Casting device

Abstract

To provide a casting technique with which even in the case of being a thin and large size casting, a final solidified part can be made to stay in a non-product part and the misrun of molten metal and the entrapment of gas are not developed.SOLUTION: A casting device (20) includes a metallic mold (21), at least two electromagnetic induction pumps (40) including a first electromagnetic induction pump (40A) and a second electromagnetic induction pump (40B), at least one holding kiln (60) for holding molten metal (61) and a control part (65) for controlling the electromagnetic induction pumps (40). The first electromagnetic induction pump (40A) is connected to a first sprue (28) and configured to send the molten metal (61) in the holding kiln (60) to a first cavity (25). The second electromagnetic pump (40B) is connected to a second sprue (34) and configured to send the molten metal (61) in the holding kiln (60) to a second cavity (31). The control part (65) starts the second electromagnetic induction pump (40A) when a predetermined time difference has passed after starting the first electromagnetic induction pump (40B).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a casting apparatus for casting large, thin-walled castings. [Background technology]

[0002] A die-casting machine is known as a method for casting using a mold that can be reused repeatedly. Die-casting machines can be used to produce large, thin-walled castings such as automotive parts, but casting large, thin-walled castings requires a large, high-pressure die-casting machine. However, high-pressure, large-scale die-casting machines are very expensive.

[0003] One of the technologies that can replace die-casting machines is low-pressure casting, and various technologies related to this low-pressure casting have been proposed (see, for example, Patent Document 1 (Fig. 1)). The meaning of low-pressure casting is as follows.

[0004] [Terminology] Low pressure casting is written as low pressure die casting in English. In Japan, the word "die" is omitted and the process is written as low pressure casting.

[0005] [Conventional low-pressure casting equipment] Patent Document 1 will be explained with reference to the following figure. FIG. 10 is a diagram illustrating the basic principle of conventional low-pressure casting. As shown in FIG. 10 , low-pressure casting equipment 100 comprises a mold 102 having cavities 101L and 101R therein, a holding furnace 104 disposed below the mold 102 and filled with molten metal 103, conduits 105L and 105R whose lower ends are immersed in the molten metal 103 in the holding furnace 104 and whose upper ends are connected to the cavities 101L and 101R, an air pressure pump 106 and an air valve 107 connected to the holding furnace 104 and which apply downward air pressure to the molten metal 103, a core 109 placed in the mold 102, and a vacuum pump 111, a vacuum tank 112, and a pressure reducing valve 113 which reduce the pressure in the cavities 101L and 101R.

[0006] [Conventional low-pressure casting method] The holding furnace 104 is filled with a predetermined amount of molten metal 103. With the air valve 107 closed, the pressure reducing valve 113 is opened to reduce the pressure inside the cavities 101L and 101R to below atmospheric pressure. Simultaneously with this reduction in pressure or after an appropriate time has passed, the air valve 107 is opened. This causes the air pressure to push the upper surface of the molten metal 103 downward. As a result, the molten metal 103 is supplied to the cavities 101L and 101R through the conduits 105L and 105R. Since there are two conduits 105L and 105R, twice the amount of molten metal 103 can be supplied per unit time, making it possible to manufacture large castings.

[0007] However, the conventional low-pressure casting apparatus 100 has the following drawbacks. The molten metal 103 is pushed by the air pressure and rises in the conduits 105L and 105R, and at this time, the molten metal 103 rises at the same speed in the left conduit 105L and the right conduit 105R.

[0008] The molten metal 103 supplied from the left and right conduits 105L and 105R rises and fills the cavities 101L and 101R. The molten metal 103 is cooled and solidified by the mold 102 at a low temperature. The part that solidifies last is called the final solidification zone, and it is known that shrinkage cavities inevitably remain in this final solidification zone.

[0009] Since shrinkage cavities are a type of casting defect, they are not desirable to leave in the product. However, with the technology of Patent Document 1, it is difficult to artificially determine the position of the final solidification portion.

[0010] In recent years, vehicle bodies have come to be made of lightweight castings in addition to press-molded parts. Castings for vehicle bodies are large and contain a mixture of thin and thick sections. When the technology of Patent Document 1 is applied to such thin-walled large castings, the following new drawbacks arise.

[0011] If the flow rate of the molten metal is too slow, solidification will proceed in the thin-walled portion, causing poor running of the molten metal. As a countermeasure, the flow rate of the molten metal is increased, but if it is increased too much, the flow of the molten metal becomes turbulent in the thick-walled part, causing gas entrainment. As described above, the technique of Patent Document 1 is prone to causing poor molten metal flow and gas entrapment when casting large, thin-walled products.

[0012] In recent years, as demand for large, thin-walled castings has increased, there has been a demand for casting technology that can confine the final solidification portion to the non-product portion and prevent poor molten metal flow and gas entrapment. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Patent No. 5704641 Summary of the Invention [Problem to be solved by the invention]

[0014] An object of the present invention is to provide a casting technique that can confine the final solidification portion to a non-product portion even in the case of a thin-walled large casting, and that prevents poor molten metal flow and gas entrapment. [Means for solving the problem]

[0015] The invention of claim 1 is a casting apparatus for casting large, thin-walled castings that are a mixture of thin and thick parts, and are large in size, The casting device includes a mold, at least two electromagnetic induction pumps including a first electromagnetic induction pump and a second electromagnetic induction pump, at least one holding furnace for holding molten metal, and a control unit for controlling the electromagnetic induction pumps; the mold comprises a first cavity corresponding to the thin-walled portion, a first weir for supplying molten metal to the first cavity, a first runner for supplying molten metal to the first weir, and a first gate for supplying molten metal to the first runner, and also comprises a second cavity corresponding to the thick-walled portion and connected to the first cavity, a second weir for supplying molten metal to the second cavity, a second runner for supplying molten metal to the second weir, and a second gate for supplying molten metal to the second runner; the first electromagnetic induction pump is connected to the first sprue and serves to send the molten metal from the holding furnace to the first cavity; the second electromagnetic induction pump is connected to the second sprue and serves to send the molten metal from the holding furnace to the second cavity; the control unit performs time-delayed operation control to start the second electromagnetic induction pump when a predetermined time difference has elapsed since the first electromagnetic induction pump was started, When a connection portion between the first cavity and the second cavity is defined as an outlet of the first cavity and a connection portion between the second weir and the second cavity is defined as an inlet of the second cavity, the outlet of the first cavity and the inlet of the second cavity are set at the same height; The predetermined time difference is the difference between a first arrival time from when the first electromagnetic induction pump is started until the molten metal reaches the outlet of the first cavity and a second arrival time from when the second electromagnetic induction pump is started until the molten metal reaches the inlet of the second cavity.

[0016] The invention according to claim 2 is the casting apparatus according to claim 1, In addition to the time-staggered operation control, the control unit The present invention is characterized in that individual pressure control is performed to make the discharge pressure of the second electromagnetic induction pump lower than the discharge pressure of the first electromagnetic induction pump.

[0017] The invention according to claim 3 is the casting apparatus according to claim 1, In addition to the time-staggered operation control, the control unit The temperature difference control is performed to lower the output of the heater built into the second electromagnetic pump compared to the output of the heater built into the first electromagnetic induction pump.

[0018] The invention according to claim 4 is the casting apparatus according to claim 1, The cross-sectional area of the second weir is larger than that of the first weir.

[0019] The invention according to claim 5 is the casting apparatus according to claim 1, The first cavity is disposed at an inclination that is upward from the first weir, and an outlet of the first cavity is connected to the second cavity. [Effects of the Invention]

[0020] In the invention according to claim 1, the control unit performs time-staggered operation control, that is, by time-staggered operation control, the second electromagnetic induction pump is started after a predetermined time lag has elapsed since the first electromagnetic induction pump was started. The thin walled section begins to solidify in the first cavity, which is first supplied with molten metal by the first electromagnetic induction pump. The thicker part begins to solidify in the second cavity, which is supplied with molten metal by the second electromagnetic induction pump. In other words, solidification proceeds in the order of the first cavity and then the second cavity.

[0021] Furthermore, since the molten metal is supplied from the second electromagnetic induction pump, the molten metal in the second weir, the second runner, and the second sprue, which are close to the second electromagnetic induction pump, solidifies later than the molten metal in the second cavity. Of the second weir, second runner, and second spout, the second runner and second spout solidify the slowest.

[0022] As a result, the final solidification part is formed in the second runner or the second gate. Because the non-product part is created by the second weir, the second runner, and the second gate, the final solidification part remains in the non-product part. Therefore, the present invention provides a casting technique that can confine the final solidification portion to a non-product portion even in the case of a thin-walled large casting.

[0023] In the invention according to claim 2, in addition to the time-difference operation control, the control unit performs individual pressure control to make the discharge pressure of the second electromagnetic induction pump lower than the discharge pressure of the first electromagnetic induction pump. That is, the first electromagnetic induction pump is set to high pressure, and the second electromagnetic induction pump is set to low pressure. By setting the first electromagnetic induction pump to a high pressure, the flow rate of the molten metal in the first cavity increases, resulting in good molten metal circulation. By setting the second electromagnetic induction pump to a low pressure, the flow rate of the molten metal in the second cavity is reduced, preventing gas entrainment. Therefore, the present invention provides a casting technique that can confine the final solidification portion to a non-product portion even in the case of a thin-walled large casting, and that prevents poor molten metal flow and gas entrapment.

[0024] In the invention according to claim 3, the control unit performs temperature difference control in addition to time-difference operation control, in which the output of the heater built into the second electromagnetic pump is lower than that of the heater built into the first electromagnetic induction pump. That is, the first electromagnetic induction pump supplies high-temperature molten metal to the first cavity. High temperatures increase the fluidity of the molten metal and allow more time for it to solidify, resulting in better molten metal flow in the first cavity. Therefore, the present invention provides a casting technique that can confine the final solidification portion to a non-product portion even in the case of a thin-walled large casting, and that prevents poor molten metal flow.

[0025] In the invention according to claim 4, the cross-sectional area of the second weir is made larger than the cross-sectional area of the first weir. That is, the cross-sectional area of the first weir is made small and the cross-sectional area of the second weir is made large. The smaller the cross-sectional area, the faster the flow rate, which increases the flow rate of the molten metal in the first cavity and improves the molten metal circulation. The larger the cross-sectional area, the slower the flow rate, preventing gas entrainment in the second cavity. Therefore, the present invention provides a casting technique that can confine the final solidification portion to a non-product portion even in the case of a thin-walled large casting, and that prevents poor molten metal flow and gas entrapment.

[0026] In the invention according to claim 5, the first cavity is disposed at an inclination that forms an upward gradient from the first weir, and the outlet of the first cavity is connected to the second cavity. If the first cavity is on an upward slope, the molten metal supplied by the first electromagnetic induction pump will completely fill the first cavity before flowing into the second cavity. Since the molten metal completely fills the first cavity, the casting quality in the thin-walled part will be good. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic perspective view of a thin-walled large casting. [Figure 2] FIG. [Figure 3] 1 is a diagram illustrating the principle of a casting device according to the present invention. [Figure 4] FIG. 1 is a cross-sectional view of an electromagnetic induction pump. [Figure 5] 1(a) to 1(d) are diagrams illustrating the main parts of the casting process. [Figure 6] 1(a) to 1(d) are diagrams illustrating the casting process. [Figure 7] FIG. 10 is a diagram illustrating the first half of a control flow performed by a control unit. [Figure 8] FIG. 10 is a diagram illustrating the latter half of the control flow performed by the control unit. [Figure 9] 10(a) and 10(b) are diagrams illustrating a modified example of the mold. [Figure 10] FIG. 1 is a diagram illustrating the basic principle of conventional low-pressure casting. DETAILED DESCRIPTION OF THE INVENTION

[0028] An embodiment of the present invention will be described below with reference to the accompanying drawings. [Example]

[0029] [Thin-walled large castings] As shown in FIG. 1, the thin-walled large casting 10 is a large casting having a vertical dimension A of 1500 mm (maximum), a horizontal dimension B of 1500 mm (maximum), and a height of 1000 mm (maximum), and is a casting that has a mixture of thin-walled portions 11 having a thickness of, for example, 2 to 4 mm and thick-walled portions 12 that are thicker than the thin-walled portions 11. Such a thin-walled large casting 10 is suitable for use as a part of an automobile body made of light metal, i.e., as an automobile body component part.

[0030] The thin-walled, large casting 10 shown in FIG. 1 is a schematic representation of a certain type of vehicle body component, but the overall shape of the thin-walled, large casting 10 is not limited to this example. The point is that it is a casting that has a mixture of thin-walled portions 11 and thick-walled portions 12, and it is sufficient if it is a large casting, and the shape and size may be changed as desired.

[0031] The light metal material is preferably an aluminum alloy, a magnesium alloy, a zinc alloy, a tin alloy, or the like.

[0032] [Casting method] The arrangement of weirs, runners, and gates according to the shape and size of the casting is called a casting plan. An example of a casting plan for a large, thin-walled casting 10 is explained with reference to FIG.

[0033] 2, thin-walled portion 11 extends diagonally downward from one end of thick-walled portion 12, which extends almost horizontally. That is, thin-walled portion 11 slopes upward, and an upper end 11a of thin-walled portion 11 is connected to thick-walled portion 12.

[0034] Therefore, in the present invention, a first gate section 28m (this is the part cast at the first gate 28 described below, and is marked with the symbol m; the same applies below) is placed below the lower end 11b of the thin-walled section 11, and a first runner section 27m for spreading the molten metal is placed at the upper end of this first gate section 28m, and multiple first weir sections 26m (four in this example) are raised from this first runner section 27m, and these first weir sections 26m are connected to the lower end 11b of the thin-walled section 11.

[0035] In addition, in the present invention, a second gate portion 34m is arranged below the thick-walled portion 12, and a second runner portion 33m for spreading the molten metal is arranged at the upper end of this second gate portion 34m, and multiple (four in this example) second weir portions 32m are raised from this second runner portion 33m, and these second weir portions 32m are connected to the thick-walled portion 12.

[0036] [Cross-sectional area of weir] The sum (total) of the cross-sectional areas of the first weir sections 26m is expressed as the cross-sectional area S1 of one first weir section 26m multiplied by the number n1, and the sum (total) of the cross-sectional areas of the second weir sections 32m is expressed as the cross-sectional area S2 of one second weir section 32m multiplied by the number n2. In this example, since n1 and n2 are both 4, the cross-sectional area of the first weir 26m and the cross-sectional area of the second weir 32m can be compared by setting the first weir 26m as S1 and the second weir 32m as S2.

[0037] [Casting equipment] A casting apparatus 20 for producing the above-described thin-walled large casting 10 will be described with reference to FIG. As shown in FIG. 3, casting apparatus 20 includes mold 21, at least two electromagnetic induction pumps 40, at least one holding furnace 60 for holding molten metal 61, and control unit 65 for controlling electromagnetic induction pump 40.

[0038] Since there are at least two electromagnetic induction pumps 40, when it is necessary to distinguish between the two, the designations "1" and "2" are added and an alphabet is added to the reference numeral, such as first electromagnetic induction pump 40A and second electromagnetic induction pump 40B.

[0039] [Mold] The structure of the mold 21 is determined in consideration of removing (demolding) a thin-walled large casting (FIG. 2, reference numeral 10), and is composed of, for example, a lower mold 22, a middle mold 23, and an upper mold 24. It is possible to provide a multi-stage intermediate mold 23, add a slide mold, or add a core, and the structure of the mold 21 is not limited to that of the embodiment.

[0040] The mold 21 is provided with a first cavity 25 corresponding to the thin-walled portion, a first weir 26 for supplying molten metal to the first cavity 25, a first runner 27 for supplying molten metal to the first weir 26, and a first gate 28 for supplying molten metal to the first runner 27, as well as a second cavity 31 corresponding to the thick-walled portion and connected to the first cavity 25, a second weir 32 for supplying molten metal to the second cavity 31, a second runner 33 for supplying molten metal to the second weir 32, and a second gate 34 for supplying molten metal to the second runner 33.

[0041] When the connection portion between the first cavity 25 and the second cavity 31 is the outlet 25a of the first cavity, and the connection portion between the second weir 32 and the second cavity 31 is the inlet 31a of the second cavity, the outlet 25a of the first cavity and the inlet 31a of the second cavity are set to the same height (including approximately the same height).

[0042] The mold 21 is kept at a lower temperature than the molten metal 61. Therefore, the supplied molten metal 61 is gradually cooled, and the liquid changes to a solid (i.e., solidifies). Because the first cavity 25 is narrow, solidification progresses quickly to the center. Conversely, because the second cavity 31 is wide, it takes time for solidification to reach the center.

[0043] [Electromagnetic induction pump] The electromagnetic induction pump 40 is a pump that utilizes electromagnetic induction. Its basic structure will be described with reference to FIG.

[0044] As shown in FIG. 4, the electromagnetic induction pump 40 includes a base flange 41, a conductor pipe 42 extending vertically through the base flange 41, an iron core member 43 housed in the conductor pipe 42, a lower coil 44 surrounding the lower part of the conductor pipe 42, a lower case 45 surrounding the lower coil 44 and suspended from the base flange 41, an upper coil 46 surrounding the upper part of the conductor pipe 42, an upper case 47 surrounding the upper coil 46 and mounted on the base flange 41, a discharge pipe 48 extending upward from the conductor pipe 42, a melt level gauge 49 surrounding the discharge pipe 48, a first heater 51 surrounding the lower coil 44, a second heater 52 surrounding the conductor pipe 42 between the first heater 51 and the base flange 41, a third heater 53 surrounding the conductor pipe 42 above the base flange 41, and a fourth heater 54 surrounding the discharge pipe 48.

[0045] When the lower coil 44 is energized, the molten metal (FIG. 3, reference numeral 61) is pulled up by Fleming's left-hand principle. Next, when the upper coil 46 is energized and the lower coil 44 is de-energized, the molten metal is raised to the level gauge 49. The level of the level gauge 49 becomes the "standby level."

[0046] According to Fleming's left-hand rule, increasing the current increases the force. When the current in the upper coil 46 is further increased, the molten metal exceeds the level gauge 49 and is discharged above the discharge pipe 48.

[0047] 3, first electromagnetic induction pump 40A is connected to first gate 28 and serves to send molten metal 61 from holding furnace 60 to first cavity 25. The second electromagnetic induction pump 40B is connected to the second gate 34 and serves to feed the molten metal 61 from the holding furnace 60 to the second cavity 31.

[0048] The control unit 65 shown in FIG. 3 performs time-lag operation control such that the second electromagnetic induction pump 40B is started when a predetermined time has elapsed since the start of the first electromagnetic induction pump 40A. The final solidification portion under the time-lag operation control and the predetermined time used in the time-lag operation control will be described with reference to FIGS.

[0049] 5(a), molten metal 61 is supplied to the first gate 28 as shown by the arrow (1), and passes through the first runner 27 and the first weir 26, rising up inside the first cavity 25 and filling the first cavity 25. The level of the top surface of the molten metal 61 when filled is designated as L1. Since the outlet 25 a of the first cavity 25 and the inlet 31 a of the second cavity 31 are at the same height, the upper surface level L 1 coincides with the bottom of the second cavity 31 .

[0050] As the supply of the molten metal 61 continues in the direction of the arrow (1), the molten metal 61 overflows from the first cavity 25, flows into the second cavity 31, and begins to accumulate at the bottom of the second cavity 31, as shown in FIG. 5(b). Figure 5(c) is an enlarged view of part C in Figure 5(b), and as shown in Figure 5(c), the molten metal 61 rises but is held together by surface tension and does not flow into the second weir 32. The upper surface level of the molten metal 61 at this time is designated as L2. This upper surface level L2 is higher than the upper surface level L1 shown in Figure 5(a).

[0051] 5(d), the upper surface level of the molten metal 61 reaches L3, which is higher than L2, and a portion of the molten metal 61 drips down onto the second weir 32. Drooping of this magnitude is acceptable if it is small in scale.

[0052] The process from when the molten metal 61 is at the standby level until the final solidified portion 14 is formed will be described with reference to FIGS. 6(a) to 6(d). In FIG. 6(a), the molten metal 61 is held at a standby level. Based on the volumes of the first cavity 25, the first weir 26, the first runner 27 and the first sprue 28, and the settings of the first electromagnetic induction pump (Figure 3, symbol 40A), the time T1 required for the left part of the figure to travel from the standby level through the first cavity 25 to the upper surface level L1 is determined.

[0053] [First arrival time] This required time T1 is to be read as the first arrival time T1 from when the first electromagnetic induction pump (FIG. 3, reference numeral 40A) is started until the molten metal 61 reaches the outlet 25a of the first cavity 25.

[0054] Similarly, the time T2 required for the upper surface level to reach L1 from the standby level is determined based on the volumes of the second weir 32, the second runner 33 and the second sprue 34 and the settings of the second electromagnetic induction pump (Figure 3, symbol 40B) in the right part of the figure.

[0055] [Second arrival time] This required time T2 is to be read as a second arrival time T2 from when the second electromagnetic induction pump (FIG. 3, reference numeral 40B) is started until the molten metal 61 reaches the inlet 31a of the second cavity 31.

[0056] [Predetermined time difference] The predetermined time difference is determined by the formula: (first arrival time T1 - second arrival time T2) = predetermined time difference. The predetermined time difference is, for example, about 1 second.

[0057] Therefore, the first electromagnetic induction pump (40A in FIG. 3) is started, and one second later the second electromagnetic induction pump (40B in FIG. 3) is started.

[0058] As time passes, as shown in FIG. 6(b), the first cavity 25 shown on the left side of the figure is filled with molten metal 61, and at this time the molten metal 61 reaches the inlet 31a of the second cavity 31 shown on the right side of the figure.

[0059] After a further time has passed, the second cavity 31 is filled with the molten metal 61 as shown in FIG. 6(c).

[0060] In Figure 6(c), because the second cavity 31 has a large volume, the molten metal 61 solidifies relatively slowly from the surface to the center of the second cavity 31. While this solidification is in progress, the supply of molten metal 61 indicated by arrow (2) is maintained. This maintenance is called "holding pressure," and by compensating for the shrinkage of the volume of the molten metal 61 due to solidification, it prevents the occurrence of "shrinkage cavities" in the casting after solidification. During pressure holding, the molten metal 61 in the second weir 32, the second runner 33 and the second gate 34 is in an unsolidified state.

[0061] Then, with the passage of time, solidification progresses in the order of the surface of the second cavity 31 → the center of the second cavity 31 → the second weir 32 → the second runner 33 → the second gate 34 . As a result, the final solidified portion 14 remains in the second runner 33 or the second gate 34 .

[0062] Once solidification is complete, the mold is removed. This results in the product portion 15, the non-product portion 16A on the left, and the non-product portion 16B on the right, as shown in Figure 6(d). A small amount of non-product portion 16C is attached to the product portion 15, but this non-product portion 16C is removed. After removal, the product portion 15 becomes the thin-walled large casting 10 shown in Figure 1.

[0063] [Final solidification part] The final solidification portion 14 remains in the non-product portion 16B on the right. That is, the present invention provides a casting technique that can artificially retain the final solidification portion 14 in the non-product portion 16B in a thin-walled large casting 10.

[0064] In the present invention, the setting of the predetermined time difference and the first and second arrival times T1 and T2 is important. There is no problem if the upper surface level L1 shown in Fig. 5(a) becomes the level L2 shown in Fig. 5(b) due to a slight deviation in the setting. Furthermore, the upper surface level L1 is allowed up to L3 shown in Fig. 5(d). Therefore, sufficient flexibility is ensured in setting the predetermined time difference.

[0065] In addition, the "predetermined time difference" is adjusted by repeating trials (test casting) and adjusting the time difference depending on the quality of the product (FIG. 6(d), reference numeral 15). As a result, the present invention can be easily implemented.

[0066] It is preferable to add individual pressure control, or temperature difference control, or both individual pressure control and temperature difference control to the time-staggered operation control performed using a "predetermined time difference." These controls will be explained based on the flow charts of FIGS.

[0067] 7, a "predetermined time difference tset" is set at step number (hereinafter abbreviated as ST) 01. tset is, for example, 1.0 second.

[0068] Next, in ST02, it is specified whether or not individual pressure control is to be performed. When this is carried out, the discharge pressure P1 of the first electromagnetic induction pump is set in ST03, and the discharge pressure P2 of the second electromagnetic induction pump is set in ST04.

[0069] Each of the first electromagnetic induction pump and the second electromagnetic induction pump is VVVF (voltage conversion, frequency conversion) controlled by the control unit 65. The discharge pressure can be increased by increasing the voltage, and decreased by decreasing the voltage.

[0070] In the present invention, it is recommended that the discharge pressure P2 of the second electromagnetic induction pump be lower than the discharge pressure P1 of the first electromagnetic induction pump. This type of individual control of the discharge pressures is called individual pressure control. The effects of individual pressure control will be described later.

[0071] In ST05, it is confirmed that the discharge pressure P2 is lower (low pressure) than the discharge pressure P1. If not, the user is prompted to correct the set value (ST06) and the process returns to ST03.

[0072] If the answer is NO in ST02 or YES in ST05, proceed to ST07. In ST07, it is specified whether or not to perform temperature difference control. When this is carried out, the heater output H1 of the first electromagnetic induction pump is set in ST08, and the heater output H2 of the second electromagnetic induction pump is set in ST09.

[0073] The heater output is set for all or some of the first to fourth heaters 51 to 54 shown in Fig. 4. In other words, increasing the output of the first to fourth heaters 54 increases the temperature of the molten metal 61. By providing a difference in output, it is possible to provide a difference in temperature between the molten metal discharged by the first electromagnetic induction pump and the molten metal discharged by the second electromagnetic induction pump.

[0074] In the present invention, the heater output H2 built into the second electromagnetic induction pump is lower than the heater output H1 built into the first electromagnetic induction pump. As a result, a difference in the temperature of the molten metal occurs. Creating a difference in the temperature of the molten metal is called temperature difference control. The effects of temperature difference control will be described later.

[0075] In ST10, it is confirmed that the second heater output H2 is smaller than the first heater output H1. If not, the user is prompted to correct the set value (ST11) and returns to ST08. If the answer is NO in ST07 or YES in ST10, proceed to Figure 8.

[0076] When a mold clamping completion signal is received in ST12 of FIG. 8, the first electromagnetic induction pump is started (ST13). The time tact that has elapsed since starting is counted (ST14). In ST15, it is checked whether the elapsed time tact has reached the predetermined time difference tset. If not, the process waits for the time difference to reach the predetermined time difference tset.

[0077] When it reaches the predetermined temperature, the second electromagnetic induction pump is started (ST16). That is, the control unit starts the second electromagnetic induction pump when a predetermined time difference has elapsed since the first electromagnetic induction pump was started. In ST17, it is checked whether hot water supply and pressure maintenance have been completed. If not, the process waits for completion. When this is complete, the first electromagnetic induction pump and the second electromagnetic induction pump are stopped (ST18).

[0078] [Effect of individual pressure control] Next, the effect of the individual pressure control will be described. In the present invention, in addition to the time-lag operation control, it is recommended to perform individual pressure control in which the discharge pressure of the second electromagnetic induction pump is made lower than the discharge pressure of the first electromagnetic induction pump. When the discharge pressure of the first electromagnetic induction pump becomes higher than the discharge pressure of the second electromagnetic induction pump through individual pressure control, the molten metal pressure increases along the arrow (1) in Figure 5(a). This causes the molten metal 61 to be strongly pushed into the narrow first cavity 25. As a result, even though solidification begins from the surface of the first cavity 25, the molten metal 61 reaches every corner of the first cavity 25 before that happens. This improves the running of the molten metal and improves the casting quality.

[0079] At the same time, when the discharge pressure of the second electromagnetic induction pump becomes lower than the discharge pressure of the first electromagnetic induction pump through individual pressure control, the molten metal pressure along arrow (2) in Figure 6(b) decreases, and the molten metal then slowly rises within the second cavity 31, reaching Figure 6(c). If the flow velocity of the molten metal is high, it will entrain the surrounding gas, but if the flow velocity is low, this is not a concern. As a result, high-quality castings can be obtained without gas entrainment.

[0080] [Effect of temperature difference control] Next, the effect of the temperature difference control will be described. In the present invention, in addition to the time difference operation control, it is recommended to perform temperature difference control in which the output of the heater built into the second electromagnetic pump is lower than that of the heater built into the first electromagnetic induction pump. By controlling the temperature difference, the molten metal 61 indicated by the arrow (1) in FIG. 5(a) becomes hotter. The fluidity of the molten metal increases as the temperature increases. In addition, the molten metal 61 has more time to solidify as the temperature increases. As a result, the molten metal 61 reaches every corner of the narrow first cavity 25. This improves the running of the molten metal and improves the casting quality.

[0081] The temperature difference control can also be implemented by creating a difference between the temperature of the intermediate stalk on the first electromagnetic induction pump side and the temperature of the intermediate stalk on the second electromagnetic induction pump side.

[0082] In addition, the temperature difference control lowers the temperature of the molten metal 61 indicated by the arrow (2) in Fig. 6(b). Because the second cavity 31 has a large volume, even if solidification progresses from the surface, it takes time for the molten metal 61 to reach the center, and the molten metal 61 reaches every corner of the second cavity 31. By keeping the temperature low, oxidation of the molten metal 61 can be suppressed, and the casting quality is improved.

[0083] [Cross-sectional area of weir] In FIG. 2, if the cross-sectional area of the first weir 26 is S1 and the cross-sectional area of the second weir 32 is S2, it is recommended that the cross-sectional area S2 of the second weir be larger than the cross-sectional area S1 of the first weir 26. When the cross-sectional area S1 of the first weir 26 is reduced, the flow velocity of the molten metal 61 indicated by the arrow (1) in FIG. 5(a) is increased by the first weir 26. As a result, the molten metal 61 flows into the first cavity 25 at a high speed. As a result, the running property of the molten metal is improved, similar to when the pressure is increased.

[0084] In addition, when the cross-sectional area S2 of the second weir 32 is increased, the flow velocity of the molten metal indicated by the arrow (2) in FIG. 6(b) is slowed down by the second weir 32. As a result, the molten metal 61 flows into the second cavity 31 at a slow speed. As a result, gas entrainment is prevented in the same way as when the pressure is reduced.

[0085] [Example of mold modification] The thin-walled large casting 10 described in FIG. 1 may be a casting obtained using the mold 21B shown in FIG. 9(a) or a casting obtained using the mold 21C shown in FIG. 9(b). 9(a) and 9(b), the same components as those in FIG. 3 are designated by the same reference numerals as in FIG. 3, and detailed descriptions thereof will be omitted.

[0086] As shown in FIG. 9(a), in the mold 21B, the first cavity 25 extends horizontally, and the outlet 25a of the first cavity 25 is connected to the second cavity 31.

[0087] Alternatively, as shown in FIG. 9(b), in a mold 21C, the first cavity 25 has a downward slope, and an outlet 25a of the first cavity 25 is connected to the second cavity 31. However, if you turn it upside down, it becomes Figure 5(a), so Figure 9(b) can be substituted for Figure 5(a).

[0088] As a result, many thin-walled large castings can be cast using either the mold 21 shown in FIG. 3 or the mold 21B shown in FIG. 9(a). Therefore, the mold 21 shown in FIG. 3 and the mold 21B shown in FIG. 9(a) will be compared and examined.

[0089] Many thin-walled large castings 10 have complex shapes, and a mold 21 having an inclined first cavity 25 and a horizontal second cavity 31 as shown in FIG. 3 is more suitable than a mold having a horizontal first cavity 25 and a horizontal second cavity 31 as shown in FIG. 9(a). Therefore, in terms of configuration, the mold 21 shown in FIG. 3 is superior.

[0090] Furthermore, in the mold 21 of FIG. 3, as explained in FIG. 5(a), the upper surface level L1 of the molten metal 61 is clearly and easily determined.

[0091] 9(a), the molten metal 61 supplied to the first cavity 25 overflows into the second cavity 31 before filling the first cavity 25. As a result, the upper surface level L1 of the molten metal 61 becomes unclear and is not easily determined. Therefore, the mold 21 shown in FIG. 3 is superior in terms of casting.

[0092] In view of the above, a casting apparatus 20 including a mold 21 in which the first cavity 25 is formed at an upward slope from the first gate 28 and the outlet 25a of the first cavity 25 is connected to the second cavity 31 is recommended. If the first cavity 25 has an upward slope, the molten metal 61 supplied by the first electromagnetic induction pump 40A will completely fill the first cavity 25 before flowing into the second cavity 31. Since the molten metal 61 completely fills the first cavity 25, a special effect is obtained in that the casting quality of the thin-walled portion 11 becomes good.

[0093] In the above description, the formula (first arrival time T1-second arrival time T2)=predetermined time difference is used in FIG. 6(a). 3, however, when the discharge pressure of first electromagnetic induction pump 40A is significantly increased, first arrival time T1 becomes shorter than expected. Alternatively, when the discharge pressure of second electromagnetic induction pump 40B is significantly decreased, second arrival time T2 becomes longer than expected.

[0094] Alternatively, depending on the structure of the mold 21, the following may occur. When the distance along the molten metal flow in the first cavity 25 is significantly short, the first arrival time T1 becomes shorter than expected. Alternatively, when the distance along the molten metal flow in one or all of the second weir 32, the second runner 33, and the second gate 34 becomes long, the second arrival time T2 becomes longer than expected.

[0095] There may be other reasons why the first arrival time T1 is shorter than expected and the second arrival time T2 is longer than expected. In this case, the following modification can be used to address the issue.

[0096] [Modifications according to the present invention] The formula for calculating the predetermined time difference is as follows: (Second arrival time T2 - First arrival time T1) = Predetermined time difference

[0097] The invention based on this modified example is as follows. A casting apparatus for casting large, thin-walled castings that are a mixture of thin and thick parts, The casting device includes a mold, at least two electromagnetic induction pumps including a first electromagnetic induction pump and a second electromagnetic induction pump, at least one holding furnace for holding molten metal, and a control unit for controlling the electromagnetic induction pumps; the mold comprises a first cavity corresponding to the thin-walled portion, a first weir for supplying molten metal to the first cavity, a first runner for supplying molten metal to the first weir, and a first gate for supplying molten metal to the first runner, and also comprises a second cavity corresponding to the thick-walled portion and connected to the first cavity, a second weir for supplying molten metal to the second cavity, a second runner for supplying molten metal to the second weir, and a second gate for supplying molten metal to the second runner; the first electromagnetic induction pump is connected to the first sprue and serves to send the molten metal from the holding furnace to the first cavity; the second electromagnetic induction pump is connected to the second sprue and serves to send the molten metal from the holding furnace to the second cavity; the control unit performs time-delayed operation control to start the first electromagnetic induction pump when a predetermined time difference has elapsed since the second electromagnetic induction pump was started, When a connection portion between the first cavity and the second cavity is defined as an outlet of the first cavity and a connection portion between the second weir and the second cavity is defined as an inlet of the second cavity, the outlet of the first cavity and the inlet of the second cavity are set at the same height; a first electromagnetic induction pump for starting the first cavity and a second electromagnetic induction pump for starting the second cavity; a second electromagnetic induction pump for starting the first cavity and a first electromagnetic induction pump for starting the first cavity;

[0098] [Effect of change example] 6(b), the supply of molten metal 61 starts as indicated by arrow (2). After a predetermined time lag (for example, 1 second) has elapsed, the supply of molten metal 61 starts as indicated by arrow (1). Although the molten metal 61 of arrow (2) arrives first, when the molten metal 61 of arrow (2) arrives at the inlet 31a of the second cavity, the molten metal 61 of arrow (1) arrives at the outlet 25a of the first cavity at the same time (including almost the same time). After that, the molten metal 61 of arrow (2) and the molten metal 61 of arrow (1) flow into the second cavity 31, and the state reaches FIG. 6(c).

[0099] [Effect of change example] 6(c), the molten metal 61 solidifies in the order of the first cavity 25, the second cavity 31, the second weir 32, and the second runner 33. That is, among the second weir 32, the second runner 33, and the second gate 34, the second runner 33 and the second gate 34 solidify last.

[0100] As a result, the final solidification portion 14 is formed in the second runner 33 or the second gate 34. Since the non-product portion 16B is formed by the second weir 32, the second runner 33, and the second gate 34, the final solidification portion 14 is reliably kept in the non-product portion 16B. Therefore, the present invention provides a casting technique that can confine the final solidification portion to a non-product portion even in the case of a thin-walled large casting.

[0101] In addition, this modification can accommodate significant changes in the mold structure and significant changes in the settings of the electromagnetic induction pump.

[0102] Although two electromagnetic induction pumps 40 are shown in Fig. 3, three or more pumps may be used, as this allows for the production of larger and more complex castings.

[0103] 3, multiple electromagnetic induction pumps 40A, 40B are mounted on one holding furnace 60, but multiple holding furnaces 60 may be provided, with the first electromagnetic induction pump 40A mounted on the first holding furnace and the second electromagnetic induction pump 40B mounted on the second holding furnace. This has the advantage that the temperature of the molten metal 61 can be controlled for each holding furnace 60. In addition, if necessary, an aluminum alloy of one composition can be stored in the first holding furnace, and an aluminum alloy of a different composition can be stored in the second holding furnace, enabling casting similar to two-shot molding performed with resin molding technology. [Industrial Applicability]

[0104] The present invention is suitable for a casting apparatus for casting large, thin-walled castings that have a mixture of thin and thick portions. [Explanation of symbols]

[0105] 10...large thin-walled casting, 11...thin-walled section, 12...thick-walled section, 14...final solidification section, 15...product section, 16A, 16B, 16C...non-product section, 20...casting apparatus, 21...mold, 25...first cavity, 25a...outlet of first cavity, 26...first weir, 27...first runner, 28...first sprue, 31...second cavity, 31a...inlet of second cavity, 32...second weir, 33...second runner, 34...second sprue, 40...electromagnetic induction pump, 40A...first electromagnetic induction pump, 40B...second electromagnetic induction pump, 60...holding furnace, 61...molten metal, 65...control section, S1...cross-sectional area of first weir, S2...cross-sectional area of second weir, T1...first arrival time, T2...second arrival time.

Claims

1. A casting apparatus for casting large, thin-walled castings that are a mixture of thin and thick parts, The casting device includes a mold, at least two electromagnetic induction pumps including a first electromagnetic induction pump and a second electromagnetic induction pump, at least one holding furnace for holding molten metal, and a control unit for controlling the electromagnetic induction pumps; the mold comprises a first cavity corresponding to the thin-walled portion, a first weir for supplying molten metal to the first cavity, a first runner for supplying molten metal to the first weir, and a first gate for supplying molten metal to the first runner; a second cavity corresponding to the thick-walled portion and connected to the first cavity, a second weir for supplying molten metal to the second cavity, a second runner for supplying molten metal to the second weir, and a second gate for supplying molten metal to the second runner; the first electromagnetic induction pump is connected to the first gate and serves to send the molten metal from the holding furnace to the first cavity; the second electromagnetic induction pump is connected to the second sprue and serves to send the molten metal from the holding furnace to the second cavity; the control unit performs time-delayed operation control to start the second electromagnetic induction pump when a predetermined time difference has elapsed since the first electromagnetic induction pump was started, When a connection portion between the first cavity and the second cavity is defined as an outlet of the first cavity and a connection portion between the second weir and the second cavity is defined as an inlet of the second cavity, the outlet of the first cavity and the inlet of the second cavity are set at the same height, a first electromagnetic induction pump for starting the molten metal and a second ...

2. The casting apparatus according to claim 1, In addition to the time-staggered operation control, the control unit A casting apparatus characterized in that individual pressure control is performed to make the discharge pressure of the second electromagnetic induction pump lower than the discharge pressure of the first electromagnetic induction pump.

3. The casting apparatus according to claim 1, In addition to the time-staggered operation control, the control unit A casting apparatus characterized in that temperature difference control is performed to lower the output of the heater built into the second electromagnetic pump compared to the output of the heater built into the first electromagnetic induction pump.

4. The casting apparatus according to claim 1, A casting apparatus characterized in that the cross-sectional area of the second weir is larger than the cross-sectional area of the first weir.

5. The casting apparatus according to claim 1, A casting apparatus characterized in that the first cavity is disposed at an incline upward from the first weir, and an outlet of the first cavity is connected to the second cavity.

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