JPH09285860A - Tilting type automatic molten metal pouring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of the quality of a product in advance by pouring a molten metal in a molding frame, tilting a ladle backward in the opposite direction to the pouring direction, and damping the vibration of the surface of the molten metal in the ladle to correctly control the molten metal pouring. SOLUTION: In an automatic molten metal pouring equipment 1, the molten metal in a ladle 2 is poured from a tapping port 3 to a down gate Mo of a molding frame 4 by tilting the ladle 2 clockwise around the axis O of revolution by a driving means 9. When the molten metal equivalent to one mold is poured, the ladle 2 is tilted backward at the maximum speed counterclockwise around the axis O of revolution by the driving means 9 in the opposite direction to the pouring direction, and when the ladle reaches the position where the molten metal is not spilled from the tapping part 3, the backward tiltation is stopped to smoothly perform the pouring cutting. The angle of backward tiltation is normally about 110 deg.. The residual vibration of the molten metal in the ladle 2 is eliminated to solve the problem of the sloshing of the molten metal in tilting the ladle 2 backward. Deterioration of the quality of the product due to inclusion of air and slag can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a casting technique, and more particularly, it holds a molten metal such as molten iron or aluminum in a ladle for a predetermined amount and tilts the ladle to form a mold frame. The present invention relates to a tilt-type automatic pouring method for pouring molten metal. According to the present invention, there is provided a tilt-type automatic pouring method in which vibration of the molten metal in the ladle, particularly when the tilting operation is performed after the pouring is finished is quickly suppressed.

[0002]

2. Description of the Related Art In a tilting pouring method in which a ladle holding a molten metal is tilted to pour the molten metal, the ladle is tilted forward to pour the molten metal into a mold frame, and after the pouring is completed, the ladle is tilted at a predetermined angle. Tilt backwards and stop in preparation for the next pouring. If the backward tilting operation of the ladle is made faster than that of the forward tilting operation when pouring to shorten the pouring cycle time, the molten metal held in the ladle and the inner wall of the ladle will collide with each other. The surface vibrates (liquid level vibration: sloshing), and residual vibration occurs. If this sloshing is large, the molten metal may overflow from the ladle. Even if there is no such overflow, if the residual vibration is long, the residual vibration adversely affects the next pouring, and the pouring control cannot be performed well.

[0003]

In tilting pouring, accurate pouring of molten metal into the mold frame and control for making the pouring level at the pouring port into the mold frame constant are important.

However, as mentioned above, when the molten metal surface vibrates due to the backward tilting motion of the ladle, it adversely affects the accurate pouring control to the mold frame sprue and the molten metal level control in the mold frame. Rotational control of the ladle tilting is an important issue at present.

Further, if sloshing is large when the ladle is tilted backward, contamination (molten metal contamination) may occur due to the entrainment of air or slag, which may cause deterioration of quality.

[0006] In recent years, automation and speeding up of a pouring device have been promoted, but a pouring method and device that completely solve the problem of sloshing of the molten metal have not yet been put into practical use.

Therefore, an object of the present invention is to quickly perform the backward tilting operation of the ladle in the tilting pouring method, eliminate residual vibration of the molten metal in the ladle, and to slosh the molten metal during the backward tilting operation of the ladle. It completely solves the problem, the molten metal overflows from the ladle, or does not adversely affect the accurate pouring control to the mold frame spout and the level control of the molten metal in the mold frame. It is an object of the present invention to provide a tilt-type automatic pouring method in which deterioration of the product quality caused by contamination (molten metal contamination) due to inclusion of slag is prevented.

[0008]

The above object can be achieved by the tilting automatic pouring method according to the present invention. In summary, the present invention, in a pouring method of pouring into a mold frame by tilting a ladle holding a metal melt, after pouring into the mold frame, the ladle is When tilting backward in the opposite direction, the tilting automatic pouring method is characterized in that the melt surface vibration of the molten metal in the ladle is damped by accelerating and decelerating after ΔT time has elapsed after the tilting of the ladle has started. Is.

According to one embodiment of the present invention, the ladle performs a backward tilting motion at a rotational acceleration (a) = αsin ωt (ω is a rotational angular frequency of the ladle), and after the backward tilting starts, ΔT In time, the ladle further has a rotational acceleration (b) = Kαsin ω (t− △
T) is added. The rotational acceleration (a) = α sin ωt
In order to control the tilt angle to be the same as the predetermined tilt angle achieved by one cycle and to suppress the vibration, the ladle has a rotational acceleration (a) = (α / (1 + K)) sin ωt (ω is The tilting operation is performed by the rotation angle frequency of the ladle, and the rotation acceleration (b) = (Kα
/ (1 + K)) sin ω (t−ΔT) is added.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The tilting automatic pouring method according to the present invention will now be described in more detail with reference to the drawings. FIG. 1 shows an embodiment of an automatic pouring device for carrying out the tilt-type automatic pouring method according to the present invention.

The automatic pouring device 1 has a ladle 2.
The ladle 2 is tiltable around a rotation center axis O passing near the tap hole 3. In the present embodiment, the ladle 2 is a so-called fan-shaped ladle having a fan-shaped cross section, and the rotation center axis O
Is constructed so as to pass through the main part of the fan shape.

Further, the ladle 2 is driven by a motor 7 such as a servomotor and a belt drive through a sector gear 4 fixed to the ladle 2 and a pinion gear 6 provided on a frame 5 supporting the ladle. It is tilted by the driving means 9 provided with the member 8.

By rotating and tilting the ladle 2 in the clockwise direction in FIG. 1 around the rotation center axis O by the driving means 9, the molten metal in the ladle 2 is discharged from the tap hole 3 into the mold frame M. It is poured into the sprue M _o . After pouring one mold,
The ladle 2 is tilted backward by the drive means 9 around the rotation center axis O in the direction opposite to that at the time of pouring, and counterclockwise in FIG. 1 at the maximum speed so that the hot water can be drained smoothly. Then, when a certain angle (a position where the molten metal does not spill from the tap hole 3) is reached, the tilting operation is stopped thereafter. Normally, the backward tilt angle is about 10 °.

When the next mold M frame is installed at a predetermined position along the pouring line L _P in accordance with the continuous tact cycle, the pouring work is repeated according to the above-mentioned procedure. Such pouring work is continuously performed until the molten metal in the ladle 2 is equal to or less than one mold. To supply the molten metal to the ladle 2, the dolly 11 on which the frame 5 supporting the ladle 2 is mounted is moved rearward on the rail 12, and the water is appropriately supplied from a water heater (not shown) located there. To be done.

In the casting system having the above-mentioned structure, the automatic pouring apparatus 1 has the vibration of the molten metal held in the ladle 2 when the ladle 2 is tilted by the drive means 9 around the rotation center axis O, That is, sloshing occurs.

The present invention suppresses the above sloshing by controlling the servomotor 7 of the ladle driving means 9.

First, the basic principle of vibration damping, which is the basis of the present invention, will be described. As described above, since the liquid level vibration in the ladle is considered to occur when the ladle 2 is tilted backward,
The liquid level vibration at the time of tilting backward will be described.

Further, according to the results of the research and experiment conducted by the present inventors, it is assumed that the liquid level in the ladle 2 when the ladle is tilted backward does not have liquid level vibration when the ladle tilt is started. Under hot water conditions, it vibrates while keeping a straight line, and the liquid level vibration is 1
It turns out that the next mode is dominant. Therefore, the liquid surface vibration was modeled for the first-order mode.

As shown in FIG. 1, FIG. 2 is a schematic diagram of a pouring device having a structure in which the center of rotation of the ladle is provided at the pouring port of the ladle. Sloshing in the ladle is a single pendulum type model. It is a conceptual diagram of a sloshing model at the time of capturing. FIG.
The ladle shown in (1) is not the fan-shaped ladle shown in FIG. 1 but has a cylindrical shape. However, damping of sloshing can be similarly considered regardless of the shape of the ladle.

When the ladle is tilted by η around the center of rotation O _r of the ladle, the balance of the moments about the fulcrum O of the pendulum is

[0021]

[Equation 1] Becomes

[0022] Here, eta: ladle tilting angle [psi: melt vibration angle O _r: ladle rotation center O _g: gravity center of the melt O: fulcrum of the pendulum D: from a ladle rotation center O _r to melt the centroid O _g Of the angle θ _g : angle formed by the line segment O _r O _g with respect to the horizontal line m: mass of molten metal c: equivalent viscosity coefficient l: equivalent pendulum length. Further, the liquid surface vibration angle ψ takes a variation from the initial angle θ _ini with the clockwise direction being positive.

In the above equation (1), J is the moment of inertia of the pendulum around the fulcrum O, and J = ml ² .
g is the gravitational acceleration.

Therefore, the left side of the above equation (1) is the inertial term, the first term of the right side is the viscous (damping) term, the second term of the right side is the gravity term, and the third term of the right side is the term of the vertical component of the external force due to the ladle rotation. , Right side 4th
The term is the horizontal component of the external force due to ladle rotation.

In the present invention, the backward tilt angle of the ladle is 0.174.
Since it is set to 5 rad (10 °), η can be considered to be sufficiently small. Therefore, when ψ is sufficiently small, the equation (1) is linearly approximated. At this time, D and θ _g can be regarded as constants, and in the third term on the right side of the equation (1),

[0026]

[Equation 2] If the third term is omitted, the equation (1) is represented by the following equation (2).

[0027]

(Equation 3)

Further, the transfer function G (s) is given by the following equation (3). Here, s is a Laplace operator.

[0029]

(Equation 4)

As described above, the liquid level vibration when the ladle is tilted backward can be expressed by a simple model such as equation (2). Therefore, use this model to suppress the liquid level vibration. You can

Generally, the transfer function G (s) of the target system
Is expressed by the second-order lag system shown in the following equation (4),
When an impulse-shaped input of magnitude 1 is applied at the initial time t ₀ , vibration as shown in FIG.

[0032]

(Equation 5) However, A: System gain ω _n : Natural angular frequency ζ: Damping ratio u (s): Input (rotational acceleration of the ladle in pouring) y (s): Output (in molten metal vibration of ladle in pouring) Size) s: Laplace operator

On the other hand, when an input impulse K for canceling the vibration of the solid line is applied at time t ₁ , a vibration like the dotted line is generated for the input. Therefore, FIG.
The vibration characteristics of the secondary system shown by the solid line in (A) are canceled by the vibration of the dotted line, resulting in the vibration as shown in FIG. 3 (B). That is, this damping method is a damping method by the input of the opposite phase.

In this damping method by the anti-phase input, the magnitude K of the anti-phase input and the timing time ΔT, that is, (t ₁ -t ₀ ) are important. In the case of a quadratic system, the solution of the above equation (4) is obtained by Laplace inverse transformation, and is represented by the following equation (5).

[0035]

(Equation 6) Using this equation (5), K and ΔT are obtained as follows.

[0036]

(Equation 7)

As mentioned above, the first impulse input 1
On the other hand, residual vibration can be completely eliminated by applying the input impulse K after the lapse of ΔT time. This method is called positive-cast (Presi-Cast) or pre-shape (Preshape) theory.

As described above, the pre-shape theory can be applied to the above equation (4), but the liquid surface vibration model of the present invention also includes the numerator (s) as shown in the above equation (3). ) Is a quadratic expression for. However, according to the theoretical analysis of the present inventors' research, it was found that the denominator of the equation (3) is dominant in the response of the system, and the pre-shape theory can be applied to the present invention as well.

However, in the above-mentioned vibration damping method, in reality, a large input is required to control with two impulse-shaped acceleration inputs, and since it is impulse-shaped, it is difficult to realize it, and the shock Since it is a dynamic input, it is easy to excite vibration of a higher-order mode that is not modeled, which is not realistic. In addition, in the actual pouring, if a sudden input such as impulse is applied, the molten metal in the ladle may be scattered, which is not preferable.

Furthermore, in the pouring control, the ladle must be tilted backward and stopped at a constant angle, which requires a negative acceleration.

Then, a rapid ladle rotation control method according to the present invention will be described which tilts the ladle backward by a desired angle and eliminates residual vibration.

Control of the backward tilt angle of the ladle after tilting: In order to prevent hot water draining and overflow, the ladle should not be completely returned after pouring, but a constant backward tilt angle, as described above. So up to 10
It is returned by °, for example, about 5 °. The acceleration / deceleration curve at that time is preferably a smooth sinusoidal curve rather than an impulse curve. At this time, it takes time to make this sinusoidal curve extremely smooth.
As shown in (A), the start-up, the fall is made smooth so as not to be discontinuous, and the predetermined target time (t _f )
Later, the rotational acceleration (a) having an acceleration / deceleration curve such that the target rotational angle (θ) is obtained is given. The rotation angular velocity (v) and the rotation angle (θ) at that time are shown in FIGS. 4B and 4C, respectively.

When the acceleration / deceleration curve is sinusoidal (that is, the rotational acceleration a = αsin ωt, ω is the rotational angular frequency of the ladle), given the target time t _f and the target rotational angle θ, the target time t _f Thus, each rotation frequency ω and α are obtained from the rotation angle θ.

Damping of molten metal: In the acceleration / deceleration curve of FIG. 4 (A), residual vibration occurs at the time t _f at the end of rotation of the ladle.
Therefore, the above-described pre-shape theory is applied to the acceleration / deceleration curve (FIG. 4A) as described in FIGS. 5 and 6.

That is, FIG. 5 (A) shows an acceleration / deceleration curve showing the rotational acceleration when the ladle is tilted backward, similar to that shown in FIG. 4 (A). This acceleration / deceleration curve is discretized at an appropriate sampling interval, for example, Δt = 0.01 seconds, as shown in FIG. 5B, due to a command from the computer.

Therefore, in order to eliminate the liquid vibration with respect to each of the impulse accelerations, according to the equation (6), Δ
After T seconds, add K input. That is, acceleration a _i (i =
Acceleration b _i (i = 1, 2, 3, ..., 10) is added after ΔT seconds for each of 1, 2, 3, ..., 10). This state is shown in FIG. Therefore, the acceleration / deceleration curve actually added to the ladle is as shown in FIG. 6 (B).

As a result, after t _f + ΔT seconds, the residual vibration is completely eliminated.

Reaching the target rotation angle in consideration of vibration suppression of the molten metal: As will be understood from the above, in order to obtain the target ladle rotation angle θ in damping the liquid level vibration of the molten metal in the ladle, When the rotational acceleration during the backward tilting motion of the pan is a = αsinωt, the rotational acceleration applied to the ladle after ΔT time to cancel the residual vibration is, as shown in FIG. 7, b = Kαs
inω (t−ΔT).

Therefore, in practice, an acceleration input of a = αsinωt + Kαsinω (t-ΔT) is added to the ladle.

However, in this case, the rotation angle (θ) of the tank is different between a = αsinωt and a = αsinωt + Kαsinω (t-ΔT).

That is, the rotation angle θ of the ladle has an acceleration of 2
It is found by integrating the number of times and time. (I) In the case of a = Asin ωt

[0052]

(Equation 8) (Ii) In the case of a = Asinωt + KAsinω (t-ΔT)

[0053]

[Equation 9]

Therefore, the rotation angle θ in the case of (ii) considering the residual vibration is (1 + K) times that in the case of (i).

Therefore, in the case of (ii) in which the residual vibration is taken into consideration, when it is desired to set the rotation angle θ to (α / ω) t _f ,

[0056]

(Equation 10) And it is sufficient. Therefore, a ′ = a + b, and the integral becomes (α / ω) t _f , and the control of the rotation angle is achieved. This state is shown in FIG.

Therefore, in practice, (1) so that the total time of t _f and ΔT becomes the target time,
Determine t _f and determine ω and α. However, ΔT is determined by the pouring method performed. (2) Add the acceleration input represented by the following formula.

[0058]

[Equation 11] (3) As a result, the target angle θ is achieved at the target time t _f , and residual vibration is eliminated after t _f + ΔT.

That is, the rotational acceleration (a) = α sin ω
In order to control the tilt angle to be the same as the predetermined tilt angle achieved by one cycle of t and to suppress the vibration, the ladle 2 has a rotational acceleration (a) = (α / (1 + K)) sin ωt After tilting backward, at the time ΔT after the start of tilting, the ladle 2 further has a rotational acceleration (b) = (Kα / (1 + K)) sin ω (t- △
T) may be added.

In carrying out the present invention described above, it is necessary to obtain the damping coefficient ζ and the natural angular frequency ω _n in the above equation (3) or equation (4). Can be obtained by Further, the damping coefficient ζ and the natural angular frequency ω _n can be obtained by computer calculation, for example, by a fluid analysis numerical simulator developed by the present inventors.

However, the damping coefficient ζ and the natural angular frequency ω _n
Is determined for each liquid level because it varies depending on the position of the molten metal in the ladle, that is, the liquid level. Therefore, the above equation (6) for damping the liquid level vibration is obtained for each liquid level.

[0062]

As described above, the tilt-type automatic pouring method of the present invention is a pouring method for pouring the molten metal into the mold frame by tilting the ladle holding the molten metal. After pouring, when the ladle is tilted backward in the opposite direction to that at the time of pouring, it accelerates / decelerates at time ΔT after the tilt of the ladle starts to be controlled to suppress the vibration of the molten metal in the ladle. Since it is configured to shake, the backward tilting operation of the ladle is performed quickly, and the residual vibration of the molten metal in the ladle is eliminated, and the problem of sloshing of the molten metal during the backward tilting operation of the ladle is completely solved. Does not overflow from the ladle, or does not adversely affect the accurate pouring control to the mold frame spout and the level control of the molten metal in the mold frame. Furthermore, contamination due to the entrainment of air or slag (molten metal contamination) ) Can prevent product quality deterioration due to

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an automatic pouring device for carrying out the tilting automatic pouring method of the present invention.

FIG. 2 is a conceptual diagram of a sloshing model when sloshing in a ladle is regarded as a single pendulum model.

FIG. 3 (A) is a diagram showing a vibration characteristic of a secondary system, and FIG. 3 (B) is a diagram showing a mode of vibration suppression by antiphase input.

FIG. 4 is a diagram showing a rotation angle, a rotation angular velocity, and a rotation acceleration in a backward tilting operation of a ladle.

FIG. 5 (A) shows an acceleration / deceleration curve applied to a ladle, and FIG. 5 (B) shows a state in which this acceleration / deceleration curve is discretized at predetermined time intervals Δt. Is.

FIG. 6 (A) is a view showing a state in which acceleration / deceleration is added for vibration removal at the time of backward tilting operation of the ladle, and FIG.
FIG. 6 is a diagram showing an acceleration / deceleration curve actually added to a ladle in consideration of vibration removal.

FIG. 7 is a diagram showing a backward tilt acceleration curve of a ladle and an additional acceleration curve for vibration removal during a backward tilt operation of the ladle.

FIG. 8 is a diagram for explaining rotation angle control in consideration of vibration damping during backward tilting of a ladle.

[Explanation of symbols]

 1 Tilt-type automatic pouring device 2 Ladle 3 Pouring mouth 9 Ladle driving means

Claims (3)

[Claims] 1. A pouring method for pouring a ladle holding a molten metal into a mold frame by tilting the ladle, wherein the ladle is moved in a direction opposite to that at the time of pouring after pouring the mold frame. When tilting backward, the tilting automatic pouring method is characterized by accelerating and decelerating after a predetermined time (ΔT) has elapsed since the start of tilting the ladle to suppress the vibration of the molten metal in the ladle. . 2. The ladle has a rotational acceleration (a) = αsin
ωt (ω is the rotation angle frequency of the ladle) is used for tilting backward, and the rotational acceleration (b) = Kαsin ω (t- △ T) is added to the ladle at time ΔT after the start of tilting backward. The tilting automatic pouring method according to claim 1. 3. The ladle has a rotational acceleration (a) = (α /
(1 + K)) sin ωt (where ω is the rotational frequency of the ladle), the tilting operation is performed, and the rotation acceleration (b) = (Kα / (1 + K )) Sin ω (t
-ΔT) is added.