JPH10291065A - Casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the development of shrinkage hole without arranging a large capacity of feeder head, to improve the yield and to reduce the finishing manhours by setting gas generating agent in a gas generating chamber communicated with a cavity in a mold, pouring molten metal and pressurizing the molten metal with the gas generated with the heat of the molten metal. SOLUTION: A lower mold 1a, upper mold 1b and a core 5, are combined to obtain the mold 1 having the cavity 6. A small capacity of gas generating chamber 7 communicated with the upper part of a thick forming part 6a of the cavity, is arranged in this mold 1. A prescribed quantity of the gas generating agent 8 generating the gas with the heat of the molten metal is incorporated into the upper part of this gas generating chamber 7. As the gas generating agent 8, vinyl acetate, lime stone, pulp, etc., is used. Successively, the molten metal is poured in this mold 1 and the molten metal is supplied into the cavity 6 from a sprue 2 through a runner 3 and a gate 4. By this method, the gas G is generated with the heat of the molten metal M invaded into the gas generating chamber 7 to pressurize the molten metal M. Further, the development of the shrinkage hole accompanied with the shrinkage of the molten metal is effectively prevented with a small quantity of the molten metal M.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting technique for preventing shrinkage cavities due to shrinkage generated in a cooling and solidification process of a molten metal cast in a mold, and more particularly to a casting technique for a large-capacity molten metal. The present invention relates to a casting method in which a molten metal is pressurized and a shrinkage of the molten metal can be replenished without providing a molten metal.

[0002]

In gravity casting using a sand mold or a mold, or low pressure casting, the molten metal that has been cast is cooled and contracts in the process of solidification.
Shrinkage cavities may occur in the thick part of the product due to shrinkage of the molten metal. Therefore, in order to prevent the occurrence of such shrinkage cavities, a hot water is provided in the thick portion to store the excess molten metal therein, and the pressure of the hot water is applied to the molten metal in the cavity, so that the molten metal is formed. I am trying to replenish the shrinkage.

[0003] However, such a riser is completely unnecessary for a cast product, and furthermore, the height of the riser must be sufficiently secured to obtain the desired effect. There is a problem that the yield decreases. In addition, not only the number of man-hours for cutting the feeder increases, but also the position of the feeder is restricted in order to avoid interference between the cutting tool and the product, and the degree of freedom in product design is impaired. Solving the points has been an issue in conventional casting techniques.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional casting technique for preventing shrinkage cavities from being caused by a riser. Can prevent the occurrence of shrinkage nests, which can improve yield and reduce the number of finishing steps.
The purpose is to provide a casting method that can increase the degree of freedom in product design.

[0005]

A casting method according to a first aspect of the present invention is directed to a casting method in which a gas generating agent which generates gas by the heat of molten metal is housed in a gas generating chamber communicating with a cavity of a mold. The molten metal is pressurized by a gas generated from a gas generating agent, and the configuration of such a casting method is a means for solving the above-mentioned conventional problems.

[0006] As an embodiment of the casting method according to the present invention, the casting method according to claim 2 is characterized in that a gas generating chamber is formed above the cavity.
Similarly, in a casting method according to a third aspect of the present invention, the gas generating chamber is formed on a side of the cavity, and is connected to the cavity through a weir. In the sand mold, the gas generating agent is placed in a state where the gas generating agent is placed on a portion corresponding to the gas generating chamber of the model, and the gas generating agent is transferred to the mold side when the mold is removed. In a casting method according to a fifth aspect of the present invention, when forming a sand mold, an air-permeable container containing a gas generating agent at the bottom is put in a state of being placed on a model with the bottom facing upward. When the mold is removed, the container is moved to the mold side together with the gas generating agent, and the structure of such a casting method solves the above-mentioned conventional problems. It is the means of the eye.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the casting method according to the present invention, a gas generating chamber communicating with a cavity is provided in a mold, and a gas generating agent placed therein directs the molten metal toward the cavity by a gas generated by the heat of the molten metal. And pressurize it to replenish the shortage of molten metal due to solidification shrinkage and prevent the occurrence of shrinkage cavities. Types of molds include sand molds, molds, plaster molds, ceramic molds, etc. Can be applied to

The gas generating chamber is formed as a cylinder, rod, or pin having a smaller capacity than the feeder at a position corresponding to the conventional feeder, that is, above or to the side of the cavity. can do. In addition,
When the gas generating chamber is provided at a position lateral to the cavity, the gas generating chamber communicates with the inside of the cavity via a weir (corresponding to a hot-water weir).

Examples of the gas generating agent used in the present invention include resin materials such as polyvinyl chloride and polyvinyl acetate, carbonates such as calcium carbonate (limestone) and sodium carbonate (soda ash), and pulp and cotton. A material that decomposes or burns by the heat of the molten metal to generate gas, such as a fiber material, can be used, and is not particularly limited.

Such a gas generating agent is set at the uppermost position in the gas generating chamber. If the gas generating agent is a resinous material having tackiness, its viscosity is used. Thus, it can be attached to the mold wall inside the gas generating chamber. In addition, if it is powdery or granular, it can be attached to the mold wall of the gas generating chamber using an appropriate binder or adhesive, and if it is a relatively large solid, it should be embedded in the mold as it is. Is also possible.

The amount of such a gas generating agent is such that the gas generated by decomposition or combustion by the molten metal does not enter the cavity, and the shrinkage cavity is replenished by replenishing the shortage of the molten metal due to solidification shrinkage. It is necessary that the pressure be sufficient to prevent generation of gas, and it can be obtained in advance by a simple preliminary test in relation to the size of the gas generation chamber.

Further, when a sand mold is used as a mold, a gas generating agent is placed in a portion corresponding to a gas generating chamber of a model, and a mold is formed. Set the gas generating agent at the bottom of the container,
It is desirable to insert the container in a state where it is placed face down on a model, since the setting of the gas generating agent is completed simultaneously with the molding. In addition, as the above-mentioned breathable container,
For example, it is possible to use one prepared by a molding method of a shell mold using resin-coated sand. Further, a gypsum or ceramic material having an appropriate number of fine holes near the bottom, a sand box container formed by a cold box method, or another sand molding method can be used.

[0013]

In the casting method according to the first aspect of the present invention, a gas generating chamber communicating with the cavity is provided in the mold, and a gas generating agent such as a resin material is stored in the gas generating chamber. When the molten metal is filled into the cavity and further enters the gas generation chamber, the gas generating agent in the gas generation chamber generates gas by the heat of the molten metal, and the gas is generated by this gas. Since the unsolidified molten metal in the chamber is pushed to the side of the cavity and pressurizes the molten metal in the cavity, shortage due to solidification shrinkage of the molten metal in the cavity can be replenished to prevent shrinkage cavities. At this time, the molten metal in the gas generation chamber is pushed and moved by the continuously generated gas, so that the fluidity can be maintained even with a relatively small capacity, and the capacity of the gas generation chamber is reduced to the conventional capacity. An extremely excellent effect that the size can be reduced as compared with the riser and the weight yield can be improved.

In the casting method according to the second aspect of the present invention, since the gas generating chamber is formed above the cavity of the mold, the capacity of the gas generating chamber can be reduced to that of the conventional hot water. In addition to being smaller in size, there are less restrictions on the direction of die release and restrictions on the position of a thick portion requiring local pressurization, and the degree of freedom in designing a cast part is improved. In addition, the gas generation chamber portion can be easily cut off as compared with the conventional hot water, and the number of finishing steps can be reduced.
Since there is no need to consider the workability at the time of cutting the hot water, a more excellent effect that the degree of freedom in designing parts can be improved can be obtained. Similarly, in the casting method according to the third aspect of the present invention, since the gas generating chamber is formed on the side of the cavity and communicates with the cavity through the weir, similarly, a large-capacity hot water is not provided. Also, an excellent effect that the hot water effect can be improved by the pressure of the gas from the gas generating agent is exhibited.

Further, in a casting method according to a fourth aspect of the present invention, in forming a sand mold, a mold is placed in a state where a gas generating agent is placed in a portion corresponding to a gas generating chamber of a model, Since the gas generating agent is transferred to the mold side, the gas generating agent can be set at the same time as the molding, so that the gas generating agent can be easily loaded. In the related casting method, when molding a sand mold, a gas permeable container containing a gas generating agent at the bottom is placed in a state in which the gas permeable agent is placed face down on a model, and the air permeable container is filled with the gas generating agent. Together with the mold so that the gas generating agent can be easily loaded in the same manner, and it is necessary to form a part corresponding to the gas generating chamber on the model in advance. In Ino, with manufacture of the model is facilitated, set freely the position of the gas generating chamber, resulting in a further excellent effect that it is possible to change.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings.

Embodiment 1 FIGS. 1A and 1B are for explaining a first embodiment of a casting method according to the present invention.
(A) is sectional drawing which shows the shape of the casting_mold | template used for the said Example.

The mold 1 shown in the figure has a lower mold 1a and an upper mold 1
b, a sand mold comprising a gate 2, a runner 3 and a weir 4, and a cavity 6 is formed between the lower die 1a and the upper die 1b and the core 5.

A thin rod-shaped gas generating chamber 7 is formed above the thick part 6a of the cavity 6 where shrinkage cavities are expected to occur in the product casting due to solidification shrinkage of the molten metal. , A gas generating agent 8 made of a vinyl acetate resin is inserted.

When the molten metal M is poured into the gas generating chamber 7 from the gate 2 by using the mold 1 in which the gas generating agent 8 is set in the gas generating chamber 7, the molten metal M is filled with the runner 3 and the dam. 4 flows into the cavity 6. The molten metal M that has flowed into the cavity 6 further enters the gas generating chamber 7 through the thick-wall forming portion 6a, and contacts the gas generating agent 8 at the uppermost portion of the gas generating chamber 7.

The gas generating agent 8 in the gas generating chamber 7 is shown in FIG.
As shown in (b), the heat of the molten metal M decomposes to generate gas G, and the pressure of this gas causes the unsolidified molten metal M in the gas generation chamber 7 to be pressed against the cavity 6 and move, Since the shrinkage of the molten metal M in the cavity 6 which has already been filled and started to solidify is replenished, the thick part 6
a can be prevented beforehand from occurring.

The gas generating chamber 7 pressurizes the molten metal M by the pressure of the gas generated from the gas generating agent 8, so that the volume of the gas generating chamber 7 is significantly reduced as compared with the conventional hot water using only gravity. As a result, the weight yield is improved, and the gas generating chamber portion is easily separated, so that the number of finishing steps can be reduced. The degree of freedom can be improved.

Embodiment 2 FIG. 2 is a sectional view showing the shape of a mold used in a second embodiment of the casting method according to the present invention.

The mold 1 shown in the figure is a sand mold, similarly having a gate 2, a runner 3 and a weir 4, a lower mold 1a and an upper mold 1b.
A cavity 6 is formed between the core and the core 5.

In this embodiment, since the thick portion 6b of the cavity 6 where shrinkage cavities are expected to occur is located on the right side in the drawing, a feeder shape is formed on the right side of the cavity 6. A gas generating chamber 7 is formed and communicates with the cavity 6 via a weir 9. The same gas generating agent 8 as in the first embodiment is inserted at the upper end position inside the gas generating chamber 7.

Also, in this embodiment, the gas generated from the gas generating agent 8 also
Is pressed to the side of the cavity 6 and moves through the weir 9, so that the occurrence of shrinkage cavities in the thick-walled portion 6b of the cavity 6 can be effectively prevented, and the gas pressure is used. Thus, even if the gas generating chamber 7 is relatively small, a sufficient hot water effect can be obtained,
Weight yield can be improved.

In both of the above embodiments, examples in which a sand mold is used have been described. However, it is needless to say that the present invention can be applied to a mold other than a sand mold such as a mold and a plaster mold.

Embodiment 3 FIGS. 3 (a) and 3 (b) illustrate an example of a method of forming a mold in a casting method according to the present invention.
FIG. 3A is a perspective view showing a shape of a gas permeable container used for forming a gas generating chamber and setting a gas generating agent at the same time as forming a sand mold.

That is, the gas permeable container 1 shown in FIG.
Reference numeral 0 denotes a resin-coated sand molded by heating in a mold, which is a bottomed cylindrical container having a suitable air permeability, and whose inner diameter and length are the same as those of the mold according to Example 1. The dimensions are based on the dimensions of the first gas generation chamber 7.

When the upper mold 1b is formed, the gas-generating agent 8 is inserted into the bottom of the air-permeable container 10 having such a shape in advance. The casting sand is cast in this state. When the mold is removed, the upper mold 1b is completed by leaving the breathable container 10 on the side of the upper mold 1b.

FIG. 3 (b) shows the shape of the mold 1 formed by such a method. Gas is generated by the cavity of the gas permeable container 10 at a position facing the thick portion 6a of the cavity 6. A chamber 7 is formed.

In the mold 1 according to this embodiment, exactly the same effects as those of the first embodiment including the prevention of shrinkage cavities are obtained, and the gas generating chamber 7 is formed simultaneously with the molding of the mold 1 by the air permeable container 10. Is completed and the setting of the gas generating agent 8 is completed, so that the mounting workability of the gas generating agent 8 is extremely excellent. In addition, since it is not necessary to previously form a portion corresponding to the gas generating chamber on the model, it is easy to make the model, and the position of the gas generating chamber 8 is changed or added according to the occurrence of a shrinkage cavity. Can be performed freely.

Embodiment 4 FIGS. 4 (a) and 4 (b) illustrate another example of a method of forming a mold in a casting method according to the present invention.

In this embodiment, first, FIG.
As shown in (1), after placing the flask F on the mold platen B, the upper mold model P is set in the flask F.

Next, as shown in an enlarged manner in FIG.
A seating surface P formed in a portion P1 corresponding to the gas generating chamber of the model P
The gas generating agent 8 is placed on the top 2 and the molding sand is cast in this state. Then, die cutting is performed so that the gas generating agent 8 placed on the model P remains on the side of the upper die 1b.

Then, the cut upper die 1b is matched with the separately formed lower die 1a, and a mold 1 similar to that of FIG. 1A is completed.

Also in the mold 1 according to this embodiment, the same effects as those of the above embodiment including the prevention of shrinkage cavities can be obtained by the pressure of the gas generated from the gas generating agent 8, and the gas is produced simultaneously with the molding. Since the setting of the generating agent 8 is completed, the setting of the gas generating agent 8 becomes easy, and the mold is not damaged during the setting.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view showing a shape of a mold used in a first embodiment of a casting method according to the present invention. (B) It is an expanded sectional view explaining the pressurization situation of the molten metal in the casting mold shown in Drawing 1 (a).

FIG. 2 is a sectional view showing the shape of a mold used in a second embodiment of the casting method according to the present invention.

FIG. 3 (a) is a perspective view showing the shape of a gas permeable container used for molding a mold in the casting method according to the present invention. (B) It is sectional drawing which shows the shape of the casting mold molded using the gas permeable container shown to Fig.3 (a).

FIG. 4A is a cross-sectional view of a model showing a molding method of a mold in a casting method according to the present invention. (B) It is an expanded sectional view showing the state where the gas generating agent was placed on the model shown in Drawing 4 (a).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 6 Cavity 7 Gas generating room 8 Gas generating agent 10 Air permeable container M Melt P model

Claims (5)

[Claims] 1. A molten metal is injected into a gas generating chamber communicating with a cavity of a mold while a gas generating agent that generates gas by heat of the molten metal is housed therein, and the molten metal is pressurized by a gas generated from the gas generating agent. And casting method. 2. The casting method according to claim 1, wherein the gas generating chamber is formed above the cavity. 3. The casting method according to claim 1, wherein the gas generating chamber is formed on a side of the cavity, and communicates with the cavity via a weir. 4. The method according to claim 1, wherein a mold is placed in a portion corresponding to the gas generating chamber of the model when forming the sand mold, and the gas generating agent is transferred to the mold side when removing the mold. The casting method according to any one of claims 1 to 3, wherein 5. A sand mold is formed by inserting a gas permeable container containing a gas generating agent at the bottom thereof in a state of being placed on a model with the bottom portion facing upward, and removing the container together with the gas generating agent when removing the mold. The casting method according to any one of claims 1 to 3, wherein the method is shifted to a mold side.