JPS5841658A - Continuous casting method - Google Patents

Abstract

PURPOSE:To improve the corrosiveness of a horn applied with ultrasonic oscillations and to fine crystal grains in continuous casting of belt wheel type by evacuating the inside of a vessel immersed and inserted into charged molten metal to form a well and inserting said horn therein. CONSTITUTION:In the stage of continuous casting of belt wheel type for Al, etc., an inverted cup-like vessel 9 of sealed type formed of a heat insulating material is immersed and inserted into the upper part of a tundish 4. The inside of the vessel 9 is evacuated by operating an evacuating pump to form an evacuated chamber and to heighten the surface 5' of the molten metal upward to a constant level and to hold the same at said level, thereby forming a well 8. A horn 7 is inserted into the well 8, and ultrasonic oscillations are applied thereto. The metal 5 in the tundish 4 is charged into a mold consisting of a rotary wheel 1 for casting, endless belts 2, 2', and a pressing wheel 3, whereby the molten metal is cooled and solidified to form a cast ingot 6. By such method, the crystal grains of the cast ingot are fined stably for a long time without using any additive.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention continuously forms a mold using a rotating casting wheel having a concave I'# on its circumferential surface and an endless metal belt that runs on and contacts the circumferential surface of the rotating wheel. A belt-wheel type continuous casting method in which molten metal (hereinafter simply referred to as molten metal) is continuously injected into the mold and is cooled and solidified by cooling water applied to the circumferential surface of the mold to continuously obtain an ingot. In , improvement of the method of applying ultrasonic vibration to the solidification interface in the mold through the molten metal to refine the crystal grains of the ingot, specifically #'i
This invention relates to a continuous a manufacturing method that improves the corrosion resistance of the ultrasonic transmission horn that is immersed in the molten metal, and that allows stable application of ultrasonic waves over a long period of time.

Generally, the ingots produced by the belt-wheel continuous casting method are processed by pressing and other processes to become products, but defects on the surface of the ingots are magnified by processing and have a negative impact on the quality of the products. The defect Vi is more likely to occur and expand as the crystal grains near the surface of the ingot are larger.

Therefore, it is desirable that the vicinity of the surface of the ingot has a fine grain structure.

Various methods of controlling the ingot structure have been studied from this point of view. For example, in pure aluminum-medium aluminum alloys, Ti
A method of adding a refining agent such as B is often used.

However, the disadvantage of this method is that TiB2 is expensive, which increases the manufacturing cost of the product.

There is also a method in which ultrasonic vibrations are applied to the solidification interface to refine the solidification phase, that is, the crystal grains on the surface of the ingot and its vicinity, which are generated in the initial stage of casting. In order to apply vibrations, an ultra-YT wave transmission horn (hereinafter simply referred to as the horn) is immersed in hot water before the mold forming point. In this case, even if the horn is made of titanium or a titanium alloy, which has the best corrosion resistance against aluminum-based molten metal, it will be severely eroded, and according to the Ken9Y experiment conducted by the present inventors, the erosion rate is about 0+a+ per hour.

Therefore, even if the design and shape and dimensions of the horn are determined according to the resonant frequency of the sensor, the length of the horn will gradually become shorter and will eventually stop resonating. However, it has the disadvantage of losing its ability to refine grains. This also eroded the horn's financial strength; it also caused the melt to get into the bath water and contaminate the molten metal. and for a long period of time without using micronization additives such as i'in, etc.
, which made it possible to refine the structure of the ingot by using ultrasonic waves. When the horn is immersed in the flowing molten metal while vibrations are applied, the horn is severely corroded, and either of the above (the application of ultra-tt wave vibrations and the penetration into the flowing molten metal) It has been found that under condition F'''C, where no immersion (immersion) is present, there is no problem with horn erosion even after several tens of hours of immersion.

The present invention was made based on this knowledge, and the inside of an inverted cup-shaped container is immersed from both sides into the molten metal that is continuously injected into a mold. This achieves the desired purpose by forming a stationary or nearly stationary molten metal pool by holding the molten metal rising inside, and inserting a horn to which ultrasonic vibrations are applied into this molten metal pool. It is.

The present invention will be described in detail below using embodiments shown in the drawings.

In Fig. 1, (1) is a rotary wheel for casting, C2) and (2)
') is a metal endless belt before and after forming a J shape,
(3) is a pressure wheel ゛τ゛ for pressing the endless belt (2) against the surface of the rotating casting wheel α), and this pressure wheel (3)
Directly below the casting rotary ring (1) and force] (end bell) (2
') molds are formed continuously.

When the mold is opened, the tip of the tandish (4), which is supported horizontally, is charged into the first part.

In this facility, molten aluminum (5) flows through a transfer trough from a molten metal holding furnace (not shown) and is transferred to a tundish (4).
) K is transferred and continuously injected into the mold, and its circumference 1f1
The ingot (
6).

Shake at that time! An ultrasonic vibration yσ applying device consisting of a 191 element, a horn, etc. is installed above the tundish (4), and a pawn (7) is inserted into the molten metal. In the drawing, the vibrator is omitted.

Therefore, in the present invention, the circumferential surface of the horn (7) is
- The stationary l- to prevent erosion consists of a pool (8) that flows at an extremely low speed, the details of which are as follows.

(9) is a container formed of an insulating heat insulating material in the shape of an inverted cup and sealed with molten metal, forming a decompression chamber inside.

(10) is a pressure reduction pump for reducing the pressure inside the pressure reduction chamber (9), and (11) is a pressure that indicates the pressure inside the pressure reduction chamber (9) and transmits an electric signal to operate the pressure reduction pump (10). It is an indication regulator.

(12) is a communication pipe that communicates the decompression chamber (9) with the decompression pump (10) and pressure indicating regulator (11).
A series of these decompression mechanisms are operated in the decompression chamber (9) by the following operations.
The pressure inside the vacuum chamber is reduced to raise and maintain the molten metal surface (5') at a constant level.

First, the pressure to be regulated or controlled is set in the pressure indicating regulator (11), but at this point, the pressure inside the decompression chamber is higher than the set pressure, that is, atmospheric pressure, so the pressure indicating regulator (11) is operated by the decompression pump. (10), which activates the decompression pump (10) and also indicates the pressure in the decompression chamber (9). When the pressure in the decompression chamber (9) reaches the set pressure, An electric signal is immediately sent to stop the decompression pump (10). By repeating this operation, the inside of the decompression chamber (9) is maintained at a constant pressure, and at the same time, the molten liquid in the mendices (4) is sucked into the decompression chamber (9) and its surface (5) ') comes to a position higher than the hot water level in the water tank (4), and the w force in the decompression chamber (9) and the decompression JJE chamber (
The molten metal head in the chamber (9') is kept constant at a position where it is in equilibrium with the atmospheric pressure.・This set pressure iL leaves a space (13) above the molten metal surface (5') in the decompression chamber (9). An insulated hot water level detection needle (14) is installed in this space (13).
) is installed through the wall of the decompression chamber (9) and the Ichihara device W
(lfi), an alarm (16), and a lead wire (17) are connected to the casting machine main body, and if the hot water level in the decompressed chamber rises above the normal level due to a malfunction of the pressure indicator regulator or other causes, this will cause the hot water level to rise. When the detection needle (14) comes into contact with the molten metal (5), the above series of circuits closes and an alarm is issued, and at the same time the decompression pump (
]0) Next, in order to further clarify the effects of the present invention, using the apparatus shown in Figure 1, aluminum bath water maintained at 700°C ± 2°C was cast at a casting speed of 12.5 m/m. A comparative experiment was conducted between the conventional method and the method of the present invention.

The dimensions and set pressure of the main parts of the device used in the invented method for the same vehicle were as follows.

The inner dimensions of the decompression chamber are inner diameter (Do) 60wφ and height II.
o) 120 mm, and the diameter (DH) of the horn that transmits ultrasonic vibrations to the molten metal is 30 mm. The set pressure of the pressure indicator regulator is 0.98 Kf/m, which is atmospheric pressure (1,
, OKt/cJi) was set to 0.02 Kf/ctJ. As a result, the height of the molten metal in the vacuum chamber (HI□) is approximately 83■.

The horn material used in both the conventional method and the method of the present invention was titanium, and the applied frequency was 17Kliz. Bahorn is about 7
It has a service life that is 0 times longer, and the crystal grains of the ingot have a #1 (11) concentration compared to those using refining additives such as TiBx.
It was equivalent to the Soviet Union.

In the above embodiment, the penetration angle θ′f of the pawn into the molten metal
: is set to v90°, but this may be 106 or more with respect to the horizontal line.

Ceramic fibers are used for the seal between the main horn (7) and the decompression chamber (9), but the material is not limited to this. It is now possible to refine the crystal grains of ingots on an industrial scale without using a metallurgy, stably for a long time, and at low maintenance costs, and the industrial effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the method of the present invention. 1・・・・・・・・・・・・Rotary wheel for casting 2.2
′・・・・・・Metal painless belt 9− 4・・・・・・・・・Menditshu 6・・・
・・・・・・・・・Ingot 7・・・・・・・・・Horn 8・・・・・・・・・Pump 9・・・・・・・・・・・・・・Inverted cup-shaped container (decompression chamber)
10・・・・・・・・・・・・Reducing pump 10-

Claims (1)

[Claims] 1. The mold is continuously formed using a rotating casting wheel with grooves on its curved surface and an endless metal belt that runs in contact with the circumferential surface of the rotating wheel. In the belt-wheel type continuous casting method, a molten metal is continuously injected into the mold and is cooled and solidified by cooling water applied to the circumferential surface of the mold to continuously obtain an ingot. The inside of an inverted cup-shaped container is immersed and inserted from above into the molten metal that is continuously injected into the mold, and the molten metal is kept rising inside the container by reducing the pressure, thereby making the molten metal stand still or nearly stationary. A continuous casting method in which a horn that applies ultrasonic vibrations is inserted into a pool of metal, and the ultrasonic vibrations are applied to the solidification interface in the mold through the molten metal.