JP2513905B2 - Ceramic injection molding method and molding die used therefor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ceramics injection molding method for producing an injection-molded article having excellent performance in the case of injection-molding ceramics, and a molding die used therefor.

(Prior Art) Silicon ceramics such as silicon nitride, silicon carbide, and sialon are more stable at high temperatures than metals and are less susceptible to oxidative corrosion and creep deformation. In recent years, therefore, active use of them as engine parts has been actively researched. Has been done in. For example, the radial turbine rotor made of these ceramic materials is lighter in weight and can increase the operating temperature of the engine as compared with the metal rotor, and is excellent in thermal efficiency. Therefore, the turbocharger rotor for automobiles or the gas turbine rotor is used. Has attracted attention as such.

Such a turbine rotor has blades forming a complicated three-dimensional shape, and therefore has a simple sintered shape.
For example, it is extremely difficult to finish a material having a simple shape such as a rod-like shape or a square shape such as a dense silicon nitride or silicon carbide sintered body into a desired shape by grinding.

Ceramics molding methods include plastic molding methods that utilize the plasticity of molding materials such as extrusion molding, sludge casting molding methods that inject sludge in which ceramic raw material powder is suspended in water into molds, and prepared powders into molds. A dry pressure molding method in which molding is performed by putting and pressing is well known. The injection molding method, which is often used for these other plastics, has recently come to be used for irregularly shaped ceramics and complicatedly shaped ceramics.

In the injection molding of ceramics, the raw material fine powder itself of ceramics has no plasticity unlike plastics, and therefore, a molding material, a pellet, or a plasticizing material obtained by adding a thermoplastic resin to the raw material fine powder has been disclosed by the applicant. 64-24
Molding material obtained by adding water proposed in No. 707 (kneaded clay)
Is used for injection molding.

That is, a ceramic powder is mixed with a thermoplastic resin such as polyethylene or polystyrene, a plasticizer, a dispersant, an organic binder made of wax or the like, and the mixed raw material is heated to have plasticity and injected into a molding die. This is a molding method, and a ceramic sintered body can be obtained by degreasing the obtained molded body and firing it. It is a method of mixing ceramic powder mainly with water as a plasticizing medium and an organic binder with a plasticizer, cooling the mixed raw material to give it plasticity, and injecting it into a molding die for molding. A ceramic sintered body can be obtained by removing the binder from the molded body and firing it. According to these molding methods, it is possible to quickly and accurately obtain a molded product with a small finishing allowance in a single operation for a complicated part that requires a considerable number of steps in other methods.

However, molding materials containing these ceramics have poorer fluidity than molding materials containing only thermoplastics, and may contain air bubbles when pushed into the mold from the injection molding machine, or may not be homogeneous. was there.

On the other hand, in the conventional injection molding method, the molding is performed by keeping the temperature of the molding die constant from the inlet to the tip.

However, when the temperature of the molding die is kept constant, a temperature difference of the molding material occurs between the die inlet portion and the tip portion during injection molding, resulting in a non-uniform density distribution of the obtained molded body. As a result, cracks or deformations occurred in the sintered body formed by firing the molded body, and the dimensional accuracy, strength, etc. became non-uniform, and a uniform sintered body could not be obtained.

(Problems to be Solved by the Invention) In view of the above situation, the inventors of the present invention have diligently studied a method of homogeneously injecting a molding material into a mold in ceramics injection molding, and it is advantageous to use a mold having a specific shape. The present invention has been accomplished, and further, it has been found that the molding material can be controlled to a uniform temperature by providing a temperature gradient in the molding die, and the present invention has been accomplished.

An object of the present invention is to provide a homogenous ceramic molded body having no defects such as pores and weld lines.

Another object of the present invention is to provide a homogeneous ceramic molded body having high dimensional accuracy and uniform strength without cracks or deformation.

Still another object is to provide an injection molding method and a molding die used therefor for efficiently obtaining a ceramic molded body having a complicated shape and a homogeneous shape with a high yield.

(Means for Solving the Problems) The molding method of the present invention for achieving the above object is a ceramics injection molding method, which comprises injecting a ceramics molding material into a cavity of a molding die through a gate by an injection molding machine. When the molding die is used in which the gate has an area of at least 20% of the maximum cross-sectional area of the cavity as viewed from the gate side, and at the end of pressurization, the temperature distribution of the molded body in the molding die is within ± 0.5 ° C. The temperature gradient of the mold is controlled so that

The shape of the gate of the molding die used in the method of the present invention is substantially similar to the projected shape of the cavity viewed from the gate side, whereby the molding material passing through the gate flows along the shape of the cavity. It is more effective if controlled in this way.

When each of the cavities has at least one thick part and a thin part, the gate may be opened in each thick part so that the injected molding material is filled from the thick part to the thin part. preferable.

In the method of the present invention, the best effect is obtained by setting the temperature gradient of the molding die so as to satisfy the following inequality.

x ≦ y ≦ 5x However, in the above formula, x is the moving time (seconds) of the molding material from the gate to the temperature measurement site, and y is the temperature difference (° C.) of the mold with the gate temperature measurement site. .

The molding die suitably used in the method of the present invention is a ceramics molding injection molding die comprising a cavity having a shape corresponding to the shape of the molded body and a molding material introducing portion for guiding the molding material from the injection nozzle to the cavity, The area of the gate is at least 20% of the maximum cross-sectional area of the cavity as seen from the gate side, and the heating means, the temperature control means, and the molded body temperature measuring means are respectively provided in a plurality of sections extending from the vicinity of the gate to the inner depth of the cavity. It is characterized by comprising and.

When the cavity includes at least one thick portion, each of the at least one thick portion is provided with a gate that directly opens, and the area of the gate is the maximum crossing of the cavity when viewed from the gate side. The object of the present invention can be achieved by forming at least 20% of the area.

Furthermore, the shape of the gate may be substantially similar to the projected shape of the cavity viewed from the gate side,
More preferable.

In the present invention, the "maximum cross-sectional area of the cavity viewed from the gate side" means the area of the maximum cross-section of the cavity perpendicular to the moving direction of the molding material passing through the gate, and simply "maximum cross-sectional area of the cavity". Sometimes called "area."

Further, "the projected shape of the cavity viewed from the gate side" means the projected shape of the cavity on a plane perpendicular to the moving direction of the molding material passing through the gate, and is simply referred to as "the projected shape of the cavity". Sometimes.

Furthermore, in the present invention, the thick portion and the thin portion are the maximum spheres inscribed in each part of the molded body when the diameter of the largest sphere inscribed in the molded body shape is the maximum wall thickness of the molded body. The diameter is calculated, and the part where the diameter is 40% or more of the maximum thickness is called the thick part, and the part where the diameter is less than 40% is called the thin part. The molded body having a plurality of thick portions is referred to as a molded body having one or more thin portions between the thick portions.

(Operation) Hereinafter, the configuration of the present invention will be described in detail with respect to its operation and specific embodiments thereof.

Injection molding of ceramics is carried out by pellets or kneaded clay (hereinafter,
It is called a molding material. ) Is pressed into an injection molding die for molding. The injection mold generally comprises a cavity corresponding to the shape of the molded body, and a molding material introduction portion including a sprue, a runner and a gate for guiding the molding material from the injection nozzle to the cavity. The slope of the sprue and runner is preferably about 2 to 10 °.

In the ceramics injection molding method of the present invention, a molding die having a gate area of 20% or more of the maximum cross-sectional area of the cavity as viewed from the gate side is used as the injection molding die. The gate area is the maximum cross-sectional area of the cavity viewed from the gate side.
When it is 20% or more, the molding material that has passed through the gate flows along the shape of the molded body, the air discharge in the cavity is uniform, and a molded body without defects is obtained. On the other hand, if an injection mold of less than 20% is used, the molding material that has passed through the gate will not flow along the shape of the molded body, resulting in uneven air discharge in the cavity, resulting in defects such as pores and weld lines in the molded body. Occurs and the yield of the molded product deteriorates.

Generally, a gate means an inlet into which a molding material flows into a cavity (product part). However, in the case of a so-called direct gate as shown in FIG. 1, for example, the sprue portion or runner portion and the cavity (product portion) 2 are mixed,
In some cases, the gate part cannot be specified. In such a case,
It is preferable that the G portion, which is a portion near the nozzle portion 1 of the product portion 2, is regarded as a gate, and the gate cross-sectional area in such a case is the G portion cross-sectional area.

Further, in the case of the present invention, when the gate shape G of the injection molding die is formed so as to have a substantially similar shape to the projected shape P of the cavity viewed from the gate side, that is, a similar shape or an approximate similar shape, the molding material that has passed through the gate. Can be controlled so as to flow along the shape of the molded body, and defects that occur in the molded body can be more effectively prevented. This effect becomes particularly large as the gate cross-sectional area increases. In the above case, the gate is preferably provided at the center of the gate mounting surface of the cavity. 2A to 2d, when the minimum width in the non-overlapping portion of the gate cross-sectional shape G and the projected figure P of the cavity is A and the maximum width is B, the shape G and the projected figure P are When the shapes are substantially similar to each other as shown in FIGS. 2a and 2b, the value of B / A becomes smaller than that of the dissimilar shape shown in FIGS. 2c and 2d (1
Therefore, the filling speed of the molding material into the parts A and B becomes almost constant, the air discharge in the cavity becomes uniform, and a defect-free molded product can be obtained. On the other hand, when the B / A becomes large like the non-similar shape, the filling speed from the A part is faster and the filling speed from the B part is slower, so that the discharge of the air in the cavity becomes irregular and the air is trapped in the molded product. Become.

Table 1 shows the relationship between the similar figures (Figs. 2a and 2b) and the non-similar figures (Figs. 2c and 2d). The maximum cross-sectional area of gate area / cavity (molded body) is 50%.

Moreover, as shown in FIGS. 3a and 3b, even if the maximum cross-sectional area of gate area / cavity (molded body) is 90%,
In the case of the figure, it can be seen that the gate is inefficient beyond the cross section of the molded body, and the similar shape is excellent. Furthermore, the larger the cross-sectional area of the gate, the smaller the B / A value of the gate having the similar shape becomes smaller than the B / A value of the gate having the non-similar shape. From this, it can be seen that the use of a gate having a large cross-sectional area and a similar shape is more effective because the air in the cavity is evenly discharged.

Throughout this document, with respect to the cross-sectional shape of the gate, a substantially similar shape, that is, a similar shape or an approximate similar shape means, for example, a shape as shown in FIGS. 4a to 7c. In FIGS. 4a to 7c, P indicates a cavity projection figure viewed from the gate side, and G and G'represent gate shapes similar to and similar to them, respectively. For example
Although the shapes in Figures 4a to 4c, P, G, and G ', are all considered to be circular,
Regarding the quadrangle shown in FIGS. 5a to 5c, a shape such as G ′ is regarded as an approximate similar shape. A polygon, for example, a circle G in FIG. 6c in the case of an octagon as shown in FIG. 6a, is regarded as an approximate similarity because the B / A value is extremely small. When the cavity projection figure P viewed from the gate side is a polygon (triangle or more), if any angle (θ) is 120 ° or more, a circle such as G ′ may be an approximate similar shape. Further, in a complicated shape P such as the turbine rotor shown in FIG. 7a, a similar shape G as shown in FIG. 7b may be used.
This may cause difficulty in mold making, or the fluidity of the molding material in the sprue part or runner part may deteriorate.
As shown in FIG. 7c, a polygonal shape such as a hexagon G ′ that connects the blade tips 3 of the blade portion 4 having the shape P may be used, and in the case of a hexagon, the angle (θ) is 140 °, and thus may be circular. Good.

In a mold of a ceramics molded body composed of a plurality of parts having different wall thicknesses, the inlet or gate to the molded body mold is
It is preferable to dispose so as to directly open to the enlarged portion (thickness portion) of the cavity corresponding to the thickened portion of the molded body. For example, in the case of injection molding the molded body M ₁ as shown in FIG. 8a, in the case of conventional injection molding, the arrangement method of the sprue S and the gate G as shown in FIG. 8b is usually considered.
As shown in FIG. 8c, the molding die of the present invention has an injection gate G provided in the thick wall portion 5 of the cavity, and the sprue portion is gradually thickened along the shape of the molding body. Molded injected into.

By arranging the gate in such a manner that the cavity is directly opened in the thick portion, the resulting molded article has a fine ceramics injection molding technology (published by Nikkan Kogyo Shimbun), page 122, FIG. It is possible to prevent the occurrence of defects such as a weld line and the entrapment of pores due to jetting, which are seen in the conventional method as shown in FIGS. The reason for this is that the molding material does not cause jetting by thickly injecting the molding material along the shape of the molded body from the thick portion, and the material is hard to cool and the fluidity can be maintained for a long time. This is because the weld line generated by

In addition, a molding die of a ceramics molded body having a plurality of thickened portions and having different thicknesses, for example, a molded body M ₂ whose front view and side view are shown in FIGS. 9a and 9b, has a thickened portion 5 ′. And 5 "
, The sprue S and the gate G as shown in FIG. 9c or 9d, or the sprue S, the runners R and R ′ and the gate G and G as shown in FIG. 9e. Although it is conceivable to dispose G ′, the molding die of the present invention is provided with injection gates G and G ′ in the thick portions 5 ′ and 5 ″ as shown in FIG. The molding material is injected and molded into the thick portions 5 ', 5 "of the molding body. In this case, it is preferable to maximize the injection amount of the molding material into at least one of the thick portions.
This is because joining the molding material flowing into each thick portion at the thick portion can prevent defects such as pores and weld lines from joining at the thick portion. For example, in FIG. 9e, the diameter of the runner R to the gate G is made larger than the diameter of the runner R'to the gate G ', or the distance of the runner R connected to the sprue S is made shorter than the runner R'. , The injection amount into the thick portion 5'can be controlled to be larger than the injection amount into the thick portion 5 ". Of course, in this case, even if the runners of the same shape and length join the molding material in the thin portion. Without it there is no need to control.

Further, the introduction part of the molding die of the present invention, that is, the injection sprue
The gate or the injection sprue, the runner, and the gate may have a constant taper in a portion or a runner portion continuous from the injection gate to the sprue. Particularly, in the case of a sprue gate whose injection is composed of a sprue and a gate, those having the above-mentioned taper are preferable. The taper angle may be appropriately selected depending on the molding material used,
Generally, it is about 1-10 °. The reason for providing the taper is to allow the injected molding material to spread so as to smoothly flow from the injection molding machine nozzle through the gate to the cavity, that is, the molding die, and to smoothly release the molding material from the die.

Further, in the present invention, the temperature of the mold is controlled so that the temperature distribution of the molded product at the end of the pressurization of the injection molding is within ± 0.5 ° C. For that purpose, for example, a method of setting the temperature of the molding die so as to have a gradient from the gate portion G to the tip of the die, or a method of controlling the speed (injection speed) of filling the molding material into the mold, etc. is there. As a concrete example of the present invention, as shown in FIG. 10, the molding material arrival time x (sec) from the mold gate portion to the temperature measuring portion, and the temperature of the mold from the mold gate portion to the temperature measuring portion. When the difference is y (° C.), the temperature gradient of the mold is set so that x ≦ y ≦ 5x. The reason for the range from y = x to y = 5x is
Since the specific heat or thermal conductivity of the molding material differs depending on the type and addition amount of the organic binder in the molding material, or the type and addition amount of the ceramic powder, the shape and wall thickness of the molded body differ, so the molding conditions etc. differ. , Etc.
Since a molding material having a large specific heat and a small thermal conductivity is not easily affected by the mold temperature, the mold temperature difference y can be reduced even if the molding material arrival time x is long, for example, y = x. or,
Since a molding material having a small specific heat and a large thermal conductivity is easily affected by the mold temperature, the mold temperature difference y must be increased when the molding material arrival time x becomes long, for example, y =
It will be 5x. More specifically, for example, the composition of the ceramic material is 48 to 60 vol% of ceramic powder and 52 to 40 vol% of the organic binder, and the composition of the organic binder has a molecular weight of 10,000 to 50,000 of 3 to 15 wt% and a molecular weight of 200 to 200. 1000 is 85
〜97wt%, molding conditions are molding material temperature 60〜80
When the temperature is 0 ° C and the mold temperature is 40 to 52 ° C, the range of x≤y≤5x is preferable.

When the mold temperature gradient is set as described above, the temperature of the injection-molded body is ± 0.
It becomes almost uniform within 5 ° C., which is preferable for producing a homogeneous molded body and subsequent production of a homogeneous sintered body. When the temperature distribution of the molded body exceeds the set temperature ± 0.5 ° C, the density distribution of the obtained molded body becomes non-uniform, and as a result, the sintered body formed by firing the molded body is cracked or deformed. However, the dimensional accuracy and strength become non-uniform, making it difficult to obtain a uniform sintered body.

Moreover, the time when the temperature distribution of the molded body needs to be within ± 0.5 ° C. of the set temperature is when the pressurization is completed. In general,
Injection molding is high pressure for a predetermined time after filling the molding material,
Then, the molded body is kept at a low pressure for a predetermined time in order to impart the shape of the molded body or prevent defects such as sink marks generated inside the molded body. The end of pressurization means the end of the high-pressure pressurization process carried out for the predetermined time.

In the injection molding method using an organic binder in which a large amount of a binder, wax, lubricant, etc. are added to the raw material powder and kneaded, the injection molding material temperature is higher than the mold temperature. The material is cooled as it goes from the gate to the tip, and the temperature of the molded body also becomes lower as it goes from the gate to the tip. In order to compensate for this and to keep the temperature of the molded body constant, the preferable temperature condition of the die as described above is such that the temperature of the die is increased from the gate portion to the tip portion. As a method for heating the mold, for example, a general heater (rod, band, etc.) may be used, or a liquid (water, oil)
May be used.

In addition, in the injection molding method using the kneaded material obtained by adding a small amount of an organic binder and mainly water to the raw material powder,
Since the temperature of the clay (molding material) is lower than the mold temperature,
The molding material becomes higher from the gate portion to the tip portion. In order to compensate for this temperature difference and keep the temperature of the molded body constant,
The temperature of the mold is lowered from the gate to the tip.

Examples of the ceramic powder used in the present invention include conventionally known oxides such as alumina and zirconia, as well as so-called new ceramics such as nitrides such as silicon nitride, carbides such as silicon carbide, and composite materials thereof. Etc. As the molding material, both an injection molding material (pellet) using an organic binder as a plasticizer and an injection molding material (kneaded clay) mainly using water as a plasticizing medium and an organic binder as a plasticizer can be used.

(Examples) Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1 Injection molding using an organic binder will be described with reference to the flowchart shown in FIG.

Mix 100 parts by weight of ceramic raw material (Si ₃ N ₄ ) powder with 2 parts by weight of SrO, 3 parts by weight of MgO and 3 parts by weight of CeO ₂ as a sintering aid, and add water to this mixture with an attritor. Then, the mixture was wet-mixed and ground to have an average particle size of 0.5 μm. Next, this was spray-dried to obtain granules having an average particle size of 30 μm, and the granules were isostatically pressurized at a pressure of 2.5 ton / cm ² for granulation.

Next, after crushing the granulated product to an average particle size of 30 μm, 3 parts by weight of a binder (ethylene vinyl acetate copolymer), 15 parts by weight of a plasticizer (paraffin wax), relative to 100 parts by weight of the obtained powder, Add 2 parts by weight of lubricant (stearic acid), knead,
It is extruded by an extruder and pelletized, and then this is used under the conditions of material temperature 68 ℃, mold temperature 50 ℃, injection pressure 400kg / cm ² and injection speed 200cc / sec, using the injection mold of the shape shown in Table 2. M _3, M ₄ shown in FIG. 12-FIG. 14 were injection molded Te,
A molded body of M ₅ was obtained. The turbine rotor, which is the molded body M ₅ in FIG. 14, has a maximum diameter portion (φ70 m) of the hub portion 6 excluding the blade portion.
The maximum cross-sectional area was defined as m).

 The results are shown in Table 2 and FIGS. 15 to 17.

Example 2 Injection molding using kneaded clay will be described with reference to the flowchart shown in FIG.

The same processes as in Example 1 were carried out up to the raw material preparation, mixed pulverization and spray drying steps. Granules with an average particle size of 30 μm obtained from the spray-drying step were obtained, and then 100 parts by weight of the granules, Cedran FF-200 surfactant, 1 part by weight of Sanyo Chemical Industry Co., Ltd., a plasticizer (methyl cellulose) ) 7 parts by weight and 30 parts by weight of water were added and kneaded. Next, vacuum kneading is performed on this kneaded material at a vacuum degree of 70 mmHg to obtain a diameter of 52 mm,
After obtaining a kneaded material having a length of 500 mm, isostatic pressing with a pressure of 2.5 ton / cm ² was performed. Next, the material temperature is 12 ℃, mold temperature is 60 ℃, injection pressure is 300kg / cm ² , injection speed is 200cc.
Under the condition of / sec, injection molding was performed using an injection mold having a shape shown in Table 3 to obtain molded bodies of M ₆ , M ₇ , and M ₈ shown in FIGS. 12 to 14. The results are shown in Table 3 and FIGS. 19 to 21.

As is clear from the above results, when an injection mold having a gate area of 20% or more of the maximum cross-sectional area of the cavity as viewed from the gate side is used, a molded body having no defects such as pores and weld lines can be molded, The molding yield is greatly improved. Further, as the gate area ratio increases, the molding yield of the similar shape or the similar shape is improved.

Example 3 Injection molding of an organic molding material will be described with reference to the process chart shown in FIG.

The raw material was prepared by mixing 100 parts by weight of Si ₃ N ₄ powder for ceramics, 2 parts by weight of SrO powder as a sintering aid, 3 parts by weight of MgO powder and
3 parts by weight of CeO ₂ was mixed and ground to an average particle size of 0.5 μm.
Next, spray dry by spray drying to obtain an average particle size of 30μ.
m granular material was obtained. This granular material was pressurized at a pressure of 3 t / cm ^{2 by} a hydrostatic isotropic pressure method.

After pressing, crushing and crushing again to an average particle size of 30 μm (called “method”), calcining in air at 450 ° C. for 5 hours,
A method of crushing to obtain an average particle size of 30 μm (called method)
The following two methods were prepared. Powder obtained after disintegration 100
By weight, 3 parts by weight of the binder, 15 parts by weight of the plasticizer and 2 parts by weight of the lubricant were mixed and kneaded with a kneader to obtain an organic molding material. The obtained molding material was pelletized by an extruder. The pellets thus obtained are then injection-molded into a machine as shown in Fig. 8a and Fig. 8a.
Injection molding was performed in the molds M ₁ and M _{2 of} the molded body shown in FIGS. 9a and 9b, respectively. The filling method of the molded body M ₉ was carried out by using the molds shown in FIGS. 8b and 8c, and were designated as the filling method 1 and the filling method 2, respectively. The angle of the sprue part of the filling method 1 is 2 °, and the filling method 2
It was 5 °. The method for filling the molded body M ₁₀ is 9c.
It carried out using the metal mold | die shown in FIG. 9, FIG. 9b, and FIG. 9e, and set it as the filling method 3, the filling method 4, and the filling method 5, respectively. Filling method 3
The taper angle of the sprue part of No. 2 was 10 °, and the taper angle of the sprue part of the filling method 4 was 5 °. In the filling method 5, the runners R and R'have the same length and diameter, and the taper angles are both 5 degrees. The same as Filling Method 5 except that the diameter of the runner R is smaller than that of the runner R ', the taper angle of the runner R is 5 ° and the taper angle of the runner R'is 10 °, and the flow rate of the molding material is controlled. This was designated as filling method 6. A schematic diagram of each filling process is shown in FIG. 23, and molding results are shown in Table 4.

As can be seen from the schematic diagram of the filling process in FIG. 23, the molded body M ₉
In the filling method 1 in which the molding material is filled from the thin portion of the molded article, the jetting of the molding material occurs in the thick portion, which is not preferable. On the other hand, in the filling method 2 in which the molding material is filled from the thick portion of the molded body M ₉ along the shape of the molded body, jetting does not occur and the material is uniformly filled, which is preferable.
As shown in the table, the molding yield was also improved.

The thick portion 5 ', the moldings in M ₁₀ having a plurality of 5 "filling method 3 and 5 is filled from one of the thick portion of the molded body
As a result, the other thick portion is filled from the thin portion, which is not preferable because the same problem as in the above filling method 1 occurs. On the other hand, both thick parts 5 ', 5 "
The filling methods 5 and 6 in which the molding material is uniformly filled with the molding material are preferable, and the molding yield is improved as shown in Table 4. Further, as compared with the filling method 5, 6 was adjusted so that the joining of the molding material was performed at the thick portion, and thus the occurrence of defects was less and a favorable result was obtained.

Example 4 Injection molding of a water-based molding material will be described with reference to the process chart shown in FIG.

Preparation of raw materials, mixed pulverization, and spray drying were performed in the same manner as in Example 3. 100 parts by weight of a granular material having an average particle size of 30 μm obtained by spray drying, 30 parts by weight of water, 7 parts by weight of a binder and 1 part by weight of a surfactant were mixed and kneaded with a kneader to obtain an aqueous molding material. It was The obtained water-based molding material was formed into a columnar shape having a diameter of 52 mm and a length of 340 mm by a vacuum extruder, and the columnar molding material was isostatically pressurized by a rubber press at a pressure of 2.5 t / cm ² . The obtained water-based molding material was molded using an injection molding machine in the same manner as in Example 3 to obtain molded articles M ₁₁ and M _12.
Was injection molded.

A schematic diagram of each filling process is shown in FIG. 25, and molding results are shown in Table 5. From these, it can be seen that almost the same results as the organic molding material of Example 3 can be obtained.

Example 5 An injection molding method using an organic binder was carried out. Hereinafter, the injection molding method using the organic binder of FIG. 26 will be described with reference to the flowchart.

As a sintering aid, SrO: 2 parts by weight, MgO: 3 parts by weight, CeO ₂ : 3 with respect to 100 parts by weight of silicon nitride powder as a ceramic raw material.
Part by weight is added, and these are crushed and mixed to obtain an average particle size of 0.5μ.
m mixed powder, and then spray-dried to obtain granules with an average particle size of 30 μm, isostatically pressurizing with a pressure of 2.5 ton / cm ² to granulate, and then crush it to obtain average particles. Diameter 30μ
m particles were obtained. Next, to 100 parts by weight of this prepared powder, a binder: 3 parts by weight, a wax: 15 parts by weight, and a lubricant: 2 parts by weight were added and kneaded to form a pellet, which was then heated to a material temperature of 68 ° C. , Injection pressure 400kg / cm ² , injection speed 100 ~ 30
Injection molding was carried out in a molding die shown in FIG. 27 while controlling the temperature of each part of X, Y and Z by the die temperature shown in Table 6 at 0 cc / sec and a pressurizing time of 15 sec. The shape of the gate of this mold was almost similar to the shape of the cavity, and the gate area was 20% or more of the maximum cross-sectional area of the cavity seen from the gate side. As a result, a molded body having a length of 150 mm, a width of 65 mm and a thickness of 15 mm was obtained. Table 6 shows the temperature of the molded body at that time.

Here, the mold shown in FIG. 27 includes a thermocouple 1 for controlling the mold temperature.
0,10 ', 10 ", thermocouples for measuring molded body temperature 11,11', 11" and heaters for heating mold 12,12 ', 12 "are provided to control mold temperature and mold temperature. Measurement is carried out, where G is a mold gate (inlet), and 13, 13 ', 13 "are pressure sensors inside the mold. The sampling interval of temperature and pressure of these sensors was 10 μsec.

Next, the molded body is heated to 400 ° C. at a heating rate of 1 to 3 ° C./h, held at that temperature for 5 hours for degreasing treatment, and then isostatically applied at a pressure of 7 ton / cm ^2. After pressurizing, it was fired at 1700 ° C. for 1 hour in a nitrogen atmosphere at atmospheric pressure to obtain a rectangular sintered body. Table 6 shows the dimensional accuracy and strength of the obtained sintered body.

Comparative Examples 1 and 2 A molded body was produced under the same conditions as in Example 5, except that the control temperature of the molding die was set to the condition shown in Table 6.
A rectangular sintered body was obtained. Table 6 shows the dimensional accuracy and strength of the obtained sintered body.

Example 6 Using the same raw material as in Example 5, molding was carried out using the mold shown in FIG. The gate shape of this mold was almost similar to the cavity shape, and the gate area was 20% or more of the maximum cross-sectional area of the cavity seen from the gate side.

Injection molding was carried out in the same manner as in Example 5 except that the mold control temperature was changed as shown in Table 6, and the diameter was 30 mmφ and the length was 30 mmφ.
A 200 mm compact was obtained, and degreasing and firing were carried out in the same manner as in Example 5 to obtain a round rod-type sintered body. Table 6 shows the dimensional accuracy and strength of the obtained sintered body.

Comparative Example 3 A round rod-shaped sintered body was obtained under the same conditions as in Example 6, except that the control temperature of the molding die was set as shown in Table 6. Table 6 shows the dimensional accuracy and strength of the obtained sintered body.

Example 7 The same raw material as in Example 5 was used, and it had at least one or more thick-walled portions shown in FIGS. 29a and 29b, and its gate shape was substantially similar to the cavity shape. The area of the maximum cross-sectional area of the cavity seen from the gate side
Injection molding was carried out in the same manner as in Example except that the control temperature was changed as shown in Table 6 by using a mold of 20% or more to obtain a turbine rotor molded body with a tip diameter of 150 mmφ and a blade height of 100 mm. Further, degreasing and firing were performed in the same manner as in Example 2 to obtain a turbine rotor sintered body. Table 6 shows the dimensional accuracy of the obtained sintered body.

Comparative Example 4 A sintered body of a turbine rotor was obtained under the same conditions as in Example 7, except that the control temperature of the molding die was set as shown in Table 6. Table 6 shows the dimensional accuracy of the obtained sintered body.

As is clear from the above Examples 5 to 7 and Comparative Examples 1 to 4, the control temperature of the mold is increased from the inlet to the tip, and the temperature rise is caused by the temperature gradient as shown in FIG. When the temperature is within the range, the temperature of the compact at the end of pressurization is within ± 0.5 ° C of the set temperature at any part, and it can be seen that a sinter with high dimensional accuracy and high strength can be obtained.

Example 8 An injection molding method using kneaded clay was carried out. Hereinafter, description will be given according to the flow sheet of the water-based injection molding method of FIG.

To 100 parts by weight of silicon nitride powder as a ceramic raw material, SrO: 2 parts by weight and CeO ₂ : 3 parts by weight were added as a sintering aid, and these were pulverized and mixed to obtain a compounded powder having an average particle size of 0.6 μm, Then, by spray drying, granules having an average particle size of about 30 μm were obtained. To 100 parts by weight of the granules, an organic binder (methyl cellulose: 7 parts by weight, Cedran FF-20
0: 1 parts by weight) 8 parts by weight and about 30 parts by weight of water were further added and kneaded, and then vacuum kneading was performed at a vacuum degree of 70 mmHg to obtain a kneaded clay having a diameter of 52 mm and a length of 500 mm. This is hydrostatically isostatically pressed at a pressure of 2.5 ton / cm ² , then aged in a cool and dark place at a temperature of 12 ° C overnight, then at a kneaded material temperature of 12 ° C, an injection pressure of 150 to 300 kg / cm ² , and an injection speed of 100. ~ 300cc / sec, gel hardening time 1 ~ 3 minutes, molding metal shown in Fig. 27 having the same shape as that of Example 5 while controlling the temperature of each part of X, Y, Z by the mold temperature shown in Table 7. Injection molding was performed in the mold to obtain a molded body having a length of 150 mm, a width of 65 mm and a thickness of 15 mm. Table 7 shows the temperature of the molded body at that time.

Then, the molded body is heated at a constant temperature and humidity to a temperature of 60 to 100 ° C.
The temperature is raised to 98%, the humidity is reduced from 98% to 20% and dried, then the temperature is raised to 500 ° C at a heating rate of 50 ° C / h, and the temperature is increased to 5 ° C.
Perform binder removal and retention time, and then after the hydrostatic isostatic pressing at a pressure of 7 ton / cm ^2, under a nitrogen atmosphere at normal pressure, the temperature was raised to 1650 ° C. at 700 ° C. / h, the temperature By firing for 1 hour, a rectangular sintered body was obtained. Table 7 shows the dimensional accuracy and strength of the obtained sintered body.

Comparative Examples 5 and 6 All were manufactured under the same conditions as in Example 8 except that the control temperature of the molding die was set to the conditions shown in Table 7 to obtain a rectangular sintered body. Table 7 shows the dimensional accuracy and strength of the obtained sintered body.

Example 9 Injection molding was performed in the same manner as in Example 8 except that the same raw material as in Example 8 was used and the control temperature was changed as shown in Table 7 using the mold shown in FIG. 28. 30mmφ, length 20
A 0 mm compact was obtained, and the binder was removed and fired in the same manner as in Example 8 to obtain a round rod-shaped sintered body. Table 7 shows the dimensional accuracy and strength of the obtained sintered body.

Comparative Example 7 A round rod-shaped sintered body was obtained under the same conditions as in Example 9 except that the control temperature of the molding die was set as shown in Table 7. Table 7 shows the dimensional accuracy and strength of the obtained sintered body.

Example 10 Injection was performed in the same manner as in Example 8 except that the same raw material as in Example 8 was used and the control temperature was changed as shown in Table 7 using the mold shown in FIGS. 29a and 29b. Molding was performed to obtain a turbine rotor molded body having a tip diameter of 150 mmφ and a blade height of 100 mm. Further, binder removal and firing were performed in the same manner as in Example 8 to obtain a turbine rotor sintered body. The dimensional accuracy of the obtained sintered body is shown in Table 7.

Comparative Example 8 A turbine rotor sintered body was obtained under the same conditions as in Example 10, except that the control temperature of the molding die was set as shown in Table 7. The dimensional accuracy of the obtained sintered body is shown in Table 7.

From the above Examples 8, 9 and 10 and Comparative Examples 5, 6, 7 and 8, the control temperature of the mold was lowered from the inlet to the tip, and the temperature drop was the temperature gradient shown in FIG. If it is within the range of, the molded body temperature at the end of pressurization is ± 0 of the set temperature.
It can be seen that the temperature is within 5 ° C, the dimensional accuracy is good, and a sintered body with high strength can be obtained.

(Effects of the Invention) As described above, the present invention has the following effects.

According to the injection molding method of the present invention, since the injection molding is performed using the injection molding die in which the gate area is 20% or more of the maximum cross-sectional area of the cavity viewed from the gate side, it is possible to obtain a defect-free homogeneous molded body. .

In addition, the gate shape of the injection mold is a cavity (molded body)
If a similar figure or an approximate similar figure to the projected figure is used, it is possible to more effectively prevent the occurrence of defects in the molded body.

Further, when a molded product having a difference in wall thickness is manufactured by injection molding according to the present invention, a molded product having no defects such as weld lines and pores can be produced with a good yield by providing an injection gate that directly opens in the thick wall portion of the molded product mold. Obtainable. Further, when there are a plurality of thick portions, an injection gate having a direct opening is provided in each thick portion and injection molding is performed to obtain a similarly molded product having no defects.

Further, according to the present invention, by uniformly controlling the temperature distribution of the molded body, a homogeneous molded body can be obtained as a whole, and as a result, a dimensional accuracy is good, and a high-strength, homogeneous ceramic sintered body can be obtained. it can.

The present invention can be applied to both so-called organic molding materials and water-based molding materials and is extremely useful industrially.

[Brief description of drawings]

FIG. 1 is an explanatory view in the case of a direct gate of a molding die of the present invention, FIGS. 2a to 2d are explanatory views showing the relationship between a gate shape and a cavity (molding) projection figure, FIG. 3a and FIG. FIG. 3b is an explanatory view showing the relationship between the gate shape / cavity (molded body) maximum cross-sectional area of 90% and the projected figure of the cavity (molded body), FIGS. 4a to 4c, 5a to 5c, and FIG. Figures 6a to 6c and 7a to 7c show cavity projection figures viewed from the gate side,
Explanatory drawing showing the similar shape and the approximate similar shape, FIG. 8a is a longitudinal sectional view taken along the central axis of the molded body, and FIGS. 8b and 8c are the main views of the molding die of the molded body of FIG. 8a. Figures 9a and 9b are front and side views, respectively, of the shaped body; Figures 9c-9e are schematic side views, respectively, of the mold for producing the shaped bodies of Figures 9a and 9b. FIG. 10 is a graph showing the temperature gradient of the molding die in the present invention, FIG. 11 is a flowchart showing the injection molding of an organic injection molding material, and FIGS. 12 to 14 show the shapes of the molded body and the gate, respectively. Explanatory diagram showing, FIGS. 15 to 17 are graphs showing molding yields with respect to gate area ratios, FIG. 18 is a flow chart showing injection molding of water-based injection molding materials, and FIGS. 19 to 21 are against gate area ratios, respectively. Graph showing molding yield, Fig. 22 shows preparation of organic molding compound Another process drawing of injection molding, FIG. 23 is a schematic diagram of injection filling process of organic molding material, FIG. 24 is another process drawing of water-based molding material preparation, injection molding, and FIG. 25 is water-based FIG. 26 is a schematic view of the injection filling process of the molding material, FIG. 26 is another flow sheet showing an example of the organic injection molding method, and FIGS. 27, 28 and 29a are molding dies used in the present invention. Fig. 29b is a schematic diagram showing an example of temperature control in Fig. 29b, and Fig. 29b is a schematic diagram of the molded body viewed from the direction D in Fig. 29a. Fig. 30 is still another flow sheet showing an example of the water-based injection molding method. .

Claims (7)

(57) [Claims] 1. A ceramics injection molding method comprising injecting a ceramics molding material into a cavity of a mold through an injection molding machine through a gate, wherein the gate has at least 20 of the maximum cross-sectional area of the cavity as viewed from the gate side. Molding characterized by using a mold having an area of 100% and controlling the temperature gradient of the mold so that the temperature distribution of the molded body within the mold is within ± 0.5 ° C when the pressing is completed. Method. 2. The shape of the gate is substantially similar to the projected shape of the cavity viewed from the gate side, whereby the molding material passing through the gate is controlled to flow along the shape of the cavity. Item 1. The molding method according to item 1. 3. The cavity comprises at least one thick part and a thin part, and the gate is opened in each thick part to fill the injected molding material from the thick part to the thin part. The molding method according to claim 1 or 2. 4. The molding method according to claim 1, 2 or 3, wherein the temperature gradient of the molding die is set so as to satisfy the following inequality. x ≦ y ≦ 5x where x is the moving time (seconds) of the molding material from the gate to the temperature measurement site, and y is the temperature difference (° C.) of the mold between the gate and the temperature measurement site. 5. An injection molding die for ceramics molding, comprising: a cavity having a shape corresponding to the shape of a molded body; and a molding material introducing portion for guiding a molding material from the injection nozzle to the cavity. Further, at least 20% of the maximum cross-sectional area of the cavity is provided, and a plurality of sections extending from the vicinity of the gate of the cavity toward the inner depth are provided with heating means, temperature control means, and molded body temperature measuring means, respectively. Mold to be. 6. An injection molding die for ceramics molding, comprising: a cavity having a shape corresponding to a shape of a molded body and a molding material introducing section for guiding a molding material from an injection nozzle to the cavity, wherein the cavity has at least one wall. Comprising a thick portion and having a gate opening directly into each of said at least one thick portion, the area of said gate being at least 20% of the maximum cross-sectional area of said cavity as seen from the gate side. Molding tool characterized by. 7. The mold according to claim 5, wherein the shape of the gate is substantially similar to the projected shape of the cavity as viewed from the gate side.