JPS61226157A - Method for continuous casting of molten metal - Google Patents

Abstract

PURPOSE:To improve the quality of an ingot by disposing molten metal level gages together with stoppers for controlling the flow of a molten metal and controlling the operation of the stoppers according to the preset curve of the molten metal surface. CONSTITUTION:Molten aluminum 4 is connected from a holding furnace 2 into a spout 6 and is conducted through a nozzle 8 into a water-cooled casting mold 10. The stopper 16 and nozzle stopper 18 are provided in the inlet and outlet of the spout 6. The level gages 20, 22 which detect the height of the molten metal 4 surfaces in the mold 10 and the spout 6 are disposed. The level gages 20, 22 output the height signals of the molten metal surfaces via a vertical variable resistor when floats move upward or downward. The stopper 18 is exactly inserted or removed by a positioning cylinder, etc. A controller 24 controls the height of the molten metal surface according to the preset curve of the molten metal surface. Since the adjustment of the cooling rate for the ingot is made possible by the above-mentioned method, the quality thereof is improved.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a continuous casting method for molten metal, and in particular to a continuous casting method that can improve the quality of the obtained ingot by controlling the height of the molten metal to an arbitrary position. Or it relates to a semi-continuous casting method.

(Prior art) Conventionally, in semi-continuous casting of metal ingots, such as aluminum ingots, the flow of molten metal has been in the order of furnace - gutter -> nozzle mold, and the casting procedure is as follows. ing.

That is, first, the gutter stopper is opened to guide the molten metal from the furnace into the gutter, and after the gutter is filled with the molten metal to a predetermined level, the nozzle stopper provided in the gutter is opened to introduce the molten metal into the gutter. The molten metal is poured into the mold through a nozzle. This molten metal is poured via a float stopper that is generally suspended from a gutter.

The float stopper is used to close the nozzle tip when the level of the molten metal reaches the nozzle tip, and to maintain this level near the nozzle tip.

The molten metal is first allowed to flow into a so-called mold, which is surrounded by a bottom plate and a mold set at the bottom of the mold.

Then, when the molten metal level rises in the mold and reaches the set level, the bottom plate is lowered at a predetermined speed, and thereafter the molten metal level is kept constant until the end of casting using the aforementioned float stopper. There is.

(Problem to be solved) By the way, in this continuous casting method of aluminum ingots, etc., it is necessary to control the surface curve at the initial stage of casting to improve the quality of the "fir tree structure" etc. that occurs at the early stage of casting. Although it is desired to adjust the cooling rate of the ingot, which causes defects, a practical and effective means to solve this problem has not yet been found.

For example, with the above-mentioned casting method, it is not possible to control the molten metal level to a desired position without moving the mold or gutter up and down, and even if such a method were adopted, it would be very expensive in terms of equipment. There are inherent problems that are difficult, and there is also the inherent problem that the cost of the equipment increases significantly.

(Solution Means) The present invention has been made to solve the problem against the background of the above circumstances, and is characterized by supplying molten metal to a predetermined mold. When continuously casting a predetermined ingot by continuously cooling and solidifying it, a stopper is disposed in a flow path for supplying molten metal into the mold and blocks or regulates the flow of the molten metal. a level meter that detects the level of the molten metal in the mold; and a control that receives a level level signal from the level meter and controls the operation of the stopper according to a preset level curve. A control device is provided so that the control device controls the operation of the stopper to control the amount of molten metal supplied into the mold, so that the height of the molten metal level can be changed according to the molten metal level curve. I made it.

(Specific Description of Configuration) First, FIG. 1 shows a simple configuration diagram of a semi-continuous casting method for aluminum ingots according to an example of the present invention. There, 2 is a holding furnace (or heat retention furnace) that holds molten aluminum 4. The molten aluminum 4 is guided from this holding furnace 2 into a gutter 6, and a nozzle 8 passes through the bottom of the gutter 6.
Through this, the mold is introduced into a conventional water-cooled cylindrical mold 10. Further, as is well known, the molten metal 4 supplied into the water-cooled mold 10 is
The mold is solidified by cooling from the inner wall surface of the mold 10 and by cooling water injected from the lower part of the mold, and then taken out from the mold 10. In other words, the molten metal column formed in the mold 10 is solidified by supplying the molten metal 4 from the nozzle 8, and the ingot 12 formed by the solidification is continuously taken out from the lower end of the mold by lowering the bottom plate 14. It is designed to be possible.

By the way, in the casting apparatus having such a structure, the flow of the molten metal 4 from the holding furnace 2 to the gutter 6 is blocked or regulated by the gutter stopper 16, and the flow of the molten metal 4 from the gutter 6 to the water-cooled mold 10 is passed through the nozzle 8. The flow of the molten metal 4 guided inside is
It is shut off or regulated by the nozzle stopper 18. Further, the level of the molten metal 4 in the mold 10 is measured by a float level meter 20, and similarly, the level of the molten metal 4 in the gutter 6 is measured by a float level meter. 22. Output signals corresponding to the heights of the hot water inside the molds 10 and in the gutter 6 detected by the float level meters 20 and 22 are sent to a controller (control device) 24, respectively.
In the controller 24, a controlled signal is output to the nozzle stopper 18 according to a preset hot water level curve, and the operation of the nozzle stopper 18 is controlled to achieve the desired hot water level. It controls the height. The operation of the gutter stopper 16 is controlled by a controller 24 based on an output signal according to the height of the hot water level in the gutter 6 detected by a float type level meter 22. When the molten metal level is controlled, the molten metal level height signal in the gutter is also used to know the amount of molten metal 4 supplied through the nozzle 8.

The nozzle stopper 18 whose operation is controlled by the controller 24 as described above is equipped with an appropriate driving means such as a pulse motor in order to insert and remove its tip into the opening of the nozzle 8. For the drive of 18,
A preferred method is to use a high-precision positioning cylinder, to insert and remove the nozzle stopper 18 using a mechanism as shown in FIG. will be adopted. Note that there are cases where a sliding nozzle type is more advantageous than a simple plug type for the gutter stopper 16, and in that case, a driving means using a positioning cylinder 26 or the like is suitable, and the nozzle stopper 18 is also similar. A suitable driving means will be suitably adopted.

In addition, as shown in FIG. 3, the float type level meters 20 and 22 used as level meters are connected to vertical variable resistors by raising and lowering a float 28 made of a refractory material with low specific gravity such as marinite. 30, the structure is such that a predetermined hot water level height signal is outputted, and instead of this vertical variable resistor 30, it is also possible to use a structure using an actuating transformer. Furthermore, it is also possible to use an eddy current following type level meter as shown in FIG. The height of the hot water level is determined by the output signal.

Note that the output from any level meter is controlled by the controller 24.
The A/D converter installed inside converts the liquid into a digital signal, and the controller 24 sends a predetermined output signal to the drive section of the nozzle stopper 18 in accordance with a control method based on a predetermined hot water level curve. It is.

Then, the controller 24 controls the nozzle stopper 1 as follows based on the input hot water level information.
8 operation control will be performed.

That is, for example, the hot water level curve (
When controlling the hot water level height h (broken line), the hot water level (solid line) that changes with time t is divided into time periods (T, ~T in the illustrated example).

5), the nozzle stopper 18 is activated and inserted into and removed from the nozzle 8 to control the amount of molten metal supplied into the mold IO so that the curve approximates the level of the target broken line. , and the hot water level height: h. This control calculates d h/d t based on the hot water level measured between each time division, constantly monitors the value, and adjusts the outlet temperature to maintain the predetermined slope value. Y is transmitted to the drive section of the nozzle stopper 18.

A part of the flowchart of the control performed within this controller 24 is shown in FIG.

There, the flow of control operations during the elapsed time: t from the start of pouring (To) to T1 is shown, and until t reaches TI, the temporal change rate of the hot water level height: d
Determine whether h/dt is the gradient value based on the set hot water level curve, and if dh/dt7! I(k
, a specified command is issued to the drive unit to operate the nozzle stopper 18 by a predetermined value (Y). Then, when t - T, the control from the next T to T3 is performed in the same way.

In addition, here, the operating value: Y is the diameter of the nozzle 8, the shape of the nozzle stopper 1B, the value of the melt level in the mold, the value of the melt level in the gutter, the model of the drive part of the nozzle 7 bar 18, the device dimensions, etc. This is the value determined by The start of pouring from the nozzle 8 is determined based on the gutter level signal from the float level 22 provided in the gutter 6.1. the first nozzle)
Operation value of 7 bar 18: Yo can be specified. Furthermore, the time interval for operating the stopper 18 can be continuous (=0.1 seconds), but it can also be intentionally set at intervals of several seconds in accordance with the response time of the hot water level. . In the control method according to the present invention, the near value error of the curve is reduced by increasing the number of time divisions.

Then, according to such a control method, the nozzle stopper 1
By controlling the operation in step 8, the amount of molten metal 4 supplied into the mold 10 can be controlled, and the height of the molten metal 4 can be freely changed according to a preset molten metal level curve. As a result, the rising part of the mold surface curve at the initial stage of casting, which was difficult in the past, can be well controlled, and the height of the mold surface can be changed even in the middle of casting, for example, when casting with low mold surface. The casting method can now be carried out advantageously.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, the initial molten metal level curve during casting can be freely controlled.
It has become possible to adjust the cooling rate of the ingot, which causes quality defects such as "fir tree texture" that occur in the early stages of casting, and to improve quality. It is possible to perform hot water level control (for example, low hot water level casting), and it also eliminates the need for float stoppers, which used to be done manually, and also automates work such as pulling out gutter stoppers, reducing man-hours. As a result, it has become possible to enjoy benefits such as those that can be achieved.

[Brief explanation of drawings]

FIG. 1 is a simple configuration diagram for explaining the present invention,
FIG. 2 is a perspective explanatory view showing an example of the drive mechanism of the nozzle stopper, FIGS. 3 and 4 are explanatory views showing different examples of level meters, and FIG. 6 is a graph showing an example of control over a curve, and FIG. 6 is a diagram showing a part of a flowchart of control performed in the control device. 2: Holding furnace 4 Ni molten aluminum 6: Gutter
8: Nozzle 10: Water-cooled mold 12: Ingot 14: Bottom plate 16: Gutter stopper 18: Nozzle stopper 20.22 = float type level gauge 24: Controller Applicant: Sumitomo Light Metal Industries, Ltd. Figure 1 Excerpt Figure 2 Figure IIB Elapsed time R(t) Procedural amendment (1 button October 30, 1985)

Claims (1)

[Claims] In continuously casting a predetermined ingot by supplying molten metal to a mold and letting it cool and solidify continuously,
A stopper disposed in a flow path for supplying molten metal into the mold to block or regulate the flow of the molten metal, a level meter to detect the height of the molten metal surface in the mold, and the level. and a control device that controls the operation of the stopper according to a preset hot water level curve in response to a hot water level height signal from the meter, and the control device controls the operation of the stopper to prevent melting into the mold. 1. A continuous casting method for molten metal, characterized in that the height of the molten metal can be changed according to the molten metal level curve by controlling the amount of metal supplied.