JPH07286730A - Flame stabilizer for gas turbine burner - Google Patents

Abstract

PURPOSE:To obtain an Ni-base alloy flame stabilizer which can be welded and has excellent heat resistant fatigue characteristics by forming the stabilizer of Ni-base superalloy containing specific ratios of C, Co, Cr, Al, Ti, Nb, W and Ni, and fixing a ring made of the same material as that of a swirler to the side connected with the swirler at a hot isotropic pressure. CONSTITUTION:An intermediate ring 11 is fixed to an Ni-base precision cast ring 10 to form a flame stabilizer. The ring 11 is fixed to the ring 10 by diffusion bonding with hot isotropic pressure treatment. In this case, the stabilizer is formed of Ni-base superalloy containing by weight% 0.05-0.20 of C, 15-25 of Co, 15-25 of Cr, 1-3 of Al, 1-3 of Ti, 1-3 of Nb, 5-10 of W and 55 or more of Ni in such a manner that (Al+Ti) amount and W amount are contained within lines for sequentially connecting points of 2.5% of (Al+Ti) and 10% of W, 3% of (Al+Ti) and 10% of W, 5% of (Al+Ti) and 7.5% of W, 5% of (Al+Ti) and 7.5% of W in a characteristic diagram.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for a flame stabilizer of a combustion device for a low NOx gas turbine.

[0002]

2. Description of the Related Art In recent years, a combustion apparatus for a gas turbine (see FIG. 2) has a two-stage combustion structure in order to reduce NOx.
Therefore, the premixed combustion method in which fuel and air are mixed and injected from the same nozzle is being used. Since the flame stabilizer has a structure that is overheated by the flame, it is necessary to apply a material having excellent heat resistance. For example, 19% Fe-by weight
Heat resistant steel such as 22% Cr-9Mo-residual Ni was considered as a candidate material for the flame stabilizer. However, 19% Fe-22%
Cr-9Mo- remaining Ni steel flame stabilizer flame test (fuel composition simulating the actual _{(wt%), CH 4:} 89~91, C 2 H
_{6: 5.5~7.5, C 3 H 8} : 2~2.5) results, will crack occurs in the operation of a few hours, it has been found that application to actual equipment is difficult. Therefore, it became necessary to develop alternative materials for flame stabilizers. Especially, since the damaged part is only the flame stabilizer and the swirler is sound, a structure capable of exchanging only the flame stabilizer has been required. In other words, it has been required to develop a flame stabilizer that can be attached and welded to a swirler and has excellent thermal fatigue resistance.

On the other hand, according to the knowledge obtained so far, γ'phase precipitation strengthening containing Al + Ti: 7 to 10 (for example, Al + Ti: 7 to 10) is used rather than Ni-based heat-resistant steel because it is used for a gas turbine rotor blade, etc. The Ni ₃ (Al, Ti)) Ni-based superalloy is promising as a candidate material for a flame stabilizer because it is excellent in high temperature strength and thermal shock resistance. However, the Ni-base superalloy containing Al + Ti: 7 to 10 is a precision cast alloy, and weldability is not considered at all. Therefore, in the case of fusion welding, there is a problem that many microcracks are generated in the heat affected zone.

Examples of γ'phase precipitation strengthening alloys having improved weldability include US Pat. No. 60-100641 and US Pat. No. 104810467, which are modifications of US Pat. No. 4039330.

[0005]

The above-mentioned conventional techniques improve weldability at the sacrifice of high temperature strength, and high temperature strength, particularly long time strength is taken into consideration from the viewpoint of increasing service temperature and extending life. Not at all.

It is an object of the present invention to provide a flame stabilizer provided with a γ'phase precipitation strengthening alloy having a good balance between weldability and high temperature strength.

[0007]

According to the present invention, in order to improve the weldability, the basic strengthening factor of the Ni-base superalloy is γ'by adjusting the addition amounts of Al, Ti, etc. to be low.
The precipitation amount of the phase is suppressed to a low level to improve the weldability, and the addition amount of W is adjusted in order to improve the high temperature strength, especially the long-term strength, to prevent the precipitation of the harmful phase which adversely affects the strength. Further, in order to enable fusion welding of the precision cast flame stabilizer to the swirler, an intermediate ring of the same quality as the swirler is fixed to the flame stabilizer.

[0008]

The function of the composition of the elements forming the flame stabilizer will be described below.

Al and Ti contribute to the high temperature strength by precipitating the γ'phase, which is a basic strengthening factor of Ni-base superalloys, that is, Ni ₃ (Al, Ti), but if added in excess, weldability is improved. Lower. As the addition amount, Al: 1 to 3%, T
i: The range of 1.5 to 3% is appropriate. Especially Al + T
i: The range of 3 to 5% is preferable.

W is solid-dissolved in the matrix to strengthen it, and is particularly effective for improving long-term strength. However, if added excessively, it promotes the precipitation of harmful phases such as the Laves phase and rather reduces the strength. The appropriate amount of W added is in the range of more than 5% and 10% or less, and W: 6 to 7% is particularly preferable.

C forms a carbide with Cr, Ti, W, etc. in the matrix and grain boundaries to improve the high temperature strength, but when added in excess, it promotes coarsening of the carbide and lowers the strength and ductility at a high temperature for a long time.

Si and Mn are conventionally added to obtain deoxidation, but since the flame stabilizer is manufactured by vacuum casting, addition of these elements is essentially unnecessary, but in order to improve strength and the like. Can be added from the viewpoint. But,
Excessive addition lowers the ductility during high temperature use, so it is preferable to keep both elements to 0.5% or less.

Cr is 2 in order to obtain oxidation resistance and corrosion resistance.
The range of 2 to 25% is appropriate, and Fe is contained because a ferroalloy is used when alloy elements such as Cr, W, Ti, and B are added during melting of a Ni-based alloy. When the amount is excessive, precipitation of σ phase and the like and coarsening of carbides are caused, and the high temperature strength is lowered.

B and Zr strengthen the grain boundaries and improve the high temperature strength. However, if added excessively, not only the ductility and the long-term strength are lowered but also the weldability is lowered, so the upper limit is made 0.015%. did.

The structure of the developed material required as a flame stabilizer and the superiority of the alloy of the present invention will be described below with reference to examples, in comparison with conventional materials.

[0016]

EXAMPLE FIG. 3 shows a cross section around a flame holder of a combustion apparatus used in a gas turbine. The combustion device is the main combustion chamber R
1, a sub-combustion chamber R2, combustion nozzles 3a, 3b, 3c, and a premixing chamber 4. A gas turbine blade is arranged downstream of the combustion chamber R1. That is, as shown in FIG. 4, a swirler 5 for promoting mixing of air and fuel is provided inside the premixer 4,
Further, a flame stabilizer (vortex generator) 6 is provided on the downstream side of the premixer.
Is provided.

The air-fuel mixture flows from the upstream side toward the flame stabilizer 6 as shown by the arrow AF, and becomes a vortex flow from the sudden expansion portion 6a of the flame stabilizer and flows downstream. That is, this sudden expansion portion acts as flame holding at the eddy flow start point. A cooling groove is provided in the spring 9 outside the flame stabilizer, and air CA flows through the groove to cool the flame stabilizer and supply air to the combustion chamber.

The flame stabilizer is thus provided downstream of the swirler, but since the flame moves to the vortex flow 8 and the metal temperature of the flame stabilizer rises, the material is excellent in heat resistance, and by any chance Even if the vessel is damaged, it is required to have a structure that can be easily replaced.

First, as a candidate material for flame stabilizers, from the viewpoint of good weldability and heat resistance, 19% Fe-22% by weight.
There is a Cr-9Mo-Ni based heat resistant steel. Since the flame stabilizer made of 19% Fe-22% Cr-9Mo-Ni-based heat-resistant steel machined after forging has good weldability, TIG or EBW
It could be easily attached to the swirler by any of the welding methods. However, the combustion test (fuel composition (wt
_{%), CH 4: 89~91,} C 2 H 6: 5.5~7.5, C 3
As a result of H ₈ : 2 to 2.5), cracks are generated after a few hours of operation, so there was a problem in thermal fatigue resistance when applied to an actual machine. Therefore, in order to search for a γ'phase precipitation strengthened Ni-based alloy having excellent high-temperature strength, Ni-based alloys having different amounts of Al + Ti and W were cast in a high-frequency melting furnace. Then, after heating at 1170 ° C. for 4 hours, cooling with water, and aging treatment at heating at 850 ° C. for 5 hours to prepare test pieces for welding experiments and creep experiments, respectively.

FIG. 5 shows a welding current of 80 A, without preheating.
Al + T when 1-pass TIG welding with a welding time of 50 seconds
The relationship between the i amount and the weld crack length is shown. Al + Ti content is 5%
If it exceeds the limit, it will crack easily.
It has been found that it is preferable to control the content to be not more than%.

FIG. 6 is a characteristic diagram showing the relationship between the amount of Al + Ti and the amount of W with respect to the creep rupture time at 900 ° C. and 12 kgf / mm ² . Al + Ti is 2.5% or more, W
When the ratio is 5% or more, the breaking time increases as shown in the figure,
It can be seen that the creep characteristics are improved. However, as shown in FIG. 5, considering the weld crackability, Al + Ti is 5
% Or less is preferable. Although the high temperature strength is increased by adding W, the weldability does not decrease. From these, it was found that by adjusting Al + Ti and the amount of W, a Ni-based superalloy that can be welded and has excellent creep characteristics can be obtained. Details are disclosed in Japanese Patent Application No. 3-277452.

Therefore, from FIG. 6, Al + Ti, which is considered to be most preferable in the range of Al + Ti, W: 3 to 5%,
W: A flame stabilizer having a composition aimed at a range of 6 to 8.5% was precision cast by the lost wax method and a combustion test was conducted to confirm the performance. The other components were in the following ranges.
That is, in% by weight, C; 0.09 to 0.14, Si; <
0.3, Cr; 22-24, B; 0.005-0.01
3, Fe <0.5, Nb; 0.8 to 1.0, Co; 20 to
22, Cu <0.1, Ta; 1.1 to 1.3, and the rest is Ni.

However, the precision cast flame stabilizer has a problem that, when the TIG or EBW method is directly melt-welded to the swirler, some microcracks are generated in the heat-affected zone of the welding due to the large constraint. As a countermeasure against this, a method has been found in which a ring of the same quality as the swirler (hereinafter, referred to as an intermediate ring) is attached in advance to the flame stabilizer on the attachment side of the swirler.

FIG. 1 schematically shows the structure of the flame stabilizer. A Ni-based precision casting ring (outer diameter 350 mm, inner diameter 310 mm, maximum wall thickness 6 mm) was produced by the lost wax method as in the above. An intermediate ring (TIG welding after hot roll bending) was fixed to this Ni-based precision casting ring to form a flame stabilizer. The method of fixing the intermediate ring to the Ni-based precision casting ring is performed by hot isostatic pressing (HI) from the viewpoints of securing joint strength and mass productivity.
The diffusion bonding method by P) treatment is the best. FIG. 7 shows the manufacturing process of the flame stabilizer. As a pretreatment for joining the Ni-based precision casting ring and the intermediate ring by HIP treatment, align both rings to be HIP joined as shown in the figure,
The front and back are EB welded to form a void. This void is joined in the HIP process (H by the partial vacuum method).
It is also called the IP joining method). At the same time, there is also an advantage that casting defects (drawing cavities, voids, etc.) inherent in the precision casting ring and the like are eliminated. Since the voids are formed during EB welding, the pressure difference from the HIP processing atmosphere pressure becomes large, the creeping deformation of the void surface is likely to occur, and the bondability can be improved. The size of the voids to be formed has room for further study in relation to the HIP treatment conditions. The size of the air gap this time is EB welding under a low heat input condition (eg 1.2 kJ /) so that micro cracks do not occur in the heat affected zone of the Ni-based precision casting ring.
cm), but as a result, the ring thickness (7.5 mm) was 4
It was 0 to 55%. HIP processing condition is temperature: 120
The temperature was 0 ° C., the holding time was 3 hours, and the pressure was 1200 kgf / cm ² .

Next, the HIP-treated flame stabilizer is subjected to solution treatment and aging treatment (1170 ° C. × 4 h, 850 ° C. × 8 h) and machined to a predetermined size to complete the flame stabilizer. Finally, it is necessary to attach this flame stabilizer to the swirler, but fusion-free welding such as the TIG or EB welding method has made it possible to join without defects.

The γ'phase precipitation-strengthened (Ni ₃ (Al, Ti)) Ni-base superalloy flame stabilizer with the intermediate ring thus produced showed the occurrence of thermal fatigue cracks in the above-mentioned combustion test. There wasn't. As a result, N with an intermediate ring
The prospect that the flame stabilizer made of i-based superalloy can be applied to the actual machine was obtained.

[0027]

EFFECTS OF THE INVENTION According to the flame stabilizer of Ni-based alloy and the method of manufacturing the same of the present invention, the swirler can be melt-welded without causing weld cracking, and the performance of the Ni-based alloy is exhibited.

[Brief description of drawings]

FIG. 1 is a sectional view of a flame stabilizer provided with an intermediate ring.

FIG. 2 is a sectional view of a gas turbine.

FIG. 3 is a sectional view of a combustor.

FIG. 4 is a cross-sectional view of a combustor swirler and a flame stabilizer.

FIG. 5 is a characteristic diagram showing the relationship between the amount of Al + Ti and welding cracks.

FIG. 6 Relationship between W content and Al + Ti content and 12 kg at 900 ° C.
A diagram showing the creep rupture time at f / mm ² .

FIG. 7 is an explanatory diagram of a manufacturing process of a flame stabilizer provided with an intermediate ring.

[Explanation of symbols]

 10 ... Ni-based precision casting ring, 11 ... Intermediate ring.

Front page continuation (72) Inventor Nobuyuki Iizuka 3-1-1 Sachimachi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Shinichi Nakahara 3-1-1, Sachimachi, Hitachi, Ibaraki No. 1 in Hitachi Factory, Hitachi, Ltd. (72) Takamitsu Nakazaki 3-1-1, Sachimachi, Hitachi, Hitachi, Ibaraki Prefecture (72) In Hitachi Factory, Hitachi, Ltd. (72) Norio Yokoba, Saiwaicho, Hitachi City 3-1, 1-1 Hitachi Ltd. Hitachi factory

Claims (1)

[Claims] 1. A gas turbine combustor comprising a swirler and a flame stabilizer for forming a premixed flame, wherein C is% by weight;
0.05 to 0.20, Co; 15 to 25, Cr; 15 to 2
5, Al; 1-3, Ti; 1-3, Nb; 1-3, W;
5 to 10 and 55% or more of Ni, (Al + T
i) amount and W amount are A (Al + Ti:
2.5%, W: 10%), B (Al + Ti: 3%, W: 1
0%), C (Al + Ti: 5%, W: 7.5%), D (A
l; ti: 5%, W: 5%), E (Al + Ti: 3.5)
%, W5%) and F (Al + Ti: 2.5%, W: 7.5
%) Is a flame stabilizer made of a Ni-based superalloy within a line connecting the points sequentially, wherein a ring of the same quality as the swirler is fixed to the side connected to the swirler by hot isotropic pressure. A flame stabilizer for a gas turbine combustor.