JPS63295031A - Metallic mold - Google Patents

Abstract

PURPOSE:To reduce the number of days for manufacturing a metallic mold by fitting a block mold made up of a sintered body of metallic powder molded by slurry liquid obtained through mold surface slits into fitting recessed parts provided on a metallic mold body made up of metallic material other than a sintered body of metallic powder. CONSTITUTION:The metallic mold body 10 is composed of metallic mold material other than a sintered body of metallic powder to provide fitting recessed parts 10A larger than molded surface parts 11A. The block mold 11 made up of a sintered body of metallic powder obtained by sintering a molded body of metallic powder molded out of slurry liquid obtained through mold surface slits is fitted and fixed attachably detachably. The days for manufacturing the metallic mold can be reduced by this constitution.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a mold having a block mold formed by sintering a metal powder molded body, and is used for plastic injection molding, vacuum forming, press molding, etc. Used in molds for molding, blow molding, etc.

(Conventional technology) There are two types of molds: a mold that creates a complex inverted product shape by machining such as cutting and engraving from the mold material (conventional example 1), and a mold that has a similar shape to the product made in a simulated manner. Generally, a mold (conventional example 2) is used, which is made by covering the mold with metal (such as molten aluminum) and inverting the shape.

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, because it is very time-consuming and requires various machining processes, it has the disadvantage of being extremely high in cost (approximately, the ratio of material costs to processing costs in the total cost is 1).
: 9th place).

Conventional example 2 can reduce production costs because it requires fewer machining processes, but it is also difficult to make metal molds by solidifying molten metal to form a mold, as typified by the mold manufacturing method using aluminum smelting. Due to restrictions on the mold material, 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
0405 Publication) for the manufacture of molds, and 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 with 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 liquid in a slurry from a porous surface that constitutes a part of the inner surface of a mold, and is hereinafter referred to as a surface deliquing 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. be.

(Problems to be Solved by the Invention) However, the mold 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 strength of the molding surface is insufficient. 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, Pa-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. Due to disadvantages, it is difficult to form this metal powder in molds with porous surfaces.

In addition, when a molded body made of metal powder is created by the slurry deliquid method and used as a mold by firing it, it is difficult to make the entire mold into fired crystals compared to the conventional method in terms of the total cost of manufacturing the mold. Although it is less expensive than the cutting and engraving mold shown in 1, since the metal powder sintered material used for slurry removal is generally more expensive than the mold steel material, it is easy to machine the mold other than the molding surface. Using powder sintered material even for the part where the shape of the mold can be adjusted is disadvantageous in terms of cost, and when sintering a powder compact, dimensional shrinkage occurs, but it is not necessary to sinter the entire mold. If it is made of crystal, there is a problem that distortion becomes larger during the shrinkage process during sintering.

The present invention reduces the machining parts such as engraving of the mold to the necessary minimum, and limits the part of the mold that uses baked crystal to the part that is difficult to machine, thereby achieving lower cost and higher precision. The purpose is to provide molds.

(Means for Solving the Problems) The present invention achieves the stated purpose by taking the following technical measures in a mold having a molding surface portion that comes into contact with a molded product to shape the molded product. This is what I did.

That is, in the present invention, the mold body 10 is made of a mold material other than the metal powder sintered body, and the mold body 10 is formed with a fitting opening portion 10^ larger than the molding surface portion 11A. A block mold 11 having a molding surface portion 11A is removably fitted and fixed in the fitting recess 108, and the block mold 11 is used to sinter a metal powder compact molded by slurry wire dehydration. The present invention relates to a mold characterized in that it is composed of a metal powder sintered body.

(Example) In FIG. 1, 1 is a base, 2 is a mounting plate for a lower mold, 3 is a lower mold, and the king is collinear with a bolt 4. 5
is an upper mold, which is attached to a mounting plate 6 with bolts 7. The upper mold 5 has a material supply passage 8, and the material supplied through this passage 8 is made into a predetermined shaped object by the upper and lower molds 3.5, and in this embodiment, A hollow cylindrical body and a hollow prismatic body are illustrated.

In FIG. 1, the present invention is illustrated as being applied to the lower mold 3, but the present invention is of course applicable to the upper mold 5 as well.

FIG. 2, FIG. 3 (1) (As shown in FIG. 21 and FIG. 4, the lower mold 3 consists of a mold body 10 and a block mold 11 having a molding surface portion 11A. , is made of a normal mold material other than a metal powder sintered body, and the mold body 10 has a fitting recess 10 larger than the molding surface portion 11A.
A is formed by machining.

A block mold 11 having a molding surface portion 11A forms a fitting recess 1
The block type 11 is removably fitted and fixed to 0A.
is a metal powder compact (
It is composed of a metal powder sintered body formed by firing a green body).

In addition, in FIG. 2, 12 indicates a runner,
The pair of fitting recesses 10A are communicated with each other, and the molding surface portions 11A indicated by ring-shaped grooves etc. are connected to each other.
2A is a block type runner, and this runner 12
A may be created during green body molding, or may be created by machining or the like after sintering.

FIG. 5 shows another embodiment, in which four fitting recesses 10A are formed, a block mold 11 is fitted and fixed in each recess, and the blocks are connected by a cross-shaped runner 12. Common.

Next, the creation of the block type described above will be explained.

Since this block type is created by a slurry line deliquification method, the slurry will be explained first.

The slurry is formed by mixing a sintering metal powder, an organic binder, and an organic solvent such as water or alcohol (hereinafter, water or an organic solvent will be referred to as a solvent).

As the metal powder for sintering, one type or a mixed powder of two or more types of various metal powders (Fe, high speed steel, stainless steel, aluminum, etc.) made by carbonyl method, gas atomization method, water atomization method, pulverization method, etc. can be used. In addition, ceramic powder, a mixed powder of these powders, or a mixed powder of these and various reinforcing fibers can be used for this metal powder. Examples of reinforcing fibers include carbon fibers, poron fibers, ceramic (SIC + AO203, etc.) whiskers, etc. I can give an example.

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, metal powders with a length of 108 m or more are commercially available and easily available.

Here, the average particle diameter refers to the particle diameter dm 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. In addition, the cumulative weight ratio (%) Ro corresponding to a certain particle size do is
When the total weight of the sample powder is Wo, and the cumulative weight of the particles below d is 10, then wo / Wo X100 (%)
is given by 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 generally about 2 to 5 parts by weight of binder and 8 to 40 parts by weight of solvent per 100 parts by weight of metal powder.

Next, a forming frame formed by the slurry line dewatering method will be described. As this molding frame, the average particle diameter of the metal powder for sintering is d
In this case, a linear slit with a width S of 10 μm≦S≦3d is used. As this material, a normal mold material may be used, and no special material is required.

The reason why the slit width S is set to 10 μm or more is because it is difficult to form a slit smaller than 10 μm using normal industrial machining means, and it 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. 9, if the metal powder 21 in the slurry injected into the molding frame 20 has a particle size smaller than S, it tends to flow out from the slits 22 formed in the molding frame 20 due to pressure. do. However, at this time, the particles 21 form a bridge at the entrance to the middle of the slit 22.

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, bridging occurs. They are difficult to form and result in particles flowing out of the slit.

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

The molding frame 20 in FIG. 5 has a product (
That is, an inverted model 24 having a transfer surface 248 having a similar shape (block type) is provided, and a pressure plunger 25 is fitted into the upper opening of the outer frame 23.

Note that the model 24 in FIG. 5 is exemplified as one for making a block mold having a shape different from the block molds shown in FIGS. 1, 2, etc.

Further, the outer frame 23 is appropriately divided in the vertical direction, and a slit 22 with a slit width S of 10 μm≦S≦3d is formed between the opposing divided surfaces, and the pressurizing plunger 25 and the outer frame 23 Similarly, slits are formed between the mold surface and the mold surface, and these slits 22 are linear when viewed from the molding chamber.

In addition, in FIG. 5, 26 is a slurry, which is injected and filled into the molding chamber in which the inverted model 24 is placed. Further, 27 is a heater, which is provided as necessary.

The inverted model 24 to be placed in the molding frame 20 is manufactured according to a conventional method from the product drawing, but in this case, the molding frame 20
When the green body pressure-molded is finally manufactured using this mold, the final product (the ring body in Figure 1) will shrink, so the size will be larger to account for this shrinkage. must be formed (this contraction is α)
In addition, the green body is sintered to make a mold, and it also shrinks during sintering, so a large green body must be made during powder molding to account for this shrinkage rate (this shrinkage is β ).

That is, as shown in FIG. 7, the inverted model 24 has a transfer surface 24 formed to be larger than the imaginary line (surface) 24B corresponding to the product outline to a size that can clear the above two shrinkage rates.
A, and the surfaces other than the transfer surface 24A are surfaces that do not directly contact the slurry, and in particular, the surface facing the transfer surface 24A is a surface that is brought into surface contact with the molding frame and transmits the total slurry pressure. .

In addition, since the inverted model 24 is placed in the outer frame 23 and the slurry 26 injected into it is pressurized (30 to 1000 kg, f/cd) by the pressurizing plunger 25, the material must be made of material that can withstand this pressurizing force. has been created.

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

A main process inverted model 24 is manufactured from the product drawing, and this inverted model 24 is placed in the molding frame 20.

On the other hand, the slurry 26 mixed and kneaded in a separate process is poured into the molding frame 20 and pressurized by pushing the pressure plunger 25, and the liquid in the slurry is discharged from the slit 22 formed in the molding frame 20. be done.

The slurry is pressurized at 30 to 1000 kg, f/-, 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 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 26 formed by pressurized deliquification
After being taken out from the molding frame 20, it is dried as appropriate. On the other hand, the inverted model 24 is moved back to the forming frame 20 as necessary.
It will be transported for preparation. By drying the compact 26A, the solvent between the powder particles evaporates, and the binder in the solvent becomes v
4. The particles shrink or solidify, and the contact strength of the particles improves. This improves the ease of handling the molded body (green body).

Note that the above drying may be performed after the molding, but it can also be performed simultaneously when the slurry is pressurized using the heater 27 shown in FIG.

In this case, the temperature applied for drying is preferably higher than the boiling point of the solvent, preferably 10 to 30° C. higher than the boiling point. By applying such a temperature, the solvent in the molded article can be boiled and vaporized 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 solvent act as a lubricant to cause the powders to slide against each other and undergo plastic deformation. For this reason, the surface friction between the powders is reduced, and it is possible to mold the powders into a state in which they are in close contact with each other even at a considerably lower pressure than when molding powders using the CIP method, mold press method, etc. This makes it possible to solidify the molded product.

The molded body 26^ is carried into a sintering furnace or the like, and is sintered to form a professional mold 11 having a surface portion 11A to be molded, and a fitting recess of the mold body 10 as shown in FIG. 10
A is fitted and fixed.

In addition to the above-described model, the model 24 may be a master model made of plastic or plaster when the molding pressure is 30 to 200 kg and f/crA. Furthermore,
The block mold 11 may have a rectangular shape in addition to a circular shape.

(Effects of the Invention) According to the present invention, a block mold having a shape corresponding to a complex-shaped portion in contact with a molded object, that is, a molding surface for shaping a molded object, can sinter a powder compact. Since this block mold is fitted and fixed in the fitting recess of the mold body, the area of the molded body is made as small as possible compared to the case where the entire mold is made of a sintered body. This makes it possible to provide molds that are lower in cost and take less time to manufacture than conventional molds.

In addition, in the case of a mold for molding multiple pieces using the same die, an inexpensive mold can be provided by making and assembling a powder sintered mold (pro-tsuku mold) for only the portion corresponding to the product unit.

Furthermore, the block mold part that fits and secures into the fitting recess of the mold body can be replaced with a block mold of a different shape made in advance by the slurry dewatering method, and by standardizing the shape of the mold body, One mold base can be used as multiple sets of molds.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway elevation view showing the mold of the present invention, Fig. 2 is a view taken along the line A-A in Fig. 1, and Fig. 3 (1) (21 and 4
Figures (1) and (2) are a plan view and a sectional view showing two examples of the block type, and Figure 5 is a plan view of another example corresponding to Figure 2.
Figure 6 is a cross-sectional view of the forming frame, Figure 7 is a front view of the inverted model, Figure 8 is a graph showing the particle size distribution of powder, Figure 9 (1)
(21 is an explanatory cross-sectional view showing the state of powder bridge formation in the vicinity of the slit, and FIG. 10 is an explanatory view showing a flowchart for making a part of the mold of the present invention. 3... Mold, 10... Gold Mold body, 10^...fitting recess, 11...block mold, IIA...molding surface part. Fig. 7

Claims (1)

[Claims] (1) In a mold having a molding surface portion that comes into contact with a molded object to shape the molded object, the mold body 10 is made of a mold material other than a metal powder sintered body, and the mold body 10 includes: A fitting recess 10A larger than the molding surface portion 11A is formed, and a block mold 11 having the molding surface portion 11A is removably fitted into the fitting recess 10A. A mold comprising a metal powder sintered body formed by firing a metal powder molded body formed by slurry wire deliquidation.