JPH075415B2 - Method for manufacturing ceramic rotating body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a rotating body having a shaft portion and a rotor portion (wing portion) such as a vehicle turbine wheel.

(Prior Art) There is known a turbine wheel for a vehicle in which a rotor portion is made of ceramic. When the rotor portion is made of ceramic in this way, the shaft portion and the rotor portion, which have a large difference in coefficient of thermal expansion, must be joined. Therefore, in Japanese Patent Publication No. 60-255678, Wc-Co The rotor portion is fitted to the shaft portion using the alloy plate as a buffer layer, and the rotor portion is fitted to the shaft portion through the brazing layer in Japanese Utility Model Laid-Open No. 61-200401. In this case, the rotor portion and the shaft portion are screwed together, and in JP-A-62-119177, the rotor portion and the shaft portion are screwed together.

(Problems to be Solved by the Invention) Among the above-mentioned conventional techniques, in the case of joining via a buffer layer or a brazing layer, it is not effective unless the thickness of each of these layers is increased to some extent, and at high temperatures. If so, these layers cause oxidative deterioration, thermal deterioration, and electrical corrosion deterioration.

On the other hand, when the rotor portion and the shaft portion are screwed or pin-joined, it is difficult to perform processing such as thread cutting after firing the ceramic molded body because the hardness is high and it is difficult to attach the screw portion and the like before firing. It can be said that the molding is practically not applicable in consideration of the fact that the dimensions are greatly changed after firing.

(Means for Solving the Problems) In order to solve the above problems, according to the present invention, after the shaft portion of the rotating body and at least the boss portion of the rotor portion are integrally formed of a ceramic material, pores are formed in the formed body. Was formed, and then the molten metal of the matrix metal was press-fitted or impregnated into the pores.

(Function) Since there is no joint interface between the rotor part and the shaft part, there is no crack due to the difference in thermal expansion, and the thermal conductivity is poor in the ceramic unit, which is disadvantageous in terms of cooling, but metal is filled in the pores. By doing so, the thermal conductivity is also improved.

(Example) Below, the Example of this invention is described based on an accompanying drawing.

FIG. 1 is a block diagram showing the method of the present invention in the order of steps. In the present invention, first, a ceramic powder, a firing aid,
The pore forming powder and the conductive substance are mixed and mixed, and the mixed powder is subjected to pressure molding, slip casting or injection molding to integrally form the shaft portion and the rotor portion of the turbine wheel.

Here, as the ceramic powder, for example, Si ₃ N ₄ , Al ₂ O ₃ , Zr
An insulating material such as O ₂ or sialon is used, and as the conductive powder added to facilitate later electric discharge machining, one having conductivity from the beginning and one exhibiting conductivity by firing, for example, Ti, Zr , Hf, Ta, W, Mo, Cr, Nb, and other carbides, nitrides, borides, carbonitrides, and mixtures thereof are used, and the addition amount is such that the resistivity of the sintered body after firing is 10 Ωcm or less. So that As the sintering aid powder, Al ₂ O ₃ , Y ₂ O ₃ , MgO, SiO ₂ or the like is used alone or as a mixture, and as the pore forming powder, a glassy material having a diameter of 1 to 5 μm and soluble in an acid Powder is used, and the specific component ratios are as follows.

SiO ₂ 20-35 wt% B ₂ O ₃ 35-50 wt% Na ₂ O 12-25 wt% K ₂ O 3-10 wt% Al ₂ O ₃ 2-12 wt% MgO 3-14 wt% Next, dry and degrease the molded body After that, calcination is performed. The preliminary firing may be omitted and the main firing may be performed immediately.

When calcination is performed, it is performed at 1000 to 1400 ° C. for about 30 minutes to 2 hours. Then, this calcination melts the vitreous pore-forming powder, takes in the impurities present at the grain boundaries of the ceramic powder into the glass, and removes the impurities together when the pore-forming powder is later eluted with an acid. To do.

When the calcination is completed as described above, the elution treatment with acid is performed. The acid used is HNO ₃ , Hcl or H ₃
Add a small amount of PO ₄ , HF, organic acid, etc., or use a mixture. Next, the formed body having a three-dimensional network structure obtained by eluting the pore-forming powder is fired. Baking temperature 1600-2200
Do it for about 2 hours at ℃.

After that, the sintered body having the three-dimensional mesh structure is subjected to electric discharge machining, ultrasonic machining, grinding with a diamond grindstone, etc.
A ceramic molded body 1 as shown in the figure is obtained. The molded body 1 is composed of a shaft portion 2 and a rotor portion 3, and an engaging recess 4 for coupling to another metal shaft or the like is formed at an end portion of the shaft portion 2,
Further, a large diameter portion 5 is formed on the outer circumference of the shaft portion 2 near the rotor portion 3, and a groove 6 for fitting a seal ring is formed around the large diameter portion 5. The molded body 1 has a porosity of 10 to 30.
It is preferable that pores having a diameter of about 1 to 10 μm are uniformly formed.

The molded body 1 obtained as described above is set in a mold, and the molten metal of the matrix metal is injected under pressure into the mold to press or impregnate the molten metal into the pores of the molded body 1 and solidify the molten metal. By squeezing, as shown in FIG. 3, the rotating body 7 in which the ceramic metal and the composite are combined is obtained.

FIGS. 4 to 6 are views showing another embodiment. In the embodiment shown in FIG. 4, the ceramic molded body 1 is formed up to the boss portion 3a of the rotor portion 3, and the wing portion 3b is formed. Only metal is used. Further, in the embodiment shown in FIG. 5, the ceramic is not exposed at the neck portion of the rotor portion 3. In both of the embodiments shown in FIGS. 4 and 5, the ceramic is not exposed. It is suitable to uniformly disperse the pores and to set the pore diameter to 1 to 10 μm and the porosity to 10 to 30%.

On the other hand, in the embodiment shown in FIG. 6 (A), the pore diameter and the porosity are gradually changed as shown in FIG. 6 (B) to prevent the concentration of thermal stress and pore stress.

Next, an experimental example in which specific numerical values are given is shown.

[Experimental Example 1] Silicon nitride powder with a maximum particle size of 5 μm (average particle size 0.5 μm) 50
Parts by weight, Y ₂ O ₃ (maximum particle size 1.0 μm, average 0.4 μm), Al ₂ O ₃
(Maximum particle size 1.0 μm, average 0.4 μm) 10 parts by weight and 30 parts by weight of glass powder having the following composition (maximum particle size 44
μm, average 4 μm) was added, mixed well, slip casting and injection molded to obtain a turbine blade.

Composition of glass SiO ₂ 25.4wt% Na ₂ O 16.1wt% Al ₂ O ₃ 8.0wt% K ₂ O 9.2wt% MgO 4.2wt% BaO 0.6wt% CoO 1.3wt% CuO 1.0wt% B ₂ O ₃ 34.2wt% After sufficiently drying, raise the temperature to 650 ° C at 10 ° C / min and hold for 2 hours.
After that, the temperature was raised to 1200 ° C. at 15 ° C./min and calcined at the same temperature for 2 hours. The calcination and the degreasing are performed under N ₂ , and a 30 ml / min N ₂ carrier is flown at a reduced pressure of 0.4 Torr.

After calcination, ultrasonic waves of 20 MHz were irradiated with HF 0.05% + 25% HNO _{3 and} washed for 30 minutes. After washing, it was thoroughly washed with water and then dried. After drying, it was calcined at 500 bar and 1700 ° C. for 2 hours to obtain a sintered body.

The density of the sintered body is about 2.0, and about 40% are pores. When the true density was measured strictly, it was about 2.6 to 2.7, indicating that the pore cell walls were sufficiently grain-grown.

When the fracture surface was observed with an optical microscope SEM or the like, the approximately maximum pores were about 40 μm, and pores of 2-3 μm on average were uniformly dispersed throughout.

Set this in the mold and preheat to 1200 ° C,
The melt of Incone l713C was press-fitted. The molten metal temperature is 1350 ° C, and the applied pressure is 200 Kgf / mm ² .

The three-point bending strength after casting was about 50 to 60 Kgf / mm ² , which was 2 to 6 times that of the conventional one.

Observation of the fracture surface showed good filling without defective filling.

[Experimental Example 2] In Experimental Example 1, continuous pores were three-dimensionally uniformly distributed as shown in FIGS. 3 to 5, but in Experimental Example 2, both the amount of pores and the diameter of pores were gentle. It was decided to have a gradient to.

As the raw materials Si ₃ N ₄ , Al ₂ O ₃ , Y ₂ O ₃ and the like, the same ones as in Experimental Example 1 were used. The glass powder was changed to the following, and the same compounding ratio was adopted.

The main properties of the glass had a specific gravity 4.3 Viscosity _{(800~1200 ℃) 0.4~2.0cp SiO 2 12.0wt} % ZrO 2 15.3wt% B 2 O 3 37.2wt% PbO 10.4wt% Al 2 O 3 5.5wt% BaO 3.2 wt% Na ₂ O 16.4 wt% As in Experimental Example 1, one was slip-casting, the other was injection-molded and dried sufficiently. Drying is 110 ° C. for 12 hours, 210 ° C. for 10 hours, 350 ° C. for 10 hours, and 450 ° C. for 10 hours. The pattern up to the calcination was the same as in Experimental Example 1, and the pattern was washed with the same acid solution, thoroughly washed with water and dried. After drying 17
The sample was treated at 00 ° C., then cut from the center and observed.

This is shown in FIG. 6 (A). The relative density in FIG. 6 (B) is a three-dimensional estimation of the two-dimensionally obtained one. There is a general idea that when the relative density exceeds 80%, fine pores are closed, but in this test
In SEM observation, micropores of 0.1 μm or less were formed and not blocked. It is considered that this is because the excess amount of the auxiliary agent which is not necessary for sintering was discharged in advance during the cleaning with acid. When it exceeds 80%, the maximum pore size is 0.3 to 0.4 μm.
And about 0.1 μm is distributed almost uniformly. Furthermore, at the edge, the relative density reached 97-98%, and the maximum pore size was 0.1 μm.

Regarding the internal defects, the particle size of the glass powder was larger than the particle size of the raw material, so it seems that the fluidity and filling properties were improved, and the shrinkage cavities seen in the boss were not seen. Further, it is considered that this is due to some extent to the elasticity of the glass powder, the slurry due to the influence of the additives, the compounding ratio, etc., and the properties of the kneaded body at the time of molding.

After that, there was a concern that the pores of the molded body were clogged, and after pickling again, it was dried, preheated to 1200 ° C, and SCM420 was pressure-cast at 50 kgf / mm ² at a molten metal temperature of 1520 ° C.

Observation of the fracture surface after casting revealed that the steel had penetrated to a distance of about 51 mm in Fig. 6 and no cracks were seen.

(Effects of the Invention) As described above, according to the present invention, since a rotating body such as a turbine wheel can be formed of a composite material of ceramic and metal having no bonding interface, a temperature difference between a low temperature and a high temperature can be reduced. Even if it is used in a place where severe conditions are repeated, the advantages of ceramics (heat resistance) and the advantages of metal (thermal conductivity) are exhibited, and a long-life rotating body that is not easily damaged can be provided.

In particular, in the turbine wheel, the boss portion of the rotor portion was likely to have a sink mark or the like in the past, but according to the method of the present invention, the boss portion is a part of the ceramic molded body. There is no disadvantage and the yield is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the method of the present invention in the order of steps, and FIG.
FIG. 4 is a sectional view of a ceramic molded body, FIG. 3 is a sectional view of a rotating body, and FIGS. 4 to 6A are sectional views of another embodiment.
FIG. 6B is a graph showing the relationship between the distance from the shaft end and the pore diameter and relative density. In the drawings, 1 is a ceramic molded body, 2 is a shaft portion, 3 is a rotor portion, 3a is a boss portion, 3b is a blade portion, and 7 is a rotating body.

Claims (4)

[Claims] 1. A method of manufacturing a rotating body comprising a shaft portion and a rotor portion, wherein the shaft portion and at least a boss portion of the rotor portion are integrally molded with a ceramic material, and then pores are formed in the ceramic molded body. Then, a method of manufacturing a ceramic rotating body, characterized in that the pores are filled with a molten metal material so as to be solidified. 2. The ceramic rotating body according to claim 1, wherein the pores are formed by eluting a glassy pore-forming powder mixed with a ceramic material with an acid. Production method. 3. The method for producing a ceramic rotary body according to claim 1, wherein the pores in the ceramic molded body are uniformly distributed with substantially the same diameter. 4. The ceramic rotating body according to claim 1, wherein the pores in the ceramic molded body gradually change in pore diameter and porosity from the shaft portion toward the boss portion. Production method.