JP2630601B2 - Manufacturing method of composite member - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a composite member formed by casting a fiber molded body with a matrix metal by high-pressure casting.

(Prior Art) Conventionally, in the above-mentioned composite member, a fiber formed body (hereinafter referred to as a formed body) in which fibers such as boron, carbon, alumina, silicon carbide, and stainless steel are formed into a predetermined shape is used as a matrix metal such as aluminum or an aluminum alloy. Various types of cast-in are known. And as a method of manufacturing the composite member,
The molded body is placed in a casting mold (hereinafter, referred to as a mold), a molten matrix metal (hereinafter, referred to as a molten metal) is introduced into the mold, and thereafter, the molten metal is introduced under pressure by a plunger engaged with the mold. Various high-pressure casting methods for solidifying in the pressurized state have been proposed (eg, Japanese Patent Publication No. Sho 62-38412,
See JP-A-60-114540.

By the way, the composite member manufactured by the high-pressure casting method has a fine structure, less shrinkage cavities, and high strength. However, when the molten metal is filled into the molded body, the molten metal solidifies from the chopstick in contact with the molded body, so that it is not sufficiently filled between the fibers of the molded body, and the structure of the matrix metal filled in the molded body is relatively small. There is a problem in that the composite member becomes coarse, and a composite member having sufficient strength cannot always be obtained.

Therefore, as disclosed in the above-mentioned Japanese Patent Publication No. 62-38412 and the like, casting is performed by preheating a compact before starting casting. However, since the molded body is preheated, the molten metal is sufficiently filled between the fibers of the molded body, but since the solidification speed of the molten metal filled in the molded body is lower than other parts, the composite is The problem is that shrinkage cavities are likely to occur near the boundary of the member, and the pressure of the plunger is not sufficiently transmitted to the molded body, and the structure of the matrix metal filled in the molded body is not always sufficiently dense. There is. In particular, for composite members manufactured using a sand core, the above tendency is remarkably exhibited.

For example, the rotor of a rotary engine has a triangular conical shape, an eccentric shaft is engaged in a bearing portion, and a ring gear is fixed to a side wall of the bearing portion. In addition, it is required that the bearing portion has wear resistance and sag resistance. Therefore, as shown in, for example, FIG. 10, various types of rotors R in which the bearing portion 30 is formed of a composite member have been tried. Since the rotor R is provided with a hollow portion such as the bearing portion 30 and the cooling passage 31, the high pressure is applied by using a sand core composed of an upper sand core and a lower sand core to form the hollow portion. It is manufactured by a casting method. That is, the rotor R supports the preheated molded body on the sand core, places the sand core in the mold, introduces the molten metal into the mold, and thereafter operates the plunger to add the molten metal. It is manufactured by pressing and holding a plunger in which the molten metal solidifies.

However, the molten metal in the mold solidifies from the part in contact with the mold, and the part surrounded by the upper sand core and the lower sand core, that is, the part where the molded body is disposed is solidified later. . Therefore, when the portion of the compact is solidified, the plunger-side portion, that is, the sprue side, has already completed solidification, so that the pressing force of the plunger does not act on the portion of the compact, and the density of the matrix metal is reduced. It is difficult to be dense enough. In addition, since the solidification rate is different between the portion of the molded body and the other portion, shrinkage cavities are likely to occur near the boundary of the bearing portion 30 formed as a composite member.

As described above, the rotor R is not necessarily formed with sufficient strength because the bearing portion 30 is not formed as a high-density composite member and shrinkage cavities are easily generated near the boundary of the bearing portion.

(Object of the Invention) The present invention has been made in view of the above conventional situation, and an object of the present invention is to provide a method of manufacturing a composite member capable of sufficiently filling a compact with a matrix metal and suppressing the occurrence of shrinkage cavities. Is to provide.

(Constitution of the Invention) According to the present invention, a sand core supporting a preheated molded body is placed in a mold, a molten metal is introduced into the mold by pressure, and the molten metal is kept in a pressurized state until the molten metal solidifies. A method of manufacturing a composite member by performing high-pressure casting to form a composite member by casting the above-mentioned molded body, and filling the molded body by disposing a cooling member between the molded body and a sand core. The solidification speed of the melt is increased so that the melt in the mold can be solidified uniformly as a whole.

That is, a structural feature of the present invention resides in that a cooling member for cooling the molten metal filled in the molded body to a temperature lower than the preheating temperature of the molded body is disposed between the molded body and the sand core. .

(Example) An example of the present invention will be described with reference to the drawings.

First Embodiment FIGS. 1 to 3 are explanatory views of a high-pressure casting apparatus used to carry out the method of the first embodiment.

The high-pressure casting apparatus 1 shown in the figure is an apparatus for manufacturing a rotor R of a conventionally known rotary engine shown in FIG. 10, and an upper die 3 having a cross-sectional shape corresponding to the outer shape of the rotor R.
The mold 2 in which the lower mold 4 and the molten metal introduction part 5 for accommodating the molten metal W are fixedly and separably connected to each other, and the molten metal W injected into the molten metal introduction part 5 is added to the upper and lower dies 3 and 4. A plunger 6 for introducing and holding the pressure, and a bearing portion 30 for the rotor;
And a sand core 7 forming a hollow portion such as the coolant passage 31.

The sand core 7 is composed of an upper sand core 8 and a lower sand core 12 fired by shell sand such as zircon sand, and a cooling member 14 and a molded body 15 as cooling members are mounted on the lower sand core 12. Have been. The upper sand core 8 has a cylindrical cavity 9 inside, and a protrusion 10 forming a coolant passage 31 of the rotor is formed outside, and a gap 11 between the protrusions 10 communicates with the cavity 9. It is formed. The lower sand core 12 has a rotor bearing 30 in the center.
Is formed, and a cylindrical cooling member 14 as a cooling member is integrally embedded in the projecting portion 13 when firing.

The chill 14 is formed of a good heat conductor such as steel or copper having good heat conductivity, and may be provided to be attached to the fired lower sand core 12.

The molded body 15 mounted in close contact with the cooling metal 14 is a cylindrical body in which a cylindrical portion 16 serving as a bearing portion 30 of the rotor and a gear-shaped projection 17 serving as a side wall of the bearing portion 30 are integrally formed. It is made of a fiber having high strength and high elasticity, such as boron, carbon, alumina, silicon carbide, and stainless steel, and is formed by press molding or the like.

As shown in FIG. 3, the sand core 7 is mounted on the lower sand core 12 in which the preheated molded body 15 is cooled and the gold 14 is buried, as shown in FIG.
Thereafter, the upper sand core 8 is mounted to be integrally assembled, and fixedly arranged on the lower mold 4 of the mold by a skirting board (not shown).

The high-pressure casting apparatus 1 shown in FIGS. 1 to 3 is configured as described above, and the manufacture of the rotor R is performed as follows.

At the time of casting, the molten metal W is made of aluminum, aluminum alloy, or the like, which is melted at about 700 ° C. or higher than the melting point.
The molded body 15 is preheated to 100 to 150 ° C, and the molded body 15 is preheated to 400 to 500 ° C. Then, the molded body 15 is mounted on the lower sand core 12, and the sand core 7 is integrally assembled as shown in FIG. 3, and the sand core 7 is disposed in the upper and lower dies 3, 4 of the mold. Then, the molten metal W is injected into the molten metal introducing section 5, and thereafter, the plunger 6 is operated upward to introduce the molten metal W into the upper and lower dies 3, 4, and a predetermined pressure (eg, 4)
It is cast by holding under pressure at 00 kg / cm ² ).

At this time, the molten metal W introduced into the upper and lower dies 3, 4 passes through the gate 18 as shown by the dotted arrow, passes through the gap 11 between the upper sand cores, and is filled into the molded body 15. Since the material 15 is preheated, it does not solidify directly even if it comes into contact with the molded body 15, so that it cools through the space between the fibers and is reliably filled to the gold 14 side. Then, it is rapidly cooled by the cooling metal 14, and solidification proceeds sequentially from the side of the cooling metal 14. On the other hand, plunger 6
The side, that is, the gate 18 side, is cooled by the mold 2 because it is in contact with the mold 2, and solidification also proceeds sequentially from the mold 2 side.

However, since the solidification rate by the chill 14 is higher, the solidification proceeds faster on the side of the molded body 15 than on the gate 18 side, and the side of the molded body 15 completes solidification before the gate 18 side completes solidification. That is, the side of the molded body 15 solidifies in a pressurized state of a predetermined pressure. Therefore, the molded body 15 is formed as a composite member filled with the matrix metal in a sufficiently dense state, and a high-strength rotor R having almost no shrinkage cavity near the boundary of the composite member is produced. become.

 For example, the following embodiment will be described.

Experimental Example A zircon sand having an average particle size of # 80 was baked as the sand core 7, a steel (S45C) was used as the chill 14, and an average fiber diameter 3 μm and an average fiber length 500 μm were used as the molded body 15.
Formed with an apparent density of 0.33 g / cc by short alumina alumina fibers, an aluminum alloy (JISAC8
A) and the like, preheat the molded body 15 to 500 ° C.
° C. preheated to melt the aluminum alloy 720 ° C., a pressure of the plunger 6 400 kg / cm ² As a result of casting the rotor shown in FIG. 10 is set to, at the same conditions without the cooling block Compared with the conventional rotor R to be manufactured, the composite member in which the compact 15 is filled with the aluminum alloy is formed as a structure having a high density, and the conventional method is used not only near the boundary of the composite member but also in other parts. No shrinkage cavities were observed as in the case of rotor R.

Second Embodiment In the second embodiment, instead of the chill 14 in the first embodiment, as shown in FIG.
This is a method of manufacturing a rotor R shown in FIG. 10 using a chill 14 provided extremely thinly.

The molded body 15 is mounted on the cooling metal 14 as shown in FIG. 4, but since the mold layer 20 having poor heat conductivity is interposed between the cooling metal 14 and the cooling metal 14, No direct contact with 14.
Therefore, the molded body 15 is not excessively cooled by the cooling metal 14 from the time of mounting to the start of casting, so that the coating layer
The preheating temperature can be set lower than in the case of the first embodiment in which 20 is not provided. Further, since the coating layer 20 is formed as an extremely thin layer, it does not significantly affect the solidification speed of the molten metal filled in the molded body 15. 400 ℃ lower than in the example
As a result, a composite member having a dense structure was formed as in the first embodiment, and almost no shrinkage cavities were observed.

The coating layer 20 is made of, for example, 55.5% SiO ₂ and Al ₂
O ₃ 2.0%, Fe ₂ O ₃ 4.0%, CaO 0.5%, MgO 25.0%, ZrO ₂
0.5%, C 6.0% and other 6.5% are dissolved in an alcohol solution to form a coating solution, cooled by a dipping method and formed on the surface of the gold 14 to a thickness of about 200 μm. Is also good.

Third Embodiment In a third embodiment, a compact 25 shown in FIG. 5 is used in place of the compact 15 of the first embodiment, and the compact 25 is attached to the lower sand core 12 as shown in FIG. This is a method for manufacturing a rotor (not shown) in which the composite member is formed only on the side wall of the bearing portion to which the ring gear is mounted.

The molded body 25 is made of the same material as that of the first embodiment, and is an annular body having an outer peripheral portion formed in a gear shape, which is preheated at the time of casting and is the same as that of the first embodiment as shown in FIG. Attached to the chill 14. Therefore, it passes through the gap 11 between the molten metal filled in the molded body 25 and the upper sand core, and passes through the protrusion 13 of the lower sand core.
The molten metal introduced to the side is cooled by contact with the cooling metal 14 and solidified earlier than the molten metal on the gate 18 side, and a composite member having a high density is formed in the portion of the molded body 25. A rotor R having high strength is produced with almost no shrinkage cavities near the boundary of the composite member.

Fourth Embodiment A fourth embodiment is a cooling system in which the coating layer 20 is provided extremely thinly at the portion where the molded body 25 contacts as shown in FIG. 7 instead of the cooling system 14 of the third embodiment. This is a method for manufacturing a rotor similar to that in the third embodiment using gold 14.

A coating layer having poor heat conductivity between the molded body 25 and the chill 14
Because of the interposition of 20, the preheating temperature of the molded body 25 can be set lower than in the third embodiment, and
Since 20 is formed as an extremely thin layer, the solidification speed of the molten metal filled in the compact 25 is not significantly affected, as in the second embodiment.

When the coating layer 20 is provided on the surface of the chill 14 by the same dipping method as in the second embodiment, only the surface in contact with the molded body 25 is roughened, so that the coating layer is formed only on the surface. 20 is provided at a predetermined thickness.

Fifth Embodiment The fifth embodiment is a method of manufacturing a rotor similar to that of the third embodiment by using the chill 14 shown in FIG. 8 instead of the chill 14 of the third embodiment.

A notch 21 is formed on the outer peripheral surface of one end of the chill 14 shown in FIG. 8 so as to be in contact with the inner peripheral surface of the molded body 25 and engage with the side surface of the molded body 25. Therefore, the molded body 25 is notched
The composite member can be formed at an appropriate position without being moved upward by the molten metal W at the time of casting because it is restrained by the molten metal W.

Sixth Embodiment The sixth embodiment is a method of manufacturing a rotor similar to that of the third embodiment by using the chill 14 shown in FIG. 9 instead of the chill 14 of the third embodiment.

A notch 22 is formed on the outer peripheral surface of one end of the chill 14 shown in FIG. 9 so as not to contact the inner peripheral surface of the molded body 25 but to engage with the side surface of the molded body 25. Therefore, the molded body 25 is
The preheating temperature can be set lower than in the fifth embodiment because the gap is not moved upward by the molten metal W during casting and the gap 23 with the outer peripheral surface of the chill 14 becomes a heat insulating layer. .

In each of the above embodiments, the lower sand core 12 is
13 is equipped with a chill 14 so that the strength is higher than before, the amount of shell sand used is reduced, and the heat is transferred by the chill 14, so the core disintegration is excellent. ing.

(Effects of the Invention) According to the present invention, by providing a cooling member for cooling the molten metal filled in the compact to a temperature lower than the preheating temperature of the compact, between the sand core and the compact. The molten metal filled in the compact is solidified earlier than on the gate side, and the solidification speed of the molten metal as a whole can be made uniform.

That is, the molten metal filled in the compact can be solidified substantially in a pressurized state, thereby increasing the density of the matrix metal in the portion of the compact as compared with the related art, and increasing the distance between the portion of the compact and other portions. Can suppress the occurrence of shrinkage cavities. Thereby, it became possible to manufacture a composite member having high density, no shrinkage cavities, and high strength.

[Brief description of the drawings]

FIG. 1 is a sectional front view of a high-pressure casting apparatus used in the method of the first embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. FIG. 4 is an assembled view of the sand core according to the first embodiment, FIG. 4 is a sectional view of a main part of the sand core according to the second embodiment of the present invention, and FIG. 5 is a method according to the third to sixth embodiments of the present invention. FIG. 6 is a perspective view of a fiber molded body to be used, FIG. 6 is a sectional view of a main part of a sand core according to a third embodiment of the present invention, and FIG. FIG. 8 is a sectional view of a main part of a sand core according to a fifth embodiment of the present invention.
The figure is a sectional view of a main part of a sand core according to a sixth embodiment of the present invention,
FIG. 10 is a front view showing a rotor of a conventional rotary engine, partially cut away. 1 high-pressure casting device, 2 casting mold, 6 plunger, 7 sand core, 8 upper sand core, 12 lower sand core,
14 …… Cold, 15,25 …… Fiber molded body, 18 …… Gate, 20
... coating layer, 21,22 ... notch, 23 ... gap between fiber molded body and chill, R ... rotor, W ... molten matrix metal.

Claims (1)

(57) [Claims] 1. A sand core supporting a preheated fiber molded body is placed in a casting mold, a molten matrix metal is introduced under pressure into the casting mold, and the molten matrix metal is heated until the molten matrix metal solidifies. In a casting method of a composite member for producing a composite member by performing high-pressure casting while maintaining a pressure state and casting the fiber molded body, the molten matrix metal filled in the fiber molded body is preheated to the fiber molded body. A method for producing a composite member, wherein a cooling member for cooling to a temperature lower than the temperature is disposed between the fiber molded body and the sand core.