CN114599465A - Aluminum casting method and mold - Google Patents

Abstract

An aluminum casting method for pouring a molten aluminum (12) pumped up by an electromagnetic pump (20) into a mold (50), wherein the thickness of a powder mold release agent applied to the mold (50) is set to be thinner than the thickness of the mold release agent in a gravity mold casting method, that is, the temperature of the mold before pouring is controlled to be in the range of 110 to 250 ℃, and the temperature of the molten aluminum at the time of pouring is controlled to be a value obtained by adding 20 to 55 ℃ to the liquidus temperature of aluminum.

Description

Aluminum casting method and mold

Technical Field

The present invention relates to an aluminum casting method and a mold used in the aluminum casting method.

Background

An aluminum alloy (hereinafter, referred to as aluminum) is melted, and the obtained melt is poured into a mold, thereby obtaining an aluminum product.

As an aluminum product, a knuckle is known as one of vehicle parts. The extending portion of the knuckle extends radially with the axle portion as a center. The knuckle is a complex shaped component.

A technique for manufacturing a knuckle by a gravity die casting method has been proposed (for example, see patent document 1).

In the gravity die casting method disclosed in patent document 1, a melt is poured from a gate opening upward. The melt flows down along the pouring gate under the action of gravity, and the flow direction is changed into horizontal. The melt with changed direction flows through the cavity on one side, the cavity on the axle part and the cavity on the other side in sequence to fill all the cavities.

Further, a mold for casting a knuckle has been proposed (for example, see patent document 2 (fig. 6)).

The technique disclosed in patent document 2 is described with reference to fig. 15 (plan view).

As shown in fig. 15, the mold 100 has a central cavity 101 forming an axle portion, a first cavity 102 extending from the central cavity 101 to one side, and a second cavity 103 extending from the central cavity 101 to the other side.

Further, the mold 100 has a gate 104 and a runner 105. The runner 105 functions to connect the gate 104 and the first cavity 102.

The melt flows through the gate 104, the runner 105, the first chamber 102, the central chamber 101, and the second chamber 103 in this order.

The techniques disclosed in patent documents 1 and 2 are called gravity die casting. The gravity die casting method is particularly low in pressure of the melt as compared with a high-pressure casting method typified by a die casting method. Since the pressure of the melt is low, the mold does not need to be made strong and the casting apparatus does not need to be made strong in the gravity mold casting method. Therefore, the gravity die casting method is widely used for practical use.

In contrast, in the gravity die casting method, there are disadvantages described below.

The flow rate of the melt is low because it depends on gravity. Thus, if the temperature of the mold is too low, the melt solidifies before reaching the end of the cavity.

As a countermeasure, the temperature of the melt is increased. Empirically, the value obtained by adding 100 ℃ to the liquidus temperature of the melt is used as the melt temperature.

By setting the liquidus temperature plus the temperature of 100 c, unfavorable solidification can be eliminated.

After casting, the melt is cooled and solidified, but since the temperature of the mold is high, it takes a long time until solidification. If it takes a long time to solidify, the production time is prolonged, and the productivity is lowered.

In the case of high-pressure casting such as die casting, the flow rate of the melt is high, and the productivity is not lowered. However, the mold and the casting apparatus are expensive and cannot be used.

In the case where improvement in productivity is required, a casting method capable of improving productivity without increasing the melt pressure is desired.

Next, the mold 100 was examined.

In fig. 15, the melt flows through the gate 104 → the runner 105 → the first chamber 102 → the central chamber 101 → the second chamber 103.

Since the distance from the gate 104 to the tip end (upper right corner in the drawing) of the second cavity 103 is long, the pouring time becomes long. If the pouring time is long, the casting time becomes long, and productivity is lowered.

In addition, in order to reach the end of the second chamber 103, the melt temperature needs to be increased. This is because, if the melt temperature is too low, the melt solidifies and cannot flow to the end.

However, if the melt temperature is high, the solidification time becomes long, and the productivity is lowered.

In the case where an increase in productivity is required, it is desirable to shorten the distance from the gate to the end of the second cavity.

In order to cope with this requirement, the present inventors have studied to move the gate 104 to an intermediate position between the first cavity 102 and the second cavity 103. This is because the distance from the gate 104 to the end of the second cavity 103 becomes about half. The contents of this study will be described in detail with reference to fig. 16 and 17.

As shown in fig. 16, the conventional knuckle casting 110 is composed of a center portion 112 having a spindle hole 111, a first projecting portion 113 projecting from the center portion 112, a second projecting portion 114 projecting from the center portion 112, and a third projecting portion 115 projecting from the center portion 112.

As shown in fig. 17, a mold 120 for casting the knuckle casting 110 having such a shape includes a central cavity 121, a first cavity 122, a second cavity 123, and a pillar portion 124 protruding to provide the axle hole 111, and includes a gate 125 and a runner 126 on a bottom surface.

The distance from the gate 125 to the end of the second cavity 123 becomes short, the casting time can be shortened, and the productivity can be improved.

The melt 127 flowing through the gate 126 collides with a flat top surface 128 of the pillar portion 124. Then, the flow direction is bent 90 ° to the left or right. I.e. the flow direction changes sharply. The flow of the melt 127 is disturbed due to the collision and the abrupt change in the flow direction. Due to this disturbance, casting defects such as gas entrainment may occur.

Even if the productivity could be increased, casting defects are unacceptable.

Therefore, a mold capable of shortening the distance from the gate to the end of the second cavity without accompanying casting defects is desired.

Documents of the prior art

Patent document

Japanese patent application laid-open No. 2014-76450 in patent document 1

Japanese patent laid-open No. 2012-143788 of patent document 2

Disclosure of Invention

Problems to be solved by the invention

The present invention addresses the problem of providing a casting method that can improve productivity without increasing the pressure of a molten metal, and a mold used in the casting method.

Means for solving the problems

The invention according to claim 1 is an aluminum casting method in which a molten aluminum drawn by an electromagnetic pump is poured into a mold, wherein a thickness of a powder mold release agent applied to the mold is set to be thinner than a thickness of a mold release agent in a gravity mold casting method, that is, a temperature of the mold before pouring is controlled to be in a range of 110 to 250 ℃, and a temperature of the molten aluminum during pouring is controlled to be a value obtained by adding 20 to 55 ℃ to a liquidus temperature of the aluminum.

The invention of claim 2 is preferably a mold that can be used in the aluminum casting method of claim 1, and that is a mold for casting a casting having a central portion, a first projecting portion projecting from the central portion, and a second projecting portion projecting from the central portion in a direction different from that of the first projecting portion, the mold including: a gate provided on a bottom surface, a main runner rising from the gate, a first runner branching from the main runner, a first cavity forming the first projecting portion from a melt supplied through the first runner, a second runner branching from the main runner, and a second cavity forming the second projecting portion from a melt supplied through the second runner, wherein a conical portion projecting toward the main runner is provided at an outlet of the main runner, and the melt passing through the main runner is branched to the first runner and the second runner along a conical surface of the conical portion.

The invention of claim 3 is preferably the mold of claim 2, wherein the casting is a knuckle, the central portion is a spindle portion having a spindle hole, the mold further includes a pillar portion forming the spindle hole, and the conical portion is provided at a front end of the pillar portion.

The invention of claim 4 is preferably the mold used in the aluminum casting method according to claim 1, wherein the mold includes an exhaust part for exhausting gas accumulated in the cavity, and the exhaust part is provided with a vent hole having a size of 30 to 80 μm.

The invention of claim 5 is preferably the mold of claim 4, wherein the exhaust part is a cylinder fitted into the mold, the cylinder having a bottom facing the cavity, and the vent hole being provided in the bottom.

The invention according to claim 6 is preferably the mold according to claim 5, wherein the vent hole is a slit having a width of 30 μm to 80 μm.

The invention according to claim 7 is preferably the mold according to claim 6, wherein the slits are provided in the bottom so that 2 or more slits are parallel to each other.

The invention according to claim 8 is preferably the mold according to claim 5, wherein the cylinder doubles as a product ejector pin for separating the casting from the mold.

ADVANTAGEOUS EFFECTS OF INVENTION

In the invention according to claim 1, the molten metal is pumped up by an electromagnetic pump. A slight pressure fluctuation is applied to the melt by the electromagnetic pump, and the fluidity of the melt is increased by the pressure fluctuation. According to the method of the present invention, since the fluidity of the melt is greatly improved as compared with the fluidity of the melt in the gravity die casting method, the temperature of the melt can be lowered as compared with the gravity die casting.

In addition, according to the method of the present invention, since the fluidity is greatly improved as compared with the fluidity of the melt in the low-pressure die casting method, the temperature of the die can also be reduced.

In addition, according to the method of the present invention, since the mold release agent is thin, the heat of the melt is rapidly transferred to the mold, and the solidification time is shortened.

From the above, the melt of the present invention completes solidification in an exceptionally short time as compared with the gravity die casting method. Since the casting time is shortened, productivity is improved.

That is, according to the present invention, a casting method capable of improving productivity without increasing the melt pressure is provided.

Further, according to the present invention, since the melt solidifies in a short time, the solidification structure is refined. By this refinement, the mechanical strength of the casting can be improved.

In the invention according to claim 2, a conical portion is provided at the outlet of the main runner, and the molten metal is divided into the first runner and the second runner along the conical surface of the conical portion. The change of the flow of the melt is smooth. This can suppress the occurrence of casting defects.

In addition, since the gate and the main runner are provided between the first cavity and the second cavity, the distance from the gate to the end of the second cavity becomes short.

Therefore, according to the present invention, there is provided a mold capable of shortening the distance from the gate to the end of the second cavity without accompanying casting defects.

In the invention according to claim 3, the casting is a knuckle, the central portion is a spindle portion having a spindle hole, the mold further includes a pillar portion forming the spindle hole, and the conical portion is provided at a front end of the pillar portion.

In the case of a knuckle, an axle hole is necessary. Since the conical portion is provided at the pillar portion where the axle hole is formed, the conical portion can be easily projected toward the main runner, and the manufacturing cost of the mold can be suppressed.

In the invention according to claim 4, a mold into which the molten aluminum pumped up by the electromagnetic pump is poured is provided with an exhaust portion, and the exhaust portion is provided with a vent hole having a size of 30 μm to 80 μm. If the particle size is 30 μm to 80 μm, the problem of burrs is eliminated and the air release property is ensured.

Therefore, according to the present invention, there is provided a mold in which, when a molten aluminum is poured by an electromagnetic pump, the molten aluminum does not enter a gap for evacuation.

In the invention according to claim 5, the exhaust unit is a cylinder fitted into the mold, and a vent hole is provided in a bottom of the cylinder.

Since the mold is large and heavy, it is not easy to directly set a gap on the mold. In contrast, in the present invention, the clearance is provided in the cylinder body that is separate from the mold. Since the cylindrical body is small and lightweight, the gap formation processing is facilitated.

In the invention according to claim 6, the vent hole is a slit. The slit is oblong, and therefore the opening area can be obtained. In addition, the slits can be easily formed by a wire electric discharge machine.

In the invention according to claim 7, since two or more slits are provided, the opening area is increased, and the air discharge performance is improved.

In the invention of claim 8, the cylinder doubles as a product ejector pin. The cylinder exerts a gas exhaust function and a product push-out function, so that the added value is improved.

Drawings

FIG. 1 is a schematic view of a casting apparatus for carrying out the aluminum casting method of the present invention.

Fig. 2 is a cross-sectional view of the electromagnetic pump.

Fig. 3 is an enlarged view of a portion 3 of fig. 2.

Fig. 4(a) is a front view of the casting, and (b) is a perspective view of the knuckle casting.

Fig. 5 is a sectional view of the mold, which is a sectional view corresponding to the section taken along line 5-5 in fig. 4 (b).

Fig. 6 is a diagram illustrating the temperature range and the casting time of the mold in the comparative example.

Fig. 7 is a diagram illustrating the temperature range and casting time of the mold in the example.

FIG. 8 is a cross-sectional view of the knuckle casting just after demolding.

FIG. 9 is an exploded view of the knuckle casting.

Fig. 10 is a main part sectional view of the movable mold.

Fig. 11 is a sectional view of the exhaust portion.

Fig. 12 is a bottom view of the exhaust unit.

Fig. 13 is a view illustrating a modification of the exhaust unit, where (a) is a view showing radial vent holes, and (b) is a view showing fine circular holes.

Fig. 14 is a diagram illustrating the barrel also functioning as a product ejector pin.

Fig. 15 is a plan view of a conventional mold.

Fig. 16 is a sectional view of a conventional knuckle casting.

Fig. 17 is a sectional view of a mold corresponding to a conventional knuckle casting.

Detailed Description

Embodiments of the present invention will be described based on the drawings.

Examples

As shown in fig. 1, the holding furnace 10 is a furnace that is provided with a heater 11 and stores a molten aluminum 12. The holding furnace 10 is provided with an electromagnetic pump 20. The electromagnetic pump 20 is controlled by the control unit 32.

The melt 12 is heated or kept at a temperature equal to or higher than the melting point by the heater 11, and the temperature thereof is controlled by the temperature control section 66.

In this example, a steel frame 13 is mounted on the holding furnace 10, and the electromagnetic pump 20 is supported by the steel frame 13. However, the holding furnace 10 may be provided with the electromagnetic pump 20 in any manner.

The holding furnace 10 is a facility for holding the temperature of the melt 12 at a predetermined value. The holding furnace 10 is not limited to a holding furnace in a narrow sense as long as it is a vessel for storing aluminum in a molten state, such as a melting furnace, a tapping furnace, and a ladle (ladle).

The detailed configuration of the electromagnetic pump 20 will be described based on fig. 2.

As shown in fig. 2, the electromagnetic pump 20 includes: a base flange 21, a liquid guide tube 22 vertically extending through the base flange 21, a core member 23 housed in the liquid guide tube 22, a lower coil 24 surrounding a lower portion of the liquid guide tube 22, a lower case 25 surrounding the lower coil 24 and suspended from the base flange 21, an upper coil 26 surrounding an upper portion of the liquid guide tube 22, an upper case 27 surrounding the upper coil 26 and mounted on the base flange 21, a discharge tube 28 upwardly extending from the liquid guide tube 22, and a liquid level meter 29 surrounding the discharge tube 28.

When the lower coil 24 is energized, the melt (fig. 1, symbol 12) is lifted according to fleming's left-hand rule.

When the upper coil 26 is energized and the lower coil 24 is not energized, the melt is lifted up to the level gauge 29. The liquid level of the liquid level gauge 29 is a "standby liquid level".

These controls are performed by a control unit (fig. 1, reference numeral 32).

According to fleming's left hand rule, if the current is increased, the force increases.

When the current of the upper coil 26 is further increased, the melt exceeds the level gauge 29 and is discharged upward from the discharge pipe 28. Then, the molten metal is poured into the mold 50 through the liquid guide block 14 shown in fig. 1.

Therefore, the electromagnetic pump 20 is a pressure casting unit that draws the melt 12 stored in the holding furnace 10 and supplies the drawn melt to the mold 50.

The mold 50 includes a heater and a water passage, and the temperature of each part of the mold 50 is constantly measured by the temperature control unit 66, and temperature control is performed so that the measured value becomes a predetermined temperature. By this temperature control, the temperature of the mold 50 immediately before casting is maintained at an appropriate temperature.

The electromagnetic pump 20 as the pressure casting means has a pressure phenomenon peculiar to the electromagnetic action, and the present inventors have focused on this phenomenon. This phenomenon will be described with reference to fig. 3.

As shown in fig. 3, the melt 12 flows upward in the passage between the liquid guiding tube 22 and the core member 23. The magnetic field 31 reaching the core member 23 from the upper end 26a of the upper coil 26 has a curved shape protruding upward. The degree of this bending may vary. If the frequency of the power supply is 50Hz, the degree of bending varies by a factor of 2 of 100 Hz.

The pressure (discharge pressure) of the melt 12 varies slightly at a small frequency (100Hz) due to the variation (displacement) of the magnetic field 31. That is, minute pulsation is inevitably generated in the melt 12.

Next, the form of the casting 35 will be explained.

As shown in fig. 4(a), the casting 35 has a central portion 36, a first projecting portion 42 projecting from the central portion 36, and a second projecting portion 43 projecting from the central portion 36 in a direction different from that of the first projecting portion 42. The purpose of the casting 35 is arbitrary, and is, for example, a knuckle casting as one of vehicle parts.

As shown in fig. 4(b), the knuckle casting 40 as the casting 35 includes a spindle portion 41 corresponding to the central portion 36, a first projecting portion 42 projecting largely from the spindle portion 41, a second projecting portion 43 projecting from the spindle portion 41 to the opposite side, and a third projecting portion 44 projecting inwardly from the spindle portion 41. The axle portion 41 has an axle hole 45 at the center.

A mold 50 suitable for casting the knuckle casting 40 of this form will be described with reference to fig. 5.

As shown in fig. 5, the mold 50 is composed of a fixed mold 51 and a movable mold 52.

The movable die 52 is provided with a first cavity 53 in which a first projecting portion (fig. 4 b, reference numeral 42) is formed, a second cavity 54 in which a second projecting portion (fig. 4 b, reference numeral 43) is formed, and a third cavity 55 in which a third projecting portion (fig. 4 b, reference numeral 44) is formed.

The movable die 52 is provided with a pillar portion 56 forming a spindle hole (fig. 4(b) and reference numeral 45). The column portion 56 is a tapered cylinder, extends to the fixed die 51 so as to penetrate the first to third cavities 53 to 55, and has a tapered portion 57 at the tip thereof.

The fixed die 51 includes a gate 58 on a lower surface thereof, a main runner 59 extending upward from the gate 58, and a first runner 61, a second runner 62, and a third runner 63 branching off from the conical portion 57 and extending along the conical portion 57. For ease of illustration, the third runner 63 passes inside and in front of the conical section 57.

The first gate 61 is connected to the first chamber 53, the second gate 62 is connected to the second chamber 54, and the third gate 63 is connected to the third chamber 55.

The conical portion 57 is provided at an outlet of the main runner 59 so as to protrude toward the main runner 59.

Therefore, the melt 12 flowing from the gate 58 to the main runner 59 is divided at the apex 57a of the conical portion 57 and flows along the conical surface 57 b. Therefore, the melt 12 flowing through the first gate 61, the second gate 62, and the third gate 63 smoothly flows without disturbance.

In the figure, 64 is a boundary line between the product portion and the non-product portion, and the boundary line 64 is a line passing through a boundary between the conical portion 57 and the pillar portion 56.

Next, a description will be given of a melt poured into a mold (fig. 6a, 130) or a mold (fig. 7, 50) by comparing a conventional technique (gravity mold casting method) with the present invention (casting method using an electromagnetic pump).

In the gravity die casting method, the temperature of the die before casting (which varies depending on the location) is controlled to be in the range of 240 to 360 ℃. Further, the mold is coated with the release agent described in fig. 6 (b).

As shown in fig. 6(a), the molten metal is poured from a gate 131 provided at a high position of the mold 130. The melt fills the cavity 133 through the downwardly inclined runner 132.

As shown in fig. 6(b), the thickness ta of the release agent 134 was empirically set to 150 μm.

The release agent 134 is applied to the mold 120, for example, by dissolving graphite or ceramic in a solvent and applying it to the mold 120 with a spray gun or a brush.

As shown in fig. 6(c), the casting time under this condition was 80 seconds.

As described in fig. 3, the use of the electromagnetic pump increases the fluidity of the melt. From this finding, the present inventors found that the melt can be made to flow to the end of the cavity even if the melt temperature is lowered. Further, if the melt temperature is lowered, the mold temperature immediately before casting can be lowered.

Further, when the melt temperature is lowered, thermal damage to the mold is reduced, and therefore the mold release agent can be made thin. Further, since the melt has high fluidity and thermal damage to the mold can be reduced, the mold release agent can be made thin.

Based on the above findings, the present invention has been made. The details of the present invention will be described with reference to fig. 7(a) to (c).

In the casting method using an electromagnetic pump, the temperature of the mold before casting (which varies depending on the location) is controlled to be 120 to 240 ℃. Even in this case, the melt flows to the end of the cavity without solidifying. Further, a mold release agent shown in fig. 7(b) was applied to the mold.

As shown in fig. 7(a), in the embodiment, the mold 50 is poured using the electromagnetic pump 20.

As shown in fig. 7(b), a powder release agent 65 is used as the release agent. The powder releasing agent 65 is applied by electrostatic coating to blow powder toward the die 50.

The powder release agent 65 is composed of, for example, powder containing diatomaceous earth as a main component. Diatomaceous earth has innumerable minute gaps inside, and air is enclosed in the gaps, and therefore, diatomaceous earth is rich in heat insulation performance. Even if the thickness is thin, heat transfer from the melt to the mold 50 can be satisfactorily blocked.

The electrostatic coating improves the adhesion of the coating material during coating. When the sprayed material is powder, the powder is aligned on the surface of the die 50. It is expected that the mold release performance can be sufficiently maintained even if it is thin as compared with the conventional mold release agent. Therefore, in the present invention, the thickness Tb of the powder mold release agent 65 is set to 20 μm.

As shown in fig. 7 c, the melt temperature is lowered by 10 ℃ to 700 ℃, and the mold temperature immediately before casting (temperature difference depending on the part) is set to 120 to 240 ℃, and casting is performed on the mold 50. The casting time under this condition was 45 seconds.

Since the thickness Tb of the powder mold release agent 65 is small, heat transfer from the melt to the mold 50 is strong, and it is expected that the casting time can be greatly shortened.

Therefore, the present inventors performed the following experiments. In the experiment, it was attempted to lower the melt temperature, with the melt rotating to the end of the chamber as a premise.

(1) The experimental conditions are as follows:

(1-1) casting method: gravity die casting or casting using electromagnetic pump

(1-2) thickness of mold release agent: 150 μm or 20 μm (powder)

(1-3) melt: AC4CH (aluminium alloy) with liquidus temperature of 615 DEG C

(1-4) melt temperature: 710 deg.C, 700 deg.C, 680 deg.C, 670 deg.C, 660 deg.C or 635 deg.C

(1-5) items measured in the experiment: casting time

Experiment 01: in the gravity die casting method, a mold was coated with a release agent of 150 μm, and the melt temperature was set to 710 ℃, so that the casting time was 80 seconds as described in fig. 6 (c).

Experiment 02: the melt temperature was lowered to 700 ℃ under the same conditions as in experiment 01. The casting time was 60 seconds.

Experiment 03: by the casting method using an electromagnetic pump, a 20 μm powder mold release agent was electrostatically coated in a mold, and the casting time was 45 seconds as illustrated in fig. 7(c) with the melt temperature set at 700 ℃.

Experiment 04: the melt temperature was lowered to 680 ℃ under the same conditions as in experiment 03. The casting time was 41 seconds.

Experiment 05: the melt temperature was lowered to 670 ℃ under the same conditions as in experiment 03. The casting time was 39 seconds.

Experiment 06: the temperature of the melt was lowered to 660 ℃ under the same conditions as in experiment 03. The casting time was 37 seconds.

Experiment 07: the melt temperature was lowered to 635 ℃ and the other conditions were the same as in experiment 03. The casting time was 32 seconds.

(2) The experimental results are as follows:

in the prior art (experiments 01 and 02), the casting time is 60 to 80 seconds, and in the technique of the present invention (experiments 03 to 07), the casting time is 32 to 45 seconds, and the casting time is approximately half.

(3) Mechanical test:

a test piece cut out from the casting obtained in experiment 01 was designated as "test piece 1", and the mechanical properties were examined. Further, a test piece cut out from the casting obtained in experiment 07 was used as "test piece 2" to examine mechanical properties.

(3-1) mechanical properties of test piece 1:

2 dendrite arm spacing: 25 to 35 μm

Tensile strength: 290MPa of pressure

0.2% yield strength: 210MPa

Elongation at break: 13.7 percent

·10⁷Secondary fatigue limit: 62.2MPa

(3-2) mechanical properties of test piece 2:

2 dendrite arm spacing: 8 to 25 μm

Tensile strength: 312MPa

0.2% yield strength: 238MPa

Elongation at break: 12.2 percent

·10⁷Secondary fatigue limit: 75.7MPa

(3-3) evaluation:

the 2 nd Dendrite Arm Spacing (DASII) is the length of the branches extending from the crystal. The shorter the branches, the stronger the casting.

The test piece 2 by the die casting method using the electromagnetic pump is superior to the test piece 1 by the gravity die casting method in all of DASII, tensile strength, yield strength, elongation at break, and fatigue limit.

As shown in fig. 8, the obtained knuckle casting 40 is cut along a boundary line 64.

As shown in fig. 9, the product portion 46 is separated from the non-product portion 47. The product portion 46 is finished into a knuckle by performing machining. The non-product portion 47 is scrap, and is redissolved for subsequent casting.

The present invention changes the release agent 134 described in fig. 6(b) to the thin powder release agent 65 described in fig. 7(b), which is one of the essential elements.

In the present invention, as illustrated in fig. 7(c), the temperature of each part of the mold 50 is set to a range of 120 to 240 ℃ immediately before casting. This temperature range can be extended to a range of 110 to 250 ℃ by combining with other experiments.

The casting time in experiment 05 was 39 seconds, the casting time in experiment 06 was 37 seconds, and the casting time in experiment 07 was 32 seconds.

If 40 seconds, which is half the casting temperature of 80 seconds in experiment 01, is set as the target casting temperature of the present invention, experiments 05 to 07 can achieve the target.

The melt temperature for experiment 05 was 670 ℃. Since the liquidus temperature was 615 ℃, the melt temperature for experiment 05 was (liquidus temperature +55 ℃).

The melt temperature of experiment 06 was 660 ℃. Since the liquidus temperature was 615 ℃, the melt temperature of experiment 06 was (liquidus temperature +45 ℃).

The melt temperature for experiment 07 is 635 ℃. Since the liquidus temperature was 615 ℃, the melt temperature for experiment 07 was (liquidus temperature +20 ℃).

If the melt temperature is 20 ℃ to 55 ℃ plus the liquidus temperature, it is expected that the casting time will be halved, and the productivity will be greatly improved.

The inventors of the present invention also verified that the casting time can be halved if the melt temperature is 20 ℃ to 55 ℃ above the liquidus temperature by using AC2B (liquidus temperature 595 ℃) and ADC12 (liquidus temperature 580 ℃).

From the above, the present invention can be summarized as follows.

An aluminum casting method for pouring a molten aluminum drawn by an electromagnetic pump into a mold, wherein the thickness of a powder mold release agent applied to the mold is set to be thinner than the thickness of the mold release agent in the gravity mold casting method, the temperature of the mold before pouring is controlled to be in the range of 110 to 250 ℃, and the temperature of the molten aluminum at the time of pouring is controlled to be a value obtained by adding 20 to 55 ℃ to the liquidus temperature of aluminum.

The electromagnetic pump is a unit for pouring molten liquid to the mold at low pressure.

By using a powder mold release agent that is thinner than the mold release agent in the gravity die casting method, the temperature of the melt can be lowered compared to the conventional method, and the temperature of the mold can be lowered compared to the conventional method, whereby the casting time can be halved compared to the conventional method, and the productivity can be improved.

Therefore, according to the present invention, a casting method capable of improving productivity without making the melt high pressure is provided.

The method of the present invention is applicable to casting a knuckle having a complicated structure, but the casting is not limited to the knuckle and may be any casting.

In the case where the casting time was controlled to be 40 seconds or less, the remaining amount was 1 second in the above experiment 05. Since the ambient temperature of the mold varies depending on the season and day and night, the margin is preferably set to about 3 seconds. In experiments 06 and 07, the remaining amount was 3 seconds or more.

In experiment 06, the temperature of the melt at the time of pouring was controlled to a value obtained by adding 45 ℃ to the liquidus temperature of aluminum.

In experiment 07, the temperature of the melt at the time of pouring was controlled to a value obtained by adding 20 ℃ to the liquidus temperature of aluminum.

In fig. 17, a melt 127 is poured into a mold 120 by a gravity die casting method or a low-pressure die casting method.

In the case of a casting method using an electromagnetic pump, the fluidity of melt 127 is improved as compared with the gravity die casting method or the low-pressure die casting method. If the fluidity is improved, a phenomenon equivalent to an increase in the flow rate occurs. That is, the larger the flow velocity, the more remarkable the generation and disturbance of the vortex. Therefore, in the casting method using the electromagnetic pump, a countermeasure against disturbance of the flow of the molten metal is strongly required, as compared with the gravity die casting method or the low-pressure die casting method.

As a countermeasure, the conical portion 57 shown in fig. 5 is effective. That is, the conical portion 57 exerts a significant effect in the casting method using the electromagnetic pump, as compared with the gravity die casting method or the low-pressure die casting method.

From the above, the method of the present invention can be summarized in the following manner.

The melt 12 shown in fig. 5 is pumped up by an electromagnetic pump (fig. 1, 20), supplied from the gate 58 to the main runner 59, branched along the conical surface 57b of the conical portion 57 to the first runner 61 and the second runner 62, and poured into the first chamber 53 through the first runner 61 and the second chamber 54 through the second runner 62.

The fluidity of the melt is improved by the electromagnetic pump (fig. 1, symbol 20). If the fluidity of the melt is high, the melt reaches the end of the cavity well, and therefore the melt temperature and the mold temperature can be reduced. When the melt temperature and the die temperature are lowered, the solidification time of the melt is shortened, and the productivity is further improved.

The number of the first runners 61 and the like branched from the main runner 59 is 3 in the embodiment, but the number may be 2 or 4 or more, and may be any number as long as 2 or more.

Further, even when the runner extends from the main runner 59 in a disk shape, the disk-shaped runner includes a first runner and a second runner in cross section, and therefore, the present invention also includes the runner.

The bottom surface of the conical portion 57 of the present invention may be any of a perfect circle, an ellipse, an oblong circle, and a deformed circle. Further, since the edge lines of pyramids such as triangular pyramids and rectangular pyramids become sources of turbulence, this is not preferable. However, if the pyramid has a rounded ridge, the pyramid belongs to the conical portion 57.

Therefore, the conical portion 57 is not limited to a narrow sense of a right cone.

However, if the gas is contained in the melt 12, the gas remains in the form of pores in the casting 35. The pores become casting defects, and are not preferable.

Therefore, it is also desirable to take measures against air exhaustion in the mold 50.

As a countermeasure against the air exhaustion, it is recommended to provide a "gap" locally in the mold 50. However, if the gap is large, although the gas-discharging property is large, a part of the melt enters the gap and becomes a burr. Conversely, if the gap is small, the generation of burrs is suppressed, but the air release property becomes small.

Further, since the fluidity of the melt 12 is improved by using the electromagnetic pump 20, the setting of the gap needs to be sufficiently studied.

Therefore, the size of the gap for exhaust is confirmed through experiments.

(4) The experimental conditions are as follows:

(4-1) casting method: gravity die casting method, low-pressure die casting method, or casting method using electromagnetic pump

(4-2) setting of clearance for exhaust: 0.01mm (10 μm) to 0.2mm (200 μm)

(4-3) matters confirmed in the experiment: good or bad of burr and exhaust

Experiment 11: experiments were conducted by setting the clearance for air exhaust to 0.2mm (200 μm) by gravity die casting or low-pressure die casting. When the clearance for air discharge was 0.2mm, no burr was generated and the air discharge performance was good, and therefore, the value was evaluated as o (good).

Experiment 12: experiments were conducted by setting the clearance for air exhaust to 0.1mm (100 μm) by gravity die casting or low-pressure die casting. When the clearance for air discharge was 0.1mm, the air discharge property was slightly poor, and therefore, the evaluation was x (poor).

Experiment 13: experiments were conducted by setting the gap for exhaust to 0.2mm (200 μm) by a casting method using an electromagnetic pump. Since the fluidity of the melt is increased by the electromagnetic pump, a large amount of burrs are generated when the clearance for degassing is 0.2 mm. The evaluation was X.

Experiment 14: experiments were conducted by setting the gap for exhaust to 0.1mm (100 μm) by a casting method using an electromagnetic pump. Even if the clearance for exhaust is 0.1mm, a small amount of burrs are generated. The evaluation was X.

Experiment 15: experiments were conducted by setting the gap for air exhaust to 0.08mm (80 μm) by a casting method using an electromagnetic pump. When the clearance for exhaust was 0.08mm, no generation of burrs was observed. The evaluation was O.

It is found that the burr problem can be eliminated even with the electromagnetic pump if the gap is 0.08mm (80 μm) or less. However, since the smaller the gap, the lower the air release property, the experiment was continued to verify this.

Experiment 16: experiments were conducted by setting the gap for exhaust to 0.05mm (50 μm) by a casting method using an electromagnetic pump. The air release property was maintained, and therefore, the evaluation was evaluated as ∘.

Experiment 17: experiments were conducted by setting the gap for exhaust to 0.03mm (30 μm) by a casting method using an electromagnetic pump. The air release property was maintained, and therefore, the evaluation was evaluated as ∘.

Experiment 18: experiments were conducted by setting the gap for exhaust to 0.02mm (20 μm) by a casting method using an electromagnetic pump. The air-discharge property is slightly deteriorated. The evaluation was X.

Experiment 19: experiments were conducted by setting the gap for exhaust to 0.01mm (10 μm) by a casting method using an electromagnetic pump. The exhaust performance is further deteriorated. The evaluation was X.

As can be seen from the above, in the casting method using the electromagnetic pump, the gap for exhausting air is preferably 0.03mm (30 μm) to 0.08mm (80 μm).

A specific example to which the gap having the above-described size is applied will be described below.

The mold 50 of the present invention is fitted with an air vent 70 described below.

As shown in fig. 10, the movable die 52, which is one of the components of the die 50, is provided with an exhaust portion accommodating recess 68 that opens into the cavity 67 and a through hole 69 that extends from the exhaust portion accommodating recess 68 to the outside of the die. The through hole 69 has a sufficiently smaller diameter than the exhaust section accommodating recess 68. The exhaust unit 70 is fitted into the exhaust unit housing recess 68. The exhaust unit 70 is already fitted into the exhaust unit housing recess 68 on the right side in the figure.

As shown in fig. 11, the exhaust unit 70 is, for example, a hollow body composed of a bottomed cylindrical body 72 having a bottom portion 71 and a lid 73 closing an open end of the cylindrical body 72. The cover 73 is fixed to the cylinder 72 by caulking, screwing, welding, or the like. The exhaust portion 70 is constructed of strong carbon steel.

The lid 73 is provided with a hole 74 continuous with the through hole (fig. 10, reference numeral 69). Further, the bottom portion 71 is provided with a vent hole 75.

The gas passing hole 74 that enters the cylinder 72 from the vent hole 75 reaches the through hole (fig. 10, reference numeral 69).

The lid 73 may be omitted, and the exhaust unit 70 may be constituted only by the bottomed cylinder 72 having the bottom 71.

As shown in fig. 12, the vent holes 75 are elongated slits having a width W of 30 to 80 μm, and are provided in the bottom portion 71 so that 2 or more (for example, 3) are parallel to each other. The slits are easily formed by a wire electric discharge machine.

As shown in fig. 13(a), the vent holes 75 may be slits arranged radially.

As shown in fig. 13(b), the vent hole 75 may be replaced with 2 or more fine circular holes 76. In this case, the diameter of the fine round hole 76 is 30 μm to 80 μm. However, since the number of the fine round holes 76 is large, the machining time is long. On the other hand, the slits can be regarded as holes formed by collecting fine circular holes 76. The slit is superior to the fine round hole 76 in view of the processing cost.

The molten aluminum 13 drawn by the electromagnetic pump 20 shown in fig. 1 is poured into the mold 50 through the liquid guide block 14. Prior to this pouring, the cavity 67 shown in fig. 10 is filled with air. This air is pressed by the melt 13 during the casting process. When pressed, the air passes through the air discharge portion 70 and is discharged through the through hole 69.

The melt 13 fills the cavity 67 instead of air. When full, the melt 13 contacts the bottom 71 shown in FIG. 12. As described above, the vent holes 75 having a size of 30 μm to 80 μm do not allow the melt 13 to pass therethrough. The vent holes 75 having a size of 30 to 80 μm allow only gas such as air to pass therethrough. As a result, the generation of burrs is suppressed.

The exhaust unit 70 having such an advantage can also serve as a product ejector pin. A specific example thereof will be described with reference to fig. 14.

As shown in fig. 14, the cylinder 72 is long enough to penetrate the movable mold 52 vertically. A flange 81 is attached to the upper end (a portion sufficiently distant from the bottom 71) of the cylindrical body 72.

The flange portion 81 is sandwiched by an upper ejector plate 82 and a lower ejector plate 83.

The movable die 52 is inserted by extending the guide rod 84 from the lower ejector plate 83.

A gate frame 85 is mounted on the movable mold 52, an ejector driving unit 86 is lowered from the gate frame 85, and the ejector driving unit 86 is connected to the upper ejector plate 82. The ejection drive unit 86 may be any one of an air cylinder, a hydraulic cylinder, and an electric cylinder.

The lower ejector plate 83 is biased upward by a compression spring 87, and the raised position is determined by a stopper 88 provided on the gate frame 85.

The air in the cavity 67 is exhausted through the exhaust portion 70, and instead, the cavity 67 is filled with the melt. When the melt solidifies, the movable die 52 is raised. Subsequently, the upper ejector plate 82 and the lower ejector plate 83 are lowered by the ejector driving unit 86. Then, the exhaust portion 70 protrudes into the cavity 67. By this projection, the casting is separated from the movable die 52.

Next, the upper ejector plate 82 and the lower ejector plate 83 are lifted by the ejector driving unit 86. Thereby, the state returns to fig. 14.

The cylinder 72 (the exhaust unit 70) also serves as a product ejector pin. The cylinder 72 (the air discharge portion 70) performs an air discharge function and a product squeezing function, and thus added value is improved.

The exhaust unit 70 may be provided integrally with the movable mold 52. However, since the vent hole 75 is fine, the vent part 70, which is separate from the movable die 52, is easily processed as in the embodiment.

Industrial applicability

The present invention is applicable to an aluminum casting method in which a molten aluminum drawn by an electromagnetic pump is poured into a mold, and a mold used in the casting method.

Description of the symbols

12 … molten metal, 20 … electromagnetic pump, 35 … casting, 36 … central part, 40 … steering knuckle casting, 41 … axle part, 42 … first extension part, 43 … second extension part, 45 … axle hole, 50 … mould, 53 … first cavity, 54 … second cavity, 56 … pillar part, 57 … conical part, 57a … vertex, 57b … conical surface, 58 … sprue, 59 … main sprue, 61 … first sprue, 62 … second sprue, 65 … powder demoulding agent in the invention, 67 … cavity, 70 … exhaust part, 71 … bottom, 72 … cylinder, 75 … vent hole, 134 … demoulding agent in the gravity mould casting method.

Claims (8)

1. An aluminum casting method for pouring a molten aluminum pumped by an electromagnetic pump into a mold, wherein,

the thickness of the powder release agent applied to the mold is set to be thinner than that of the release agent in the gravity die casting method,

the temperature of the mould just before casting is controlled within the range of 110-250 ℃,

the temperature of the molten liquid during casting is controlled to be a value obtained by adding 20-55 ℃ to the liquidus temperature of the aluminum.

2. A mold used in the aluminum casting method as recited in claim 1, which is a mold for casting a cast article having a central portion, a first projecting portion projecting from the central portion, and a second projecting portion projecting from the central portion in a direction different from that of the first projecting portion, wherein,

the mold has: a gate provided on a bottom surface, a main runner rising from the gate, a first runner branching from the main runner, a first cavity forming the first projecting portion from a melt supplied through the first runner, a second runner branching from the main runner, and a second cavity forming the second projecting portion from a melt supplied through the second runner,

a conical portion protruding toward the main runner is provided at an outlet of the main runner, and the melt passing through the main runner is distributed to the first runner and the second runner along a conical surface of the conical portion.

3. The mold of claim 2, wherein,

the casting is a steering knuckle and the casting is,

the central portion is a spindle portion having a spindle hole,

the mold further includes a pillar portion forming the axle hole,

the conical portion is provided at the front end of the column portion.

4. A mold for use in the aluminum casting method as recited in claim 1,

the mold is provided with an exhaust part for exhausting the gas accumulated in the cavity,

the exhaust part is provided with vent holes having a size of 30 to 80 μm.

5. The mold of claim 4, wherein,

the exhaust part is a cylinder fitted to the mold, and the cylinder has a bottom facing the cavity, and the vent hole is provided in the bottom.

6. The mold of claim 5, wherein,

the vent hole is a slit having a width of 30 to 80 μm.

7. The mold of claim 6, wherein,

the slits are arranged in the bottom in a manner that more than 2 slits are parallel to each other.

8. The mold of claim 5, wherein,

the barrel doubles as a product ejector pin for separating the casting from the mold.

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