JP2000263216A - Lost foam pattern casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain cast blow hole in a casting and also, to improve the mechanical characteristics, such as fatigue strength, tensile strength and elongation. SOLUTION: A lost foam pattern casting method is executed by forming a lost foam pattern 10 embedding a pipe and connecting cooling pipings 36, 38 with the pipe in the case of embedding this lost foam pattern 10 into molding sand and making flow of coolant into the pipe from these cooling pipings 36, 38, after pouring molten metal. In this way, the solidification of the molten metal in a cavity is quickened and the development of the cast blow hole can be restrained. Further, since the molten metal surrounding the pipe is rapidly cooled, the metallurgical structure at this portion, is made fine and the mechanical characteristics, such as the fatigue strength, tensile strength, elongation, are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a casting method using a vanishing model.

[0002]

2. Description of the Related Art A conventional vanishing model casting method is disclosed in
No. 09439. The vanishing model casting method is a technique for forming a hollow portion inside a casting, and a vanishing model used in this casting method is formed into a predetermined shape and dimensions as shown in FIG. A pipe 4 is embedded. The vanishing model 1 is the vanishing model 1
Ends 4a, 4b, 4c, 4 of pipe 4 projecting from
After d, 4e and 4f are closed with an adhesive tape or the like, they are buried in the molding sand in the flask. A sand mold is formed by hardening the casting sand. Next, a molten metal is injected from a sand gate. As a result, the vanishing model 1 is melted by the heat of the molten metal, and the part of the vanishing model 1 (cavity part) is melted.
Is replaced by the molten metal. The pipe 4 has an end 4
Since a, 4b, 4c, 4d, 4e, and 4f are supported by the casting sand (sand mold), they are held at the positions. In this state, when the molten metal is naturally cooled and solidified, a hollow portion is formed inside the casting by the pipe 4.

[0003]

However, in the above-described vanishing model casting method, since the molten metal is naturally cooled in a sand mold, solidification of a thick part of the casting is delayed, and a casting cavity is easily generated. Further, since the cooling rate of the molten metal is slow, there is a problem that the metal structure of the casting does not become fine, and it is difficult to improve the fatigue strength, the tensile strength, and the like. In view of the above, the invention described in claim 1 of the present invention prevents casting cavities even in a thick part by increasing the cooling rate of the molten metal in the cavity as compared with the molten metal in the runner part. It is an object of the present invention to improve the mechanical properties of a casting by making the metal structure finer. In addition to the object of the invention described in claim 1, the invention according to claim 2 enables a plurality of vanishing models to be placed in the casting sand by enabling the vanishing models to be accurately arranged at fixed positions in the molding sand. Its purpose is to improve productivity by allowing it to be buried in a building.

[0004]

The above object is achieved by a vanishing model casting method according to the present invention.
According to the present invention, the molten metal is poured into the sand mold to replace the lost model portion (cavity portion) with the molten metal, and then the coolant flows through the pipe passing through the cavity portion. The solidification of the molten metal is accelerated, and the occurrence of cavities can be suppressed. In addition, since the molten metal around the pipe is rapidly cooled, the metal structure in that portion becomes finer, and mechanical properties such as fatigue strength, tensile strength, and elongation are improved.

[0005] The above-mentioned other object is solved by a vanishing model casting method according to claim 2. According to the present invention, since the pipe is supported by the fixing jig when the disappearing model is embedded in the casting sand, the disappearing model can be accurately embedded at a predetermined position in the casting sand. For this reason, a plurality of disappearance models can be embedded in the casting sand, and a plurality of castings can be manufactured by one casting. Therefore, the productivity of the casting is improved.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
A vanishing model casting method according to one embodiment of the present invention will be described. The vanishing model casting method according to the present embodiment,
The present invention relates to a method of casting an aluminum casting having a through-hole in a central axial direction, and a longitudinal sectional view showing a state in which a vanishing model used in the present embodiment is buried in a molding sand of a flask in FIG. FIG. 2 shows a longitudinal sectional view of the disappearing model. The vanishing model 10 is formed into a shape equal to that of a casting by using styrofoam or the like, and an aluminum pipe 12 (hereinafter, referred to as a pipe 12) is formed in the center thereof in the axial direction as shown in FIG.
Has been passed. The pipe 12 has an inside diameter equal to the through hole of the casting, and both end portions 12t of the pipe 12 protrude from end faces 10u and 10d of the disappearing model 10 by a predetermined dimension.

Next, a description will be given of a casting flask 20 for storing casting sand for burying the disappearing model 10. The flask 20
Is a top open type container installed on a vibration table (not shown), and its bottom 20d has a double bottom. The upper bottom plate 22 of the bottom portion 20d is formed of a porous element having air permeability, and can support the molding sand S in a permeable state. A pressurization / suction chamber K is provided inside the bottom 20d, that is, between the upper bottom plate 22 and the lower bottom plate 21, and a pressurization / suction pipe 23 is connected to the pressurization / suction chamber K.
The pressurizing / suctioning pipe 23 is connected to a pressurizing device and a depressurizing device (not shown).
3 is connected to the bottom 20d of the flask 20 by an open / close valve 2.
3v is attached.

With this structure, when the open / close valve 23v is opened while the pressurizing device is operated, the inside of the pressurizing / suction chamber K is pressurized, and the air inside passes through the upper bottom plate 22 and the mold 20 Released into When the open / close valve 23v is opened while the pressure reducing device is operated, the pressure in the pressurization / suction chamber K is reduced, and the gas in the casting flask 20 is removed from the upper and lower plates 2
2 and is sucked into the pressure / suction chamber K.
In the casting flask 20, the vanishing model 10 is located above the upper bottom plate 22.
Is buried therein. Further, at a position higher than the upper bottom plate 22 by a predetermined level, a receiving stand 24 for supporting a fixing jig 30 described later is fixed in a state protruding from the inner wall surface of the casting frame 20.

Next, a fixing jig 3 for fixing the disappearing model 10
0 will be described. The fixing jig 30 is a jig for positioning the two vanishing models 10 at predetermined positions in the casting flask 20 and supplying cooling water to the pipes 12 of the vanishing models 10. Upper plate 32u supporting
And a lower plate 32d that supports the lower end surface 10d of the vanishing model 10. The upper plate 32u and the lower plate 32d are formed with openings 32h through which the pipes 12 of the disappearing model 10 pass.

The upper plate 32u and the lower plate 32d are connected at the center by a connecting pipe 34. The connecting pipe 34 connects the two plates 32u and 32d by adjusting the distance between the upper plate 32u and the lower plate 32d according to the length of the disappearance model 10, and has a passage 34r formed therein for flowing cooling water. I have. Further, a flange 34f to be gripped by the robot hand 40 is formed at an upper portion of the connection pipe 34. Further, the connecting pipe 3 is provided at the upper end of the connecting pipe 34.
A fitting 34x for connecting the water cooling hose 42 to the water cooling hose 42 is attached.

A lower collecting pipe 36 is connected to a lower end of the connecting pipe 34. The lower collecting pipe 36 dissipates the cooling water supplied from the connecting pipe 34 to the pipe 12 of the model 10.
And is formed in a substantially T-shape. The central inlet 36a of the lower collecting pipe 36 is connected to the connecting pipe 34, and the two outlets 36b on both sides are connected to the lower side of the pipe 12 of the disappearing model 10, respectively. Further, an upper collecting pipe 38 is connected to the upper side of the pipe 12 of the disappearing model 10. The upper collecting pipe 38 is a pipe for guiding the cooling water flowing out of the pipe 12 of the disappearing model 10 to the drain pipe 44, and is formed in a substantially L shape. Two inflow ports 38a formed on the lower side of the upper collecting pipe 38 are connected to the upper side of the pipe 12 of the vanishing model 10, respectively, and a collecting outlet 38b formed on the upper end portion is connected to a drain pipe via a fitting 38x. 44. That is, the connection pipe 3
4. The lower collecting pipe 36 and the upper collecting pipe 38 correspond to the cooling pipe of the present invention.

Next, the vanishing model casting method according to the present embodiment will be described in the order of steps. First, when forming the disappearing model 10 with styrene foam or the like, a pipe 1 is attached to the disappearing model 10.
2 and the disappearance model 10 and the pipe 12 are integrally formed as shown in FIG. Next, two disappearance models 1
At 0, a runner model 15 made of styrene foam is joined with an adhesive. When the runner model 15 is connected to the vanishing model 10 in this way, a refractory is applied to the surface of the vanishing model 10. Refractory is for preventing skin roughness cast during pouring, those kneaded with Si0 ₂ in water glass or the like is preferably used.

Next, two vanishing models 10 coated with refractory are set between the upper plate 32u and the lower plate 32d of the fixing jig 30, and the upper plate 32u and the lower plate 32d are connected by the connecting pipe 34. Are linked. Furthermore, the outlet 36b of the lower collecting pipe 36 is connected to the pipe 12 of the disappearing model 10 protruding from the opening 32h of the lower plate 32d, and the central inlet 36a of the lower collecting pipe 36 is connected to the connecting pipe 34. . Also, the inlet 38 of the upper collecting pipe 38 is connected to the pipe 12 of the vanishing model 10 protruding from the opening 32h of the upper plate 32u.
a is connected.

When the preparation for burying the lost model 10 is completed in this way, the flange 34f of the connecting pipe 34 of the fixing jig 30 is gripped by the hand 40 of the robot, and the lost model 10 is conveyed to the position of the flask 20. You. Next, the flask 20
Of the pressurizing / suction chamber K is pressurized, and the air in the pressurizing / suction chamber K passes through the upper and lower plates 22 to form Will be released. Thereby, the casting sand S in the casting flask 20 is fluidized. Next, the robot grips the flange 34 f of the fixing jig 30 and embeds the fixing jig 30, the disappearance model 10 and the runner model 15 in the casting sand S of the flask 20. Here, the disappearing model 10 and the runner model 15 are fixed to the fixing jig 3.
By being supported by the cradle 24 of the flask 20, it is held at a predetermined position in the flask 20.

In this manner, the lost model 10 and the like are
, The on-off valve 23v is closed and the pressurizing device stops. Further, the vibration table is operated to apply vibration to the casting flask 20, and the casting sand S is filled into every corner of the disappearing model 10. As a result, a sand mold is formed in the flask 20. A water cooling hose 42 is connected to the fitting 34x of the connecting pipe 34 of the fixing jig 30, and a drain pipe 44 is connected to a collecting outlet 38b of the upper collecting pipe 38.
Is connected. The vibration step may be omitted depending on the shape of the vanishing model 10 and the layer of the refractory applied to the vanishing model 10 in some cases.

Next, the pressure reducing device is operated to open and close the opening / closing valve 23v, and the casting sand S is depressurized and solidified by sucking the inside of the casting flask 20, and the gas in the casting flask 20 is released from the upper bottom plate. From 22, it is sucked into the pressure / suction chamber K. Then, in this state, the molten metal is poured into the sand mold. When the molten metal is poured, the runner model 15 is heated by the heat of the molten metal.
Then, the disappearing model 10 is melted, and the portion (cavity portion) of the disappearing model 10 is replaced with the molten metal. Since the pipe 12 is supported by the fixing jig 30, it is held at that position. When the molten metal is filled in the sand mold, cooling water is flown into the pipe 12 of the disappearance model 10 immediately before the molten metal solidifies. Here, the water temperature, flow rate, and water pressure of the cooling water are controlled to appropriate values in accordance with the solidification state of the molten metal. When a predetermined time has passed in this way and the molten metal solidifies, a hollow portion is formed inside the casting by the pipe 4.

When the casting is formed, the water cooling hose 42 is removed from the connecting pipe 34 of the fixing jig 30, and the drain pipe 44 is removed from the collecting outlet 38 b of the upper collecting pipe 38. Next, the decompression device is stopped, the pressure device is operated, and the
In a state where the casting sand S in the flowing state, the casting and the fixing jig 30
Is taken out of the casting sand S by the robot. Next, the end of the pipe 12 protruding from the casting is cut and removed in a post-processing step. The pipe 12 in the casting is used as a part of the casting as it is.

As described above, according to the vanishing model casting method according to the present embodiment, after pouring into a sand mold to replace the portion of the vanishing model (cavity portion) with the molten metal, the pipe 12 passing through the cavity portion Since the cooling water flows into the cavity, solidification of the molten metal in the cavity is quicker than in the molten metal in the runner portion, and the occurrence of a cavity can be suppressed. Further, since the molten metal around the pipe 12 is quenched, the metal structure in that portion becomes finer, and mechanical properties such as fatigue strength, tensile strength, and elongation are improved. Further, when the disappearing model 10 is embedded in the casting sand S, the pipe 12 is supported by the fixing jig 30, so that the disappearing model 10 can be accurately embedded at a predetermined position in the casting sand S. For this reason, a plurality of vanishing models 10 can be embedded in the casting sand S, and a plurality of castings can be manufactured by one casting. Therefore, the productivity of the casting is improved.

In the vanishing model casting method according to the present embodiment, an example has been shown in which cooling water is flown through the pipe 12 of the vanishing model 10 to cool the molten metal. However, other coolants, such as air and gas, are used. It is also possible to cool the molten metal by flowing.

FIG. 3 shows an example in which a pipe 54 is used in a hollow portion 52 constituting a pin boss portion of the piston 50 when the piston 50 is cast. Unnecessary portions (dotted line portions) of the pipe 54 are cut and removed in a later step. The pin boss portion of the piston 50 requires high cycle fatigue strength due to the reciprocating motion of the connecting rod. However, usually, the pin boss portion is often exposed to a high temperature of 180 ° C. or more, so that it is necessary to maintain high strength, and it has been difficult to reduce the weight by stealing meat.
However, according to the vanishing model casting method according to the present embodiment,
Since the strength around the pipe 54 is improved, the weight can be reduced without changing the components of the molten metal as compared with the conventional casting method.

FIG. 4A shows the dimensions of the secondary dentite arm spacing (secondary DAS) of the metal structure of the casting formed by the conventional casting method and the casting by the vanishing model casting method according to the present embodiment. It is the graph which compared the dimension of the secondary DAS of the metal structure of a casting. Secondary DA of conventional castings
While S is about 60 μm, the secondary DAS of the casting in the present embodiment is about 10 μm, which indicates that the metal structure is sufficiently fine. FIG. 4 (B) shows the secondary DAS and
10 ⁷ times is a graph showing the relationship between the ambient temperature fatigue strength, secondary DAS on the horizontal axis represents the 10 ⁷ times normal temperature fatigue strength on the vertical axis. As is apparent from this graph, casting the metal structure is improved 10 ⁷ times normal temperature fatigue strength if miniaturization.

[0022]

According to the present invention, the solidification of the molten metal in the cavity is accelerated, so that the formation of cavities can be suppressed.
The metal structure becomes finer, and mechanical properties such as fatigue strength, tensile strength, and elongation are improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a state in which a vanishing model used in one embodiment of the present invention is embedded in molding sand of a flask.

FIG. 2 is a longitudinal sectional view of the vanishing model according to one embodiment of the present invention.

FIG. 3 is a sectional view of a piston formed by a vanishing model casting method according to an embodiment of the present invention.

FIG. 4 (A) is a view showing the dimensions of a secondary dentite arm spacing (secondary DAS) of a metal structure of a casting formed by a conventional casting method, and molding by a vanishing model casting method according to the present embodiment. 3 is a graph comparing the metal structure of a cast metal with the size of secondary DAS. FIG. 4 (B) shows the secondary DA
It is a graph showing the relationship between S and 10 ⁷ times normal temperature fatigue strength.

FIG. 5 is a cross-sectional view illustrating a vanishing model used in a conventional vanishing model casting method.

[Explanation of symbols]

 S Cast sand, sand mold 10 Elimination model 12 Pipe 20 Casting frame 30 Fixing jig 34 Connecting pipe (Cooling pipe) 36 Lower collecting pipe (Cooling pipe) 38 Upper collecting pipe (Cooling pipe) 42 Water cooling hose 44 Drain pipe

Claims (2)

[Claims] When a lost model in which a pipe is embedded is formed and the lost model is embedded in casting sand, a cooling pipe is connected to the pipe, and after pouring, a coolant is supplied from the cooling pipe to the pipe. A vanishing model casting method characterized by flowing. 2. The vanishing model casting method according to claim 1, wherein the pipe is supported by a fixing jig when the vanishing model is buried in molding sand.