Molten Metal Holding Furnace for 2-Chamber Low-Pressure Casting

Abstract

To provide a two-chamber type low-pressure casting melt-preserving furnace allowed to reduce the usage of pressurized gas and inhibit the problem resulting from the pressurized gas upon releasing a pressurizing unit to the atmosphere.SOLUTION: A two-chamber type low-pressure casting melt-preserving furnace includes melt-preserving and melt-pressurizing chambers connected for communication through a melt flow-passage opening, in which the melt-pressurizing chamber comprises a pressurizing unit and a melt-delivering unit and the melt-preserving and melt-pressurizing chambers have a furnace inner wall 2 composed of a melt-reservation container 4 and a heat-insulation layer 5, so as to feed melt into a cavity of a metal mold through the melt-delivering unit by introducing pressurized gas into a space of the pressurizing unit. The pressurizing unit for the melt-reservation container 4 is demarcated through a joint 6 into an upper melt-reservation container 4A and a lower melt-reservation container 4B, so that the joint 6 has a furnace-inside joining end positioned below a lower-limit surface of melt. The pressurizing unit for the heat-insulation layer 5 is demarcated into a first heat-insulation layer 5A as a pressurizing region and a second heat-insulation layer 5B as a non-pressurizing region through a pressure bulkhead member 7 having one end positioned in the joint 6 and the other end connected / fixed to a furnace shell at the pressurizing unit.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a molten metal holding furnace for two-chamber low-pressure casting, which is suitable for manufacturing castings such as aluminum alloys by the low-pressure casting method. Specifically, it relates to the furnace inner wall structure of the pressurizing part of a two-chamber low-pressure casting molten metal holding furnace in which the molten metal pressurizing chamber is composed of a tapping part and a pressurizing part.

Background Art

[0002] As a molten metal holding furnace for two-chamber low-pressure casting composed of a molten metal holding chamber and a molten metal pressurizing chamber, Patent Document 1 discloses that the molten metal holding chamber and the molten metal pressurizing chamber are communicatively connected via an openable and closable molten metal flow path provided on the furnace bottom of the molten metal holding chamber. The molten metal pressurizing chamber includes a pressurizing part and a tapping part that communicate at the bottom. A two-chamber low-pressure casting molten metal holding furnace is disclosed in which a pressurized gas is introduced into the space of the pressurizing part and the molten metal is supplied to the cavity of the mold through the tapping part.

[0003] In the casting operation of the two-chamber low-pressure casting molten metal holding furnace, the molten metal flow path is opened to introduce the molten metal in the molten metal holding chamber into the molten metal pressurizing chamber. When the molten metal level sensor installed in the pressurizing part detects that the molten metal level in the molten metal pressurizing chamber has reached a predetermined height, after closing the molten metal flow path, a pressurized gas such as dry air is introduced into the pressurizing part, and the molten metal maintained at a predetermined temperature is supplied to the cavity of the mold through the tapping part. After a predetermined time has elapsed, the pressurizing part is opened to the atmosphere repeatedly. When the molten metal in the molten metal holding chamber has decreased to a predetermined amount, the molten metal supply port of the molten metal holding chamber is opened to supply new molten metal to the molten metal holding chamber.

[0004] The furnace inner wall of the molten metal holding furnace for two-chamber low-pressure casting consists of a molten metal storage container made of an integrally fired mass of monolithic refractory material that is in direct contact with the molten metal, and a heat insulation layer such as a heat insulation board located on the back side of the molten metal storage container, that is, between the furnace shell (iron sheet) and the molten metal storage container. For example, Patent Document 2 discloses a molten metal storage tank consisting of a molten metal storage container made of a silicon carbide-based monolithic refractory material, and a heat insulation layer in which a ceramic fiber layer, an alumina-resistant refractory board (ceramic fiber blanket), a high-temperature heat-resistant board (calcium silicate heat insulation board), a filler (porous granular refractory material), and a low-temperature heat insulation board (perlite board) are sequentially laminated on the outer surface of the molten metal storage container. Note that an alumina-based monolithic refractory material is also used as the monolithic refractory material of the molten metal storage container.

[0005] For the furnace inner wall of the molten metal holding furnace for two-chamber low-pressure casting, first, the heat insulation layer is constructed, then a formwork is installed so as to face the heat insulation layer, and the monolithic refractory material kneaded with water or the like is poured into the space formed by the formwork and the heat insulation layer, left for a predetermined time, demolded, and dried and fired according to a predetermined heating curve to form the molten metal storage container.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the case of the molten metal holding furnace for two-chamber low-pressure casting of Patent Document 1, since the furnace inner wall has air permeability and the molten metal storage container is an integrally fired mass of monolithic refractory material, there are the following problems.

[0008] First, when introducing pressurized gas into the pressurizing section and supplying molten metal into the cavity of the mold through the molten metal discharging section, the retention region of the pressurized gas in the furnace inner wall of the molten metal pressurizing chamber becomes extensive, which not only requires a large amount of pressurized gas but also results in a long pressurizing time. In addition, the exhaust time when the pressurizing section is opened to the atmosphere becomes long, leading to poor productivity. Second, when the pressurizing section is opened to the atmosphere, the pressurized gas retained in the furnace inner wall flows out from the surface of the furnace inner wall of the pressurizing section into the molten metal, causing a foaming phenomenon, which leads to the generation of a large amount of oxides and the early deterioration of the molten metal. On the other hand, these oxides accumulate on the surface of the molten metal, making it difficult to detect the constant molten metal level (predetermined height) by the molten metal surface sensor in the pressurizing section. Third, the operation of removing the generated oxides becomes frequent. Fourth, when removing oxides and the like adhering to the surface of the furnace inner wall of the pressurizing section, if the molten metal storage container is damaged, it is impossible to repair.

[0009] The present invention has been made in view of such conventional problems, and an object thereof is to provide a two-chamber type low-pressure casting molten metal holding furnace that can reduce the amount of pressurized gas introduced into the pressurizing section of the molten metal pressurizing chamber and suppress problems caused by the pressurized gas when the pressurizing section is opened to the atmosphere.

Means for Solving the Problems

[0010] As a first means for solving the above problems, the present invention provides a two-chamber type low-pressure casting molten metal holding furnace in which a molten metal holding chamber and a molten metal pressurizing chamber are communicatively connected through an openable and closable molten metal flow path opening provided in the furnace bottom of the molten metal holding chamber. The molten metal pressurizing chamber includes a pressurizing section and a molten metal discharging section that communicate at the bottom. The furnace inner walls of the molten metal holding chamber and the molten metal pressurizing chamber are composed of a molten metal storage container made of an amorphous refractory material and a heat insulating layer located on the back side of the molten metal storage container. Pressurized gas is introduced into the space of the pressurizing section to supply the molten metal maintained at a predetermined temperature to the cavity of the mold through the molten metal discharging section, wherein the pressurizing section of the molten metal storage container is partitioned into an upper molten metal storage container and a lower molten metal storage container through a joint portion, and the inner joint end of the joint portion on the furnace side is located below the lower limit molten metal surface of the molten metal. The pressurized portion of the heat insulation layer is partitioned into a first heat insulation layer in the pressurized region and a second heat insulation layer in the non-pressurized region via a pressure partition member having one end located within the joint portion and the other end connected and fixed to the furnace shell of the pressurized portion.

[0011] It is preferable that the inner furnace joint end of the joint portion is located near the lower limit of the molten metal surface of the molten metal.

[0012] It is preferable that the pressure partition member is a steel plate.

Advantages of the Invention

[0013] According to the invention of claim 1, when introducing a pressurized gas into the pressurized portion, the pressurized gas only flows into the upper molten metal storage container and the first heat insulation layer, and does not flow into the lower molten metal storage container and the second heat insulation layer. Therefore, the usage amount of the pressurized gas and the pressure increase time can be reduced. When the pressurized portion is opened to the atmosphere, the discharge amount of the pressurized gas into the molten metal is reduced, and the time for opening to the atmosphere can be shortened. Since the discharge amount of the pressurized gas can be reduced, the generation of foreign matters such as oxides can be suppressed, the cleanliness of the molten metal can be maintained for a long time, the deposition of oxides on the molten metal surface can be suppressed, the constant molten metal surface can be stably managed and suppressed for a long time, and furthermore, the interval between oxide removal operations can be extended. By shortening the pressure increase time and the time for opening to the atmosphere and extending the interval between oxide removal operations, productivity can be improved. The adherent substances such as oxides are on the surface of the upper molten metal storage container, and repair measures can be taken when damaged.

[0014] According to the invention of claim 2, the pressurized region is reduced, and the usage amount of the pressurized gas can be reduced.

[0015] According to the invention of claim 3, since the pressure partition member is a steel plate, it has the effect of improving the durability and manufacturability of the pressure partition member.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0018] FIG. 1 shows a two-chamber type molten metal holding furnace for low-pressure casting (hereinafter simply referred to as "molten metal holding furnace") 1 according to an embodiment of the present invention. The molten metal holding furnace 1 includes a molten metal holding chamber 10 and a molten metal pressurizing chamber 20, and both chambers are communicatively connected via a molten metal flow path 30. The molten metal pressurizing chamber 20 includes a pressurizing portion 20a and a tapping portion 20b that communicate at the bottom. The pressurizing portion 20a and the tapping portion 20b of the molten metal pressurizing chamber 20 are arranged in the X direction in FIG. 1, and the pressurizing portion 20a of the molten metal holding chamber 10 and the molten metal pressurizing chamber 20 are arranged in the Y direction in FIG. 1, so that the molten metal holding furnace 1 is arranged in an L shape when viewed from a plane.

[0019] As shown in FIG. 2, the furnace inner wall 2 of the molten metal holding furnace 1 is composed of a molten metal storage container 4 for storing molten metal inside the furnace shell 3 and a heat insulating layer 5 located on the back side of the molten metal storage container 4, that is, between the furnace shell 3 and the molten metal storage container 4.

[0020] The molten metal storage container 4 is made of refractory castables. As the refractory castables, aluminous materials such as the product name: ALKON CAST (Alcon Cast) manufactured by Calderys Inc. are suitable, for example.

[0021] The heat insulation layer 5 has a multi-layer heat insulation structure, and refractory heat-insulating castables and heat insulation boards such as silica-based and calcium silicate-based ones are suitable.

[0022] As shown in FIG. 3, the molten metal storage container 4 in the pressurizing portion 20a of the molten metal pressurizing chamber 20 is vertically partitioned into an upper molten metal storage container 4a and a lower molten metal storage container 4b. The lower end surface of the upper molten metal storage container 4a and the upper end surface of the lower molten metal storage container 4b form a stepped joint portion 6. From the viewpoint of reducing the amount of pressurized gas used and suppressing oxides and the like associated with this reduction, the inner furnace-side joint end of the joint portion 6 is preferably below the lower limit molten metal surface (LL) of the molten metal and as close as possible to the vicinity below the lower limit molten metal surface (LL).

[0023] The upper molten metal storage container 4a has a rectangular cylindrical shape with openings at the upper and lower ends. As shown in FIG. 4, an annular downward convex portion 6a is formed on the inner peripheral side of the lower end surface, and the upper end surface is located above the fixed molten metal surface (NL) of the molten metal. On the outer peripheral side of the upper molten metal storage container 4a, a shelf portion 6c on which a holding plate 8a of a holding member 8 described later is placed is formed.

[0024] The lower molten metal storage container 4b forms a lower portion of the pressurizing portion 20a, a molten metal outlet portion 20b, and a communication portion 20c that communicates the pressurizing portion 20a and the molten metal outlet portion 20b, and the upper ends of the pressurizing portion 20a and the molten metal outlet portion 20b are open. As shown in FIG. 4, an upward convex portion 6b is formed on the outer peripheral side of the upper end surface of the pressurizing portion 20a so as to engage with the annular downward convex portion 6a of the upper molten metal storage container 4a and form a stepped joint portion 6.

[0025] The heat insulation layer 5 in the pressurizing portion 20a of the molten metal pressurizing chamber 20 is vertically and horizontally partitioned by a pressure partition member 7 into a first heat insulation layer 5a which is a pressurized region located on the upper molten metal storage container 4a side and a second heat insulation layer 5b which is a non-pressurized region located on a part of the upper molten metal storage container 4a side and the lower molten metal storage container 4b side.

[0026] The pressure partition member 7 is formed of a steel plate, for example, a stainless steel plate (thickness: 2 to 4 mm). As shown in FIG. 5, it has an L-shaped longitudinal cross-sectional shape, is a rectangular box shape having an opening 7e at the bottom, and includes a side portion 7a composed of four side surfaces, a rectangular frame-shaped bottom portion 7b welded and joined to the lower end of the side portion 7a, a rectangular frame-shaped insertion portion 7c welded and joined to the inner edge of the bottom portion 7b, and a rectangular frame-shaped first ceiling plate 7d welded and joined to the upper end of the side portion 7a. From the viewpoint of preventing the molten metal from flowing excessively into the first heat insulation layer 5a through the gap of the joint portion 6, the plate thickness of the insertion portion 7c is preferably thinner than that of the bottom portion 7b. The side portion 7a of the pressure partition member 7 may have a circular box shape. As shown in FIG. 4, the first ceiling plate 7d is connected and fixed to the outer ceiling plate 3b of the furnace shell 3 by welding with the second ceiling plate 7f, and the ceiling of the pressure partition member 7 is formed by the first ceiling plate 7d and the second ceiling plate 7f. The insertion portion 7c of the bottom portion 7b is inserted and clamped on the outer peripheral side of the joint portion 6 between the lower end of the upper molten metal storage container 4a and the upper end of the lower molten metal storage container 4b.

[0027] As shown in FIGS. 4 and 5, the holding member 8 includes a holding plate 8a having a rectangular shape that presses against the shelf portion 6c of the upper molten metal storage container 4a and having an opening at the center, a plurality (8) of support plates 8b welded and fixed to the side portion 7a of the pressure partition member 7 such that the upper end surface is at the same height as the shelf portion 6c of the upper molten metal storage container 4a, a plurality (8) of bolts 8c welded and fixed vertically at equal intervals in the circumferential direction of the bottom portion 7b of the pressure partition member 7, and nuts 8d for fixing the holding plate 8a and the bolts 8c. By attaching and tightening the nuts 8d to the bolts 8c passing through the opening of the holding plate 8a, the upward floating of the upper molten metal storage container 4a and the displacement of the joint portion 6 are prevented.

[0028] As shown in FIG. 2, the molten metal holding chamber 10 includes a ceiling heat insulation lid 11 at the upper part and a heat insulation lid 12 for opening and closing a molten metal supply port 11a formed in the ceiling heat insulation lid 11, and an immersion tube heater 13 is disposed inside to hold the molten metal stored inside within a predetermined temperature range. Further, the molten metal stored inside the molten metal holding chamber 10 is held between an upper limit position when the supply of the molten metal is completed and a lower limit position when the supply of the molten metal starts.

[0029] As shown in FIG. 3, the molten metal pressurizing chamber 20 includes a lid 21 having an opening 21a at the upper part of the pressurizing portion 20a, and an opening / closing lid 22 is provided at the opening 21a. The lid 21 is provided with a pressurizing port 21b for introducing pressurized gas into the pressurizing portion 20a and a constant molten metal level sensor 29. The lower end of the constant molten metal level sensor 29 is located at the constant molten metal level (NL) of the molten metal in the pressurizing portion 20a, and is adapted to detect the constant molten metal level NL of the molten metal in the pressurizing portion 20a. The communication portion 20c has an immersion tube heater 24 disposed therein and holds the molten metal stored therein within a predetermined temperature range. At the molten metal outlet portion 20b, a die base 25 is fixed on the top plate 3a of the furnace shell 3, and a mold 26 is fixed on the die base 25.

[0030] Returning to FIG. 2, the molten metal flow path 30 is formed so as to communicate the bottom of the molten metal holding chamber 10 and the side surface of the pressurizing portion 20a of the molten metal pressurizing chamber 20. A valve seat 32 is formed at the molten metal flow path opening 31 on the molten metal holding chamber 10 side of the molten metal flow path 30, and above the valve seat 32, a shut-off valve 33 that vertically penetrates the ceiling heat insulating lid 11 of the molten metal holding chamber 10 and opens and closes the molten metal flow path 30 is provided. That is, the shut-off valve 33 presses the valve seat 32 when descending to close the molten metal flow path 30, and separates from the valve seat 32 when ascending to open the molten metal flow path 30.

[0031] In FIG. 4, as a connection structure between the furnace shell 3 and the pressure partition member 7, the first ceiling plate 7d of the pressure partition member 7 is welded and connected to the outer ceiling plate 3b of the pressurizing portion 20a via the second ceiling plate 7f, but it is not limited thereto. For example, the first ceiling plate 7d of the pressure partition member 7 may be welded and fixed to the furnace shell 3 below the outer ceiling plate 3b via the second ceiling plate 7f. Further, the second ceiling plate 7f may be interposed between the outer ceiling plate 3b and the inner ceiling plate 3c, and the inner ceiling plate 3c and the outer ceiling plate 3b may be fixed with bolts.

[0032] FIG. 6 shows a modified example of the joint portion 6 between the lower end surface of the upper molten metal storage container 4a and the upper end surface of the lower molten metal storage container 4b. In FIG. 6, hatching is omitted for simplicity except for the insertion portion 7c of the pressure partition member 7. In FIG. 6(a), a downward convex portion 6a is formed on the outer peripheral side of the lower end surface of the upper molten metal storage container 4a, while an upward convex portion 6b is formed on the inner peripheral side of the upper end surface of the lower molten metal storage container 4b so as to engage with the downward convex portion 6a to form a stepped shape. The insertion portion 7c of the pressure partition member 7 is inserted and sandwiched between the downward convex portion 6a of the upper molten metal storage container 4a and the upper end surface of the lower molten metal storage container 4b. In FIG. 6(b), an annular recess 6d is formed on the lower end surface of the upper molten metal storage container 4a, and an annular convex portion 6e that engages with the recess 6d is formed on the upper end surface of the lower molten metal storage container 4b. The insertion portion 7c of the pressure partition member 7 is inserted and sandwiched between the outer peripheral side lower end surface of the upper molten metal storage container 4a and the outer peripheral side upper end surface of the lower molten metal storage container 4b. In FIG. 6(c), an annular convex portion 6e is formed on the lower end surface of the upper molten metal storage container 4a, and an annular recess 6d that engages with the annular convex portion 6e is formed on the upper end surface of the lower molten metal storage container 4b. The insertion portion 7c of the pressure partition member 7 is inserted and sandwiched between the outer peripheral side lower end surface of the upper molten metal storage container 4a and the outer peripheral side upper end surface of the lower molten metal storage container 4b.

[0033] The furnace inner wall 6 of the molten metal pressurizing chamber 20a of the first embodiment is constructed by the following procedure.

[0034] First, as shown in FIG. 7, a second heat insulating layer 5b is formed inside the furnace shell 3 with a heat insulating board or the like. Subsequently, a mold for the lower molten metal storage container 4b (excluding the portion corresponding to the upper molten metal storage container 4a of the pressurizing portion 20a) is disposed inside the second heat insulating layer 5b, and the kneaded refractory is poured into the space formed by the second heat insulating layer 5b and the mold. After curing, the mold is removed to form the lower molten metal container 4b. In this state, the lower molten metal storage container 4b is dried and burned at a predetermined temperature rising curve and cooled to room temperature.

[0035] As shown in Fig. 8, after applying mortar S to the upper end surface of the lower molten metal storage container 4b, a pressure partition member 7 incorporating an upper molten metal storage container 4a that has been pre-formed using a mold, dried, and fired is placed, and the upper molten metal storage container 4a is fitted into the lower molten metal storage container 4b. Note that the incorporation of the upper molten metal storage container 4a into the pressure partition member 7 is performed by tightening a nut 8d onto a bolt 8c protruding from a holding plate 8a while one side of the holding plate 8a of the holding member 8 is supported by the surface of the shelf portion 6c of the upper molten metal storage container 4a and the other side is supported by the upper end surface of the support plate 8b.

[0036] As shown in Fig. 9, an amorphous refractory material for forming the inner side of the heat insulation layer 5b is poured into the space (A) on the outside of the furnace of the pressure partition member 7 and the space (Ba) excluding the upper part of the space formed between the inside of the furnace of the pressure partition member 7 and the outside of the furnace of the upper molten metal storage container 4a. After the amorphous refractory material has cured, the inner side of the second ceiling plate 7f is welded and fixed to the first ceiling plate 7d, and the outer side of the second ceiling plate 7f is welded and fixed to the outer ceiling plate 3b.

[0037] Next, as shown in Fig. 10, after placing a heat insulating material such as a heat insulating board in the space (Bb) formed by the surface of the amorphous refractory material poured into the space (Ba), the inner surface of the inner ceiling plate 3c, and a virtual vertical plane from the inner end surface of the inner ceiling plate 3c, the inner ceiling plate 3c is welded and fixed to the outer ceiling plate 3b.

[0038] Note that the spaces (Ba) and (Bb) may be composed of an amorphous refractory material. In this case, an amorphous refractory material is poured into the space (A), and after the amorphous refractory material has cured, the inner side of the second ceiling plate 7f is welded and fixed to the first ceiling plate 7d and the outer side of the second ceiling plate 7f is welded and fixed to the outer ceiling plate 3b. Then, a mold is placed on the upper end surface of the upper molten metal storage container 4a, and an amorphous refractory material is poured into the space formed by the mold, the inner side of the pressure partition member 7, and the outer side of the upper molten metal storage container 4a.

[0039] Next, the operation of the molten metal holding furnace 1 of the first embodiment will be described.

[0040] In FIG. 3, in order to supply the molten metal in the pressurizing portion 20a of the molten metal pressurizing chamber 20 (inside the molten metal storage container 4) to the mold 26, when pressurized gas is introduced from the pressurizing port 21b into the pressurizing portion 20a of the molten metal pressurizing chamber 20 (inside the molten metal storage container 4), as shown in FIG. 4, a part of the pressurized gas flows into the furnace inner wall 2. That is, the pressurized gas flows into the upper molten metal storage container 4a and the first heat insulating layer 5a from the gap at the contact portion between the canopy 21 and the upper molten metal storage container 4a and the non-dipped portion of the inner surface of the upper molten metal storage container 4a above the molten metal surface. On the other hand, since the inner surface of the lower molten metal storage container 4b is immersed in the molten metal, the pressurized gas does not flow into the lower molten metal storage container 4b. Further, the lower end surface of the upper molten metal storage container 4a and the upper end surface of the lower molten metal storage container 4b are engaged with each other with the downward convex portion 6a and the upward convex portion 6b interposing the insertion plate 7 of the pressure partition member 7, and the molten metal flowing into the joint portion 6 has a sealing effect on the pressurized gas. Therefore, the inflow of the pressurized gas from the upper molten metal storage container 4a to the lower molten metal storage container 4b is suppressed. Furthermore, since the second heat insulating layer 5b is isolated from the first heat insulating layer 5a by the pressure partition member 7, the pressurized gas does not flow in.

[0041] The pressure change of the gas contained in the furnace inner wall 2 causes a delay due to the ventilation resistance of the furnace inner wall 2 compared to the molten metal pressure change, and a pressure difference occurs between the response pressure and the gas pressure in the furnace inner wall 2. As a result, when the inside of the pressurizing portion 20a is opened to the atmosphere and depressurized, the gas pressure in the furnace inner wall 2 becomes higher than the molten metal pressure, and the pressurized gas existing in the first heat insulating layer 5a and the upper molten metal storage container 4a is released from the surface of the upper molten metal storage container 4a and bubbles are generated.

[0042] The joint portion 6 between the upper molten metal storage container 4a and the lower molten metal storage container 4b is in the molten metal immersion portion, and since there is no pressurized gas in the lower molten metal storage container 4b, the foaming phenomenon from the inner surface of the lower molten metal storage container 4b is prevented.

[0043] Thus, when introducing pressurized gas into the pressurizing section 20a (inside the molten metal storage container 4) of the molten metal pressurizing chamber 20, the pressurized gas only flows into the upper molten metal storage container 4a and the first heat insulation layer 5a, and does not flow into the lower molten metal storage container 4b and the second heat insulation layer 5b. Therefore, the usage amount of the pressurized gas can be significantly reduced. On the other hand, when the inside of the pressurizing section 20a of the molten metal pressurizing chamber 20 is opened to the atmosphere, as the discharge amount of the pressurized gas decreases, the generation of foreign substances such as oxides can be suppressed, the cleanliness of the molten metal can be maintained for a long time, the detection failure of the constant molten metal surface caused by the deposition of oxides on the molten metal surface can be prevented, and further, casting defects such as the mixing of foreign substances into the cast product due to the foaming phenomenon and the occurrence of casting cavities can be prevented.

Explanation of Reference Numerals

[0044] 1…Molten metal holding furnace for two-chamber low-pressure casting 2…Furnace inner wall 3…Furnace shell 3a…Top plate 3b…Outer top plate 3c…Inner top plate 4…Molten metal storage container 4a…Upper molten metal storage container 4b…Lower molten metal storage container 5…Heat insulation layer 5a…First heat insulation layer 5b…Second heat insulation layer 6…Joint part 6a…Downward convex part 6b…Upward convex part 6c…Shelf part 7…Pressure partition member 7a…Side surface part 7b…Bottom surface part 7c…Insertion part 7d…First ceiling plate 7e…Opening part 7f…Second ceiling plate 8…Holding member 8a…Holding plate 8b…Supporting plate 8c…Bolt 8d…Nut 10…Molten metal holding chamber 20…Molten metal pressurizing chamber 20a…Pressurizing section 20b…Molten metal outlet section 26…Mold 26a... cavity 30... molten metal flow path

Claims

1. A molten metal holding furnace for two-chamber low-pressure casting, in which a molten metal holding chamber and a molten metal pressurizing chamber are communicatively connected via an opening / closing molten metal flow path provided on the hearth of the molten metal holding chamber. The molten metal pressurizing chamber includes a pressurizing section and a tapping section that communicate at the bottom. The furnace inner walls of the molten metal holding chamber and the molten metal pressurizing chamber are composed of a molten metal storage container made of refractory castable and a heat insulation layer located on the back side of the molten metal storage container. Pressurized gas is introduced into the space of the pressurizing section to supply molten metal maintained at a predetermined temperature through the tapping section to the cavity of a mold. The pressurizing section of the molten metal storage container is partitioned into an upper molten metal storage container and a lower molten metal storage container via a joint, and the inner joint end of the joint in the furnace is located below the lower molten metal surface. The pressurizing section of the heat insulation layer is partitioned into a first heat insulation layer in the pressurized region and a second heat insulation layer in the non-pressurized region via a pressure partition member, one end of which is located in the joint and the other end of which is connected and fixed to the furnace shell of the pressurizing section. The molten metal holding furnace for two-chamber low-pressure casting is characterized by this.

2. The molten metal holding furnace for two-chamber low-pressure casting according to Claim 1, characterized in that the pressure partition member is a steel plate.

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