JPS637318B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a melting and holding furnace equipped with a heating element for holding molten metal in a molten state.

When melting various metals and injecting them into molds to cast machine parts, generally the molten metal is not directly taken out of the melting furnace and poured into the molds; The melt is transferred from the melting furnace to a melting and holding furnace, where it is held in a molten state, and a predetermined amount is taken out and cast. For example, when manufacturing automobile parts by casting aluminum alloy, the aluminum alloy is first melted in a melting furnace, the molten aluminum alloy is transferred to a melting and holding furnace, and then from this melting and holding furnace. Molten metal is taken out little by little and poured into a mold to perform casting.

Figures 1 and 2 show a conventional external heating type aluminum melting and holding furnace.
is composed of a brick wall 2 and an iron plate 3,
A heating element 4 is placed above it. A heat shielding cover 5 is attached to the top of the heating element 4. The drawback of such a conventional external heating type melting and holding furnace is that the heating element 4 is placed in the upper part of the furnace 1, and the molten metal 6 is indirectly heated by the heating element 4, which reduces thermal efficiency. There is a bad thing. Further, since a considerable portion of the heat generated from the heating element 4 is dissipated to the outside, the temperature of the atmosphere increases, thereby deteriorating the working environment.

Furthermore, in this conventional external heating type melting and holding furnace, a ceramic filter 7 is disposed inside the furnace 1, but since this ceramic filter 7 has heat insulating properties, the bottom of the filter 7 is The temperature of the molten metal 6 on the side becomes lower. Therefore, it is necessary to place the horizontal portion of the ceramic filter 7 and the hearth as close to the heating element 4 as possible. On the other hand, the molten metal 6 in the furnace 1 gradually decreases as it is used, and eventually the liquid level will be below the bottom surface of the filter 7.
The molten metal becomes oxidized and becomes unusable. Therefore, if the ceramic filter 7 is installed at a high position and close to the heating element 4, the molten metal 6 in the furnace 1 cannot be used effectively, and accordingly, the number of times the molten metal must be replenished is increased. It will stop happening. In other words, in order to use as much of the molten metal 6 in the furnace 1 as possible, it is necessary to install the filter 7 as close to the hearth as possible. This causes the problem that the value is not retained.

Furthermore, in this type of melting and holding furnace, since a heating element 4 and a heat shielding cover 5 are provided on the upper part of the furnace 1, workability or accessibility when replenishing molten metal into the furnace 1 is improved. There were defects and it was not possible to save labor.

Another conventional melting and holding furnace is, for example, a vertical immersion type melting and holding furnace shown in FIGS. 3 and 4. In this furnace 1, the heating element 4 is connected to the immersion tube 8.
The upper end of this immersion tube 8 is supported by a heat shielding cover 5, and the lower part of the immersion tube 8 is immersed in the molten metal 6 in the furnace 1. In this type of molten metal holding furnace 1, approximately half of the total length of the immersion tube 8 into which the heating element 4 is inserted is the molten metal 6.
Because the system is immersed inside the system, thermal efficiency is considerably improved compared to external heating systems. However, not all of the heat generated from the heating element 4 is transferred to the molten metal 6, and some of the heat escapes into the atmosphere.
Therefore, the working environment is not improved much either.

Furthermore, in this melting and holding furnace 1, the immersion tube 8
will always come into contact with the liquid surface of the molten metal 6 at some position. The temperature change at the liquid level or impurities such as aluminum oxide or flux in the molten metal 6 makes it susceptible to high-temperature attack. Therefore, the portion of the immersion tube 8 that comes into contact with the liquid surface is damaged, and the molten metal 6 may enter the interior of the immersion tube 8, causing the heating element 4 to be easily damaged.

Furthermore, since the upper end of the heating element 4 inserted into the immersion tube 8 is supported by the heat shield cover 5, heating occurs near the terminal 9 at the upper end of the heating element 4. This tends to occur, and this tends to cause poor contact of the terminals 9. Further, since the dip tube 8 is supported by the cover 5 only by the upper end, the support of the dip tube 8 and the heating element 4 becomes unstable, and the dip tube 8 tends to wobble.

Further, in this vertical immersion type melting and holding furnace, when the amount of molten metal 6 in the furnace 1 decreases due to use, new molten metal 6 is replenished. Then, when replenishing while pouring this molten metal 6,
The molten metal 6 in the furnace 1 is stirred, and aluminum oxide and the like are suspended therein. Therefore, after replenishing the molten metal 6 into the furnace 1, it is no longer possible to immediately take out the molten metal from the furnace 1 and use it, and it is necessary to allow a 30 to 60 minute calming time to calm and purify the molten metal 6. . Therefore, in order to use the molten metal 6 continuously, two furnaces must be provided and replenishment and use must be performed alternately, which is disadvantageous in terms of equipment.

Furthermore, in this furnace 1 as well, the heating element 4 is inserted so that the upper end of the immersion tube 8 is exposed at the upper part of the furnace 1, and a heat shielding cover 5 is provided on the upper part of the furnace 1, so that the molten metal is There is a problem in workability when replenishing the molten metal 6, and it is also a cause of hindering labor saving in replenishing the molten metal 6.

The present invention has been made in view of the various problems mentioned above, and has excellent thermal efficiency, improves the working environment, eliminates restrictions on the relative position of the filter and the heating element, and furthermore, It is an object of the present invention to provide a melting and holding furnace in which damage is prevented.

The present invention will be explained below with reference to an illustrated embodiment.
5 and 6 show a furnace 10 according to this embodiment, and this furnace 10 shows an inner brick 11
The melt tank is formed into a substantially rectangular parallelepiped shape by the outer iron plate 12 and the outer iron plate 12. The upper part of this furnace 10 is an opening 13. A filter 14 made of ceramic foam is disposed within the furnace 10. The ceramic filter 14 has a substantially L-shaped cross section, and its upper end is supported by a heat shield cover 15 that covers substantially the center of the opening 13. Furthermore, a pair of heating elements 16 are horizontally arranged in the furnace 10, with each heating element 16 being inserted into an immersion tube 17. The heating element 16 is made of silicon carbide, for example, and the immersion tube 1
7 is composed of silicon nitride bonded silicon carbide.
This immersion tube 17 is supported at both ends by the mutually opposing walls of the furnace 10, and a terminal 18 connected to the heating element 16 protrudes from one end of the immersion tube 17. Electric current is passed through the heating element 16 via the terminal 18.

In the above configuration, the molten aluminum alloy (JISAC8A) molten metal 19 melted in the melting furnace enters the furnace 10 from the right side of the cover 15 of the opening 13 of the furnace 10 shown in FIGS. 5 and 6. Injected. This molten metal is purified by passing through a ceramic filter 14 to remove impurities such as oxides and gases.
The purified molten metal 19 is pumped out from the opening 13 on the left side of the cover 15 and poured into a mold or the like, thereby casting various parts made of aluminum alloy.

According to the melting and holding furnace 10 according to this embodiment, the thermal efficiency is greatly improved compared to the conventional melting and holding furnace. That is, in the furnace 10 according to this embodiment, the immersion tube 17 into which the heating element 16 is inserted is installed horizontally, parallel to the hearth, and is completely immersed below the surface of the molten metal 19. . Therefore, almost all of the thermal energy generated by the heating element 16 is consumed to maintain the temperature of the molten metal 19. Now, the capacity of the furnace 10 is set to 1 ton, and the power required to maintain the molten aluminum alloy 19 injected inside at 750° C. is now only 15 KW. For comparison, according to the conventional external heating method, it takes 50KW of power to maintain the same amount of molten aluminum alloy at the same temperature, and the conventional vertical immersion method also consumes 22KW of power. Therefore, according to the molten metal holding furnace 10 according to this embodiment, the thermal efficiency is clearly improved, and the power consumption is also reduced accordingly.

Further, according to the melting and holding furnace 10 according to this embodiment, the working environment is greatly improved. That is, the heating element 16
Since the immersion tube 17 into which the immersion tube 17 is inserted is completely immersed in the molten metal 19, the radiation of heat to the outside is extremely reduced. Further, it is also possible to provide insulation to prevent the heat generated by the molten metal 19 from dissipating to the outside more easily than in the past. This is because the heating element 16 and the immersion tube 17 are not arranged in the upper part of the furnace 10, and this also makes it possible to reduce the radiation of heat to the outside of the furnace 10. Actually, 30 cm horizontally from the wall of the furnace 10 according to this embodiment.
When I measured the temperature at a distance, it was about 30℃.
It was hot. By the way, when we conducted similar measurements in a conventional furnace, the temperature was approximately 60°C in the external heating method and approximately 50°C in the vertical immersion method. Therefore, by lowering the temperature near the furnace 10 in this way, the working environment is greatly improved.

Furthermore, according to the furnace 10 according to the present invention, the heating element 1
Since the dipping tube 17 into which the filter 6 is inserted is arranged horizontally below the surface of the molten metal 19, it is possible to install the dipping tube 17 particularly close to the horizontal portion of the filter 14. Therefore, filter 1
It becomes possible to prevent the temperature of the molten metal 19 below the horizontal portion of the filter 14 from decreasing, and in conjunction with this, it becomes possible to bring the horizontal portion of the filter 14 very close to the hearth. Since the filter 14 can be placed close to the hearth, the amount of molten metal that can be used increases. Therefore, it becomes possible to reduce the number of times the molten metal 19 is replenished, or it becomes possible to increase the amount of molten metal 19 that can be used before replenishing the molten metal 19. That is, in the case of the furnace 10 of this embodiment, when the capacity is 1 ton, it is possible to use 600 kg of molten metal 19 without replenishing it. By the way, conventional external heat type furnaces could only handle up to 300 kg. Therefore, according to this embodiment, the number of times of replenishment of molten metal is halved compared to the conventional method.
The molten metal 19 can be used efficiently.

Further, in the furnace 10 according to the present embodiment, since almost the entire length of the immersion tube 17 into which the heating element 16 is inserted is immersed below the liquid surface of the molten metal 19, a portion of the immersion tube 17 is part will not come into contact with the liquid surface. Therefore, there is no high-temperature corrosion of the dip tube 17 in the parts in contact with the liquid surface, thereby improving the service life of the dip tube 17. Note that the lifespan of the heating element 16 is generally longer than that of the immersion tube 17, so the immersion tube 17 should be periodically replaced before the immersion tube 17 breaks and the molten metal 19 infiltrates and damages the heating element 16. It is normal to replace it with In this embodiment, the heating element 16 is completely enclosed within the immersion tube 17, and the immersion tube 17 is not subjected to high-temperature immersion, so that the life of the heating element 16 is extended.
When the lifespans of the immersion tube 17 and the heating element 16 were actually measured, they were approximately 70 days and 180 days, respectively. By the way, according to the conventional vertical immersion method,
They are 50 days and 80 days, respectively. Therefore, it is clear that the melting and holding furnace 10 according to this embodiment can extend the life of the immersion tube 17 and the heating element 16.

Furthermore, according to the melting and holding furnace 10 according to the present embodiment, the immersion tube 17 is reliably supported at both ends by the mutually opposing walls of the furnace 10, unlike in the conventional vertical immersion method. This prevents the heating element 16 or the immersion tube 17 from wobbling. Further, the terminal 18 for passing current to the heating element 16 is connected to the furnace 1.
Since it is provided on the side of the molten metal instead of the top, it does not receive the heat generated by the heating element 16 or the molten metal 19, and is therefore protected from high temperatures. Therefore, it is possible to prevent poor contact due to heating of the terminal 18 and to maintain the temperature of the molten metal 19 stably. Also, this also allows the heating element 16 to have a longer lifespan.

Further, according to this embodiment, since the ceramic filter 14 is disposed inside the furnace 10,
Even when the molten metal 19 is exhausted and new molten metal is injected into the furnace 10, the refilled molten metal 19
will be immediately purified by the filter 14. Therefore, the purified molten metal can be used immediately, and there is no need to provide two furnaces. That is, the molten metal 19 can be used continuously in one furnace 10. Therefore, the space for installing the furnace 10 is also reduced. Further, according to this embodiment, since no heating source is present in the upper part of the furnace 10, the proximity and workability when replenishing the molten metal 19 are improved, and the handling of the molten metal is also facilitated.

Although the present invention has been described above with reference to an illustrated embodiment,
The present invention is not limited to the above embodiments, and various modifications can be made based on the technical idea of the present invention. For example, as shown in FIG. 7, a plurality of immersion tubes 17, for example three immersion tubes 17 each housing a heating element 16, may be arranged on opposite sides of the ceramic filter 14. In this case, the amount of heat generated by each heating element 16 can be reduced. Alternatively, as shown in FIG. 8, the ceramic filter 14 may be formed into a substantially plate-like shape, and the filter 14 may be arranged vertically within the furnace 10 so as to divide the interior into two parts. In this case, since there is no horizontal portion of the filter 14, there is no heat insulating effect on the heating element 16. Therefore, it becomes possible to use the heat of the heating element 16 more effectively, and the immersion tube 17 into which the heating element 16 is inserted can be placed closer to the hearth. Therefore, with such a configuration, the molten metal 19 can be pumped out more effectively.

As described above, the present invention relates to a melting and holding furnace in which a heating element is inserted into a immersion tube and the entire immersion tube is immersed below the surface of the molten metal. Therefore, according to the present invention, it becomes possible to maintain the temperature of the molten metal by effectively utilizing the heat generated from the heating element, thereby improving thermal efficiency and improving the working environment. Furthermore, since the immersion tube into which the heating element is inserted is immersed below the surface of the molten metal, it is possible to extend the life of the heating element and the immersion tube.

Further, the melting and holding furnace according to the present invention includes a filter that divides the inside of the furnace into two. Therefore, when the molten metal runs out and new molten metal is injected, the replenished molten metal is immediately purified by the filter, making it possible to remove impurities such as oxides and gases, making it possible to drain the molten metal in the furnace. Ready for casting immediately. Therefore, when molten metal is used continuously, it is not necessary to install two holding furnaces and use them alternately as in conventional holding furnaces, but only one holding furnace is required. This also brings about the special effect of reducing the space for installing the furnace.

Furthermore, according to the present invention, since the immersion tubes each having a heating element are arranged on both sides of the filter arranged to divide the inside of the furnace into two, the temperature of the molten metal is lowered on each side of the filter. You won't have to do anything. Therefore, it becomes possible to supplement the heat insulating properties of the filter, so that the filtration effect of the filter does not decrease, and it becomes possible to use a ceramic filter having heat insulating properties.

[Brief explanation of the drawing]

Figure 1 is a plan view of a conventional external heat type molten metal holding furnace, Figure 2 is a sectional view taken along the line ~ in Figure 1, Figure 3 is a plan view of a conventional vertical immersion type melt holding furnace, and Figure 4. is a sectional view taken along the line ~ in Figure 3, Figure 5 is a plan view of a melting and holding furnace according to an embodiment of the present invention, Figure 6 is a sectional view taken along the ~ line in Figure 5, and Figure 7 is a modified example. A sectional view similar to FIG. 6 of the melting and holding furnace, and FIG. 8 is a sectional view of the melting and holding furnace according to another modification. In addition, in the symbols used in the drawings, 10...furnace,
13...Opening, 14...Ceramic filter,
15... Heat shield cover, 16... Heating element, 17...
Immersion tube, 18... terminal, 19... molten metal.

Claims (1)

[Claims] 1. In a melting and holding furnace equipped with a heating element for holding molten metal in a molten state, a filter is provided to filter the molten metal so as to divide the inside of the furnace into two, and the heating element is inserted into an immersion pipe. ,
A melting and holding furnace characterized in that the immersion tubes are arranged on both sides of the filter, and the entire immersion tube is arranged below the surface of the molten metal.