Method for estimating gas content in die-cast products

Abstract

To provide a method for estimating a gas amount in a die-cast product, which has high versatility and good prediction accuracy.SOLUTION: In a specific gravity measurement step, an aluminum die-cast product 10 cast under a plurality of casting conditions is heated for a predetermined time at a predetermined temperature below the melting point, and the specific gravity of the aluminum die-cast product 10 after heating is measured. In a gas amount measurement step, the aluminum die-cast product 10 cast under a plurality of casting conditions which are the same conditions as the aluminum die-cast product 10 used in the specific gravity measurement step is prepared, and an amount of gas generated by vacuum melting each of the aluminum die-cast products 10 cast under the plurality of casting conditions is measured. In a gas amount estimation step, based on the specific gravity measured in the specific gravity measurement step and the gas amount measured in the gas amount measurement step, the heating condition under which the relationship between the specific gravity and the gas amount for each of the plurality of casting conditions represents the most is extracted, and by measuring the specific gravity of the aluminum die-cast product 10 on which the heating condition is executed, the gas amount of the aluminum die-cast product 10 is estimated from the measured specific gravity.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for estimating the amount of gas in a die-cast product. [Background technology]

[0002] One factor that can degrade the quality of die-cast products is the presence of gases that are generated during the casting process. These gases cause defects such as shrinkage cavities and blowholes inside the die-cast product, which can lead to defects if not treated appropriately.

[0003] Conventionally, a method for measuring the amount of gas inside a die-cast product involves melting the die-cast product in a vacuum chamber and measuring the volume of the gas generated. However, applying this method to all target die-cast products requires a great deal of time and cost. Therefore, in recent years, the amount of gas in a die-cast product has been estimated using a related index rather than directly measuring it. For example, Patent Document 1 below discloses a method for determining whether the amount of gas inside a die-cast product is greater than a reference value by cutting a test piece formed near a weld in the die-cast product, calculating the bulge ratio based on the specific gravity of the test piece before and after heat treatment, and comparing the bulge ratio with a predetermined threshold value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-279667 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the above method, it may be difficult to set a threshold value depending on the heating temperature and type of steel of the die-cast product, and there is room for improvement in terms of prediction accuracy.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for estimating the amount of gas in a die-cast product that is highly versatile and has good prediction accuracy. [Means for solving the problem]

[0007] The present invention will be described below. In order to facilitate understanding of the present invention, reference numbers in the accompanying drawings are added in parentheses, but the present invention is not limited to the illustrated forms.

[0008] The method for estimating the amount of gas in a die-cast product according to the present invention includes a specific gravity measurement step of heating an aluminum die-cast product (10) cast under a plurality of casting conditions at a predetermined temperature below the melting point for a predetermined time and measuring the specific gravity of the aluminum die-cast product (10) after heating; a gas amount measurement step of preparing aluminum die-cast products (10) cast under a plurality of casting conditions that are the same as the aluminum die-cast product (10) used in the specific gravity measurement step and vacuum-melting each of the aluminum die-cast products (10) cast under the plurality of casting conditions to measure the amount of gas generated; and a gas amount estimation step of extracting heating conditions that best express the relationship between specific gravity and gas amount for each of the plurality of casting conditions based on the specific gravity measured in the specific gravity measurement step and the gas amount measured in the gas amount measurement step, measuring the specific gravity of the aluminum die-cast product heated under that heating condition, and estimating the amount of gas in the aluminum die-cast product (10) from the measured specific gravity.

[0009] In the method for estimating the amount of gas in a die-cast product according to the present invention, the plurality of casting conditions for the aluminum die-cast product (10) can include the type of steel for the aluminum die-cast product (10).

[0010] Furthermore, the present invention other Method for estimating gas content in die-cast products The method includes a specific gravity measurement step of heating aluminum die-cast products (10) cast under a plurality of casting conditions at a predetermined temperature below the melting point for a predetermined time and measuring the specific gravity of the aluminum die-cast products (10) after heating, and a gas amount measurement step of preparing aluminum die-cast products (10) cast under a plurality of casting conditions that are the same as the aluminum die-cast products (10) used in the specific gravity measurement step, and vacuum-melting each of the aluminum die-cast products (10) cast under the plurality of casting conditions to measure the amount of gas generated, thereby finding a correspondence between the amount of gas in the aluminum die-cast product (10) and the specific gravity. At 94% to 95% of the liquidus temperature of the aluminum die-casting product (10) The method is characterized by carrying out a gas amount estimation step in which the aluminum die-cast product (10) is heated, the specific gravity of the heated aluminum die-cast product (10) is measured, and the gas amount of the aluminum die-cast product (10) is estimated from the measured specific gravity.

[0011] Book Related to the invention other In the method for estimating the amount of gas in die-cast products, The plurality of casting conditions for the aluminum die-cast product (10) may include the type of steel for the aluminum die-cast product (10). [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a method for estimating the amount of gas in a die-cast product that is highly versatile and has good prediction accuracy. [Brief explanation of the drawings]

[0013] [Figure 1] 1A and 1B are diagrams showing an aluminum die-cast product according to the present embodiment, in which FIG. 1A is a plan view and FIG. 1B is a front view. [Figure 2] 1 is a graph showing the correspondence relationship between heating conditions, specific gravity, and gas amount for steel type A, where sub-diagram (a) shows the correspondence relationship when the heating temperature is 560°C, and sub-diagram (b) shows the correspondence relationship when the heating temperature is 570°C. [Figure 3] 1 is a graph showing the correspondence relationship between heating conditions, specific gravity, and gas amount for steel type B, where sub-diagram (a) shows the correspondence relationship when the heating temperature is 550°C, and sub-diagram (b) shows the correspondence relationship when the heating temperature is 560°C. [Figure 4] 1 is a graph showing the correspondence relationship between heating conditions, specific gravity, and gas amount for steel type C, where sub-diagram (a) shows the correspondence relationship when the heating temperature is 540°C, and sub-diagram (b) shows the correspondence relationship when the heating temperature is 550°C. [Figure 5] FIG. 1 is a diagram showing the relationship between the amount of gas and the specific gravity after steel type A is heated at a heating temperature of 570°C for 30 minutes. [Figure 6] FIG. 1 is a diagram showing the relationship between the amount of gas and the specific gravity after steel type B is heated at a heating temperature of 560° C. for 30 minutes. DETAILED DESCRIPTION OF THE INVENTION

[0014] In devising the method for estimating the amount of gas in a die-cast product according to the present invention, the inventors conducted extensive research and came up with the idea that there is a certain correlation between the amount of gas generated inside an aluminum die-cast product and the specific gravity of the aluminum die-cast product, and that the degree of this correlation varies depending on the heating conditions of the aluminum die-cast product. The process of this idea is explained below. First, the configuration of an aluminum die-cast product 10 according to this embodiment, which was used to investigate this correlation, is explained using FIG. 1. Here, FIG. 1 shows an aluminum die-cast product 10 according to this embodiment, with sub-figure (a) being a plan view and sub-figure (b) being a front view.

[0015] 1, the aluminum die-cast product 10 according to this embodiment is formed in the shape of a flat plate with a substantially rectangular plane, and is formed by injecting molten metal into a cavity defined by a fixed mold and a movable mold that constitute a die-casting mold, and allowing the molten metal to solidify within the cavity. Note that the aluminum die-cast product 10 is not limited to a flat plate shape, and various shapes may be used depending on the application.

[0016] The aluminum die-cast product 10 is formed under a plurality of casting conditions using different steel types for the molten metal. Here, the steel types used for the aluminum die-cast product 10 were RMH-TMH (steel type A), 10Si (steel type B), and ADC12-T3 (steel type C), which is ADC12 subjected to T3 treatment, manufactured by Ryobi Ltd. Note that various steel types other than those mentioned above can also be used for the aluminum die-cast product 10.

[0017] The above describes the configuration of the aluminum die-cast product 10 according to this embodiment. After casting the aluminum die-cast product 10 using various steel types, the inventors carried out the following steps to investigate the correspondence between the heating conditions, specific gravity, and gas amount of the aluminum die-cast product 10.

[0018] [Specific gravity measurement process] First, the specific gravity of the aluminum die-cast product 10 cast using each steel type was measured before heating (heating time 0 minutes). Next, the heating temperature of the aluminum die-cast product 10 was increased to a predetermined temperature just before the melting point of each steel type, and the specific gravity was measured after 30 minutes of heating and after 60 minutes of heating. The temperatures just before the melting point of each steel type were 560°C and 570°C for steel type A, 550°C and 560°C for steel type B, and 540°C and 550°C for steel type C. The specific gravity was measured by measuring the weight of the aluminum die-cast product 10 in air and in a liquid with a known specific gravity (e.g., water), calculating the buoyancy of the aluminum die-cast product 10, and calculating the volume of the aluminum die-cast product 10 from the buoyancy and the specific gravity of the liquid. The weight of the aluminum die-cast product 10 in air was then divided by the volume. Furthermore, the aluminum die-cast product 10 was heated using an electric furnace.

[0019] [Gas volume measurement process] Next, aluminum die-cast products 10 were prepared by casting using the same steel type and heating under the same heating conditions as the aluminum die-cast products 10 used in the specific gravity measurement process, and the amount of gas was measured for each aluminum die-cast product 10 corresponding to each steel type and heating condition. The gas amount was measured by melting the die-cast product 10 in a vacuum chamber and measuring the volume of gas generated.

[0020] [Relationship between heating conditions, specific gravity and gas amount] The heating conditions, specific gravity, and gas amount of the aluminum die-cast product 10 obtained by the above process were correlated. The results are shown in Figures 2 to 4. Here, Figure 2 is a graph showing the correspondence relationship between heating conditions, specific gravity, and gas amount for steel type A, with sub-diagram (a) showing the correspondence relationship when the heating temperature is 560°C and sub-diagram (b) showing the correspondence relationship when the heating temperature is 570°C. Also, Figure 3 is a graph showing the correspondence relationship between heating conditions, specific gravity, and gas amount for steel type B, with sub-diagram (a) showing the correspondence relationship when the heating temperature is 550°C and sub-diagram (b) showing the correspondence relationship when the heating temperature is 560°C. Furthermore, FIG. 4 is a graph showing the correspondence relationship between heating conditions, specific gravity, and gas amount for steel type C, where sub-diagram (a) in the figure shows the correspondence relationship when the heating temperature is 540°C, and sub-diagram (b) in the figure shows the correspondence relationship when the heating temperature is 550°C.

[0021] First, we investigated the relationship between heating conditions, specific gravity, and gas volume for steel types A and B. As shown in sub-diagram (a) in Figure 2, when the heating temperature of aluminum die-cast product 10 was relatively low, the variation in specific gravity increased as the heating time increased, and no correlation was observed between specific gravity and gas volume. Furthermore, as shown in sub-diagram (a) in Figure 3, when the heating temperature of aluminum die-cast product 10 was relatively low, the specific gravity remained constant regardless of the heating time, and no correlation was observed between specific gravity and gas volume. On the other hand, as shown in sub-diagrams (b) in Figure 2 and (b) in Figure 3, when the heating temperature was relatively high, the specific gravity tended to decrease as the heating time increased, with the increase in the gas volume of aluminum die-cast product 10.

[0022] Next, we investigated the relationship between heating conditions, specific gravity, and gas amount for steel type C. Here, the results of gas amount measurement in the gas amount measurement process showed that all aluminum die-cast products 10 cast using steel type C showed low gas amounts. As shown in sub-diagram (a) in Figure 4, when the heating temperature of aluminum die-cast product 10 was relatively low, the specific gravity varied as the heating time increased. On the other hand, as shown in sub-diagram (b) in Figure 4, when the heating temperature of aluminum die-cast product 10 was relatively high, the variation in specific gravity tended to be relatively small regardless of the length of heating time.

[0023] As described above, when the heating temperature is relatively high, the difference in specific gravity depending on the gas amount of the aluminum die-cast product 10 becomes clear, and the variation in specific gravity between aluminum die-cast products 10 with similar gas amounts tends to be smaller. It was also shown that the above trend can be sufficiently observed with a heating time of 30 minutes. On the other hand, when the heating temperature is relatively low, no correlation was observed between specific gravity and gas amount.

[0024] [Determining the heating temperature] Next, the inventors investigated the heating conditions that best reveal the relationship between the specific gravity and gas volume of the aluminum die-cast product 10. That is, they investigated the heating temperature that clearly shows the difference in specific gravity depending on the gas volume of the aluminum die-cast product 10 and that shows a tendency for the variation in specific gravity to be small between aluminum die-cast products 10 with similar gas volumes. The results are shown in Table 1 below. Table 1 is a chart showing the liquidus temperatures of steel types A, B, and C, and the temperatures corresponding to 93% to 96% of the liquidus temperature.

[0025] [Table 1]

[0026] As shown in Figures 2 to 4, the heating temperatures at which the relationship between the specific gravity and gas volume of the aluminum die-cast product 10 appears are 570°C for steel type A, 560°C for steel type B, and 550°C for steel type C. These temperatures correspond to the temperature range of 94% to 95% of the liquidus temperature in Table 1. When the correlation between specific gravity and gas volume was confirmed at temperatures below 94% of the liquidus temperature of the aluminum die-cast product 10, the above-mentioned trend was not observed. Furthermore, at temperatures exceeding 95% of the liquidus temperature of the aluminum die-cast product 10, a portion of the aluminum die-cast product 10 thermally deformed, making it impossible to obtain satisfactory measurement results. From the above, it was determined that the heating temperature, among the heating conditions, is preferably 94% to 95% of the liquidus temperature of the aluminum die-cast product 10.

[0027] [Gas volume estimation process] Finally, the inventors attempted to estimate the gas amount from the specific gravity using the correspondence relationship between the heating time, specific gravity, and gas amount of the aluminum die-cast product 10. Specifically, the relationship between the specific gravity and gas amount of the aluminum die-cast product 10 was determined using FIGS. 5 and 6 when the heating temperature was set to a temperature corresponding to 94% to 95% of the liquidus temperature of the aluminum die-cast product 10 (570°C for steel type A and 560°C for steel type B). Here, FIG. 5 shows the correspondence relationship between the gas amount and specific gravity after steel type A was heated at a heating temperature of 570°C for 30 minutes. Furthermore, FIG. 6 shows the correspondence relationship between the gas amount and specific gravity after steel type B was heated at a heating temperature of 560°C for 30 minutes.

[0028] The inventors applied a linear function to experimental data showing the correspondence between the amount of gas and the specific gravity in the aluminum die-cast product 10, as shown by the dashed lines in FIGS. 5 and 6. The coefficient of determination (R 2 ) was calculated, the coefficient of determination for steel type A was R 2 =0.9727, the coefficient of determination for steel type B is R 2 = 0.9397, and it was confirmed that the experimental data could be well approximated by a linear function. 2) is an index that represents the goodness of fit of the estimated regression equation to the data, and the closer this value is to 1, the better the approximation to the data.

[0029] From the above, it was confirmed that the gas amount can be accurately estimated from the specific gravity of the aluminum die-cast product 10. In this embodiment, temperatures that are 94% to 95% of the liquidus temperature of the aluminum die-cast product 10 cast using each steel type were extracted as the heating temperature among the heating conditions. By adopting a method of determining the heating temperature based on the liquidus temperature in this way, even if the steel type is changed, the heating temperature corresponding to the steel type can be immediately determined, providing a highly versatile method of estimating the gas amount of a die-cast product. In other words, the multiple casting conditions for aluminum die-cast products in the present invention can include aluminum die-cast products of all steel types.

[0030] Furthermore, according to the present invention, by adopting the above-mentioned heating temperature at which the relationship between the specific gravity of the aluminum die-cast product 10 and the amount of gas is most apparent, it is possible to provide a method for estimating the amount of gas in a die-cast product with good prediction accuracy.

[0031] Although the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the scope described in the above embodiments. Various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included in the technical scope of the present invention. [Explanation of symbols]

[0032] 10 Aluminum die-cast product.

Claims

1. a specific gravity measurement step of heating aluminum die-cast products cast under a plurality of casting conditions at a predetermined temperature below the melting point for a predetermined time, and measuring the specific gravity of the aluminum die-cast products after heating; a gas amount measuring step of preparing aluminum die-cast products cast under a plurality of casting conditions that are the same as the aluminum die-cast product used in the specific gravity measuring step, and measuring the amount of gas generated by vacuum melting each of the aluminum die-cast products cast under the plurality of casting conditions; a gas amount estimation step of extracting heating conditions that best represent the relationship between specific gravity and gas amount for each of a plurality of casting conditions based on the specific gravity measured in the specific gravity measurement step and the gas amount measured in the gas amount measurement step, measuring the specific gravity of an aluminum die-cast product under the selected heating condition, and estimating the gas amount of the aluminum die-cast product from the measured specific gravity; A method for estimating the amount of gas in a die-cast product, comprising:

2. 2. The method for estimating a gas amount in a die-cast product according to claim 1, The method for estimating the amount of gas in a die-cast product, wherein the plurality of casting conditions for the aluminum die-cast product include the type of steel of the aluminum die-cast product.

3. A specific gravity measurement process in which aluminum die-cast products cast under a plurality of casting conditions are heated at a predetermined temperature below the melting point for a predetermined time, and the specific gravity of the aluminum die-cast products after heating is measured; a gas amount measuring step of preparing aluminum die-cast products cast under a plurality of casting conditions that are the same as the aluminum die-cast product used in the specific gravity measuring step, and measuring the amount of gas generated by vacuum melting each of the aluminum die-cast products cast under the plurality of casting conditions; By carrying out the above, the correspondence relationship between the amount of gas and the specific gravity of the aluminum die-cast product is found in advance, and further, A gas amount estimation method for a die-cast product, comprising: heating an aluminum die-cast product at a temperature that is 94% to 95% of the liquidus temperature of the aluminum die-cast product; measuring the specific gravity of the aluminum die-cast product that has been heated; and estimating the gas amount of the aluminum die-cast product from the measured specific gravity.

4. A method for estimating the amount of gas in a die-cast product according to claim 3, comprising: The method for estimating the amount of gas in a die-cast product, wherein the plurality of casting conditions for the aluminum die-cast product include the type of steel of the aluminum die-cast product.

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