WO2008123644A1

WO2008123644A1 - Forging apparatus and forging method for rheocasting

Info

Publication number: WO2008123644A1
Application number: PCT/KR2007/005020
Authority: WO
Inventors: Tae-Soo Ha
Original assignee: Tae-Soo Ha
Priority date: 2007-04-06
Filing date: 2007-10-12
Publication date: 2008-10-16
Also published as: KR100861414B1

Abstract

Disclosed is a forging apparatus and forging method for rheocasting. The forging apparatus includes a molten metal guiding device installed to the main body and having a horizontally rotatable injection tube to guide molten metal to a riser tube, a molten metal transfer device installed behind the main body to transfer molten metal in a heat-keeping furnace to the molten metal guiding device, and a product transfer device installed at the main body to seat the discharged product thereon and transfer the seated product into a water vessel for cooling the product. The horizontally rotatable injection tube is changeable in position if necessary to maximize the utilization of a space therearound. The forging apparatus includes a ladle, which is horizontally and vertically transferred while being maintained in a stable state by the molten metal transfer device, to achieve stable transfer of even a heavy weight of the molten metal.

Description

FORGING APPARATUS AND FORGING METHOD FOR

RHEOCASTING

Technical Field

[1] The present invention relates to a forging apparatus and a forging method for rheocasting, and more particularly, to a forging apparatus and a forging method for rheocasting, wherein: a predetermined fixed amount of molten metal, which was accurately measured by a meter, is supplied into a riser tube, thereby always maintaining a constant size and physical properties of forged products; an injection tube can be rotated and returned after completion of a molten metal injecting operation to minimize the occupation of an available space by the injection tube, thereby maximizing the utilization of a space around a molten metal guiding device; and a ladle can be horizontally and vertically transferred in a state of being mounted stably by a molten metal transfer device, thereby assuring the stable transfer of even a heavy weight of molten metal received in the ladle. Background Art

[2] Casting is an operation to make a cast, and is performed in the order of designing a cast, preparing a casting plan, preparing a mold, melting and injecting a material, and finishing a product.

[3] A non-ferrous casting method includes a gravity die casting and a low-pressure die casting. The gravity die casting and the low-pressure die casting have advantages of providing products with various shapes, sizes, and thicknesses. However, they have a need for a high-temperature mold, high-temperature molten metal, and an excessively long solidification time. Therefore, the casting methods may cause cracks in a product due to air bubbles mixed in a product and a reduction in volume caused upon solidification.

[4] As described above, the gravity die casting and the low-pressure die casting accompany deteriorations in the density and mechanical properties of a finished product, and have a difficulty to satisfy requirements of various industries pursuing high-quality products. In particular, in the manufacture of vehicle components having a relatively large size and complex shape, the gravity die casting and the low-pressure die casting have a difficulty to comply with requirements of the manufacturing industry of vehicle components.

[5] Despite the above described problems, currently, many domestic and foreign vehicle component production enterprises produce various kinds of non-ferrous metal components such as an aluminum wheel by use of the gravity die casting and the low- pressure die casting. Therefore, due to the nature of these casting methods, there exist several problems, for example, an increase in the occurrence of a defective product, and deteriorations in mechanical properties of products such as a density, strength, elongation, etc. For this reason, the low-pressure die casting has been conventionally applied only to the manufacture of a small aluminum wheel (having a maximum size of 18 inches). Further, since the above described casting methods have to maintain a temperature of a mold within a range of about 38O⁰C to 400⁰C due to the nature thereof, a delay in the forging cycle of a product is inevitable, and in conclusion, the above described casting methods are unsuitable for mass production.

[6] To solve the above described problems, a cast forging method has been proposed.

The cast forging method is to solidify molten metal while applying a high pressure to the molten metal. This method has an advantage of enabling the mass production of products having superior mechanical properties and delicate structure.

[7] An example of a forging apparatus using non-ferrous metals is disclosed in Korean

Patent Registration No. 10-0254941 (entitled "Rheocasting Apparatus"). The rheocasting apparatus has the function of continuously producing high-quality products by rheocasting of non-ferrous metals.

[8] However, the conventional rheocasting apparatus has the following several problems.

[9] Firstly, although it is important to rapidly cool a lower mold and a side mold after completing a forging operation in order to perform a subsequent process, in the conventional rheocasting apparatus, the lower mold and the side mold rapidly heated by high-temperature molten metal cannot be cooled rapidly, resulting in a delay in the forging cycle of a product.

[10] Secondly, since an upper mold is directly introduced into the lower mold to press molten metal in the lower mold, the molten metal flows over an upper end of the lower mold, and a great amount of air may be mixed into the molten metal. The air mixed in the molten metal deteriorates the strength of a forged product, and consequently, increases the occurrence of a defective product.

[11] Thirdly, the conventional rheocasitng apparatus has no function for discharging the air mixed in and around the molten metal during the forging of molten metal using the upper and lower mold. Accordingly, the forged product inevitably has an uneven surface and suffers from a deterioration in strength.

[12] Fourthly, the periphery of an upper end of the upper mold has the slowest heat transfer and the fastest cooling. Therefore, when the molten metal in the lower mold is pressed by the upper mold, the molten metal is not wholly cooled at a uniform rate, but begins to be locally cooled starting from around the periphery of the upper end of the upper mold having the slowest heat transfer. Accordingly, an upper peripheral region of the pressed molten metal is first cooled, and exhibits a deterioration in physical properties and increased precipitation phenomenon.

[13] Fifthly, since a conventional molten metal injecting operation has been performed as an operator manually injects dangerous molten metal, which was melted in a blast furnace, into the lower mold by use of molten metal transfer tools such as a ladle, there always exists the risk of an accident. Further, the manual injection of molten metal makes it difficult to inject an accurate amount of molten metal everytime, and consequently, the manufacture of uniform, high-quality products is impossible. In fact, it is impossible to manually transfer and inject a great amount of molten metal, and the conventional apparatus has a limit in the production of large products. Disclosure of Invention Technical Problem

[14] Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a forging apparatus for rheocasting, which can assure rapid and sure cooling of a lower mold and a side mold, and a forging method using the same.

[15] It is another object of the present invention to provide a forging apparatus for rheocasting, which can achieve a thinner thickness in the center of a forged product than that in the periphery of the product, and a forging method using the same.

[16] It is a further object of the present invention to provide a forging apparatus for rheocasting, which can prevent molten metal from flowing over the periphery of an upper end of a lower mold while being guided to the upper end of the lower mold, and a forging method using the same.

[17] It is a still further object of the present invention to provide a forging apparatus for rheocasting, which can allow air in molten metal to be easily discharged to the outside during a forging operation, and a forging method using the same.

[18] It is a still further object of the present invention to provide a forging apparatus for rheocasting, which can allow a side mold to be stably supported by a side holder with an increased coupling force therebetween, and a forging method using the same.

[19] It is a still further object of the present invention to provide a forging apparatus for rheocasting, which can maintain a uniform temperature throughout the upper mold prior to performing a forging operation, and a forging method using the same.

[20] It is a still further object of the present invention to provide a forging apparatus for rheocasting, which can achieve sure discharge of a product from an upper mold, and a forging method using the same.

[21] It is a still further object of the present invention to provide a forging apparatus for rheocasting, which can supply a fixed amount of molten metal in a heat-keeping furnace into a riser tube while maintaining the molten metal at a constant temperature, and a forging method using the same.

[22] It is a still further object of the present invention to provide a forging apparatus for rheocasting, which can change the position of an injection tube as occasion demands, and a forging method using the same.

[23] It is yet another object of the present invention to provide a forging apparatus for rheocasting, which can assure safe transfer and supply of even a heavy weight of molten metal. Technical Solution

[24] In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a forging apparatus for rheocasting comprising: a main body having a main cylinder; a lower mold unit installed in a lower region of the main body and including a bed, a lower base fixed on the bed, and a lower mold installed on the lower base in a vertically movable manner to form a lower portion of a product; a side mold unit including a side mold installed around the lower mold unit to form the periphery of the product, a side holder installed around the side mold to support the side mold, and a link mechanism connected to the side mold and the side holder so as to allow the side mold to be expanded outward or returned upon an upward or downward movement of the lower mold; a mold cooling device installed around the lower mold unit and the side mold unit, to cool the peripheries of the lower mold unit and the side mold unit after the product is discharged therefrom; an upper mold unit installed in the main cylinder of the main body, to form an upper portion of the product while being moved up and down by the main cylinder; an upper mold heating device installed around an upper mold of the upper mold unit, to heat the periphery of an upper end of the upper mold so as to maintain a uniform temperature throughout the upper mold; a discharge device connected to the upper mold unit and used to push the product downward when the product is lifted together with the upper mold so as to separate the product from the upper mold unit; a heat-keeping furnace installed at one side of the main body, to store molten metal therein and to keep the molten metal at a constant temperature; a molten metal guiding device installed to the main body and having an injection tube to guide the molten metal injected thereinto to a riser tube, the injection tube being installed in a horizontally rotatable manner; a molten metal transfer device installed behind the main body, to transfer the molten metal in the heat-keeping furnace to the molten metal guiding device; and a product transfer device installed at the other side of the main body, to seat the discharged product thereon and to transfer the seated product into a water vessel for cooling the product.

[25] The lower mold unit may comprise: the bed; the lower base fixed on the bed; a lower fixing plate installed on the bed inside the lower base; the lower mold fixed on the lower fixing plate; and a lower lock-out cylinder connected to the lower mold, to move up and down the lower fixing plate and the lower mold.

[26] The center of an inner surface of the lower mold may protrude upward as compared to the periphery of the inner surface.

[27] The periphery of an upper end of the lower mold may have molten metal discharge grooves.

[28] The side holder and the side mold may have a plurality of inclined surfaces formed at corresponding contact surfaces thereof.

[29] The link mechanism may comprise: a stationary link having one end fixed to an upper end of the side holder and the other end provided with an operating pin; and a pivotable link having one end coupled to an upper end of the side mold by a hinge pin and the other end formed with a slot such that the operating pin is inserted into and guided along the slot.

[30] The link mechanism may comprise: a stationary link having one end fixed to the upper end of the side holder; and an operating cylinder having one end coupled to the other end of the stationary link by a first hinge pin and the other end provided with a rod, an end of the rod being coupled to the upper end of the side mold by a second hinge pin.

[31] A temperature adjustment plate may be wound on the periphery of the side holder.

[32] The mold cooling device may comprise: a first cooling pipe connected to a cooler and installed in the side holder to cool the side mold; a second cooling pipe connected to the cooler and installed in the lower base to cool the lower mold unit and the side mold unit; and a third cooling pipe connected to the cooler and installed in the bed to cool the lower base.

[33] The upper mold unit may comprise: an upper base installed to the main cylinder; an upper fixing plate fixed to the upper base; a supporting shaft having an upper end fixed to the upper fixing plate; an upper mold plate fixed to a lower end of the supporting shaft; and an upper mold installed to the upper mold plate.

[34] The inner surface of the lower mold and a bottom surface of the upper mold may have vent holes to discharge air in the molten metal to the outside during a forging operation of the molten metal injected in the lower mold.

[35] The upper mold may comprise: an upper outer mold connected to the upper mold plate and used to press the upper periphery of the product while being moved down together with the upper mold plate; and an upper center mold installed in the center of the upper outer mold to be moved up and down separately from the upper outer mold and used to press the center of the product, so as to discharge the forged product.

[36] The discharge device may comprise: an upper lock-out cylinder installed on the center of the upper mold; a discharge plate connected to a rod of the upper lock-out cylinder so as to be moved up and down along the rod; a pressure rod fixed to the center of a lower surface of the discharge plate; a discharge shaft installed to a lower end of the pressure rod to push down the center of the product so as to discharge the product; a discharger installed to the periphery of the upper mold to push down the periphery of the product so as to discharge the product; and a discharge pin provided between the discharge plate and the discharger, to push down the discharger upon a downward movement of the discharge plate.

[37] The upper mold heating device may comprise: a ring-shaped burner head installed around the upper end of the upper mold and having a plurality of fuel igniters; and a fuel supply hose connected to the burner head to supply fuel into the burner head.

[38] The molten metal guiding device may comprise: a supporting shaft installed on the rear center of the main body; a rotating shaft vertically installed on an upper end of the supporting shaft; a drive motor connected to the rotating shaft, to rotate the rotating shaft; an angle adjustment bracket fixed to an upper end of the rotating shaft to be rotated in a horizontal direction together with the rotating shaft; and the injection tube installed to the angle adjustment bracket to guide the molten metal into the riser tube.

[39] The angle adjustment bracket may comprise: a hinge hole formed in one side of the bracket, to which one side of the injection tube is coupled by a hinge pin; and an arcuate angle adjustment hole formed in the other side of the bracket such that the injection tube is pivotally rotated about the hinge pin or is fixed to the angle adjustment bracket by means of an angle adjustment bolt after being pivotally rotated.

[40] The heat-keeping furnace may comprise: a supporting frame installed at a side of the main body; a body installed on the supporting frame; a supporting link installed between the supporting frame and the body to support the body while guiding upward and downward movements of the body; a lifting cylinder installed between the supporting frame and the body to move the body up and down; a blast furnace installed in a side of the body to store the molten metal therein; a molten metal supply source provided on the body to guide and supply the molten metal into the blast furnace; an injection tube installed at the other side of the body to inject the molten metal in the blast furnace into the riser tube; and a meter installed to the body at a position near the injection tube, to measure the weight of the molten metal to be supplied into the injection tube, so as to discharge only a preset weight of the molten metal.

[41] The molten metal transfer device may comprise: a molten metal transfer guide rail installed between the heat-keeping furnace and the injection tube; a molten metal transfer carrier installed on the molten metal transfer guide rail to be transferred along the guide rail; a carrier transfer motor installed to the molten metal transfer carrier, to move the carrier along the molten metal transfer guide rail; a vertical guide fixed to a side of the molten metal transfer carrier, to be reciprocally moved together with the molten metal transfer carrier; a ladle bar installed to the vertical guide, to be moved up and down along the vertical guide; a ladle bar lifting cylinder installed on the molten metal transfer carrier and connected to the ladle bar, to move up and down the ladle bar; a ladle installed at an end of the ladle bar in a pivotally rotatable manner, to store the molten metal in the heat-keeping furnace and to inject the stored molten metal into the injection tube; and a ladle pivoting motor provided at an upper end of the ladle bar such that it is connected to the ladle to pivotally rotate the ladle.

[42] The product transfer device may comprise: a product transfer rail provided at a side of the main body; a product transfer carrier installed on the product transfer rail such that the carrier is transferred along the rail to receive and transfer the discharged product; a product holder transfer rail installed to connect the product transfer carrier and the water vessel with each other; and a product holder installed on the product holder transfer rail to be moved along the transfer rail and used to grip the product on the product transfer carrier so as to transfer the product into the water vessel.

[43] The product transfer carrier may comprise release agent injectors to inject a release agent to the lower mold, the side mold, and the upper mold.

[44] In accordance with another aspect of the present invention, the above and other objects can be accomplished by the provision of a forging method for rheocasting using a forging apparatus comprising: a main body having a main cylinder; a lower mold installed in a lower region of the main body; a side mold installed around the lower mold to form the periphery of a product; an upper mold installed in the main cylinder of the main body; a discharge device connected to the upper mold to separate the product from the upper mold; an upper mold heating device installed around the upper mold to heat the periphery of an upper end of the upper mold; and a product transfer device installed at the other side of the main body, to seat the discharged product thereon and to transfer the seated product, the forging method comprising: rotating and setting a riser tube and an injection tube such that the riser tube is transferred to a position above the lower mold and one end of the injection tube is located above the riser tube, in order to inject molten metal in a heat-keeping furnace into the lower mold; heating the periphery of the upper end of the upper mold, which has the slowest heat transfer and the fastest cooling, by use of a burner, to maintain a uniform temperature throughout the upper mold; putting the molten metal in the heat- keeping furnace into a ladle and injecting the molten metal received in the ladle into the injection tube, to inject the molten metal into the lower mold through the injection tube and the riser tube; pressing and forging the molten metal in the lower mold as the upper mold is lowered by operation of the main cylinder; lifting the lower mold and the side mold connected to a lower lock-out cylinder by operation of the lower lock-out cylinder after the molten metal in the lower mold is pressed and forged, and expanding the side mold outward to separate the side mold from the periphery of the product; lifting the upper mold by the main cylinder after the lower mold and the side mold are lifted, to separate the product from the lower mold; discharging the product from the upper mold by the discharge device after the product is separated from the lower mold; locating a product transfer carrier below the upper mold to load the product discharged from the upper mold thereon so as to transfer the loaded product to a water vessel, and gripping the product by a product holder to immerse the transferred product in the water vessel for cooling the product; and injecting a release agent into the upper mold, the lower mold, and the side mold after completing the transfer of the product. [45] The pressing and forging of the molten metal may comprise: pressing and forging the periphery of the molten metal in the lower mold by pushing an upper outer mold constituting the upper mold downward; and pressing and forging the center of the molten metal in the lower mold by pushing an upper center mold constituting the upper mold downward.

Advantageous Effects

[46] Now, several effects of the present invention will be described.

[47] Firstly, a side holder, a lower base, and a bed are installed, respectively, with a first cooling pipe, a second cooling pipe, and a third cooling pipe, to achieve rapid and sure cooling of the lower mold and the side mold after completion of a forging operation.

[48] Secondly, since a center portion of the lower mold is convexly raised as compared to a peripheral portion thereof, the center of a forged product has a thinner thickness than that of the periphery of the product. As a result, the center of the forged product has a reduced solidification time, resulting in a reduction in the forging cycle of the product and improved physical properties of the product.

[49] Thirdly, by virtue of molten metal discharge grooves formed in the periphery of the lower mold, when the upper mold is introduced into the lower mold to press the molten metal, the molten metal in the lower mold is smoothly guided to the periphery of an upper end of the lower mold along the molten metal discharge grooves. Accordingly, there is no risk that the molten metal flows over while being guided to the periphery of the upper end of the lower mold, and it is possible to prevent a great amount of air from being mixed into the molten metal.

[50] Fourthly, by virtue of vent holes formed in an inner surface of the lower mold and a bottom surface of the upper mold, air mixed in and around the molten metal is easily discharged to the outside through the vent holes while the molten metal is forged by the lower mold and the upper mold. This prevents the occurrence of a defective product. [51] Fifthly, an outer peripheral surface of the side mold and an inner peripheral surface of the side holder are formed with first and second inclined surfaces, respectively. By allowing contact surfaces of the side mold and the side holder to be supported by the two inclined surfaces, the side mold can be stably supported by the side holder with an increased coupling force therebetween.

[52] Sixthly, there is provided a burner, which includes a ring-shaped burner head having a fuel igniter and a fuel supply hose connected to the burner head so as to supply fuel into the burner head. The burner is used to heat the periphery of an upper end of the upper mold, which shows the slowest heat transfer and the fastest cooling. Thereby, the upper mold can be heated to maintain a uniform temperature throughout the upper mold before or after a forging operation. This has the effects of improving physical properties of the periphery of the upper mold and substantially eliminating the risk of precipitation.

[53] Seventhly, in operation of a product discharge device, if an upper lock-out cylinder is operated and a discharge plate is lowered, a pressure rod used to press the center of the product, a discharge shaft, a discharge pin to press the periphery of the product, and a discharger are lowered simultaneously. Thereby, as the center and the periphery of the product can be pressed simultaneously by the discharge device, the product can be surely discharged from the upper mold.

[54] Eighthly, the molten metal in a heat-keeping furnace can be sufficiently heated by a blast furnace to keep a constant temperature, and a fixed amount of the molten metal accurately measured by a meter can be supplied into a riser tube. Accordingly, it is possible to always maintain a constant size and physical properties of forged products.

[55] Ninthly, the present invention provides a molten metal guiding device having an injection tube installed to rotate in a horizontal direction. While the molten metal is injected into the riser tube, the injection tube is rotated such that one end thereof faces the riser tube. Then, after completing the injection of the molten metal, the injection tube is rotated such that both ends of the injection tube face opposite sides of a rear surface of a main body, so as to occupy only a minimum space. By allowing the injection tube to rotate and return to its original orientation after completing the injection of the molten metal, the utilization of a space around the molten metal guiding device can be maximized.

[56] Tenthly, a molten metal transfer guide rail is installed between the heat-keeping furnace and the molten metal guiding device, and a molten metal transfer carrier is installed on the molten metal transfer guide rail to be moved along the guide rail. Also, the molten metal transfer carrier is installed with a ladle such that the ladle is movable up and down along a vertical guide provided at a side of the carrier. With this configuration, the ladle can be horizontally and vertically moved while being kept in a stable state by a molten metal transfer device, and even a heavy weight of the molten metal received in the ladle can be stably transferred. Brief Description of the Drawings

[57] The above and other objects, features, and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: [58] FIGS. 1 to 3 are a front view, a side view, and a plan view, respectively, schematically illustrating a forging apparatus for rheocasting according to the present invention; [59] FIG. 4 is a sectional view schematically illustrating the injection of molten metal into a lower mold; [60] FIG. 5 is a sectional view schematically illustrating the forging of molten metal in the lower mold under the pressing of upper and lower molds; [61] FIG. 6 is a sectional view schematically illustrating the simultaneously raised state of the upper and lower molds; [62] FIG. 7 is a sectional view schematically illustrating the separated state of the upper and lower molds; [63] FIG. 8 is a sectional view schematically illustrating a product discharged from the upper mold;

[64] FIGS. 9 and 10 are a sectional view and a plan view, respectively, schematically illustrating the lower mold; [65] FIGS. 11 and 12 are a sectional view and a bottom view, respectively, schematically illustrating the upper mold; [66] FIGS. 13 and 14 are partial sectional views schematically illustrating another embodiment of a link structure included in a side mold unit; [67] FIG. 15 is a perspective view schematically illustrating a temperature adjustment plate to be wound on the periphery of a side holder; [68] FIG. 16 is a sectional view schematically illustrating another embodiment of a product discharge device; [69] FIGS. 17 and 18 are a schematic perspective view of an upper mold heating device, and a sectional view illustrating the use of the upper mold heating device, respectively; [70] FIG. 19 is a side view schematically illustrating a molten metal guiding device;

[71] FIG. 20 is a side view schematically illustrating another embodiment of a heat- keeping furnace; [72] FIGS. 21 to 23 are a front view, a side view, and a plan view, respectively, schematically illustrating a molten metal transfer device; [73] FIG. 24 is partial side view schematically illustrating another embodiment of a product transfer carrier; and

[74] FIGS. 25 and 26 are flow charts illustrating the sequence of a forging method for rheocasting. Best Mode for Carrying Out the Invention

[75] The detailed characteristics and advantages of the present invention will be more clearly understood by reading the following description with reference to the accompanying drawings.

[76] FIGS. 1 to 3 are a front view, a side view, and a plan view, respectively, schematically illustrating a forging apparatus for rheocasting according to the present invention. FIGS. 4 to 8 are sectional views schematically illustrating the sequence of a method for forging molten metal injected into a lower mold.

[77] The forging apparatus for rheocasting according to the present invention comprises a main body 10, a lower mold unit 20, a side mold unit 30, a mold cooling device 50, an upper mold unit 60, an upper mold heating device 80, a molten metal guiding device 120, a molten metal transfer device 130, and a product transfer device 140.

[78] The main body 10, as shown in FIG. 1, includes a main cylinder 11 installed in the center of an upper region thereof. The upper mold unit 60 that will be described hereinafter is installed to the main cylinder 11 in a vertically movable manner. Provided below the upper mold unit 60 is the lower mold unit 20 that will be described hereinafter.

[79] The lower mold unit 20, as shown in FIGS. 4 to 8. is installed in the center of a lower region of the main body 10. The lower mold unit 20 includes a bed 21, a lower base 22 mounted on the bed 21, a lower fixing plate 23 mounted on the bed 21 so as to be located inside the lower base 22, a lower mold 24 fixed on the lower fixing plate 23, and a lower lock-out cylinder 25 connected to the lower mold 24 so as to move up and down the lower mold 24.

[80] Molten metal is injected into the lower mold 24. The center of an inner surface of the lower mold 24, as shown in FIGS. 4 to 8 and FIG. 9, is raised convexely than the periphery of the inner surface, such that the inner surface of the lower mold 24 has a convex portion 24a. With the use of the lower mold 24, the center of a forged product has a thinner thickness than that of the periphery of the product. Accordingly, the center of the forged product has a reduced solidification time, and consequently, a forging cycle of the product can be reduced and also, physical properties of the forged product can be improved.

[81] The lower mold 24, as shown in FIGS. 9 and 10, is formed, along the periphery of an upper end thereof, with molten metal discharge grooves 24b. In the illustrated embodiment, four molten metal discharge grooves 24b are radially arranged, about the center of the lower mold 24, in the periphery of the lower mold 24. With this configuration, when an upper mold 55 is introduced into the lower mold 24 to press the molten metal in the lower mold 24, the molten metal can be smoothly guided to the periphery of an upper end of the lower mold 24 along the molten metal discharge grooves 24b. Thereby, there is no risk that the molten metal flows over in the course of being guided to the periphery of the upper end of the lower mold 24. This has the effect of preventing a great amount of air from being mixed into the molten metal. Although the four molten metal discharge grooves 24b are illustrated, it will be appreciated that below or above four molten metal discharge grooves may be provided.

[82] The inner surface of the lower mold 24, as shown in FIGS. 9 and 10, is formed with vent holes 24c to discharge air mixed in the molten metal to the outside while the molten metal injected into the lower mold 24 is forged. With the vent holes 24c formed in the inner surface of the lower mold 24, the air mixed in and around the molten metal can be easily discharged to the outside through the vent holes 24c while the molten metal is forged by the lower mold 24 and the upper mold 55.

[83] The side mold unit 30, as shown in FIGS. 4 to 8, includes a side mold 31 installed around the lower mold unit 20 to form the periphery of a product M, a side holder 32 to support the periphery of the side mold 31, and a link mechanism 33 connected to the side mold 31 and the side holder 32 so as to support the side mold 31 when the side mold 31 is expanded outward by an upward movement of the lower mold 24.

[84] The side mold 31 to form the periphery of the product M has a lower end fixed to the lower fixing plate 23 such that the side mold 31 is moved up and down together with the lower fixing plate 23. An upper end of the side mold 31 is connected to the link mechanism 33. The side mold 31 has a plurality of inclined surfaces, more particularly, first and second inclined surfaces 31a and 31b defined at an outer circumference thereof.

[85] The side holder 32 to support the periphery of the side mold 31 has a lower end fixed to the lower base 22 and an upper end connected to the link mechanism 33. The side holder 32 has a plurality of surfaces, more particularly, first and second inclined surfaces 32a and 32b defined at an inner circumference thereof.

[86] As the first and second inclined surfaces 31a and 31b at the outer circumference of the side mold 31 come into contact with the first and second inclined surfaces 32a and 32b at the inner circumference of the side holder 32 such that the side mold 31 and the side holder 32 are supported by each other, the side mold 31 can be stably supported by the side holder 32 with an increased coupling force therebetween.

[87] The link mechanism 33 includes a stationary link 34 and a pivotable link 35. The stationary link 34 has one end fixed to the upper end of the side holder 32, and an operating pin 37 is provided at the other end of the stationary link 34. The pivotable link 35 has one end coupled to the upper end of the side mold 31 by a hinge pin 36. The other end of the pivotable link 35 is formed with a longitudinal slot 35a such that the operating pin 37 is inserted into and guided along the slot 35a.

[88] FIGS. 13 and 14 are partial sectional views schematically illustrating another embodiment of the link mechanism. The link mechanism 40 of the present embodiment is characterized in that the pivotable link 35 is replaced by an operating cylinder 43. The link mechanism 40 includes a stationary link 41 having one end fixed to the upper end of the side holder 32, and the operating cylinder 43 having one end coupled to the other end of the stationary link 41 by a first hinge pin 42 and the other end provided with a rod 44, an end of the rod 44 being coupled to the upper end of the side mold 31 by a second hinge pin 45.

[89] If the side mold 31 is moved up and down, the operating cylinder 43 of the link mechanism 40 is pivotally rotated about the first hinge pin 42, and the rod 44 is reciprocally moved forward and rearward, so as to guide the outward expansion and return of the side mold 31.

[90] FIG. 15 is a perspective view schematically illustrating a temperature adjustment plate 46. The temperature adjustment plate 46 is wound around the side holder 32. It is necessary to appropriately heat the side holder 32 before a forging operation, and to cool the side holder 32 after the forging operation. The temperature adjustment plate 46 may take the form of a heater plate connected to a heating system for heating the side holder 32, or may take the form of a cooling plate connected to a cooling system for cooling the side holder 32.

[91] The mold cooling device 50, as shown in FIGS. 4 to 8, includes a first cooling pipe

51, a second cooling pipe 52, and a third cooling pipe 53. The first cooling pipe 51 is connected to a cooler (not shown) and is installed in the side holder 32 to cool the side mold 31. The first cooling pipes 51 is arranged along both inner and outer peripheries of the side holder 32. The second cooling pipe 52 is connected to the cooler and is installed in the lower base 22 to cool the lower mold unit 20 and the side mold unit 30. The third cooling pipe 53 is connected to the cooler and is installed in the bed 21 to cool the lower base 22 via circulation of a refrigerant.

[92] Since the mold cooling device 50 is arranged throughout the side holder 32, lower base 22, and bed 21, the lower mold 24 and the side mold 31 can be rapidly and surely cooled after completion of a forging operation.

[93] The upper mold unit 60, as shown in FIGS. 4 to 8, is installed in the main cylinder 11 of the main body 10, to form an upper portion of the product M as it is moved up and down by the main cylinder 11.

[94] The upper mold unit 60 includes an upper base 61 installed to the main cylinder 11, an upper fixing plate 62 fixed to the upper base 61, a supporting shaft 63 having an upper end fixed to the upper fixing plate 62, an upper mold plate 64 fixed to a lower end of the supporting shaft 63, and an upper mold 65 installed to the upper mold plate 64.

[95] The upper mold 65 is divided into an upper outer mold 66 and an upper center mold

67.

[96] The upper outer mold 66 is used to press the upper periphery of the product M, and has an upper end fixed to the upper mold plate 64. The upper outer mold 66 has a plurality of vent holes 66a radially formed in a bottom surface thereof. With this configuration, while the molten metal is forged by the upper outer mold 66, the air mixed in and around the molten metal can be easily discharged to the outside through the vent holes 66a.

[97] The upper center mold 67 is located in the center of the upper outer mold 66 and is moved up and down along with the upper outer mold 66. Pressure shafts 68 are connected to the upper periphery of the upper center mold 67. Each pressure shaft 68 is also connected with a pressure cylinder (not shown). The pressure shaft 68 is pushed downward by operation of the pressure cylinder, to press the center of the molten metal.

[98] The upper center mold 67 is connected, at the upper center thereof, with a discharge shaft 69 constituting a product discharge device. The discharge shaft 69 is connected with a discharge cylinder (not shown). The upper center mold 67 is moved downward by operation of the discharge cylinder, to discharge the product M attached to the periphery of the upper outer mold 66 downward.

[99] FIG. 16 is a sectional view schematically illustrating another embodiment of the product discharge device. The product discharge device 70 of the present embodiment is characterized in that it presses the center and the periphery of the product M simultaneously, to achieve sure discharge of the product M from an upper mold 77.

[100] The product discharge device 70 includes an upper lock-out cylinder 71 installed on the center of the upper mold 77. A discharge plate 72 is connected to a rod of the upper lock-out cylinder 71 so as to be moved up and down along the rod. A pressure rod 73 is fixed to the center of a lower surface of the discharge plate 72. In turn, a discharge shaft 74 is installed to a lower end of the pressure rod 73 to push down the center of the product M so as to discharge the product M. A discharger 75 is installed to the periphery of the upper mold 77 to push down the periphery of the product M so as to discharge the product M. A discharge pin 76 is provided between the discharge plate 72 and the discharger 75, to push down the discharger 75 upon a downward movement of the discharge plate 72.

[101] In operation of the product discharge device 70 having the above described configuration, if the upper lock-out cylinder 71 is operated, the discharge plate 72 is lowered. As the discharge plate 72 is lowered, the pressure rod 73 and the discharge shaft 74 to press the center of the product M and the discharge pin 76 and the discharger 75 to press the periphery of the product M are lowered simultaneously. Accordingly, the product discharge device 70 is operated to press the center and the periphery of the product M simultaneously, thereby achieving sure discharge of the product M from the upper mold 77.

[102] The upper mold heating device 80, as shown in FIGS. 17 and 18, is installed around the upper mold 65, and more particularly, around the upper outer mold 66, to heat the periphery of an upper end of the upper outer mold 66 in order to maintain a uniform temperature throughout the upper outer mold 66.

[103] The upper mold heating device 80 takes the form of a burner. The burner includes a ring-shaped burner head 81 to surround the upper end of the upper outer mold 66 and having a plurality of fuel igniters 82, and a fuel supply hose 83 connected to the burner head 81 to supply fuel into the burner head 81.

[104] The upper mold heating device 80 is used to heat the periphery of the upper end of the upper outer mold 66 just prior to or during a forging operation. Since the periphery of the upper end of the upper outer mold 66 is a portion having the slowest heat transfer and the fastest cooling, this portion has to be appropriately heated, to maintain a uniform temperature throughout the upper outer mold 66 during a forging operation. This has the effects of improving physical properties in the periphery of the upper outer mold 66 and preventing precipitation in the periphery of the upper end of the upper outer mold 66 and the periphery of an upper end of the product M.

[105] A heat-keeping furnace 100 is installed at a side of the main body 10. The heat- keeping furnace 100 is configured to store molten metal therein and keep the molten metal at a constant temperature. The molten metal stored in the heat-keeping furnace 100 is injected into the lower mold 24 by the molten metal transfer device 130 and the molten metal guiding device 120, which will be described hereinafter.

[106] FIG. 20 is a side view schematically illustrating another embodiment of the heat- keeping furnace. The heat-keeping furnace 110 of the present embodiment includes a supporting frame 111 installed at a side of the main body 10. A body 112 is installed on the supporting frame 111, and a supporting link 113 is installed between the supporting frame 111 and the body 112 to support the body 112 while guiding upward and downward movements of the body 112. Also, a lifting cylinder 114 is installed between the supporting frame 111 and the body 112 to move the body 112 up and down. A blast furnace 115 to store molten metal therein is provided in a side of the body 112, and a molten metal supply source 116 is provided on the body 112 to supply molten metal into the blast furnace 115. An injection tube 117 is installed at the other side of the body 112 to inject the molten metal in the blast furnace 115 into a riser tube 91. The body 112 is provided, at a position toward the injection tube 117, with a meter 118 to measure the weight of the molten metal to be supplied into the injection tube 117, so as to discharge a preset weight of the molten metal.

[107] The heat-keeping furnace 110 having the above described configuration keeps the molten metal, which was supplied from the molten metal supply source 116 and sufficiently heated by the blast furnace 115, at a constant temperature.

[108] When the molten metal in the heat-keeping furnace 110 is supplied into the riser tube

91, the molten metal first passes through the meter 118. Accordingly, after being measured by the meter 118, only a fixed amount of the molten metal is supplied into the riser tube 91. As a predetermined constant amount of molten metal is always injected by the meter 118 of the heat-keeping furnace 110, the forged products M have the same size and physical properties as each other.

[109] The molten metal guiding device 120, as shown in FIGS. 2 and 19, is installed to the main body 10 at a position behind the lower mold 24. The molten metal guiding device 120 includes an injection tube 127 to inject molten metal into the riser tube 91 when the riser tube 91 is located on the lower mold 24 by operation of a riser tube cylinder

92. The injection tube 127 is installed to rotate in a horizontal direction.

[110] The molten metal guiding device 120 includes a drive motor 121 installed at the rear center of the main body 10, a hollow supporting shaft 122 installed on the drive motor 121, a rotating shaft 123 vertically installed on an upper end of the supporting shaft 122 and connected to the drive motor 121 so as to be rotated upon operation of the drive motor 121, an angle adjustment bracket 124 fixed to an upper end of the rotating shaft 123 to be rotated in a horizontal direction together with the rotating shaft 123, and the injection tube 127 installed to the angle adjustment bracket 124 to guide molten metal into the riser tube 91.

[I l l] Here, the angle adjustment bracket 124 has a hinge hole 124a formed in one side thereof such that a side of the injection tube 127 is coupled to the angle adjustment bracket 124 by means of a hinge pin 125. The angle adjustment bracket 124 further has an arcuate angle adjustment hole 124b formed in the other side thereof such that the injection tube 127 is pivotally rotated about the hinge pin 125 or is fixed to the angle adjustment bracket 124 by means of an angle adjustment bolt 126 after being pivotally rotated.

[112] The injection tube 127 of the molten metal guiding device 120 is adjustable in a vertical angle by the angle adjustment bracket 124 and the hinge pin 125 and the angle adjustment bolt 126 coupled to the angle adjustment bracket 124. Also, the injection tube 127 is rotatable in a horizontal direction by the drive motor 121 and the rotating shaft 123.

[113] The injection tube 127 of the molten metal guiding device 120 is rotated such that one end of the injection tube 127 faces the riser tube 91 when molten metal is injected into the riser tube 91 and also, such that both ends of the injection tube 127 face opposite sides of a rear surface of the main body 10 after completing the injection of the molten metal, so as to minimize a space occupied by the molten metal guiding device 120. Accordingly, after the molten metal is completely injected, the injection tube 127 is again rotated and returned to maximize the utilization of a space in the vicinity of the molten metal guiding device 120.

[114] The molten metal transfer device 130, as shown in FIGS. 1 to 3 and FIG. 21, is installed behind the main body 10, to transfer the molten metal in the heat-keeping furnace 100 into the injection tube 127 of the molten metal guiding device 120.

[115] The molten metal transfer device 130 includes a molten metal transfer guide rail 131 to transfer a ladle 137, which will be described hereinafter, through the heat-keeping furnace 100 and the injection tube 127. A molten metal transfer carrier 132 is installed on the molten metal transfer guide rail 131 to be transferred along the guide rail 131. The molten metal transfer carrier 132 is provided with a carrier transfer motor 133 to transfer the carrier 132 along the molten metal transfer guide rail 131.

[116] A vertical guide 134 is fixed to a side of the molten metal transfer carrier 132 such that it is transferred horizontally along the molten metal transfer guide rail 131 together with the molten metal transfer carrier 132. The vertical guide 134 is provided with a ladle bar 135 such that the ladle bar 135 is moved up and down along the vertical guide 134, A ladle bar lifting cylinder 136 is installed on the molten metal transfer carrier 132, and a ladle bar 135 is connected to a rod of the ladle bar lifting cylinder 136. Accordingly, the ladle bar 135 is moved up and down along the vertical guide 134 by operation of the ladle bar lifting cylinder 136.

[117] The ladle 137 is installed at an end of the ladle bar 135, to inject the molten metal stored in the heat-keeping furnace 100 into the injection tube 127. The ladle 137 is coupled to an end of the ladle bar 135 by a hinge shaft 139. A ladle pivoting motor 138 is provided at an upper end of the ladle bar 135 such that it is connected to the ladle 137 to pivotally rotate the ladle 137 about the hinge shaft 139.

[118] In the above described molten metal transfer device 130, the molten metal transfer guide rail 131 is provided between the heat-keeping furnace 100 and the molten metal guiding device 120, and the molten metal transfer carrier 132 is installed on the molten metal transfer guide rail 131 to be transferred along the guide rail 131. The ladle 137 is installed to the molten metal transfer carrier 132 so as to be moved up and down along the vertical guide 134 provided at the side of the molten metal transfer carrier 132. Accordingly, since the ladle 137 can be transferred horizontally and vertically while being kept in a stable state by the molten metal transfer carrier 132, even a heavy weight of molten metal received in the ladle 137 can be transferred stably. [119] The product transfer device 140, as shown in FIG. 1, includes a product transfer rail 141 provided at a side of the main body 10. A product transfer carrier 142 is installed on the product transfer rail 141 such that the carrier 142 is transferred along the rail 141 to receive and transfer the discharged product M. A product holder transfer rail 143 is installed between the product transfer carrier 142 and a water vessel 145 to connect them with each other. A product holder 144 is installed to the product holder transfer rail 143 to grip the product on the product transfer carrier 142 so as to transfer the product into the water vessel 145.

[120] FIG. 24 is partial side view schematically illustrating another embodiment of the product transfer carrier. The product transfer carrier 150 of the present embodiment includes release agent injectors 151 to inject a release agent to the lower mold 24, side mold 31, and upper mold 65. If the product M is discharged from the upper mold 65, the release agent injectors 151 are operated to inject a release agent to the lower mold 24, side mold 31, and upper mold 65.

[121] The release agent injectors 151 may be installed at fixed positions of the product transfer carrier 150, or may be installed rotatably. Specifically, the respective release agent injectors 151 may be rotated individually, or all the release agent injectors 151 may be horizontally rotated together about the center of the product transfer carrier 150. With the rotation of the release agent injectors 151, it is possible to prevent a release agent from being injected only onto a partial region of the lower mold 24, side mold 31, and upper mold 65.

[122] FIGS. 25 and 26 are flow charts illustrating the sequence of a forging method for rheocasting. Now, a forging method according to the present invention will be described with reference to the drawings.

[123] First, the forging method comprises a step SlO for setting the riser tube 91 and the injection tube 127. In the setting step SlO, to inject the molten metal in the heat- keeping furnace 100 into the lower mold 24, the riser tube 91 is transferred to a position above the lower mold 24, and one end of the injection tube 127 is rotated to be located on the riser tube 91.

[124] Subsequent to the setting step SlO of the riser tube 91 and the injection tube 127, the forging method comprises a upper mold heating step S20 to heat the periphery of the upper end of the upper mold 65, which has the slowest heat transfer and the fastest cooling, by use of the burner. With the heating step S20, while the upper mold 65 presses the molten metal in the lower mold 24, the periphery of the upper mold 65, which is relatively far away from the interior of the lower mold 24, can maintain the same or similar temperature as the lower region of the upper mold 65. Thereby, the overall upper mold can keep a constant temperature during the forging of molten metal. This has the effects of improving physical properties in the periphery of the upper mold 65 and reducing the precipitation phenomenon in the periphery of the upper end of the upper mold 65 or the periphery of the upper end of the product M.

[125] After completing the upper mold heating step S20, a molten metal injection step S30 is performed using the molten metal guiding device 120 and the molten metal transfer device 130.

[126] If the riser tube 91 is transferred to a position above the lower mold 24 by operation of the riser tube cylinder 92 as shown in FIG. 4, the molten metal guiding device 120 is operated.

[127] If the drive motor 121 of the molten metal guiding device 120 is operated, the rotating shaft 123 is rotated to horizontally rotate the angle adjustment bracket 124 and the injection tube 127 installed to the rotating shaft 123. As the injection tube 127 is rotated such that one end of the injection tube 127 is located on the riser tube 91, the drive motor 121 is stopped.

[128] The molten metal transfer device 130 is operated as soon as the drive motor 121 of the molten metal guiding device 120 is stopped. In operation of the molten metal transfer device 130, as the rod of the ladle bar lifting cylinder 136 of the molten metal transfer device 130 is first moved forward, the ladle bar 135 is moved downward along the vertical guide 134, and the ladle 137 is introduced into the heat-keeping furnace 100. After an appropriate amount of molten metal in the heat-keeping furnace 100 is put into the ladle 137, the rod of the ladle bar lifting cylinder 136 is moved rearward, to discharge the ladle 137 from the top of the heat-keeping furnace 100.

[129] Once the appropriate amount of molten metal is put into the ladle 137, the carrier transfer motor 133 of the molten metal transfer device 130 is operated to horizontally transfer the molten metal transfer carrier 132 along the molten metal transfer guide rail 131. Thereby, the ladle 137 above the heat-keeping furnace 100 is transferred along the molten metal transfer guide rail 131 to a position above the injection tube 127 of the molten metal guiding device 120.

[130] The carrier transfer motor 133 is stopped and the ladle pivoting motor 138 is operated as soon as the ladle 137 is located on the top of the injection tube 127. With operation of the ladle pivoting motor 138, the ladle 137 is pivotally rotated about the hinge shaft 139 to inject the molten metal in the ladle 137 into the injection tube 127. The molten metal injected into the injection tube 127 flows along the injection tube 127, to thereby be introduced into the lower mold 24 through the riser tube 91.

[131] After the molten metal is injected into the lower mold 24 as shown in FIG. 4 by the molten metal injection step S30, the upper mold 65 is lowered as shown in FIG. 5, to prepare a press forging step S40 for pressing the molten metal in the lower mold 24.

[132] The press forging step S40 is divided, as shown in FIG. 26, into a periphery press step SlOO and a center press step Sl 10. In the periphery press step SlOO, the upper mold 65, more particularly, the upper outer mold 66 is pushed downward to press the periphery of the molten metal in the lower mold 24. In the center press step Sl 10 to be performed after completing the periphery press step SlOO, the upper mold 65, more particularly, the upper center mold 67 is pushed downward to press the center of the molten metal in the lower mold 24.

[133] After the molten metal in the lower mold 24 is pressed and forged by the press forging step S40, a mold lifting step S50 follows. In the mold lifting step S50, as shown in FIG. 6, the lower lock-out cylinder 25 is operated to lift the lower mold 24 and the side mold 31 connected to the lower lock-out cylinder 25, thereby expanding the side mold 31 outward for separating the side mold 31 from the periphery of the product M.

[134] In a state wherein the molds are lifted by the mold lifting step S50, as shown in FIG. 7, an upper mold lifting step S60 is performed. In this step, the upper mold 65 is further lifted by the main cylinder 11, to separate the product M from the lower mold 24.

[135] If the product M is separated from the lower mold 24 by the upper mold lifting step S60, as shown in FIG. 8, a product discharge step S70 to discharge the product M from the upper mold 65 is performed.

[136] In the product discharge step S70, the discharge shaft 69 is lowered to lower the upper center mold 67, thereby discharging the product M attached to the periphery of the upper outer mold 66 downward.

[137] Now, the product discharge step S70 using the discharge device 70 as shown in FIG. 16 will be described. First, if the discharge plate 72 is lowered by operation of the upper lock-out cylinder 71, the pressure rod 73 and the discharge shaft 74 to press the center of the product M, and the discharge pin 76 and the discharger 75 to press the periphery of the product M are lowered simultaneously. Accordingly, as the discharge device 70 presses the center and the periphery of the product M simultaneously, the product M can be surely discharged from the upper mold 65.

[138] Subsequent to the product discharge step S70, a product transfer step S80 is performed to transfer the discharged product M. In this step, the product transfer carrier 142 is located below the upper mold 65 such that the product M discharged from the upper mold 65 is loaded thereon. The loaded product M is transferred to the water vessel 145, and the product M is gripped by the product holder 144 to thereby be immersed and cooled in the water vessel 145.

[139] After completing the product transfer step S 80, a release agent coating step S90 to inject a release agent into the upper mold 65, lower mold 24, and side mold 31 is performed.

[140] The above described forging apparatus for rheocasting according to the present invention has the following several advantages.

[141] Firstly, since the side holder 32, the lower base 22, and the bed 21 are installed with the first cooling pipe 51, the second cooling pipe 52, and the third cooling pipe 53, the lower mold 24 and the side mold 31 can be rapidly and surely cooled after completing a forging operation.

[142] Secondly, since the center of the lower mold 24 is raised convexly as compared to the periphery of the lower mold 24, the center of the forged product M has a thinner thickness than that of the periphery of the product M. As a result, the center of the forged product M has a reduced solidification time, resulting in a reduction in the forging cycle of the product M and improved physical properties of the product M.

[143] Thirdly, by virtue of the molten metal discharge grooves 24b formed on the periphery of the lower mold 24, when the upper mold 65 is introduced into the lower mold 24 to press the molten metal, the molten metal in the lower mold 24 is smoothly guided to the periphery of the upper end of the lower mold 24 along the molten metal discharge grooves 24b. Accordingly, there is no risk that the molten metal flows over in the course of being guided to the periphery of the upper end of the lower mold 24, and it is possible to prevent a great amount of air from being mixed into the molten metal.

[144] Fourthly, by virtue of the vent holes 24c and 66a formed in the inner surface of the lower mold 24 and the bottom surface of the upper mold 65, air mixed in and around the molten metal can be easily discharged to the outside through the vent holes 24c and 66a while the molten metal is forged by the lower mold 24 and the upper mold 65. This prevents the occurrence of a defective product.

[145] Fifthly, the outer peripheral surface of the side mold 31 and the inner peripheral surface of the side holder 32 are formed with the first and second inclined surfaces 31a and 32a and 31b and 32b, respectively. By allowing contact surfaces of the side mold 31 and the side holder 32 to be supported by the two inclined surfaces, the side mold 31 can be stably supported by the side holder 32 with an increased coupling force therebetween.

[146] Sixthly, there is provided an upper mold heating device 80, which includes a ring- shaped burner head 81 having a fuel igniter 82 and a fuel supply hose 83 connected to the burner head 81 so as to supply fuel into the burner head 81. The upper mold heating device 80 is used to heat the periphery of the upper end of the upper mold 65, which shows the slowest heat transfer and the fastest cooling. Thereby, the upper mold 65 can be heated to maintain a uniform temperature throughout the upper mold 65 before or after a forging operation. This has the effects of improving physical properties of the periphery of the upper mold 65 and substantially eliminating the risk of precipitation. [147] Seventhly, in operation of a product discharge device 70, if an upper lock-out cylinder 71 is operated and a discharge plate 72 is lowered, a pressure rod 73 used to press the center of the product M, a discharge shaft 74, a discharge pin 76 to press the periphery of the product M, and a discharger 75 are lowered simultaneously. Thereby, as the center and the periphery of the product M can be pressed simultaneously by the discharge device 70, the product M can be surely discharged from the upper mold 77.

[148] Eighthly, the molten metal in the heat-keeping furnace 110 can be sufficiently heated by the blast furnace 115 to keep a constant temperature, and a fixed amount of the molten metal accurately measured by the meter 118 can be supplied into the riser tube 91. Accordingly, it is possible to always maintain a constant size and physical properties of forged products.

[149] Ninthly, the present invention provides the molten metal guiding device 120 having the injection tube 127 installed to rotate in a horizontal direction. While the molten metal is injected into the riser tube 91, the injection tube 127 is rotated such that one end thereof faces the riser tube 91. Then, after completing the injection of the molten metal, the injection tube 127 is rotated such that both ends of the injection tube 127 face opposite sides of the rear surface of the main body 10, so as to occupy only a minimum space. By allowing the injection tube 127 to rotate and return to its original orientation after completing the injection of the molten metal, the utilization of a space around the molten metal guiding device 120 can be maximized.

[150] Tenthly, the molten metal transfer guide rail 131 is installed between the heat- keeping furnace 100 and the molten metal guiding device 120, and the molten metal transfer carrier 132 is installed on the molten metal transfer guide rail 131 to be moved along the guide rail 131. Also, the molten metal transfer carrier 132 is installed with the ladle 137 such that the ladle 137 is movable up and down along the vertical guide 134 provided at a side of the carrier 132. With this configuration, the ladle 137 can be horizontally and vertically moved while being kept in a stable state by the molten metal transfer device 130, and even a heavy weight of the molten metal received in the ladle 137 can be stably transferred. Industrial Applicability

[151] As apparent from the above description, according to a forging apparatus of the present invention, a lower mold and a side mold can be rapidly and surely cooled by a lower mold cooling device after completing a forging operation. This can reduce the solidification time of a forged product, resulting in a reduced forging cycle of the product. Further, the present invention can prevent molten metal from flowing over in the course of being guided to the periphery of an upper end of the lower mold, and consequently, can prevent a great amount of air from being mixed into the molten metal. According to the present invention, during a forging operation of the molten metal, air mixed in and around the molten metal can be easily discharged to the outside through vent holes, and a side mold can be stably supported by a side holder. Furthermore, with the use of an upper mold heating device, the overall upper mold can be kept at a uniform temperature before or after a forging operation. Upon discharge of a forged product, the center and the periphery of the product can be pressed simultaneously by a lower movement of a discharge plate constituting a discharge device, to achieve sure discharge of the product from an upper mold. In the present invention, a fixed amount of molten metal, which is measured by a meter, can be supplied into a riser tube, to always maintain the same size and physical properties of forged products. In addition, with the use of an injection tube which is installed to rotate horizontally, it is possible to change the position of the injection tube as occasion demands, and consequently, to maximize the utilization of a space around the injection tube. Finally, according to the present invention, a ladle can be horizontally and vertically transferred while being maintained in a stable state by a molten metal transfer device, thereby enabling even a heavy weight of molten metal therein to be stably transferred.

[152] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying drawings.

[153]

Claims

[1] A forging apparatus for rheocasting comprising: a main body having a main cylinder; a lower mold unit installed in a lower region of the main body and including a bed, a lower base fixed on the bed, and a lower mold installed on the lower base in a vertically movable manner to form a lower portion of a product; a side mold unit including a side mold installed around the lower mold unit to form the periphery of the product, a side holder installed around the side mold to support the side mold, and a link mechanism connected to the side mold and the side holder so as to allow the side mold to be expanded outward or returned upon an upward or downward movement of the lower mold; a mold cooling device installed around the lower mold unit and the side mold unit, to cool the peripheries of the lower mold unit and the side mold unit after the product is discharged therefrom; an upper mold unit installed in the main cylinder of the main body, to form an upper portion of the product while being moved up and down by the main cylinder; an upper mold heating device installed around an upper mold of the upper mold unit, to heat the periphery of an upper end of the upper mold so as to maintain a uniform temperature throughout the upper mold; a discharge device connected to the upper mold unit and used to push the product downward when the product is lifted together with the upper mold unit so as to separate the product from the upper mold unit; a heat-keeping furnace installed at one side of the main body, to store molten metal therein and to keep the molten metal at a constant temperature; a molten metal guiding device installed to the main body and having an injection tube to guide the molten metal injected thereinto to a riser tube, the injection tube being installed in a horizontally rotatable manner; a molten metal transfer device installed behind the main body, to transfer the molten metal in the heat-keeping furnace to the molten metal guiding device; and a product transfer device installed at the other side of the main body, to seat the discharged product thereon and to transfer the seated product into a water vessel for cooling the product.

[2] The forging apparatus according to claim 1, wherein the lower mold unit comprises: the bed; the lower base fixed on the bed; a lower fixing plate installed on the bed inside the lower base; the lower mold fixed on the lower fixing plate; and a lower lock-out cylinder connected to the lower mold, to move up and down the lower fixing plate and the lower mold.

[3] The forging apparatus according to claim 2, wherein the center of an inner surface of the lower mold protrudes upward as compared to the periphery of the inner surface.

[4] The forging apparatus according to claim 2 or 3, wherein the periphery of an upper end of the lower mold has molten metal discharge grooves.

[5] The forging apparatus according to claim 1, wherein the side holder and the side mold have a plurality of inclined surfaces formed at corresponding contact surfaces thereof.

[6] The forging apparatus according to claim 1, wherein the link mechanism comprises: a stationary link having one end fixed to an upper end of the side holder and the other end provided with an operating pin; and a pivotable link having one end coupled to an upper end of the side mold by a hinge pin and the other end formed with a slot such that the operating pin is inserted into and guided along the slot.

[7] The forging apparatus according to claim 1, wherein the link mechanism comprises: a stationary link having one end fixed to the upper end of the side holder; and an operating cylinder having one end coupled to the other end of the stationary link by a first hinge pin and the other end provided with a rod, an end of the rod being coupled to the upper end of the side mold by a second hinge pin.

[8] The forging apparatus according to claim 1 or 5, wherein a temperature adjustment plate is wound on the periphery of the side holder.

[9] The forging apparatus according to claim 1, wherein the mold cooling device comprises: a first cooling pipe connected to a cooler and installed in the side holder to cool the side mold; a second cooling pipe connected to the cooler and installed in the lower base to cool the lower mold unit and the side mold unit; and a third cooling pipe connected to the cooler and installed in the bed to cool the lower base.

[10] The forging apparatus according to claim 1 or 2, wherein the upper mold unit comprises: an upper base installed to the main cylinder; an upper fixing plate fixed to the upper base; a supporting shaft having an upper end fixed to the upper fixing plate; an upper mold plate fixed to a lower end of the supporting shaft; and an upper mold installed to the upper mold plate.

[11] The forging apparatus according to claim 10, wherein the inner surface of the lower mold and a bottom surface of the upper mold have vent holes to discharge air in the molten metal to the outside during a forging operation of the molten metal injected in the lower mold.

[12] The forging apparatus according to claim 10, wherein the upper mold comprises: an upper outer mold connected to the upper mold plate and used to press the upper periphery of the product while being moved down together with the upper mold plate; and an upper center mold installed in the center of the upper outer mold to be moved up and down separately from the upper outer mold and used to press the center of the product, so as to discharge the forged product.

[13] The forging apparatus according to claim 1, wherein the discharge device comprises: an upper lock-out cylinder installed on the center of the upper mold; a discharge plate connected to a rod of the upper lock-out cylinder so as to be moved up and down along the rod; a pressure rod fixed to the center of a lower surface of the discharge plate; a discharge shaft installed to a lower end of the pressure rod to push down the center of the product so as to discharge the product; a discharger installed to the periphery of the upper mold to push down the periphery of the product so as to discharge the product; and a discharge pin provided between the discharge plate and the discharger, to push down the discharger upon a downward movement of the discharge plate.

[14] The forging apparatus according to claim 1, wherein the upper mold heating device comprises: a ring-shaped burner head installed around the upper end of the upper mold and having a plurality of fuel igniters; and a fuel supply hose connected to the burner head to supply fuel into the burner head.

[15] The forging apparatus according to claim 1, wherein the heat-keeping furnace comprises: a supporting frame installed at a side of the main body; a body installed on the supporting frame; a supporting link installed between the supporting frame and the body to support the body while guiding upward and downward movements of the body; a lifting cylinder installed between the supporting frame and the body to move the body up and down; a blast furnace installed in a side of the body to store the molten metal therein; a molten metal supply source provided on the body to guide and supply the molten metal into the blast furnace; an injection tube installed at the other side of the body to inject the molten metal in the blast furnace into the riser tube; and a meter installed to the body at a position near the injection tube, to measure the weight of the molten metal to be supplied into the injection tube, so as to discharge only a preset weight of the molten metal.

[16] The forging apparatus according to claim 1, wherein the molten metal guiding device comprises: a supporting shaft installed on the rear center of the main body; a rotating shaft vertically installed on an upper end of the supporting shaft; a drive motor connected to the rotating shaft, to rotate the rotating shaft; an angle adjustment bracket fixed to an upper end of the rotating shaft to be rotated in a horizontal direction together with the rotating shaft; and the injection tube installed to the angle adjustment bracket to guide the molten metal into the riser tube.

[17] The forging apparatus according to claim 16, wherein the angle adjustment bracket comprises: a hinge hole formed in one side of the bracket, to which one side of the injection tube is coupled by a hinge pin; and an arcuate angle adjustment hole formed in the other side of the bracket such that the injection tube is pivotally rotated about the hinge pin or is fixed to the angle adjustment bracket by means of an angle adjustment bolt after being pivotally rotated.

[18] The forging apparatus according to claim 1, wherein the molten metal transfer device comprises: a molten metal transfer guide rail installed between the heat-keeping furnace and the injection tube; a molten metal transfer carrier installed on the molten metal transfer guide rail to be transferred along the guide rail; a carrier transfer motor installed to the molten metal transfer carrier, to move the carrier along the molten metal transfer guide rail; a vertical guide fixed to a side of the molten metal transfer carrier, to be reciprocally moved together with the molten metal transfer carrier; a ladle bar installed to the vertical guide, to be moved up and down along the vertical guide; a ladle bar lifting cylinder installed on the molten metal transfer carrier and connected to the ladle bar, to move up and down the ladle bar; a ladle installed at an end of the ladle bar in a pivotally rotatable manner, to store the molten metal in the heat-keeping furnace and to inject the stored molten metal into the injection tube; and a ladle pivoting motor provided at an upper end of the ladle bar such that it is connected to the ladle to pivotally rotate the ladle.

[19] The forging apparatus according to claim 1, wherein the product transfer device comprises: a product transfer rail provided at a side of the main body; a product transfer carrier installed on the product transfer rail such that the carrier is transferred along the rail to receive and transfer the discharged product; a product holder transfer rail installed to connect the product transfer carrier and the water vessel with each other; and a product holder installed on the product holder transfer rail to be moved along the transfer rail and used to grip the product on the product transfer carrier so as to transfer the product into the water vessel.

[20] The forging apparatus according to claim 19, wherein the product transfer carrier comprises release agent injectors to inject a release agent to the lower mold, the side mold, and the upper mold.

[21] A forging method for rheocasting using a forging apparatus comprising: a main body having a main cylinder; a lower mold installed in a lower region of the main body; a side mold installed around the lower mold to form the periphery of a product; an upper mold installed in the main cylinder of the main body; a discharge device connected to the upper mold to separate the product from the upper mold; an upper mold heating device installed around the upper mold to heat the periphery of an upper end of the upper mold; and a product transfer device installed at the other side of the main body, to seat the discharged product thereon and to transfer the seated product, the forging method comprising: rotating and setting a riser tube and an injection tube such that the riser tube is transferred to a position above the lower mold and one end of the injection tube is located above the riser tube, in order to inject molten metal in a heat-keeping furnace into the lower mold; heating the periphery of the upper end of the upper mold, which has the slowest heat transfer and the fastest cooling, by use of a burner, to maintain a uniform temperature throughout the upper mold; putting the molten metal in the heat-keeping furnace into a ladle and injecting the molten metal received in the ladle into the injection tube, to inject the molten metal into the lower mold through the injection tube and the riser tube; pressing and forging the molten metal in the lower mold as the upper mold is lowered by operation of the main cylinder; lifting the lower mold and the side mold connected to a lower lock-out cylinder by operation of the lower lock-out cylinder after the molten metal in the lower mold is pressed and forged, and expanding the side mold outward to separate the side mold from the periphery of the product; lifting the upper mold by the main cylinder after the lower mold and the side mold are lifted, to separate the product from the lower mold; discharging the product from the upper mold by the discharge device after the product is separated from the lower mold; locating a product transfer carrier below the upper mold to load the product discharged from the upper mold thereon so as to transfer the loaded product to a water vessel, and gripping the product by a product holder to immerse the transferred product in the water vessel for cooling the product; and injecting a release agent into the upper mold, the lower mold, and the side mold after completing the transfer of the product.

[22] The forging method according to claim 21, wherein the pressing and forging of the molten metal comprises: pressing and forging the periphery of the molten metal in the lower mold by pushing an upper outer mold constituting the upper mold downward; and pressing and forging the center of the molten metal in the lower mold by pushing an upper center mold constituting the upper mold downward.