JP3646662B2 - Mold for casting - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a die for light metal casting, for example, aluminum die casting, and more particularly to a multi-cavity casting die.
[0002]
[Prior art]
The temperature of the mold is an important factor for the casting produced therefrom, and affects many things such as the size of the casting, the quality of the casting surface, the soundness of the casting, the life of the mold, and the casting productivity. The mold takes away the heat energy brought in by the molten metal by cooling water, mold release agent, heat radiation to the air, and the balance determines the mold temperature. As production conditions, it is desirable that the entire mold, particularly the entire cavity, have a uniform temperature and no variation.
[0003]
Therefore, conventionally, methods for increasing the number of cooling pipes or reducing the distance between the mold surface and the cooling pipes have been performed to balance the cooling of the mold. However, the former has a problem that the cooling pipe cannot be arranged at a necessary part due to an increase in die processing cost, interference between the ejector pin and the cooling hole, and the latter is likely to cause water leakage due to a crack of the mold. There was a problem of becoming.
[0004]
In addition, with the recent demand for cost reduction of cast products, productivity improvement by multi-cavity is an indispensable issue along with shortening the cycle size of the casting process. It was difficult to make product quality from all cavities uniform. In particular, when using a multi-cavity and low-speed filling die casting method, the effect of the aluminum solidification rate in the cavity on the product quality is significant, so it is essential to reduce the quality variation between cavities. It was a problem.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and its purpose is to minimize the curing time, to reduce the occurrence rate of nest defects, shrinkage nests, etc. The object of the present invention is to provide a casting mold that makes it possible to obtain a sound casting by suppressing variation in quality.
[0008]
[Means for Solving the Problems]
The present invention provides a casting mold according to each of the claims as means for solving the above-mentioned problems. The casting mold according to claim 1, wherein a molten metal supply passage for supplying molten metal to these cavities is formed in a mold in which three or more cavities are formed, and the molten metal supply passage is common. A branch passage that branches off from the passage and communicates with each cavity portion, and the cross-sectional area of the branch passage having the shortest length among these branch passages is made smaller than the cross-sectional area of the other branch passages. Thereby, the influence of the heat of the high temperature part of a common channel | path can be reduced, and the shift | offset | difference of solidification timing can be made small.
[0009]
The casting mold according to claim 2 has a dam portion provided in the branch passage to reduce the cross-sectional area of the flow passage, whereby the temperature of the dam portion becomes high due to heat from the flowing molten metal. Therefore, the final solidified portion is not in the cavity portion but in the vicinity of the dam portion. Therefore, it is possible to prevent the occurrence of defects such as a cast hole in the cast product serving as the product portion.
In the casting mold according to claim 3 , the dam portion is formed in an arc shape or a taper shape, so that the molten metal can be introduced into the cavity portion without disturbing the flow of the molten metal. The tissue can be made uniform.
[0010]
In the casting mold of claim 4 , the speed of the molten metal flowing into the cavity portion is regulated to 0.05 to 0.3 m / s, and when the flowing speed of the molten metal is slow as described above, Since differences in the timing of solidification start and the solidification rate are likely to occur, the present invention is particularly effective in the mold structure of the casting mold of the present invention.
The casting mold according to claim 5 is formed by forming three or more cavities at the same height position, and thereby performing from the start of filling the molten metal into the cavity until the completion of filling. Is possible.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a casting mold according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view of a casting mold according to an embodiment of the present invention, FIG. 2 is a diagram illustrating a casting mold and a cooling water flow system, and FIG. It is the top view and sectional drawing of the casting mold of another embodiment which has one cavity part (product part). The casting mold 1 includes a fixed mold 2 and a movable mold 3. As shown in FIG. 2, a bushing 5 and a sleeve 6 are disposed in the casting mold 4, and a plunger 7 is provided so as to be fitted thereto. Yes.
[0012]
As shown in FIG. 3, the mold 1 includes a cavity portion 8 that is a product portion, a runner portion 9 corresponding to a branch passage of the molten metal supply passage to the cavity portion 8, and a hot water reservoir that is a common passage of the molten metal supply passage. The biscuit part 10 equivalent to is formed. Therefore, the molten metal pushed out by the movement of the plunger 7 is introduced from the biscuit portion 10 through the runner portion 9 into the cavity portion 8 where it solidifies to form a product.
[0013]
As shown in FIGS. 1 and 2, the main mold 3a in which the cavity 8 of the movable mold 3 is formed is equipped with a nest 11 having a cooling water passage 12 formed as a cooling means. In the present invention, three or more cavity portions 8 are formed in the mold 1, and three or more cooling means are provided corresponding to the cavity portions. As the nesting material, a material having a thermal conductivity different from that of the main mold material is used. For example, an SKD steel material of JIS G4404 is used as the main mold material, and Cu or the like is used as the insert material. Further, depending on the position of the cavity portion 8 of the mold 1, a material having a different thermal conductivity is used as the material of the insert 11 as a cooling means provided corresponding thereto. By doing so, the temperature distribution of the mold 1 can be controlled.
[0014]
That is, although only a partial cross section is shown in FIG. 1, in the multi-cavity mold 1 having three or more pieces, the material of the nest 11 of the cooling water passage portion 12 is made to the outer cavity portion 8 a. A material having higher thermal conductivity is used for the material of the insert 11b with respect to the inner cavity portion 8b than for the material of the insert 11a. Thereby, the mold temperature from the center where the mold temperature is likely to rise during casting can be controlled at the same temperature as the outer mold temperature. In addition, the insert 11a and the insert 11b are attached to the main mold 3a, and are installed so that no gap is generated between the main mold 3a and the inserts 11a and 11b. When the gap is not completely filled, a filler may be inserted between the main mold 3a and the inserts 11a and 11b.
Moreover, although the cooling water water flow part 12 is shown in the U-shape, it may be double (jet type), spiral or meandering, and the inlet and outlet are respectively connected to the cooling water supply side and the cooling water. Connected to the discharge side.
[0015]
FIG. 2 shows a cooling system of the nest 11, and the cooling water water passing portions 12 of the nest 11 are respectively connected to the cooling water tank 13 via the flow rate adjusting valve 14. A cooling water pump 15 is provided in the cooling water tank 13, and this cooling water tank 13 is connected to a cooler (chiller) 16, which is a heat exchanger. Is cooled by exchanging heat between the circulating water in the factory or the like in the cooler 16. The cooling system is a cooling water flow system in which the flow time, flow rate, cooling water temperature, etc. of the cooling water passing through each nest can be individually controlled by the management device 17, and the mold is closed from the casting machine, etc. A structure that can control the pumping pump 15, the flow rate adjusting valve 14, etc. by inputting timing signals and timer signals for opening, injection, curing, etc. and managing the cooling water flow time, flow rate, etc. It has become. The cooling water temperature is controlled to a constant temperature by the cooler 16, and the mold 1 and the cooling water flow system are closed. Further, the control device 17 monitors the flow rate and flow time of each cooling water and the mold temperature in each cavity portion, and casts by the central cavity portion depending on whether or not the temperature difference is less than a predetermined value. You may provide the management system which determines the quality of a cast product quality.
[0016]
1 and 2, even when the mold cooling system shown in FIGS. 1 and 2 is used, the center-side cavity portion 8b is closer to the outer cavity portion 8a at the time of casting. Due to the difference in the solid phase ratio between the outer side and the outer side due to heat conduction, the inner quality (sink amount) of the products in the central cavity portion 8b and the outer cavity portion 8a may change. A mold 1 of another embodiment shown in FIG. 3 shows a solution to this problem. A dam portion 18 is provided in a runner portion 9 communicating with a central cavity portion (product portion) 8b, and the cavity portion (Product part) The flow path cross-sectional area of the shortest runner part 9 among the runner parts 9 communicating with 8a, 8b is made smaller than the flow path cross-sectional areas of the other runner parts. The dam portion 18 is formed in an arc shape or a taper shape, that is, the cross section of the dam portion is, for example, a semicircular shape or a trapezoidal shape, so that the molten metal can be introduced into the cavity portion 8b without disturbing the flow of the molten metal. . Thereby, the structure of the cast product can be made uniform.
[0017]
In this way, by providing the weir portion 18 in the runner portion 9 that communicates with the central cavity portion 8b, heat dissipation from the molten metal to the mold is promoted, and the solidification rate of the molten metal in the central cavity portion when filling the molten metal is increased. The solidification rate of the molten metal in the outer cavity can be matched. Furthermore, during continuous casting, the rise in mold temperature at the weir is more likely to rise than the rise in mold temperature at the cavity, so that the final solidified part can be generated near the weir. ) Is less likely to occur. The same effect can be obtained even when a weir portion is provided in each runner portion communicating with all the cavity portions.
[0018]
As apparent from the above description, in the present invention, in the multi-cavity mold, the aluminum solidification rate in the cavity portion is made uniform, that is, the solidification start timing of aluminum (molten metal) is made uniform and the cavity portion is provided. It is possible to align the solidification rate of the introduced molten metal.
In casting, when the inflow speed of the molten metal is slow, a difference in the solidification start timing and the solidification speed is likely to occur. Therefore, in the casting mold of the present invention, the speed of the molten metal flowing into the cavity portion is 0. Optimum effects can be obtained by using in the case of 0.05 to 0.3 m / s. In addition, by forming the cavity portions at the same height position, it is possible to perform the process from the start of the flow of molten metal into the cavity portion to the completion of filling in synchronization between the respective cavity portions.
[0019]
FIG. 4 is a graph comparing (a) mold temperature and (b) strength variation in a multi-cavity mold of the prior art and the present invention. As can be seen from FIG. 4 (a), in the mold in the prior art, the mold temperature in the central cavity portion is increased to nearly 300 ° C., whereas in the mold of the present invention, the mold in the central cavity portion is used. The temperature rises only up to about 240 ° C., and the temperature difference of the mold temperature between the central cavity portion and the outer cavity portion is about 80 ° C. in the conventional mold, but about 20 ° C. in the mold of the present invention. Significant improvement. Further, as can be seen from FIG. 4 (b), regarding the variation in strength, in the conventional mold, there is a large difference in tensile strength between the product A2 by the central cavity portion and the products A1 and A3 by the outer cavity portion. However, in the mold according to the present invention, there is no difference in the tensile strength between the product A2 and the products A1 and A3, the variation is improved, and the strength is also improved.
[0020]
【The invention's effect】
Therefore, the casting mold of the present invention has the following effects.
(1) By reducing the mold temperature difference between the central cavity part and the outer cavity part, the structure of the cast product can be made uniform in the outer and central cavity parts, and the strength difference of the cast product between the cavity parts can be reduced. Can be suppressed.
(2) By reducing the mold temperature difference between the central cavity portion and the outer cavity portion, the occurrence rate (defective rate) of nest defects in the cast product can be suppressed.
(3) By providing the weir portion in the runner portion of the central cavity portion, the shrinkage nest occurrence rate of the cast product in the central cavity portion can be suppressed.
(4) By controlling the cooling water flow time and flow rate individually, it is possible to improve the ability of the molten metal during injection (filling) and minimize the curing time, thereby reducing the cycle time. It can be reduced by about 20%.
[Brief description of the drawings]
FIG. 1 is a partial sectional view of a casting mold according to one embodiment of the present invention.
FIG. 2 is a diagram illustrating a casting mold and a cooling water flow system according to the present invention.
FIGS. 3A and 3B are a plan view and a cross-sectional view of a casting mold according to another embodiment when a weir portion is provided in the runner portion.
FIG. 4 is a graph comparing (a) mold temperature and (b) product strength variation of casting molds of the present invention and the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... (For casting) Mold 2 ... Fixed mold 3 ... Movable mold 3a ... Main mold 7 ... Plunger 8, 8a, 8b ... Cavity part (product part)
9 ... runner (branch passage)
10 ... Biscuits (common passage)
DESCRIPTION OF SYMBOLS 11, 11a, 11b ... Nest 12 ... Cooling water flow-through part 13 ... Cooling water tank 14 ... Flow control valve 15 ... Cooling water pumping pump 16 ... Cooler (chiller)
18 ... weir

Claims (5)

In a casting mold comprising a movable mold and a fixed mold, and three or more cavities are formed on their mating surfaces,
The molten metal supply passage for supplying molten metal to three or more cavity portions in the mold is formed, and the molten metal supply passage is branched from the common passage and communicated with the respective cavity portions. And consist of
A casting mold characterized in that the flow path cross-sectional area of the shortest length of the branch paths is smaller than the flow path cross-sectional areas of the other branch paths. The casting mold according to claim 1 , wherein a flow passage cross-sectional area is reduced by providing a weir portion in the branch passage. The casting mold according to claim 2 , wherein the dam portion is formed in an arc shape or a taper shape. The speed of the molten metal which flows into the said cavity part is 0.05-0.3 m / s, The casting metal mold | die as described in any one of Claims 1-3 characterized by the above-mentioned. The casting mold according to any one of claims 1 to 4 , wherein the three or more cavities are formed at the same height position.

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