JPS60224507A - Air-permeable molding die - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a breathable mold.

The inventors of this application filed a patent application in 1982-1986 in an earlier patent application.
No. 784, Japanese Patent Application No. 1983-71258, Japanese Patent Application No. 58-7
As disclosed in No. 1259 and Japanese Patent Application No. 58-80943, etc., metal powder and ceramic powder are used as aggregates, and a binder containing components that evaporate or burn out during the hardening and firing process is further added as necessary. We have proposed a mold with an air-permeable structure, which is made of a composite fired body obtained by adding steel fibers and has a dense hardened layer containing at least iron oxide on its surface. However, when this mold is used for molding processes that require ventilation, such as vacuum molding molds, blow molding molds, etc., when the mold temperature rises, the cooling rate of the product slows down. There are problems in that it takes a long time to release the mold, and that the product is deformed if the mold is released too quickly, or that the product is not sufficiently molded if the mold temperature is too low.

The present invention has been made in view of these problems, and its purpose is to provide an air-permeable mold that does not have any problems in terms of strength and has excellent air permeability, thermal conductivity, and temperature control ability. It is about providing.

The present invention will be explained in detail below based on examples. 1st
As shown in the figure, (1) is a porous composite fired body with four parts (1a) in the center, and this composite fired body (1) is made of metal powder and ceramic powder, and the outer periphery including the mold surface. It has a dense hardened layer (2), and a backing layer (3) made of an unfired mixed structure inside this hardened layer (2). The hardened layer (2) consists of a bonding structure of metal oxide particles dispersed in ceramic powder and fired ceramic particles. Although the formation mechanism of this hardened layer (2) is not necessarily clear, it is generally considered to be the result of oxidation of metal powder and diffusion bonding at the interface with ceramic particles. Then, in this hardened layer (2), fine pores (5 to 10 μm thick) are formed as the binder evaporates or burns away during the drying process and the firing process in an oxidizing atmosphere. This creates a porous yet dense and smooth surface.

On the other hand, the backing layer (3) located inside the hardened layer (2) consists of a mixed structure of metal powder and ceramic powder that have not been sufficiently fired, and there is a Pores are formed due to evaporation or burning out of the binder.

The pores of this backing layer (3) communicate with the pores of the hardened layer (2), so the composite fired body (1) has a porous ventilation structure as a whole.

Such a porous composite fired body (1) is produced by mixing and kneading aggregate and a binder to obtain a slurry sample, pouring and molding the slurry sample, and drying or drying the molded body.
It is obtained by the next firing step and step 7 of firing the product after this step under oxidizing atmosphere conditions.

First, the process of obtaining a slurry sample is to thoroughly mix and stir metal powder and ceramic powder or steel fibers, and add a binder containing components that evaporate during the curing process, such as silica sol such as ethyl silicate or colloidal silica. etc., and thoroughly mixed and stirred. Next, the slurry sample is solidified and molded into a desired shape to obtain a molded body. This is done, for example, by setting a model or actual object inside a mold, pouring the slurry sample into the mold, and leaving it for the required time.
During this pouring, it is also effective to add a hardening agent, apply vibration to promote filling properties, or squeeze.

More specifically, as the "metal powder", iron powder such as cast iron powder, electrolytic powder, pure iron powder, and non-ferrous metal powder such as nickel powder and copper powder are used. Among these, cast iron powder has the advantage of promoting pore formation by burning free carbon during firing.

As a "ceramic powder", the deformation rate at high temperatures is small,
Materials that easily bond with metal powder, such as neutral materials such as mullite, calcined alumina, activated alumina, fused alumina, chromite, and sillimanite, fused silica,
Acidic materials such as zirconium and fused zircon are generally suitable, but basic materials such as magnesia and talc can also be used.

Furthermore, as the "steel fiber", stainless steel fibers are generally suitable. This is because stainless steel fibers do not disappear during the firing process, so they have a high reinforcing effect on both the hardened layer and the backing layer.

Other steel fibers such as free-cutting steel may also be used.
Further, the reinforcing effect of the backing layer can be obtained by using glass fiber, carbon fiber, ceramic, tungsten fiber, etc., and the advantages of preventing cracking and preventing ceramic powder from falling off can be obtained. Suitable steel fibers are ones that have high strength and a large surface area, such as those produced by a chatter vibration cutting method.

The mixing ratio of the metal powder, ceramic powder, and binder is approximately (1 to 5):(1 to 5) by weight, preferably 1.

Here, the lower limit of the mixing ratio of metal powder and ceramic, and of wood powder and binder is specified because it is necessary to obtain the minimum usable mold strength.

The reason for specifying the first limit is that too much aggregate will reduce the ability to cover the binder from the viewpoint of moldability, resulting in a decrease in strength and deterioration in the stability of the mold surface.

Next, the molded body obtained in the previous step is removed from the mold, and then air-dried and/or primary firing is performed, and the molded body is further fired for a second time under oxidizing atmosphere conditions.

The oxidizing atmosphere may be air or may be so-called oxygen-enriched air in consideration of oxygen supply. Firing conditions vary depending on the blending ratio of aggregates and binders, mold dimensions, target porosity, and production aspects, but generally the firing temperature is 400-15
A firing time of 1 hour or more at 00°C is appropriate, but it is not limited to these temperatures and times (The longer the firing time, the more the hardened layer will grow. Therefore, if you want to thicken the hardened layer, If you want to make the product thinner, you can shorten the firing time.This secondary firing process in an oxidizing atmosphere allows the ceramic powder to be fired and the metal powder dispersed in the molded body to be heated. As the oxidation sintering progresses, a dense hardened layer (2) is gradually generated from the surface to the inside, and at the same time, the volatile components of the binder remaining in the compact are burned off and the compact becomes porous. is promoted, and upon completion of the secondary firing, a porous composite fired body (1) as shown in Fig. 1 is produced.
is obtained.

Next, the composite fired body (1) in Fig. 1 is cut at the A-A' position to expose the unfired backing layer (3) and to prevent the mold surface from being damaged even if shot particles hit the mold surface. After masking with a plate, the unfired backing layer (3) is thoroughly removed by projecting a shot material such as shot particles toward the backing layer (3) using a projection device, and a cavity is formed on the back side as shown in Figure 2. (4a) and a hardened layer (2) on the outer periphery of the hollow molding chamber (4) was obtained. At this time, the shot particles projected from the projection device (not shown) do not cause molding or cracks, leaving only the hardened layer (2) of uniform thickness and only the backing layer (3) clean. removed.

In addition to the above-mentioned projection device, means for removing the backing layer (3) include a sandblasting device, sander, grinder, drill, etc., and when removing the hardened layer (2), a sander,
All you have to do is rub it once with a grinder, cutter, etc. to remove the grain.

Next, a conduit (5) is placed in the cavity (4a) of the hollow molding chamber (4) along the back of the mold surface, and water, air, liquid nitrogen,
After forming a flow path (6) through which a temperature regulating medium such as liquefied carbon dioxide, hot water, or hot air passes, a furan-based resin containing a curing catalyst as a binder is added to the cavity (4a) and mixed with the particles. The material (7) was filled so as to bury the conduit (5) and cured to obtain a breathable mold (8) as shown in FIG.

In addition, as particulate matter (7), from the viewpoint of thermal conductivity, strength, and heat resistance, aluminum alloys, copper alloys, iron-based materials, etc. with a particle size of 10
A relatively small size of about 0μ to 3tm is effective.

In addition to these particulate substances (7), particulates of plastic resins such as vinyl chloride resin, A-B-3 resin, and styrene resin, and inorganic compounds such as silicon oxide, zirconium silicate, aluminum oxide, and glass may also be used. good.

In addition, a pipe made of paper or polystyrene foam is arranged in place of the iron-based pipe (5) in the hollow part (4a), and then aluminum alloy is added with a heat-resistant binder such as sodium sulfate, ethyl silicate, or colloidal silica. ,Copper alloy,
A particulate material such as iron is filled and hardened, and then the paper or expanded polystyrene conduit is burned out to form a flow path (6
), and instead of the paper or foamed polystyrene conduit, a shell core may be used to fill and harden the aluminum alloy, copper alloy, iron-based, etc. particulate material, and then The shell core may be destroyed and removed by baking to form the channel (6).

In addition, the particulate material (7) can be cured by filling the particulate material (7) in which a urethane resin is added and mixed as a binder in addition to the above, and then curing by passing an amine gas through the mixture; Alternatively, sodium silicate is used as a binder, and after filling, carbon dioxide gas is aerated and cured.Furthermore, a thermosetting phenol resin is used as a binder, and after filling, the material is heated and cured at a temperature of 150 to 180°C. It's okay. Next, specific examples of the present invention will be shown.

(Example) Cast iron powder (particle size under 44μ) as metal powder and synthetic mullite powder (particle size under 75μ) as ceramic powder were uniformly mixed in a weight ratio of 1:1, and a curing catalyst was further added as a binder. Ethyl silicate containing 25 wt% of the total weight of cast iron powder and synthetic mullite powder is added, and these are sufficiently mixed and stirred to obtain a slurry sample. Next, this slurry-like sample was poured into a mold with a model set while being vibrated, and left to stand for a predetermined period of time to solidify and form.After the solidified molded product was released from the mold, it was left in the air for 24 hours to air dry. do. Next, it was charged into a firing furnace and subjected to secondary firing at a firing temperature of 900° C. for 4 hours in an oxidizing atmosphere to obtain a composite fired body.

Next, the back side of this composite fired body is cut to expose the internal unfired backing layer, and after masking with a rubber plate or the like so that the mold surface will not be damaged even if the shot particles hit the mold surface, the unfired backing layer is removed. Thick grains with a particle size of 0.5 mm are projected from a projection device toward the backing layer at a speed of 70"/se.
The unfired backing layer was thoroughly removed by projecting at a projection density of 100'9/· to form a cavity, and a copper conduit (9) was placed behind the mold surface of this cavity. IFI is performed to form a flow path (10), and further, a furan-based resin containing a curing catalyst in advance as a binder is added and mixed into the cavity, and aluminum alloy particulate material (11) with a particle size of 1.511 is added. The conduit (9) is filled and hardened so that it is buried, and a breathable mold (
12) was obtained.

Next, as shown in FIG. 4, this breathable mold (12) has an opening on the negative side and a ventilation hole (12) communicating with the outside on the other side.
3a) is fitted into the frame (13) with the mold surface facing the opening side and the back side facing the ventilation hole (13a), and then inserting the vacuum pump ( (not shown) through the vent hole (138).
A resin product made of 0.5 mm vinyl chloride sheet heated to 120°C was sucked and molded in about 6 seconds.

In this way, 50 resin products were continuously molded while passing cooling water at a water temperature of 16°C and a flow rate of 5 n/m into the channel (10). The mold rising temperature in 12) was 40°C.

(Comparative example) A breathable mold (1
When 50 pieces were molded in the same manner as described above using 2) without passing cooling water, the mold temperature of the breathable mold (12) rose to 60°C.

Therefore, the cooling rate of the resin product was slower than in the previous example, and it took longer to release the product from the mold, resulting in a drop in productivity.

As is clear from the following explanation, the present invention provides temperature control in the flow path formed on the back of the mold when the mold temperature is cold at the beginning of work or when the mold temperature rises due to continuous use. Since the temperature of the mold can be controlled to a predetermined temperature by passing the medium through the mold, it has the effect of greatly improving productivity, and the effect of contributing to this type of industry is significant.

[Brief explanation of the drawing]

Figures 1 to 3 show the manufacturing process of a breathable mold according to the present invention. Figure 1 is a cross-sectional view of the composite fired body, and Figure 2 is a cross-sectional view of the composite fired body in Figure 1. FIG. 3 is a cross-sectional view of a hollow mold with the backing layer removed, and FIG. 3 is a cross-sectional view of a breathable mold of the present invention in which a flow path is provided in the back cavity of the hollow mold and filled with particulate matter. FIG. 4 is a sectional view showing a state in which the breathable mold of the present invention is fitted into the frame of a vacuum forming apparatus. (1): Composite fired body (2): Hardened layer (3): Unfired backing layer (6) (10): Channel (
7) (11) : Particulate matter (8) (12) : Breathable mold 1 Zuhom 2 Zutei 3

Claims (1)

[Scope of Claims] 1. A composite fired body made of metal powder and ceramic powder used as aggregate, mixed with a binder containing a component that evaporates or burns out, molded and fired as a sample; Only the dense hardened layer containing metal oxides on the outer periphery of the body is left, and the internal unfired backing layer is removed to provide a cavity and form a flow path through which a temperature regulating medium is passed. A breathable mold made of a mold filled with particulate matter. 2. Consists of a composite fired body made by molding and firing a sample of metal powder and ceramic powder aggregate mixed with a binder containing components that evaporate or burn out, and metal oxides on the outer periphery of this composite fired body. A part of the dense hardened layer containing the and/or part or all of the internal unfired backing layer is removed to create a cavity inside and a flow path for passing a temperature regulating medium in the cavity. A breathable mold that is filled with particulate matter.