JP2018094622A - Molten metal holding furnace for low pressure casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To circumvent deterioration in casting quality by preventing the released air bubbles from flowing into the molten metal to be injected into a mold when pressurized gas entering into the material constituting a molten metal container of the molten metal holding furnace for low pressure casting is discharged as bubbles into the molten metal.SOLUTION: A plate member made of a material having a porosity lower than that of the molten metal container is disposed at the bottom of the molten metal container substantially directly beneath the outlet.SELECTED DRAWING: Figure 1

Description

The present invention relates to a molten metal holding furnace for low pressure casting.

As in Patent Document 1, a holding furnace for low-pressure casting in which a molten metal storage container that is in direct contact with the molten metal is made of a breathable material such as a regular refractory or an irregular refractory is known.
In low-pressure casting, an inert gas such as air or argon or nitrogen is supplied into a holding furnace having a molten metal and pressurized, whereby the molten metal in the furnace is filled in a mold cavity and casting is performed. In the holding furnace for low pressure casting having a molten metal storage container made of a material having air permeability, in the step of supplying the pressurized gas, after the pressurized gas enters and is held in the material constituting the molten metal storage container, In the step of stopping the supply of the pressurized gas and exhausting it from the holding furnace, the invaded gas is released as bubbles into the molten metal stored in the molten metal storage container. At that time, the bubbles rise while oxidizing the surrounding molten metal, and flow into the stalk having the outlet. Bubbles (oxides) that flow into the stalk flow into the mold cavity from the outlet when supplying pressurized gas into the holding furnace again, creating hard spots in the cast product, etc. It was a cause of quality degradation.

Patent Document 2 includes a shut-off valve that opens and closes a melt channel opening located between a melt holding chamber and a pressurizing chamber, and the pressurizing chamber has a pressurizing unit and a tapping unit that communicate with each other at the bottom. A holding furnace for low-pressure casting is disclosed in which the inner wall surfaces of the pressurizing part and the hot water part are made of a fine fired product made of fine ceramics.
In the holding furnace for low-pressure casting described in the publication, the inner wall surface of the pressurizing part is made of non-breathable fine ceramics, so that it is possible to prevent the pressurized gas from entering the molten metal storage container.

JP, 2006-140887, A Japanese Patent No. 4615300

However, in the holding furnace for low-pressure casting described in Patent Document 2, a monolithic fired product made of fine ceramics is more expensive than a regular refractory or an amorphous refractory, and therefore the cost of the low-pressure casting holding furnace increases. was there.
Even if the inner wall surface of the pressurizing part is made of non-breathable fine ceramics, the fine ceramics will have cracks, cracks, etc. due to physical shock during heat shock and maintenance, etc. As a result, the bubbles generated in the molten metal could cause the product quality to deteriorate.

In view of the above problems, the present invention provides a molten metal that is injected into a mold when the pressurized gas that has entered the material constituting the molten metal container is discharged as bubbles into the molten metal. The purpose is to prevent inflow.

  In order to achieve the above object, the low pressure casting holding furnace of the present invention is a low pressure casting holding furnace having a molten metal storage container made of a material having air permeability, and the bottom of the molten metal storage container has a lower part than the molten metal storage container. Also, a plate-like member made of a material having a low porosity is arranged so as to be almost directly below the hot water outlet. The plate-like member is installed, for example, in a recess provided in the bottom of the molten metal storage container via a filler such as cement.

As a result, the gas that has entered the material constituting the molten metal storage container cannot be released into the molten metal from the contact surface of the plate member having a lower porosity than the material constituting the molten metal storage container. It is discharged into the molten metal from a position where the member is not in contact, or is discharged to a refractory layer and / or a heat insulating layer made of a material having a higher porosity than the molten metal storage container located outside the molten metal storage container.

Thus, it was set as the structure which prevents that the gas which penetrate | invaded in the material which comprises a molten metal storage container flows in into the molten metal inject | poured into a metal mold | die from a hot water outlet.

According to the low pressure casting holding furnace according to the present invention, when pressurized gas enters the material constituting the molten metal storage container, the bottom of the molten metal storage container has a lower porosity than the molten metal storage container. Since the plate-like member made of the material is arranged so as to be almost directly below the hot water outlet, the gas that has entered the material constituting the molten metal storage container has a lower porosity than the material constituting the molten metal storage container. It cannot be discharged from the surface where the plate-shaped member is in contact, but is discharged from a location where the plate-shaped member is not in contact, or is made of a material having a higher porosity than the molten metal storage container located outside the molten metal storage container. Release into refractory and / or heat insulation layers

As a result, it becomes possible to prevent bubbles from being released from the molten metal storage container that is directly below the outlet, so that the amount of bubbles flowing into the molten metal injected from the outlet into the mold can be reduced. become.

In addition, the total amount of bubbles released from the molten metal storage container to the molten metal is reduced by the amount released from the molten metal storage container to the refractory layer and / or the heat insulation layer. It is possible to reduce the total amount of bubbles to be generated.

The molten metal holding furnace for low-pressure casting of the 1st embodiment of the present invention. In 1st Embodiment, the cross-sectional shape of a plate-shaped member becomes a trapezoid. In 1st Embodiment, the cross-sectional shape of a hollow becomes trapezoid. In 1st Embodiment, the cross-sectional shape of a plate-shaped member and a hollow becomes trapezoid. The molten metal holding furnace for low pressure casting of the 2nd Embodiment of this invention. The molten metal holding furnace for low pressure casting of the 3rd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a molten metal holding furnace 1 for low pressure casting according to a first embodiment of the present invention.
The molten metal holding furnace 1 includes a molten metal storage container 12, and the molten metal storage container 12 is formed of a material having air permeability such as an alumina-based amorphous refractory. In this embodiment, the molten metal storage container 12 is formed by, for example, mixing powdery alumina and water, forming the mixture into a predetermined shape, and curing and drying.

A refractory layer 14 and a heat insulating layer 16 are sequentially located on the outer side of the molten metal storage container 12, and the outer surface of the molten metal storage container 12 covers the bottom surface, the side surface, and the upper surface with the iron skin 18. The refractory layer 14 is formed by mixing alumina and other refractories with water, forming and drying. The heat insulating layer 16 is configured by attaching a fire-resistant fabric.

The molten metal holding chamber 20, which is an internal space of the molten metal storage container 12, has a hot water outlet 24 at the top, and the hot water outlet 24 is configured by a cylindrical stalk 26. The molten metal holding chamber 20 includes a tube heater 28 on the side wall portion, and can hold the molten metal stored therein within a certain temperature range. The molten metal holding chamber 20 is provided with an air supply port 21 and an exhaust port 22 at the upper part, and can supply and exhaust pressurized gas into the molten metal holding chamber.

The molten metal storage container 12 is provided with a recess 8 at the bottom, and the plate-like member 4 is installed in the recess 8 via a filler 6 such as alumina cement. The plate-like member 4 covers the bottom of the molten metal storage container 12 that is substantially directly below the hot water outlet 24, and the entire bottom may be covered. The plate-like member 4 is made of, for example, silicon carbide ceramics or fine ceramics, and has a thickness of about 10 to 40 mm, for example. The depression 8 only needs to have a depth and a width that allow the plate-like member 4 to be installed.

The plate-like member 4 and / or the depression 8 does not exclude a configuration in which the cross-sectional shape is a trapezoid as shown in FIGS. By configuring the cross-sectional shape of the plate-like member 4 and / or the depression 8 to be trapezoidal, it is possible to prevent the plate-like member 4 from being lifted from the depression 8. In addition, the structure which prevents floating by other methods, such as pressing the plate-shaped member 4 with a jig | tool from the top, is not excluded from this invention.

Next, an operation method according to the first embodiment will be described with reference to FIG.

In this operation method, the molten metal holding chamber 20 is filled with the molten metal in advance.
First, a pressurized gas such as an inert gas such as argon or nitrogen is fed into the molten metal holding chamber 20 through the air supply port 21 by a pressurizing device (not shown). At this time, since the molten metal storage container 12 is formed of a material having air permeability such as an alumina-based amorphous refractory material, the pressurized gas enters into the material constituting the molten metal storage container 12.

The pressurized gas sent into the molten metal holding chamber 20 pressurizes the liquid level M of the molten metal, and the molten metal rises in the stalk 26 and is formed in a casting mold (not shown) through the hot water outlet 24. Press-fitted into the cavity.

  After the completion of casting, the supply of the pressurized gas from the air supply port 21 is stopped, and the pressurized gas in the molten metal holding chamber 20 is exhausted from the exhaust port 22. At this time, the pressurized gas held in the molten metal storage container 12 is released into the molten metal, the refractory layer 14 and / or the heat insulating layer 16. At this time, since the porosity of the plate-like member 4 is lower than the material constituting the molten metal storage container 12, the pressurized gas can be released into the molten metal from the surface with which the plate-like member 4 contacts via the filler 6. The refractory layer 14 made of a material having a higher porosity than the molten metal storage container 12 and / or discharged from the portion where the plate-like member 4 is not in contact into the molten metal, or located outside the molten metal storage container 12 and / or It is discharged as bubbles into the heat insulating layer 16. The bubbles released into the molten metal from the portion where the plate-like member 4 is not in contact rise while oxidizing the surrounding molten metal. However, since the bubbles are discharged while avoiding almost directly below the hot water outlet 24, the bubbles enter the stalk 26. It becomes difficult to flow in.

In the step of supplying the pressurized gas to the molten metal holding chamber 20 again, since the amount of bubbles (oxide) flowing into the stalk 26 is small, the bubbles (oxide) into the molten metal pressed into the cavity through the hot water outlet 24. The amount of inflow also decreases.
In this way, it is possible to reduce the amount of bubbles (oxide) flowing into the molten metal injected into the cavity.

Further, since the total amount of bubbles released from the molten metal storage container 12 to the molten metal is reduced by the amount released from the molten metal storage container 12 to the refractory layer 14 and / or the heat insulating layer 16, it is compared with the case where there is no plate-like member 4. As a result, the total amount of bubbles released into the molten metal can be reduced.

As a second embodiment, the internal space of the molten metal storage container 12 can be partitioned into a molten metal holding chamber 20 and a pressurizing chamber 30.

FIG. 5 is an overall view of the second embodiment.

Between the molten metal holding chamber 20 and the pressurizing chamber 30, an elevating shut-off valve 34 that opens and closes the molten metal flow path port 32 is provided, and the elevating shut-off valve 34 is connected to an elevating drive mechanism by pneumatic pressure or the like. Be controlled. The pressurizing chamber is provided with a pressurizing chamber tube heater 31 and can hold the molten metal stored therein within a certain temperature range.

In the second embodiment, it is possible to simultaneously open and close the replenishing port lid 35 and inject pressurized gas into the pressurizing chamber 30 with the shut-off valve 34 closed, thereby increasing production efficiency. Is possible.

The pressurized gas penetrates into the material constituting the molten metal storage container 12 and is held for a certain period of time and then released into the molten metal as a bubble, but from a position just below the hot water outlet 24 where the plate-like member 4 is installed. Does not release bubbles. Therefore, as in the first embodiment, it is possible to prevent bubbles from flowing into the mold cavity from the hot water outlet 24 and causing the product quality to deteriorate.

As a third embodiment, the internal space of the molten metal storage container 12 is partitioned into a molten metal holding chamber 20 and a pressurized chamber 30 by a shutoff valve 34, and the pressurized chamber 30 is subjected to pressure on the upper surface of the molten metal with compressed gas. It is also possible to divide into the pressurizing part 36 to be made into the hot water supply part 38 which pours the pressurized molten metal into the cavity of a metal mold | die.

FIG. 6 is an overall view of the third embodiment.

  The pressurizing part 36 and the tapping part 38 are in communication with each other at the bottom, and a pressurizing tube 40 that is a heat-resistant integrally fired product is attached to the inner surface of the pressurizing part. A tapping pipe 42 that is an integrally fired product is attached.

The pressurizing tube 40 is formed of a non-breathable material such as fine ceramics or a material having some breathability such as silicon carbide ceramics.

  When the pressurizing tube 40 is formed of a non-breathable material, the intrusion of the pressurized gas into the material constituting the molten metal storage container 12 and the release of bubbles into the molten metal can be basically prevented. The plate-like member 4 is also installed when fine ceramics are cracked or cracked due to a physical shock during heat shock and / or maintenance, etc., and the air permeability of the pressure tube 40 is lost. As a result, bubbles are not generated from directly below the outlet 24 where the plate-like member 4 is installed. Therefore, as in the first and second embodiments, it is possible to prevent bubbles from flowing into the mold cavity from the hot water outlet 24 and causing a reduction in product quality.

Further, when the pressurizing tube 40 is formed of a material having some air permeability, the pressurized gas enters the material constituting the molten metal storage container 12 and is held for a certain period of time and then released as bubbles to the molten metal. However, bubbles are not released from substantially directly below the hot water outlet 24 where the plate-like member 4 is installed. Therefore, as in the first and second embodiments, it is possible to prevent bubbles from flowing into the mold cavity from the hot water outlet 24 and causing a reduction in product quality.

In the third embodiment, similarly to the second embodiment, it is possible to simultaneously open and close the supply port lid 35 and inject pressurized gas into the pressurizing chamber 30 with the shut-off valve 34 closed. It is possible to increase production efficiency.

DESCRIPTION OF SYMBOLS 1 ... Molten metal holding furnace 4 ... Plate-shaped member 6 ... Filler 8 ... Indentation 12 ... Melt container 14 ... Refractory layer 16 ... Heat insulation layer 18 ... Iron skin 20 ... Molten metal holding chamber 21 ... Supply port 22 ... Exhaust port 24 ... Hot water outlet 26 ... Stoke 28 ... Tube heater 30 ... Pressurizing chamber 31 ... Pressurizing chamber tube heater 32 ... Molten flow path port 34 ... Elevating shut-off valve 35 ... Replenishing port cover 36 ... Pressurizing part 38 ... Hot water part 40 ... Pressurizing pipe 42 ... Tapping pipe M ... Molten liquid level

Claims (4)

In a molten metal holding furnace for low-pressure casting having a molten metal storage container made of a material having air permeability, a plate-shaped member made of a material having a lower porosity than the molten metal storage container is provided at the bottom of the molten metal storage container. By arranging it so that it is directly underneath, the gas that has been released into the molten metal after entering the material constituting the molten metal storage container and that has become bubbles flows into the molten metal injected into the mold from the outlet. Prevents molten metal holding furnace for low pressure casting. 2. The molten metal holding furnace for low pressure casting according to claim 1, wherein the plate member is made of ceramics. 2. The low pressure casting molten metal holding furnace according to claim 1, wherein the molten metal holding furnace includes a shut-off valve that opens and closes a molten metal flow passage opening located between the molten metal holding chamber and the pressurizing chamber. In the invention according to claim 1 and 3, in the molten metal holding furnace, the pressurizing chamber has a pressurizing unit that applies pressure to the upper surface of the molten metal with a compressed gas, and the pressurized molten metal is poured into the cavity of the mold. A molten metal holding furnace for low-pressure casting, which is divided into a hot-water supply section, and a pressure tube which is a heat-resistant integral fired product is attached to the inner surface of the pressure section.