JPS63290205A - Production of metallic mold made of metal powder compact - Google Patents

Abstract

PURPOSE:To easily produce a metallic mold by simple compacting frame by utilizing a method squeezing liquid in slurry of powder in the compacting frame, squeezing the liquid from linear slit in the compacting frame having the specific width under specific pressurized force and sintering the obtd. green compact. CONSTITUTION:The slurry 7 formed by adding and mixing metal powder for sintering, organic binder and water or organic solvent is prepared. Further, at the time of using (d) for average particle size of the above metal powder, the compacting frame 1 having the linear slit 3 satisfying the inequality to the slit width S is prepared. Then, plastic or gypsum-made master model 5 having transfer face of similar shape as the product is inserted into the frame 1 and the slurry 7 is poured into the frame 1 and pressurized with a plunger 6 at 30-200 kgf/cm<2> pressure. By this method, the liquid in the slurry 7 is discharged from the slit 3 to obtain the green metal powder compact. This is sintered to produce a metallic mold element, and by this metallic mold element, the metallic mold having a cavity with shape similar to that of the product shape in the interior thereof is made.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for manufacturing a mold using a powder compact, and relates to a mold for plastic injection molding, vacuum molding, press molding, blow molding, etc. used for.

(Conventional technology) As a mold manufacturing method, there is a method (conventional example 1) that creates a complex inverted product shape by machining such as cutting and engraving, and a method in which a metal (e.g. aluminum A method (conventional example 2) in which the shape is created by pouring over the molten metal (such as molten metal) and inverting the shape is generally adopted.

Conventional example 1 has few restrictions as a mold material, so
A mold material that matches the desired strength can be selected, and therefore the characteristics of the mold can be satisfied.

However, it is very time-consuming and requires various machining processes, so it has the disadvantage of being extremely high in cost (approximately, the ratio of material costs to processing costs in the total cost is l
: 9th place).

Conventional example 2 can reduce production costs because it requires fewer machining steps, but it also involves solidifying molten metal to form a mold, as typified by the mold manufacturing method using aluminum casting. Due to restrictions on mold materials, mold physical properties (
There is a problem in that the characteristics of a complete mold (compared to the characteristics required for a mold that meets the intended use) deteriorate.

That is, Conventional Example 1 and Conventional Example 2 each have advantages and disadvantages.

Therefore, the inventor proposed the technology previously proposed (Japanese Patent Laid-Open No. 61-1
No. 0405 Public I! After discovering the use of this material in mold manufacturing, he conducted various experiments.

In this proposed technology, a slurry composed of sintering powder, a binder, and water or an organic solvent is injected into a mold having a porous body on at least a portion of the inner surface of the mold and pressurized. This is a method in which the material is squeezed out through a porous body and molded into the desired shape. That is, this method is a method for removing the liquid in the slurry from a porous surface that constitutes a part of the inner surface of the molding frame, and is hereinafter referred to as a surface dewatering method.

The surface deliquification method has the advantage that the slurry containing the sintering powder is highly fluid, so it can be molded into the desired shape at low pressure, and even complex shapes can be molded easily. .

(Problems to be Solved by the Invention) However, the molding frame used for carrying out the surface deliquification method must have a part or all of its inner surface made of a porous material, and the molding surface lacks strength. There are also problems in that the method is expensive in terms of cost. Further, there is a problem that the roughness of the porous surface is transferred to the surface of the molded product, resulting in poor surface smoothness of the molded product and difficulty in releasing the mold.

Further, the mold material is desirably Fe-based metal in consideration of its mold characteristics. In general, Fe-based powders have a particle size of several microns or more and are not necessarily spherical powders, so they may get stuck in the holes of the porous surface during molding, making it difficult to release the mold and causing damage during removal. Therefore, it is difficult to mold this metal powder with a molding frame having a porous surface.

The present invention is not limited by the type of mold, does not require expensive special molding frames, is easy to transfer from a simulated product, and is much cheaper than molds made by machining. The purpose of the present invention is to provide a mold manufacturing method that satisfies the mold characteristics.

(Means for solving the problems) In order to achieve the above object, the present invention takes the following technical means.

That is, in the present invention, a master model made of plastic or plaster having a transfer surface having a shape similar to the product is prepared such that the slit width S is 10 when the average particle diameter of the metal powder for sintering is d.
A slurry made by adding and mixing an organic binder and water or an organic solvent to the metal powder for sintering was poured into the molding frame for 30 minutes. The slurry was pressurized at a pressure of ~200 kg, f/ctA, and the liquid content in the slurry was discharged through the slit to create a metal powder compact in which the powders contacted each other and were solidified via an organic binder. Create mold elements by sintering metal powder compacts,
This is a method of manufacturing a mold made of a metal powder compact, characterized in that the mold element is used to form a mold having a cavity in the shape similar to the product shape.

(Function) A plastic or plaster master model having a transfer surface with a shape similar to the product is placed in a molding frame, and the liquid content of the slurry injected into the molding frame is 30 to 20%.
By applying pressure of 0 kg, f/csA, it is squeezed out through a linear slot 7) formed in the molding frame. At this time, it is only necessary to form slits for liquid removal in the molding frame, so metal materials commonly used as the mold material can be used, and the slurry pressing force is 30 to 200.
Since the pressure is relatively low such as kg, f/cffl,
The model never undergoes any physical deformation.

In addition, since the width of the slit is set to a predetermined value, the slit can be easily formed in the mold, and the width of the slit can be easily formed in the mold without flowing out.
It is easily dehydrated by applying a pressure of kg, f/cJ.

When the liquid content in the slurry is sufficiently removed, the powders in the slurry come into contact with each other and are solidified through the binder to obtain the desired powder compact.

The surface quality of this molded body is determined by the inner surface quality of the molding frame, but the plastic or plaster master model used in the present invention is smoothed in advance, and by using this, a powder molded body with good surface quality can be obtained. easily obtained.

When this powder compact is sintered, a mold element having a sufficient density as a mold is created, and a mold having a cavity having a similar shape to the product shape is obtained inside the mold element.

(Example) First, the slurry used in the present invention will be explained.

The slurry is formed by mixing metal powder for sintering, an organic binder, and an organic solvent such as water or alcohol.

As the metal powder for sintering, one type or a mixed powder of two or more types of various metal powders (Pe, high speed steel, stainless steel, aluminum, etc.) made by carbonyl method, gas atomization method, water atomization method, pulverization method, etc. can be used. Moreover, a ceramic powder, a mixed powder thereof, or a mixed powder of these and various reinforcing fibers can be used as the metal powder. Examples of reinforcing fibers include carbon fibers, boron fibers, ceramic (SiC, ANt (h, etc.) whiskers, etc.).

Further, the particle size of the metal powder can be from several micrometers in average particle size. The lower limit of the average particle diameter is determined by the width of the linear clearance of the forming frame, which will be described later. Generally, various types of metal powders with a particle size of 10 μm or more are commercially available and are easily available.

Here, the average particle diameter refers to the particle diameter d11 corresponding to 50% of the cumulative weight ratio in the particle size distribution determined by the relationship between the particle diameter and the cumulative weight ratio as shown in FIG.
The cumulative weight ratio (%) Ro corresponding to a certain particle diameter d0 is the total weight of the sample powder -. Then, the cumulative weight of particles less than d0 is . Then it's Xiong. It is given as /-0X100 (%). The above particle size distribution can be easily measured using a particle size distribution analyzer (for example, manufactured by Cirrus).

As the organic binder added to the powder, one that is soluble in water or an organic solvent, which is the slurry liquid component, is used. For example, acrylic resin-based, cellulose acetate-based, and thermosetting resin-based binders can be used.A specific example of the acrylic resin-based binder is the product name "Bind Ceram WA320".
J (manufactured by Sankyo Toatsu) can be exemplified.

The composition of the slurry varies depending on the particle size of the sintering metal powder used, but is approximately 1, 2 to 5 parts by weight of binder, 8 to 40 parts by weight of water or organic solvent, and 100 parts by weight of metal powder.
It is about parts by weight.

Next, the molding frame used in the present invention will be explained. The molding frame used is one in which a linear slit is formed with a width S of 10 μm≦S≦3d, where d is the average particle diameter of the metal powder for sintering. As the material of the frame, a normal mold material may be used, and no special material is required.

The reason why the slit width S is set to be 10 μm or more is because it is difficult to form a slit with a 10 μm wide groove using normal industrial mechanical processing means, and also causes high costs.

On the other hand, S is limited to 3d or less because if it exceeds 3d, the metal powder will flow out of the slit, making molding difficult or impossible.

Here, the reason why S can be opened up to 3d is considered as follows. As shown in FIG. 4, when the metal powder 2 in the slurry injected into the molding frame 1 has a particle size smaller than S, the metal powder 2 formed in the molding frame 1 by pressure; trying to flow out. However, at this time,
The particles 2 form a bridge from the entrance to the middle of the slit 3.

At this time, when S = αd, if the α value is set to a value of 1 or more, the powder easily forms a bridge up to α = 3 and the outflow of particles is prevented, but when α = 4 or more, the bridging occurs. is difficult to form, resulting in particles flowing out from the slit.

A specific example of the molding frame is shown in FIG.

In the molding frame 1 shown in FIG. 2, a plastic or plaster master model 5 having a transfer surface 5A having a shape similar to the product is provided on the inner bottom surface of an outer frame 4, and a pressurizing plunger 6 is installed in the upper opening of the outer frame 4. It is fitted.

Furthermore, the outer frame 4 is appropriately divided in the vertical direction, and the slip width S between the opposing divided surfaces is set to 10 pIII≦S≦3d.
Similarly, slits 3 are formed between the pressurizing plunger 6 and the mold surface of the outer frame 4, and these slits 3 are linear when viewed from the molding chamber. There is.

In addition, in FIG. 2, 7 is a slurry, which is injected and filled into the molding chamber in which the master model 5 is charged. Further, 8 is a heater, which is provided as necessary.

1. When the plastic or plaster master model 5 placed in the molding frame 1 is a solid plate-like material, such as Chemiwood manufactured by Kokusai Michal, the shape of the final product is determined as shown in FIG. It is possible to adopt a method of manufacturing the product by mechanical processing using an NC lathe or the like from a drawing in which the product shape is inverted and larger, taking into account shrinkage during mold molding and product shrinkage during final product molding.

Furthermore, the model 5 can also be created by a casting method when the material is liquid, such as Ciba Geigy's epoxy resin (L Y556 + HY9745) or plaster.

That is, as shown in Figure 1, a wooden mold is created from a drawing of the final product shape, taking into account shrinkage during molding, an inverted plaster mold or raw resin mold is made from this wooden mold, and this is inverted to make a plastic or resin mold. It will be an official master model made of plaster.

The present invention is not characterized by the creation of this master model; one characteristic of the present invention is that a low-strength plastic or plaster master model is used for such metal powder molding. An example is shown. In other words, the physical properties of Araldite LY556 and HY974J as a hardening agent show that the tensile strength is 600~
700 kg, f/cd.

Heat resistant temperature is 160°C. Furthermore, by mixing 300 to 500 parts by weight of ceramic powder such as alumina, the desired plastic model can be obtained.

As shown in FIG. 2, the model 5 has a transfer surface 5A, and the surface other than the transfer surface 5A is a surface that is in surface contact with the outer frame 4 and transmits the total slurry pressure. be done.

In addition, the model 5 is placed in the outer frame 4, and the slurry 7 injected into it is pressurized by a pressure plunger 6 (30 to 20
0 k(,f/cnl), so it is made of plastic or plaster material that can withstand the pressure.

The mold manufacturing process will be outlined with reference to FIG.

A plastic or plaster master model 5 prepared according to the description is placed in a molding frame 1.

On the other hand, the slurry 7 that has been mixed and kneaded in a separate process is poured into the molding frame 1 and pressurized by pressing the pressure plunger 6, and the liquid in the slurry flows through the slits 3 formed in the molding frame 1. be discharged.

The slurry is pressurized at 30 to 200 kg, f/cd, and the slurry is pressurized and deliquified until the powders in the slurry come into contact with each other. In this state, the powders are solidified through the binder-containing water or organic solvent present between the particles.

In addition, in the compact, the fact that the powders are in contact with each other means that
It is also a prerequisite for sintering powders together.

By the way, the powder compact 7A formed by pressurized deliquification
After being taken out from the molding frame 1, it is dried as appropriate. On the other hand, the model 5 is transported again to the molding frame 1 for preparation, if necessary. By drying the compact 7A, the solvent between the powder particles is vaporized, the binder in the solvent is concentrated or solidified, and the contact strength of the particles is improved. By this, the molded body (
(green body) improves handling properties.

The above drying may be carried out after the molding, but it can also be carried out at the same time when the slurry is pressurized using the heater 8 shown in FIG.

In this case, the temperature applied for drying is higher than the boiling point of water or organic solvent, preferably 10 to 3
It is preferable to set the temperature to 0°C. By applying such a temperature, the water or organic solvent in the molded article can be boiled and vaporized to disappear in a short time.

This has the advantage that the drying process after removal can be simplified.

Incidentally, powders such as lead and aluminum that are easily plastically deformable as sintering powders are entangled and solidified by applying relatively low pressure, and are then molded. Therefore, the moldability and handleability of the powder compact become good for powders that are difficult to plastically deform, such as iron powder.

In this case, the organic binder and water or organic solvent are
The powder acts like a lubricant to cause sliding and plastic deformation. Therefore, the surface friction force between the powders decreases, and C
By using the IP method, mold pressing method, etc., it is possible to mold the powder in a state where the powders are in close contact with each other even at a considerably lower pressure than when molding powder, and this makes it possible to solidify the molded product. Become.

The molded body 7A is carried into a sintering furnace or the like and sintered to form a mold element 7B with a large shrinkage weight of the final product when forming the final product, after which a part is machined as shown in FIG. It is assembled by adding an easy mounting plate 7C and the like to form a mold having a cavity 7D inside.

Note that the mold element 7B after sintering can be subjected to parting processing, or texture processing, etc., on the mold mating surface portion, etc., if necessary.

Next, specific examples will be listed and explained.

(1) Using various metal powders for sintering shown in Table 1, the slurries shown in Table 1 were prepared. The formulation of the slurry is based on 100 parts by weight of powder. As the binder, the previously described "Bind Ceram WA320 J" was used, and as the solvent, water or alcohol was used.

(2) The slurry obtained in (1) was poured into the mold shown in FIG. The inner diameter of the molding frame was φ1801fl, and the outer frame had a two-part structure. The slit width (clearance) of the molding frame is shown in Table 1. After injecting the slurry to a depth of about 50 fins, a pressure plunger was fitted and preheated in this state.

The preheating temperature was 90°C when the solvent was water and 66°C when the solvent was alcohol (boiling point 76°C).

(3) The preheated molding frame injected with the slurry was placed in a pressurizer, and pressurized while heating. The molding pressures are shown in Table 1. The heating temperature was 120°C when the solvent was water, and 90°C when the solvent was alcohol.

Approximately 20 minutes after the start of pressurization, the solvent in the slurry in the molding frame stopped boiling, and the pressure became stable. Stay in this state for another 10 minutes,
A predetermined pressure was applied and maintained while heating.

After 30 minutes from the start of pressurization, the molding frame was taken out from the pressurizing machine and cooled, and then the powder compact was taken out from the molding frame. If a molded body is obtained, dry it completely,
Relative density (% by volume) was measured.

(4) The feasibility of molding and the relative density of the green body are also listed in Table 1. In the same table, O indicates that molding is possible, △ indicates that molding is difficult, and × indicates that molding is impossible.

The remaining amount of water or pulcohol in the molded product before complete drying shown in (3) was about 7% of the total volume of the molded product.

(5) From Table 1, molding was difficult or impossible for the comparative example (4.5) in which the slit width (clearance) exceeded 3 times the average particle diameter, but other methods with slit widths (clearance) of 3 times or less In the examples, molded bodies could be obtained.

However, for 3rd grade, the average particle size is 3 times or less, so although molding is possible, the molding pressure is 400 kg,
f/cd, the master model was deformed and it was difficult to obtain a molded product having the final product shape or a shape close to it. Also, for this I'lh3, the master model could not be reused.

Furthermore, regarding case 16, although the condition that the average particle diameter is 3 times or less is satisfied, the molding pressure of the slurry is very low at 25 kg and f/C4, so it is impossible to mold it. there were.

(6) The obtained powder compacts were sintered in a sintering furnace under the sintering conditions shown in Table 1, and the relative densities of the sintered bodies at this time are also shown in Table 1.

In addition, among the times under the sintering conditions (lower rows in Table 1), 1/8, 1/24, etc. are 8Hr and 24H up to the sintering temperature.
This means that the temperature was increased over IHr and maintained at this temperature.

(7) A part of the sintered mold element was assembled with a mounting plate that was easily machined.

Next (Effects of the Invention) As explained above, according to the present invention, a slurry made by adding and mixing an organic binder and water or an organic solvent to a metal powder for sintering is injected into a forming frame. 200 ksr
, pressurizes at f/c+4, drains the liquid in the slurry through the slit, and creates a metal powder compact in which the powders come into contact with each other and are solidified via an organic binder.This is then sintered to form a mold. Therefore, the cost of the mold (cost including all raw materials, manufacturing, etc.) can be significantly reduced compared to the cost of conventional metal cutting molds.

In particular, when the slurry pressure is 30 to 200 kir,
Since it is f/crA, it is possible to use a plastic or plaster master model, which promises a significant cost reduction.

Furthermore, when making a multi-cavity mold, the present invention makes it possible to make a large number of individual units and combine them to form a multi-cavity mold, which eliminates the conventional method of cutting from a metal block. The cost was significantly reduced compared to

In addition, when it is necessary to make multiple molds to manufacture a product due to the lifespan of the metal, there is no need to make a master model again, which also reduces costs.Furthermore, compared to conventional example 2, Therefore, the mold material is not subject to any restrictions, and after sintering, it can be made to have the required density as a mold characteristic.

Moreover, it is sufficient to form linear slits in the molding frame into which the slurry containing the sintering metal powder is injected, and any ordinary metal mold material can be used as the molding frame. Therefore, the molding frame does not lack strength, and the molding surface can be processed to be smooth by ordinary mold processing means.

Therefore, by injecting slurry into a molding frame and pressurizing it, and draining the liquid in the slurry through the slits, it is possible to easily obtain a powder compact with good surface properties and in which the powders are in contact with each other. This also makes it easier to take out from the molding frame.

In addition, since the width of the slit is specified within a predetermined range, it is easy to form the slit, and while preventing the powder in the slurry from flowing out, the liquid in the slurry can be easily discharged at a relatively low pressure. be able to.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a flowchart of the present invention, Fig. 2 is a cross-sectional view of a molding frame for carrying out the invention, Fig. 3 is a graph showing the particle size distribution of powder, Fig. 4 (1) and (2
) is a cross-sectional explanatory view showing the state of bridge formation of powder in the vicinity of the slit. ■...Forming frame, 3...Slit, 5...Model,
6...Plunger, 7A...Powder compact, 7B...
・Mold element. Figure 1 Figure 3 Figure 4 Figure 11 40f2 mrtJ-

Claims (1)

[Claims] (1) A plastic or plaster master model having a transfer surface with a similar shape to the product has a slit width S of 10 μm≦S≦3, where d is the average particle size of the metal powder for sintering.
d into a molding frame having a linear slit,
A slurry made by adding and mixing an organic binder and water or an organic solvent to the metal powder for sintering was poured into the molding frame for 30 minutes.
~200kg. Pressure is applied at a pressure of f/cm^2, and the liquid in the slurry is discharged through the slit to create a metal powder compact in which the powders come into contact with each other and are solidified via an organic binder. Next, the metal powder is Create mold elements by sintering the compact,
A method for manufacturing a mold made of a metal powder compact, characterized in that the mold element is used to form a mold having a cavity having a similar shape to the product shape.