JPH0399746A - Precision suction mold - Google Patents

Abstract

PURPOSE:To obtain a mold having good strength, permeability, surface accuracy and transferability by making solid formed body of slurry-state material specified with component composition and composed of a composite formed body with drying and/or primary burning executed to form this to the permeable structure having specific porosity. CONSTITUTION:The slurry-state material prepared by mixing iron powder, ceramic powder and binder containing component vaporized in hardening process at wt. blending ratio of (1-9): (1-9): (1-3), respectively, is used. In some case, further, by adding and mixing reinforcing fiber, the slurry-state material is provided. This material is poured, formed and solidified so as to become the desired mold shape and the mold is manufactured through the drying process of he primary burning process or further executing the primary buring process after drying. This composite formed body is made to the permeable structure having >=10% porosity with fine pores generated with exhaust of vaporized component. For example, the composite formed body 1 has the recessed or projecting mold surface 10 and is formed with the fine pattern 100 on the mold surface, and this is clearly transferred to the casting surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a collapsible precision suction mold.

[Conventional technology and its technical issues]

Molds are essential when processing liquid or slurry materials into three-dimensional shapes. The characteristics of the mold in this case are: ■ It has good surface accuracy, can faithfully transfer minute patterns, and can handle complex shapes and thin-walled shapes; ■ It has pinholes on the surface and inside of the molded product. It is desired that the material should not produce any mold or cavities, (1) be easy to mold and be obtained at low cost, and (2) be able to disintegrate after use.

However, in the past, there was nothing that met these conditions. In other words, there is a green mold as a mold for metal casting,
Conditions (■) can be satisfied because mountain sand, semi-synthetic sand, or synthetic sand is simply mixed with water, such as coal powder, bennite, grain flour, etc., and then filled into a casting frame and compacted and molded.
It was not possible to satisfy the conditions of ~■, and precision casting could not be performed.

There are die-casting molds as molds for precision casting.
Although satisfying the condition of ■ is 1-11 ability, ■
It is not possible to satisfy the conditions (1) to (2), and there is a particular problem that cavities are likely to occur due to lack of air permeability.

The present invention was created to solve the above-mentioned problems, and its purpose is to have good surface precision, be able to faithfully transfer fine patterns, and be able to transfer complex shapes and thin shapes. In addition, it has good air permeability, can reliably remove air and gas inside the cavity and in the material, is easy to manufacture at low cost, and has good disintegration properties. The purpose is to provide molds.

[Means to solve the problem]

In order to achieve the above object, the present invention combines iron-based powder, preferably ceramic powder with a smaller particle size, and a binder containing components that evaporate during the curing process in a weight mixing ratio (1 to 9).
: (1 to 9) : A slurry material is prepared by mixing 3 in steps (1 to 3), or a slurry material is prepared by further adding and mixing reinforcing fibers, and this is poured and molded into the desired mold shape. , a composite molded body obtained by drying and/or primary firing the solidified molded body, and the composite molded body has a porous structure with a porosity of 10 to 50% as a whole.

The mold according to the present invention is suitable for, for example, the following uses.

■Low-pressure molding (non-pressure suction molding) in which liquid or slurry materials (slip), such as molten metal, molten glass, and molten plastic, are injected without pressure and molded by applying suction from the outside. (2) A mold in which the liquid material or slurry material is pressurized or injected into a cavity and molded by applying suction from the outside (pressure suction mold) This includes deaeration and dehydration of ceramics.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a precision suction mold according to the present invention, which is composed of a composite molded body 1 made of iron-based powder and ceramic powder as aggregates, and has a concave or convex mold surface 10. A fine pattern 100 such as grains is formed on the mold surface 10.

In Fig. 2, the mold consists of a composite molded body 1a for the upper mold and a composite molded body 1b for the lower mold, and a cavity 11°11 is formed by the mold surfaces 10 and 10 of the mold. Material is injected from the central injection path 12, and a hole 13 for an ejecting pin is formed in one composite molded body 1b.

Also, if necessary, a medium conduit or heater 14 for cooling or keeping the mold warm may be embedded.

FIG. 3 shows another embodiment of the present invention, in which the mold is made of a composite molded body 1 made of iron-based powder, ceramic powder, and reinforcing fibers 2 as aggregates.

The composite molded article 1. As schematically shown in FIG. 4, la and lb are composed of a structure in which iron-based powder particles 3a and ceramic particles 3b having a smaller particle size are joined by the interparticle suction force of finer binder particles 3c. The ceramic particles 3b are dispersed to fill the gaps between the iron-based powder particles 4, thereby creating a dense surface texture. Moreover,
Fine pores of 3 to 20 μm are formed by the evaporation components in the binder evaporating from the molded body layer to the outside, and the entire structure has a porous ventilation structure with a porosity of 10 to 50%.
The compressive strength is about 10 to 100 kg/■2.

The mold according to the present invention as described above is produced by mixing iron-based powder, ceramic powder, and a binder containing components that evaporate during the curing process in a desired mixing ratio, or by further adding and mixing reinforcing fibers to create a slurry-like material. It is made by a step of pouring and molding this slurry-like material, a step of drying the solidified molded object, a step of primary firing instead of drying, or a step of further primary firing after drying.

Specifically, as the "iron-based powder", iron powder such as cast iron powder, electrolytic powder, pure iron powder, etc. is used, and depending on the case, copper powder, stainless steel powder, etc. can also be used.

"Ceramic powder" can be any material as long as it is easily bonded to iron-based powder, such as neutral powder such as Murai, calcined alumina, activated alumina, fused alumina, Chroma 1, sillimanite, or fused Acidic materials such as silica are generally used, but basic materials may also be used. "Reinforcing fibers" are used to prevent cracks and ceramic powder from falling off, and to improve strength and dimensional stability.

The reinforcing fibers may be steel fibers such as stainless steel and free-cutting steel, glass fibers, ceramic fibers such as alumina, carbon fibers, and the like.

The particle size of the iron-based powder is 500 μm in maximum dimension, preferably 40 to 100 μm, and the particle size of the ceramic powder is smaller than that of iron-based powder, 300 μm in maximum dimension, preferably 35 μm.
~40 μn1. The reason why the maximum dimension is defined as above is because the strength tends to be insufficient and the surface accuracy is deteriorated due to excessive porosity. The reinforcing fibers generally have a length of 0.05 to 30nw, depending on the size of the mold.
n, the thickness may be appropriately selected within the range of 10 to 400 μm.

Next, the reason why a binder containing a component that evaporates during the curing process is used is to bond the iron-based particles and ceramic particles and provide fine pores. That is, in the conventional green mold for casting, ventilation gaps were obtained by joining coarse-grained sand in a point-contact manner.

The present invention differs from this idea by using particles with a fine particle size for mold forming, and achieves the formation of ventilation gaps by allowing the evaporated components in the binder to escape to the outside, thereby creating a dense mold surface. This creates countless and minute ventilation gaps. Specifically, a silica sol (a stabilized colloidal solution of silica), particularly an alcoholic solvent-based silica sol based on ethyl silicate, is suitable as the binder containing the evaporable component.

The mixing ratio of the iron-based powder, ceramic powder, and binder is preferably (1 to 9): (1 to 9): (1 to 3) by weight, and within this range, strength, air permeability, and heat One may be selected as appropriate depending on required characteristics such as conductivity and surface properties. The lower limit was set to 1:, 1:1 because
This is because it is necessary to obtain the minimum strength that can be used as a mold. Regarding the blending ratio of iron-based powder and ceramic powder, together with the particle size, they affect the surface roughness and collapsibility of the mold surface.

In order to simultaneously improve surface roughness and collapsibility, it is recommended that the weight mixing ratio of iron-based powder and ceramic powder be 426 to 1:9. To adjust air permeability, it is sufficient to reduce the blending ratio of aggregate to binder, and if those blending ratios are fixed, the blending ratio of iron-based powder and ceramic powder can be adjusted by decreasing the amount of iron-based powder. Just do it like this.

In addition, when using reinforcing fibers, the amount added is 1 to 10v.
It should be o1%. If it is less than 1vo1%, no improvement in strength or dimensional stability can be expected. However, addition of more than 10 νO1% is not preferable because it tends to cause fiber balls and reduces moldability.

Next, the slurry material is poured into a desired mold shape. FIG. 5(,) shows this stage, in which the slurry material 5 is poured into the flask 7 in which the master model 6 is placed and solidified. During this casting process, a curing agent is added, vibration is applied, or squeezing is performed as appropriate. Moreover, if pins and pipes are inserted as necessary in this step, the structure shown in FIG. 2 can be easily obtained.

Next, after the solidified molded element 1' is released from the mold, drying and/or primary firing is performed. This is because, in the case of the present invention, not only is the generation of cracks and distortions suppressed, but also the evaporation components such as alcohol contained in the binder are evaporated to form fine pores.

Drying may be carried out naturally for 1 to 48 hours, for example, or by drying for 1 to 48 hours using a vacuum dryer 8 as shown in FIG.
Vacuum drying may be performed at a temperature of about 0.0°C. The primary firing is to ignite and burn the evaporated components by burning the surface of the dried molded element with a torch lamp or by heating it with electric heat for a short time. The primary firing does not form a hardened layer on the mold surface, and the temperature is at most 450°C.
Although the time depends on the size of the mold, it is about 10 to 40 minutes.

With the above steps, the composite molded product 1, la shown in FIGS. 1 to 3 is
, lb are obtained, then as shown in FIG. 5(C), a sealing means 9 consisting of a film, cover, or box is applied to the outer surface excluding the mold surface 10 and the parting line.
A suction section 90 is provided at an appropriate location. Now it can be used as a suction mold.

Figures 6 and 7 show examples of the use of the mold according to the invention. FIG. 6 shows an example of a casting method in which a liquid or slurry material W is injected by gravity and a suction force is applied to the cavity. The molds used are a fixed type IA and a movable type IB consisting of composite molded bodies 1a and 1b, which have stopper means 9 and 9 on their outer surfaces, and suction parts 90 and 90 are connected to a vacuum pump or the like through a hose. It is connected to a pressure reducing device 91. Mold surface 1
0.10 is coated with mold coating agent and mold release agent in advance, and injection means 1
5, liquid or slurry material W is injected into the cavity 11, and at the same time, the pressure reducing device 191 is operated to apply negative pressure to the fixed mold IA and the movable mold IB, reducing the pressure inside the cavity 11 and casting. be done.

FIG. 7 shows an example of a method of casting a liquid or slurry material W at low pressure by suction. In this case as well, a fixed mold IA and a movable mold 1B consisting of composite molded bodies 1a and 1b are used as molds, and the outer surfaces are provided with sealing means 9, 9, and suction parts 90 and 90 at required locations are connected to each other through hoses. Pressure reducing device 9 such as a vacuum pump
Connected to 1. The movable mold IB is connected to the mold opening/closing device 16, and the liquid or slurry material W is placed in a container and passed through the conduit 19 by gas pressure introduced from the air guide hole 180 provided in the two-part sealing lid 18. It is injected into the cavity 11 under pressure in two parts, and at the same time, it is injected into the decompression device 91.
When the mold is operated, a negative pressure is applied to the fixed mold IA and the movable mold IB, and the pressure inside the cavity 11 is reduced to perform casting.

The above is an example, and only one mold may be a composite molded article according to the present invention, and even if both molds are composite molded products, suction may be applied to only one mold.

2- During such casting, the mold of the present invention is a composite molded material in which a slurry-like material made of iron-based powder and ceramic powder as aggregate and a colloidal binder added thereto is poured, solidified, and then dried or further fired. The strength of the mold is higher than that of conventional green molds due to the dispersion of iron-based powder as a strength member and the binding action of the binder. In addition, it has good heat resistance, and therefore, even after repeated rapid heating and cooling, defects such as cracks, chipped corners, and crumbling are suppressed. In particular, when reinforcing fibers 2 are added, the strength against bending is increased and dimensional changes are reduced.

Furthermore, in the present invention, air permeability is not achieved through point contact between the iron-based powder and the ceramic powder, but rather through the pore-forming effect caused by the release of evaporated components contained in the binder. For this reason, during the casting process, it is possible to uniformly create negative pressure in the entire cavity, fill the material evenly to every corner of the mold surface, and at the same time efficiently remove the air in the cavity and the gas or moisture contained in the material. can.

In addition, since the aggregate contains ceramic powder, the thermal conductivity is lower than that of a mold, and when the material is cast at low speed and low pressure, so-called hot water circulation is good. Therefore, it is possible to produce a good quality cast product without pinholes or cavities even if the shape is complex or thin.

Moreover, because of the ventilation structure described above, the particle size of iron-based powder and ceramic powder can be reduced, which allows for a finer surface texture, and because molding is performed by pour molding, it is possible to reduce the particle size of iron-based powder and ceramic powder. Transferability is obtained, and the fine patterns of the master model (for example, leather grain patterns) can be faithfully reproduced. Generally, there is a contradictory relationship between transferability and air permeability of the mold, and it is necessary to make the aggregate particle size finer in order to improve the transferability. Even if a pattern can be formed, it is difficult to transfer it to a cast product. According to the present invention, transferability and air permeability can be achieved simultaneously.

Furthermore, in the present invention, the composite molded body 1 constituting the mold. la and lb are made by drying a cast-molded element or heating it at a low temperature for a short period of time. In other words, it is an unsintered body. Therefore, the surface of the mold can be made to have very good surface quality, and the surface accuracy of the cast product can be made into a mold. On the other hand, when the casting molded element is dried and then fired, the dispersed iron-based particles oxidize and precipitate on the surface of the mold, expand and bond, and grow. Since it begins to cover the body surface, the surface quality becomes very poor. According to the present invention, this problem does not occur and a good surface roughness can be achieved, so that precise transferability can be achieved.

Next, specific examples of the present invention will be shown.

Specific example 1 ■ T4 iron powder (particle size 40 μn 1 under) as iron-based powder
, synthetic mullite (particle size 34 μm 1 under) was used as the ceramic powder, and ethyl silicate (S) was used as the binder.
(alcohol-solvent silica sol with 20% alcohol content and 80% volatile content) was used in a weight mixing ratio of 2:2:
1 and mixed uniformly to obtain sample A in the form of slurry 5. In addition, glass fiber (length 1
00 μm, thickness IQ μm) was added and mixed in an amount of 4 wt % to obtain slurry sample B.

Each slurry sample was used as a master model on an acrylic disc with a smooth surface (surface roughness Rz: o, 1 μm).
) was poured into a flask loaded with vibration, and after solidification, the mold was released and vacuum dried at 100°C to obtain mold A□. In addition, after vacuum drying at 100℃, ignite with a torch lamp and
Perform primary firing to burn out the alcohol for a minute, and then mold A2
I got it.

(2) The characteristics of each mold are shown in Table 1 below.

For comparison in Table 1, the mixing ratio of the above iron-based powder and ceramic powder was set to 3.
Near, 1:9, each surface roughness is about 1 μm
, decreased by 2 μm, and the surface roughness improved.

16- In addition, regarding the mold A1, after drying, the mold was further heated at 500°C, 9
As a result of oxidation baking at 00'C for 6 hours, the surface roughness was 50
Approximately 10 μm at 0°C, approximately 17 μI at 9°0°C
n, and the surface quality was poor. This is due to oxidation precipitation and expansion of iron-based powder.

Using m, a6 type A1, the mold surface was coated and gravity casting of the zinc alloy was performed while suction of 700 mmHg was applied. The casting conditions were a casting temperature of 420°C and a casting time of 30°C.
The mold release time was 30 seconds.

As a result, despite the wall thickness of 1 to 2 mm, the metal flows well and casts can be performed without sinkage, and the smooth surface is clearly transferred to the casting surface, and there are no cavities on the surface or inside. there were.

■ Using mold A2, low-pressure suction casting of AC4D and AC23H1 high-strength brass was performed, and the movable mold and fixed mold
A suction force of mmHg was applied. As a result, the casting accuracy was further improved than in the case (2) above, and a mold suitable for injection molding was obtained.

〔Effect of the invention〕

According to item 1 of the present invention as described above, it has better strength than a green mold, and can simultaneously achieve air permeability, extremely good surface precision and transferability, and also collapse after casting. A mold with good properties can be obtained, and the process and operation are simple, and expensive equipment such as an electric furnace is not required, so the excellent effect of manufacturing at low cost can be obtained.

Further, according to the second aspect of the present invention, the strength is improved and the dimensional stability is improved to a good level f, so that an excellent effect can be obtained in that the mold can withstand high-pressure casting.

[Brief explanation of drawings]

Figures 1 to 3 are cross-sectional views showing embodiments of the precision suction mold according to the present invention, Figure 4 is an enlarged view schematically showing the structure of the mold of the present invention, and Figures 5 (a) (b) ( C) is an explanatory diagram showing the manufacturing process of the mold of the present invention, and FIGS. 6 and 7 are cross-sectional views showing examples of use of the mold of the present invention. 1, 1a, 1b-composite molded body, 1'...element body, 3a...iron-based powder particles, 3b...ceramic powder particles,
3C... Binder particles, 5... Slurry material, 1
0...Mold surface, 11...Cavity

Claims (2)

[Claims] (1) Iron-based powder, ceramic powder, and binder containing components that evaporate during the curing process in a weight mixing ratio of (1 to 9): (1 to 9).
9): A composite molded body is obtained by pouring and molding the slurry material mixed in (1 to 3) into a desired mold shape, and drying and/or primary firing of the solidified molded body, and the composite molded body is A precision suction mold characterized in that it has a vented structure with a porosity of 10% or more as a whole with fine pores created by the escape of the evaporated components. (2) Iron-based powder, ceramic powder, and a binder containing components that evaporate during the curing process in a weight mixing ratio of (1 to 9): (1)
~9): The slurry-like material mixed in (1-3) and further mixed with reinforcing fibers was poured and molded into the desired mold shape, and the solidified molded product was dried and/or primarily fired. A precision suction mold comprising a composite molded body, characterized in that the composite molded body has a vented structure with a porosity of 10% or more as a whole due to pores created by the removal of the evaporated components.