JPS5825845A - Hot top casting device - Google Patents

Abstract

PURPOSE:To improve the lubricity of the inside wall surface of a mold of a hot top casting device with less lubricating oil, to decrease the number of polishing steps for the mold surfaces and to improve the quality of the surface of cast ingots by forming a chrome plating layer on the inside wall surface of the mold. CONSTITUTION:A direct cooling mold 22 of a cylindrical shape made of pure copper is provided below a receiving tank (hot top) 20 made of refractories for molten metal, and the circumferential bottom end part of the tank 20 overhangs from the inside wall surface thereof to the inner side, thereby forming an overhange part 24. A hard chrome plating layer 40 of a prescribed thickness is formed over the entire circumferential surface of the inside wall surface of the mold 22 in contact with molten metal. When the molten metal 21 is supplied, a molten metal column is formed on a bottom plate 42 by the inside wall surface of the mold 22 and the tank 20, and said column is primarily cooled via the layer 40 by the cooling water flowing through the chamber 26. Thereafter, the molten metal is cooled secondarily wit the water ejected through slits 30 and is removed as a cast ingot 32. During this time, lubricating oil is supplied continuously from a supply passage 38 through a well 34 and a groove 36 to the inside wall surface of the groove 22.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot-top casting apparatus, and particularly to a hot-top casting apparatus that improves mold lubricity and extends mold life when continuously casting aluminum or aluminum alloy ingots by hot-top casting techniques. The present invention also relates to a mold that can effectively improve the quality of the surface of the resulting ingot.

Traditionally, ingots of metals such as aluminum and aluminum alloys have been cast by the well-known continuous casting method, but recently, a molten metal receiving tank made of an insulated refractory material has been installed above the mold to allow the metal to solidify. A casting method called hot top casting method or closed casting method, in which molten metal is held under high hydrostatic pressure above a layer, is being adopted, and a typical device for this method is as shown in Figure 1. It has a structure.

That is, a molten metal receiving tank 2 made of a refractory material is provided above a cylindrical direct cooling mold 4, and a lower end of the inner periphery of the molten metal receiving tank 2 protrudes inward from the inner wall surface of the mold 4 to form an overhang portion 5. A direct cooling mold 4 with a molten metal receiving tank 2 is used, and a molten metal 6 to be cast is stored in the molten metal receiving tank 2, while a supply passage 8 is passed through the inner wall surface of the mold 4. While holding the molten metal 6 in a columnar shape close to the lubricating interface formed by the supplied lubricating oil, the coolant 10 (generally water is used) that is forced to flow through the mold 4 continuously cools the metal through the inner wall surface of the mold. The columnar ingots 12 that are continuously taken out from the opening at the bottom of the mold 4 are cooled (secondary cooling) by injecting the coolant 10 to the columnar ingots 12, which are completely cooled to the inside. By solidifying the ingot 12, the desired ingot 12 is obtained.

By the way, in such a hot top casting method, since the surface of the molten metal exists in the molten metal receiving tank 2, there is no need to strictly adjust the height of the molten metal surface in the mold as in the conventional casting method. However, this method is still far from being a perfected technology, and because the primary cooling from the inner wall of the mold is particularly strong, it can cause twitching skin on the casting surface (cold shirt). 5hut), and the width of the component segregation region near the casting surface is also large.

For this reason, in Japanese Patent Publication No. 54-42847, etc., a method is proposed in which air, nitrogen, or inert gas is injected between the refractory molten metal receiving tank and the direct cooling mold to reduce contact between the molten metal and the directly cooling mold. Also, British Patent No. 1,189,784 discloses a structure in which a graphite ring 14 is inserted in the part where the molten metal directly contacts the cooling mold to reduce secondary (mold) cooling, as shown in FIG. , as solutions have been proposed, but none of these measures can sufficiently improve the structure of the ingot surface or the surface layer of the ingot, or the casting work and mold structure are complicated. For practical purposes, further improvements were needed. For example, in the case of the former gas injection bundle, it is difficult to control the injection amount, and in the case of the latter graphite ring insertion tube, although the second cooling capacity can be reduced, there is no graphite on the surface of the casting surface. There are problems such as the appearance of taut skin that is unique to rings.

The present invention has been made in view of the above circumstances, and is characterized in that a molten metal receiving tank made of a refractory material is provided above and the lower end of the inner periphery of the molten metal receiving tank is formed into a mold. It includes a direct cooling mold with a molten metal receiving tank that extends inward from the inner wall surface to form an overhang part, the molten metal to be cast is stored in the molten metal receiving tank, and the molten metal is held in a columnar shape within the mold. , continuous cooling,
In a hot-top casting machine designed to solidify the metal, a chrome plating layer is formed on the inner wall surface of the direct cooling mold that comes into contact with the molten metal, thereby significantly increasing the lubricity of the inner wall surface of the mold. It reduces the consumption of lubricating oil, effectively suppresses the sticking of the ingot to the mold surface, reduces the man-hours required for polishing the mold surface, and significantly improves the quality of the ingot surface. I was able to accomplish this.

Hereinafter, the present invention will be explained in more detail based on embodiments shown in the drawings.

First, FIG. 3 shows that a cylindrical mold (direct cooling mold) 22 made of pure copper is provided below a molten metal receiving tank (metal top) 210 made of a hollow heat-insulating refractory according to an embodiment of the present invention. ing. The mold 22 is arranged so that the lower end of the inner periphery of the molten metal receiving tank 20 protrudes inward from the inner wall surface of the mold to form an overhang portion 24. A cooling water chamber 26 is formed inside the mold 22, and cooling water as a coolant is supplied from the outside to the supply pipe 26.
The mold 22 is cooled by being guided into the cooling water chamber 26 through the cooling water chamber 8 and flowing therethrough, while the slit 3 provided around the lower opening of the mold 22 cools the mold 22.
From 0, the cooling water is injected onto the ingot (molten metal column in a semi-solidified state) 32 to be formed, thereby directly cooling it. Further, inside the upper part of the mold 22, there is provided a lubrication system consisting of a lubricating oil reservoir 34, a lubricating oil groove 36 that leads the lubricating oil from there to the inner wall surface of the mold and the upper part, and a supply path 88 that supplies the lubricating oil thereto. During the casting operation, lubricating oil is continuously supplied to the inner wall surface (mold surface) of the mold 22 to create a lubricated interface. In addition, l! is attached to the inner upper end of the mold 22! At the above-mentioned lubricating oil groove 36 which is opened, the hard chrome plating layer is removed from the lubricating oil reservoir 7I.

When the molten metal 21 is supplied, the inner wall surface of the mold 22 and the molten metal receiving tank 2
0, a molten metal column is formed on the bottom plate 42, and after this is cooled by the cooling water flowing through the cooling water chamber 26 through the chrome plating layer 40 formed on the inner wall surface, Furthermore, the slit 30 at the bottom of the mold 22
The ingot 32 is completely solidified to the inside by being secondary cooled by the cooling water jetted from the ingot, and as the bottom plate 42 descends, it is continuously taken out as a columnar ingot. , a mold 22 that primarily cools the molten metal 21; the inner wall surface is a hard chrome plating layer 4;
Furthermore, due to the smooth surface of the plating layer 40, the lubricating oil supplied thereto spreads uniformly over the entire surface, forming a lubricating interface that exerts an effective lubricating action, which significantly improves the life of the mold. This also significantly improved the lubricity of the mold. Therefore, by providing the loam plating layer 40 on the inner wall surface of the mold 22, it is possible to significantly reduce the consumption of lubricating oil.
For example, the distribution of rapeseed oil and castor oil becomes more even,
Even if the supply amount is halved, the occurrence of casting surface defects such as deterioration of the ingot surface and twitching phenomenon can be effectively suppressed.

In addition, the seizure between the mold 22 and the ingot 32 is significantly reduced, the adhesion of slag due to seizure is eliminated, and a smooth surface is maintained for a long period of time, which is necessary in the past. Frequent polishing work on the surface of the mold 22 can be omitted, making it possible to significantly reduce the number of repair work, which also greatly contributes to improving the life of the mold.

Incidentally, the excellent effects of the present invention as described above have been demonstrated by the following experiments.

In other words, this experiment examined the effects of the presence or absence of a chrome plating layer (40) on the inner wall surface of the mold, but in the case of no chrome plating layer (40), the occurrence of seizing and twitching phenomena in the ingot was suppressed. for 2~4 cc/
However, in the case where the chrome plating layer (40) with a thickness of 10 μm is provided according to the present invention, the amount of lubricating oil (castor oil) to be supplied is reduced. Even when the flow rate was reduced to 1.5 to 2 cc/min, approximately half of the conventional rate, there was hardly any problem with seizure, and no casting surface defects such as twitching were observed.

In addition, the mold with 9 chrome plating layers remained smooth even after 300 semi-continuous OJ operations and did not require polishing, but the mold without chrome plating layer had 30 to 50 chrome plating layers. The repeated semi-continuous casting operations caused seizures and casting surface defects, necessitating polishing of the mold surface.

The thickness of the chrome plating layer (40) formed on the inner wall surface of the mold (22) according to the present invention varies depending on the casting conditions, the type of molten metal, etc., and is difficult to regulate unambiguously. A thickness of about 30 μm is preferably employed. If this plating layer is too thin, the existence of the plating layer becomes meaningless and the purpose of the present invention cannot be fully achieved. If it is too thick, it will only have a negative effect on the primary cooling function of the molten metal. This results in technical and economic problems during processing.

Generally, such a chrome plating layer is provided over the entire inner wall surface (mold surface) of the mold 22 as in the previous example, but the plating layer comes into contact with the molten metal and ingot (solidified shell) on the inner wall surface. Therefore, there is no problem in omitting the formation of the plating layer on the inner wall surface that does not contact the ingot at the bottom of the mold.

Further, the casting apparatus according to the present invention is particularly suitable for manufacturing thin rods of aluminum or aluminum alloy with a diameter of about 40 to 1100 nφ, but of course, it can also be used when manufacturing rod-shaped ingots with a larger diameter. Needless to say, it can also be advantageously applied.

In addition, the casting apparatus according to the present invention can be combined with the lubricating oil supply method for multiple casting casting disclosed in Japanese Patent Application No. 11191/1987, which was previously filed by one of the inventors, to achieve even more remarkable effects. It is played. That is, the previously filed invention is a multiple casting method in which a plurality of ingots are continuously formed by arranging a plurality of molds and supplying a predetermined molten metal to each mold, cooling and solidifying the same. In this method, a lubricating device is used which has a plurality of pump elements arranged in parallel with a constant discharge amount, one drive shaft for driving the pump elements, and a variable rotation speed motor connected to the drive shaft. A predetermined amount of lubricating oil discharged from a plurality of pump elements each driven by the same drive shaft of an oil supply device is guided to each mold via an oil supply path from each pump element to each mold. By effectively supplying lubricating oil to each mold according to this method, the effect of the chrome plating layer according to the present invention in each mold can be improved. It is possible to make the most of it.

In addition, the present invention is not limited in any way to the specific examples illustrated above, and various changes and improvements can be made based on the knowledge of those skilled in the art without departing from the spirit of the present invention. For example, in the upper case, the mold 22 is made of pure copper and has a cylindrical shape, but it may be made of aluminum, an aluminum alloy, a copper alloy, etc. Instead, a rectangular cylindrical one will be used. Furthermore, the secondary cooling that is added after the primary cooling of the molten metal by the inner wall surface of the mold can be achieved by using coolant distributed around the opening at the bottom of the mold, in addition to the conventional method in which the coolant is flowed through the mold and is ejected from the bottom of the mold. There is no problem even if the cooling is performed by jetting the coolant from a coolant jet pipe.

It makes it possible to significantly reduce the amount of lubricating oil consumed, extend the life of the mold, and effectively prevent seizure of the mold surface so that the surface is always kept smooth. This method has great industrial significance in that it has achieved a reduction in the number of man-hours required for polishing the mold surface.

[Brief explanation of the drawing]

FIGS. 1 and 2 are longitudinal cross-sectional views of main parts showing different representative examples of conventional hot-top casting apparatuses, and FIG. 3 is a longitudinal cross-sectional view showing an example of the hot-top casting apparatus according to the present invention. 20: Molten metal receiving tank 21: Molten metal 22: Mold (
Direct cooling mold) 24; Overhang part '32: Ingot 34: Lubricating oil reservoir 36: Lubricating oil groove 38: Supply path 40: Chrome plating layer Applicant: Sumitomo Light Metal Industries, Ltd.

Claims (1)

[Claims] The molten metal includes a direct cooling mold with a molten metal receiving tank, in which a metal resistant metal receiving tank made of a refractory material is provided above, and the lower end of the inner periphery of the molten metal receiving tank extends inward from the inner wall surface of the mold to form an overhang part; In a hot top casting device, the molten metal to be cast is stored in a receiving tank, and is continuously cooled and solidified while being held in a columnar shape within the mold. A hot top casting device characterized by forming a chrome plating layer on the inner wall surface that comes in contact with the hot top casting device.