Method for predicting erosion of mold

Abstract

To accurately predict erosion of a mold.SOLUTION: A method for predicting erosion of a mold (1) that forms a cavity (1a) into which molten metal (2) is filled includes: an area specifying step (step S1) of specifying an area in the cavity (1a), where a predetermined phenomenon occurs; and an area specifying step (S2) of specifying an area in the mold (1), where erosion is likely to occur, based on the results obtained in the area specifying step (step S1). Furthermore, the area specification step (step S1) includes a first step (step S11) of specifying an area (R11) where the molten metal pressure in the cavity (1a) becomes large during the filling of the molten metal (2).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for predicting erosion of a mold.

Background Art

[0002] A die-casting method is known in which a molten metal is filled into a cavity formed in a pair of mold halves that can be opened and closed, and the molten metal is cooled and solidified to obtain a die-cast product. In this type of die-casting method, since the high-temperature molten metal is repeatedly filled into the cavity, erosion occurs in the mold that forms the cavity as the number of casting shots increases. As a result, the shape of the eroded mold is transferred to the die-cast product cast from the mold, and problems such as the dimensions of the die-cast product not meeting the required values occur. Therefore, attempts have been made to predict in advance the occurrence of abnormalities during operation.

[0003] For example, in Patent Document 1 below, in order to predict in advance the occurrence of defects in die-cast products, a plurality of factors affecting casting are selected, each factor is measured and calculated during operation, and this is compared with a preset determination criterion to determine whether the cause of the occurrence of defects is occurring and to give a warning. A system is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the invention described in Patent Document 1 above not only requires setting determination criteria through a large number of experiments and trial and error in advance, but also there may be differences in the determination results depending on the set determination criteria, and there are problems in making predictions with high accuracy.

[0006] The present invention has been made in view of the problems existing in the above-described prior art, and its object is to indicate important factors for predicting regions where the mold is likely to be eroded, and to accurately predict mold erosion by determining locations where erosion is likely to occur in the mold based on the obtained prediction.

Means for Solving the Problems

[0007] The present invention will be described below. For ease of understanding of the present invention, reference numerals of the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated forms thereby.

[0008] The method for predicting erosion of a mold according to the present invention is a method for predicting erosion of a mold (1) constituting a cavity (1a) filled with molten metal (2), and includes a region specifying step (step S1) of specifying a region where a predetermined phenomenon occurs in the cavity (1a), and a region determining step (step S2) of determining a region where erosion is likely to occur in the mold (1) based on the result obtained in the region specifying step (step S1). The region specifying step (step S1) is characterized by having a first step (step S11) of specifying a region (R11) where the fluctuation of the molten metal pressure in the cavity (1a) becomes large during the filling of the molten metal (2).

[0009] Further, in the method for predicting erosion of a mold according to the present invention, the region specifying step (step S1) may include a second step (step S12) of specifying a region (R12) where the amount of air entrainment in the cavity (1a) becomes large during the filling of the molten metal (2).

[0010] Further, in the method for predicting erosion of a mold according to the present invention, the region specifying step (step S1) may include a third step (step S13) of specifying a region (R13) where a filling delay of the molten metal (2) occurs in the cavity (1a).

[0011] Also, in the mold erosion prediction method according to the present invention, the region specifying step (step S1) may include a fourth step (step S14) of specifying a region (R14) where the flow velocity of the molten metal (2) increases within the cavity (1a).

Effect of the Invention

[0012] According to the present invention, by indicating important factors for predicting regions where the mold is likely to be eroded and determining locations in the mold where erosion is likely to occur based on the obtained prediction, mold erosion prediction can be performed with high accuracy.

Brief Description of the Drawings

[0013]

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Embodiment for Carrying Out the Invention

[0014] Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. Note that the following embodiments do not limit the invention according to each claim, and not all combinations of the features described in the embodiments are essential for the solution means of the invention.

[0015] Before explaining the erosion prediction method of the mold according to this embodiment, first, based on FIGS. 1 and 2, the overall configuration of a general die-casting apparatus in which the erosion prediction method of the mold of this embodiment is executed will be described. Here, FIGS. 1 and 2 are cross-sectional views showing an example of the overall configuration of a die-casting apparatus including a general mold 1. In particular, FIG. 1 shows the state before the filling of the molten metal, and FIG. 2 shows the state after the filling of the molten metal. As shown in FIGS. 1 and 2, the mold 1 is provided as a main component of a die-casting apparatus for performing die-casting.

[0016] The exemplary general mold 1 has a fixed mold 10 including a fixed die 12 and a fixed holder 11, and a movable mold 20 including a movable die 22 and a movable holder 21. A cavity 1a is defined by the fixed die 12 and the movable die 22. Further, a sleeve 30 is provided in the mold 1. The sleeve 30 communicates with the cavity 1a via a sprue 1b, a main runner 1c, and a main gate 1d. Further, the cavity 1a communicates with an exhaust gate 1f (not shown), an exhaust runner 1e, and an overflow 50 (shown in FIG. 3 described later). A plunger tip 31 is provided in the sleeve 30. The plunger tip 31 can move forward and backward within the sleeve 30. Further, a diverter 40 is provided at the position of the sprue 1b which is the position facing the forward direction of the plunger tip 31. When the plunger tip 31 moves forward within the sleeve 30 and presses the molten metal 2, the molten metal 2 is filled into the cavity 1a via the sprue 1b, the main runner 1c, and the main gate 1d.

[0017] From the state shown in FIG. 1, by moving the plunger tip 31 to the state shown in FIG. 2, the molten metal 2 that has been pressed by the plunger tip 31 and sent into the sleeve 30 collides with the diverter 40. The molten metal 2 that has collided with the diverter 40 is configured to be guided to the main runner 1c and the main gate 1d by the diverter 40.

[0018] Next, the specific shape inside the mold 1 in which the mold erosion prediction method according to the present embodiment is executed will be described with reference to FIG. 3.

[0019] FIG. 3 is a diagram showing the inside of the mold 1 according to the present embodiment. The cavity 1a formed by the mold 1 according to the present embodiment includes an opening forming portion 61 and a protrusion forming portion 62. Further, the lower part of the cavity 1a communicates with the main gate 1d, the main runner 1c, and the sprue 1b respectively, the upper part of the cavity 1a communicates with the exhaust gate 1f and the exhaust runner 1e respectively, and both side portions of the cavity 1a communicate with a pair of overflows 50 respectively.

[0020] Note that the erosion prediction method for the mold 1 according to this embodiment is performed by simulation. Therefore, a two-dimensional shape model corresponding to the mold 1 shown in FIG. 3 is defined, and predetermined conditions are set. In the following steps, based on these condition settings, a heat flow analysis (molten metal flow analysis) is performed to calculate data of a predetermined phenomenon, thereby identifying the corresponding region. Note that the calculation method is not particularly limited, and known or commonly used methods can be used.

[0021] Next, based on FIGS. 4 and 5, the steps of the mold erosion prediction method will be described. Here, FIG. 4 is a flowchart for explaining the steps of the mold erosion prediction method for the mold 1 according to this embodiment, and FIG. 5 is a flowchart for explaining the specific processing content of the region identification step in the flowchart shown in FIG. 4.

[0022] As shown in FIG. 4, the mold erosion prediction method for the mold 1 according to this embodiment includes a region identification step (step S1) and a region determination step (step S2). Each step will be sequentially described below.

[0023] In the mold erosion prediction method for the mold 1 according to this embodiment, first, in the region identification step, a region where a predetermined phenomenon occurs within the cavity 1a defined by the mold 1 is identified (step S1). Specifically, identification of a region where the fluctuation of the molten metal pressure becomes large (step S11), identification of a region where the amount of air entrainment becomes large (step S12), identification of a region where a filling delay of the molten metal occurs (step S13), and identification of a region where the flow velocity of the molten metal becomes large (step S14) are respectively performed.

[0024] Here, the region identification step (step S1) only needs to include at least step S11. As combinations of steps, for example, only step S11, the combination of step S11 and step S12, the combination of step S11, step S12, and step S13, the combination of step S11, step S12, and step S14, the combination of all steps (step S11, step S12, step S13, and step S14), etc. can be considered. Hereinafter, as shown in FIG. 5, the case where all steps are combined will be described.

[0025] In the region identification step (step S1) of the present embodiment, first, during the filling of the molten metal 2, a region where the fluctuation of the molten metal pressure becomes large in the cavity 1a is identified (step S11). Here, as a result of the inventors' intensive research on the relationship between the fluctuation of the molten metal pressure and the erosion of the mold, it has been found that when the fluctuation of the molten metal pressure occurs in an arbitrary region within the cavity filled with the molten metal, a physical and chemical load is applied to a part of the mold in contact with the region, and erosion is likely to occur in the mold. Therefore, first, the fluctuation of the molten metal pressure that occurs when erosion occurs in the mold will be described with reference to FIG. 6.

[0026] FIG. 6 is a graph showing an example of the temporal change in the molten metal pressure within the cavity 1a according to the present embodiment. As the molten metal 2 is filled, the molten metal pressure within the cavity 1a rises (in the section from time t0 to t1 in FIG. 6), but then the molten metal pressure decreases (in the section from time t1 to t2 in FIG. 6), and thereafter shows a series of phenomena of rising again (after time t2 in FIG. 6). In the present embodiment, such a phenomenon is regarded as a fluctuation in the molten metal pressure. Further, in the present embodiment, when a fluctuation in the molten metal pressure occurs within the cavity 1a, if the molten metal pressure decreases and then rises again in an arbitrary region within the cavity 1a, the amount of decrease in the molten metal pressure (the difference between the value of the molten metal pressure at time t1 in FIG. 6 and the value of the molten metal pressure at time t2) is defined as the magnitude of the fluctuation in the molten metal pressure. Thus, the fact that erosion is likely to occur in the mold when the magnitude of the fluctuation in the molten metal pressure, which is the amount of decrease in the molten metal pressure when it once decreases and then rises again, is large has been discovered by the present inventor.

[0027] FIG. 7 is a schematic diagram showing the magnitude of the fluctuation in the molten metal pressure in each region within the cavity 1a according to the present embodiment and the distribution in each region. A predetermined threshold value is set for the calculated magnitude of the fluctuation in the molten metal pressure, and a region showing a value exceeding this is identified as a region (R11) where the fluctuation in the molten metal pressure is large. In the cavity 1a according to the present embodiment, the region surrounded by the short dashed line at the upper part of the cavity 1a is identified as the region (R11) where the fluctuation in the molten metal pressure is large.

[0028] In addition, as a method for identifying a region where the fluctuation in the molten metal pressure is large, in addition to the above, a predetermined threshold value can also be set for the frequency of occurrence of the fluctuation in the molten metal pressure (the number of times of up and down movement of the molten metal pressure), and a region showing a value exceeding this can be identified as a region where the fluctuation in the molten metal pressure is large. Also, in addition to the method of setting a threshold value, for example, a region where the fluctuation in the molten metal pressure shows the maximum value can be identified as a region where the fluctuation in the molten metal pressure is large. Furthermore, only the presence or absence of the fluctuation in the molten metal pressure can be grasped, and a region where the fluctuation in the molten metal pressure occurs can be regarded as a region where the fluctuation in the molten metal pressure is large.

[0029] Subsequent to step S11, while filling the molten metal 2 into the cavity 1a, an area where the amount of air entrainment in the cavity 1a increases is specified (step S12). FIG. 8 is a schematic diagram showing the distribution of the amount of air entrainment in the cavity 1a according to the present embodiment. A predetermined threshold value is set for the calculated amount of air entrainment, and an area exceeding this threshold value is specified as an area (R12) where the amount of air entrainment increases. In the cavity 1a according to the present embodiment, the area surrounded by the long dashed line in the upper right part of the cavity 1a is specified as the area (R12) where the amount of air entrainment increases.

[0030] Subsequent to step S12, in the cavity 1a, an area where a filling delay of the molten metal 2 occurs is specified (step S13). FIG. 9 is a schematic diagram showing an area (R13) where a filling delay of the molten metal 2 occurs in the cavity 1a according to the present embodiment. In the cavity 1a according to the present embodiment, the area surrounded by the dashed-dotted line in the upper right part of the cavity 1a and the upper part of the protrusion forming portion 62 is specified as the area (R13) where a filling delay of the molten metal 2 occurs.

[0031] Subsequent to step S13, in the cavity 1a, an area where the flow rate of the molten metal 2 increases is specified (step S14). FIG. 10 is a schematic diagram showing the distribution of the maximum flow rate of the molten metal 2 in the cavity 1a according to the present embodiment. A predetermined threshold value is set for the calculated maximum flow rate, and an area exceeding this threshold value is specified as an area (R14) where the flow rate of the molten metal 2 increases. In the cavity 1a according to the present embodiment, the area surrounded by the two-dot chain line in the lower part of the cavity 1a and in the vicinity of the connection portion with the exhaust gate 1f is specified as the area (R14) where the flow rate of the molten metal 2 increases.

[0032] In addition, as a method for specifying the area where the flow rate of the molten metal 2 increases, in addition to calculating the maximum flow rate described above, for example, the time integral value of the flow rate before and after filling the molten metal 2 in each area in the cavity 1a, or the average flow rate of the molten metal 2 in each area in the cavity 1a is calculated, and a predetermined threshold value is set, whereby the area where the flow rate of the molten metal 2 increases can also be specified.

[0033] By executing the series of steps from step S11 to step S14 as described above, the area identification step (step S1) is completed.

[0034] Subsequently, based on the result obtained from the area identification step (step S1), an area determination step is executed to determine the areas in the mold 1 that are likely to experience erosion in the cavity 1a (step S2). Specifically, as shown in FIG. 11, in this area determination step (step S2), after overlapping the areas (R11, R12, R13, and R14) obtained from each step of the area identification step (step S1), the vicinity of the area where the areas overlap the most is determined as the area in the mold 1 that is likely to experience erosion. Here, FIG. 11 is a diagram showing the overlapping of the areas (R11, R12, R13, and R14) obtained from each step of the area identification step (step S1) in the cavity 1a according to the present embodiment.

[0035] And the result of determining the vicinity of the area where each area (R11, R12, R13, and R14) overlaps the most as the area in the mold 1 that is likely to experience erosion is shown in FIG. 12. Note that FIG. 12 is a diagram showing the vicinity of the area where the areas obtained from each step of the area identification step (step S1) overlap the most in the cavity 1a according to the present embodiment. In the area determination step (step S2) of the present embodiment, as shown in FIG. 12, the area surrounded by the solid line and in contact with the mold 1 is determined as the area (R2) in the mold 1 that is likely to experience erosion.

[0036] Thus, the method for predicting erosion of the mold 1 according to the present embodiment is completed.

[0037] Note that the areas determined to be likely to experience erosion in the mold 1 according to the present embodiment are in good agreement with the results obtained by the inventor through actual casting. As is clear from the above, according to the method for predicting erosion of the mold according to the present invention, it is possible to accurately predict the erosion of the mold that reproduces the actual results.

[0038] As described above, the preferred embodiments of the present invention have been explained. However, the technical scope of the present invention is not limited to the scope described in the above embodiments. Various changes or improvements can be made to the above embodiments.

[0039] For example, in the simulation in this embodiment, a two-dimensional model was used. However, by using a three-dimensional model, more accurate prediction is possible. For example, FIG. 13 is a schematic diagram showing the result of executing the method of the present invention in a mold according to a modified example of this embodiment. The mold according to this modified example is an extension of the two-dimensional model of mold 1 used in the above-described embodiment to a three-dimensional model. In addition, the region specifying step (step S1) in this modified example shown in FIG. 13 is executed including all combinations of steps (step S11, step S12, step S13, and step S14).

[0040] As shown in FIG. 13, in this modified example, by executing the method of the present invention, regions are specified (R110, R120, R130, and R140) in each of steps S11, S12, S13, and S14 included in the region specifying step (step S1), and based on the results, a region (R200) where erosion is likely to occur is determined in the mold according to this modified example.

[0041] Also, in the above-described embodiment, the regions specified in each step of the region specifying step (step S1) were calculated and specified by simulation. However, the present invention is not limited to this method. For example, a method of specifying a region from actual measurement data, or a method of specifying a region by estimating the flow pattern of the molten metal from the structure of the cavity, etc. can be used.

[0042] It is clear from the description of the claims that forms with the above-described changes or improvements added can also be included in the technical scope of the present invention.

Explanation of Reference Numerals

[0043] 1 Mold, 1a Cavity, 1b Gate, 1c Main Runner, 1d Main Gate, 1e Exhaust Runner, 1f Exhaust Gate, 2 Molten Metal, 10 Fixed Mold, 11 Fixed Holder, 12 Fixed Die, 20 Movable Mold, 21 Movable Holder, 22 Movable Die, 30 Sleeve, 31 Plunger Tip, 40 Divider, 50 Overflow, 61 Opening Forming Portion, 62 Projection Forming Portion.

Claims

**Claim 1** A method for predicting erosion of a mold that constitutes a cavity filled with molten metal, a region specifying step of specifying a region in which a predetermined phenomenon occurs within the cavity, a region determination step of determining a region in the mold where erosion is likely to occur based on the result obtained in the region specifying step, which is to be executed, wherein the region specifying step has a first step of specifying a region in which the fluctuation of the molten metal pressure within the cavity becomes large during the filling of the molten metal. The method for predicting erosion of a mold is characterized by this. **Claim 2** The method for predicting erosion of a mold according to Claim 1, wherein the region specifying step includes a second step of specifying a region in which the amount of air entrainment within the cavity becomes large during the filling of the molten metal. The method for predicting erosion of a mold is characterized by this. **Claim 3** The method for predicting erosion of a mold according to Claim 1 or 2, wherein the region specifying step includes a third step of specifying a region in which a filling delay of the molten metal occurs within the cavity. The method for predicting erosion of a mold is characterized by this. **Claim 4** The method for predicting erosion of a mold according to Claim 1 or 2, wherein the region specifying step includes a fourth step of specifying a region in which the flow rate of the molten metal becomes large within the cavity. The method for predicting erosion of a mold is characterized by this.

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