JP4422045B2 - Molten metal holding furnace for low pressure casting and molten metal supply method there - Google Patents

Description

  The present invention relates to a low pressure casting molten metal holding furnace suitable for manufacturing, for example, aluminum and aluminum alloy castings, and a molten metal supply method therefor.

Conventionally, various molten metal holding furnaces are known (see, for example, Patent Documents 1, 2, and 3).
JP 2001-321914 A JP-A-11-138250 JP-A-3-258449

  In Patent Document 1, a molten metal holding chamber and a pressurizing chamber communicate with each other via a molten metal flow channel opening, and the molten metal flow channel port is opened and closed by a shut-off valve. There has been disclosed a molten metal holding furnace for low pressure casting in which a molten metal is filled in a cavity of a mold through stalk by pressing.

  In Patent Document 2, a melt holding chamber and a pressurizing chamber composed of a pressurizing unit and a tapping unit communicate with each other via a melt channel port, and the melt channel port is opened and closed by a shutoff valve so that the melt channel port is closed. Hold the molten metal for low-pressure casting by supplying the gas for pressurization into the pressurizing part under pressure and pressurizing the surface of the molten metal so that the molten metal is filled in the cavity of the mold through the outlet of the molten metal part. A furnace is disclosed.

  In the molten metal holding chamber of the above-described type of low pressure casting molten metal holding furnace, initially, a plurality of, usually 20 to 30 shots (casting) equivalent amount of molten metal is stored and pressurized from the molten metal holding chamber after casting. The supply of the molten metal for one shot to the chamber is performed using the difference in level between the molten metal surfaces in the open state of the molten metal flow passage opening. Regarding the molten metal surface height at the start of operation or when the molten metal is replenished to the molten metal holding chamber, the molten metal surface height is higher than the molten metal surface height in the pressurizing chamber and the same height as the molten metal surface height in the pressurized chamber. There is a method to make it.

  In Patent Document 3, a pressurization chamber corresponding to the molten metal holding chamber and a pumping chamber corresponding to the pressurization chamber communicate with each other via a melt flow passage opening, and the melt flow passage opening is opened and closed by a shutoff valve. In a state where the molten metal flow path port is opened, a pressurizing gas is supplied into the pressure chamber, the pressure of the molten metal is pressurized, and the molten metal is allowed to flow into the pumping chamber until reaching a certain molten metal level. A melt holding furnace for die casting that supplies a predetermined amount of molten metal to the injection sleeve through a hot water supply pipe and a hot water supply port by supplying a pressurizing gas into the pumping chamber in a closed state and pressurizing the surface of the molten metal. Is disclosed.

  In the case of the molten metal holding furnace for low-pressure casting described in Patent Document 1, a space having a height equal to the height difference between the upper limit height and the lower limit height of the pressurizing chamber is minimal above the hot surface of the pressurization chamber. Necessary. Further, in the case of the molten metal holding furnace for low-pressure casting described in Patent Document 2, a space having a height equal to the height difference between the upper limit hot metal surface height of the pressurizing unit and the lower limit hot metal surface height is minimum above the hot water surface of the pressurizing unit. Limited is required. For this reason, in the case of the molten metal holding furnace for low-pressure casting described in Patent Document 1, there is a problem that the stalk becomes longer and the pressurizing chamber becomes larger. Moreover, in the case of the molten metal holding furnace for low-pressure casting described in Patent Document 2, there is a problem that the pressurizing part is enlarged. Furthermore, in the case of the molten metal holding furnace for low pressure casting described in each of Patent Documents 1 and 2, after filling the molten metal into the cavity of the mold, the space above the molten metal surface of the pressurizing chamber or the pressurizing unit is formed. When the pressure is lowered to the atmospheric pressure, a high-temperature pressurizing gas is released to the atmosphere, so that there is a problem that the loss of heat energy is large.

  By the way, in both the holding furnaces, the molten metal stored in the molten metal holding chamber is supplied to the pressurizing chamber for each casting, and this casting is repeated several times until the molten metal level in the molten metal holding chamber reaches the lower limit level. It is. That is, as the casting level is repeated, the level of the molten metal in the pressurizing chamber or the extraction section decreases, so that the time interval for filling the mold cavity with the molten metal becomes longer after the initial casting, and the production efficiency decreases. In addition to this, the residence time of the molten metal in the stalk or the outlet becomes longer. As a result, since the temperature of the molten metal filled in the mold is lowered, there arises a problem that it is difficult to obtain a casting with a constant quality.

  On the other hand, in the case of the molten metal holding furnace for die casting described in Patent Document 3, the pressurized chamber is added to the molten metal supply from the pressurized chamber corresponding to the molten metal holding chamber to the pumping chamber corresponding to the pressurized chamber. Although there is a different aspect from Patent Documents 1 and 2, the method for supplying molten metal from the pressurizing chamber to the pumping chamber in Patent Document 3 is described in Patent Document 1 or 2. When applied to a holding furnace, there is a problem that a molten steel surface swinging phenomenon occurs in the pressurizing chamber, which hinders the stable supply of the molten metal to the pressurizing chamber, so that it is difficult to obtain a casting with a constant quality.

  Therefore, as a result of repeated various experiments and examinations, the inventor of the present application has found that the occurrence of the oscillation phenomenon occurs at the time when communication between the molten metal holding chamber and the pressurizing chamber is started, that is, when the shutoff valve starts to rise The present inventors have found that it is related to and caused by the pressure in the molten metal holding chamber.

  The present invention has been made on the basis of the above-mentioned knowledge with the object of eliminating such conventional problems, and is capable of holding a molten metal for low-pressure casting that enables downsizing, reduction of thermal energy loss, and stabilization of casting product quality. It is intended to provide a furnace and a molten metal supply method there.

  In order to solve the above-mentioned problems, the first invention includes a molten metal holding chamber and a pressurizing chamber that are arranged in parallel and communicated via an openable and closable molten metal flow port, and is stored in a closed state of the molten metal flow port. The molten metal in the molten metal holding chamber is supplied from the molten metal holding chamber to the pressurizing chamber under the open state of the molten metal flow port, and then pressurized in the pressurized chamber under the closed state of the molten metal flow port. In the molten metal holding furnace for low-pressure casting formed so that the molten metal in the pressurizing chamber can be filled into the cavity of the mold, the molten metal holding chamber is opened to the pressurizing chamber when the molten metal flow port is opened prior to the supply. A preload that does not cause a back flow in the molten metal flowing into the molten metal holding port is applied to the molten metal holding chamber under the closed state of the molten metal flow port, and the pressurized state in the molten metal holding chamber is also applied during the supply with the molten metal flow port opened. Gas supply for pressurization introducing gas for pressurization It was used as a structure provided on the melt holding chamber.

  In the second invention, in addition to the structure of the first invention, the filling is performed through stalk arranged from below the mold to below the molten metal surface.

  According to a third aspect of the invention, in addition to the configuration of the first aspect, the pressurizing chamber has a lower flow passage that communicates with the molten metal flow port, a pressurization portion that opens at the bottom to the lower flow passage, and the pressurization portion. Are separated and arranged side by side, and are composed of a tapping part opened to the lower flow passage at the bottom, the pressurizing is performed in the pressurizing part, and the filling is performed from the tapping part.

  According to a fourth aspect of the present invention, the molten metal in the molten metal holding chamber stored under the closed state of the openable and closable molten metal flow port at the bottom of the molten metal holding chamber is communicated with the molten metal holding chamber via the molten metal flow port. Low pressure casting in which the molten metal in the pressurizing chamber is filled with the molten metal in the pressurizing chamber by supplying the molten metal in the pressurizing chamber with the molten metal flow port open and then pressurizing the pressurizing chamber with the molten metal flow port closed. In the molten metal supply method in the molten metal holding furnace, prior to the supply, when the molten metal flow port is opened, a preload that does not cause a reverse flow in the molten metal flowing from the molten metal holding chamber to the pressurizing chamber is applied to the molten metal flow port. The molten metal holding chamber is supplied in the closed state, and the pressurized state in the molten metal holding chamber is maintained even during the supply in the open state of the molten metal circulation port.

  According to the present invention, when the molten metal is supplied from the molten metal holding chamber to the pressurizing chamber, the occurrence of the fluctuation phenomenon of the molten metal in the pressurizing chamber is suppressed by preventing the backflow or pulsation of the molten metal. Mixing of the oxide into the molten metal is reduced, and there is an effect that good purity of the molten metal is maintained.

  In addition, since the level of the hot water surface can be accurately grasped by suppressing the swinging phenomenon and the constant hot water surface can be reliably secured, the constant hot water surface position can be set near the ceiling in the pressurizing chamber. In addition to reducing the internal volume of the pressure chamber and reducing the stalk length, it is possible to reduce the size of the molten metal holding furnace for low-pressure casting, and also to suppress the decrease in the molten metal temperature. The effects such as being done.

Next, embodiments of the present invention will be described with reference to the 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 for low pressure casting includes a molten metal holding chamber 10 and a pressurizing chamber 20 arranged in parallel. Both chambers communicate with each other through the molten metal flow path port 30.

  The molten metal holding chamber 10 is provided with a holding chamber lid 11 at the top, a tube heater 12 and a temperature sensor 13 on the side surface portion of the inner wall made of a refractory, and the molten metal supply port provided through the holding chamber lid 11. The molten metal supplied from 14 and stored therein is formed so as to be able to be held within a certain temperature range. Further, the molten metal holding chamber 10 communicates with a pressurizing gas supply port 15, and the pressurizing gas from the pressurizing gas supply chamber can be pressurized, and the pressure is detected by a pressure sensor 16. Furthermore, a level sensor 17 for detecting the upper limit level of the hot water surface is provided below the holding chamber lid 11.

  The pressurizing chamber 20 is provided with a pressurizing chamber lid 21 at the top, a tube heater 22 on the side surface portion of the inner wall made of refractory, and communicates with the pressurizing gas supply port 23, and the pressurizing gas from here The interior can be pressurized. A lower die base 24 is fixed to the upper surface of the pressurizing chamber lid 21, and a cylindrical stalk 25 is provided through the pressurizing chamber lid 21 from the lower die base 24. A mold 26 is fixed on the lower die base 24, and the cavity 27 and the pressurizing chamber 20 of the mold 26 are located inside the gate 28 and the stalk 25 formed between the stalk 25 and the cavity 27. It communicates through the space. Further, a level sensor 29 for detecting the level of the constant hot water surface when the molten metal is supplied is provided below the pressurizing chamber lid 21 so that the tip thereof is positioned in the vicinity of the ceiling.

  The molten metal flow passage port 30 is provided at the bottom of the molten metal holding chamber 10, and the molten metal holding chamber 10 and the pressurizing chamber 20 can communicate with each other through the molten metal flow passage port 30. A shut-off valve that opens and closes the molten metal flow passage opening 30 through the holding chamber lid 11 in an airtight and elevating manner above the valve seat 31 formed at the opening of the molten metal flow passage opening 30 to the molten metal holding chamber 10. 32 is provided. That is, the shut-off valve 32 presses against the valve seat 31 when lowered and closes the molten metal flow path port 30, and moves away from the valve seat 31 when opened to open the molten metal flow path port 30.

  In FIG. 1, a two-dot chain line U indicates the upper limit level of the molten metal surface in the molten metal holding chamber 10, and a two-dot chain line L indicates the lower limit level of the molten metal surface.

Next, the molten metal supply method in the molten metal holding furnace for low pressure casting according to the present invention will be described by applying it to the molten metal holding furnace 1 for low pressure casting constructed as described above.
The molten metal is supplied from the molten metal supply port 14 into the molten metal holding chamber 10 until the molten metal level reaches the molten metal surface upper limit level U while the molten metal flow passage port 30 is in the raised position. The molten metal flow path port 30 is closed. And the gas for pressurization is introduce | transduced in the molten metal holding | maintenance chamber 10 from the gas supply port 15 for a pressurization, the pre-load of 10-14 kPa is given in a chamber, and this pressure state is maintained. The preload is a pressure necessary to prevent a backflow from occurring in the molten metal flowing toward the pressurizing chamber 20 when the molten metal is supplied from the molten metal holding chamber 10 to the pressurizing chamber 20 later. The preload value varies depending on the internal volume of the molten metal holding chamber 10 and the pressurizing chamber 20, the type of molten metal, and the like, and is determined experimentally prior to actual operation. The preload can be a pressure value corresponding to the last shot or a pressure value corresponding to each shot.

  When preload is applied to the molten metal holding chamber 10, the shutoff valve 32 is raised to open the molten metal flow passage port 30, and the inflow of molten metal from the molten metal holding chamber 10 to the pressurizing chamber 20 via the molten metal flow passage port 30 is started. Then, after maintaining the pressurized state in the molten metal holding chamber 10 and continuing the inflow of molten metal until a level surface 29 is detected by the level sensor 29 provided in the pressurized chamber 20, the shutoff valve 32 is lowered. While closing the molten metal flow path port 30, the introduction of the pressurizing gas is stopped and the inflow of the molten metal is stopped. Note that the pressurization state is not necessarily maintained the same as the pressurization state at the time of preloading, and may be appropriately maintained in an arbitrary pressurization state. For example, when reducing the rising speed of the hot water surface in the latter half of the inflow period into the pressurizing chamber 20, the pressure in the pressurizing chamber 20 is decreased or the amount of pressurizing gas introduced is decreased.

  When the molten metal supply port 30 is closed, under this closed state, a pressurized gas such as dry air is introduced into the pressurized chamber 20 from the pressurized gas supply port 23 to pressurize the molten metal in the pressurized chamber 20. As a result, the level of the molten metal in the stalk 25 is pushed up, and the molten metal is filled into the cavity 27 of the mold 26.

  When a predetermined time elapses when the molten metal at the pouring gate 28 is solidified while maintaining the state of filling the molten metal, the introduction of the pressurizing gas is stopped and the pressure in the pressurizing chamber 20 is lowered to or near the atmospheric pressure. .

  Subsequently, after the upper mold part and the horizontal mold part of the mold 26 are opened and the cast product is taken out, the upper mold part and the horizontal mold part of the mold 26 are again closed and integrated. The shot operation is complete.

  Thereafter, the molten metal is supplied from the molten metal holding chamber 10 to the pressurizing chamber 20 for each shot, and the above-described operations are repeated. When the molten metal level in the molten metal holding chamber 10 falls to the lower limit level L, the molten metal supply port A new molten metal is supplied from 14 to the molten metal holding chamber 10 until the upper limit level U is reached.

  FIG. 2 shows a molten metal holding furnace 2 for low pressure casting according to a second embodiment of the present invention. In the molten metal holding furnace 2 for low pressure casting, portions common to the molten metal holding furnace 1 for low pressure casting shown in FIG. Are given the same numbers and their explanation is omitted.

  In the molten metal holding furnace 2 for low pressure casting, the molten metal is supplied to the molten metal holding chamber 10 from a molten metal supply port (not shown). The pressurizing chamber 20 is composed of a pressurizing unit 20A, a tapping unit 20B, and a lower flow passage 20C. The pressurizing unit 20A and the tapping unit 20B are separated from each other, and the lower flow passage 20C is pressurized. The bottom portions of the portion 20A and the hot water discharge portion 20B are communicated with each other and communicated with the molten metal flow passage port 30.

  With such a configuration, by introducing a pressurization gas such as dry air from the pressurization gas supply port 23 into the pressurization unit 20A under the closed state of the melt flow passage port 30, the melt in the pressurization unit 20A is pressurized. The level of the molten metal in the hot water discharge section 20B is pushed up, and the molten metal is filled in the cavity 27 of the mold 26. The molten metal holding furnace 2 for low pressure casting is in the stalk 25 in the molten metal holding furnace 1 for low pressure casting. Is regarded as the tapping part 20B, and the portion inside the pressurizing chamber 20 and outside the stalk 25 is regarded as the pressurizing part 20A, the low pressure casting molten metal holding furnaces 1 and 2 are substantially the same. Therefore, with regard to the molten metal supply method in the molten metal holding furnace 2 for low pressure casting, if the inside of the stalk 25 is regarded as the tapping part 20B and the part inside the pressurizing chamber 20 and outside the stalk 25 is regarded as the pressurizing part 20A, It becomes substantially the same.

  The molten metal holding furnace for low pressure casting and the molten metal supply method therefor according to the present invention are suitable for the production of, for example, aluminum and aluminum alloy castings.

It is sectional drawing of the molten metal holding furnace for low pressure casting which concerns on 1st Embodiment of this invention. It is sectional drawing of the molten metal holding furnace for low pressure casting which concerns on 2nd Embodiment of this invention.

Explanation of symbols

1, 2 Low pressure casting melt holding furnace 10 Molten holding chamber 11 Holding chamber lid 12 Tube heater 13 Temperature sensor 14 Molten metal supply port 15 Pressurizing gas supply port 16 Pressure sensor 17 Level sensor 20 Pressurizing chamber 20A Pressurizing unit 20B 20C Lower flow passage 21 Pressurizing chamber lid 22 Tube heater 23 Pressurizing gas supply port 24 Lower die base 25 Stoke 26 Mold 27 Cavity 28 Pouring port 29 Level sensor 30 Melting channel port 31 Valve seat 32 Shut-off valve U Hot water surface upper limit level L Hot water Surface lower limit level

Claims (4)

A molten metal holding chamber and a pressurizing chamber, which are arranged in parallel and communicated via an openable and closable molten metal flow port, and the molten metal stored in the molten metal holding chamber in a closed state of the molten metal flow port is stored in the molten metal flow port. After being supplied from the molten metal holding chamber to the pressurizing chamber in an open state, the molten metal in the pressurizing chamber is filled into the mold cavity by pressurizing the pressurizing chamber with the molten metal circulation port closed. In the low pressure casting molten metal holding furnace formed possible,
Prior to the supply, when the molten metal flow port is opened, a preload that does not cause a reverse flow in the molten metal flowing from the molten metal holding chamber to the pressurizing chamber is generated in the molten metal holding chamber under the closed state of the molten metal flow port. And a pressurizing gas supply port for introducing a pressurizing gas for maintaining a pressurized state in the molten metal holding chamber even when the molten metal circulation port is supplied is provided in the molten metal holding chamber. A molten metal holding furnace for low pressure casting.   The molten metal holding furnace for low-pressure casting according to claim 1, wherein the filling is performed through a stalk arranged from below the mold to below the molten metal surface. The pressure chamber is
A lower flow passage leading to the molten metal distribution port;
A pressurizing part opened to the lower flow passage at the bottom,
Separated from the pressurizing part, it comprises a tapping part opened at the bottom flow path at the bottom,
The molten metal holding furnace for low pressure casting according to claim 1, wherein the pressurization is performed in the pressurization unit, and the filling is performed from the tapping unit. The molten metal in the molten metal holding chamber stored in a closed state of the openable and closable molten metal flow port at the bottom of the molten metal holding chamber communicates with the molten metal holding chamber through the molten metal flow port, and is connected to the pressurizing chamber arranged in parallel. In a molten metal holding furnace for low-pressure casting, which is supplied with an open state of a molten metal flow port and then pressurizes the pressurized chamber under a closed state of the molten metal flow port to fill the mold cavity with the molten metal in the pressurized chamber. In the molten metal supply method,
Prior to the supply, when the molten metal flow port is opened, a preload that does not cause a reverse flow in the molten metal flowing from the molten metal holding chamber to the pressurizing chamber is generated in the molten metal holding chamber under the closed state of the molten metal flow port. Give,
The method for supplying molten metal in a molten metal holding furnace for low-pressure casting is characterized in that the pressurized state in the molten metal holding chamber is maintained even during the supply in the open state of the molten metal circulation port.

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