JP2004291041A - Preformed body for composition and method for manufacturing sand mold provided with the body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the ingress of molten metal into a sand core 13 while ensuring ventilation between a preformed body 1 and the sand core 13 when performing composition of the preformed body 1 and molten metal while discharging air inside the preformed body 1 for composition held by the sand core 13 into the sand core 13. <P>SOLUTION: On the sand mold contact surface (an inner circumferential surface) in contact with the sand core 13 in the preformed body 1, there is formed an air permeable molten metal ingress preventive layer 1a to prevent the ingress of molten metal impregnated inside the preformed body 1 during the composition from a sand mold contact surface into the sand mold 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the technical field related to a composite preform to be impregnated with a molten metal and a method for producing a sand mold including the same.
[0002]
[Prior art]
In general, in a cylinder block made of an aluminum alloy, a liner member made of cast iron is cast-in or press-fitted into an inner wall portion of a cylinder bore in which a piston and a piston ring slide to improve wear resistance.
[0003]
However, in this configuration, in addition to the weight increase due to the liner member, a cast-in allowance and a press-fit allowance for holding the liner member are required, so that it is difficult to reduce the pitch between the cylinder bores. Further, since the cast-in or press-fitting of the liner member is not a metallurgical joining but a mechanical fitting, a gap in heat transfer occurs between the cylinder block main body and the liner member. For this reason, the method of cast-in or press-fitting the liner member cannot sufficiently exhibit the characteristics of aluminum such as light weight and good thermal conductivity.
[0004]
Therefore, in recent years, cylinder blocks without liner members have been developed and put to practical use in order to promote the weight reduction of cylinder blocks and to improve engine performance by making use of good thermal conductivity. There is known a method in which a cylinder bore portion is compositely reinforced with a composite material (reinforcing material) such as ceramic fiber (for example, alumina short fiber or carbon short fiber) to improve wear resistance. In this method, beforehand, a preform for forming a composite made of the above-described composite material and having pores therein is formed, and the preformed body is set at a predetermined position of a mold. The molten metal is injected and impregnated into the preform, and in this way, a cylinder block in which the cylinder bore is composited with the composite material is manufactured.
[0005]
In the case of forming a composite by such a method, from the viewpoint of ensuring that the preform is impregnated with the molten metal to obtain sufficient composite properties, the high-pressure casting method (molten metal forging) disclosed in Patent Document 1 is usually used. Method) or a low-speed medium-pressure die casting method.
[0006]
[Patent Document 1]
JP-A-2002-96141
[0007]
[Problems to be solved by the invention]
However, in the above-described high-pressure casting method and low-speed medium-pressure die-casting method, it is necessary to pressurize the molten metal at a high pressure (about several tens of MPa). There is a problem in that the use of the sex core is restricted, and the degree of freedom of the shape of the cast product is reduced. (In the Patent Document 1, a sand core is used. Since the resin coat is applied and the pressure is applied substantially uniformly to the entire periphery, the resin coat can withstand a certain high pressure.)
[0008]
On the other hand, if the molten metal is pressurized at a low pressure, sand molds and sand cores can be used, reducing costs and increasing the degree of freedom in the shape of the cast product. Since air remains in (in the pores), it is difficult to completely discharge this air with a low-pressure molten metal, so that the impregnating property of the preform is low, and a good composite is obtained. You will not be able to get the character.
[0009]
Therefore, the preform is held in a sand mold, and at the time of compounding with the molten metal, the pressure in the sand mold is reduced to about -1 atm (0.10 MPa) so that air inside the preform is discharged to the sand mold. It is possible to do. In this way, it is possible to secure sufficient complexity only by the depressurizing force without much pressurizing the molten metal (the pressure of the molten metal may be, for example, about 0.007 MPa).
[0010]
However, when the pressure in the sand mold is reduced, there arises a problem that the molten metal impregnated inside the preform tends to penetrate into the sand mold. On the other hand, if a resin coat or the like is applied to the surface of the sand mold as described in Patent Document 1 so as to prevent the molten metal from entering the sand mold, the ventilation between the preform and the sand mold is shut off, and the preforming is performed. The air inside the body cannot be discharged to the sand mold.
[0011]
The present invention has been made in view of such a point, and an object of the present invention is to discharge air inside the composite preform held by a sand mold into the sand mold as described above. An object of the present invention is to prevent infiltration of a molten metal into a sand mold while securing ventilation between the preformed body and the sand mold when the molded body and the molten metal are combined.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a molten metal having air permeability and impregnated into the inside of the preform at the time of compounding is formed on the sand mold contact surface of the preform for composite formation from the sand mold contact surface. A molten metal intrusion prevention layer for preventing intrusion into the sand mold is formed.
[0013]
Specifically, according to the first aspect of the present invention, the air inside the sand mold is discharged from the sand mold contact surface in contact with the sand mold in the holding state during the compounding with the molten metal by the reduced pressure in the sand mold when the sand mold is combined. In addition, the present invention is directed to a composite preform that is impregnated with the molten metal from the other side as the air is discharged to form a composite.
[0014]
And, on the sand mold contact surface, there is formed a molten metal infiltration prevention layer which has air permeability and prevents the molten metal impregnated therein during the complexing from entering the sand mold from the sand mold contact surface. And
[0015]
With the above configuration, since the molten metal permeation preventing layer has air permeability, the internal air is discharged from the sand mold contact surface of the preform to the sand mold due to the reduced pressure in the sand mold. Thereby, even if the pressure of the molten metal is considerably low, the molten metal is impregnated into the preformed body, and sufficient composite properties can be obtained. On the other hand, the molten metal impregnated in the preform is prevented from entering the sand mold by the molten metal intrusion prevention layer. Such a molten metal permeation prevention layer can be composed of ceramic fibers, ceramic particles, or the like, and can be easily obtained by adjusting the volume ratio of the fibers or particles and the average pore diameter (also referred to as cell diameter) inside thereof. Can be In addition, when a sand mold is formed on the sand mold contact surface of the preform via a melt infiltration prevention layer, the sand can be prevented from entering the composite preform by the melt infiltration prevention layer. Become.
[0016]
According to a second aspect of the present invention, in the first aspect, the molten metal infiltration preventing layer is configured to prevent the molten metal from entering the sand mold from the sand mold contact surface when the molten metal impregnation pressure is 1 atm or less. It is assumed that
[0017]
That is, the impregnation pressure of the molten metal is represented by the sum of the pressure of the molten metal and the depressurizing force (absolute value) in the sand mold. When the impregnation pressure is 1 atm or less, the molten metal infiltration preventing layer If the infiltration of the molten metal into the sand mold can be prevented, the function and effect of the first aspect of the invention can be sufficiently obtained.
[0018]
According to a third aspect of the present invention, in the first or second aspect of the present invention, the molten metal permeation preventing layer is constituted by a fiber molded body made of ceramic fibers.
[0019]
According to a fourth aspect of the present invention, in the third aspect, the ceramic fiber is at least one selected from the group consisting of alumina fiber, silica fiber, carbon fiber, potassium titanate whisker and aluminum borate whisker. And
[0020]
According to these inventions, it is possible to easily form a molten metal infiltration preventing layer having good air permeability and capable of reliably preventing infiltration of the molten metal into the sand mold. Also, on the sand mold contact surface of the preform, via a molten metal intrusion prevention layer, for example, when forming a sand mold by blow pressure, the molten metal intrusion prevention layer acts as a cushion against the blow pressure, It is possible to prevent the preformed body from being deformed or damaged by the sand to which the blow pressure is applied.
[0021]
According to a fifth aspect of the present invention, in the third or fourth aspect, the volume ratio of the ceramic fibers is set to 8% or more of the entire fiber molded body.
[0022]
This makes it possible to more easily form the molten metal permeation preventing layer having good air permeability and capable of reliably preventing the molten metal from entering the sand mold.
[0023]
According to a sixth aspect of the present invention, in the first or second aspect of the invention, the molten metal permeation preventing layer is made of ceramic particles.
[0024]
According to a seventh aspect of the present invention, in the sixth aspect, the average particle diameter of the ceramic particles is set to 10 μm or less.
[0025]
According to these inventions, by mixing ceramic particles with water or the like to form a slurry, and applying the slurry to a sand mold contact surface with a brush or the like, air permeability is good and penetration of the molten metal into the sand mold is reliably prevented. It is possible to easily form a molten metal intrusion prevention layer that can be used.
[0026]
According to the invention of claim 8, the air inside is held by the sand mold, and the air inside the sand mold is discharged from the sand mold contacting surface in contact with the sand mold in the holding state by depressurization in the sand mold and the discharge of the air during the compounding with the molten metal. On the sand mold contacting surface of the composite preform which is impregnated with the molten metal from the other side and is compounded from the other side, a pressure is applied to sand to form the sand mold by applying pressure to the sand. It is an invention of a method for manufacturing a sand mold having a molded body.
[0027]
In the present invention, the step of forming the composite preform and the step of forming the composite preform include: Forming a molten metal intrusion prevention layer for preventing the molten metal impregnated in the body from intruding into the sand mold from the sand mold contact surface; and forming the molten metal on the sand mold contact surface of the composite preform. Forming the sand mold through the infiltration-preventing layer.
[0028]
This makes it possible to easily manufacture a sand mold holding the preform, and to suppress the sand from entering the composite preform in the sand mold forming step.
[0029]
According to the ninth aspect of the present invention, in the ninth aspect, the molten metal infiltration preventing layer is a fiber made of a ceramic fiber, which is capable of preventing sand constituting the sand mold from entering the composite preform during sand molding. It is constituted by a molded body.
[0030]
In this way, sand can be reliably prevented from entering the composite preform, and in the sand mold forming step, for example, when a sand mold is formed by blow pressure, the molten metal infiltration preventing layer is provided. By acting as a cushion against the blow pressure, the preformed body can be prevented from being deformed or damaged by the sand to which the blow pressure has been applied. Such a molten metal infiltration preventing layer can be easily obtained by adjusting the volume ratio and cell diameter of the ceramic fiber. A cushion effect against pressure is obtained.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a composite preform 1 according to an embodiment of the present invention. As shown in FIG. 2, the preform 1 is provided on an inner wall portion of a cylinder bore of an aluminum alloy cylinder block 2 in an automobile engine. This is used to form the composite layer 2a. The composite layer 2a is obtained by impregnating the preformed body 1 with a molten metal of an aluminum alloy base material (for example, AC4D specified in JIS H5202) and then forming a composite. Accordingly, the cylinder block 2 does not require a liner member made of cast iron, so that the cylinder block 2 can be reduced in size and weight as compared with the cylinder block 2 having a liner member, and has good thermal conductivity.
[0032]
2, 3 is a water jacket formed around the cylinder bore and through which cooling water flows, 4 is an oil gallery formed to extend in the crankshaft direction and through which engine oil flows, and 5 is an oil gallery. , A crankcase that forms a crank chamber that houses the crankshaft.
[0033]
The preform 1 is made of ceramic fiber (alumina short fiber, carbon short fiber, etc.) or a metal having good wear resistance (18-8 stainless steel (Fe-18Cr-8Ni), tungsten, molybdenum, carbon steel, etc.). The composite material 1 is made of a composite material such as a metal fiber material or a porous metal body, and has pores therein. The volume ratio of the composite material 1 is, for example, 10%. As an example, when the preform 1 was actually made of a porous metal (Fe-18Cr-8Ni), a preform having a volume ratio of 10% and a cell diameter of 0.38 mm was obtained.
[0034]
As shown in FIG. 1, the preform 1 has a cylindrical shape (that is, has a through-hole penetrating the center of a cylinder) so as to conform to the shape of the inner wall of the cylinder bore. The entire surface (the inner wall surface of the through-hole) is held in an externally fitted state on the outer peripheral surface of the first sand core 13 having a cylindrical shape as a sand mold, as described later (see FIG. 3). In this holding state, the inner peripheral surface of the preform 1 becomes a sand mold contact surface that comes into contact with the sand mold (the first sand core 13). Then, as described later, the air in the preform 1 is discharged from the sand mold contact surface (inner peripheral surface) to the first sand core 13 due to the reduced pressure in the first sand core 13, and the air is discharged. As a result, the molten metal is impregnated into the preform 1 from a surface other than the inner peripheral surface (mainly the outer peripheral surface). In this embodiment, the sand mold contact surface is also a sand mold held surface held by a sand mold, but the portion held by the sand mold is located at a location different from the sand mold contact surface from which air is discharged (for example, pre-formed). (Both end faces of the body 1).
[0035]
On the inner peripheral surface of the preform 1, the molten metal having air permeability and impregnated inside the preform 1 at the time of the compounding enters the first sand core 13 from the inner peripheral surface. Is formed. When the impregnation pressure of the molten metal (the sum of the pressure applied to the molten metal and the depressurizing force (absolute value) in the first sand core 13) is 1 atm or less, the molten metal infiltration preventing layer 1a becomes The inner peripheral surface of the first sand core 13 is configured to be prevented from entering the first sand core 13. In this embodiment, as described later, the pressure of the molten metal is considerably smaller than the depressurizing force (absolute value) in the first sand core 13, and the impregnation pressure of the molten metal is substantially equal to the pressure in the first sand. The pressure is substantially the same as the absolute value of the decompression force in the child 13.
[0036]
The molten metal permeation prevention layer 1a is formed of a fiber molded body made of ceramic fiber, and the ceramic fiber is selected from the group consisting of alumina fiber, silica fiber, carbon fiber, potassium titanate whisker, and aluminum borate whisker. The volume ratio of the ceramic fibers is preferably at least 8% of the entire fiber molded body. That is, if the volume fraction of the ceramic fiber is less than 8%, the cell diameter becomes large and the air permeability becomes good, but it is difficult to reliably prevent the molten metal from entering the first sand core 13. Because it becomes. On the other hand, the upper limit of the volume fraction of the ceramic fiber is not particularly defined, but is about 30%, which is the limit at which molding is possible. Air permeability can be ensured (if not 100%). However, from the viewpoint of obtaining good air permeability, it may be 30% or less. As an example, when the hot water infiltration preventing layer 1a was actually made of an alumina short fiber molded product, a material having a volume ratio of 10% and a cell diameter of about 10 μm was obtained. Thus, the cell diameter of the molten metal permeation prevention layer 1a is considerably smaller than the cell diameter of the preform 1 (the main body excluding the molten metal permeation prevention layer 1a).
[0037]
In order to compound the preform 1 with the molten metal, first, as shown in FIG. 3, a first sand core 13 having the preform 1 is manufactured. At the center of the first sand core 13, a decompression pipe 19 for depressurizing the inside of the first sand core 13 and thus the inside of the preform 1 is arranged. One end of 19 is located inside the first sand core 13, while the other end protrudes outside of the first sand core 13. Means (not shown).
[0038]
In order to manufacture the first sand core 13, a sand core manufacturing apparatus 20 as shown in FIG. 4 is used. The sand core manufacturing apparatus 20 has a pair of upper and lower dies of an upper die 21 and a lower die 22, and the lower surface of the upper die 21 and the upper surface of the lower die 22 form cavities 23, respectively. Recesses 21a and 22a having a circular cross section are formed. A portion near the side surface of the concave portion 22a of the lower mold 22 is a set portion 22b in which the preform 1 is set. The depth of the set portion 22b is set to be substantially the same as the length of the preform 1. The portion closer to the center than the set portion 22b is formed to be slightly deeper than the set portion 22b. A pipe support hole 22c capable of supporting the pressure reducing pipe 19 is formed in a lower portion of the lower mold 22.
[0039]
In the upper part of the upper mold 21, a plurality of sand filling holes 21b for filling the cavity 23 with sand are formed. On the upper side of the upper die 21, a sand storage case 25 having a concave portion 25a forming a sand storage portion 24 together with the upper die 21 is formed on the lower surface, and the sand is stored in the sand storage portion 24. Can be put in. This sand contains a resin as a curing agent that is cured by an amine gas. As the sand, for example, silica sand having a particle size index AFS of 65 to 73 (average particle size of 0.2 to 0.3 mm) or the like can be used.
[0040]
A gas supply pipe 26 for supplying factory air at a predetermined pressure into the sand storage section 24 is provided at an upper portion of the sand storage case 25. When factory air at a predetermined pressure is supplied to the cavity, the sand in the sand container 24 is filled into the cavity 23 through the sand filling hole 21b. That is, the sand core manufacturing apparatus 20 forms the first sand core 13 by applying pressure (blow pressure) to the sand.
[0041]
Next, a method of manufacturing the first sand core 13 including the preform 1 using the sand core manufacturing apparatus 20 will be described with reference to FIG.
[0042]
First, the preform 1 (main body) is prepared, and separately from this, a cylindrical fiber molded body 31 (paper-like one) to be the molten metal intrusion prevention layer 1a is prepared. The outer diameter of the fiber formed body 31 is set slightly smaller than the inner diameter of the preformed body 1 (main body).
[0043]
After that, as shown in FIG. 5A, the preform 1 and the fiber compact 31 are set in the setting portion 22b of the lower mold 22 in the sand core manufacturing apparatus 20. That is, the fiber formed body 31 is inserted into the through-hole of the preformed body 1 so that the inner peripheral surface of the preformed body 1 is covered with the fiber formed body 31 (that is, the inner peripheral surface of the preformed body 1). Both are set on the set portion 22b (with the molten metal intrusion prevention layer 1a formed on the surface) (see FIG. 5B for the setting completed state). At this time, the preformed body 1 and the fiber formed body 31 do not need to be integrated by an adhesive or the like, as long as the fiber formed body 31 is attached to the preformed body 1 by its own weight so as not to shift downward. Good. The preformed body 1 and the fiber formed body 31 are integrated by blow pressure as described later.
[0044]
Subsequently, as shown in FIG. 5B, the pipe 19 for pressure reduction is supported in the pipe support hole 22 c of the lower mold 22, and sand (and resin) is put into the concave portion 25 a of the sand storage case 25 to form the concave portion. The opening 25a is closed with the upper mold 21 to form the sand container 24.
[0045]
Then, the upper mold 21 and the lower mold 22 are clamped to each other. Thereafter, as shown in FIG. 5C, a predetermined pressure of factory air (blow pressure) is introduced into the sand container 24 through the gas supply pipe 26. Supply. As a result, the sand in the sand accommodating portion 24 is filled into the cavity 23 through the sand filling hole 21b, and the preform 1 and the fiber molded body 31 (the molten metal intrusion prevention layer 1a) are integrated by the blow pressure. The first sand core 13 is formed on the inner peripheral surface of the preform 1 via the molten metal intrusion prevention layer 1a. Thereby, the through hole of the preform 1 is filled with the first sand core 13, and the first sand core 13 penetrates the through hole of the preform 1. After that, when the sand accommodating case 25 is removed and the amine gas flows into the first sand core 13 from the sand filling hole 21b of the upper die 21, the resin mixed in the sand is cured by the amine gas, The preform 1 is held on the outer peripheral surface of one sand core 13.
[0046]
At the time of forming the first sand core 13, the molten metal permeation prevention layer 1 a serves to prevent sand (including resin) constituting the first sand core 13 from entering the preform 1. Things. That is, if the molten metal permeation preventing layer 1a is configured to prevent the molten metal from entering the first sand core 13 from the inner peripheral surface of the preformed body 1 during compounding, the sand is usually preformed. It is possible to prevent the body 1 from entering the body. The molten metal permeation prevention layer 1a also functions as a cushion against the blow pressure, and also functions to prevent the preformed body 1 from being deformed or damaged by the sand to which the blow pressure is applied.
[0047]
Next, as shown in FIG. 5 (d), the upper mold 21 and the lower mold 22 are opened, and the first sand core 13 is taken out from the concave portion 22 a of the lower mold 22. The preform 1 is held on the outer peripheral surface of the first sand core 13, and a pressure reducing pipe 19 is disposed at the center of the first sand core 13. After the first sand core 13 is formed, the depressurizing pipe 19 may be inserted into the center of the first sand core 13 and disposed.
[0048]
Next, a method of manufacturing the cylinder block 2 by combining the preform 1 held by the first sand core 13 with a molten metal will be described.
[0049]
The cylinder block 2 is manufactured by a sand type low pressure casting method using a casting apparatus 10 as shown in FIG. That is, the casting apparatus 10 includes an upper die 11, a lower die 12, and a second sand core 14 as a mold in addition to the first sand core 13. The first sand core 13 is disposed in a portion corresponding to the inside of the cylinder bore, whereby the preform 1 is set in the cavity 16 while being held by the first sand core 13. Will be. Further, the second sand core 14 is disposed in a portion corresponding to the inside of the crankcase 5, and the side of the first sand core 13 from which the pressure reducing pipe 19 protrudes (corresponding to the crankcase 5). (A side to be formed) is bonded with a mold adhesive (molpet or the like) via a low air permeability layer 15 having almost no air permeability. Further, the upper die 11 is provided at a portion corresponding to the outside of the crankcase 5 and the cylinder bore, and the lower die 12 is provided at a portion corresponding to the upper end side of the cylinder bore. In other words, the upper mold 11, the lower mold 12, the first sand core 13 and the second sand core 14 have the same shape as the cylinder block 2 in the mold so that the vertical relationship with the actual engine arrangement is reversed. (In FIG. 6, the sand cores for forming the water jacket 3 and the oil gallery 4 are omitted, and the shape of the cavity 16 is simplified.) The surface of the first sand core 13 opposite to the second sand core 14 is in contact with the upper mold 11 via a low air permeability layer 18 having almost no air permeability.
[0050]
The upper mold 11, the lower mold 12, and the second sand core 14 are also sand molds formed by applying pressure to sand, similarly to the first sand core 13. The mold 12 and the second sand core 14 may be molds. However, from the viewpoint of increasing the degree of freedom of the shape of the cylinder block 2, a sand mold is preferable, and since the molten metal is filled into the cavity 16 at a low pressure as described later, there is no problem even if such a sand mold is used. When the upper mold 11 is formed of a mold, the low air permeability layer 18 is not required.
[0051]
The lower mold 12 is provided with a molten metal passage 17 for filling the cavity 16 with the molten metal, and a gate 17 a communicating with the cavity 16 is formed at a tip end of the molten metal passage 17. The molten metal is filled into the cavity 16 through a molten metal passage 17 and a gate 17a by a not-shown electromagnetic pump or pressurizing means used for low-pressure casting such as compressed air. The casting temperature of the molten metal is set to, for example, 750 ° C.
[0052]
The decompression pipe 19 penetrates vertically through the second sand core 14, and an end of the decompression pipe 19 opposite to the first sand core 13 is connected to decompression means such as a decompression pump. ing. In the present embodiment, the decompression force is set to -1 atm to -0.72 atm (-0.10 MPa to -0.073 MPa). On the other hand, the pressure of the molten metal is set to about 0.007 MPa, which is considerably smaller than the pressure reducing force, and the impregnation pressure of the molten metal is substantially the absolute value of the pressure reducing force in the first sand core 13. It is almost the same pressure as.
[0053]
When the pressure reducing means is operated, the pressure in the first sand core 13 and thus the inside of the preform 1 is reduced through the pressure reducing pipe 19, whereby the air inside the preform 1 has air permeability. The air discharged to the first sand core 13 via the molten metal permeation prevention layer 1a is sucked into the pressure reducing pipe 19 and discharged to the outside of the mold. At this time, low air permeability layers 15 and 18 are formed between the first sand core 13 and the second sand core 14, and between the first sand core 13 and the upper die 11, respectively. Therefore, the inside of the second sand core 14 and the inside of the upper mold 11 are not depressurized via the first sand core 13, and the inside of the preform 1 is depressurized, and the air inside the It is sure to be sucked.
[0054]
When the molten metal is filled into the cavity 16 through the molten metal passage 17 and the sprue 17a while operating the pressure reducing means as described above, the molten metal is impregnated into the preform 1 by almost only the reduced pressure force. The molded body 1 is composited. At this time, the molten metal is surely impregnated in the preform 1 only by the above-mentioned reduced pressure, and a sufficient composite property is obtained. At this time, the maximum impregnation pressure of the molten metal is 1 atm. However, when the impregnation pressure of the molten metal is 1 atm or less, the molten metal enters the first sand core from the inner peripheral surface of the preform 1. Since it is configured to prevent infiltration into the inside of the first sand core 13, the molten metal does not enter the first sand core 13.
[0055]
Then, after the molten metal filled in the cavity 16 is solidified, the entire mold is placed in a heating furnace and heated, whereby the resin of the upper mold 11, the lower mold 12, the first sand core 13, and the second sand core 14 is formed. Decomposes and the sand molds 11 to 14 collapse. At this time, the molten metal permeation prevention layer 1a peels off from the inner peripheral surface of the preform 1 together with the sand. Thus, the cylinder block 2 is completed. Since the inner wall portion of the cylinder bore of the cylinder block 2 is further blast-finished, even if a part of the molten metal permeation prevention layer 1a remains on the inner peripheral surface of the preform 1, Completely removed by blasting. In addition, a predetermined portion is subjected to machining or the like.
[0056]
Therefore, in the above-described embodiment, the molten metal which has air permeability and is impregnated into the inside of the preform 1 at the time of the complexation is applied to the inner peripheral surface (sand mold contact surface) of the preform 1 for complexation. Since the molten metal intrusion prevention layer 1a is formed to prevent the molten metal from entering the first sand core 13 holding the preformed body 1, the molten metal can be preformed even if the pressure of the molten metal is considerably low. By impregnating the inside of the body 1, sufficient complexity can be obtained, and the molten metal impregnated in the preform 1 can be prevented from entering the first sand core 13.
[0057]
In the above embodiment, the preformed body 1 (main body) and the fiber formed body 31 are separately formed, and they are integrated by the blow pressure when the first sand core 13 is formed. Alternatively, the preformed body 1 and the fiber formed body 31 may be integrated before forming the first sand core 13. In this case, first, as shown in FIG. 7A, for example, a slurry 42 for molding the fiber molded body 31 is put in a bottomed cylindrical container 41, and the slurry 42 is added to the slurry 42 by a suction molding device. The molded part 52 of 51 is immersed, and the fiber molded body 31 is suction-molded in the molded part 52. That is, the outer peripheral surface on one end side of the cylindrical member 53 whose one end opening is closed and the other end opening is connected to a suction device (not shown) is formed as a forming part 52. An opening 54 that opens on both the surface and the outer peripheral surface is formed. Then, when the suction device is operated in a state where the forming section 52 is immersed in the slurry 42, the fiber formed body 31 is formed by suction in the forming section 52. Subsequently, as shown in FIG. 7 (b), the molding part 52 of the suction molding device 51 is transferred to another container 43 containing a slurry 44 for forming the preform 1 (main body). By immersing in the slurry 44 and operating the suction device in the same manner as described above, the preform 1 is formed on the fiber formed body 31. When the molded product is dried and sintered, the preformed body 1 in which the molten metal permeation preventing layer 1a is integrally formed on the inner peripheral surface is obtained.
[0058]
Further, in the above embodiment, the molten metal permeation prevention layer 1a is not limited to the fiber molded body, and may be made of ceramic particles. The average particle size of the ceramic particles is preferably 10 μm or less. That is, if the average particle size of the ceramic particles is larger than 10 μm, the cell diameter becomes large, and it becomes difficult to reliably prevent the infiltration of the molten metal into the first sand core 13. As the ceramic particles, titania particles, alumina particles, zinc oxide particles and the like can be used. In this case, titania powder, alumina powder, zinc oxide (zinc white) powder or the like is mixed with water or the like to form a slurry, and the slurry is applied to the inner peripheral surface of the preform 1 with a brush or the like. 1a can be easily formed. Further, the molten metal permeation prevention layer 1a may be made of both ceramic fibers and ceramic particles. As an example, when the hot water infiltration prevention layer 1a is actually composed of both alumina short fibers and titania particles (average particle diameter of 0.3 to 0.5 μm) (mass ratio 43:57), the volume ratio is 10%. A cell having a cell diameter of about 50 μm was obtained.
[0059]
Further, in the above embodiment, the case where the composite layer 2a is formed on the inner wall of the cylinder bore of the aluminum alloy cylinder block 2 has been described. However, the present invention is not limited to the cylinder block 2, but the brake disc rotor of the vehicle braking system The present invention can also be widely applied to a case where a composite layer is formed in a part such as a valve lifter of an engine valve train or the like where composite reinforcement is required. At this time, the shape of the preform is not limited to the cylindrical shape as in the above embodiment, but may be freely set according to the shape of the portion to be compounded. The present invention is not limited to the aluminum alloy composite member such as the cylinder block 2 but can be widely applied to a light alloy composite member such as a magnesium alloy.
[0060]
【The invention's effect】
As described above, according to the preform for compounding of the present invention, the molten metal that has air permeability and is impregnated therein during the compounding enters the sand mold from the sand mold contacting surface. By forming the molten metal intrusion prevention layer for preventing the molten metal from entering, the molten metal impregnated in the preform can be prevented from infiltrating into the sand mold while obtaining sufficient composite properties.
[0061]
Further, according to the method for manufacturing a sand mold having a preformed body of the present invention, a preformed body is formed, and the preformed body having air permeability and being compounded at the sand mold contact surface of the formed preformed body at the time of compounding is formed. Forming a molten metal infiltration preventing layer for preventing the molten metal impregnated in the inside from entering the sand mold from the sand mold contact surface, and then forming the melt infiltration layer on the sand mold contact surface of the composite preform. By forming the sand mold through the blocking layer, a sand mold holding the preformed body can be easily manufactured, and the sand can be prevented from entering the preformed body during sand mold forming. . When the molten metal infiltration preventing layer is formed of a fiber molded body made of ceramic fibers, which can prevent sand constituting the sand mold from entering the preformed body at the time of sand molding, the sand is formed in the preformed body. Intrusion can be reliably suppressed, and the preformed body can be prevented from being deformed or damaged by sand to which blow pressure or the like has been applied.
[Brief description of the drawings]
FIG. 1A is a perspective view of a composite preform according to an embodiment of the present invention, and FIG. 1B is a longitudinal sectional view thereof.
FIG. 2 is a cross-sectional view showing a cylinder block of an automobile engine having a composite layer formed by compounding the preform of FIG. 1;
FIG. 3 is a cross-sectional view showing a first sand core as a sand mold provided with the preform of FIG. 1;
FIG. 4 is a cross-sectional view showing a sand core manufacturing apparatus for manufacturing a first sand core.
FIG. 5 is a schematic view showing a method for producing a first sand core.
FIG. 6 is a sectional view showing a casting device for manufacturing the cylinder block of FIG. 2;
FIG. 7 is a schematic view showing a method of integrating a preformed body and a fiber formed body before forming a first sand core.
[Explanation of symbols]
1 Preform
1a Layer for preventing infiltration of molten metal
2 Cylinder block
2a Composite layer
10 Casting equipment
13 First sand core (sand mold)
19 Decompression pipe
20 Sand core production equipment
31 Fiber molding

Claims (9)

It is held in a sand mold, and when combined with the molten metal, the air inside from the sand mold contact surface that comes into contact with the sand mold in the holding state is discharged to the sand mold by the depressurization in the sand mold and from the other surface with the discharge of the air A preform for compounding in which the molten metal is impregnated inside and compounded,
The sand mold contact surface is characterized in that a molten metal infiltration prevention layer is formed that has air permeability and prevents the molten metal impregnated therein during the complexing from entering the sand mold from the sand mold contact surface. Preform for compounding. The preform for composite according to claim 1,
The molten metal infiltration preventing layer is configured to prevent the molten metal from entering the sand mold from the sand mold contact surface when the impregnation pressure of the melt is 1 atm or less, and is a preform for composite formation. . The composite preform according to claim 1 or 2,
A preform for compounding, characterized in that the molten metal permeation prevention layer is constituted by a fiber molded body made of ceramic fibers. The preform for composite according to claim 3,
The preform for compounding, wherein the ceramic fiber is at least one selected from the group consisting of alumina fiber, silica fiber, carbon fiber, potassium titanate whisker, and aluminum borate whisker. The composite preform according to claim 3 or 4,
A preform for compounding, characterized in that the volume fraction of the ceramic fibers is at least 8% of the entire fiber compact. The composite preform according to claim 1 or 2,
A preform for compounding, wherein the molten metal permeation prevention layer is composed of ceramic particles. The preform for composite according to claim 6,
A composite preform, wherein the ceramic particles have an average particle size of 10 μm or less. It is held in a sand mold, and when combined with the molten metal, the air inside from the sand mold contact surface that comes into contact with the sand mold in the holding state is discharged to the sand mold by the depressurization in the sand mold and from the other surface with the discharge of the air On the sand mold contact surface of the composite preform in which the molten metal is impregnated and compounded, a sand mold having a composite preform for forming the sand mold by applying pressure to sand. A manufacturing method,
A step of molding the composite preform,
The molten metal that has air permeability and is impregnated inside the composite preform during the composite formation penetrates into the sand mold from the sand mold contacting surface of the formed composite preforming body. Forming a molten metal intrusion prevention layer that prevents
Forming the sand mold on the sand mold contact surface of the composite preform via the molten metal infiltration preventing layer, the method comprising the steps of: A method for producing a sand mold comprising the composite preform according to claim 8,
The composite, characterized in that the molten metal infiltration preventing layer is formed of a fiber molded body made of ceramic fibers, which can prevent sand constituting the sand mold from entering the composite preform during sand molding. Of manufacturing a sand mold having a preform for use in sand.

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