JP2021098218A - Aluminum casting method - Google Patents

Abstract

To provide a casting method capable of increasing productivity without increasing the pressure of a molten metal.SOLUTION: In an aluminum casting method where a molten metal 12 of aluminum pumped up by an electromagnetic pump 20 is poured into a mold 50, the thickness of a powder release agent applied to the mold is set so as to be thinner than the thickness of a release agent in a gravity casting method, the temperature of the mold immediately before the molten metal pouring is controlled so as to fall within a range of 110 to 250°C, and the temperature of the molten metal upon the pouring is controlled to have a value obtained by adding 20 to 55°C to the liquidus temperature of aluminum.SELECTED DRAWING: Figure 1

Description

The present invention relates to an aluminum casting method.

An aluminum product can be obtained by melting an aluminum alloy (hereinafter referred to as aluminum or aluminum) and pouring the obtained molten metal into a mold.
As an aluminum product, a knuckle, which is one of vehicle parts, is known. A knuckle is a component having a complicated shape in which an overhanging portion extends radially around an axle portion.

A technique for manufacturing a knuckle by a gravity casting method has been proposed (see, for example, Patent Document 1).
Patent Document 1 discloses a gravity casting apparatus for knuckles and a gravity casting method. In this gravity casting device for knuckles, molten metal is poured from a sprue that opens upward. Due to the action of gravity, the molten metal flows down the runner and changes its direction horizontally. The molten metal that has changed direction flows in the order of one cavity, the cavity of the axle portion, and the other cavity to fill the cavity.

Further, a mold for casting a knuckle has been proposed (see, for example, Patent Document 2 (FIG. 6)).
The technique of Patent Document 2 will be described with reference to FIG. 10 (plan view).
As shown in FIG. 10, 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. ..

In addition, the mold 100 has a sprue 104 and a sprue 105. The runner 105 serves to connect the sprue 104 and the first cavity 102.
The molten metal flows in the order of the sprue 104, the runner 105, the first cavity 102, the central cavity 101, and the second cavity 103.

The techniques of Patent Document 1 and Patent Document 2 are called a gravity mold casting method. Since the pressure of the molten metal is remarkably low as compared with the high-pressure casting method represented by the die casting method, it is not necessary to make the mold strong and the casting apparatus does not need to be strong. Therefore, the gravity mold casting method is widely put into practical use.

On the other hand, the gravity mold casting method has the following drawbacks.
The flow velocity of the molten metal depends on gravity, so it is slow. Therefore, if the mold temperature is too low, the molten metal will solidify before reaching the end of the cavity.
As a countermeasure, raise the temperature of the mold. Empirically, the value obtained by adding 100 ° C. to the liquidus temperature is defined as the molten metal temperature.

By adding 100 ° C. to the liquidus temperature, the inconvenient solidification could be eliminated.
After pouring, the molten metal is cooled and solidified, but it takes time to solidify because the temperature of the mold is high. If it takes a long time to solidify, the production time is extended and the productivity is lowered.

If it is a high-pressure casting method such as a die casting method, the flow velocity of the molten metal is high and the productivity does not decrease. However, the mold and casting equipment are expensive and cannot be adopted.

While improvement in productivity is required, a casting method capable of increasing productivity without increasing the pressure of the molten metal is desired.

Japanese Unexamined Patent Publication No. 2014-76450 Japanese Unexamined Patent Publication No. 2012-143788

An object of the present invention is to provide a casting method capable of increasing productivity without increasing the pressure of molten metal.

The invention according to claim 1 is an aluminum casting method in which molten aluminum pumped by an electromagnetic pump is poured into a mold.
The thickness of the powder release agent applied to the mold is set to be thinner than the thickness of the release agent in the gravity casting method.
The temperature of the mold immediately before pouring is controlled so as to be within the range of 110 ° C to 250 ° C.
The temperature of the molten metal at the time of pouring is controlled to a value obtained by adding 20 ° C. to 55 ° C. to the liquidus temperature of the aluminum.

In the invention according to claim 1, the molten metal is pumped up by an electromagnetic pump. The electromagnetic pump imparts a minute pressure fluctuation to the molten metal, and this pressure fluctuation increases the fluidity of the molten metal. Since the fluidity of the molten metal is significantly higher than that of the molten metal in the gravity mold casting method, the temperature of the molten metal can be lower than that in the gravity mold casting method.
In addition, the fluidity of the molten metal in the low-pressure mold casting method is significantly higher than that of the molten metal, so that the temperature of the mold can be lowered.
Further, if the mold release agent is thin, the heat of the molten metal is rapidly transferred to the mold, and the solidification time is shortened.

As described above, the molten metal according to the present invention can be solidified in a much shorter time than the gravity mold casting method, and the productivity can be improved.
That is, the present invention provides a casting method capable of increasing productivity without increasing the pressure of the molten metal.

It is a principle figure of the casting apparatus which concerns on this invention. It is sectional drawing of the electromagnetic pump. It is a three-part enlarged view of FIG. It is a perspective view of a knuckle casting. It is a cross-sectional view of a mold, and is the cross-sectional view corresponding to the cross section of line 5-5 of FIG. It is a figure explaining the temperature range and the casting time of the mold in the comparative example. It is a figure explaining the temperature range of the mold and the casting time in an Example. It is sectional drawing of the knuckle casting immediately after the mold release. It is an exploded view of a knuckle casting. It is a top view of a conventional mold.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the holding furnace 10 is a furnace provided with a heater 11 to store the molten aluminum 12. An electromagnetic pump 20 is provided in the holding furnace 10. The molten metal 12 is heated or kept warm by the heater 11 above the melting point, and the temperature is controlled by the temperature control unit 66.
In this example, the steel frame 13 is mounted on the holding furnace 10, and the electromagnetic pump 20 is supported by the steel frame 13, but the mounting form of the electromagnetic pump 20 on the holding furnace 10 is arbitrary.

The holding furnace 10 may be a container for storing aluminum in a molten state, such as a melting furnace, a hot water discharge furnace, and a ladle, and is not limited to a holding furnace in a narrow sense.

The detailed structure of the electromagnetic pump 20 will be described with reference to FIG.
As shown in FIG. 2, the electromagnetic pump 20 includes a base flange 21, a hot water guide pipe 22 extending vertically through the base flange 21, and an iron core member 23 housed in the hot water guide pipe 22. The lower coil 24 that surrounds the lower part of the hot water guide pipe 22, the lower case 25 that is suspended from the base flange 21 while surrounding the lower coil 24, the upper coil 26 that surrounds the upper part of the hot water guide pipe 22, and the upper coil 26 are surrounded. It also includes an upper case 27 mounted on the base flange 21, a discharge pipe 28 extending upward from the hot water guide pipe 22, and a hot water level gauge 29 surrounding the discharge pipe 28.

When the lower coil 24 is energized, the molten metal (FIG. 1, reference numeral 12) is pulled up by Fleming's left-hand principle.
Next, when the upper coil 26 is energized and the lower coil 24 is de-energized, the molten metal is pulled up to the molten metal level 29. The level of the total water level 29 becomes the "standby level".

According to Fleming's left-hand rule, increasing the current increases the force.
When the current of the upper coil 26 is further increased, the molten metal exceeds the molten metal level gauge 29 and is discharged above the discharge pipe 28. Then, the hot water is poured into the mold 50 through the hot water guide block 14 shown in FIG.
Therefore, the electromagnetic pump 20 is a pressurized hot water pouring means for pumping the molten metal 12 stored in the holding furnace 10 and supplying it to the mold 50.

The mold 50 is provided with a heater and a water passage, and the temperature control unit 66 constantly measures the temperature of each part of the mold 50 and controls the temperature so that the measured value becomes a predetermined temperature. By this temperature control, the temperature of the mold 50 immediately before pouring is maintained at an appropriate temperature.

The present inventors paid attention to the pressure phenomenon peculiar to the electromagnetic action in the electromagnetic pump 20 as the pressurized hot water pouring means. This phenomenon will be described with reference to FIG.

As shown in FIG. 3, the molten metal 12 flows upward in the passage between the hot water guide pipe 22 and the iron core member 23. The magnetic field 31 reaching the iron core member 23 from the upper end portion 26a of the upper coil 26 is curved so as to be convex upward. The degree of this curvature fluctuates at 100 Hz, which is twice as high as 50 Hz.
Due to the fluctuation (displacement) of the magnetic field 31, the pressure (discharge pressure) of the molten metal 12 fluctuates minutely in a fine cycle (100 Hz). That is, fine pulsations are inevitably generated.

As shown in FIG. 4, the knuckle casting 40 includes a central axle portion 41, a first overhanging portion 42 that greatly overhangs from the axle portion 41, and a second overhanging portion 43 that overhangs from the axle portion 41 to the opposite side. It has a third overhanging portion 44 that overhangs from the axle portion 41 to the back. The axle portion 41 has an axle hole 45 in the center.
An example of the mold 50 for casting the knuckle casting 40 having such a form will be described with reference to FIG.

As shown in FIG. 5, the mold 50 includes a fixed mold 51 and a movable mold 52.
The movable mold 52 has a first cavity 53 forming a first overhanging portion (FIG. 4, reference numeral 42), a second cavity 54 forming a second overhanging portion (FIG. 4, reference numeral 43), and a third overhanging portion. A third cavity 55 is provided to form (FIG. 4, reference numeral 44).

In addition, the movable type 52 is provided with a pillar portion 56 for forming an axle hole (FIG. 4, reference numeral 45). The pillar portion 56 is a cylinder having a draft, and extends to the fixed mold 51 so as to penetrate the first to third cavities 55, and has a conical portion 57 sharpened downward at the tip.

The fixed type 51 is provided with a sprue 58 on the lower surface, a main sprue 59 extending upward from the sprue 58, and a first runway 61 and a second runner extending along the conical portion 57 while being branched by the conical portion 57. It has 62 and a third runway 63. The third runway 63 passes through the back and front of the conical portion 57 for convenience of drawing.
The first runway 61 is connected to the first cavity 53, the second runway 62 is connected to the second cavity 54, and the third runway 63 is connected to the third cavity 55.

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

Next, the molten metal to be poured into the mold 110 or the mold 50 will be described while comparing the conventional technique (gravity mold casting method) with the present invention (casting method using an electromagnetic pump).

In the gravity mold casting method, the mold temperature immediately before pouring (the temperature varies depending on the part) is controlled in the range of 240 ° C. to 360 ° C. In addition, the mold was coated with the mold release agent described in FIG. 6 (b).
As shown in FIG. 6A, hot water is poured from a sprue 111 provided at a high position of the mold 110. The molten metal fills the cavity 113 through a downwardly sloping runner 112.

As shown in FIG. 6B, the release agent 114 has a thickness ta of 150 μm based on experience.
For the release agent 114, for example, graphite or ceramics is dissolved in a solvent and applied to the mold 110 with a gun or a brush.
As shown in FIG. 6 (c), the casting time under this condition was 80 seconds.

As described with reference to FIG. 3, the use of an electromagnetic pump increases the fluidity of the molten metal. From this finding, the present inventors have noticed that the molten metal can flow to the end of the cavity even if the temperature of the molten metal is lowered. In addition, when the molten metal temperature is lowered, the mold temperature immediately before pouring can be lowered.

Furthermore, when the molten metal temperature is lowered, the thermal damage to the mold is reduced, so that the mold release agent can be thinned. In addition, the high fluidity of the molten metal also reduces the thermal damage to the mold, so that the mold release agent can be thinned.
Based on the above findings, the present invention has been derived. The details of the present invention will be described with reference to FIGS. 7 (a) to 7 (c).

In the casting method using an electromagnetic pump, the mold temperature immediately before pouring (the temperature varies depending on the part) is controlled in the range of 120 ° C. to 240 ° C. Even so, the molten metal flowed to the end of the cavity without solidifying. In addition, the mold was coated with the mold release agent described in FIG. 7 (b).
As shown in FIG. 7A, in the embodiment, hot water is poured into the mold 50 by the electromagnetic pump 20.

As shown in FIG. 7B, a powder release agent 65 was adopted as the release agent. The powder release agent 65 sprays powder onto the mold 50 by an electrostatic coating method.
The powder release agent 65 is made of, for example, a powder containing diatomaceous earth as a main component. Diatomaceous earth has innumerable fine gaps inside, and air is trapped in these gaps, so that it has excellent heat insulation performance. Even if the film thickness is thin, heat transfer from the molten metal to the mold 50 is satisfactorily blocked.

Due to electrostatic coating, the adhesive force of the sprayed material during painting increases. In addition, if the spray is powder, the powder will line up on the surface of the mold 50. Compared with the existing mold release agent, it is expected that the mold release performance will be sufficiently maintained even if it is thin. Therefore, in the present invention, the thickness Tb of the powder release agent 65 is set to 20 μm.

As shown in FIG. 7 (c), the molten metal temperature is lowered by 10 ° C. to 700 ° C., and the mold temperature immediately before pouring (the temperature varies depending on the part) is set to the range of 120 to 240 ° C. I took a bath. The casting time under this condition was 45 seconds.

Since the thickness Tb of the powder release agent 65 is thin, heat transfer from the molten metal to the mold 50 becomes active, and it is expected that the casting time can be significantly shortened.
Therefore, the present inventors tried to lower the molten metal temperature on the premise that the molten metal flows to the end of the cavity. The results are shown in the table.

Experiment 01: When a mold release agent of 150 μm was applied to the mold by the gravity mold casting method and the molten metal temperature was set to 710 ° C., the casting time was 80 seconds as described in FIG. 6 (c). It was.
Experiment 02: The molten metal temperature was lowered to 700 ° C., and other conditions were the same as in Experiment 01. The casting time was 60 seconds.

Experiment 03: When a mold was electrostatically coated with a 20 μm powder release agent and the molten metal temperature was set to 700 ° C. by a casting method using an electromagnetic pump, the casting time was as described in FIG. 7 (c). Was 45 seconds.
Experiment 04: The molten metal temperature was lowered to 680 ° C., and other conditions were the same as in Experiment 03. The casting time was 41 seconds.

Experiment 05: The molten metal temperature was lowered to 670 ° C., and other conditions were the same as in Experiment 03. The casting time was 39 seconds.
Experiment 06: The molten metal temperature was lowered to 660 ° C., and other conditions were the same as in Experiment 03. The casting time was 37 seconds.
Experiment 07: The molten metal temperature was lowered to 635 ° C., and other conditions were the same as in Experiment 03. The casting time was 32 seconds.

In the conventional technique (experiments 01 and 02), the casting time was 60 to 80 seconds, but in the technique of the present invention (experiments 03 to 07), the casting time is 32 to 45 seconds, and the casting time is almost halved. became.

The test piece cut out from the cast product obtained in Experiment 01 was designated as "test piece 1", and its mechanical properties were examined. Further, the test piece cut out from the cast product obtained in Experiment 07 was designated as "test piece 2", and the mechanical properties were examined.

The secondary dendrite arm space (DASII) is the length of the branch extending from the crystal, and the shorter the branch, the stronger the casting. The test piece 2 by the mold casting method using an electromagnetic pump was superior to the test piece 1 by the gravity mold casting method in all of the tensile strength, the strength, the elongation at break, and the fatigue limit.

As shown in FIG. 8, the obtained knuckle casting 40 is cut along the boundary line 64.
As shown in FIG. 9, the product unit 46 and the non-product unit 47 are separated. The product unit 46 is machined to make a knuckle. The non-product part 47 is scrapped, redissolved, and used for the next casting.

In the present invention, it is one of the essential elements that the mold release agent 114 described in FIG. 6 (b) is changed to the thin powder mold release agent 65 described in FIG. 7 (b).
Further, in the present invention, as described with reference to FIG. 7C, the temperature of each part of the mold 50 is set in the range of 120 ° C. to 240 ° C. immediately before pouring. This temperature range could be extended to the range of 110 ° C to 250 ° C when examined in combination with another experiment.

Further, in Table 1 described above, assuming that 40 seconds, which is half of the casting temperature of 80 seconds in Experiment 01, is set as the target casting temperature of the present invention, Experiments 05 to 07 were able to clear the target.

If the molten metal temperature is the liquidus temperature plus 20 ° C. to 55 ° C., the casting time is expected to be halved, and the productivity can be significantly improved.
In addition, the present inventors also verified AC2B (liquidus line temperature 595 ° C.) and ADC12 (liquidus line temperature 580 ° C.), and also set the molten metal temperature to the liquidus line temperature of 20 ° C. to 55 ° C. At the added temperature, the casting time could be halved.

Based on the above, the present invention can be summarized as follows.
This is an aluminum casting method in which molten aluminum pumped up by an electromagnetic pump is poured into a mold, and the thickness of the powder release agent applied to the mold is greater than the thickness of the mold release agent in the gravity casting method. It is set thinly, the temperature of the mold immediately before pouring is controlled to be within the range of 110 ° C to 250 ° C, and the temperature of the molten metal at the time of pouring is 20 ° C to the liquidus temperature of aluminum. The value is controlled by adding 55 ° C.

An electromagnetic pump is a means for pouring molten metal into a mold at a low pressure.
By adopting a thin powder release agent, lowering the temperature of the molten metal than before, and lowering the temperature of the mold than before, the casting time can be halved and productivity can be improved. Became.
Therefore, the present invention provides a casting method capable of increasing productivity without increasing the pressure of the molten metal.

The method of the present invention is suitable for casting a knuckle having a complicated structure, but the cast product is not limited to the knuckle and is arbitrary.

Further, when the casting time is controlled to 40 seconds or less, in Table 3 above, in Experiment 05, the margin is 1 second. Since the ambient temperature of the mold changes depending on the season and day and night, it is desirable to set the margin to about 3 seconds.
In this case, Experiments 06 and 07 correspond, and the temperature of the molten metal at the time of pouring is controlled to a value obtained by adding 20 ° C. to 45 ° C. to the liquidus temperature of aluminum.

The present invention is suitable for an aluminum casting method in which molten aluminum pumped by an electromagnetic pump is poured into a mold.

12 ... molten metal, 20 ... electromagnetic pump, 50 ... mold, 65 ... powder release agent according to the present invention, 114 ... mold release agent by gravity casting method.

Claims (1)

This is an aluminum casting method in which molten aluminum pumped up by an electromagnetic pump is poured into a mold.
The thickness of the powder release agent applied to the mold is set to be thinner than the thickness of the release agent in the gravity casting method.
The temperature of the mold immediately before pouring is controlled so as to be within the range of 110 ° C to 250 ° C.
An aluminum casting method characterized in that the temperature of the molten metal at the time of pouring is controlled to a value obtained by adding 20 ° C. to 55 ° C. to the liquidus temperature of the aluminum.

Images