JP2011000597A - Pressure casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure casting method for obtaining a product having high dimensional precision and also high denseness.SOLUTION: When continuous casting is performed by repeating: a step where a molten metal is filled into a die cavity formed by a fixed die, a movable die and an insert die for pressurizing a molten metal via a molten metal inflow port; a step where the insert die is pulled back by a prescribed distance in a direction of increasing the volume of the die cavity during the step of filling the die cavity with the molten metal; a step where, after the die cavity is filled with the molten metal, the inflow port of a molten metal is closed; and a step where the insert die is progressed so as to pressurize the molten metal filled into the die cavity, the prescribed distance of pulling back the insert die is regulated in such a manner that the pressurization part by the insert die in a forming stock is set in a prescribed dimensional range.

Description

  According to the present invention, when casting a cast product using a casting machine, after the molten metal is filled into the mold cavity, the molten metal inflow path is closed, and the molten metal in the mold cavity is added by the pressurizing means attached to the mold. The present invention relates to a pressure casting method that suppresses the occurrence of internal defects and maintains the dimensional accuracy of a cast product.

  Conventionally, a squeeze casting method is known as a method for obtaining a high-quality cast product, in which a molten metal is filled into a mold at a low speed and generally pressurized with a metal pressure of about 70 MPa or more, mainly about 100 MPa. By utilizing this method, important safety parts such as wheels, engine blocks, and knuckles with high density and less shrinkage are produced. However, in this method, when filling the mold cavity with the molten metal, the molten metal is once poured into a cylindrical container called a sleeve and cast, so that oxide is generated on the molten metal surface when pouring into the sleeve. As a result, the mechanical properties of the cast product are dispersed, and a filter such as a wire mesh that removes oxides from the mold entrance is required to stabilize the mechanical properties. In addition, in a casting machine with high metal pressure, it is necessary to increase the mold closing force in order to prevent metal blowout from the mold, or it becomes equipment with high hydraulic pressure to increase the metal pressure. It was expensive.

  In addition, in the low pressure casting method, a cylindrical stalk that pours molten metal into the mold is always immersed, so that after the pouring, the oxide floats on the molten metal surface where the stalk is immersed, and this oxide floats. It was mixed in the casting and caused variations in the mechanical properties of the casting. For this reason, a filter such as a wire net that removes oxide at the mold entrance is required. In addition, in the low-pressure casting method, since the solidification rate of the shaped material is slow, a nest is generated at the final solidified portion, resulting in a decrease in mechanical properties.

  As a method for solving these problems, a method disclosed in Patent Document 1 below is known. This method is detachable in which an amount of molten metal required for one casting is accommodated in an apparatus including a closing means for closing a molten metal inflow gate and a pressurizing means for pressurizing the molten metal in the closed mold cavity. It is characterized by using a pressure pan, and if the surface of the molten metal held in the pan is cleaned, the above-mentioned problems of the low pressure casting and the pressure casting method having a sleeve can be solved. Can do. In addition, in this device, since the pressure is applied directly to the molten metal with a wide cross-sectional area without applying a method of applying pressure to the molten metal through a narrow gate port through which the molten metal enters, the conventional manufacturing method has a long pressurization duration. The product can be made with a small pressure device.

  Further, in the pressure casting method, various inventions described in the following patent documents relating to pressure conditions have been proposed in order to obtain a sound casting product with high density. In the pressure casting method disclosed in the following Patent Document 2, the product is decelerated before the mold cavity is completely filled, and then the pressure is gradually increased to prevent burrs from being blown, thereby obtaining a product with high density. I am doing so.

  Further, in the invention described in Patent Document 3 below, pressure is increased in two stages to prevent hot water splashing from the mold and to obtain a product with high internal quality.

  Further, in the invention described in Patent Document 4 below, the pressurizing force of the pressurizing plunger is feedback-controlled to pressurize so as to match the master curve.

  Further, in the invention described in Patent Document 5 below, in order to obtain a casting for gravity casting in which the hot water is good and the residual bubbles are small, a vent hole is provided at the tip of the mold cavity portion where the hot water is bad through an on-off valve. I am doing so.

  In the invention described in Patent Document 6 below, the pressure plunger is protruded before the molten metal is filled into the mold cavity. This method prevents the molten metal from entering the clearance between the pressurizing plunger and the mold that are movably fitted with a small clearance so that the pressurizing operation can be performed continuously without disassembly and cleaning. I have to.

Japanese Patent No. 4054051 JP 2008-18461 A JP 2004-122146 A JP 2001-96353 A JP-A-4-33770 JP-A-61-1463

  However, for example, in the vertical casting method disclosed in Patent Document 1, in order to suppress the occurrence of internal defects and maintain the dimensional accuracy of a cast product at a low metal pressure of, for example, about 50 MPa, it is disclosed. It is not possible to easily manufacture a product having a precise and constant size only by the technology that has been used. Specifically, unless the pressurization part becomes a product or becomes a product, but the accuracy of the dimensions of the same part is not required, especially the pressurization part itself is a product and requires dimensions. When there are irregularities, high dimensional accuracy is required. However, as the mold temperature rises during continuous operation, the weight of the casting material and the dimensions of the mold may change, making it difficult to obtain a product with a predetermined thickness and a predetermined weight with high accuracy for a certain period of time. . This problem cannot be solved by other Patent Documents 2-6.

  That is, in the pressure casting method disclosed in Patent Document 2, the molten metal held in the sleeve is filled into the mold cavity at a high speed, so that the molten metal spouts out of the mold and the quality deteriorates. However, this pressure casting method cannot solve the above problem.

  Further, in the pressure casting method disclosed in Patent Document 3, the pressure is increased in two stages to prevent the hot water from flying from the mold and to obtain a product with high internal quality. Although it is possible to prevent the molten metal from jetting out of the mold and deteriorating the quality, this pressure casting method cannot solve the above problems.

  Further, Patent Document 4 is characterized in that a stable pressurizing operation is continued while a stroke per unit time (movement distance) is moved so as to fit the master curve by feedback control of the pressurizing force of the pressurizing plunger. However, in this method, the molten metal in the mold cavity filled from the mold gate port is pressurized and solidified at a local site different from the gate port. In such a method of filling the mold cavity constituted by the combined molds with the molten metal and pressurizing the metal in the part that does not become a product from the same injection port, the dimensions of the casting material to be the product are naturally determined accurately. Therefore, it is not possible to cope with the casting method in which the weight and dimensions of the casting to be finally achieved are not determined, and furthermore, it is possible to finally adjust to the target material dimensions while suppressing the shrinkage nest. Can not.

  Further, in Patent Document 5, in order to obtain a casting for gravity casting with good hot water flow and few residual bubbles, a gas vent hole is provided at the tip of a mold cavity portion with poor hot water flow through an on-off valve. However, in this method, since the passage connected to the vent hole and the passage of the on-off valve coincide with each other, after the air and molten aluminum at the molten metal flow out of the mold, the on-off valve is operated to enter the mold cavity. The optimal operation timing when the molten aluminum is completely filled cannot be confirmed. Further, even a shut-off pin that discharges a general gas basically has the same mechanism by discharging the air through a pin hole by retracting the pin during exhaust. Further, although no patent document is described, for example, when high pressure is not applied as in low pressure casting, it is possible to use it continuously in repeated casting once the coating agent is used. When pressure molding is performed at a high pressure as described above, it is necessary to spray, for example, a graphite-based release agent before casting every time. Under this condition, in the venting vent installed in the mold for venting air, the release agent accumulates on the air vent, and stable air exhaust cannot be performed, thereby ensuring stable casting. was difficult.

  Further, in Patent Document 6 below, the pressurizing plunger is protruded before the molten metal is filled into the mold cavity, so that the pressurizing plunger and the mold that are movably fitted with a small clearance can be used. The molten metal is prevented from entering the clearance, and the pressure operation can be continuously performed without disassembly and cleaning. However, since this method is not for reducing the air in the mold cavity remaining when the molten metal flows in, the amount of the molten metal filled in the mold cavity cannot be stabilized.

  The present invention has been made in view of such problems. After filling the mold cavity with the molten metal, the molten metal inlet is closed, and the molten metal in the mold cavity is removed by the pressurizing means attached to the mold. An object of the present invention is to provide a pressure casting method that suppresses the generation of internal defects and maintains the dimensional accuracy of a cast product by applying pressure stepwise.

  The pressure casting method according to the present invention includes a step of advancing the insert mold into a mold cavity formed by a fixed mold, a movable mold, and a insert mold for pressurizing a molten metal, and a molten metal flow in the cavity. Filling the molten metal through the inlet; pulling the nested mold back by a predetermined distance in the direction of increasing the capacity of the mold cavity during the process of filling the mold cavity with the molten metal; and the mold After the molten metal is filled in the cavity, the process of closing the molten metal inlet and the process of advancing the insert mold and pressurizing the molten metal filled in the mold cavity are repeated. A predetermined distance for pulling back the nested mold is adjusted so that a pressurizing portion by the nested mold is within a predetermined size range.

  In a pressure casting method according to a preferred embodiment of the present invention, when casting a cast product using a vertical mold casting machine, the mold cavity is filled with molten metal through a casting stalk from a removable pressure pan. After that, in the pressure casting method of the casting product in which the molten metal inflow path is closed and the molten metal in the mold cavity is pressurized by the pressurizing means attached to the mold, the molten metal inflow in the process of filling the molten metal into the mold cavity The hydraulically driven center nesting mold, which is located at the top of the part and can move up and down and can pressurize the molten metal filled in the mold cavity, is lowered to the molten metal inflow side, and at the latest, before the completion of filling In the process of pressurizing the molten metal filled in the mold cavity, the initial position of the hydraulically driven center nested mold loaded on the molten metal inflow site is used as a reference. By setting the final target displacement in advance and changing the applied pressure before the final target displacement, or by setting multiple times from the start of pressurization, the final target displacement can be added step by step according to the increasing displacement. It is characterized by increasing the pressure. Here, lowering the nesting mold to the molten metal inflow side is performed in order to reduce the volume of the mold cavity and suppress residual air, but the molten metal filled from the stalk causes turbulent flow. This means that the air moves in a range that does not cause a gas defect and does not increase the inflow resistance. In addition, it is said that it will rise before filling is completed, in anticipation of the volume that shrinks when the molten metal solidifies and becomes a solid, and the mold is moved up to the position where the volume of the molten metal is increased to raise the mold This means increasing the volume of the cavity. Further, the volume of the molten metal varies depending on the density based on the molten metal temperature, but approximately 10% of the solid volume is a measure of the shrinkage.

  In the present embodiment, by being configured as described above, the mold cavity is filled with a constant weight of metal that does not interfere with the product dimensions, for example, ± 1.0%, and then in a multistage manner according to the target dimensions. Since the cast product with high dimensional accuracy is obtained because of the pressurization, the processed product can be surely taken, and a dense cast product in which internal defects are suppressed can be obtained.

  Further, in this embodiment, during continuous production, the difference between the measured moving distance and the standard moving distance of the center nested mold is detected so that the filling amount of the mold cavity during filling is constant, and before filling is completed. It is possible to adopt a configuration that adjusts the position of the center nesting die at the center. According to this structure, the molten metal weight which fluctuates according to external factors during continuous operation, such as hot water temperature and mold temperature, can be made constant, and a cast product having a very stable size can be obtained. Here, the standard moving distance is in contact with the center nesting die after casting from the position of the center nesting die before pressurization in which a shaped material having a target dimension obtained in advance at the beginning of continuous casting is obtained. It means the distance to the upper end of the cast product, and the actually measured moving distance means the actual moving distance deviated from the standard moving distance during continuous operation. By evaluating the difference between the two moving distances for each shot or in units of more shots and updating the position of the center nest before pressurization, the casting can always be maintained at the standard size.

  In another embodiment of the present invention, when filling the mold cavity with the molten metal, air and hot water in the mold cavity are passed through a passage sandwiched between the upper mold and the horizontal mold adjacent to the tip of the mold cavity. After discharging the tip metal, the hydraulically driven shut-off pin moves in the passage so that the metal pressed by the hydraulically driven center nesting die does not blow out from the die cavity. The structure which presses the metal can be adopted. According to this configuration, the metal in the cavity is completely filled after the air and hot metal in the mold cavity are discharged, so that the mold cavity filling amount becomes more constant.

  Further, in another embodiment of the present invention, the movement of the hydraulically driven shut-off pin is caused by the thermoelectric embedded in the mold adjacent to the passage between the upper mold and the horizontal mold adjacent to the tip of the mold cavity. A configuration based on at least one of the temperature detected from the pair and the elapsed time after the start of filling the molten metal can be employed. According to this configuration, the mold cavity filling amount becomes even more constant.

  Further, in another embodiment of the present invention, in addition to the melt inflow site, a configuration in which pressurization is performed in stages using a hydraulically driven partial pressurization pin that can operate independently for a plurality of solidification delay sites. Can be adopted. According to this configuration, each part in the product can be made dense with no defects.

  Further, in another embodiment of the present invention, by adopting a type in which a molten metal is filled into a mold cavity through a cast stalk from a detachable pressure cooker, the pressurizing force gradually increases after filling the molten metal. Can be employed in a range of 20 to 50 MPa. According to this configuration, since the machine cost can be reduced and a material with less shrinkage can be obtained, this is an industrially advantageous molding method.

  Further, in another embodiment of the present invention, a configuration is adopted in which the pressurization diameter of the coagulation delay site to be pressurized using a hydraulically driven center nesting die is larger than the diameter of the product obtained after processing from the same site. it can. According to this structure, the product which does not contain the sheared metal structure and segregation layer which generate | occur | produce in the boundary of the site | part pressurized and the site | part which is not pressurized can be manufactured.

  Moreover, in other embodiment of this invention, it can employ | adopt that the cast product to manufacture is an aluminum wheel. According to this configuration, a dense aluminum wheel with high dimensional accuracy and no casting defects can be obtained.

  According to another embodiment of the present invention, in the spoke portion connected to the out rim flange portion of the aluminum wheel, a partial pressure pin that is hydraulically driven with respect to the surplus portion formed between the plurality of ribs of the spoke portion. It is possible to employ pressurization using According to this configuration, it is possible to obtain an aluminum wheel in which the intersecting portion between the out rim flange portion and the spoke portion where solidification is delayed is made dense. Here, the out rim flange means a rim flange on the clothing surface side of the wheel.

  Further, before the filling step of filling the mold cavity with the molten metal, after filling the mold with the molten metal, the surface of the molten metal remaining in the detachable pressure pan and the detachable pressure pan Removing one or more oxide films on the surface of the molten metal poured using ladle with a special jig has a very good effect on quality improvement.

  In one embodiment of the present invention, in order to obtain a dense and highly accurate product, and to prevent metal from being blown from the mold during casting, a hydraulically driven load applied to the molten metal inflow site is used. By setting the final target displacement in advance with the initial position of the center nesting mold as a reference and setting multiple positions for changing the applied pressure before the final target displacement, or multiple times from the start of pressurization, The initial position of the center nesting mold is adjusted so that the pressing force is increased stepwise according to the displacement, and the mold cavity filling amount at the time of filling is constant during continuous production as necessary. This can be summarized in terms of the solid phase rate of the molten metal. As an example, the solid phase rate of the melt at the center of the solidification delay site in the mold cavity in contact with the hydraulically driven center nesting die. Before reaching 20%, move the pressure plunger to at least 50% to 70% of the final target displacement, keep the final metal pressure during that time within 70% of the pressure at the end of molding, and then step up the pressure By doing so, each part in the product can be made denser and with high dimensional accuracy.

  As described above, according to the present invention, a product with high dimensional accuracy and high density can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a basic configuration diagram showing a vertical clamping caster that performs a pressure casting method according to an embodiment of the present invention and its peripheral structure. It is an enlarged view of a shut-off pin for discharging residual gas in the mold cavity of the casting machine. It is process drawing which shows the movement of the center nest type | mold and gate seal pin from the molten metal filling to the metal mold cavity of the casting machine to pressurization. It is a figure which shows the time-dependent change of the stroke of a center nesting metal mold | die, a metal pressure, and a filling air pressure. It is a position change flowchart of the center nesting mold for making the filling amount of the molten metal into the mold cavity constant during continuous production.

Hereinafter, preferred embodiments of a pressure casting method of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a basic configuration diagram showing a vertical clamping casting machine and its peripheral structure according to an embodiment of the present invention.

  As shown in FIG. 1, the vertical mold casting machine according to the present embodiment has a lower mold 10 fixed to a fixed platen 4, a horizontal mold 11 that opens and closes laterally with respect to the lower mold 10, and a lower mold 10. A mold cavity 12 is formed by an upper mold 9 that opens and closes in the vertical direction. In this embodiment, the cast product is an aluminum wheel, and the mold cavity 12 is formed in an aluminum wheel shape.

  A pressure pan 1 in which an amount of molten aluminum 7 required for one casting is accommodated is detachably mounted on the lower surface of the fixed platen 4. A molten metal injection port 6 communicating with the lower side from the mold cavity 12 is formed in the central portion of the lower mold 10 corresponding to the central portion of the aluminum wheel. A cylindrical stalk 8 that is immersed in the molten aluminum 7 of the pressure pan 4 is provided. A gas pressurization inlet 5 having one end communicating with the inside of the pressurization pan 1 is formed in the stationary platen 4. By supplying the pressurization gas into the pressurization pan 1 through the gas pressurization inlet 5, The mold cavity 12 can be filled with the molten metal 7 through the stalk 8.

  The upper mold 9 is fixed to the movable platen 3 and moves up and down. The upper die 9 is provided with a cylindrical center nesting die 13 that is driven up and down with respect to the upper die 9 at the center thereof. This center insert mold 13 is provided as a pressurizing means for the molten metal filled in the mold cavity 12, and the tip thereof forms the outer diameter surface of the central portion of the aluminum wheel product. A gate seal pin 14 that selectively closes the molten metal inlet 6 is coaxially mounted at the center of the center insert mold 13 so as to be movable forward and backward. Further, the upper die 9 is provided with a partial pressure pin 15 that applies partial pressure to the surplus portion formed between the ribs of the spoke portion connected to the out rim flange portion of the aluminum wheel so as to be movable back and forth. ing. The partial pressure pin 15 is interlocked with the connecting plate 17. Further, as shown in detail in FIG. 2, the upper mold 9 is formed so that the metal pressed by the center insert mold 13 does not blow out from the mold cavity 12 through the air vent passage 18. A shut-off pin 19 that closes the tip of the cavity 12 is mounted so as to freely advance and retract. The shut-off pin 19 is driven in conjunction with the connecting plate 16 at a timing when a temperature change is detected by the thermocouple 20 mounted in the upper mold 9.

  The connecting plates 16 and 17, the gate seal pin 14, and the center insert mold 13 are hydraulically driven by hydraulic cylinders 21 to 24, respectively. The movement stroke and pressure of the center nested mold 13 are detected by the position sensor 25 and the pressure sensor 26, respectively, and those detection signals and the detection signal of the thermocouple 20 are fed back to the control unit 28. The control unit 28 performs drive control of the hydraulic cylinders 21 to 24 based on the set value set by the input unit 29 and the fed back parameter.

Next, a pressure casting method for an aluminum wheel using the vertical clamp casting machine configured as described above will be described.
First, the molten aluminum 7 is poured into the detachable pressure pan 1 using the ladle 2, and the pressure pan 1 is moved up horizontally and docked to the stationary platen 4. After that, air is introduced from the gas pressurizing inlet 5 and the molten metal surface of the molten aluminum 7 held in the pressurizing pan 1 is pushed down, and the upper die 9, the lower die 10, and the horizontal die 11 are formed through the stalk 8. The aluminum wheel mold cavity 12 is filled with molten aluminum 7. During filling, as shown in FIG. 3, the center nested mold 13 is lowered to reduce the volume of air in the mold cavity 12 (a), and before the completion of filling, the center nested mold 13 is raised and the center insert mold is added. The volume of the molten aluminum 7 in the pressure part is secured (b), and simultaneously with completion of filling, the hydraulically driven gate seal pin 14 fitted to the center insert mold 13 is lowered to close the molten metal inlet 6 (c). Thereafter, the pressure is increased step by step while the center insert mold 13 is lowered to the final target displacement point (d). From this, it can be seen from FIG. 4 that the center pressurization stroke rises and falls and the metal pressure gradually rises and the filling air pressure rises. That is, as the air pressure that pushes down the molten metal surface of the pressure pan 1 rises, the molten aluminum 7 enters the mold cavity 12, but before the filling is completed, the center nesting die 13 rises and the filled molten metal. The molten metal inlet 6 is closed by a hydraulically driven gate seal pin 14 immediately after completion of filling. Thereafter, the hydraulically driven center nesting die 13 is lowered (the downward stroke of the center nesting die 13 is increased), and the molten aluminum 7 in the die cavity 12 is pressurized stepwise. Moreover, a shrinkage nest is prevented using the partial pressurization pin 15 with respect to the spoke cross | intersection part which solidification delays. Furthermore, in order to completely fill the mold cavity 12 with the molten aluminum 7 except for the air in the mold cavity 12, as shown in FIG. Then, the shutoff pin 19 is pressed against the aluminum solution 7 that has flowed out, so that the molten aluminum 7 is not blown out from the mold cavity 12 by pressurization.

FIG. 5 shows a position change flowchart of the center nested mold 13 for making the filling amount of the molten aluminum 7 into the mold cavity 12 constant during continuous production. In addition, the optimum retraction (upward) distance of the center nesting die 13 is obtained while observing the difference between the pressure moving distance of the nesting and the actually measured moving distance for obtaining the casting material of the target dimension. Specifically, first, using the input unit 29, the target standard movement distance n and the pullback amount R of the center nesting die 13 corresponding thereto are input to the control unit 28 (S1, S2). During operation (S4), when the pressure sensor 26 detects that the pressure applied by the center nested mold 13 has reached a predetermined pressure, the pressurization is terminated (S5), and the center nested mold 13 is actually used. The distance S moved to is detected by the position sensor 25 (S3, S6). If the absolute value of the difference between the target standard movement distance n and the actual movement distance S of the center nesting mold 13 at the time of filling the molten metal is 1.0 mm or less, the amount of retraction of the center nesting mold 13 (the amount of increase) ) The next casting is performed without changing R (S7). However, if it exceeds 1.0 mm, it is necessary to change the pull back amount (rise amount) R of the center nesting die 13 (S8, S9). In that case, when the actual moving distance S is larger than the target standard moving distance n (S8), it is necessary to increase the amount of the molten aluminum 7, and the control unit 28 sets the center nested mold set initially. The value of the pullback amount (rise amount) R of 13 is reset by 1 mm (S10). Conversely, when it is small (S9), the control unit 28 resets the value of R by 1 mm (S11).
In the above example, the subsequent pullback amount R is determined based on the difference between the actual moving distance S of the center nested mold 13 and the target moving distance n. However, the movement of the center nested mold 13 is determined. Based on the difference between the later position and the target position, the subsequent pullback amount R may be determined.

  Table 1 shows the influence of the position control of the hydraulically driven center nesting mold during filling of the molten metal and the method of pressurizing the molten metal inflow site after filling the molten metal on the quality of the cast product. Quality refers to the appearance of the cast product, the weight accuracy of the cast material, the material dimensions directly under the pressure plunger, and the nest inside the product. The cast product is an aluminum wheel.

  In Example 1, the position control of the hydraulically driven center nesting mold at the time of filling the molten metal is performed, and the molten metal in the mold cavity at the molten metal inflow portion after the filling is stepwise pressurized, so that no metal is blown out. The appearance, weight accuracy, material dimensions just below the pressure plunger, and soundness inside the product are good. Here, the position control of the hydraulic drive center nesting mold at the time of molten metal filling is one that lowers the center pressurizing nesting at the time of filling and raises it before the completion of filling to reduce the amount of air remaining in the mold cavity. On the other hand, if the filling amount increases or decreases due to changes in the mold temperature during continuous casting, the value is fed back by checking the difference between the actual travel distance of the center insert and the standard travel distance. It means a system that always controls the weight and dimensions to be optimal after pressure solidification. Incremental pressurization of the melt in the mold cavity at the melt inflow site starts with pressurization using a center nested mold in order to effectively remove the shrinkage nest while aiming at the final product size that is targeted in advance. The applied pressure was suppressed to about 20 MPa for 2 seconds, and then the pressure was increased stepwise to reach 36 MPa. The metal pressure is preferably 20 MPa or more, more preferably 30 MPa or more for preventing shrinkage from the viewpoint of pressurization transmission time and pressurization distance. The mold closing force and the metal pressure for casting are increased, and the machine cost is increased. Therefore, it is preferable to perform molding at a pressure of less than 50 MPa in combination with local pressurization to a portion where solidification is delayed.

  Further, in Example 2, when the cavity air was not positively discharged using the shut-off pin, although slightly inferior to Example 1 of the present invention, although a slight lack of hot water was confirmed, A very small number of contractions were observed.

  In addition, when the pressurization diameter of the coagulation delay part to be pressurized using a hydraulically driven center insert mold is smaller than the diameter of the product obtained after processing from the same part, the pressurization part and the pressurization part Since a sheared metal structure and segregation layer were observed at the boundary of the parts that were not formed, and this became a problem in terms of product strength, in the examples shown in Table 1, molding was performed with a diameter larger than the product diameter. This caused no problems.

  As described above, in the pressure casting method according to the present embodiment, in the step of filling the mold cavity 12 with the molten aluminum 7, as shown in FIG. The hydraulically driven center nested mold 13 that can move and pressurize the molten aluminum 7 filled in the mold cavity 12 is lowered to the molten metal inflow side, raised at the latest before the completion of filling, and during continuous production. As shown in FIG. 5, the center nesting die before filling is completed by detecting the difference between the measured moving distance and the standard moving distance of the center nesting die 13 so that the filling amount of the mold cavity at the time of filling becomes constant. The position of the mold 13 is adjusted. Further, in the step of pressurizing the molten aluminum 7 filled in the mold cavity 12, as shown in FIG. 4, the initial position at the start of the operation of the hot water pressure driven center nested mold 13 loaded on the molten metal inflow portion. The final target displacement is determined in advance, and the position for changing the applied pressure before the final target displacement or multiple times from the start of pressurization are set step by step according to the increasing displacement. As shown in FIG. 1 and FIG. 2, the pressurizing force is increased, and when filling the mold cavity 12 with the molten aluminum 7, it is sandwiched between the upper mold 9 and the horizontal mold 12 adjacent to the tip of the mold cavity. After discharging the air in the mold cavity 12 and the aluminum solution 7 of the molten metal via the air vent passage 18, the center nesting mold 13 and the partial pressurizing pin 15 thereafter are discharged. As molten aluminum 7 whose pressure more pressurized is not blown out from the mold cavity 12, to press the molten aluminum 7 in the air vent passage 18 to move the shut-off pin 19 inherent in the upper mold 9 is. Thereby, it becomes possible to obtain a highly dense product having excellent dimensional accuracy and few shrinkage foci.

1 pressure pan, 2 ladle, 3 movable platen, 4 fixed plate, 5 gas pressure inlet, 6 molten metal inlet, 7 aluminum molten metal, 8 stalk, 9 upper mold, 10 lower mold, 11 horizontal mold, 12 mold cavity, 13 Center insert mold, 14 Gate seal pin, 15 Partial pressure pin, 16, 17 Connecting plate, 18 Air vent passage, 19 Shut-off pin, 20 Thermocouple

Claims (9)

Advancing the nested mold into a mold cavity formed by a stationary mold, a movable mold and a nested mold for melt pressurization;
Filling the melt into the cavity via a melt inlet;
Pulling back the nested mold by a predetermined distance in the direction of increasing the capacity of the mold cavity during the process of filling the mold cavity with molten metal;
After the molten metal is filled in the mold cavity, the step of closing the molten metal inlet,
Repeating the step of advancing the nested mold and pressurizing the molten metal filled in the mold cavity,
A pressure casting method, wherein a predetermined distance for pulling back the nested mold is adjusted so that a pressurizing portion of the base material by the nested mold is within a predetermined size range.   Adjusting a predetermined distance for pulling back the nesting die at the time of subsequent casting based on a difference between a moving distance of the nesting die from the start of pressurization of the molten metal to the end of pressurization and a target moving distance. The pressure casting method according to claim 1.   2. The predetermined distance for pulling back the nested mold at the subsequent casting is adjusted based on an error between a position of the nested mold at the end of pressurization of the molten metal and a target position. Pressure casting method. The nesting mold is a center nesting mold that is positioned above the molten metal inlet and moves up and down by hydraulic drive,
In the step of filling the mold cavity with the molten metal,
Filling the mold cavity with molten metal from the detachable pressure pan through casting stalk, and raising the center nested mold to a position where the shape material of the target dimension can be obtained before completion of filling,
In the process of pressurizing the molten metal filled in the mold cavity,
4. The pressurizing force is increased stepwise according to the displacement of the center nesting die in the pressurizing direction or by setting a plurality of times from the start of pressurization. The pressure casting method according to item.   The movable mold is composed of an upper mold and a horizontal mold, and when filling the mold cavity with molten metal, the mold cavity air and the mold cavity air and a passage sandwiched between the upper mold and the horizontal mold adjacent to the tip of the mold cavity. After discharging the hot metal, move the hydraulically driven shut-off pin in the upper mold and press the metal in the passage so that the metal pressurized from the center insert mold does not blow out from the mold cavity. The pressure casting method according to claim 4, wherein the passage is closed.   The temperature detected by the thermocouple embedded in the mold adjacent to the passage sandwiched between the upper mold and the horizontal mold adjacent to the tip of the mold cavity, and the elapsed time after filling the melt. 6. The pressure casting method according to claim 5, wherein the pressure casting method is based on at least one of the signals.   7. The method according to claim 4, wherein a plurality of coagulation delay sites other than the pressurization site by the center nesting mold are pressurized stepwise by a hydraulically driven partial pressurizing pin that can be operated independently. The pressure casting method according to claim 1.   The pressure casting method according to any one of claims 4 to 7, wherein the pressurizing force gradually increasing after the molten metal filling is in a range of 20 to 50 MPa.   The pressurization diameter of the coagulation delay part pressurized using a hydraulic drive center insert mold is larger than the diameter of the product obtained after processing from the same part. Pressure casting method.

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