JPH1190583A - Full-mold casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly exhaust gas generated from a lost foam pattern to out of a mold. SOLUTION: A pattern 1 composed of a losable synthetic resin foamed body is embedded into the mold and successively, the molten metal 8 poured from a sprue 2 is supplied into the upper part of the pattern 1 through runners 31, 32 and gates 4 and the pattern 1 is replaced into the molten metal 8 to produce a casting. At the time of using A for the total cross sectional area of the sprues 2, B for the total cross sectional area of the runners 32 and C for the total cross sectional area of the gates 4, these area have the relation of A<B<C. At least one side of the upper surface 321 of the runner 32 or the upper surface 41 of the gates 4, gas vent holes 51, 52 communicated with the air, are arranged. At the time of using D for the total cross sectional area of the gas vent holes 51, 52, these area are D<=A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a full mold casting method.

[0002]

2. Description of the Related Art A full mold casting method or a vanishing model casting method (hereinafter collectively referred to as a full mold casting method) is a model made of a substance which evaporates and disappears when heated, such as expanded polystyrene. , Efficient synthetic resin foam is used. Then, bury the model in the mold,
A molten metal obtained by melting metal is poured into a mold. This is a casting method in which the model is vaporized and lost by the heat of the molten metal, and the model is replaced with the molten metal to produce a casting.

[0003] Conventionally, in a generally practiced full mold casting method, there are three types depending on a supply position of a molten metal to a model burying portion. That is, there are a top gate type that supplies molten metal from above the model, a bottom gate type that supplies molten metal from the bottom of the model, and a side gate type that supplies molten metal from the side surface of the model. In either case, the molten metal is injected from the gate and supplied to the model via a runner and weir.

[0004]

In the conventional full mold casting method described above, it is a very important technical problem how to smoothly discharge the gas generated when the model disappears out of the mold. I have. That is, the gas generated by the vaporization of the model has a volume of 10 to 20 times the volume of the model.
May be doubled. If this large amount of gas cannot be released sufficiently outside the mold, the quality of the casting will be greatly reduced.

As means for releasing the above gas, conventionally,
A method has been adopted in which a coating mold having high air permeability is provided in advance on the outer peripheral surface of the model, and gas is extruded from the coating mold into the mold. However, in the degassing method using this coating mold, the large amount of gas generated above cannot be released sufficiently. In particular, in a casting having a large ratio of casting weight / surface area (so-called modulus), the outflow area from the outer peripheral coating layer becomes narrow, and it becomes more difficult to sufficiently release gas. Therefore, there is a limit to solving this problem only by improving the coating mold.

Conventionally, in the case of a top gate type,
For example, as disclosed in Japanese Patent Publication No. 51-3686, it has been proposed to provide a gas vent at the upper part of the runner. However, there is a problem in that simply providing the gas release portion may make it impossible to perform sufficient gas release due to the molten metal filling the runner.

In the case of a side gate type, as disclosed in Japanese Utility Model Publication No. 49-22504, for example,
It has been proposed to provide a gas venting pipe inside the model. However, in this case, there is a problem that the generated gas is not released to the outside at a sufficient speed because the gas venting portion stops at the upper end of the model.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a full mold casting method capable of smoothly discharging gas generated from a lost model to the outside of a mold.

According to a first aspect of the present invention, a model made of a foam made of a fugitive synthetic resin is buried in a mold, and then molten metal injected from a gate is supplied to an upper portion of the model through a runner and a weir.
In the top gate type full mold casting method for producing a casting by replacing the model with the molten metal, a total cross-sectional area of the gate is A, a total cross-sectional area of the runner is B, and a total cross-sectional area of the weir is C. And A and B are in a relationship of A <B <C, and at least one of the upper surface of the runner and the upper surface of the weir is provided with a gas vent path to the atmosphere, and
The full mold casting method is characterized in that when the total cross-sectional area of the gas venting path is D, D ≦ A.

The most remarkable point in the present invention is that the cross-sectional areas A, B, and C of the gate, runner, and weir are sequentially increased, that is, as the molten metal progresses, the cross-section of the path of the molten metal increases. That is, the cross-sectional area is broadened as it were.

The gate, runner, and weir are elements constituting a gate system for guiding the molten metal to a model portion (cavity) in the mold. And the gate plays the role of receiving the molten metal and guiding it to the runner. The runner is a molten metal passage arranged in a substantially horizontal direction, and serves to distribute the molten metal to a plurality of weirs. The weir serves to supply the molten metal distributed from the runner to the model. These are provided so that the total cross-sectional area of the runner is larger than that of the gate and that of the weir is larger than that of the runner.

In addition, a gas venting path to the atmosphere is provided on at least one of the upper surface of the runner or the upper surface of the weir. Here, the upper surface of the weir means, for example, the upper surface of a horizontal portion of the weir when the weir is extended horizontally from the runner and bent down in an L-shape (see FIG. 1).
In this case, it is preferable that the gas vent path is provided coaxially with the vertical portion of the weir. Thereby, degassing can be performed more smoothly.

It is preferable that the cross section of the runner is vertically long, that is, the height is larger than the width. Thereby, when the gas vent is provided on the upper surface of the runner, it becomes easier to secure a gas passage for guiding gas to the gas vent inside the runner.

The total cross-sectional area D of the gas venting path has a relation of D ≦ A with the total cross-sectional area A of the gate. The total cross-sectional area D of the gas venting path is larger than the total cross-sectional area A of the gate (D>
In case A), there is a problem that air enters from the gas venting path, and if, for example, the flow rate of the gas is set to 10 times the flow rate of the molten metal, in the worst case, detonation air is formed. In addition,
It is preferable that the lower limit value of the total sectional area D of the gas venting path is set so that the internal pressure of the gas can be maintained lower than the molten metal injection head (effective casting height).

Next, the operation of the present invention will be described. In the full mold casting method according to the present invention, the gas vent path is provided, and the total cross-sectional area of the gate, the runner, and the weir is set to be divergent in the traveling direction of the molten metal. Therefore, the gas generated from the model portion by the injection of the molten metal is smoothly discharged to the outside of the mold through the weir, the runner, and the gas vent.

That is, in the runner and the weir, a sectional area larger than the space occupied by the molten metal supplied from the gate is ensured due to the above-mentioned sectional area relation. Therefore, in the runner and the weir at the time of pouring the molten metal, an extra space other than the molten metal passage is obtained, and this can be secured in the gas passage. And when the injected molten metal reaches the model,
A large amount of gas is generated and attempts to escape to low pressure areas. At this time, the gas passage is secured in the weir. Therefore, the generated gas enters the gas passage in the weir with almost no resistance.

If the weir is provided with a gas venting path, the generated gas directly reaches the gas venting path from the gas passage in the weir and passes through the gas venting path to the outside of the mold. Released smoothly. In addition, when the runner is provided with a gas vent, the generated gas smoothly enters the gas passage secured in the runner from the gas passage in the weir, and then flows out of the mold through the gas vent. Released outside.

As described above, in the present invention, not only is the above-described gas vent path provided, but also the total cross-sectional areas B and C of the weir and the runner leading to the gas vent path are defined by the total cross-sectional area A of the gate. In the relationship, A <B <C is set. Therefore, the gas passage can be reliably secured in the weir and the runner, and the generated gas can be easily led out to the gas vent passage. Further, since the upper limit value of the total cross-sectional area D of the gas venting path is limited as described above, there is no problem of formation of detonation due to reverse inflow of air.

Therefore, according to the present invention, it is possible to provide a top gate type full mold casting method capable of smoothly discharging the gas generated from the disappearing model to the outside of the mold.

Next, as in the second aspect of the present invention,
It is preferable that B and C have a relationship of 1.5A ≦ B ≦ 2A and 2A ≦ C ≦ 3A. That is, the total cross-sectional area B of the runner is preferably in the range of 1.5 to 2 times the total cross-sectional area A of the gate. In the case of 1.5A> B, there is a problem that the gas flow path may not be sufficiently secured. On the other hand, in the case of B> 2A, the amount of molten metal used in the gate system increases and the yield decreases. There is.

The total cross-sectional area C of the weir is preferably within a range of two to three times the total cross-sectional area A of the gate. 2A> C
In the case of (1), there is a problem that the gas flow path may not be sufficiently secured. On the other hand, in the case of C> 3A, there is a problem that the molten metal used for the gate system increases and the yield decreases.

Further, as in the third aspect of the present invention, it is preferable that the gas vent path is constituted by a hole provided in the mold or a fire-resistant pipe buried in the mold. For example, in the case of a mold using caking sand, by providing a hole in the mold, it is possible to obtain a degassing path that does not lose its shape when releasing gas. Further, in the case of a mold using non-caking sand, the use of the above-mentioned refractory pipe makes it possible to obtain a gas venting path which does not lose its shape when releasing gas.

Next, there is the following invention as a so-called bottom gate type or side gate type full mold casting method. That is, a model made of a foam made of a fugitive synthetic resin is buried in a mold, and then the molten metal injected from a gate is supplied to the bottom or side surface of the model through a runner or weir, and the model is replaced with the molten metal. In the bottom gate type or side gate type full mold casting method for producing a casting by casting, a through hole is provided inside and under the model, and a gas passing through the atmosphere is provided above the through hole. There is a full mold casting method in which E ≦ A, where E is the total cross-sectional area of the through hole, and A is the total cross-sectional area of the sprue, where the drainage paths are connected.

The most remarkable point in the present invention is that a through hole is provided inside the above-mentioned model so as to penetrate the model up and down.
In addition, a gas venting path leading to the atmosphere is connected to the upper part of the through hole.

If the total cross-sectional area of the through hole is E and the total cross-sectional area of the gate is A, then E ≦ A. The total cross-sectional area E of the through hole is larger than the total cross-sectional area A of the gate (E> A)
In this case, there is a problem that air flows backward from the gas venting path, and there is a danger of forming explosive air. The lower limit of the total cross-sectional area E of the through-hole is preferably set so that the gas pressure can be maintained lower than that of the molten metal head in order to prevent the molten metal from being jetted back.

Next, the operation of the present invention will be described. In the present invention, the through hole is provided in the model. In the bottom gate type and the side gate type, the model sequentially disappears from the vicinity of the bottom of the model to generate gas. Therefore, the generated gas first enters the through hole inside the model and rises upward.

The gas venting path is connected above the through hole. Therefore, the generated gas that has entered the through hole directly enters the gas venting path as it is, and is smoothly discharged to the outside of the mold. Therefore, the generated gas can be released more smoothly than before. In addition, since the upper limit value of the total cross-sectional area E of the through hole is limited as described above, the problem of forming detonation does not occur.

Therefore, according to the present invention, it is possible to provide a bottom gate type or side gate type full mold casting method capable of smoothly discharging the gas generated from the disappearing model to the outside of the mold.

Further, as in the invention of claim 5, it is preferable that the gas vent path is constituted by a hole provided in the mold or a fire-resistant pipe buried in the mold. Thereby, the same effect as above can be obtained.

Further, as in the invention of claim 6, the through hole can be formed by arranging a hole penetrating up and down or a vanishable pipe inside the model. In other words, it is possible to easily form a through hole by drilling a hole in the model later, or by preparing a pipe that constitutes a through hole in advance and arranging this in a predetermined position when molding the model. it can. This can facilitate the formation of the through hole. Further, the pipe needs to have a vanishing property that disappears due to the heat of the molten metal, similarly to the model body. The pipe having the same material or different material as the model can be used as the pipe having a dissipating property.

Also, as in the invention of claim 7, it is preferable that the runner and the weir are made of a fugitive material. As a result, the cost of the gate system can be reduced. Also, various materials can be used as the emissive material as in the case of the model material. In addition, it is preferable that the runner and the weir in this case are configured by providing a fire-resistant coating mold on the outer periphery of the above-mentioned fugitive material. Thereby, it is possible to prevent the inner surface shapes of the runner and the weir formed by the disappearance of the erodible material at the time of pouring the molten metal from being collapsed by the flow of the molten metal.

Further, as in the invention of claim 8, it is preferable that a hollow portion is provided inside the runner and the weir along the flow direction of the molten metal. This makes it possible to smoothly discharge the gas generated by the evaporable material constituting the runner and the weir, and to easily hollow the runner and the weir.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 A top gate type full mold casting method according to an embodiment of the present invention will be described with reference to FIGS. In the full mold casting method of this example, as shown in FIG.
A model 1 made of a fugitive synthetic resin foam is used as a mold (not shown).
Buried inside. Next, the molten metal 8 injected from the gate 2 is poured into a lower runner (horizontal section) 31, an upper runner (vertical section) 32,
It is supplied to the upper part of the model 1 through the weir 4 and the casting is manufactured by replacing the model 1 with the molten metal 8.

Assuming that the total cross-sectional area of the gate 2 is A, the total cross-sectional area of the upper runner 32 is B, and the total cross-sectional area of the weir 4 is A <B <C. Further, on the upper surface of the runner 32 and on the upper surface of the weir 4, gas venting paths 51 and 52 communicating with the atmosphere are provided. When the total cross-sectional area of the gas vent paths 51 and 52 is D, D ≦ A.

Hereinafter, this will be described in detail. Model 1 in this example is
As shown in FIG. 1, it has a box shape and has the same shape as the casting to be obtained. The size of the model 1 allows for thermal expansion and contraction. In addition, model 1
Is made of expanded polystyrene in this example.

On the upper surface of the model 1, a spout 2 and a lower runner 3
A gate system consisting of an upper runner 32 and a weir 4 is provided.
The gate 2 is a refractory hollow cylinder as shown in FIG. 1 and is connected to one end of a lower runner 31. The sectional area A of the gate 2 is determined by the amount of molten metal to be supplied and the casting height.

As shown in FIG. 1, the runner has a lower runner 31.
And the upper runner 32 are combined. The lower runner 31 has the above-mentioned gate 2 connected to the upper surface of one end, and the upper runner 32 is connected to the upper surface of the other end. The upper runner 32 is provided at the upper center of the model 1 so as to have a length corresponding to the entire width.

Further, as shown in FIGS. 2B and 2C, the lower runner 31 and the upper runner 32 are made of a polystyrene foam 61.
The outer peripheral surface is coated with a fire-resistant coating mold 62. At the center of the expanded polystyrene 61, a hollow portion 63 is provided along the longitudinal direction.

As shown in FIG. 1, a total of six weirs 4 are arranged at predetermined intervals in consideration of the flowability of the molten metal.
Each weir 4 extends horizontally from the side wall 322 of the upper runner 32 and has a tip bent downward to connect to the model. As shown in FIG. 2 (d), the weir 4 is also made of a polystyrene foam 61, the outer peripheral surface of which is coated with a fire-resistant coating mold 62, and the center of the polystyrene foam 61 is hollow. A part 63 is provided.

Then, as shown in FIG.
Gas vent paths 51 and 52 are provided at two locations on the upper surface 321 and the upper surface 41 of one weir 4. These degassing paths 51 and 52 are constituted by refractory pipes 510 and 520. In addition, the model 1 and the above-mentioned gate system are buried with mold sand.

The total cross-sectional area of each part in the gate system will be described with reference to FIG. As shown in the figure, the total cross-sectional area B 'of the lower runner 31 (the area surrounded by the coating mold 62 in the same figure (b)) is larger than the total sectional area A of the spout 2 (the same figure (a)). And the total cross-sectional area B of the upper runner 32 ((c) in FIG.
(The area surrounded by the coating mold 62) is larger than B ′.

The total cross-sectional area C obtained by combining six cross-sectional areas C ′ of the weir 4 (the area surrounded by the coating mold 62 in FIG.
The total area B of the upper runner 32 is further increased.
That is, each total sectional area has a relation of A <B ′ <B <C,
It spreads out in the direction of the molten metal.

In this embodiment, the total cross-sectional area B of the upper runner 32 is 1.5 times the total cross-sectional area A of the sprue 2 and the total cross-sectional area C of the weir 4.
Is set to twice A. In addition, degassing paths 51 and 5
The total cross-sectional area D of the gate 2 is smaller than the total cross-sectional area A of the gate 2.

Next, in the casting operation, first, the molten metal 8 is poured from the gate 2. In this example, a molten metal for cast iron is injected. The injected molten metal 8 enters the lower runner 31 from the gate 2 and changes its course in the horizontal direction. Next, the molten metal 8 is pushed up from the lower runner 31 to the upper runner 32, and changes course in the horizontal direction at the upper center of the model 1. Next, the molten metal 8 is distributed from the upper runner 32 to each weir 4 and supplied to the model 1 portion.

In this embodiment, the total cross-sectional areas A, B ', B, and C of the respective portions are sequentially increased along the path of the molten metal as described above. Therefore, the gate 2 and the lower runner 3
The molten metal 8 supplied via the upper runner 32 and the weir 4
Flows without satisfying all the cross-sectional areas of. That is,
As shown in FIGS. 3A and 3B, a state in which gas passages 329 and 49 are formed inside the upper runner 32 and each weir 4 in addition to the spaces 328 and 48 occupied by the molten metal 8 is maintained. .

Next, when the molten metal 8 reaches the model 1, the model 1 is vaporized by heat received from the molten metal 8 and generates a large amount of gas 9. This gas 9 is supplied to the weir 4 and upper runner 3
The gas easily reaches the gas venting paths 51 and 52 through the gas passages 329 and 49 in FIG. Degassing path 51,5
The gas 9 arriving at 2 is smoothly discharged to the outside of the mold through the gas 9 and burns outside the mold.

As described above, in the present embodiment, the gas vent paths 51 and 52 are provided, and the cross-sectional area of each part of the gate system is widened in the traveling direction of the molten metal as described above. Therefore, the gas passages 329 and 49 can be secured in the weir 4 and the upper runner 32, and the gas venting passage 5 is provided.
The gas 9 can be easily led to 1,52. Therefore,
The gas 9 can be smoothly discharged to the outside from the degassing paths 51 and 52. Further, the total cross-sectional area D of the degassing passages 51 and 52 is smaller than the total cross-sectional area A of the gate 2. Therefore, there is no adverse effect that air flows backward from the outside and detonation air is formed in the mold.

Embodiment 2 This embodiment is a specific example of a bottom gate type full mold casting method. That is, as shown in FIG. 4, in this example, the model 1 made of the fugitive synthetic resin foam is embedded in the mold 7. Next, the molten metal 8 injected from the gate 2 is poured into the runner 3, weir 4
To the bottom portion 13 of the model 1, and the casting is manufactured by replacing the model 1 with the molten metal 8.

The model 1 is provided with a through hole 15 penetrating vertically therethrough, and a gas venting path 53 leading to the atmosphere is connected to the upper part of the through hole 15. When the total cross-sectional area of the through hole 15 is E and the total cross-sectional area of the gate 2 is A, E ≦ A
It is.

The model 1 of this example is made of expanded polystyrene and has the same shape as the casting to be obtained as in the first embodiment. Also, inside Model 1
Two through holes 15 are provided. The through hole 15 is provided by hollowing the model 1 up and down.

On the bottom of the model 1 are a spout 2, a runner 3, a weir 4
The sprue system is connected. The gate 2 is a refractory cylinder, as shown in FIG. As shown in FIG. 4, the runner 3 is disposed in a horizontal direction, and two weirs 4 are erected from the upper surface thereof.

The weir 4 is connected to the position where the through hole 15 is formed in the model 1 as shown in FIG. The runner 3 and the weir 4 are made of polystyrene foam as in the first embodiment, and the outer peripheral surface thereof is coated with a fire-resistant coating.

Further, above the model 1, two gas vent paths 53 made of a refractory material are provided. The gas venting path 53 is provided directly above the through hole 15 of the model 1 and connected to the same. In addition, the upper end 536 of the degassing path 53
Is exposed above the mold 7. Further, the total cross-sectional area E of the through hole 15 in this example is smaller than the total cross-sectional area A of the gate 2.

Next, in the casting operation, first, the molten metal 8 is poured from the gate 2. The molten metal 8 is made of an alloy for cast iron as in the first embodiment. The injected molten metal 8 enters the runner 3 while evaporating the runner 3 from the gate 2, and changes the course in the horizontal direction. Next, the molten metal 8 is pushed up from the runner 3 while evaporating the weir 4, and reaches the bottom 13 of the model 1.

Next, when the molten metal 8 reaches the model 1, the model 1 is vaporized by the heat received from the molten metal 8 and generates a large amount of gas 9. The gas 9 rises through the through hole 15 in the model 1 together with the gas vaporized from the gate 3 and the weir 4, and is further discharged directly to the outside of the mold 7 through the gas release path 53, and burns outside. I do.

As described above, in this example, the through hole 15 is provided inside the model 1 and the gas venting path 53 is connected above the through hole 15. Therefore, it is not necessary to vent the gas through the mold as in the related art, and the gas 9 can be directly and smoothly discharged to the outside of the mold 7. Further, since the total cross-sectional area E of the through hole 15 in this embodiment is smaller than the total cross-sectional area A of the gate 2, there is no adverse effect of the formation of detonation in the mold due to the reverse flow of air.

[0057]

As described above, according to the present invention, it is possible to provide a full mold casting method capable of smoothly discharging the gas generated from the disappearing model to the outside of the mold.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a model and a gate system according to a first embodiment.

FIG. 2 is an explanatory view showing a cross-sectional shape of each part of a gate system in the first embodiment.

FIG. 3 (a) an upper runner according to the first embodiment;
(B) Explanatory drawing which shows the state at the time of molten metal injection of a weir.

FIG. 4 is an explanatory diagram showing a configuration of a model and a gate system in a second embodiment.

[Explanation of symbols]

 1. . . Model, 15. . . 1. through-hole, . . Gate, 3 . . Yudo, 31. . . Lower runner, 32. . . Upper runner, 4. . . Weirs, 51, 52, 53. . . 6. degassing path; . . 7. a mold; . . Molten metal, 9. . . gas,

Claims (8)

[Claims] 1. A model made of a foam made of a fugitive synthetic resin is buried in a mold.
In a top gate type full mold casting method for supplying a casting through the weir to the upper part of the model and replacing the model with the molten metal to produce a casting, the total cross-sectional area of the gate is A, and the total cross-sectional area of the runner is A B, when the total cross-sectional area of the weir is C, they are in a relationship of A <B <C, and at least one of the upper surface of the runner and the upper surface of the weir is provided with a gas venting passage leading to the atmosphere. And D is the total cross-sectional area of the gas venting path, and D ≦ A. 2. The method according to claim 1, wherein said A, B, C,
Is a full mold casting method characterized by having a relationship of 1.5A ≦ B ≦ 2A and 2A ≦ C ≦ 3A. 3. The full mold casting method according to claim 1, wherein the gas venting path is constituted by a hole provided in the mold or a fire-resistant pipe buried in the mold. 4. A model made of a fugitive synthetic resin foam is buried in a mold, and then a molten metal injected from a gate is poured into a runner,
In a bottom gate type or side gate type full mold casting method in which a casting is manufactured by supplying the molten metal to the bottom or side portion of the model through a weir and replacing the model with the molten metal, the inside of the model is placed above and below the model. A through-hole is provided, and a gas venting path leading to the atmosphere is connected to the upper part of the through-hole. The total cross-sectional area of the through-hole is E, and the total cross-sectional area of the gate is A. A full mold casting method, wherein E ≦ A. 5. The gas venting path according to claim 4, wherein:
A full mold casting method comprising a hole provided in a mold or a refractory pipe buried in the mold. 6. The full mold according to claim 4, wherein the through hole is formed by disposing a hole penetrating up and down or a fugitive pipe inside the model. Casting method. 7. The method according to claim 1, wherein:
A full mold casting method, wherein the runner and the weir are made of a fugitive material. 8. The full mold casting method according to claim 7, wherein a hollow portion is provided inside the runner and the weir along a flow direction of the molten metal.