JP2018149576A - Casting solidification analysis method, casting solidification analysis device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting solidification method, even in the case of a cast with a special shape, capable of predicting the generation of a shrinkage cavity defect at high precision.SOLUTION: There is provided a casting solidification method, upon the performance of the solidification analysis of a cast, each treatment of a set step where an atmospheric pressure application part of applying atmospheric pressure to the part of a free fluidization area as a viscosity flow state is set and an analysis execution step where the atmospheric pressure applied to the part of the free fluidization area by the atmospheric pressure application part is used as one of analysis parameters, the generation of a shrinkage cavity defect is predicted is executed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a casting solidification analysis method, a casting solidification analysis apparatus, and a program.

  When casting a die-cast product or cast steel product, for most metals, shrinkage occurs during solidification. For this reason, a cavity defect (casting defect) accompanying solidification shrinkage called a shrinkage defect is generated in the cast product. In order to manufacture a high-quality cast product, it is required to apply a casting simulation (computer simulation) to the casting process and to predict the occurrence of shrinkage defect in the casting simulation.

  As techniques for predicting the occurrence of shrinkage defects, there are techniques described in Patent Document 1 and Non-Patent Document 1. Patent Document 1 states that “the amount of shrinkage when the molten metal of the cast metal condenses is defined as the amount of contraction, the amount of contraction is set for each of the elements of the model composed of a plurality of elements, and this amount of contraction is determined according to the solid phase ratio. Distribute to neighboring cells ”. Non-Patent Document 1 describes that “the molten metal is replenished from the direction of gravity and the direction of the maximum solid phase ratio gradient of adjacent elements”.

JP 2005-329465 A

Nagasaka, Y. and two others, “Quantitative prediction of shrinkage cavity by 3D solidification analysis”, Foundry, Japan Foundry Engineering Society, 1989, Vol. 61, No. 2, p. 98-103

  In the prior art described in Patent Document 1 and Non-Patent Document 1, atmospheric pressure is not taken into account in predicting the occurrence of shrinkage defect, so in the case of a specially shaped casting, there is actually no shrinkage defect. Even if it exists, there existed a subject that generation | occurrence | production of a shrinkage defect would be estimated. Examples of the specially shaped casting include, for example, a casting (for example, a side riser) provided with a feeder at a position lower than the uppermost portion of the casting body.

  Accordingly, an object of the present invention is to provide a casting solidification analysis method, a casting solidification analysis device, and a program capable of accurately predicting the occurrence of shrinkage defect even if the casting has a special shape.

In order to solve the above problems, for example, the configuration described in the claims is adopted.
The present application includes a plurality of means for solving the above problems.
When performing a solidification analysis of a cast product, a setting step for setting an atmospheric pressure load section that applies atmospheric pressure to a portion of a free flow region that is in a viscous flow state;
An analysis execution step of predicting the occurrence of shrinkage defect using the atmospheric pressure applied to the free flow region by the atmospheric pressure load as one of the analysis parameters;
Each of the processes is executed.

  According to the present invention, since atmospheric pressure is taken into account for predicting the occurrence of shrinkage defect, the occurrence of shrinkage defect can be accurately predicted even with a specially shaped casting.

It is an example of the block diagram which shows the structure of the casting solidification analysis apparatus which concerns on one Embodiment of this invention. It is an example of sectional drawing explaining the derivation | leading-out procedure of the supply path | route of the molten metal at the time of injecting molten metal into a casting_mold | template. It is an example of the flowchart which shows the flow of a process of the casting solidification analysis method which concerns on one Embodiment of this invention. It is an example of the flowchart which shows the flow of the process for calculation data preparation. It is an example of the flowchart which shows the flow of the process for calculating a temperature change. It is an example of the flowchart which shows the flow of the process for calculating a shrinkage nest. It is an example of the flowchart which shows the flow of a process of shrinkage nest calculation A. It is an example of the flowchart which shows the flow of the process for the molten metal replenishment calculation from an atmospheric pressure load part. It is an example of the flowchart which shows the flow of the process for the molten metal replenishment calculation from a maximum temperature part. It is an example of the flowchart which shows the flow of a process of shrinkage nest calculation B. It is an example of the sectional view of the casting which shows typically the idea of the conventional shrinkage nest prediction method. It is an example of a sectional view of a casting which shows typically a way of thinking of a shrinkage cavity prediction method of this embodiment. FIG. 13 is an example of a diagram showing a portion of the free flow region shown in FIG. 12 where the molten metal remains after a certain time as solidification progresses but free flow is impossible. It is an example of the perspective view which shows the whole shape of the casting used by this embodiment. It is an example of the figure which shows the generation | occurrence | production position of the actual shrinkage cavity defect which generate | occur | produced in the casting used by this embodiment. It is an example of the figure which shows distribution of the time which the casting used by this embodiment reaches | attains the set flow limit solid phase rate. It is an example of the figure which shows the shrinkage cavity prediction result by a conventional method about the casting used by this embodiment. It is an example of the figure which shows the shrinkage cavity prediction result by the shrinkage cavity prediction method which concerns on this embodiment about the casting used by this embodiment.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings. The present invention is not limited to the embodiment, and various numerical values in the embodiment are examples. In the following description and each drawing, the same reference numerals are used for the same elements or elements having the same functions, and duplicate descriptions are omitted.

[Casting solidification analyzer]
FIG. 1 is an example of a block diagram showing the configuration of a casting solidification analyzer according to an embodiment of the present invention. As shown in FIG. 1, the casting solidification analysis device 10 according to the present embodiment includes a preprocessor unit 11, a solidification analysis execution unit 12 called a solver, and a post processor unit 13.

  The preprocessor unit 11 performs processing for setting analysis parameters such as a shape model to be analyzed, physical property values to be used, and calculation conditions for solidification analysis. The casting solidification analysis apparatus 10 according to the present embodiment is characterized in that atmospheric pressure is used as one of analysis parameters. That is, the preprocessor unit 11 has a function as a setting unit (setting process) for setting an atmospheric pressure load unit that applies an atmospheric pressure to a free flow region to be described later when performing solidification analysis of a cast product.

  The solidification analysis execution unit 12 performs processing for predicting the flow of molten metal, solidification analysis, and shrinkage defect. In the molten metal flow analysis, heat / flow analysis is performed considering the movement of the three-dimensional free surface. In the solidification analysis, the progress of solidification in the mold is numerically analyzed. The solidification analysis execution unit 12 predicts the occurrence of shrinkage defect, more specifically, the position and size of the shrinkage defect based on the analysis result of the solidification analysis. That is, the solidification analysis execution unit 12 has a function as an analysis execution unit (analysis execution step) for predicting the occurrence of shrinkage defect using the atmospheric pressure applied to the free flow region as one of the analysis parameters.

  The post processor unit 13 visualizes and displays the occurrence position and size of the shrinkage flaw defect predicted to occur by using the prediction result of the solidification analysis execution unit 12 as a diagram. From the display by the post processor unit 13, it is possible to evaluate the state of the shrinkage defect (that is, the position and size of the shrinkage defect occurrence) that is predicted to occur in the casting when actually cast.

  The casting solidification analyzer 10 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory) for storing a program executed by the CPU, and a RAM (Random Access Memory) used as a work area of the CPU. It can comprise by the well-known microcomputer containing these. In this case, FIG. 1 is a functional block diagram of the casting solidification analyzer 10. That is, the preprocessor unit 11, the coagulation analysis execution unit 12, and the postprocessor unit 13 are functional units that are executed by software by the CPU interpreting and executing programs that realize the respective functions.

(Procedure for deriving molten metal supply route)
FIG. 2 is an example of a cross-sectional view illustrating a procedure for deriving a molten metal replenishment route when molten metal is poured into a mold. FIG. 2A shows the initial stage of coagulation, FIG. 2B shows the middle stage of coagulation, and FIG. 2C shows the end stage of coagulation.

  In the mold 21, an atmospheric pressure load unit 22 is set in a two-dimensional or three-dimensional manner by the preprocessor unit 11 in a region that comes into contact with air when the cast metal melt is solidified. The mold 21 and the atmospheric pressure load portion 22 are made of a material having air permeability.

  The casting shown in FIG. 2 is in a state where solidification has proceeded, and is composed of a portion 23 other than the free flow region and a portion 24 of the free flow region. The portion 23 other than the free flow region is a portion whose solid phase ratio is greater than or equal to a value defined as the flow limit solid phase ratio, that is, a portion not in a viscous flow state. The free flow region portion 24 is a portion whose solid phase ratio is 0 to a value defined as a flow limit solid phase ratio, that is, a portion in a viscous flow state. FIG. 2 shows a state in which the shrinkage defect 25 has occurred around the atmospheric pressure load portion 22. The atmospheric pressure load section 22 is, for example, a through hole that applies (adds) atmospheric pressure to the portion 24 of the free flow region.

  The melt replenishment for the solidification shrinkage of the casting portion, that is, the solidification shrinkage of the portion 23 other than the free flow region and the portion 24 of the free flow region is performed from the portion in contact with the atmospheric pressure load portion 22. The amount of molten metal to be supplied is determined according to the solid phase ratio of each part. About the replenishment amount at this time, you may make it add a restriction | limiting according to a solid-phase rate, without being uniform.

  It is assumed that the molten metal replenishment for the shrinkage in the free flow region portion 24, that is, the molten metal replenishment for compensating for the shrinkage is performed from the molten metal portion in contact with the atmospheric pressure load portion 22. Doing so is reasonable from the well-known Triceri experiment result that "atmospheric pressure is balanced with the height of 760 millimeters of mercury". In other words, if atmospheric pressure acts from the atmospheric pressure loading portion 22 to the free flow region portion 24, if the molten metal is an aluminum alloy, the molten metal is approximately 4.1 meters in height due to the difference in density from mercury. This is because it has the ability to push up about 1.5 meters. As a result, the shrinkage defect 25 is generated and grown from around the atmospheric pressure load portion 22.

[Casting analysis method]
Hereinafter, a casting solidification analysis method (a casting solidification analysis method according to an embodiment of the present invention) in the casting solidification analysis apparatus 10 according to the present embodiment having the above-described configuration will be described with reference to FIG. FIG. 3 is an example of a flowchart showing a processing flow of the casting solidification analysis method.

  The processing operation of the casting solidification analysis method according to the present embodiment corresponds to the processing operation of the solidification analysis execution unit 12 of FIG. And when the casting solidification analysis apparatus 10 is comprised with a microcomputer, the processing operation is performed under control by CPU.

  In the flowchart of FIG. 3, the CPU first prepares calculation data (step S11). Here, data set by the preprocessor unit 11 in FIG. 1, that is, analysis parameters such as a shape model to be analyzed, physical property values to be used, and calculation conditions for solidification analysis are used. Details of the processing operation for preparing the calculation data will be described later (see FIG. 4).

  Next, the CPU sets an initial value t = 0 (step S12), then advances the time by a minute time Δt (step S13), and then calculates a temperature change after the minute time Δt (step S13). Step S14). Details of the processing operation for calculating the temperature change will be described later (see FIG. 5). Next, the CPU calculates the shrinkage nest based on the temperature change (step S15). Details of the processing operation for calculating the shrinkage nest will be described later (see FIG. 6).

  Next, the CPU determines whether or not all of the casting has solidified (step S16). If solidification has not been completed (NO in S16), the CPU returns to step S13 and repeats the same processing. If solidification has been completed (YES in S16), the CPU ends the processing operation of the solidification analysis execution unit 12, that is, a series of processing operations for prediction of solidification analysis including molten metal flow analysis and shrinkage defect generation. To do.

(Calculation data preparation processing operation)
Next, the processing operation for preparing calculation data in step S11 in FIG. 3 will be described with reference to FIG. FIG. 4 is an example of a flowchart showing a flow of processing for preparing calculation data.

  The CPU reads data obtained by converting the casting and the mold into elements for analysis from various data prepared by the preprocessor unit 11 in FIG. 1 (step S21), and then reads the direction of gravity (step S22), The atmospheric pressure to be applied to the free flow region portion 24 through the atmospheric pressure loading section 22 is read (step S23), and then the physical property values to be used are read (step S24).

  Next, the CPU reads the flow limit solid phase ratio allowing free flow (step S25), and then reads the boundary condition (step S26). Here, the boundary condition is a thermal resistance value (= value corresponding to the reciprocal of the heat transfer coefficient) at various boundaries such as a casting and a mold. Next, the CPU sets a time step Δt for coagulation analysis from the data read in step S21, step S24 and step S26 (step S27), and ends a series of processing operations for preparing calculation data. The process proceeds to step S13.

(Processing operation for temperature change calculation)
Next, the processing operation for calculating the temperature change in step S14 in FIG. 3 will be described with reference to FIG. FIG. 5 is an example of a flowchart showing a flow of processing for calculating a temperature change.

First, the CPU instructs to search all the elements (i = 1 to i _max , j = 1 to j _max , k = 1 to k _max ) that are elementized for analysis (step S31), and then For each element, a new temperature is calculated using the old temperature before time Δt (step S32). This processing conforms to the analysis method disclosed in Non-Patent Document 1, for example. Although the difference method is adopted here, the present invention is not limited to this, and can be realized even by temperature change calculation by the finite element method.

  The CPU repeatedly executes the loop processing from step S31 to step S33 until the search is completed for all elements. Then, when the loop processing is completed for all elements, the CPU ends a series of processing operations for calculating the temperature change, and proceeds to step S15 in FIG.

(Processing for shrinkage calculation)
Next, the processing operation for calculating the shrinkage nest in step S15 in FIG. 3 will be described with reference to FIG. FIG. 6 is an example of a flowchart showing a flow of processing for calculating the shrinkage nest.

First, the CPU groups the free flowable elements into element groups connected on one or more faces (step S41), and then the elements (i = 1 to i _max , j = 1 to j _max , k = 1 to k _max ) are instructed to search (step S42).

  Next, the CPU checks whether or not the element being searched is a cast element (step S43). If the element is not a cast element (NO in S43), the CPU returns to step S42, and if it is a cast element (S43). YES), it is checked whether or not the temperature is equal to or higher than the solidus temperature (step S44). Then, the CPU returns to step S42 if it is not equal to or higher than the solidus temperature (NO in S44), and if it is equal to or higher than the solidus temperature (YES in S44), the amount of solidification shrinkage during the transition from the old temperature to the new temperature. Is calculated (step S45).

  Next, the CPU checks whether or not it is a free-flowable region (step S46), and if it is a free-flowable region (YES in S46), performs shrinkage calculation A (step S47). Details of the processing operation of the shrinkage nest calculation A will be described later (see FIG. 7). If the CPU is not in the free flowable region (NO in S46), the shrinkage calculation B is performed (step S48). Details of the processing operation of the shrinkage nest calculation B will be described later (see FIG. 10).

  The CPU repeatedly executes the loop processing from step S42 to step S49 until the search is completed for all elements. Then, when the loop processing is completed for all elements, the CPU ends a series of processing operations for calculating the shrinkage nest, and proceeds to step S16 in FIG.

(Processing of shrinkage nest calculation A)
Subsequently, the processing operation of the shrinkage nest calculation A in step S47 of FIG. 6 will be described with reference to FIG. FIG. 7 is an example of a flowchart showing the flow of processing of the shrinkage nest calculation A.

  First, the CPU checks whether or not the free flowable group to which the element to be searched belongs is in contact with the atmospheric pressure load unit 22 (step S51). If it is in contact with the atmospheric pressure load unit 22 (YES in S51), the CPU performs a melt replenishment calculation from the atmospheric pressure load unit 22 (step S52). Details of the processing operation of the melt replenishment calculation from the atmospheric pressure load unit 22 will be described later (see FIG. 8).

  If not in contact with the atmospheric pressure load part 22 (NO in S51), the CPU performs a molten metal replenishment calculation from the highest temperature part (from the high temperature part to the low temperature part) (step S53). The details of the processing operation of the melt replenishment calculation at the highest temperature portion will be described later (see FIG. 9). After the process of step S52 or step S53 is completed, a series of processing operations for shrinkage nest calculation A is terminated, and the process proceeds to step S49 in FIG.

(Processing for calculation of molten metal replenishment from the atmospheric pressure load)
Next, the processing operation for the molten metal replenishment calculation from the atmospheric pressure load unit 22 in step S52 of FIG. 7 will be described with reference to FIG. FIG. 8 is an example of a flowchart showing a processing flow for molten metal replenishment calculation from the atmospheric pressure load unit 22.

  First, the CPU checks whether or not the molten metal element in contact with the atmospheric pressure load unit 22 is emptied by molten metal replenishment (step S61). If the molten metal element in contact with the atmospheric pressure load unit 22 is empty (NO in S61), the CPU changes the element to the atmospheric pressure load unit 22 (step S62), and then contacts the atmospheric pressure load unit 22. A melt replenishment calculation from the melt element is performed (step S63). If the molten metal element in contact with the atmospheric pressure load unit 22 is not emptied due to the molten metal supply (YES in S61), the CPU directly proceeds to step S63. And after completion | finish of the process of step S63, CPU complete | finishes a series of processing operation for the molten metal supply calculation from the atmospheric pressure load part 22, and moves to step S49 of FIG.

(Processing for calculation of molten metal replenishment from the highest temperature part)
Next, the processing operation for the molten metal replenishment calculation from the maximum temperature part in step S53 in FIG. 7 will be described with reference to FIG. FIG. 9 is an example of a flowchart showing a processing flow for molten metal replenishment calculation from the maximum temperature portion.

  First, the CPU checks whether or not the element of the maximum temperature portion is emptied due to the molten metal supply (step S71). If the highest temperature element is empty (NO in S71), the CPU changes the highest temperature part next to the highest temperature part to the highest temperature part (step S72), and then the molten metal from the highest temperature element. Supply calculation is performed (step S73). If the element of the maximum temperature part is not empty (YES in S61), the CPU directly proceeds to step S73. And after completion | finish of the process of step S73, CPU complete | finishes a series of processing operation for the molten metal replenishment calculation from a maximum temperature part, and transfers to step S49 of FIG.

(Processing for shrinkage calculation B)
Subsequently, the processing operation for shrinkage nest calculation B in step S48 of FIG. 6 will be described with reference to FIG. FIG. 10 is an example of a flowchart showing a flow of processing for shrinkage nest calculation B.

The CPU first resets the counter of the number of adjacent elements n _max that can be replenished to 0 (step S81), and then instructs the search for all 26 adjacent elements including diagonal elements (step S82). Next, it is determined whether or not the element is hotter than the element to be searched (step S83).

The CPU returns to step S82 if it is not an element having a higher temperature than the element to be searched (NO in S83), and if it is a high temperature element (YES in S83), the counter for the number of adjacent elements n _max is incremented by one ( n _max = n _max +1) (step S84). The CPU repeatedly executes the loop processing from step S82 to step S85 until all the adjacent elements (26) are completed. Then, when the loop processing is completed for all the adjacent elements, the CPU determines whether or not the number of adjacent elements n _max is 1 or more (n _max > 0) (step S86).

If the number of adjacent elements n _max is not 1 or more (NO in S86), the CPU ends a series of processes for shrinkage calculation B, and if the number of adjacent elements n _max is 1 or more (in S86). (YES), a search for an adjacent element that can be supplied with molten metal is instructed (step S87), and then a molten metal supply calculation from the adjacent element is performed (step S88). The CPU repeatedly executes the loop processing from step S87 to step S89 until the search is completed for adjacent elements that can be refilled with molten metal. Then, when the loop processing is completed for the adjacent elements that can be replenished with molten metal, the CPU ends the series of processing operations for shrinkage nest calculation B, and proceeds to step S49 in FIG.

[program]
When performing solidification analysis of a cast product, the process of setting the atmospheric pressure load unit 22 and the process of predicting the occurrence of shrinkage defects using the atmospheric pressure as one of analysis parameters are microcomputers that are examples of computers. Can be executed by a program instruction. More specifically, the series of processes in the flowcharts of FIGS. 3 to 10 executed under the control of the CPU of the microcomputer can be executed by program instructions for the CPU.

  A program according to an embodiment of the present invention that causes the CPU to execute this series of processing may be preinstalled in the ROM of the microcomputer. However, the present invention is not limited to this, and can be provided by wired or wireless communication means, or can be provided by being stored in a storage medium such as a computer-readable IC card or USB memory. It is.

[Concept of conventional shrinkage nest prediction method]
Here, the concept of the conventional shrinkage nest prediction method will be described with reference to FIG. FIG. 11 is an example of a cross-sectional view of a casting schematically showing the concept of a conventional shrinkage cavity prediction method. The time advances from FIG. 11A → FIG. 11B → FIG. 11C.

  The molten metal replenishment is performed in the direction of gravity, that is, from the uppermost part to the lowermost part. The portion 23 other than the free flow region is a portion equal to or greater than the value defined as the flow limit solid phase ratio. The portion 24 of the free flow region is a region below the value defined as the flow limit solid phase ratio. In this way, the shrinkage defect is generated from the uppermost portion of the free flow region portion 24. And the generation | occurrence | production position of the shrinkage defect 26 and 27 will be estimated in the position shown in figure.

  In FIG. 11A, the shrinkage defect 26 is generated at a position gravitationally above the head difference indicated by Δh. In FIG. 11B, similarly, the shrinkage defect 27 is generated at a position located gravitationally above. In FIG. 11C, the shrinkage nest defect 27 grows at the position shown in the figure in a state where the solidification is almost completed. Eventually, the occurrence position of the shrinkage defect is predicted at two locations, the position of the shrinkage defect 26 and the position of the shrinkage defect 27.

[Concept of shrinkage nest prediction method of this embodiment]
Next, the concept of the shrinkage nest prediction method of this embodiment will be described with reference to FIG. FIG. 12 is an example of a sectional view of a casting schematically showing the concept of the shrinkage cavity prediction method of the present embodiment.

  In the casting solidification analysis apparatus 10 according to the present embodiment, the molten metal replenishment is performed from the molten metal portion in contact with the atmospheric pressure load portion 22 in addition to the gravity direction. By applying the atmospheric pressure to the free flow region portion 24 by the atmospheric pressure load section 22, the molten metal replenishment is performed in the direction opposite to the gravity direction, that is, from the bottom to the top.

  The time advances from FIG. 12A to FIG. 12B to FIG. 12C. The portion 23 other than the free flow region is a portion equal to or greater than the value defined as the flow limit solid phase ratio. The portion 24 of the free flow region is a region below the value defined as the flow limit solid phase ratio. The shrinkage defect occurs in contact with the atmospheric pressure load portion 22 and grows as the shrinkage defect 25.

  In FIG. 12A, atmospheric pressure acts on the entire region 24 of the free flow region through the atmospheric pressure load portion 22. As a result, the molten metal is also supplied to the portion corresponding to the shrinkage defect 26 shown in FIG. As a result, the occurrence position of the shrinkage defect is predicted only at one position of the shrinkage defect 25 in FIG. 12C.

  FIG. 13 shows the portion of the free flow region portion 24 shown in FIG. 12 where the molten metal remains after a certain time as the solidification progresses, but the state where the free flow is impossible, that is, the solid fraction is the flow limit. It is an example of the figure which shows part 24 'other than the free-flow region of a part more than a solid phase rate and less than one.

  The casting portion outside the portion 24 ′ other than the free flow region is a solidification completed portion where the solid phase ratio has reached 1. Since the amount of the solid phase is large in the region 24 ′ other than the free flow region, the molten metal cannot move quickly over a wide range. Therefore, transfer of molten metal replenishment is performed only between adjacent elements. At this time, the replenishment direction of the molten metal is performed from the higher temperature to the lower temperature without considering the atmospheric pressure load portion 22 and the gravity direction. As a result, a slight shrinkage defect is predicted in the region of the portion 24 ′ other than the free flow region.

  In FIG. 13, shrinkage defect 26, 27 indicates a shrinkage defect predicted by the conventional shrinkage prediction method in the above-described free flow region.

  FIG. 14 is an example of a perspective view showing the overall shape of the casting used in the present embodiment.

  The casting 30 includes a molten metal injection port 31 disposed in the mold, a runner 32 for introducing the molten metal from the injection port 31 to the casting main body, and casting portions 33a, 33b, and 33c. The atmospheric pressure load portion 22 is made of a refractory material having good air permeability. About subsequent description, it carries out about A-A 'cross-section part containing casting part 33a, 33b, 33c.

  FIG. 15 is an example of a diagram showing a position where an actual shrinkage defect occurs in the casting used in the present embodiment, and corresponds to a cross-sectional view taken along line A-A ′ of FIG. 14. The actual sectional view of the casting is obtained by, for example, a dye flaw detection test. The dye flaw detection test is a non-destructive inspection method that detects a shrinkage defect using a test solution having good red or fluorescent permeability.

  In FIG. 15, a cast part 41a corresponds to the cast part 33a in FIG. 14, and a cast part 41c corresponds to the cast part 33c in FIG. Moreover, the part 42 shown with a dashed-dotted line is a part corresponded to the atmospheric pressure load part 22 of FIG. 14, Comprising: It is the part removed with the mold sand.

  In the casting portion 41a, shrinkage defects are generated in the broken circles 43 and 44 shown in the figure. In the casting portion 41c, a shrinkage defect is generated in a broken-line circle 45 shown in the figure. Among these shrinkage defects, shrinkage defects generated in the broken-line circles 44 and 45 are densely interspersed with minute cavities.

  FIG. 16 is an example of a diagram showing a distribution of time for the casting used in the present embodiment to reach the set flow limit solid phase ratio. This is obtained in the course of the simulation, and shows a state at the A-A ′ cross section shown in FIG. 14.

  In FIG. 16, a cast part 51a corresponds to the cast part 33a in FIG. 14, and a cast part 51c corresponds to the cast part 33c in FIG. Directional solidification toward the atmospheric pressure load 52, which is mostly air permeable, is achieved. From this, according to this embodiment, most of the shrinkage nest calculation is performed in the step (step S47) of the shrinkage nest calculation A in FIG. On the other hand, in the inner area surrounded by the broken lines 53 and 54 in the figure, the directional solidification in the direction of the atmospheric pressure load section 52 has not been achieved. Therefore, in this area, the step of the shrinkage nest calculation B in FIG. This is performed in S48).

  FIG. 17 is an example of a diagram showing shrinkage cavity prediction results according to the conventional method for the casting used in the present embodiment, and corresponds to the A-A ′ sectional view of FIG. 14.

  In FIG. 17, a cast part 61a corresponds to the cast part 33a in FIG. 14, and a cast part 61c corresponds to the cast part 33c in FIG. The atmospheric pressure load unit 62 is not set in the conventional shrinkage nest prediction method, but is set as one of the constituent members for comparison with the shrinkage nest prediction method according to the present embodiment. In the conventional shrinkage nest prediction method, shrinkage defects are predicted within four broken circles 63, 64, 65, 66 shown in the figure. When this is compared with the actual occurrence position of the shrinkage nest defect shown in FIG. 15, among the predicted shrinkage nest defects in the dashed circles 63, 64, 65, 66, the shrinkage in the broken circle 66 is shown. Nest defects are not present in actual castings.

  Since the conventional shrinkage cavity prediction method only considers the direction of gravity, the molten metal is replenished downward from the upper part of each casting. Therefore, the shrinkage defect in the broken line circle 66 is formed above the casting part 61c. Is predicted.

  FIG. 18 is an example of a diagram showing a shrinkage cavity prediction result by the shrinkage cavity prediction method according to this embodiment for the casting used in this embodiment, and corresponds to the A-A ′ sectional view of FIG. 14.

  In FIG. 18, a cast part 71a corresponds to the cast part 33a in FIG. 14, and a cast part 71c corresponds to the cast part 33c in FIG. An atmospheric pressure load portion 72 is set at the uppermost portion of the casting portion 33a. According to the shrinkage nest prediction method according to this embodiment, shrinkage nest defects are predicted within the three broken circles 73, 74, and 75 shown in the figure. When this is compared with the actual occurrence position of the shrinkage defect shown in FIG. 15, the predicted shrinkage defects in the broken circles 73, 74, and 75 are within the broken circles 43, 44, and 45 in FIG. It responds well to the shrinkage defects. The fact that the shrinkage defect is not predicted at the upper part of the casting part 71c is also consistent with the situation at the upper part of the casting part 41c in FIG.

  The shrinkage defect does not occur in the upper part of the casting portion 71a. Even if a shrinkage cavity is formed here, the molten metal is pushed up by the action of the atmospheric pressure from the atmospheric pressure load portion 72, and the cavity is thereby caused by the molten metal. Because it will be buried.

  As described above, in the present embodiment, when performing the solidification analysis of the cast product, the atmospheric pressure load unit 22 that applies atmospheric pressure to the free flow region that is in a viscous flow state is set, and the atmospheric pressure load unit 22 is set. The generation of shrinkage defects is predicted using the atmospheric pressure given by the above as one of the analysis parameters. As a result, the occurrence of shrinkage defect can be accurately predicted even for a casting having a special shape such as a casting (eg, a side riser) with a feeder at a position lower than the uppermost portion of the casting body. . This is also clear from a comparison between FIG. 15 showing the actual state of shrinkage defect generation and FIG. 18 showing the shrinkage prediction result by the shrinkage prediction method according to the present embodiment.

  Here, for example, when a mold used for actual casting has a through hole for introducing molten metal or a through hole for taking out air, the atmospheric pressure load portion 22 is provided at a position corresponding to the through hole. It is preferable to set. Thereby, in actual casting, since the occurrence of shrinkage defect can be predicted in consideration of the atmospheric pressure acting through the through hole, the prediction accuracy of the occurrence of shrinkage defect can be further increased. As a result, since the occurrence of shrinkage defects can be suppressed in actual casting, a high-quality cast product can be manufactured.

  However, the setting position of the atmospheric pressure load unit 22 is not limited to the above setting example. For example, when the atmospheric pressure load unit 22 is set at an arbitrary position, the occurrence of shrinkage defect is predicted based on the atmospheric pressure load unit 22, and the good prediction result is obtained, it corresponds to the set position of the atmospheric pressure load unit 22. Thus, a through hole can be provided in an actual mold. Thereby, in the actual casting, since the predicted result of the occurrence of the shrinkage cavity defect can be faithfully reflected, the occurrence of the shrinkage cavity defect can be suppressed, and a high-quality cast product can be manufactured.

[Modification]
The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. For example, each functional unit shown in FIG. 1 may be realized by hardware in addition to the case where it is realized by software, for example, by designing a part or all of them by an integrated circuit.

  DESCRIPTION OF SYMBOLS 10 ... Casting solidification analysis apparatus, 11 ... Preprocessor part, 12 ... Solidification analysis execution part, 13 ... Post processor part, 21 ... Mold, 22, 52, 62, 72 ... Atmospheric pressure load part, 23 ... Parts other than free flow area 24 ... Free-flow region 25, 26, 27 ... Shrinkage defect

Claims (7)

When performing a solidification analysis of a cast product, a setting step for setting an atmospheric pressure load section that applies atmospheric pressure to a portion of a free flow region that is in a viscous flow state;
An analysis execution step of predicting the occurrence of shrinkage defect using the atmospheric pressure applied to the part of the free flow region by the atmospheric pressure load part as one of analysis parameters;
The casting solidification analysis method characterized by performing each process of. In the setting step, the free flowable elements are grouped into element groups connected on one or more surfaces, and when the free flowable group to which the search target element belongs is in contact with the atmospheric pressure load portion, The casting solidification analysis method according to claim 1, wherein the molten metal replenishment calculation for compensating for the shrinkage in the free flow region is a molten metal replenishment calculation from the atmospheric pressure load section. The molten metal replenishment calculation from the molten metal element in contact with the atmospheric pressure load part is performed in the setting step when the molten metal element in contact with the atmospheric pressure load area is emptied by molten metal replenishment. The casting solidification analysis method described. In the setting step, when a free flowable group to which the element to be searched belongs does not contact the atmospheric pressure load portion, a melt replenishment calculation for compensating for the shrinkage in the free flow region portion is performed from the highest temperature portion. The casting solidification analysis method according to claim 2, wherein molten metal supply calculation is performed. In the setting step, when the element of the highest temperature part is emptied by the molten metal supply, the next highest temperature part is changed to the highest temperature part, and the molten metal supply calculation from the highest temperature part is performed. The casting solidification analysis method according to claim 4. When performing solidification analysis of a cast product, a setting unit that sets an atmospheric pressure load unit that applies atmospheric pressure to a portion of a free flow region that is in a viscous flow state;
An analysis execution unit that predicts the occurrence of shrinkage defects using the atmospheric pressure applied to the portion of the free flow region by the atmospheric pressure load unit as one of the analysis parameters;
A casting solidification analysis device comprising: When performing solidification analysis of a cast product, a process of setting an atmospheric pressure load section that applies atmospheric pressure to a portion of a free flow region that is in a viscous flow state;
A process of predicting the occurrence of shrinkage defects using the atmospheric pressure applied to the free flow region by the atmospheric pressure load as one of the analysis parameters;
A program that causes a computer to execute.