gutter 4 onto the bottom stand 10 of each 2MC mold 2 through each nozzle 8,
The level of the molten metal 6 in the gutter is also kept constant.

Further, an in-mold level sensor 30 is provided to detect the level height of the molten metal column 12 formed on the bottom stand 10 of each 2MC mold 2, and an in-mold level signal from this sensor 30 is provided. is input to each pouring controller 22, and the degree of opening of the nozzle 8 by the nozzle stopper 18 is adjusted accordingly.

As the two sensors 28 and 30, a non-contact type such as an eddy current type, a capacitance type, an ultrasonic type, a laser type, or a contact type such as a float type may be used, and in particular, the latter in-mold level sensor 30, one having a sensitivity of ±1 or less is advantageously selected.

In such a multi-equipment electromagnetic casting apparatus, it is important to maintain the same level of molten metal in each EMC mold 2 at the start of casting and to start lowering the bottom table 10 in order to perform stable casting. Because it is important,
In the present invention, first, a predetermined amount of molten metal 6 is tapped out from a molten metal holding furnace such as a heat insulating furnace under the control of a tapping amount controller 26 based on a command from the main controller 24, and is poured into the casting trough 4. The molten metal 6 is guided and stored, thereby gradually increasing the level of the molten metal 6 in the gutter. At this time, the nozzles 8 for supplying molten metal to each 2MC mold 2 are in a fully closed state at the nozzle stopper 1st. The holding of the molten metal 6 in the casting gutter 4 continues until the height of the molten metal reaches a predetermined height: H, and the height of the molten metal is monitored by the level sensor 28 in the gutter. has been done.

Next, the gutter level sensor 28 reaches a predetermined setting level;
When the main controller 24M issues a command to the pouring controller 22 of each EMC mold based on the output signal,
The nozzle stoppers 18 for pouring molten metal into the molten metal are operated simultaneously to open all the nozzles 8 to a predetermined constant opening degree. In addition, when pouring the molten metal, as much as possible,
The amount of molten metal supplied above is made to be the same between each EMC mold 2. In addition, at this time, pouring iL: q
is expressed by the following formula (1).

However, g is gravity, S is the area of the nozzle 8, and α is a constant related to the opening degree and flow coefficient, and these S and α are variable by the controller 22.

In the present invention, when pouring molten metal into the base 10,
A dead zone is provided in which no particular control is performed from the initial stage until time t0, and the level of the molten metal is controlled after a sufficient pool of molten metal is formed in the molten metal storage recess 32 of the base 10. At the beginning of pouring water,
This is because it is easy to lose control due to turbulent flow, scattering, and disturbance of the hot water, and countermeasures are needed to deal with this, and it is also difficult to make the initial shape of the resulting ingot uniform. It is. And for that purpose, base 1
The depth of the molten metal storage recess 32 provided over the entire upper surface of 0 is increased to form a sufficient pool of molten metal, and then, within the range of such depth (%), each E
The aim was to equalize the level of the hot water between the MC molds.

That is, as shown in FIG. 2, at the beginning of pouring into the molten metal storage recess 32 provided at a sufficient depth hl in the base 10, [state a], each nozzle stopper 1
In a state where the opening degree of each nozzle 8 is kept constant, the molten metal 6 flows through each nozzle 8.
The molten metal is supplied to the MC mold 2 and stored in the molten metal storage recess 32 of each base 10.

Then, after a predetermined period of time (t6) has elapsed after the start of pouring, the pool of molten metal 6 in the molten metal storage recess 32 of each bottom stand 10 is formed on the bottom surface of the molten metal storage recess 32 as shown in (b). After the molten metal 6 is spread over the top and is in a sufficient state, level control of the molten metal level on the bottom stand 10 in each 2MC mold 2 is started. In addition, in this level control, the pouring controller 22 controls the operation of the nozzle stopper 18 by the driving device 20 based on the level signal from the in-mold level sensor 30, and the molten metal is supplied to the bottom stand 10 of each 2MC mold 2. This is done by controlling the amount of molten metal by a known PI control or PID control method.

Also, at this time, the main controller 24 monitors each 2MC mold 2 and performs control so that the level difference between the hot water levels in each 2MC mold 2 is minimized. Then, the molten metal surface level is at the opening height of the molten metal storage recess 32,
In other words, the heights of the molten metal in the respective 2MC molds 2 are controlled to be approximately the same until the depth hl) is reached, and as shown in FIG. 2(C), the opening of the molten metal recess 32 is When the height exceeds %), each 2M
In C mold 2, the molten metal level is always uniform.

In this way, in the present invention, the bottom base l of each 2MC mold 2 is
Depth of molten metal storage recess 32 at O.

) is made deep to absorb variations in the melt level in each 2MC mold 2 within the range of this hl, and for this reason, such a depth hl) is a constant value for subsequent continuous casting. It is desirable to set it to approximately the following formula (2) for the predetermined molten metal level height (h) required during the casting operation. In addition, this depth,)
If it is too shallow, the mold will enter the holding space by electromagnetic force before the level of the molten metal in each 2MC mold 2 is uniform, which tends to cause variations in the initial shape.On the other hand, if the depth I) is too deep, Although this will lead to stable casting, it will result in a deep bottom. In addition, the start time of controlling the hot water level in each 2MC mold 2 is as follows.
Although it varies depending on the amount of molten metal poured from the nozzle 8 and the size of the molten metal storage recess 32 in the base 10, generally, after the height of the molten metal in each molten metal storage recess 32 reaches 0.1 h or more. , level control will begin.

When the hot water level in each 2MC mold 2 exceeds the height of the base 10, the hot water level in each 2MC mold 2 is raised at a uniform rising speed along a predetermined hot water level rising curve. , the predetermined molten metal level height h (start level) required during regular pouring work can be reached. Such a uniform melt level rising speed in each 2MC mold 2 is achieved by each casting controller 22 based on the melt level level signal from each in-mold level sensor 30.
The main controller 24 performs PI or PID control, and the rising speed of the hot water level: V at that time is preferably controlled within the range of the following formula (3) % formula % (3) . Note that this rate of rise: V is expressed by the following formula (4): % formula %, where tI is the time when the hot water level reaches 1, and t2 is the time when it reaches h. If this V is too small, there will be a problem that the cooling from the bottom stand 10 will cause solidification to reach the surface of the molten metal, resulting in defects at the bottom of the ingot, while if . This makes it difficult to keep the speeds uniform.

In this way, after the molten metal level on the bottom stand 10 in each 2MC mold 2 reaches the continuous casting start level, which is the molten metal level height: h, this height: h
While holding the 2 MC molds 2, the bottom stands 10 of each 2MC mold 2 are lowered all at once, and normal casting work begins. will be formed.

Therefore, according to such a casting start method, the rising curve of the molten metal column 12 on the bottom table 10 in each 2MC mold 2 of the multiple electromagnetic casting apparatus is as shown in FIGS. 3(a) and 3(b). As can be seen, the initial stage of pouring from the start of pouring to t (1 hour) is considered to be a dead area where no level control is performed, so the level of the hot water in each 2MC mold 2 varies. By equalizing the melt level after 1° of time has elapsed, the melt level in each 2MC mold 2 is converged, and the depth of the molten metal storage recess 32 in the base 10, in other words, the opening height thereof is increased. , ), each 2MC
The level of the hot water in mold 2 becomes uniform,
After time t1 at which the height of hl has been reached, the level of the molten metal in each 2MC mold 2 is uniformly raised and reaches the desired pouring start level: h.

Thus, in each 2MC mold 2, the height of the molten metal column 12 formed on the base 10 reaches the holding space by electromagnetic force, in other words, the height of each 2MC mold 2 exceeds hlI. As a result, it is only necessary to generate an electromagnetic field under the same electrical conditions for each 2 MC mold 2, which makes it easy to control, and the initial shape of the ingot to be formed is stabilized. This enabled a smooth start of casting.

(Effects of the Invention) As is clear from the above description, according to the present invention, in the multiple electromagnetic casting apparatus, the level of the molten metal in each 2MC mold is effectively and advantageously made uniform, and solidification is based on this. The shell growth rate can also be made uniform, which makes it possible to start casting stably.Additionally, starting casting can be automated, making stable casting possible regardless of the skill level of the operator, which saves labor. In addition to achieving a cooling effect, it also became possible to freely select the optimal starting conditions according to the material, ingot size, and casting conditions (cooling conditions).

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing one of the multiple electromagnetic casting apparatuses suitably used in carrying out the present invention, and FIG.
), (b) and (c) are explanatory diagrams showing one state of the process in which a predetermined molten metal is supplied into the molten metal storage recess of the base, respectively, and FIGS. 3(a) and (b) These are graphs showing rise curves of the melt level in each 2MC mold, and explanatory diagrams showing the height of the molten metal column formed on the base plate corresponding to the graph. 2: 2MC mold 4: Casting tank 6; Molten metal 8: Nozzle 10: Bottom stand 12: Molten metal column 14: Coil 16: Cooling water jacket 18: Nozzle stop bar 20: Drive device 22: Pouring controller 24: Main controller 26: Output Molten metal flow controller 28: Gutter level sensor 30: Mold level sensor 32: Molten metal storage recess tI & castle

Claims (1)

[Claims] A plurality of casting units each configured to continuously cool and solidify a predetermined molten metal column while holding it on a base using an electromagnetic field are arranged below a casting gutter. In multi-equipment electromagnetic casting, in which a plurality of ingots are continuously formed by supplying a predetermined molten metal to each casting unit from a nozzle provided at the bottom of the casting trough and performing casting respectively. , a step of guiding the molten metal from the molten metal holding furnace into the casting trough and holding it until a set predetermined molten metal surface height: H; and a step in which the molten metal surface height in the casting trough reaches the set height. : When the temperature reaches H, the stoppers of the respective nozzles are activated to simultaneously open the respective nozzles, and the molten metal in the casting trough is poured into the molten metal receiving recess of the bottom of each casting unit through the respective nozzles. After the molten metal has sufficiently spread over the bottom surface of the molten metal storage recess in the bottom of each casting unit, the height of the molten metal column rising in the molten metal storage recess is detected, respectively. , a step of controlling the opening degree of the nozzle with a stopper so that the molten metal level heights substantially match each other by the time they reach the opening height of the molten metal storage recess; and each casting unit formed in this way. The process of raising the molten metal level of the molten metal column on the bottom stand at a uniform rising speed to a predetermined molten metal level height (h) required during regular pouring work, and After the surface of the molten metal column reaches the predetermined height h, lowering the base while maintaining the height h, and starting a regular casting operation. A method for starting casting in multi-equipment electromagnetic casting, characterized by: