JPH09155503A - Mold for precision casting and method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the mold excellent in non-reactivity for efficiently producing a high quality gas turbine moving blade and stationary blade. SOLUTION: In producing a gas turbine moving blade and stationary blade with a Ni base or Co base super heat resistant alloy containing C, Hf, in a mold surface layer (a face layer 1), by using an Al2 O3 powder and SiO2 powder only for a filler material and a slurry of colloidal silica for a binder, a mold excellent in non-reactivity with alloy molten metal is produced, a high quality gas turbine moving blade and stationary blade is efficiently produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precision casting mold and a casting method, and particularly when casting a gas turbine rotor blade or a stationary blade for power generation, particularly casting a Ni-base superalloy containing C and Hf. The present invention relates to a precision casting mold and a casting method, which are made of a low-reactivity ceramic, and are suitable for the production.

[0002]

2. Description of the Related Art Ni-based and Co-based super-heat-resistant alloys have been mainly used as materials for moving blades and stationary blades of gas turbines for power generation. The combustion gas temperature has been increasing year by year in order to improve the thermal efficiency of the gas turbine.

Conventionally, equiaxed crystals have been the mainstream of the structure of gas turbine blades. However, as the combustion gas temperature rises, the heat resistant strength reaches its limit. Therefore, in order to further improve the heat resistance strength, the structure has been columnar crystallized by the unidirectional solidification method or single crystallized, and complicated cooling holes have been provided inside the moving blade to cool the structure from the inside.

On the other hand, in the conventional structure of the gas turbine stationary blade, the equiaxed crystal of Co-based alloy has been the mainstream. However, as the combustion gas temperature rises, the heat resistant strength reaches its limit.
Therefore, Ni-based alloys with excellent high-temperature strength have been applied, and in order to further improve heat resistance strength, the structure is columnar crystallized by the unidirectional solidification method or single crystallized, and complicated cooling is performed inside the vane. Holes are provided for cooling from the inside.

When a gas turbine rotor blade or a stationary blade is manufactured by the unidirectional solidification method, the mold is kept at a high temperature for a long time and is kept in contact with the molten alloy for a long time. Properties such as non-reactivity with are required.

An example of a mold applied to the unidirectional solidification method is disclosed in Japanese Patent Laid-Open No. 224044/1992.
In this mold, the filler and the fine-grained refractory in the slurry are mainly Al ₂ O ₃ fine particles, and the maximum particle size of the filler contained in the face layer is the maximum of the filler contained in the second layer. The particle size is smaller than the particle size, and the maximum particle size of the filler contained in the second and subsequent layers is 10
It is characterized in that the average particle diameter is 20 μm or more when the particle size is μm or more and 200 μm or less.

The casting obtained by the method disclosed in JP-A-4-224044 has a good casting surface. Further, the mold has an average particle diameter corresponding to 50% cumulative weight of the filler contained in the slurry of the second and subsequent layers of 20 μm or more, so that the high temperature strength is improved. In addition, by increasing the particle size of the filler from the face layer on the melt side to the outside, the bending strength changes from compression to tension from the first layer to the outer layer, and the mold strength of each layer is increased. Can be improved.

Further, by limiting the ratio of the average particle diameter of the filler to the average particle diameter of the fine-grained refractory material within a certain range, the density of the mold can be increased, the internal voids can be reduced, and the strength can be improved. it can. The same effect can be obtained by setting the maximum particle diameters of the fillers used in the face layer and the second and subsequent layers to 100 μm or less and 100 μm to 200 μm, respectively.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The high temperature strength of the mold by the method described in Japanese Patent No. 4 is sufficient. However, the mold is intended to cast a single crystal alloy containing no C or Hf,
When a Ni-based super heat-resistant alloy containing C and Hf is cast, the mold face layer reacts with the molten alloy, and many convex defects occur on the surface of the casting.

It is possible to remove this convex defect by hand finishing or machining. However, the processing time and processing cost increase, and the unit price of the casting increases. Further, since the alloy is contaminated by the reaction, there is a problem that the casting has a problem of deteriorating the original properties of the alloy such as the physical strength and the corrosion resistance.

An object of the present invention is to efficiently produce C and Hf in order to efficiently manufacture high quality gas turbine rotor blades and vanes.
(EN) Provided is a mold capable of producing a casting having excellent surface quality and excellent non-reactivity with a Ni-based super heat-resistant alloy containing.

[0012]

In order to achieve the above object, in the precision casting mold of the present invention, the filler of the slurry forming the casting surface side surface portion of the face layer is alumina (A
1 ₂ O ₃ ) powder and silica (SiO ₂ ) powder. Further, in a precision casting mold in which a plurality of layers of a slurry and a refractory are alternately laminated, the slurry of the mold face side face layer of the mold is composed of a filler and a binder, and the filler is alumina (Al ₂ O ₃ ).
It is characterized by having powder and silica (SiO ₂ ) powder.

The binder of the face layer is
It is made of colloidal silica, and the face layer is
Comprised of stucco consisting of the slurry and refractory,
The back layer on the side opposite to the casting surface side of the face layer is provided with a plurality of alternating layers of slurry and stucco.

Further, in the Al ₂ O ₃ powder and the SiO ₂ powder, when the proportion of the SiO ₂ powder is in the range of 10 to 60% by weight, the number of convex defects generated on the casting surface is 0.5 / cm ²
Hereinafter, there is no problem because the reaction layer can be removed with a thickness of 5.0 μm or less. Further, in the Al ₂ O ₃ powder and the SiO ₂ powder, when the ratio of the SiO ₂ powder is in the range of 20 to 60% by weight, the reaction layer having a thickness of 5.0 μm or less that can be removed on the casting surface. Since it only occurs, there is no problem. Further, in the Al ₂ O ₃ powder and the SiO ₂ powder, when the ratio of the SiO ₂ powder is in the range of 10 to 45% by weight, the number of removable protrusions on the casting surface is 0.5 / cm. ^{There is} no problem because it occurs ² or less. Further, in the Al ₂ O ₃ powder and the SiO ₂ powder, if the ratio of the SiO ₂ powder is in the range of 20 to 45% by weight, the casting surface is optimal without defects. The average particle diameters of the Al ₂ O ₃ powder and the SiO ₂ powder are preferably 10.0 μm and 12.0 μm, respectively.

Further, passing the mass percentage of the Al ₂ O ₃ powder and SiO ₂ powder is, in the case of Al ₂ O ₃ powder, it is 1.0μm or less 12.
9%, 1.5 μm or less is 15.9%, 2.0 μm or less is 2
1.3%, 3.0 μm or less is 26.6%, 4.0 μm or less is 31.8%, 6.0 μm or less is 38.3%, 8.0 μm or less is 45.8%, 12.0 μm or less 54.6%, 16.0μ
63.0% for m or less, 72.6% for 24.0 μm or less, 3
82.8% below 2.0 μm, 94.6 below 48.0 μm
%, 64.0 μm or less is 97.3%, 96.0 μm or less is 100%, and SiO ₂ powder is 1.0 μm or less is 0.6%.
%, 1.5% or less is 1.8%, 2.0 μm or less is 6.8
%, 3.0 μm or less is 14.1%, 4.0 μm or less is 19.
6%, 29.0% for 6.0 μm or less, 3 for 8.0 μm or less
7.3%, 18.7 μm or less is 48.7%, 16.0 μm or less is 57.5%, 24.0 μm or less is 67.6%, 32.0
77.0% below μm, 88.5% below 48.0 μm,
62.9 μm or less is 92.9%, 96.0 μm or less is 98.
2%, 128.0 μm or less is 99.0%, 192.0 μm
The following is preferably 100%.

Further, it is preferable to unidirectionally solidify a Ni-base superalloy containing one or two of C and Hf by using the precision casting mold according to the present invention. Further, it is preferable that the precision casting mold according to the present invention is used to manufacture a columnar crystal blade or a single crystal blade of a power generation gas turbine manufactured by a unidirectional solidification method. Further, the precision casting mold according to the present invention may be used to manufacture a columnar crystal stationary blade or a single crystal stationary blade of a power generation gas turbine manufactured by a unidirectional solidification method.

By adopting the above configuration,
It has the following effects. For example, using a mold applying the slurry for the face layer (mold surface layer) by the above method,
The gas turbine moving blade and stationary blade obtained by unidirectionally solidifying a Ni-base superalloy containing C and Hf can reduce the reaction between C and Hf and the mold. Therefore, it is possible to significantly reduce the number of convex defects and the thickness of the reaction layer due to the surface defects of the casting due to the reaction. In addition, since the contamination of the alloy by the mold due to the reaction can be significantly reduced, it is possible to manufacture high-quality gas turbine moving blades and stationary blades that do not impair the original properties of the alloy such as physical strength and corrosion resistance. . This convex defect can be removed by machining or hand finishing after casting, but the quality of the surface from which the defect is removed is poor.
Since the reaction layer has a concave defect, it is impossible to repair it after casting. As described above, at the contact portion between the mold face layer and the molten alloy, a convex defect and a reaction layer are generated due to a unique reaction between the components of the mold face layer and the molten alloy components containing C and Hf.

According to the present invention, when Ni-based and Co-based super heat-resistant alloys are cast by the unidirectional solidification method, the filler of the slurry used for the mold face layer is Al ₂ O ₃ powder alone or SiO ₂ powder alone slurry. In order to solve the problem caused in the case of doing, it is a mixture of Al ₂ O ₃ powder and SiO ₂ powder only.

By applying only alumina Al ₂ O ₃ powder and SiO ₂ powder to the mold face layer, it is possible to suppress the generation of convex defects and reaction layers. At this time, Al ₂
It is desirable that the ratio of the O ₃ powder and the SiO ₂ powder be in an appropriate range. Further, since it is impossible to repair the reaction layer, the above ratio is particularly preferably within a range in which the reaction layer is hard to generate. Further, a range in which both convex defects and the reaction layer are unlikely to occur is more preferable.

Further, if the number of raised defects is generally 0.5 or less / cm ² on the surface of the casting, it is considered that they can be easily removed and there is no problem as casting. That is, Al ₂ O ₃ powder and S that make the number of convex defects to be 0.5 / cm ² or less
It is preferable to set the ratio to the iO ₂ powder. Further, if the thickness of the reaction layer is generally 5 μm or less on the surface of the casting, it is considered that the reaction layer can be removed and there is no problem as casting. In other words, the thickness of the generated reaction layer is 5 μm or less Al
It is preferable to use a ratio of ₂ O ₃ powder and SiO ₂ powder.

The average particle diameters of the Al ₂ O ₃ powder and the SiO ₂ powder are 10.0 μm and 12.0 μm, respectively. Furthermore, the passing mass percentages of the Al ₂ O ₃ powder and the SiO ₂ powder are as follows. By doing so, it is possible to further suppress the generation of convex defects and reaction layers. That is, A
In the case of l ₂ O ₃ powder, 1.0 μm or less is 12.9%, 1.5 μm
m is 15.9% or less, 2.0 μm or less is 21.3%, 3.0
26.6% below μm, 31.8% below 4.0 μm, 6.
38.3% below 0 μm, 45.8% below 8.0 μm,
54.6% below 12.0 μm and 63 below 16.0 μm.
0%, 24.0 μm or less 72.6%, 32.0 μm or less 82.8%, 48.0 μm or less 94.6%, 64.0 μ
m or less is 97.3%, 96.0 μm or less is 100%, Si
In the case of O ₂ powder, 1.0 μm or less is 0.6%, 1.5 μm or less is 1.8%, 2.0 μm or less is 6.8%, 3.0 μm or less is 14.1%, 4.0 μm or less Is 19.6%, 6.0 μm or less is 29.0%, 8.0 μm or less is 37.3%, 12.0 μm
Below is 48.7%, below 16.0 μm is 57.5%, 24.
67.6% below 0 μm, 77.0 below 32.0 μm
%, 48.0 μm or less is 88.5%, 64.0 μm or less is 92.9%, 96.0 μm or less is 98.2%, 128.0 μ
It is preferable that m or less is 99.0% and 192.0 μm or less is 100%.

Further, since the precision casting mold according to the present invention has a very low reaction with the molten alloy, a unidirectional solidification method with a long solidification time is used to produce a Ni-base super heat-resistant alloy containing one or two of C and Hf. Casting is preferred. Moreover, Cr is 5 to 20 wt.
%, C is 0.05 to 0.2 wt%, Co is 8 to 11 wt%.
%, Cu 0.1 wt% or less, Mo 0.3-5 wt%,
W is 2.5 to 10 wt%, Fe is 0.5 wt% Max, N
b is 1 wt% or less, Ti is 0.7 to 6 wt%, and Al is 2.
8-6 wt%, Hf 0.5-1.7 wt%, Ta 5w
t% or less, B is 0.01 to 0.02 wt%, Zr is 0.0
A Ni-based super heat resistant alloy containing 7 wt% or less is preferable. Further, Cr is 18 to 25 wt% and Co is 18 to 25 wt%.
%, Al 0.5 to 2 wt%, Hf 0.5 wt% or less,
When Si is 0.3 wt% or less, it is preferable to apply it to a vane.

In particular, it is preferable to cast a columnar crystal blade or a single crystal blade of a gas turbine for power generation, in which it is desired to prevent the surface defects of the casting. Furthermore, when the columnar crystal vanes or the single crystal vanes of the gas turbine for power generation are cast, the finish of the casting surface after casting can be unprocessed or significantly reduced.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 shows a sectional configuration of a precision casting mold according to the present invention. The face layer 1 is made of Al ₂ O ₃ powder and SiO.
Slurry using mixed powder consisting of ₂ powders and Al ₂ O ₃
It consists of stucco. The back layer 2 is composed of Al ₂ O ₃ slurry and Al ₂ O ₃ stucco.

FIG. 2 is a diagram showing the particle size distribution of the Al ₂ O ₃ powder and the SiO ₂ powder used in the present invention. The Al ₂ O ₃ powder and the SiO ₂ powder having the particle size distribution shown in FIG.
A slurry was prepared by arranging the mixture in the mixing ratio as shown in. The binder was colloidal silica having a SiO ₂ content of 30% by weight. Further, the slurry contains nonionic phosphoric acid ester as a surfactant and n-octyl alcohol as an antifoaming agent at 0.3% and 0.3% based on the volume of the binder, respectively.
1% was blended.

[0026]

[Table 1]

Next, the wax model in the shape of a gas turbine blade shown in FIG. 3 was dipped in a slurry and sprinkled with stucco to form a face layer. After drying for about 2 hours and immersing in a slurry, stucco was sprinkled to form a second layer. About 2
After a lapse of time, the same process was repeated 10 times to make the thickness of the mold cross section about 10 mm. After the second layer, the slurries shown in Table 2 below were used, and as the stucco, Al ₂ O ₃ grains having the grain sizes shown in Table 3 were used.

[0028]

[Table 2]

[0029]

[Table 3]

Next, the wax of the mold was removed in a heated steam of about 150 ° C., and then baked at 900 ° C. for 2 hours in the atmosphere to prepare a casting mold. Casting was performed by a mold drawing type unidirectional solidification method to obtain a unidirectionally solidified moving blade. The casting conditions are shown in Table 4 below.

[0031]

[Table 4]

First, the mold was set on a water-cooled chill plate, heated to 1530 ° C. in a heating furnace, and the molten metal was cast from above. The casting temperature was 1550 ° C. After the casting, the mold was pulled out at a speed of 35 cm / h and solidified in one direction. Table 5 shows the composition of the alloy used for casting. Three kinds of alloys were used.

[0033]

[Table 5]

After the drawing, the mold was removed, and the surface defects and the thickness of the reaction layer were examined. FIG. 4 shows the number of convex defects, which are surface defects, and the reaction layer thickness. Mixing ratio is from E to G
In the slurry No. 1, a directionally solidified casting having a good casting surface in which no convex defects and a reaction layer were formed was obtained. The casting alloys used are the three types shown in Table 5, and alloy A,
B is a columnar crystal rotor blade by unidirectional solidification, and alloy C is a single crystal rotor blade provided with a starter and a selector in the mold, but there is no clear difference in the number of convex defects and the reaction layer thickness. I couldn't see it.

As described above, in this embodiment, it is possible to provide a mold which is excellent in non-reactivity with the Ni-base superalloy containing C and Hf and which can produce a casting having excellent surface quality. Therefore, defects on the casting surface and contamination of the alloy caused by the reaction between the mold and the molten metal during casting can be significantly reduced, and a high-quality gas turbine rotor blade can be efficiently manufactured. In addition, defects on the surface of the casting are reduced, and the hand-finishing process and machining process after casting can be omitted or shortened.

<Second Embodiment> Similar to the first embodiment,
A casting mold was prepared using the gas turbine stationary blade model shown in FIG. 5, and columnar crystal stationary blades and single crystal stationary blades were cast by directional solidification. The alloys used were B and C in Table 5 above. The number of raised defects and the reaction layer thickness of the cast product were the same as the results shown in FIG.

[0037]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a mold which is excellent in non-reactivity with an alloy and which can produce a casting having excellent surface quality. Therefore, defects on the surface of the casting and contamination of the alloy caused by the reaction between the casting mold and the molten metal during casting can be significantly reduced, and high-quality gas turbine moving blades and stationary blades can be efficiently manufactured. In addition, defects on the surface of the casting are reduced, and the hand finishing process and the machining process after casting can be omitted or shortened.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a precision casting mold according to the present invention.

FIG. 2 is a particle size distribution diagram of Al ₂ O ₃ powder and SiO ₂ powder used in the present invention.

FIG. 3 is a perspective view showing the shape of a gas turbine rotor blade.

FIG. 4 is a diagram showing the influence of a filler material mixing ratio on the number of raised defects and the reaction layer thickness.

FIG. 5 is a view showing the shape of a gas turbine stationary blade.

[Explanation of symbols]

 1 Face layer 2 Back layer 3 Wax model for moving blade 4 Wax model for stationary blade

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location F01D 5/12 F01D 5/28 5/28 C04B 35/00 D (72) Inventor Hiroshi Fukui Ibaraki Prefecture Hitachi City Omika-cho 7-1-1, Hitachi Ltd. Hitachi Research Laboratory

Claims (15)

[Claims] 1. A precision casting mold characterized in that the filler of the slurry forming the casting surface side surface portion of the face layer comprises alumina (Al ₂ O ₃ ) powder and silica (SiO ₂ ) powder. 2. A precision casting mold in which a plurality of layers of a slurry and a refractory material are alternately laminated, wherein the slurry of the face layer on the casting surface side of the mold comprises a filler and a binder, and the filler is alumina (Al ₂ A precision casting mold comprising O ₃ ) powder and silica (SiO ₂ ) powder. 3. The precision casting mold according to claim 1, wherein the binder of the face layer is made of colloidal silica. 4. The precision casting mold according to claim 1, wherein the face layer is made of stucco composed of the slurry and a refractory material. 5. The back layer on the side opposite to the casting surface side of the face layer is provided with a plurality of layers of slurry and stucco alternately stacked.
The casting mold for precision casting according to any one of 1. 6. The SiO ₂ powder content of the face layer is 10 to 60% by weight.
The casting mold for precision casting according to any one of 1. 7. The SiO ₂ powder content of the face layer is 20 to 60% by weight.
The casting mold for precision casting according to any one of 1. 8. The SiO ₂ powder content in the face layer is 20 to 45% by weight.
The casting mold for precision casting according to any one of 1. 9. The precision casting according to claim 1, wherein the content of the SiO ₂ powder in the face layer is 20 to 45% by weight and the gas turbine blade is cast. Mold. 10. The face layer according to claim 1, wherein an Al ₂ O ₃ powder has an average particle size of 10.0 μm and a SiO ₂ powder has an average particle size of 12.0 μm. Precision casting mold. 11. A mass percentage of Al ₂ O ₃ powder passing through the face layer of 1.0 μm or less is 12.9%, 1.5 μm or less is 15.9%, 2.0 μm or less is 21.3%, 3.0 μm
Below is 26.6%, below 4.0μm is 31.8%, 6.0μ
m or less is 38.3%, 8.0 μm or less is 45.8%, 12.
54.6% below 0 μm and 63.0 below 16.0 μm
%, 24.0 μm or less is 72.6%, 32.0 μm or less is 82.8%, 48.0 μm or less is 94.6%, 64.0 μm
The following is 97.3% and 96.0 μm or less is 100%, and the passing mass percentage of the SiO ₂ powder is 1.0 μm or less is 0.6% and 1.5 μm or less is 1.8%, 2. 0 μm or less is 6.8%, 3.0 μm or less is 14.1%, 4.0 μm or less is 19.6%, 6.0 μm or less is 29.0%, 8.0 μm or less is 37.3%, 12. 08.7m or less is 48.7%, 16.0μ
57.5% for m or less, 67.6% for 24.0 μm or less, 3
77.0% below 2.0 μm, 88.5 below 48.0 μm
%, 64.0 μm or less is 92.9%, 96.0 μm or less is 98.2%, 128.0 μm or less is 99.0%, 192.0
The mold for precision casting according to any one of claims 1 to 10, wherein the thickness of 100 μm or less is 100%. 12. The material of the slurry or stucco applied to the back layer opposite to the casting surface side of the face layer is alumina (Al ₂ O ₃ ), silica (SiO ₂ ),
The precision casting mold according to claim 1, which is made of mullite (3Al ₂ O ₃ .2SiO ₂ ), zircon (ZrSiO ₄ ), or a composite of two or more kinds. 13. A unidirectional solidification casting, which is cast using the precision casting mold according to any one of claims 1 to 12, is a columnar crystal blade or a single crystal blade of a gas turbine for power generation. Casting method for solidified castings. 14. A unidirectional solidification casting, which is cast using the precision casting mold according to any one of claims 1 to 12, is a columnar crystal vane or a single crystal vane of a gas turbine for power generation. Casting method for solidified castings. 15. The casting method according to claim 13, wherein the unidirectionally solidified casting is a Ni-base superalloy containing at least one of C and Hf.