Device and method for predicting occurrence position of shrinkage cavity in casting

Abstract

The present invention addresses the problem of providing a device and a method for predicting the position of occurrence of a shrinkage cavity in a casting, which are capable of increasing options for countermeasures against the shrinkage cavity in a casting. The present invention is a device for predicting the occurrence position of a shrinkage cavity in a casting cast by injecting molten metal into a mold, the device comprising: a measurement point setting unit for setting a plurality of measurement points for the casting; a molten metal replenishment limit solid fraction arrival time calculation unit that calculates a molten metal replenishment limit solid fraction arrival time for each measurement point; a solidification path setting unit that sets a solidification path of the casting by connecting measurement points selected on the basis of the molten metal replenishment limit solid fraction arrival time; a surface distance calculation unit that calculates, for each measurement point located on the solidification path, the distance from the measurement point to the surface of the casting closest to the measurement point; and a molten metal replenishment blocking site determination unit that determines a molten metal replenishment blocking site at which the replenishment of the molten metal is blocked during the solidification of the molten metal.

Description

Technical Field

[0001] This invention relates to a device and method for predicting the location of shrinkage cavities in castings. Background Technology

[0002] Patent Document 1 discloses a method for predicting the location of shrinkage cavities in a casting manufactured by injecting molten metal into a mold. In this method, for each internal point in the casting, the radius value of a virtual inscribed sphere is obtained, and then the range of internal points with a radius value greater than a reference radius value is obtained, thereby determining the location where shrinkage cavities are likely to occur.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2021-53662 Summary of the Invention

[0004] As a countermeasure for areas prone to shrinkage cavities, thinning the wall thickness can be considered. However, depending on the performance requirements of the casting, cases where thinning the wall thickness is not feasible may also be considered. Therefore, various options are needed to address areas prone to shrinkage cavities.

[0005] The present invention aims to solve this problem by providing a device and method for predicting the location of shrinkage cavities in castings, which can increase the options for countermeasures against shrinkage cavities in castings.

[0006] This invention relates to an apparatus for predicting the location of shrinkage cavities in a casting produced by injecting molten metal into a mold. The apparatus includes: a measurement point setting unit that sets multiple measurement points for the casting; a molten metal replenishment limit solids fraction arrival time calculation unit that calculates, for each measurement point, the time until the molten metal cannot flow, i.e., the molten metal replenishment limit solids fraction arrival time; a solidification path setting unit that connects the measurement points selected based on the molten metal replenishment limit solids fraction arrival time to set a solidification path for the casting; a surface distance calculation unit that calculates, for each measurement point located on the solidification path, the distance from the measurement point to the nearest surface of the casting; and a molten metal replenishment blockage location determination unit that determines a molten metal replenishment blockage location that blocks molten metal replenishment during the solidification of the molten metal, based on the distance to the surface of the casting.

[0007] This structure increases the options for countermeasures against shrinkage cavities in castings.

[0008] This invention relates to a method for predicting the location of shrinkage cavities in a casting produced by injecting molten metal into a mold. The method includes: setting multiple measurement points on the casting; calculating, for each measurement point, the time until the solid fraction at which the molten metal cannot flow is reached, i.e., the time to reach the molten metal replenishment limit solid fraction; connecting the measurement points selected based on the molten metal replenishment limit solid fraction arrival time to set a solidification path for the casting; calculating, for each measurement point on the solidification path, the distance from the measurement point to the nearest surface of the casting; and determining, based on the distance to the surface of the casting, a molten metal replenishment blocking point that blocks molten metal replenishment during the solidification of the molten metal.

[0009] This structure increases the options for countermeasures against shrinkage cavities in castings.

[0010] Invention Effects

[0011] This invention provides a device and method for predicting the location of shrinkage cavities in castings, which can increase the options for countermeasures against shrinkage cavities in castings. Attached Figure Description

[0012] Figure 1 It is a three-dimensional sectional view of the cylinder head that predicts the location of shrinkage cavities.

[0013] Figure 2 From Figure 1 A partial cross-sectional view of the cylinder head shown in direction II.

[0014] Figure 3 This is a block diagram illustrating the device for predicting the location of shrinkage cavities according to the embodiment.

[0015] Figure 4 These are explanatory diagrams of the method for predicting the location of shrinkage cavities according to the embodiments. Figure (a) shows the state in which molten metal is being filled into the cavity. Figure (b) shows the state in which the molten metal has finished filling the cavity. Figure (c) shows the state in which the molten metal begins to solidify. Figure (d) shows the state in which the molten metal supply is blocked as the molten metal solidifies.

[0016] Figure 5 This is a flowchart illustrating an example of a method for predicting the location of shrinkage cavities according to an embodiment.

[0017] Figure 6 It means Figure 1 The diagram shows an example of the time to reach the molten metal replenishment limit solid fraction and the solidification path of a cylinder head.

[0018] Figure 7It is a graph showing the relationship between the arrival time of the molten metal replenishment limit solid fraction at each measurement point on the solidification path and the surface distance. Detailed Implementation

[0019] The following uses Figures 1 to 7 The embodiments of the present invention will be described. Figure 1 It is a three-dimensional sectional view of the cylinder head that predicts the location of shrinkage cavities. Figure 2 From Figure 1 A partial cross-sectional view of the cylinder head shown in direction II. Figure 3 This is a block diagram illustrating the device for predicting the location of shrinkage cavities according to the embodiment. Figure 4 This is an explanatory diagram of the method for predicting the location of shrinkage cavities according to the implementation method. Figure 4 (a) indicates the state in which molten metal is being filled into the cavity. Figure 4 (b) indicates that the molten metal has finished filling the cavity. Figure 4 (c) indicates the state in which the molten metal begins to solidify. Figure 4 (d) indicates a state in which the supply of molten metal is interrupted as the solidification of molten metal proceeds. Figure 5 This is a flowchart illustrating an example of a method for predicting the location of shrinkage cavities according to an embodiment. Figure 6 This is a diagram illustrating an example of the arrival time of the molten metal supply limit solid fraction in a cylinder head and the solidification path, indicating the predicted location of shrinkage cavities. Figure 7 It is a graph showing the relationship between the arrival time of the molten metal replenishment limit solid fraction at the measurement point located on the solidification path and the surface distance.

[0020] use Figure 1 and Figure 2 The cylinder head 10 for predicting the location of shrinkage cavities will be described. The cylinder head 10 is a cylinder head for an inline 4-cylinder engine with four combustion chambers and is made of aluminum alloy. The cylinder head 10 is a casting produced by injecting molten aluminum into a mold containing neutrons. Furthermore, the casting for predicting the location of shrinkage cavities is not limited to engine cylinder heads; various castings can be used.

[0021] The cylinder head 10 is cast using a low-pressure casting method. Other casting methods include gravity casting, tilt casting, and die casting. For example, aluminum alloys with added magnesium or copper (e.g., ADC1) can be used as the molten aluminum metal. Furthermore, it is not limited to aluminum alloys; magnesium alloys, zinc alloys, copper alloys, etc., can also be used. The mold can be a die, sand mold, etc.

[0022] The gate 15, into which molten aluminum is poured into a cavity formed in the mold, is positioned below the cylinder head 10. Figure 2The gate 15 is indicated by a dashed line. Molten aluminum metal poured from gate 15 flows from the bottom of the cavity formed in the mold upwards (from...). Figure 2 The cylinder head 10 shown is filled from the bottom to the top.

[0023] Next, use Figure 3 The shrinkage cavity occurrence location prediction device 20 of the casting according to the embodiment will be described. The shrinkage cavity occurrence location prediction device 20 of the casting includes an input device 21, a storage device 22, a calculation device 23, and an output device 24.

[0024] The input device 21 consists of a keyboard, mouse, etc., and is used to input information related to the shape or size of the cylinder head 10, information related to the temperature or material of the mold, information related to the temperature or material of the molten aluminum, and information related to the casting conditions.

[0025] The storage device 22 is composed of random access memory (RAM), read-only memory (ROM), etc., and stores information input from the input device 21, calculation programs related to the method for predicting the location of shrinkage cavities in castings, etc.

[0026] The arithmetic unit 23 consists of a central processing unit (CPU) and other components, and executes a computational program stored in the storage device 22 related to the method for predicting the location of shrinkage cavities in the casting.

[0027] The output device 24 is composed of a display or the like, and outputs the result of the calculation program executed by the arithmetic device 23.

[0028] Next, use Figure 4 The idea behind the method for predicting the location of shrinkage cavities in castings involved in the implementation method is explained. Figure 4 The mold cavity 30 shown is elongated and plate-shaped, with a narrow recess 31 in the width direction formed at the center of its length. Molten metal, composed of dissolved aluminum alloy, is poured into the cavity 30 using a low-pressure casting method. The gate 35, into which the molten metal is poured into the cavity 30, is located at the bottom of the cavity 30.

[0029] First, such as Figure 4 As shown in (a), molten metal 33 is injected from gate 35 into cavity 30 at a specified pressure, and molten metal 33 fills the lower part of cavity 30.

[0030] Next, as Figure 4 As shown in (b), the molten metal 33 reaches the cavity 30 portion furthest from the gate 35, thereby completing the filling of the cavity 30 with the molten metal 33.

[0031] Next, as Figure 4 As shown in (c), solidification 34 of the molten metal begins. Solidification 34 of the molten metal begins from the portion of the molten metal away from the gate 35 and from the outer periphery of the cavity 30. If the molten metal solidifies 34, the aluminum metal shrinks. Space is created in the cavity 30 due to the shrinkage of the aluminum alloy, but since molten metal 33 is replenished from the gate 35, no space is created that could cause shrinkage cavities.

[0032] Next, as Figure 4 As shown in (d), if the solidification 34 of the molten metal proceeds, a portion of the recess 31 will solidify entirely in the width direction. On the other hand, unsolidified molten metal 33 remains in the cavity 32, which is further away from the gate 35 than the recess 31. The molten metal 33 remaining in the cavity 32 is not connected to the gate 35, so no replenishment of molten metal 33 is made. Therefore, shrinkage cavities are generated in the area of ​​the cavity 32 where molten metal 33 remains.

[0033] Thus, if there is a portion that cuts off the connection between the molten metal 33 and the gate 35 before the molten metal solidifies (e.g., Figure 4 As shown in the depression 31, shrinkage cavity occurs. That is, if the location where the connection between the molten metal and the gate is cut off and the molten metal supply is cut off (hereinafter referred to as the molten metal supply blocking location) is determined, the location where shrinkage cavity occurs can be predicted.

[0034] Next, use Figures 5-7 The method for predicting the location of shrinkage cavities in castings using the shrinkage cavity occurrence location prediction device 20 is explained. Figure 5 This is a flowchart illustrating an example of a shrinkage cavity occurrence location prediction method performed by a shrinkage cavity occurrence location prediction device 20 in a casting.

[0035] In step S1, information such as the shape or size of the cylinder head 10, which predicts the location of the shrinkage hole, is obtained from the storage device 22. The acquisition of information about the cylinder head 10 is performed by the information acquisition unit of the computing device 23.

[0036] In step S2, multiple measurement points P are set in the cylinder head 10. The setting of measurement points P is performed by the measurement point setting unit of the calculation device 23. For example... Figure 6 As shown, measurement points P divide the 3D model of the cylinder head 10 into three dimensions at specified intervals, and are set at the center of each of the approximately cubic spaces obtained from the division. Furthermore, in Figure 6 The image shows only a portion of the measurement point P. The spacing can be set arbitrarily. Furthermore, the resulting space can be set to various shapes, rather than a cube.

[0037] In step S3, for each measurement point P, the time until the solid fraction of molten aluminum cannot flow is calculated, i.e., the time T for reaching the molten metal replenishment limit solid fraction. The calculation of the molten metal replenishment limit solid fraction reaching time T is performed by the molten metal replenishment limit solid fraction reaching time calculation unit of the calculation device 23. The molten metal replenishment limit solid fraction reaching time T is calculated based on the temperature of the molten aluminum injected into the mold, the temperature of the mold, the distance from the gate 15, etc. The solid fraction at which the molten aluminum cannot flow is, for example, 0.6 to 0.7. Figure 6 As shown, the time T to reach the limit solid fraction of molten metal replenishment decreases as the distance from the gate 15 increases. That is, as the distance from the gate 15 increases, the solidification rate of the molten aluminum metal increases, and the time to reach the solid fraction at which the molten aluminum metal can no longer flow decreases.

[0038] In step S4, the solidification path R of the cylinder head 10 is set by connecting the measurement point P selected based on the time T for the molten metal replenishment limit solid fraction to reach. The setting of the solidification path R of the cylinder head 10 is performed by the solidification path setting unit of the calculation device 23. Figure 6 As shown, the solidification path R of the cylinder head 10 is a path connecting the measurement point P (starting point) where the molten metal replenishment limit solid fraction reaches the shortest time T and the measurement point P (end point) closest to the gate 15. It is a path that represents the sequence of solidification of aluminum molten metal by line.

[0039] The solidification path R of the cylinder head 10 is selected and the measurement point P is set according to the following rules. First, as... Figure 6 As shown, the measurement point P with the shortest time T to reach the molten metal replenishment limit solid fraction calculated in step S3 is set as the starting point. Figure 6 In this study, the arrival time T of the molten metal replenishment limit solid fraction calculated for each measurement point P is divided into 7 groups according to the length of time. Therefore, in Figure 6 In the process, there are multiple measurement points P where the time T for reaching the molten metal replenishment limit solid fraction is the shortest. However, in reality, the time T for reaching the molten metal replenishment limit solid fraction varies depending on each measurement point P. Therefore, the measurement point P with the shortest time T for reaching the molten metal replenishment limit solid fraction is set as the starting point.

[0040] Next, among the measurement points P adjacent to the starting point, if there exists a measurement point P where the time T for reaching the molten metal replenishment limit solid fraction is longer than that of the starting point, then that measurement point P is selected. Furthermore, the comparison of the lengths of the time T for reaching the molten metal replenishment limit solid fraction is... Figure 6 The test is conducted among the seven groups shown. If there are multiple measurement points P where the time T for reaching the molten metal replenishment limit solid fraction varies, then the point directly below ( Figure 6The measurement point P is located in the positive Z-axis direction. If there is no measurement point P where the time T for reaching the molten metal replenishment limit solids fraction is longer, then the measurement point P directly below or near the gate 15 is selected. Based on this rule, measurement points P are selected until the measurement point P (end point) closest to the gate 15 is selected. If the measurement point P is selected until the end point, the solidification path R of the cylinder head 10 can be set by connecting the start point and the end point with the selected measurement point P. In addition, the connection method of the measurement points P between the start point and the end point can be changed appropriately.

[0041] In step S5, the distance D from each measuring point P on the solidification path R to the nearest surface of the cylinder head 10 is calculated. In other words, in step S5, the distance D from each measuring point P on the solidification path R to the nearest surface of the mold (including the neutron) is calculated. The calculation of the distance D from each measuring point P on the solidification path R to the nearest surface of the cylinder head 10 is performed by the surface distance calculation unit of the calculation device 23. The shorter the distance D to the surface of the cylinder head 10, the shorter the distance to the mold, and therefore the molten aluminum solidifies rapidly.

[0042] In step S6, for each measurement point P located on the solidification path R, a graph showing the relationship between the time T for reaching the molten metal replenishment limit solid fraction and the distance D to the cylinder head surface is created. The creation of this graph is performed by the graph creation unit of the computing device 23. Figure 7 As shown, for each measurement point P located on the solidification path R, a graph is created representing the relationship between the time T to reach the molten metal replenishment limit solid fraction and the distance D to the cylinder head surface.

[0043] In step S7, based on the time T for reaching the molten metal replenishment limit solid fraction and the distance D to the cylinder head surface, a molten metal replenishment blocking point P1 is determined to block the replenishment of aluminum molten metal during the solidification period. The determination of the molten metal replenishment blocking point P1 is performed by the molten metal replenishment blocking point determination unit of the computing device 23. Specifically, based on the graph created in step S6, a measurement point P where the distance D to the cylinder head surface is close to the time T for reaching the molten metal replenishment limit solid fraction is designated as the molten metal replenishment blocking point P1. Figure 7 (The circled area). The point at which the molten metal supply is blocked (P1) can be set according to factors such as the time T for reaching the molten metal supply limit solid fraction, the temperature of the molten aluminum, the mold temperature, and casting conditions. Alternatively, the measuring point P where the distance D to the cylinder head surface is less than a specified threshold can be set as the molten metal supply blocking point (P1).

[0044] Figure 2The diagram shows the molten metal supply interruption point P1 determined by the shrinkage cavity occurrence location prediction device 20. Shrinkage cavities are predicted to occur in the cylinder head 11 on the side further away from the gate 15 than the molten metal supply interruption point P1. As a countermeasure to suppress shrinkage cavity formation, it is possible to thicken the area around the molten metal supply interruption point P1, thereby increasing the distance between the molten metal supply interruption point P1 and the surface of the cylinder head 10. By thickening the area around the molten metal supply interruption point P1, the connection between the molten aluminum and the gate 15 is not severed in the cylinder head 11 on the side further away from the gate 15 than the molten metal supply interruption point P1, thus maintaining the supply of molten aluminum from the gate 15.

[0045] As a countermeasure to suppress the formation of other shrinkage cavities, thinning of the cylinder head 11 on the side farther from the gate 15 than the molten metal supply blocking point P1 can be considered. By thinning the wall, the molten aluminum can be solidified before the molten aluminum is cut off from the gate 15 at the molten metal supply blocking point P1.

[0046] In this invention, a solidification path for the casting is defined, and the molten metal supply blockage point is determined based on the distance from each measurement point along the solidification path to the nearest surface of the casting. By determining the molten metal supply blockage point, the location of shrinkage cavities can be predicted. Furthermore, as a shrinkage cavity countermeasure, not only is the wall thickness of the shrinkage cavity area reduced, but the formation of shrinkage cavities can also be suppressed by thickening the molten metal supply blockage point. In other words, the options for shrinkage cavity countermeasures for castings can be increased.

[0047] Furthermore, the present invention is not limited to the above-described embodiments and can be appropriately modified without departing from the spirit of the invention.

[0048] Symbol Explanation

[0049] 10-Cylinder head, 15-Gate, 20-Shrinkage cavity location prediction device, P1-Molten metal supply interruption point.

Claims

1. A device for predicting the location of shrinkage cavities in castings, characterized in that it predicts the location of shrinkage cavities in castings produced by injecting molten metal into a mold. include: The measurement point setting unit sets multiple measurement points for the casting. The molten metal replenishment limit solid fraction reaching time calculation unit calculates the time until the molten metal can no longer flow solid fraction at each measurement point, which is the molten metal replenishment limit solid fraction reaching time. A solidification path setting unit is connected to the measurement point selected based on the arrival time of the molten metal supply limit solid fraction to set the solidification path of the casting. The surface distance calculation unit calculates the distance from each measurement point located on the solidification path to the nearest surface of the casting. and The molten metal supply interruption location determination unit determines the molten metal supply interruption location that blocks the molten metal supply during the solidification of the molten metal based on the distance to the surface of the casting.

2. A method for predicting the location of shrinkage cavities in castings, characterized in that, include: The process of setting multiple measurement points for the casting; For each measurement point, the process of calculating the time until the solid fraction of molten metal can no longer flow, i.e., the time when the molten metal replenishment limit solid fraction is reached; The process of setting the solidification path of the casting based on the measurement point selected based on the arrival time of the molten metal replenishment limit solid fraction; The process of calculating the distance from each measurement point along the solidification path to the nearest surface of the casting; and The process of determining the molten metal supply interruption point that blocks the molten metal supply during the solidification of molten metal based on the distance to the surface of the casting.

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