Method of forming semi-solid metal

Abstract

To provide a method of forming a semi-solid metal allowing for improving the quality of a product obtained by applying the semi-solid forming process (thixocasting process).SOLUTION: A method of forming a semi-solid metal includes: forming a billet B for semi-solid forming by obtaining a semi-solid metal having a granulated primary crystal and cooling / solidifying it after an elapse of predetermined time and thereafter receiving the billet B for semi-solid forming in a billet re-heating container 7; and charging the semi-solid metal obtained by re-heating the billet with a heater H arranged on the outer side, into a metal mold. A billet-forming stainless container 1 forms a circular frustum-shaped billet B having an end face B1 greater in diameter and an end face B2 smaller in diameter, and the billet re-heating container 7 consists of a ceramic container having a bottom 7a with the upper part opened, and receives and re-heats the billet B in a state that the end face B1 greater in diameter is closer to an opening 7b and the end face B2 smaller in diameter is closer to the bottom 7a.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a method for forming a semi-molten metal, in which a semi-molten metal having granulated primary crystals is obtained by simply filling a molten aluminum alloy, and then the billet for semi-molten metal forming is formed by cooling and solidifying it after a predetermined time, and the semi-molten metal obtained by reheating it is poured into a forming die. [Background technology]

[0002] Semi-molten molding is a method in which a semi-molten material (e.g., aluminum alloy casting material) in which the solid and liquid phases coexist is filled into a mold, and then cooled and solidified to obtain a product. Since molding can be performed from the solid-liquid coexistence region, it has the effect of accelerating the cooling rate and improving the mechanical properties of the product, and has been attracting attention in recent years. However, since a faster cooling rate also leads to faster solidification during molding, it is necessary to fill the mold with the material in a short time.

[0003] Therefore, in order to fill a material into a die in a short time, a semi-molten material that has good fluidity (i.e., filling ability) into the die and can be filled into the die in a short time is suitable for semi-molten molding, and to obtain such characteristics, it is necessary to make a semi-molten material having a granulated solid phase (primary crystals). In order to obtain such a semi-molten material, there have been disclosed techniques that can obtain granulated primary crystals by simply filling molten aluminum alloy under specified conditions when crystal nuclei grow as they solidify (see, for example, Patent Documents 1 and 2).

[0004] Furthermore, when a desired product is formed by applying a semi-molten metal forming method (thixocasting method), the semi-molten metal having granulated primary crystals obtained as described above is cooled and solidified to form a billet (a billet for semi-molten metal forming), and then the billet is reheated to generate a semi-molten metal and then charged into a forming die. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-155262 A [Patent Document 2] JP 2007-181874 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the above Patent Documents 1 and 2, the semi-molten metal forming method (thixocasting method) is applied to form the desired product, and so there is no disclosure of a technique for reheating the billet. For example, when a billet is placed in a billet reheating container and heated, dripping portions may form from the billet. If the semi-molten metal including the dripping portions is poured into a forming die, there is a risk that the dripping portions will be mixed into the product, deteriorating its quality.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a method for forming semi-molten metal that can improve the quality of products obtained by applying the semi-molten metal forming method (thixocasting method). [Means for solving the problem]

[0008] The invention described in claim 1 is a billet forming stainless steel vessel that is made of a stainless steel cylindrical vessel into which molten aluminum alloy can be poured to form a billet, the vessel having an inner diameter of 5 inches or less and a temperature of 300°C or less before pouring, and the pouring temperature of the molten aluminum alloy is set to a temperature between a solidification start temperature of the molten aluminum alloy and 640°C or less. By simply filling the vessel with the molten aluminum alloy, a semi-molten metal having granulated primary crystals is obtained, and the billet for semi-molten forming is formed by cooling and solidifying it after a predetermined time. The billet for semi-molten forming is then placed in a billet reheating vessel and sealed on the outside. A method for molding semi-molten metal in which semi-molten metal obtained by reheating using a heating device is poured into a molding die, the stainless steel container for billet molding being open at both ends and having an inner circumferential surface that is tapered so that the diameter expands from one open end to the other open end, molding a billet for semi-molten molding in a truncated cone shape having a larger diameter end face and a smaller diameter end face, the billet reheating container being made of a ceramic container that is open at the top and has a bottom, and containing and reheating the billet for semi-molten molding with the larger diameter end face on the open side and the smaller diameter end face on the bottom side.

[0009] The invention described in claim 2 is the method for molding semi-molten metal described in claim 1, in which, when the semi-molten metal is poured into the molding die from the opening of the billet reheating container, the semi-molten metal on the opening side of the billet reheating container is poured into the profile portion of the molding die, and then the dripping portion that has accumulated at the bottom is poured and is included in the biscuit portion of the molded product.

[0010] The invention described in claim 3 is characterized in that, in the method for forming semi-molten metal described in claim 2, the other open end of the stainless steel container for billet forming is brought into close contact with the upper surface of a plate-shaped pallet, molten aluminum alloy is poured into the internal space from the one open end, and then cooled and solidified to form a billet for semi-molten forming with the end face with a larger diameter in close contact with the pallet.

[0011] The invention described in claim 4 is the method for forming semi-molten metal described in claim 1, wherein the stainless steel container for forming a billet has ring portions formed on its outer surface, at least at the one opening end, the other opening end, and an intermediate portion located between the one opening end and the other opening end, the ring portions having a wall thickness dimension larger than that of other portions.

[0012] The invention as set forth in claim 5 is the method for forming a semi-molten metal as set forth in any one of claims 1 to 4, characterized in that the billet reheating vessel is heated by a high-frequency coil. Effect of the Invention

[0013] According to the present invention, the stainless steel container for billet molding is open at both ends and configured with an inner circumferential surface that slopes so that the diameter expands from one open end to the other open end, and molds a billet for semi-molten molding in a truncated cone shape having a larger diameter end face and a smaller diameter end face, and the container for billet reheating is made of a ceramic container that is open at the top and has a bottom, and contains and reheats the billet for semi-molten molding with the larger diameter end face on the opening side and the smaller diameter end face on the bottom side, so that the quality of the product obtained by applying the semi-molten molding method (thixocasting method) can be improved. [Brief description of the drawings]

[0014] [Figure 1] 1A and 1B are a front view, a plan view, and a bottom view showing a stainless steel vessel for forming a billet applied to a method for forming a semi-molten metal according to an embodiment of the present invention; [Diagram 2] Cross-sectional view of line II-II in Figure 1 [Diagram 3] FIG. 13 is a perspective view showing the billet forming stainless steel container placed on a pallet. [Figure 4] FIG. 3 is a cross-sectional view showing the state in which the billet-forming stainless steel container is filled with molten aluminum alloy. [Diagram 5] FIG. 3 is a cross-sectional view showing a billet taken out of the billet forming stainless steel container. [Figure 6]FIG. 11 is a perspective view showing a billet taken out of the billet forming stainless steel container. [Figure 7] FIG. 13 is a perspective view showing a state in which a tool is engaged with a ring portion of the billet forming stainless steel container. [Figure 8] FIG. 13 is a perspective view showing a state in which a tool is engaged with each of a plurality of ring portions of the billet forming stainless steel container. [Figure 9] FIG. 1 is a perspective view showing a billet reheating vessel applied to a method for forming a semi-molten metal according to an embodiment of the present invention; [Figure 10] FIG. 2 is a vertical sectional view showing the billet reheating vessel. [Figure 11] FIG. 1 is a schematic diagram showing the state in which the semi-molten metal obtained in the billet reheating vessel is poured into a molding die. [Figure 12] FIG. 1 is a perspective view showing a stainless steel container for billet molding according to another embodiment of the present invention. [Figure 13] FIG. 11 is a perspective view showing a stainless steel container for billet molding according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The method for forming semi-molten metal according to this embodiment is a method in which semi-molten metal having granulated primary crystals is obtained simply by filling the molten aluminum alloy under prescribed conditions, and then billet B for semi-molten forming is formed by cooling and solidifying it after a prescribed time has elapsed. The semi-molten metal obtained by reheating billet B is then poured into a forming die, and this method is carried out using a stainless steel container 1 for billet forming and a container 7 for billet reheating.

[0016] The billet molding stainless steel container 1 used in this embodiment is a stainless steel cylindrical container having one opening end 1a that opens upward and the other opening end 1b that opens downward, as well as an inner circumferential surface 1d and an outer circumferential surface 1e. As shown in Figures 1 and 2, the inner circumferential surface 1d slopes so that it expands in diameter from the one opening end 1a toward the other opening end 1b, and on the outer circumferential surface 1e, ring portions (2-4) whose wall thickness dimension t is larger than other portions are formed at at least one opening end 1a, the other opening end 1b, and an intermediate portion 1c located between the one opening end 1a and the other opening end 1b.

[0017] However, the billet forming stainless steel container 1 is configured such that its inner peripheral surface 1d is gradually increased in diameter from one opening end 1a toward the other opening end 1b, with the inner diameter of one opening end 1a being D1 and the inner diameter of the other opening end 1b being D2. That is, the billet forming stainless steel container 1 is designed such that the inner diameter D1 of one opening end 1a is smaller than the inner diameter D2 of the other opening end 1b. Then, as shown in Figs. 3 and 4, by bringing the other opening end 1b into close contact with the upper surface of a plate-shaped pallet 5, an internal space into which molten aluminum alloy can be poured is formed, and a truncated cone-shaped billet B can be formed in the internal space.

[0018] The ring portions (2-4) are formed in a convex shape integrally protruding sideways from the outer circumferential surface 1e of the billet forming stainless steel container 1, and are formed, for example, by cutting the outer circumferential surface 1e. Specifically, the ring portion 2 is formed in the vicinity of one opening end 1a, while the ring portion 3 is formed in the vicinity of the other opening end 1b, and the ring portion 4 is formed in the intermediate portion 1c, which is the region between the ring portions 2 and 3.

[0019] In addition, the wall thickness t of the ring portions (2-4) is set to be larger than the wall thickness w of other portions (portions where the ring portions are not formed), improving deformation resistance. Therefore, even when molten aluminum alloy is poured into the internal space and the stainless steel container for billet forming 1 is repeatedly heated, the ring portions (2-4) have improved deformation resistance, making it possible to suppress deformation even over long-term use.

[0020] Here, the specified conditions in the manufacturing process of the aluminum alloy casting material applied to this embodiment are that the inner diameter of the stainless steel container 1 for billet molding (the inner diameter D1 of one opening end 1a and the inner diameter D2 of the other opening end 1b) is 5 inches or less, the temperature at which the molten aluminum alloy is poured into the stainless steel container 1 for billet molding is not less than the solidification start temperature of the molten aluminum alloy and not more than 640°C, and the temperature of the stainless steel container 1 for billet molding before pouring is not more than 300°C.

[0021] In other words, if the temperature of the molten aluminum alloy to be poured and the temperature and inner diameter of the stainless steel container 1 for billet formation are set under the above-mentioned conditions, then simply filling the stainless steel container 1 for billet formation with the molten aluminum alloy can form semi-molten metal having primary crystals granulated with equiaxed crystals, and by cooling and solidifying the semi-molten metal over a predetermined period of time, a billet B for semi-molten forming can be obtained.

[0022] According to the manufacturing method under the above-described specified conditions, the temperature of the molten aluminum alloy poured into the stainless steel container 1 for billet molding, the size (inner diameters D1, D2) and temperature of the stainless steel container 1 for billet molding are simply set to specified conditions, and the molten aluminum alloy is poured into the stainless steel container 1 for billet molding. This allows for the production of semi-molten metal having primary crystals granulated with equiaxed crystals, simply by pouring the molten aluminum alloy into the stainless steel container 1 for billet molding. Therefore, a granulated semi-molten metal for molding can be obtained easily and at low cost, without using large-scale manufacturing equipment.

[0023] In this manner, assuming the above-mentioned specified conditions, as shown in FIG. 4, the other open end 1b of the billet forming stainless steel container 1 is brought into close contact with the pallet 5, and molten aluminum alloy is poured into the internal space from one open end 1a to obtain semi-molten metal having granulated primary crystals. This is then left for a specified period of time to cool and solidify, thereby forming a billet B for semi-molten forming having a truncated cone shape conforming to the inner surface 1d of the billet forming stainless steel container 1.

[0024] Thereafter, as shown in Fig. 7, a tool 6 is engaged with the ring portion 2 and the tool 6 is moved upward to lift the billet forming stainless steel container 1, whereby the billet B is removed from the billet forming stainless steel container 1 and placed on the upper surface of the pallet 5, as shown in Fig. 5. The billet B for semi-molten forming placed on the pallet 5 consists of a truncated cone-shaped metal block having a large diameter end face B1 and a small diameter end face B2, as shown in Fig. 6, and is placed with the large diameter end face B1 in close contact with the pallet 5.

[0025] The tool 6 has two locking arms 6a that match the outer diameter of the stainless steel container 1 for billet molding, and can be lifted by inserting the locking arms 6a into the lower part of the ring portion 2 formed at one of the opening ends 1a. Note that in this embodiment, the locking arms 6a are formed to lock onto the ring portion 2 formed at only one of the opening ends 1a, but in addition to the ring portion 2 (or instead of the ring portion 2), a locking arm 6b that locks onto the ring portion 4 formed at the middle portion 1c may be provided as shown in FIG. 8.

[0026] When the billet B is removed by lifting the billet forming stainless steel container 1 in this manner, the billet B can be removed smoothly because the inner peripheral surface 1d is inclined so as to expand in diameter from one opening end 1a toward the other opening end 1b. In particular, the billet forming stainless steel container 1 according to this embodiment is prevented from deformation in the longitudinal direction by the ring portions (2-4), so that the inclination can be maintained for a long period of time, and the billet B can be removed reliably. It is preferable that a release agent be applied in advance to the inner peripheral surface 1d of the billet forming stainless steel container 1.

[0027] The billet B obtained as described above is reheated before the forming process to become a semi-molten metal (semi-molten material) again, in order to form a desired product by applying a semi-molten molding method (thixocasting method). During such reheating, a billet reheating vessel 7 is used, which is open at the top and has a bottom 7a that matches the outer diameter of the billet B, as shown in Figures 9 and 10. The billet reheating vessel 7 is made of a ceramic vessel, and can be heated by, for example, a high-frequency coil while storing the billet B inside.

[0028] That is, in the method for forming semi-molten metal according to this embodiment, when the inner diameter (D1, D2) of the stainless steel container 1 for billet forming is set to 5 inches or less, the temperature before pouring is set to 300°C or less, and the pouring temperature of the molten aluminum alloy is equal to or higher than the solidification start temperature of the molten aluminum alloy and equal to or lower than 640°C, semi-molten metal having granulated primary crystals is obtained simply by filling the stainless steel container 1 for billet forming with the molten aluminum alloy, and billet B for semi-molten forming is formed by cooling and solidifying it after a predetermined time, and then billet B for semi-molten forming is placed in billet reheating container 7 and reheated by placing heating device H on the outside, and the obtained semi-molten metal is poured into forming die K.

[0029] 9 and 10, the billet reheating vessel 7 is made of a ceramic vessel that is open at the top and has a bottom 7a, and contains a billet B for semi-molten forming with the end face B1 with a larger diameter facing the opening 7b and the end face B2 with a smaller diameter facing the bottom 7a. In order to reheat the billet B using the billet reheating vessel 7, as shown in Fig. 10, a heating device H (high-frequency coil or the like) is disposed on the outside of the billet B contained in the billet reheating vessel 7, and the billet B is heated and melted by the heat generated by the heating device H.

[0030] By reheating in this manner, the billet B melts to obtain semi-molten metal Y, and the first dripping portion accumulates at the bottom 7a. Therefore, when the billet reheating container 7 is tilted and the semi-molten metal Y is poured into the molding die K through the opening 7b, as shown in FIG. 11, the semi-molten metal Y on the upper side of the billet reheating container 7 is poured first, followed by the dripping portion that has accumulated at the bottom 7a.

[0031] For example, as shown in Figs. 11(a) to 11(c), a case will be described in which a forming die K (movable die and fixed die) in which a profile portion Ka (product shape portion) is formed is used. First, as shown in Fig. 11(a), a billet reheating container 7 is tilted and semi-molten metal Y is poured into a sleeve M of a forming machine N from an opening 7b. Then, as shown in Fig. 11(b), a plunger P is operated to fill the profile portion Ka of the forming die K with semi-molten metal Y and then cooled and solidified, thereby obtaining a formed product J. Thereafter, as shown in Fig. 11(c), the die K is separated to remove the formed product J. Such a formed product J is formed by connecting a product portion Ja formed by the profile portion Ka and a biscuit portion Jb, and by cutting off the biscuit portion Jb, a product portion Ja that becomes a product can be obtained.

[0032] In this way, the dripping part of the bottom 7a is not introduced into the profile part Ka (product shape part) of the molding die K, so that it is not included in the product part Ja of the molded product J but is included in the biscuit part Jb, and it is possible to prevent the dripping part from being mixed into the product part Ja (product), and to prevent the dripping part from being discarded and to make effective use of it. That is, in the billet reheating vessel 7, as shown in FIG. 10, the billet B is in a state of being reduced in diameter toward the bottom 7a, so that the dripping part due to reheating is likely to drip down to the bottom 7a and accumulate there. In addition, the billet reheating vessel 7 according to this embodiment is made of a ceramic vessel having the bottom 7a, so that it has high heat resistance and can be easily transported to the molding die K after reheating.

[0033] Furthermore, since the billet B for semi-molten forming is accommodated and heated with the larger diameter end face B1 facing the opening 7b, it is possible to suppress air entrapment due to depressions formed by shrinkage cavities in the smaller diameter end face B2 of the billet B for semi-molten forming. That is, when the semi-molten metal is cooled and solidified in the stainless steel container 1 for billet forming to produce the billet B, the smaller diameter end face B2 is exposed to the outside air as shown in Fig. 4, which makes it easy for shrinkage cavities to occur.

[0034] Therefore, if the billet B is placed with the smaller diameter end face B2 facing the opening 7b, heated, and then charged into the molding die K, there is a risk that air will be drawn into the profile portion Ka due to the depressions formed by the shrinkage cavities. In contrast, according to this embodiment, the smaller diameter end face B2 of the billet B is positioned on the bottom portion 7a side, so that even if shrinkage cavities are formed in the smaller diameter end face B2, it is possible to suppress the entrainment of air due to the shrinkage cavities.

[0035] According to this embodiment, the stainless steel container 1 for billet molding is open at both ends and configured with an inner surface that slopes so that the diameter expands from one open end to the other open end, and molds a billet B for semi-molten molding in a truncated cone shape having a large diameter end face and a small diameter end face, while the billet reheating container 7 is made of a ceramic container that is open at the top and has a bottom 7a, and stores and reheats the billet B for semi-molten molding with the large diameter end face B1 on the opening 7b side and the small diameter end face B2 on the bottom 7a side, so that it is possible to prevent dripping parts from being mixed into the product and to improve the quality of products obtained by applying the semi-molten molding method (thixocasting method).

[0036] In particular, according to this embodiment, when the semi-molten metal is poured into the forming die K from the opening 7b of the billet reheating container 7, the semi-molten metal Y on the opening 7b (upper) side of the billet reheating container 7 is poured into the profile portion Ka of the forming die K, and then the dripping portion that has accumulated at the bottom 7a is poured and contained in the biscuit portion of the molded product, so that it is possible to reliably prevent the dripping portion from being mixed into the product and to make effective use of the dripping portion.

[0037] In addition, the other open end 1b of the billet molding stainless steel container 1 is placed in close contact with the upper surface of the plate-shaped pallet 5, and molten aluminum alloy is poured into the internal space from one open end 1a. This is then cooled and solidified to form a billet B for semi-molten molding with the larger diameter end face B1 in close contact with the pallet 5. Therefore, when reheating, the billet B can be easily placed in the billet reheating container 7.

[0038] Furthermore, the stainless steel container 1 for billet molding has ring portions (2-4) formed on its outer surface at least one opening end 1a, the other opening end 1b, and an intermediate portion 1c located between the one opening end 1a and the other opening end 1b, each of which has a wall thickness greater than that of other portions. Therefore, while satisfying the conditions for obtaining granulated primary crystals simply by filling the container with molten aluminum alloy, deformation due to heat can be suppressed even when the container is used repeatedly, allowing the billet B to be removed smoothly.

[0039] While the present embodiment has been described above, the present invention is not limited thereto, and in addition to the above embodiment in which one ring portion 4 is formed in the intermediate portion 1c, a plurality of ring portions 4 may be formed in the intermediate portion 1c, for example, two ring portions 4a, 4b may be formed as shown in Fig. 12. In this manner, by forming a plurality of ring portions 4 in the intermediate portion 1c, the heat resistance of the intermediate portion 1c can be improved, and deformation of the intermediate portion 1c due to heat can be reliably suppressed, thereby enabling the billet B to be removed reliably.

[0040] 13, the mold may be configured so as to be divided in the longitudinal direction and, when assembled, so as to form a cylindrical shape that can be filled with the molten aluminum alloy, and which can be disassembled when removing the billet B. In this way, if the mold is configured so as to be divided in the longitudinal direction and can be disassembled when removing the billet B, the billet B can be removed smoothly and reliably.

[0041] Furthermore, the billet reheating vessel 7 may be made of other materials as long as it is a vessel that can accommodate the billet B with the larger diameter end face B1 facing the opening 7b and the smaller diameter end face B2 facing the bottom 7a and can be reheated by a heating device. Furthermore, the heating device used for reheating may be of another type that can heat efficiently by using a high-frequency coil. [Industrial Applicability]

[0042] The present invention can also be applied to devices with different external shapes or devices with added functions, etc., so long as they have the same gist as the present invention. [Explanation of symbols]

[0043] 1 Stainless steel container for billet molding 1a One open end 1b The other open end 1c middle part 1d Inner surface 1e Outer surface 2~4 Ring section 5 Palette 6 Tools 7 Billet reheating vessel 7a bottom 7b opening B Billet for semi-molten molding B1 Large diameter end face B2 Small diameter end face K Molding Tool Ka Profile Department J Molded products Ja Product Department Jb Biscuit Club H heating device

Claims

1. A billet forming stainless steel vessel is made of a stainless steel cylindrical vessel into which a molten aluminum alloy can be poured to form a billet, the vessel having an inner diameter of 5 inches or less and a temperature of 300°C or less before pouring, the pouring temperature of the molten aluminum alloy is set to a temperature between the solidification start temperature of the molten aluminum alloy and 640°C or less, and a billet for semi-molten forming is formed by simply filling the vessel with the molten aluminum alloy, and the billet is then formed by cooling and solidifying the billet over a predetermined period of time. A method for forming a semi-molten metal, comprising: placing the billet for semi-molten forming in a billet reheating container; reheating the billet with a heating device disposed outside the billet; and pouring the resulting semi-molten metal into a forming die, a billet reheating container made of ceramic material having an open top and a bottom, and containing and reheating the billet for semi-molten metal forming with the larger diameter end face on the open side and the smaller diameter end face on the bottom side, and a billet for semi-molten metal forming is formed in the shape of a truncated cone, the billet reheating container being configured so that both ends are open and the larger diameter end face is on the open side and the smaller diameter end face is on the bottom side.

2. 2. The method for molding semi-molten metal according to claim 1, wherein, when the semi-molten metal is poured into the molding die from the opening of the billet reheating vessel, the semi-molten metal on the opening side of the billet reheating vessel is poured into the profile portion of the molding die, and then the dripping portion accumulated at the bottom is poured and contained in the biscuit portion of the molded product.

3. 3. The method for forming semi-molten metal according to claim 2, further comprising the steps of: bringing the other open end of the billet forming stainless steel container into close contact with an upper surface of a plate-shaped pallet; pouring molten aluminum alloy into the internal space from the one open end; and then cooling and solidifying the molten aluminum alloy to form the billet for semi-molten forming with the end face having a larger diameter in close contact with the pallet.

4. 2. The method for forming a semi-molten metal according to claim 1, wherein the stainless steel container for forming a billet has ring portions formed on its outer circumferential surface at least at the one opening end, the other opening end, and an intermediate portion located between the one opening end and the other opening end, the ring portions each having a wall thickness larger than that of other portions.

5. 5. The method for forming semi-molten metal according to claim 1, wherein the billet reheating vessel is heated by a high-frequency coil.

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