JPH0449003A - Ceramic injection molding method and molding die used for said method - Google Patents

Abstract

PURPOSE:To obtain a homogeneous ceramic molded form, which is not cracked nor deformed and has high dimensional accuracy and uniform strength, by using a molding die, in which a gate has at least 20% area of the maximum cross-sectional area of a cavity, and controlling the temperature gradient of the molding die so that the temperature distribution of a molded form is kept within + or -0.5 deg.C when pressurization is completed. CONSTITUTION:A molding die, the area of a gate of which is 20% or more of the maximum cross-sectional area of a cavity viewed from the gate side, is used as an injection molding die. Consequently, a molding material passing through the gate flows along a molded form shape, and air in the cavity is discharged uniformly, thus obtaining a molded form having no defect. When a gate shape G is formed so as to be substantially a similar figure to the projection shape P of the cavity viewed from the gate side, the molding mate rial can be controlled so as to flow along the molded form shape. The temperature gradient of a mold is set so that the temperature distribution of the molded form at the time of the pressure completion of injection molding is kept within + or -0.5 deg.C, and speed where the molding material is filled is controlled.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a method for injection molding ceramics.
The present invention relates to a ceramic injection molding method for producing injection molded products with excellent performance, and a mold used therein.

(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, so in recent years, research has been conducted into using them as engine parts. It is being actively carried out. For example, radial turbine rotors made of these ceramic materials are lighter than metal rotors, can raise the operating temperature of the engine, and have excellent thermal efficiency, so they are used in automotive turbo charger rotors or gas turbine rotors. etc., is attracting attention.

Turbine rotors like this have blades with a complex three-dimensional shape, so they can be sintered with a simple shape.
For example, it is extremely difficult to finish a material with a simple shape such as a bar or square shape, such as a dense silicon nitride or silicon carbide sintered body, into a desired shape by grinding.

Ceramic molding methods include plastic molding methods that utilize the plasticity of the molding material such as extrusion molding, slurry casting molding methods that inject a slurry made by suspending ceramic coolant in water into a mold, and molding methods that involve molding the prepared powder into gold. A dry pressure molding method in which the material is placed in a mold and molded under pressure is well known. In addition to these methods, injection molding, which is often used for plastics, has recently come to be used for ceramics with irregular shapes or complex shapes.

Conventionally, in injection molding of ceramics, the raw material fine powder of ceramics itself is not plastic unlike plastics, so molding materials made by adding thermoplastic resin to the raw material fine powder and plasticized, pellets, or the applicant's JP-A-64 -2
A molding material (clay) obtained by adding water proposed in No. 4707 is used for injection molding.

That is, an organic binder consisting of a thermal 1-iT plastic resin such as polyethylene or polystyrene, a plasticizer, a dispersant, a wax, etc. is mixed with ceramic powder, and this mixed raw material is heated to give it plasticity, and then placed in a mold for molding. This is a method of injection molding, and a ceramic sintered body can be obtained by molding the obtained molded body and firing it. Another method is to mix ceramic powder with an organic binder, mainly water as a plasticizer, as a plasticizing medium, cool the mixed raw material to give it plasticity, and inject it into a mold 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, complex parts that would require a considerable number of man-hours using other methods can be quickly and precisely molded with a small amount of finishing allowance in a single operation.

However, molding materials containing these Ceramic 7 Sometimes it wasn't.

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

However, when the temperature of the molding die is kept constant, a temperature difference occurs in the molding material between the mold entrance and the tip during injection molding, resulting in uneven density distribution of the resulting molded product. As a result, cracks or deformation occurred in the sintered body produced by firing the molded body, resulting in nonuniform dimensional accuracy, strength, etc., and it was not possible to obtain a uniform sintered body.

(Problems to be Solved by the Invention) In view of the above-mentioned current situation, the inventors have conducted intensive studies on a method for homogeneously injecting molding material into a mold in ceramic injection molding, and have found that using a mold with a specific shape is effective. Furthermore, the inventors have discovered that the temperature of the molding material can be controlled to be uniform by providing a temperature gradient in the molding die, and have arrived at the present invention.

An object of the present invention is to provide a homogeneous ceramic molded body free from defects such as bores and weld lines.

Other objectives are no cracks or deformation, high dimensional accuracy,
The object of the present invention is to provide a homogeneous ceramic molded body having uniform strength.

A further object of the present invention is to provide an injection molding method for efficiently obtaining a homogeneous ceramic molded body having a complex shape with a high yield, and a mold for use in the injection molding method.

(Means for Solving the Problems) The molding method of the present invention to achieve the above object is a ceramic injection molding method comprising injecting a ceramic molding material into a cavity of a mold through a gate using an injection molding machine. A mold is used in which the front gate has an area of at least 20% of the maximum cross-sectional area of the cavity as viewed from the gate side, and the temperature distribution of the molded body within the mold is ±0. It is characterized by controlling the temperature gradient of the mold to within 5°C.

The shape of the gate of the mold used in the method of the present invention is substantially similar to the projected shape of the cavity seen from the gate side, so that the molding material passing through the gate flows along the shape of the cavity. If controlled in this way, it will be even more effective.

Further, in the case where each of the cavities has at least one thick wall portion and at least one thin wall portion, the gate may be opened in each thick wall portion so that the injected molding material is filled from the thick wall portion to the thin wall portion. preferable.

In the method of the present invention, the best effect can be obtained by setting the temperature gradient of the mold so as to satisfy the following inequality.

X≦y≦5X However, in the above formula, be.

The mold preferably used in the method of the present invention is an injection mold for ceramic molding, which comprises a cavity having a shape corresponding to the shape of the molded object and a molding material introduction part 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 viewed from the gate side, and a heating means, a temperature control means, and a molded body temperature measuring means are provided in a plurality of sections of the cavity from the vicinity of the gate toward the innermost part, respectively. It is characterized by comprising the following.

Further, when the cavity includes at least one thick walled portion, a cage is provided that opens directly into the at least one thick walled portion, and the area of the cage is determined by the maximum cross section of the cavity when viewed from the gate side. The object of the present invention can be achieved by making it at least 20% of the area.

Furthermore, it is more preferable that the shape of the gate is substantially similar to the projected shape of the cavity as viewed from the gate side.

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

In addition, "the projected shape of the cavity as seen from the gate side" means the projected shape of the cavity on a plane perpendicular to the direction of movement of the molding material passing through the gate, and is simply "
It could be called the projected figure of the cavity.

Furthermore, in the present invention, the thick part and the thin part are:
When the diameter of the largest sphere inscribed in the shape of the molded object is the maximum wall thickness of the molded object, find the diameter of the maximum diameter inscribed for each part of the molded object, and check that the diameter is 40% or more of the maximum wall thickness. A certain part is called a thick part, and a part where the thickness is less than 40% is called a thin part. A molded article having a plurality of thick portions refers to a molded article having one or more of the thin portions between the thick portions.

(Function) Hereinafter, the structure of the present invention, its function, and specific embodiments will be described in detail.

Ceramic injection molding involves pushing pellets or molding materials (hereinafter referred to as molding material) into an injection mold using a plunger or screw of an injection molding machine. An injection mold generally consists of a cavity that corresponds to the shape of the molded object, and a molding material introduction section that includes a sprue, a runner, and a gate that guides the molding material from the injection nozzle into the cavity. It is preferable that the slope of the sprue and runner is usually about 2 to 10°.

The ceramic injection molding method of the present invention uses a mold whose gate area is 20% or more of the maximum cross-sectional area of the cavity as viewed from the gate side. When the gate area is 20% or more of the maximum cross-sectional area of the cavity as viewed from the gate side, the molding material passing through the gate will flow along the shape of the molded object, and the air in the cavity will be discharged uniformly, resulting in a molded object without defects. is obtained. On the other hand, if an injection mold with a ratio of less than 20% is used, the molding material that has passed through the gate will not flow along the shape of the molded object, resulting in uneven air discharge within the cavity, resulting in defects such as bores and weld lines in the resulting molded object. occurs, and the yield of molded products becomes poor.

Generally, a gate refers to an entrance through which 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, part of the sprue or part of the runner and the cavity (product part) 2 are separated,
In some cases, it may not be possible to specify the Kate part. In such a case,
It is preferable that the G part, which is a part of the product part 2 close to the nozzle part l, be regarded as the gate, and the gate cross-sectional area in such a case should be the G part cross-sectional area.

Furthermore, in the case of the present invention, if the molding mold is formed so that the shape G of the injection mold is substantially similar to the projected shape P of the cavity viewed from the gate side, that is, the shape is similar or approximately similar, the molding material that passes through the gate can be controlled so that it flows along the shape of the molded object, and defects that occur in the molded object can be more effectively prevented. This effect becomes particularly significant as the gate cross-sectional area increases. In the above case, it is preferable that the cage is provided at the center of the cage mounting surface of the cavity. In FIGS. 2a to 2d, when A is the minimum width and B is the maximum width in the non-overlapping portion of the gate cross-sectional shape G and the projected shape P of the cavity, 2c and 2d, if they are substantially similar to each other as shown in FIGS.
Compared to the case of non-similar shapes as shown in the figure, the value of B/A is smaller (approaches l), so the filling rate of molding material into parts A and B remains almost constant, and the air is discharged from the cavity. This is because the molded product is uniform and has no defects. On the other hand, if <B/A is large, as in the case of non-similar shapes, the filling speed in the A part is faster and the filling speed in the B part is slower, so the air in the cavity is discharged irregularly, resulting in a defect that causes air to be drawn into the molded body. becomes.

Furthermore, for example, the relationship between similar shapes (FIGS. 2a and 2b) and dissimilar shapes (FIGS. 2c and 2d) is as shown in Table 1. Note that the gate area/cavity (molded body) maximum cross-sectional area is 50%.

Table 1 Also, as shown in Figures 3a and 3b, even if the gate area/cavity (molded body) maximum cross-sectional area is 90% and the same, in the case of Figure 3b, the gate protrudes beyond the cross-sectional area of the molded body. It can be seen that similar shapes are superior. Furthermore, as the cross-sectional area of the gate increases, the B/A value of gates with similar shapes becomes smaller than the B/A value of gates with dissimilar shapes.

From this, it can be seen that the use of gates with a large cross-sectional area and similar shapes is more effective in discharging air within the cavity evenly.

Throughout this document, regarding the cross-sectional shape of the gate, a substantially similar shape, that is, a similar shape or an approximately similar shape means a shape as shown in FIGS. 4a to 7C, for example. In FIGS. 4a to 7C, P indicates a cavity projected figure as seen from the gate side, and G and G' indicate gate shapes similar and approximately similar thereto, respectively. For example, the shapes P, G, and G' in FIGS. 4a to 40 are all considered to be circular, but as to the rectangles shown in FIGS. 5a to 5c, a shape such as G' is considered to be an approximately similar shape. Polygon,
For example, in the case of a hexagonal shape as shown in FIG. 6a, the circle G in FIG. 6C is regarded as an approximately similar shape, since the B/A value becomes extremely small. When the cavity projected figure P seen from the gate side is a polygon (triangle or more), if any angle (θ) is 120° or more, a circle like G' may be used as an approximate similar figure. Furthermore, for a complex shape P like the turbine rotor shown in Fig. 7a, it is acceptable to use a similar shape G as shown in Fig. 7b, or it may be difficult to make a mold, or it may cause molding in part of the sprue or part of the runner. Since the fluidity of the material may deteriorate, the shape P as shown in Figure 7c is
It may also be a polygonal shape such as a nonagonal G' connecting the blade tips 3 of the wing parts 4, and in a nonagonal shape, the angle (θ) or 1
Since the angle is 40°, it may be circular.

In a mold for a ceramic molded body consisting of multiple parts with different wall thicknesses, the inlet to the molded body, that is, the gate, opens directly into the enlarged part (thick part) of the cavity corresponding to the thickened part of the molded body. It is preferable to arrange it like this. For example, when injection molding a molded body M1 as shown in FIG. 9a, in conventional injection molding, the sprue S and gate G arrangement method as shown in FIG. 9b is usually considered. The mold of the invention is provided with an injection gate G in the thick part 5 of the cavity as shown in Fig. 9c, and a part of the sprue is gradually made thicker along the shape of the molded body, and the molding material is applied from the thick part to the molded body. It is injected and molded inside.

By arranging the gate so as to open directly into the thick part of the cavity, the molded body obtained is as shown in Figures 6 and 24 on page 122 of ``Fine Ceramics Injection Molding Technology'' (published by Nikkan Kogyo Shimbun). This prevents the occurrence of defects such as welt lines and bore entrainment due to wet ink, which were observed in the conventional method as shown in Figures 6 and 27 on page 123. These reasons are due to the lack of fluidity of the material, as the molding material is injected thickly from the thick part along the shape of the molded object, so that the molding material does not cause ink, and the material does not cool easily and maintains its fluidity for a long time. This is because it can prevent welt lines from occurring.

In addition, a mold for a ceramic molded body having a plurality of thick portions with different wall thicknesses, for example, a molded body M2 whose front view and side view are shown in FIG. 10a and FIG.
' and 5'', as shown in Figure 10c or Figure 10d, sprue S and gate G
Or, as shown in Fig. 10e, it is conceivable to arrange the sprue S, runners R and R', and gates G and G'. Injection cages 1-G and G' are provided at 5' and 5'', and thick parts 5' and 5 of the molded body are inserted from each injection gate G and G'.
In this case, it is preferable to maximize the amount of molding material injected into at least one of the plurality of thick parts. This is because defects such as bores and weld lines can be prevented by joining molding materials at thicker parts than at thinner parts.For example, in Fig. 10e, gate G
By making the diameter of the runner R to the gate G' larger than that of the runner R' to the gate G', or by making the distance of the runner R connected to the sprue S shorter than that of the runner R', injection into the thick part 5' can be performed. The amount can be controlled to be greater than the amount injected into the thick portion 5'. Of course, in this case, even if the runners have the same shape and length, there is no need to control if there is no bonding of the molding material at the thin portion.

Furthermore, the introduction part of the mold of the present invention, that is, the injection sprue gate or the injection sprue, the runner, and the gate, may have a constant taper in the continuous part from the injection gate to the sprue or in a part of the runner. Particularly in the case of a sprue/gate consisting of a sprue and a gate, it is preferable to have the above-mentioned taper. The taper angle may be appropriately selected depending on the molding material used, but is generally about 1 to 10°. The reason for providing the taper is to spread the injected molding material so that it flows smoothly from the nozzle of the injection molding machine through the gate into the cavity, that is, the molded body, and to enable smooth release from the mold.

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 injection molding is within ±0.5°C. For this purpose, for example, there is a method of setting the temperature of the mold so that it has a gradient from the gate part G to the tip of the mold, or a method of controlling the speed at which the molding material is filled into the mold (injection speed). be. As a specific example of the present invention, as shown in FIG. When the temperature difference is y (° C.), the temperature gradient of the mold is set so that X≦y≦5x. The reason for the range of y=x to y=5x is: ■The type and amount of organic binder in the molding material;
Or, the specific heat or thermal conductivity of the molding material differs depending on the type and amount of ceramic powder added, (2) the shape and wall thickness of the molded body differs, (2) molding conditions, etc. differ, etc.

Since a molding material with a large specific heat and a low thermal conductivity is not easily affected by the mold temperature, the mold temperature difference y can be made small even if the molding material arrival time X is long, for example, y=x. or,
Molding materials with low specific heat and high thermal conductivity are easily affected by the mold temperature, so if the molding material arrival time X increases, the mold temperature difference y must be increased, for example, y =
It becomes 5x.

More specifically, for example, the composition of the ceramic material is 48-60vo 1% ceramic powder, 52-40vo 1% organic binder, and the composition of the organic binder is 3-15wt% with a molecular weight of 10,000-50,000, and a molecular weight of 3-15wt%. 20
0 to 1000 or 85 to 97 wt%, and the molding conditions are molding material temperature 60 to 80 ° C, mold temperature 440 to 52
℃, the range of X≦y≦5x is preferable.

When the mold temperature gradient is set as described above, the temperature of the entire injection molded product is 20,000 yen, regardless of the part.
The temperature is approximately uniform within 5° C., which is preferable for the production of a homogeneous molded body and the subsequent production of a homogeneous sintered body. If the temperature distribution of the compact exceeds the set temperature of 0.5°C, the density distribution of the obtained compact will become uneven, and as a result, the sintered compact obtained by firing the compact will have cracks or deformation. etc., resulting in non-uniformity in dimensional accuracy and strength, making it difficult to obtain a uniform sintered body.

Further, the point at which it is necessary to check that the temperature distribution of the molded body is within ±0.5° C. of the set temperature is at the end of pressurization. in general,
In injection molding, after filling the molding material, high pressure is applied for a predetermined period of time.
Next, the molded product is held at low pressure for a predetermined time in order to impart a shape to the molded product or to prevent defects such as sink marks occurring inside the molded product. The term “completion of pressurization” refers to when the high-pressure pressurization process, which is carried out for the above-mentioned predetermined period of time, ends.

In the injection molding method using an organic binder, in which a large amount of organic binder such as binder, wax, lubricant, etc. is added to the raw material blended powder and kneaded, the temperature of the injection molding material 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 decreases as it goes from the gate to the tip. In order to compensate for this and keep the temperature of the molded body constant, the preferable temperature conditions for the mold as described above are such that the temperature of the mold increases from the gate part to the tip part. The method for heating the mold may be, for example, using a boat-type heater (rod, band, etc.) or using a liquid (water, oil).

In addition, in injection molding methods that use clay made by adding a small amount of organic binder and mainly water to the raw material blended powder, the temperature of the clay (molding material) is lower than the mold temperature. The temperature of the molding material increases as it goes from the gate to the tip. In order to compensate for this temperature difference and keep the temperature of the molded object constant, the temperature of the mold is lowered from the gate to the tip.

The ceramic powder used in the present invention includes conventionally known oxides such as alumina and zirconia, as well as
Examples include nitrides such as silicon nitride, carbides such as silicon carbide, known as so-called new ceramics, and composite materials thereof.

The molding materials include injection molding materials (pellets) that use an organic binder as a plasticizer, and water as a plasticizing medium.
Injection molding material that uses an organic binder as a plasticizer (kando)
Any of these can be used.

(Examples) Hereinafter, the present invention will be explained 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 explained according to the flowchart shown in FIG.

After preparing 100 parts by weight of ceramic raw material (313N4) powder with 2 parts by weight of SrO, 3 parts by weight of MgO and 3 parts by weight of Cen2 as sintering aids, water was added to this mixture in an attritor to reduce the average particle size. Wet mixing and pulverization were carried out to a diameter of 0.5 μm. Next, this was spray-dried to obtain granules with an average particle size of 30 μm, and then 2.5 ton/c
The mixture was granulated by isostatic isostatic pressurization at a pressure of t.

Next, after crushing the granules to an average particle size of 30 μm, 3 parts by weight of a binder (ethylene vinyl acetate copolymer) and a plasticizer (paraffin wax) are added to 100 parts by weight of the obtained powder.
15 parts by weight and 2 parts by weight of a lubricant (stearic acid) were added and kneaded, extruded using an extruder to form pellets, and then pelletized at a material temperature of 68°C, a mold temperature of 50°C, and an injection pressure of 400°C.
kglcrl and an injection speed of 200 cc/sec using an injection mold having the shape shown in Table 2 to obtain molded bodies of M, M, MS shown in FIGS. 13 to 15. . Note that the turbine rotor, which is the molded body M5 in FIG.
) was taken as the maximum cross-sectional area.

The results are shown in Table 2 and Figures 16 to 18.

Table 2 (Note) The molding results show the proportion of non-defective products among 10 molded bodies.

Example 2 Injection molding using clay will be explained according to the flowchart shown in FIG.

The steps of raw material preparation, mixing and pulverization, and spray drying were carried out in the same manner as in Example 1. Granules with an average particle diameter of 30 μm were obtained through a spray drying process, and then 100 μm of these granules were obtained.
To the parts by weight, 1 part by weight of surfactant Cedran FF-200 (manufactured by Sanyo Chemical Industries, Ltd., trade name), 7 parts by weight of a plasticizer (methyl cellulose), and 30 parts by weight of water were added and kneaded. Next, this kneaded material was subjected to vacuum kneading at a vacuum degree of 70 mmHg to obtain a kneaded clay with a diameter of 52 mm and a length of 500 mm.
Hydrostatic isostatic pressurization was performed at a pressure of 5 ton/cf. Next, this was carried out at a material temperature of 12°C, a mold temperature of 60°C, an injection pressure of 300 kglcrd, and an injection speed of 200 cc/s.
M6.EC as shown in FIGS. 13 to 15 was formed by injection molding using an injection mold having the shape shown in Table 3 under the conditions of EC. M? ,M,
A molded body was obtained. The results are shown in Table 3 and Figures 20 to 22.
As shown in the figure.

Table 3 (Note) The molding results show the proportion of non-defective products among 10 molded bodies.

As is clear from the above results, if an injection mold is used that has a gate area or a maximum cross-sectional area of the cavity viewed from the gate side of 209oJd, it is possible to mold a molded product without defects such as bores and welt lines. , the molding yield is significantly improved. Furthermore, as the cake area ratio increases, the molding yield of similar shapes or approximately similar shapes improves.

Example 3 Injection molding of an organic molding material will be explained according to the process diagram shown in FIG.

The raw material was prepared by mixing 100 parts by weight of Si3N, a ceramic raw material, and 2 parts by weight of SrO powder, 3 parts by weight of MgO powder, and 3 parts by weight of Ce07 as sintering aids, and adjusting the average particle size to 0.
It was ground to 5 μm. Next, it was spray-dried to obtain granules with an average particle size of 30 μm. The granules were pressurized at a pressure of 3i y'crl using a hydrostatic isostatic pressurization method.

After pressurizing, ■ a method of crushing and re-reducing the average particle size to 30 μm (method ■), ■ a method of calcining in the atmosphere at 450°C for 5 hours, and then crushing it to an average particle size of 30 μm (method ■) ) were prepared in two ways.

After crushing, 100 parts by weight of the obtained powder, 3 parts by weight of binder,
15 parts by weight of a plasticizer and 2 parts by weight of a lubricant were mixed and kneaded using a kneader to obtain an organic molding material. The obtained molding material was made into pellets of 7+ and up using an extruder.

The obtained pellets are molded using an injection molding machine,
Mold M for the molded product shown in Figures 0a and 1Ob, respectively.
Injection filled into I rM2. The filling method for the molded body M is as follows:
This was carried out using the molds shown in FIGS. 9b and 9c, and the methods were designated as filling method 1 and filling method 2, respectively. . The angle of the sprue part for filling method 1 was 2° and for filling method 2 it was 5°. The filling method for the molded body Mho is as follows. The taper angle of a part of the sprue of filling method 3 was carried out using the molds shown in Fig. Oc, Fig. 1 Ob, and Fig. 10e, and filling method 3, filling method 4, and filling method 5 were used, respectively. The taper angle of part of the 4th sprue was 5°. In filling method 5, the lengths and diameters of lunkers R and R' were the same, and the taper angles were both 5 degrees.

The diameter of runner R is smaller than that of runner R', the taper angle of runner R is 5°, and the taper angle of runner R' is 10' to control the flow rate of the molding material. Filling method 6
And so. A schematic diagram of each filling process is shown in FIG. 24, and the molding results are shown in Table 4.

As can be seen from the schematic diagram of the filling process in FIG.
In , filling method 1 in which the molding material is filled from the thin part of the molded body is undesirable because jetting of the molding material occurs in the thick part. On the other hand, filling method 2 in which the molding material is filled from the thick part of the molded body M along the shape of the molded body is preferable because jetting does not occur and the material is filled uniformly, and furthermore, the molding method shown in Table 4 is Yield has also improved.

Moreover, the molded body Mi has a plurality of thick parts 5', 5'.

In the case of filling methods 3 and 5 in which the molded body is filled from one of the thicker parts, the other thicker part is filled from the thinner part, resulting in the same problem as the above filling method 1. I know it's not good.

On the other hand, filling methods 5 and 6, in which the molding material is filled from both the thick parts 5' and 5', are preferable because the molding material is filled uniformly, and as shown in Table 4, the molding yield is improved. Furthermore, compared to Filling Method 5, since the molding material was adjusted so that the joining was performed in the thick part, defects were less likely to occur, resulting in favorable results.

Example 4 Injection molding of a water-based molding material will be explained according to the process diagram shown in FIG. 25.

Example 3: raw material preparation, mixing and pulverization, and spray drum/up to
I did the same thing. 100 parts by weight of granules with an average particle diameter of 30 μm obtained by spray try, 30 parts by weight of water, 7 parts by weight of binder and 1 part by weight of surfactant were mixed and kneaded in a kneader to form a water-based molding material. Obtained. The obtained aqueous molding material was formed into a cylinder with a diameter of 52 mm and a length of 340M using a vacuum extruder, and the cylindrical molding material was pressed using a rubber press.2.
Isostatic pressure was applied at a pressure of 5 t/ci. The obtained aqueous molding material was injection molded into molded bodies M1 and MI2 using an injection molding machine in the same manner as in Example 3.

A schematic diagram of each filling process is shown in FIG. 26, and the molding results are shown in Table 5. From these results, it can be seen that almost the same results as the organic molding material of Example 3 can be obtained.

Table 5 Example 5 An injection molding process using an organic binder was carried out. Hereinafter, a description will be given according to a flow sheet showing an injection molding method using an organic binder shown in FIG. 27.

To 100 parts by weight of silicon nitride powder as a ceramic raw material, 2 parts by weight of SrO, 3 parts by weight of Mg0, and 3 parts by weight of CeO□ were added as sintering aids, and these were ground and mixed to give an average particle size of 0.5μ. After forming a blind blended powder and then spray drying to obtain granules with an average particle size of 30 μm, 2.5
The pellets were granulated by isostatic isostatic pressurization at a pressure of ton,/crtl, and the pellets were crushed to obtain particles with an average particle size of 30 μm. Next, with respect to 100 parts by weight of this mixed powder, binder:
3 parts by weight, 1 part by weight of wax, 1 part by weight of wax, and 2 parts by weight of lubricant are added and kneaded to form pellets, which are then made into pellets at a material temperature of 68°C, an injection pressure of 400 kg/crl, and an injection speed of 100 to 300 cc/sec. , pressurization time 15 seconds
Then, X, Y depending on the mold temperature shown in Table 6.

Injection molding was performed in a molding die shown in FIG. 28 while controlling the temperature of each part of Z. 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 as seen from the gate side. As a result, a molded body having a length of 150 mm, a width of 65 nm, and a thickness of 15 mm was obtained. The temperature of the molded body at that time was set to 6.
Shown in the table.

Here, the mold shown in FIG. 28 includes a thermocouple t for mold temperature control.
o, 10', 10', thermocouple 11°11', 11' for measuring the temperature of the molded body, and heater 1 for heating the mold.
2.12'.

12' is provided to control the mold temperature and measure the temperature of the molded body. In addition, G is the mold cage (inlet part), 13,
13' and 13'' indicate pressure detection sensors in the mold.

The temperature and pressure sampling interval of these sensors is l
It was performed in 0μsec.

Next, the molded body was heated to 40006 at a heating rate of 1 to 3°C/h, and held at that temperature for 5 hours to perform a degreasing treatment.
Then, after applying isostatic pressure at a pressure of 7 tons/car, sintering was performed at 1700° C. for 1 hour in a nitrogen atmosphere at normal pressure to obtain a square 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 conditions shown in Table 6, and 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 materials as in Example 5, molding was performed using the mold shown in FIG. 29. 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 as seen from the gate side.

Injection molding was carried out in the same manner as in Example 5, except that the control temperature of the mold was changed as shown in Table 6, to obtain a molded product with a diameter of 30 mmφ and a length of 200 mm, and further in the same manner as in Example 5. Degreasing and firing were performed to obtain a round bar-shaped sintered body. Table 6 shows the dimensional accuracy and strength of the obtained sintered body.

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

Example 7 The same raw materials as in Example 5 were used, and the product had at least one thick walled portion as shown in FIGS. Using a mold whose gate area is 20% or more of the maximum cross-sectional area of the cavity as seen from the gate side, the control temperature is
Except for the changes shown in the table, injection molding was carried out in the same manner as in Example 5 to obtain a turbine rotor molded body with a tip diameter of 150 mm and a blade height of 100 mm, which was then degreased and fired in the same manner as in Example 5. A turbine rotor sintered body was obtained. Table 6 shows the dimensional accuracy of the obtained sintered body.

A sintered body of a turbine rotor was obtained by manufacturing under the same conditions as in Example 7, except that the control temperature of the mold for forming the twister was set to the conditions shown in Table 6. The dimensional accuracy of the obtained sintered body was
Shown in the table.

As is clear from the above Examples 5 to 7 and Comparative Examples 1 to 4, the control temperature of the mold was increased from the inlet to the tip, and the temperature increase had a temperature gradient as shown in Fig. 11. When the temperature falls within this range, the temperature of the compact at the end of the pressurization will be within ±0.5°C of the set temperature at any location, indicating that a sintered compact with good dimensional accuracy and high strength can be obtained. .

An injection molding method was carried out using Inusedo Eingdo. A description will be given below according to the flow sheet of the water-based injection molding method shown in FIG.

To 100 parts by weight of silicon nitride powder as a ceramic raw material, 2 parts by weight of SrO and 3 parts by weight of CeO were added as sintering aids, and these were pulverized and mixed to obtain an average particle size of 0.6 μm.
The mixture was prepared into a powder, and then spray-dried to obtain granules with an average particle size of about 30 μm. To 100 parts by weight of the granules, 8 parts by weight of an organic binder (Mef cellulose: 7 parts by weight, Cedran FF-200: 1 part by weight) and approximately 30 parts by weight of water were added and kneaded, and then kneaded under vacuum. 70mmH
Vacuum clay kneading was carried out at 100 g to obtain a clay having a diameter of 52 mm and a length of 500 mm. This was subjected to isostatic pressurization at a pressure of 2.5 ton/d, and then boiled overnight in a cool, dark place at a temperature of 12°C.
Next, the clay temperature is 12℃ and the injection pressure is 150-300 kg/
cnr, injection speed 1oo to 3oocc/sec, gel curing time 1 to 3 minutes, and x depending on the mold temperature shown in Table 7.
While controlling the temperature of each part of y and z, injection molding was carried out in the mold shown in FIG.
A molded body having a diameter of 0+ nm, a width of 65 mm, and a thickness of 15 fflffl was obtained. Table 7 shows the temperature of the molded body at that time.

Next, the molded body was heated in a constant temperature and humidity chamber at a temperature of 60°C to 100°C.
℃, lowered the humidity from 98% to 20% and dried, then raised the temperature to 500℃ at a heating rate of 50℃/h,
The binder was removed by holding at that temperature for 5 hours, followed by isostatic pressurization at a pressure of 7 ton/cnr, and then heated to 1650°C at 700°C/h under a nitrogen atmosphere at normal pressure.
The temperature was raised to 100.degree. C., and firing was performed at that temperature for 1 hour to obtain a square sintered body. Table 7 shows the dimensional accuracy and strength of the obtained sintered body.

Comparative Examples 5 and 6 A rectangular sintered body was obtained by manufacturing 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. The dimensional accuracy and strength of the obtained sintered body were
Shown in the table.

Example 9 Using the same raw materials as in Example 8, injection molding was carried out in the same manner as in Example 8, except that the mold shown in Figure 29 was used and the controlled temperature was changed as shown in Table 7. A molded body with a diameter of 30 mm and a length of 200 mm was obtained, and the binder was removed and fired in the same manner as in Example 8 to obtain a round bar-shaped sintered body. Table 7 shows the dimensional accuracy and strength of the obtained sintered body.

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

Using the same raw materials as in Example 8, Figure 30a and Figure 30
Injection molding was carried out in the same manner as in Example 8, except that the mold shown in Figure b was used and the controlled temperature was changed as shown in Table 7, to produce a molded turbine rotor with a tip diameter of 150 wlφ and a blade height of about 100. Further, the binder was removed and sintered in the same manner as in Example 8 to obtain a sintered body of a turbine rotor.

Table 7 shows the dimensional accuracy of the obtained sintered body.

Comparative Example 8 A sintered body of a turbine rotor was obtained by manufacturing under the same conditions as in Example 10 except that the control temperature of the molding die was set to the conditions shown in Table 7. Table 7 shows the dimensional accuracy of the obtained sintered body.

Example 8 above. 9. to and Comparative Examples 5 and 6°7.8, if the control temperature of the mold is lowered from the inlet to the tip, and the temperature drop is within the range of the temperature gradient shown in Figure 11. The temperature of the compact at the end of the pressurization was within ±0.5°C of the set temperature, indicating that a sintered compact with good dimensional accuracy and high strength was obtained.

(Effects of the Invention) As explained above, according to the present invention, the following effects can be achieved.

According to the injection molding method of the present invention, since injection molding is performed using an injection mold whose gate area is 20% or more of the maximum cross-sectional area of the cavity as seen from the gate side, a homogeneous molded product without defects can be obtained. .

Moreover, if the gate shape of the injection mold is made similar or approximately similar to the projected figure of the cavity (molded body), it is possible to more effectively prevent the occurrence of defects in the molded body.

Furthermore, when molded bodies with different wall thicknesses are produced by injection molding according to the present invention, by providing an injection gate that opens directly into the thick part of the molded body, molded bodies without defects such as weld lines and bores can be produced with a high yield. Obtainable. Also,
When there are a plurality of thick parts, a molded article without defects can be similarly obtained by providing an injection gate that opens directly in each thick part and performing injection molding.

Furthermore, 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,
It is possible to obtain a ceramic sintered body with good dimensional accuracy, high strength, and homogeneity.

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

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the direct gate of the mold of the present invention, Figs. 2a to 2d are explanatory diagrams showing the relationship between the gate shape and the cavity (molded body) projected figure, and Fig. 3a and Fig. Figure 3b is an explanatory diagram showing the relationship between the gate shape and the cavity (molded body) projected figure in which the gate area/cavity (molded body) maximum cross-sectional area is 90%; Figures 6a to 60 and Figures 7a to 70 are explanatory diagrams showing a cavity projected figure, a similar shape, and an approximate similar shape, respectively, as seen from the gate side; Figure 9a is a longitudinal cross-sectional view along the central axis of the molded body; Figures 9b and 9c show the factors involved in the molding die of the molded body in Figure 9a, Figures 10a and 10b are front and side views of the molded body, respectively, and Figures 1Oc to 10e are 10a and 10e. Fig. 10b is a schematic side view of a mold for producing a molded article, Fig. 11 is a graph showing the temperature gradient of the molding die in the present invention, and Fig. 12 is a graph showing the temperature gradient of the molding die in the present invention. Flowchart showing injection molding, Figures 13 to 15 are explanatory diagrams showing the shapes of the molded body and gate, respectively, Figures 16 to 18 are graphs showing molding yield with respect to gate area ratio, Figure 19 is water-based injection Flowchart showing the injection molding of the molding material, Figures 20 to 22 are graphs showing the molding yield versus gate area ratio, Figure 23 is another process chart for preparing the organic molding material and injection molding, Figure 24 is a schematic diagram of the injection filling process of an organic molding material, Figure 25 is another process diagram of the preparation and injection molding of a water-based molding material, and Figure 26 is a schematic diagram of the injection filling process of a water-based molding material.
FIG. 28, FIG. 29, and FIG. 30a are schematic diagrams showing examples of temperature control in a mold used in the present invention, and FIG. 30b is a flow sheet showing an example of an organic injection molding method. 30a is a schematic view of the molded article seen from direction D in FIG. 30a, and FIG. 31 is yet another flow sheet showing an example of the water-based injection molding method. FIG, / FIG, 3σ FIG, 3b F7G-4σ FIG, 4b FIG, 4c FIG, 9σ FIG, 9b FIG, 9c FIG, 6σ FIG, 6b FIG, 6c l6-ll Betsuto - Shi 1゛Darkness (sec
) FIG, /2 FIG-16 FIG, l7 FIG, 18 FIG, /3 FIG, /4 FIG, 15 FIG, I9 FIG-20 FIG, 21 Eid itt poor APC%] FIG, 24 Ta-order 1 Mt. =door:::mei;2 X2:wide;2FI6.23 FIG, 25 FI6.26 Previous customer Ill! dLjL tz tz Jau-I-+-Meiichi = Iiji Kyoyumiji Ko Wataru: Koyo Nito Yoji Omifuji Fu Nuriji Ko Rinji FI6.28 FIG, 29 C FIG, 30σ FIG, 30b

Claims (1)

[Claims] 1. In a ceramic injection molding method comprising injecting a ceramic molding material into a cavity of a mold by an injection molding machine through a gate, the gate has a maximum cross-sectional area of the cavity when viewed from the gate side. at least 2 of
A mold having an area of 0% is used, and the temperature gradient of the mold is controlled so that the temperature distribution of the molded object within the mold is within ±0.5°C at the end of pressurization. molding method. 2. The shape of the gate is substantially similar to the projected shape of the cavity as seen from the gate side, so that the molding material passing through the gate is controlled to flow along the shape of the cavity. Molding method. 3. Each of the cavities includes at least one thick wall portion and at least one thin wall portion, and the injected molding material is filled from the thick wall portion toward the thin wall portion by opening the gate in each thick wall portion. Molding method 1 or 2. 4. The molding method according to claim 1, 2 or 3, wherein the temperature gradient of the mold is set to satisfy the following inequality. x≦y≦5x However, x is the travel 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. In an injection mold for ceramics molding comprising a cavity having a shape corresponding to the shape of the molded object and a molding material introduction part for guiding the molding material from the injection nozzle to the cavity, the area of the gate is the size of the cavity when viewed from the gate side. 20% of the maximum cross-sectional area of the cavity, and a plurality of sections extending from the vicinity of the gate to the innermost part of the cavity are each provided with a heating means, a temperature control means, and a molded body temperature measuring means. Type. 6. An injection mold for ceramics molding comprising a cavity having a shape corresponding to the shape of the molded object and a molding material introduction part for guiding the molding material from the injection nozzle to the cavity, wherein the cavity has at least one thick part. and further comprising a gate that opens directly into each of the at least one thickened portion, and the area of the gate is at least 20% of the maximum cross-sectional area of the cavity when viewed from the gate side. Molding mold. 7. The mold according to claim 5 or 6, wherein the shape of the gate is substantially similar to the projected shape of the cavity viewed from the gate side.