JP2000263211A - Method for designing die for casting, die for casting and casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the design of a casting die which is hardly develop a casting flash in a product by obtaining the residual gas quantity or the gas pressure in the casting when the filling of molten metal is completed, comparing the pressure caused by heat expansion of the residual gas developed in the heat exchange with the casting and the casting pressure and obtaining the opening force of the dies. SOLUTION: The residual gas quantity or the gas pressure in the casting when the filling of the molten metal is completed, is obtd. and the pressure caused by the heat expansion of the residual gas developed in the heat exchange with the casting is represented as a pressure parameter. This pressure parameter and the casting pressure are compared and the die opening force is obtd. from the pressure showing the larger value to design the die. Further, at least the die opening force among the die fastening force, thermal stress and the die opening force, is given to the die or a casting machine containing the die, and the die is designed so that the gap amount on the parting plane between the dies during casting becomes a prescribed value or lower, particularly <=0.05 mm. Further, the die opening force is given to a slide core stopper and the displacing amount is calculated, and the slide core stopper is designed so that the displacing amount becomes the prescribed value or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for designing a casting mold used for die casting of a casting such as an aluminum alloy, and a casting mold.

[0002]

2. Description of the Related Art Die casting is a highly productive casting method capable of casting a large number of cast parts with high accuracy.
Since pressure is applied by the force of Pa, the mold is deformed and a gap is formed in the mold cutting surface, and a phenomenon occurs in which unsolidified molten metal in the mold cavity enters the gap. There is a problem that the molten metal that has entered the gap solidifies, so-called cast burrs are generated in the product, and man-hours for removing the cast burrs of the product are required, thereby hindering productivity. Since it is difficult to take measures against the problem after the mold is manufactured, it is necessary to optimize the shape of the mold at the stage of designing the mold.

[0003] First, the die casting method will be described with reference to the drawings. FIG. 1 shows a schematic view of a die casting die. The molten metal M is poured into the sleeve 1, the plunger tip 2 advances, and the molten metal is filled into the cavity 6 formed by combining the fixed mold 3 and the movable mold 4. Immediately thereafter, the molten metal is pressurized by the plunger tip 2 to several tens of MPa in order to make use of the hot water effect as referred to in gravity casting. This force causes the movable mold 4 supported by the die block 5 to bend into a shape as shown in FIG. 2 with the die block as a fulcrum. At this time, a mold parting surface gap 9 is generated in the parting surface of the mold, which is the end of the cavity formed by the fixed mold 3 and the movable mold 4.

[0004] The relationship between the casting burr and the mold parting surface gap is described in Research Report 454-2 of the Structural Material Center, and on average, the mold parting surface gap does not exceed about 0.05 mm. And that no casting burrs occur. Therefore, if the thickness of the movable mold, the distance between the die blocks, the arrangement, the shape, and the like are designed so that the gap generated on the parting surface of the mold during casting becomes a certain specified value or less, particularly 0.05 mm or less, the casting burr can be reduced. A mold that hardly occurs can be obtained.

Conventionally, the deformation of a mold has been calculated empirically or using a beam bending calculation formula, and a design has been made such that the maximum amount of deflection of the movable main mold when casting pressure acts is about 0.05 mm. .

[0006]

However, in recent years, the size of the mold has been increased, and since there is no experience in designing such a mold, the optimum shape of the mold without casting burrs is not known, and the mold with the casting burrs is not formed. There have been problems such as the production of a mold, the use of an equation for calculating the deflection of a beam, the use of a large mold, and the occurrence of casting burrs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and a new casting method in which casting burrs are less likely to occur in products even if the casting mold has a new shape and size. An object of the present invention is to provide a method of designing a metal mold and a metal mold for casting.

[0008]

In order to achieve the above object, a method for designing a casting mold according to the present invention is directed to a casting mold having a movable mold and a fixed mold, which is used when casting of a molten metal is completed. Determine the amount or pressure of the residual gas inside, express the pressure due to the thermal expansion of the residual gas generated by heat exchange with the casting with the pressure parameter A, compare the pressure parameter A with the casting pressure, and calculate the pressure from the one showing the larger value. Find the mold opening force,
Design the mold. In the present invention, "casting pressure" refers to the pressure applied after filling the cavity in the mold with the molten metal, and "mold opening force" refers to opening the mold combined during casting, that is, the mold. The force acting in the direction to increase the clearance between the mold parting surfaces.

Further, at least the mold opening force of the mold clamping force, the thermal stress and the mold opening force is given to the mold or a casting machine including the mold to calculate the gap amount at the mold cutting surface, and the mold during casting is subjected to the molding. It is advisable to design the casting mold so that the gap between the mold parting faces is less than a predetermined value, especially less than 0.05 mm. In the case of a casting mold having a slide core and a slide core stopper, at least the mold opening force of the mold clamping force, thermal stress and mold opening force is given to the slide core stopper, and It is preferable to calculate the displacement amount and design the shape of the slide core stopper so that the displacement amount of the slide core stopper is equal to or less than a predetermined value, particularly, 0.05 mm or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have experimentally investigated the factors that determine the parting surface gap of a mold during casting using the mold shown in FIG. 3 and calculated the parting surface clearance of the mold. The method was examined. FIG. 3 shows a state where the fixed mold 3 is seen when the movable mold 4 is opened in the mold shown in FIG. The fixed mold 3 has a shunt 20 connected to the sleeve 1, and the molten metal is connected to the shunt 20.
From the cavity 6 through the runner 21.
The fixed die 3 is provided with a gap measurement sensor for the parting surface at the mold parting surface measurement position 10, a casting pressure sensor at the casting pressure measurement position 11, and a temperature sensor at the temperature measurement position 12.
An air vent 13 is also provided on the parting surface. The operating side and the non-operating side of the fixed mold 3 are referred to as a side that performs an operation such as taking out a product when casting a product with the fixed mold 3, and an opposite side with the fixed mold 3 interposed therebetween is an opposite operating side. That.

Using the present mold, the present inventors have studied the factors that create or enlarge the gap between the mold parting surfaces during casting. As a result, the factors that cause or enlarge the gap between the mold parting surfaces during casting are the residual gas in the casting, the casting pressure (the pressure applied after filling the melt in the cavity in the mold), and the mold. It was found that it was a fastening force and a thermal stress. Furthermore, among those factors, especially when comparing the casting pressure and the pressure caused by the thermal expansion of the residual gas, there is a difference in the time when the peak value is obtained. Open the combined mold during casting, that is, find the "mold opening force" which is a force acting in the direction of increasing the gap between the mold parting surfaces, and determine the mold opening force and, if necessary, the mold clamping force and heat. It was found that by applying the stress to the mold or the casting machine including the mold and calculating the gap generated in the mold parting plane, the gap can be approximated to the actual gap in the mold parting plane during casting. The amount of residual gas in the casting is
The gas pressure was measured by gas analysis, and the gas pressure was measured by a pressure sensor provided at the tip of the air vent 13. As a method of comparing the pressure parameter A with the casting pressure and obtaining the mold opening force from the pressure indicating the larger value, there are cases where the pressure receiving area is simply multiplied by the pressure indicating the larger value, and 1.5 or the like. In some cases, the mold opening force is multiplied by a safety factor.

FIG. 4 shows the amount of a gap generated on the parting surface of the die when the injection speed of the plunger tip is 1.0 m / s (residual gas pressure in the casting is 0.13 MPa). The gap amount at 0 m / s (residual gas pressure in the casting: 0.15 MPa) is shown. In any case, the casting pressure is 70MPa
And the boosting time is 0.05 seconds. In the former case, the gap between the mold parting surfaces is at the completion of the increase of the casting pressure (0.05
In the latter case, the gap amount shows the maximum value at the time when the pressure generated by the thermal expansion of the residual gas becomes maximum (about 0.2 seconds).

Accordingly, the residual gas amount or pressure in the casting at the time of completion of filling is determined, and the pressure due to the thermal expansion of the residual gas generated by heat exchange with the casting is expressed by the pressure parameter A, and the pressure parameter A is compared with the casting pressure. Then, the larger one is given to the mold or the casting machine including the mold as the mold opening force, and if necessary, the mold clamping force and the thermal stress are also given to calculate the amount of the parting surface gap of the mold, The amount of clearance on the parting surface is below the specified value,
In particular, if the thickness of the movable mold, the distance between the die blocks, the arrangement, the shape, and the like are designed to be 0.05 mm or less, a mold in which casting burrs are unlikely to occur can be obtained. In particular, if the amount of gap or displacement of the die cutting surface is set to a specified value, especially about 0.05 mm, a light-weight die can be obtained within a range where casting burrs are unlikely to occur.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which the mold design method of the present invention is applied to an aluminum die casting mold will be described below. First, Itamura and Yamamoto's gas pressure analysis formula (Casting Engineering 68 (1996) 4)
99) Alternatively, the residual gas pressure in the casting at the time of completion of the filling of the molten metal is obtained using molten metal flow analysis software capable of calculating the back pressure. The gas remaining in the casting is pressurized by the plunger tip and crushed until the gas pressure becomes equivalent to the casting pressure. The heat of the molten metal is transmitted to the gas, and the gas thermally expands. Such pressure acts as a mold opening force without loss when the gate and the mold parting surface are closed. However, in practice, pressure loss is considered because the gate is not solidified, or gas escapes from the initial gap on the parting surface inevitably generated during mold production.In addition, when casting pressure is transmitted to the molten metal, Since it is difficult to evaluate the gas volume when the gas is compressed because it differs depending on the ratio of the solid phase ratio, it is difficult to correctly evaluate the pressure due to the thermal expansion force of the residual gas.

Therefore, the following equation is introduced as an equation for giving the pressure A due to the thermal expansion of the residual gas as the pressure parameter A. That is, A = k ｛a (p−0.101)
3) Let｝ b (MPa), and coefficients k, a, and b are determined by experiments and the like. p is the residual gas pressure immediately after filling the molten metal. The pressure parameter A may be determined by assuming an equation such as the above equation using the gas amount instead of the residual gas pressure. As described above, the pressure parameter A is introduced, the A is compared with the casting pressure, and a value obtained by multiplying the pressure showing a large value by the pressure receiving area is defined as the mold opening force, and the mold opening force is obtained. Here, even when the pressure obtained by measuring the pressure acting on the molten metal with a pressure sensor similar to the molten metal pressure sensor described in the Research Report 454-2, is used as the casting pressure, Although the machine setting value may be used, a more accurate calculation result is obtained by using the former value.

Next, the mold temperature distribution is determined by solidification analysis software or the like, and the temperature distribution is input to the mold model of the structural analysis software by the conversion software. A mold clamping force is applied to the bottom of the die block on the die plate side of the cavity to simulate deformation of the mold during casting. The model for structural analysis is a solid model with a movable mold with a die block, a contact surface is formed on the mold parting surface, and a fixed mold with the die plate side fixed on the opposite surface is arranged as shown in FIG. Mold model.

FIG. 6 compares the mold parting surface gap measured with the mold shown in FIG. 3 and the gap amount obtained by the above calculation method for the mold. When the filling of the molten metal is completed, the gas pressure in the casting is (A)
The measured gap amount and the calculated gap amount are in good agreement both in the case of 0.13 MPa in the case of the casting and the case where the gas pressure in the casting is 0.15 MPa in the case (B). In this case, the casting pressure is 70 M directly measured by the molten metal pressure sensor.
Pa, k = 0.6, a
= 100, b = 4. Therefore, the mold parting surface gap is calculated by the above calculation method, and the mold parting surface gap is set to 0.05
mm, the thickness of the mold, the distance between the die blocks,
If the mold is manufactured by designing the position and the shape, etc., a mold in which casting burrs hardly occur can be obtained.

FIG. 7 shows the amount of displacement from the original position of the movable mold surface (the position where no force is applied) when a casting pressure and a mold clamping force are applied to the movable mold. In the case where the deformation of the parting surface when the mold clamping force is applied is thus small, the amount of deformation (partition surface gap amount) may be calculated by excluding the mold clamping force and applying the mold opening force to the mold.

FIG. 8 shows an example of the relationship between the gap of the parting surface of the movable mold, the thickness of the mold, and the distance between the die blocks. At the time of designing, from such a figure, it is possible to design a mold in which casting burrs are less likely to occur by selecting a mold thickness that results in a gap amount of 0.05 mm and a distance 8 between die blocks. Die block distance 8
Is reduced as much as possible, and a mold having a gap of 0.05 mm is selected, so that a mold having less cast burr and light weight can be obtained.

FIG. 9 shows an example in which a thermal stress is applied to the movable mold to simulate thermal deformation. Figure 2 illustrates a movable half that is symmetric. When such thermal deformation is large, it is necessary to calculate the amount of gap of the parting surface by giving the mold opening force, the mold clamping force and the thermal stress to the mold.

A method of calculating the deformation of the slide core stopper during casting will be described with reference to FIG. That is,
The mold opening force determined by the method of the present invention acts on the surface of the slide core 17 in contact with the cavity 6, and the mold opening force of the slide core stopper 19 that presses the slide core through the slide core acts. FIG. 11 shows a result of calculating the deformation of the stopper by applying the mold opening force to the force receiving surface of the slide core stopper. If the amount of displacement of the stopper is 0.05 mm or less, it is possible to suppress the occurrence of casting burrs on the slide core.

[0022]

According to the present invention, by designing and manufacturing a mold by the method for designing a casting mold according to the present invention, it is possible to obtain a mold in which casting burrs hardly occur. Further, when the gap amount or displacement amount of the mold parting surface is set to a specified value, particularly about 0.05 mm, a lightweight mold can be obtained within a range in which casting burrs are unlikely to occur.

[Brief description of the drawings]

FIG. 1 is a schematic view of a die casting mold.

FIG. 2 is an explanatory view showing a state of deformation of a die casting mold due to casting pressure.

FIG. 3 is an explanatory view of an experimental mold in which a die parting surface gap and a casting pressure are measured.

FIG. 4 is a view showing a measurement result of a mold parting surface gap when a residual gas pressure in a casting is 0.13 MPa.

FIG. 5 is a view showing a result of measuring a gap between a die cut surface when a residual gas pressure in a casting is 0.15 MPa.

FIG. 6 is a diagram comparing a measured value and a calculated value of a mold parting surface gap.

FIG. 7 is an explanatory diagram showing a calculation example of a displacement amount of a portion from the side end of the movable die to the center of the cavity when a casting pressure and a mold clamping force are applied to the movable die.

FIG. 8 is an explanatory diagram showing an example of a relationship between a mold parting surface gap, a mold thickness, and a distance between die blocks.

FIG. 9 is an explanatory diagram showing an example in which a thermal stress is applied to the movable mold to calculate a deformation amount of the movable mold.

FIG. 10 is an explanatory diagram showing an example of the relationship between a slide core and a slide core stopper.

FIG. 11 gives a mold opening force to the slide core stopper,
It is explanatory drawing which shows the example which computed the deformation of the slide core stopper.

[Explanation of symbols]

1 sleeve, 2 plunger tip, 3 fixed type,
4 movable type, 5 die block, 6 cavity, M
Molten metal, 7 Mold cutting surface, 8 Distance between die blocks, 9
Mold parting surface gap, 10 Mold parting surface gap measurement position, 1
1 Casting pressure measurement position, 12 Mold temperature measurement position, 13
Air vent, 14 fixed main type, 15 movable main type, 16
Nesting, 17 slide cores, 18 hydraulic cylinders,
19 Slide core stopper, 20 shunts, 21 Runner

Claims (6)

[Claims] In a casting mold having a movable mold and a fixed mold, an amount or pressure of a residual gas in a casting at the time of completion of filling a molten metal is determined, and a pressure due to a thermal expansion of the residual gas generated by heat exchange with the casting is determined. A method for designing a casting mold, characterized by expressing the parameter A, comparing the pressure parameter A with the casting pressure, determining the mold opening force from the pressure showing the larger value, and designing the mold. 2. The method for designing a casting mold according to claim 1, wherein at least the mold opening force of the mold clamping force, the thermal stress and the mold opening force is given to the mold or a casting machine including the mold. A method of calculating a mold parting surface gap amount, and designing a casting mold so that a gap of the mold parting surface during casting is equal to or less than a predetermined value. 3. The method for designing a casting mold according to claim 2, wherein the casting mold is designed so that the gap between the mold parting faces is 0.05 mm or less. 4. The method for designing a casting mold according to claim 1, wherein in the case of a casting mold having a slide core and a slide core stopper, the mold clamping force, the thermal stress, and the mold opening force. By applying at least the mold opening force to the slide core stopper, calculating the displacement of the slide core stopper, and designing the shape of the slide core stopper so that the displacement of the slide core stopper is equal to or less than a predetermined value. A method for designing a casting mold. 5. The displacement amount of the slide core stopper is set to 0.0
The method for designing a casting mold according to claim 4, wherein the shape of the slide core stopper is designed to be 5 mm or less. 6. A casting mold designed by the method for designing a casting mold according to any one of claims 1 to 5.