JPS606241A - Pattern for forming of casting mold - Google Patents

Abstract

PURPOSE:To render porosity to the entire part of a mold by casting a slurry material formed by mixing ferrous powder, ceramics and a binder having volatility in the process of curing at a prescribed ratio onto a prototype pattern and molding the material. CONSTITUTION:A prototype pattern 4 is mounted on a plate material 5 and the outside circumference thereof is enclosed with a frame body 6. A mold parting material is coated on the surface of the pattern 4 and the body 6. A slurry material 1 formed by using ferrous powder and ceramic powder as aggregate and mixing a binder having volatility in the process of curing therewith at (1-5): (1-5):1 by weight is cast into the frame body and is oscillated or squeezed so that the material 1 is spread to a uniform thickness along the prototype pattern plate. The material 1 is rested for prescribed time to cure and thereafter the cured and molded pattern 2 is removed from the body 6 and the pattern 4. The molded pattern 2 is then dried, by which a casting mold 3 for molding consisting of the porous structure having numerous micropores scattering therein is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a model for mold making, mainly a model used in the known vacuum molding method.

One of the special molds is vacuum mold (V process). This vacuum molding process generally involves mounting a model on a suction box, covering the model with a plastic film that has been heated and softened, and then reducing the pressure inside the suction box to make the film densely layered on the surface of the model. It is made by filling a molding frame with molding sand, covering the molding sand with a film, and eliminating the air in the molding sand in the frame.

In such a vacuum mold, there is no ffl on the mold surface, or ffi of the plastic film to the m mold! The suction power of the model is important because it is determined by the situation, but conventional models of this type are generally made of metal, wood, resin, plaster, etc., and each has a large number of small holes that lead to the decompression chamber inside the suction box. The structure was such that a vent plug was buried in the vent plug, which caused the following problems: The suction point was limited, and the diameter of the small hole could not be reduced beyond a certain level. The shape was passed through two plastic films and transferred to a vacuum mold. water.

Since the pitch of the openings and small holes cannot be made fine, the suction force becomes uneven at the uneven corners of the model, and the film σ
) Peeling and wrinkles are likely to occur due to a decrease in demand.

C. Because the vent plug is embedded in the small hole, problems such as dust and rust getting into the slit and the vent plug oozing out above the model board are likely to occur.

2. Overheating of the film causes the film to bleed into the model during mold cutting, making it difficult to release from the mold.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems of the conventional mold-making model as described above, and to provide a model of this type that does not require drilling small holes and can be manufactured easily and inexpensively.

Another object of the present invention is to provide a trapping model that has excellent strength and durability in addition to the above features.

In order to achieve the above object, the present invention involves mixing iron-based (3) powder, ceramic, and a caking agent that evaporates during the hardening process in a predetermined aN mixture, and then pouring and molding the slurry-like material into a prototype model. The entire mold is made porous due to the evaporation and evaporation of the binder component during drying after release from the mold. In addition to the above, the present invention also provides a hardened shell layer that is dense and porous on the surface by firing in an oxidizing atmosphere after drying. It is a T-shaped thing.

The embodiments of the present invention will be explained below with reference to the attached drawings.
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Figures 1 to 3 show an embodiment of a mold making model according to the present invention. 1 is a slurry-like mixed material, and iron powder 11 and ceramic powder 12 are used as aggregate. Toshiko 7
It has the physical properties of evaporating at a low temperature and hardening over time, and has a composition of 1 kneading agent and 1 kneading agent.

As the iron-based powder in the mixture 1 and part 1, cast iron powder, pure iron powder, iron powder such as black powder, or steel powder can be used. Any ceramic powder can be used, such as a neutral powder such as high alumina such as mullite, an acidic powder such as silica, or a basic powder such as magnesia. Be able to do that.

As the caking agent, silica sol, typified by ethyl silicate, or colloidal silica can be used. 1102 in case of silica and luque
It can be said that it is desirable that the ceramic powder is neutral or acidic.

It is desirable to use the iron-based powder and ceramic powder having a particle size of about 150/1 m or less. 70 The reason is that if the particle size is large, the surface roughness increases and the transferability decreases.There is no particular limit to the particle size, but if the particle size is too small, it will be cranked during manufacturing and will result in -IP-f. is 50
zJ m or more is preferable. If it is within the above range, transferability is good, cracks are less likely to occur, and good porosity as described later can be ensured.

The mixing ratio of the iron-based powder and ceramic powder is approximately (1) by weight.
-5): (1 to 5) are suitable, and this is the case where the L dead wood is added at a weight ratio of lσ. Increasing the proportion of iron-based powder increases air permeability, but excessive addition has the disadvantage of lowering strength and increasing surface roughness. =1: If the blending ratio of constant ceramic powder is too low, dimensional expansion will increase, and if the blending ratio is too high, the strength will decrease f.
In the case of the present invention, the caking agent functions to bind the iron-based powder and the ceramic powder, as well as to provide air permeability to the entire model by removing evaporable components such as alcohol. If the amount of this caking agent added is too small, the moldability of the @-type will be deteriorated due to lack of fluidity, and if it is too large, the strength will be reduced due to porosity. When the above mixing ratio σ) is used, it becomes possible to achieve a well-balanced combination of strength, surface texture, and air permeability required for the model.

Next, the mixed material 1 in the form of a slurry according to the present invention is cast and molded. Specifically, as shown in Fig.
While pouring the mixed material 1 in the form of slurry in a constant state,
It is also effective to accelerate hardening by applying vibration or squeezing to spread the mixed material 1 on a master model plate to a uniform thickness.Adding a hardening agent if necessary is also effective for accelerating hardening. After that, stop shaking @, leave it for a predetermined time to harden the mixed material,
Thereafter, the cured and molded model 2 is removed from the frame 6 and the cooling mold.

The molded model 2 is then dried. This drying is 1 to 48
This is carried out by natural drying for a period of time, or if necessary, instead of this natural drying, primary firing is carried out after natural drying. The primary firing may be performed by directly igniting two models and burning the evaporated components (alcohol, etc.) in the caking material that evaporates from the molding surface. [Drying] in the present invention includes this primary firing. At any time, the drying process causes the evaporated components contained in the binder to escape from the inside of the mold 2 to the surface.
(7) By J'L, as shown in FIGS. 2 and 3, a replacement mold 3 for mold making consisting of a porous structure in which infinitely small pores 20 of 2 to 10 μm are running is obtained.

In Fig. 4 (showing another embodiment of the civil engineering invention, θ), a slurry-like mixed material is poured into the previous j: 5 and molded, and this is heated with dry w, l-, tanora, air, etc. 71 pieces from composite fired bodies fired in an oxidizing atmosphere, outer circumference +! A hard and dense hardened shell layer 81 containing the oxidized content of the iron-based powder in the mixed material is formed on A, and a backing J132 made of an unfired mixture is formed inside the hardened shell layer 31.

MA The hardened shell layer 31 is made up of a bonding structure between iron oxide particles changed from iron-based powder and fired refractory particles. After removing the 1st burr, countless minute pores are formed by the binder component, and these minute pores create a porous, dense, and hard surface. Banking/#: (2 (8) The composite structure consists of a mixed structure of unfired iron powder particles and ceramic powder particles. The pores in the hardened shell layer 31 are similar to the pores in the hardened shell layer 31.

Although the formation mechanism of the hardened shell layer is not necessarily clear,
The iron-based powder changes to iron oxide, greatly increasing its volume 1-, and as the ceramic particles are sintered in a form that envelops them, the firing of the ceramic particles also progresses, resulting in diffusion bonding at the interface with the ceramic particles. It is believed that this took place.

Firing conditions depend on the blending ratio, particle size, and model dimensions, but in general, it is appropriate to hold the temperature at about 100℃ for 0.5 hours or more, then cool it.The upper limit of the firing temperature Assuming 1.00 (1℃), the strength improves by curing, but the surface quality deteriorates and the transferability is from 5 to 5. This is because the formation of the hardened shell layer becomes uncertain and insufficient.

The model 3 obtained by the above J) is installed on top of the suction box 7 as shown in Fig. In this case, in the present invention, since the model 3 itself is porous and has air permeability, it is necessary to embed a vent peg with small holes. There is no pressure, and just by inhaling air from the decompression chamber, a suction force is applied to the glass film over the entire area in front of the model.Then, the original model is faithfully transferred because it is formed by pouring 3U of Cies slurry-like materials in front of the model. In addition, all of the above 1. suction and ambiguous plastic film are used.
The stone transferability is extremely good, and the plastic film can be closely attached to every corner of irregular shapes and patterns.Next, specific examples of the present invention will be shown.

Example 1 1. Cast iron powder (particle size 2()0 μm or less) was used as the iron powder system, synthetic mullite powder (particle size 200 μm or less) was used as the ceramic powder.
μm under) was mixed and stirred, and ethyl silicate was added as a binder to the colander so that the weight ratio was 1:1:1. The model was attached to a plate material, t, y, - poured into a frame and cured, and after curing, the mold was released and air-dried for 24 hours to obtain a model for a vacuum mold.

Old? '1. Figure 6 shows the air permeability test results of the model in relation to the mixing ratio of iron-based powder and ceramic powder. It can be seen from FIG. 6 that the air permeability increases as the content ratio of iron-based powder increases.

111.Next, the dimensional accuracy of the model was examined in relation to the original model. Figures 7(h)(b) and 8(a)(b) show the measurement points of the model and the prototype model.The measured values are shown in Tables 1 and 2 (σ) below.

Table 1 Unit: Revised Table 2 θ) As is clear from Tables 1 and 2, the model according to the present invention is within the dimensional accuracy range of 0.1 to 0.3 mm, which is higher than that of the conventional model. The dimensional accuracy is on the same level as the model, and it can be used satisfactorily.

(1) Using the model according to the present invention and the conventional model, film molding was performed using a vacuum mold. The results are shown in Table 3, and the conditions during molding are shown in Fig. 9 and Fig. 1O. f Plastic film material vinyl acetate, thickness 0. It is lWn.

Table 3 As is clear from this Table 3, Figures 9 and 1 ( ), in the model 9f of the present invention, the degree of adhesion of the film was very good, and the adhesiveness of the film was very good, and The adhesion is perfect.

In contrast, in the conventional model 9, the pitch of the small holes 90 is set to 1, and the pitch of the small holes 90 is set to 0.5 to 0.5 at the corners.
A gap of 0.8 mm was created, resulting in poor adhesion. this is,
This is because the model of the present invention has good air permeability throughout, and the suction force works throughout the entire model.

Example 2 1. Cast iron powder (particle size under 100 μm) as iron-based powder,
Mullite powder (particle size 1()0 μm or less) as the ceramic powder and ethyl silicate as the binder were mixed and stirred in a weight ratio of 2:2:1. Pour it into the frame containing the prototype model and let it harden.
After releasing the mold, the surface Yc was ignited for primary firing, and then secondary firing was performed at 900 C in an air atmosphere to obtain a vacuum molding model with a hardened shell layer made of iron oxide on the outer periphery.

(2) The relationship between the firing time and compressive strength of the obtained model for vacuum molding is shown in FIG. 11. As is clear from FIG. 11, when firing is performed in step 5, the strength of the model is greatly improved by π, and some of the important corners of the model are chipped ′f[
This type of model can be made highly durable because it does not cause any damage.

The porosity of this fired type was in the range of 20 to 25, and the adhesiveness of the glass film showed almost the same effect as in Example 1.

The present invention is suitable as a molding model for vacuum molding, and
It is also possible to apply the static pressure molding method, in which molding sand is poured into the space formed by the flask and model, and then compressed air is supplied into the flask to solidify the molding sand on the top of the model. It is.

For cutting using the mold making model of the present invention as described above, iron powder, ceramic powder, and a caking agent that evaporates during the curing process are mixed in a weight mixing ratio of (1 to 5): (] to 5); To,? We poured a slurry-like material into the prototype model, cured it, removed the volatile components in the binder by drying it after releasing it from the mold, and created porosity, eliminating the troublesome process of making small holes and venting. Not only can work such as embedding plugs be completely eliminated, but since there are no small holes for suction, no small holes are transferred to the plastic film, and the suction force is applied to every corner of the model, making it easy to use even in uneven corners. Also, it is possible to make a mold with a sharp outline by ensuring the film is tightly adhered to the film. Furthermore, since there is no need to embed the vent plug, there are no problems such as the vent plug floating up if the slit or small hole becomes clogged.
Film σ] It has the effect of not causing staining on the model, and the process is simple and can be manufactured at low cost.
I wish I could get a great effect.

Furthermore, according to the second aspect of the present invention, in addition to the features described in -A,
This has the advantage of being able to create a model with high strength and excellent durability.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing step-by-step a mold making model according to the present invention, FIG. 3 is a partially enlarged view of FIG. 2, and FIG. 4 shows another embodiment of the present invention. 5 is a sectional view showing the usage state of the model according to the present invention; FIG. 6 is a sectional view of the model according to the present invention θ; a graph showing the relationship between air permeability and composition change;
7(a) and 8(b) are plan views of the model according to the present invention, FIG. 7(b) and 8(b) are FIG. 7(a),
FIG. 8(a) is a cross-sectional view of the model; FIG. 9 is a cross-sectional view showing the state of film adhesion when suctioned using the model of the present invention;
FIG. io is a sectional view showing the state of film adhesion of a conventional model, and FIG. 11 is a graph showing the relationship between firing time and compressive strength in the example of FIG. 4. 1...Slurry-like mixed material 3...Model patent applicant Takeo Nakagawa, Shinto Kogyo Co., Ltd. January 30, 1982 Patent Application No. 71258 2, Name of the invention: Model for mold making 3, Relationship with the case of the person making the amendment Patent applicant Shinto Kogyo Co., Ltd. and 1 other person Sponsorship Claims, Invention Detailed explanation of 7. Contents of the amendment As shown in the attached sheet, the description of the claims of the present application is amended as follows. Weight mixing ratio of evaporable caking agent (1 to 5):
(1 to 5): A mold-making model obtained by pouring a slurry-like material mixed in 1 into a master model, curing it, releasing it from the mold, and drying it to impart porosity. 2. Iron-based powder and ceramic powder are used as aggregates, and a caking agent that evaporates during the hardening process is mixed in a weight ratio of (1 to 5): (
1 to 5): A slurry-like material mixed in 1 is poured into a prototype model and hardened, and after being released from the mold, it is dried and further fired in an oxidizing atmosphere to form a composite material with PM. 2. In the specification of the present application, page 4, line 8, page 8, line 9,
On the 10th line of the same page, the 12th line of the same page, the 2nd line of the 9th page, the 4th line of the same page, the 17th line of the same page, the 16th line of the 14th page.
"Hardened shell layer" should be corrected to "Hardened layer J. =2-250-

Claims (1)

[Scope of Claims] 1. Iron-based powder and ceramic powder are mixed with aggregate, and a caking agent that evaporates during the curing process is mixed in a weight ratio of (1 to 5): (1).
~5) A model for mold making made by pouring a slurry-like material mixed with 1 into a master model, hardening it, releasing it from the mold, and drying it to impart porosity. 2. Iron-based powder and ceramic powder are used as aggregates, and a caking agent that evaporates during the curing process is added at a mixing ratio of (1 to 5): (1 to 5).
5) Pour the slurry-like material mixed in = 1 into a prototype model, harden it, dry it after releasing it from the mold, and then fire it in an oxidizing atmosphere to create a composite fired body with a porous and dense hardened shell layer on the surface. A model for mold making.