JPH10226838A - Cast parts for combustor and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively produce thin and long parts for a combustor composed of a Co base heat resistant alloy excellent in creep strength and oxidation resistance with good castability. SOLUTION: This cast parts for a combustor such as a transition piece for thermal power generation or the like is the one having a compsn. contg., by weight, 0.05 to 0.30% C, 15 to 35% Cr, 8 to 25% Ni, 5 to 20% W, and the balance substantial Co, in which the length of a tube part 50c is regulated to at least >=300mm, and the thickness of at least a part of the thin part is regulated to <=10mm and also to <=1/15 to the equivalent inside diameter of the tube part. Then, a mold housing chamber 5 having an opening part 7 on the bottom part 6 and a molten metal introducing port 8 provided projectingly to the opening part are arranged, a runner 2 is connected to the molten metal introducing port 8, a gate part 3 is plurally diverged from the runner, a mold 1 having the cavity of the cast parts for a combustor is housed into the mold housing chamber from the gate part 3, pressure-reduction control is executed, and molten metal 10 in a holding furnace 9 is suctionally cast.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cast parts for combustors for thermal power generation and the like, and in particular, has excellent durability such as creep strength and oxidation resistance, does not require bending and welding, and can be manufactured at low cost. The present invention relates to a cast part for a combustor made of a heat-resistant Co (cobalt) base alloy.

[0002]

2. Description of the Related Art Combustor parts for thermal power generation are 800 to 800 parts.
Since it is used at 1000 ° C. or at a high temperature exceeding 1000 ° C., it is required to have durability such as creep strength and oxidation resistance. For example, as disclosed in Japanese Patent Application Laid-Open No. 7-224337, C: 0. 05-0.45%, Ni:
5 to 15%, Cr: 15 to 30%, W: 3 to 10%, R
e: 1 to 5%, Ti: 0.01 to 1%, Nb: 0.01
-1%, Zr: 0.01-1%, Si: 1% or less, M
A Co-based heat-resistant alloy containing n: 1% or less, Fe: 1.5%, and the balance substantially consisting of Co and unavoidable impurities is used for a gas turbine stationary blade. And C
Conventionally, a combustor part made of an o-base heat-resistant alloy is bent after forging, assembled by welding a flange portion, or as described in JP-A-7-224337, such as lost wax. It is manufactured by a simple precision casting method.

[0003]

A conventional combustor component made of a Co-base heat-resistant alloy is assembled by forging or welding, so that there is no degree of freedom in shape, the assembly cost is high, and the productivity is low. In addition, thermal efficiency is lowered from the viewpoint of heat resistance. Furthermore, when manufactured by the precision casting method, since the casting is performed in a high-temperature mold, the cooling rate after filling the molten metal is low, and the crystal grains become coarse and the toughness is reduced. In addition, in the precision casting method, since an expensive ceramic mold is used, the cost increases. Further, in the precision casting method, it is difficult to integrally manufacture a long combustor part whose wall thickness is smaller than the inner diameter.

The present invention solves the problem of a thin and long combustor component made of the above-mentioned conventional Co-based heat-resistant alloy, and is excellent in creep strength, oxidation resistance, heat efficiency and castability, and can be manufactured at low cost. An object of the present invention is to provide a cast part for a combustor and a method for manufacturing the same.

[0005]

Means for Solving the Problems As a result of intensive studies in view of the above-mentioned object, the present inventors have found that the present inventors have proposed not the precision casting method or the general suction casting method but the Japanese Patent Laid-Open Publication No.
The combination of the vacuum suction casting apparatus disclosed in Japanese Patent Application Publication No. 206815 and the appropriate control of the pressure reduction make it possible to use a casting material such as a Co-based heat-resistant alloy and have a pipe length of at least 3 mm.
00 mm or more and the thickness of at least a part of the thin portion is 10
Even when casting a combustor part that is less than 1 mm and not more than 1/15 of the equivalent inner diameter of the pipe part, there are no casting defects such as non-turning, blowing, foreign matter biting, and cracking. The present inventors have found that it is possible to impart improved creep strength and oxidation resistance and arrived at the present invention.

That is, the cast part for a combustor of the present invention is:
A combustor cast part having a thin-walled portion in a pipe portion, wherein, by weight ratio, C: 0.05 to 0.30%, Cr: 15 to 35
%, Ni: 8 to 25%, W: 5 to 20%, the balance substantially consisting of Co, and the length of the tube portion is at least 3%.
00 mm or more, and the thickness of at least a part of the thin portion is 1
0 mm or less and 1/15 or less with respect to the equivalent inner diameter of the tube. Further, the cast part for a combustor is used for thermal power generation, and is particularly a transition piece.

Next, a method for manufacturing a cast part for a combustor according to the present invention is a method for manufacturing a cast part for a combustor having a thin portion in a pipe portion, comprising: a mold accommodating chamber having an opening at a bottom; And a runner is connected to the melt inlet, a plurality of weirs are branched from the runner, and the length of the pipe portion is at least 300 mm or more from the weir, and at least the thin portion A gas-permeable mold which has a cavity in which a part of the wall thickness is 10 mm or less and which is 1/15 or less with respect to the equivalent inner diameter of the tube portion, and which is accommodated in the mold accommodating chamber; The molten metal inlet is immersed in the molten metal in the holding furnace to control the degree of decompression of the decompression device, and C: 0.05 to 0.30%, Cr: 15 to 3
The cavity is filled with a molten metal containing 5%, Ni: 8 to 25%, W: 5 to 20%, and the balance substantially consisting of Co.

Preferably, the runner is a vertical runner, and the wall thickness of the weir is preferably equal to or less than the wall thickness of the thin part of the cast part for a combustor. It is preferable that the pressure in the mold storage chamber is set to the atmospheric pressure before the opening is immersed in the molten metal, and that the degree of decompression in the mold storage chamber is gradually released after the cavity is filled with the molten metal.

Hereinafter, the reasons for limiting the composition of the Co-based heat-resistant alloy of the present invention will be described. (1) C: 0.05 to 0.30% C forms a carbide in combination with Cr, W, etc. in addition to forming a solid solution in the matrix, strengthens the inside and at the grain boundaries, and has a high-temperature strength. And further improve castability. C
If the content is less than 0.05%, the desired effect cannot be obtained. On the other hand, if the content exceeds 0.30%, the toughness deteriorates. Therefore, C is set to 0.05 to 0.30%.

(2) Cr: 15 to 35% Cr combines with C to form a carbide and is an essential element for imparting high-temperature oxidation resistance. Cr content is 15%
If it is less than 30, the desired high-temperature oxidation resistance cannot be obtained, while if the Cr content exceeds 35%, the high-temperature strength and toughness decrease. Therefore, Cr is set to 15 to 35%.

(3) Ni: 8 to 25% Ni coexists with Cr to improve high-temperature strength. If the Ni content is less than 8%, the desired effects cannot be obtained, while if the Ni content exceeds 25%, the corrosion resistance and oxidation resistance are reduced.
Therefore, Ni is set to 15 to 35%.

(4) W: 5 to 20% W combines with C to form a high-melting carbide, thereby improving high-temperature strength. If the W content is less than 5%, the desired effect cannot be obtained, while if the W content exceeds 20%, an intermetallic compound is formed and the toughness is reduced. Therefore, W is set to 5 to 20%.

Then, using the above-mentioned casting apparatus, C:
0.05 to 0.30%, Cr: 15 to 35%, Ni: 8
-25%, W: 5-20%, the balance being substantially Co
By filling the cavity with the molten metal consisting of, there is no casting defect such as non-turning, blowing, foreign matter biting, and cracking, and a cast part for a combustor can be obtained. Since the air-permeable mold at room temperature is used, the cooling rate of the molten metal after filling into the cavity is high, and the crystal grains are fine, so that durability such as creep strength and oxidation resistance is improved.

[0014]

FIG. 1 is a cross-sectional view of a transition piece, which is a cast part for a combustor, which is attached to an auto-thermal power generator and guides high-pressure gas generated in a combustion chamber to turbine blades. The transition piece 50 has a tube portion 50c having a length of 300 mm or more and a thickness of 3 to 10 mm.
mm, the inner diameter 50A of the left side is 200 to 500 mm, the inner width 50b of the right side is 80 to 160 × 240 to 480 mm, and the right end of the pipe part 50c has a thickness of 5 to 30 mm.
0d. When the transition piece 50 has a thickness of 10 mm on the left side of the tube and an inner diameter of 200 mm, the thickness is 1/20 (= 10 mm / 200 m) with respect to the equivalent inner diameter of the tube.
m), and the right side of the tube is 5 mm thick and 50 mm in inner width.
40 mm ｛(Equivalent circle diameter of tube = [4 (50 mm × 120
mm) / π] 1/2 = 87 mm}, the wall thickness is 17.4 (= 5 mm / 87 mm) with respect to the equivalent inner diameter of the tube portion, and the wall thickness is substantially equal to the equivalent inner diameter of the tube portion. It is 1/15 or less. Thus, the transition piece 50
It is a combustor cast part having a thin part of 10 mm or less and a wall thickness smaller than the equivalent inner diameter of the pipe part. The high-temperature combustion gas of about 1200 ° C. generated in the combustion chamber (not shown) flows from the inner diameter 50a on the left side of the transition piece to the inner width 50b on the right side as indicated by an arrow.

The chemical composition of the transition piece of FIG. 1 is as shown in Table 1. (Table 1) Chemical composition (% by weight ) of the cast cobalt-based heat-resistant alloy C Si Mn Ni Cr W B Fe Co 0.25 0.7 0.5 10.1 29.2 7.4 0.01 0.3 Remaining Excellent in creep strength and oxidation resistance due to the composition shown in Table 1. Transition piece.

Next, a method of manufacturing a transition piece which is a cast part for a combustor shown in FIG. 1 will be described. FIG. 2 is a longitudinal sectional view of a casting device for manufacturing a transition piece having a thin portion in a pipe portion. The casting device has a bottom 6
A mold storage chamber 5 having an opening 7 therein, a melt inlet 8 protruding from the opening 7, and a vertical runner 2 having a diameter of 35 mm accommodated in the mold storage chamber 5 and having a transition piece 50. Are provided on both sides of the cavity, and a plurality of weirs 3 are branched from the runner 2, and a pipe 50 c is formed from the weir 3.
Is at least 300 mm, and the thickness of a part of the thin portion is 1
A gas-permeable mold 1 having a cavity of a transition piece 50 having a diameter of at most 0 mm and at least 1/15 of an equivalent inner diameter of a pipe, and a decompression device 4 for controlling the pressure of a mold storage chamber 5; The inlet 8 is immersed in the molten metal 10 in the holding furnace 9 to control the degree of decompression of the decompression device 4,
C: 0.05 to 0.30%, Cr: 15 to 35%, N
A transition piece 50 containing the molten metal 10 containing i: 8 to 25%, W: 5 to 20%, and the balance substantially consisting of Co.
Is filled in the cavity. Here, weir 3
Is 10m of the thin part of the transition piece 50
m or less.

Before the molten metal inlet 8 is immersed in the molten metal 10, the interior of the mold storage chamber 5 is set to atmospheric pressure, and after filling the molten metal 10 into the cavity of the transition piece 50, the degree of decompression in the mold storage chamber 5 is gradually reduced. Has been released. The decompression device 4
It comprises a vacuum pump 12, a pressure control device 13, and a suction head 14, which is in close contact with the air-permeable mold 1 and performs vacuum suction. The breathable mold 1 is a cold box type and uses silica sand No. 6,
The cavity of the transition piece 50 is formed by the air-permeable mold 1 and the core 11.

Next, the steps of the manufacturing method will be described. The gas-permeable mold 1 is stored in a pouring station (not shown) in the mold storage chamber 5 and is carried in by a transfer device (not shown).
Next, the inside of the mold storage chamber 5 is sealed, and the suction head is brought into close contact with the air-permeable mold 1. Then, the molten metal inlet 8 is immersed in a molten metal 10 made of a Co-based heat-resistant alloy shown in Table 1 and having a temperature of 1540 to 1560 ° C., and the inside of the mold accommodating chamber 8 is depressurized by the decompression device 12, and a predetermined amount of molten metal is transferred. 5
0 cavity. In this embodiment, the ultimate pressure reduction degree is -400 mmHg, the pressure reduction speed is 400 mmHg / sec, and the pressure control device 13 controls the pressure value in the mold storage chamber 5 to increase at 50 mmHg / sec from 20 seconds after the start of pouring. Then, the molten metal from the upper part of the runner 2 flows out and falls into the molten metal holding furnace 9 sequentially. After filling the molten metal, the pressure value in the mold storage chamber 5 is controlled by the pressure control device 13. When the pressure becomes -50 mmHg 27 seconds after the start of pouring, the mold storage chamber 5 is raised to end the immersion, and the molten metal in the runner 2 is entirely discharged into the molten metal holding furnace 9 and dropped.

After the immersion, the suction head 14 is separated from the air-permeable mold 1. After that, it is carried out to the next mold release station (not shown) by a transfer device (not shown). And
Another mold storage chamber 8 in which the air-permeable mold 1 is set is carried into the pouring station. The above steps are repeated to cast the required number of transition pieces 50. 30 transition pieces 50 were continuously cast, and the quality was investigated. As a result, there were no casting defects such as all, no round, no blow, foreign matter biting, and cracking, and a cast part for a combustor made of a sound Co-based heat-resistant alloy could be obtained. Further, since the molten metal in the runner 2 is returned to the molten metal holding furnace 9, the injection yield is good, and since the weir 3 is separated from the transition piece 50, the conventional process for separating the weir is omitted. And could be manufactured at low cost.

[0020]

As described in detail above, the combustor casting part of the present invention has a weight ratio of C: 0.05 to 0.30.
%, Cr: 15 to 35%, Ni: 8 to 25%, W: 5 to 5%
20%, the balance being substantially Co, the length of the tube portion is at least 300 mm, the thickness of at least a portion of the thin portion is 10 mm or less, and 1/15 or less with respect to the equivalent inner diameter of the tube portion It has excellent durability, especially creep strength and oxidation resistance, and does not require bending or welding. Further, according to the method for producing a tube combustor cast part of the present invention, even if the Co-based heat-resistant alloy is a long and difficult-to-cast material having a thin portion, it does not turn, is blown,
A casting component for a combustor made of a Co-based heat-resistant alloy can be obtained without occurrence of casting defects such as foreign matter biting and cracking. Further, the injection yield is good, the step for separating the weir can be omitted, and the production can be performed at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a transition piece, which is a cast part for a combustor, which is attached to a private thermal power generator and guides high-pressure gas generated in a combustion chamber to a turbine blade.

FIG. 2 is a longitudinal sectional view of a casting apparatus for manufacturing a transition piece that is a cast part for a furnace according to the present invention.

[Explanation of symbols]

1: breathable mold, 2: runner, 3: dam, 4: decompression device, 5: mold storage room, 6:
Bottom, 7: opening, 8: melt inlet,
9: molten metal holding furnace, 10: molten metal, 11: core,
12: vacuum pump, 13: pressure controller, 1
4: suction head, 50: transition piece, 5
0a: left inner diameter, 50b: right inner width, 50
c: pipe part, 50d: flange part 50d.

Claims (8)

[Claims] 1. A combustor cast part having a thin wall portion in a pipe portion, wherein C: 0.05 to 0.30% by weight, C:
r: 15 to 35%, Ni: 8 to 25%, W: 5 to 20%
Wherein the balance is substantially made of Co, the length of the tube portion is at least 300 mm, the thickness of at least a part of the thin portion is 10 mm or less, and 1/15 or less with respect to the equivalent inner diameter of the tube portion. A cast part for a combustor, characterized in that: 2. The cast part for a combustor according to claim 1, wherein the cast part for a combustor is for thermal power generation. 3. The cast part for a combustor according to claim 2, wherein the cast part for a combustor is a transition piece. 4. A method for manufacturing a cast part for a combustor having a thin portion in a pipe portion, comprising: a mold storage chamber having an opening in a bottom portion; a molten metal inlet provided to project from the opening; A runner is connected to the runner, and a plurality of weirs are branched from the runner. From the weir, the thickness of the pipe portion is at least 300 mm, the thickness of at least a part of the thin portion is 10 mm or less, and the equivalent inner diameter of the pipe portion. An air-permeable mold having a cavity that is 1/15 or less with respect to the mold housing chamber,
A decompression device for controlling the pressure of the mold storage chamber, wherein the molten metal inlet is immersed in the molten metal in the holding furnace to control the degree of decompression of the decompression device. C: 0.05 to 0.30%, Cr :
A method for producing a cast part for a combustor, characterized in that the cavity is filled with a molten metal containing 15 to 35%, Ni: 8 to 25%, and W: 5 to 20%, and the balance substantially consisting of Co. 5. The method according to claim 4, wherein the runner is a vertical runner. 6. The method for manufacturing a cast part for a combustor according to claim 4, wherein the thickness of the weir portion is equal to or less than the thickness of a thin portion of the cast part for a combustor. 7. The mold receiving chamber is brought to atmospheric pressure before the molten metal inlet is immersed in the molten metal.
3. A method for producing a cast part for a combustor according to item 1. 8. The casting for a combustor according to claim 4, wherein after the cavity is filled with the molten metal, the degree of decompression in the mold chamber is gradually released. The method of manufacturing the part.