JP5843718B2 - Ni-base welding material and dissimilar material welding turbine rotor - Google Patents

Description

  Embodiments of the present invention relate to a Ni-base weld material and a dissimilar material welded turbine rotor.

In recent years, high efficiency of thermal power plants has been promoted from the viewpoint of reducing carbon dioxide emissions into the atmosphere. Therefore, high efficiency of the steam turbine and gas turbine provided in the thermal power plant is required. High efficiency is also required for a CO ₂ turbine that can be installed in a thermal power plant. Here, the CO ₂ turbine drives the turbine using CO ₂ generated by combustion of natural gas and oxygen as a working fluid. In the CO ₂ turbine, a system in which most of the generated CO ₂ is circulated to the combustor is adopted, and CO ₂ emission is reduced. Therefore, the CO ₂ turbine is attracting attention from the viewpoint of protecting the global environment.

In order to increase the efficiency of each turbine described above, it is effective to increase the inlet temperature of the working fluid introduced into the turbine. For example, a steam turbine is expected to be operated at a steam temperature of 700 ° C. or higher in the future. Also in the gas turbine and the CO ₂ turbine, the inlet temperature of the introduced working fluid tends to increase.

  Therefore, it is desirable that the components constituting the high-temperature part of each turbine be made of a Ni-based heat-resistant alloy that is used for power generation gas turbines and aircraft engine components and has a proven track record for use in high-temperature fields.

The Ni-based alloy has excellent creep strength and tensile strength at high temperatures due to the γ ′ (Ni ₃ (Al, Ti)) phase that is finely dispersed and precipitated in the Ni matrix. However, with the current manufacturing technology, for example, it is difficult to produce a large component such as a turbine rotor from a Ni-based alloy. Furthermore, Ni-based alloys are more expensive than, for example, the materials that make up conventional turbine rotors. For this reason, it is difficult to manufacture the entire turbine rotor from a Ni-based alloy from the technical and manufacturing cost viewpoints.

  In view of this, a dissimilar welded turbine rotor in which a relatively high temperature portion of the turbine rotor is made of a Ni-based alloy and the other portions are made of a conventional Fe-base heat-resistant steel has been studied.

JP 2010-23497 A

  The inventors welded a turbine rotor constituent part made of a Ni-base alloy and a turbine rotor constituent part made of a Fe-base heat-resistant steel using a Ni-base welding material, and applied an aging treatment. It has been confirmed that carbon existing at the boundary with the base welding material diffuses significantly from the Fe-base heat-resistant steel side to the Ni-base welding material side.

  Due to this carbon diffusion, a softened region is formed in the Fe-base heat-resisting steel near the boundary depleted of carbon, a hardened region is formed in the Ni-based welding material near the boundary enriched in carbon, and the creep characteristics deteriorate. Furthermore, depending on the combination of the Fe-base heat-resistant steel and the Ni-base weld material, a third phase that causes embrittlement is formed at the boundary between the Fe-base heat-resistant steel and the Ni-base weld material, which deteriorates the creep characteristics.

  A problem to be solved by the present invention is a Ni-based welding material capable of welding and joining different materials composed of a Fe-based heat-resistant steel and a Ni-based alloy or a Ni-Fe-based alloy so as to have excellent creep strength, And it aims at providing the dissimilar material welding turbine rotor weld-joined by this Ni base welding material.

The Ni-based welding material of the embodiment is used when welding and joining a first constituent member made of Fe-base heat-resistant steel and a second constituent member made of a Ni-base alloy or a Ni—Fe-based alloy. And the difference of the content rate of Cr component in the said Ni base welding material, and said 1st structural member and said 2nd structural member is 14 mass% or less, respectively, and said Ni base welding material and said 1st components and difference der 0.3 mass% or less each of the content of the C component in the second component of is, the Ni-based welding material, in mass%, Cr: 8~25, Co: 1 -12, Mo: 1 to 12, Al: 0.01 to 5, Ti: 0.01 to 3, C: 0.01 to 0.4, B: 0.001 to 0.01, the balance being It consists of Ni and inevitable impurities .

It is the figure which showed typically the cross section of the welding part of the dissimilar material welding turbine rotor welded using the Ni-base welding material of embodiment. It is the figure which showed typically the cross section of the welding part of the other structure of the dissimilar material welding turbine rotor welded using the Ni-base welding material of embodiment. It is the figure which showed typically the cross section of the welding part of the other structure of the dissimilar material welding turbine rotor welded using the Ni-base welding material of embodiment. It is a diagram showing the relationship between the content difference of C in the Fe-based turbine components as Ni-based welding material and ([Delta] CR) chemical potential difference carbon and ([Delta] [mu _C). It is a figure which shows the result of the mapping of carbon in sample 5, and a line analysis. It is a figure which shows the result of the mapping of carbon in sample 18, and a line analysis. It is a figure which shows a creep rupture test result.

  Embodiments of the present invention will be described below.

  In general, solute elements such as carbon in two bonded alloys diffuse along a concentration gradient based on Fick's first law (J = −D · ΔC / ΔX, J: flux, D: diffusion coefficient). , C: concentration, X: distance). For example, when carbon diffusion is considered, the larger the difference in carbon concentration between the two alloys, the easier the carbon diffuses. For example, when a Ni-base alloy and a Fe-base heat-resistant steel are welded together using a Ni-base welding material, a softened region is formed in the Fe-base heat-resisting steel near the boundary that is deficient in carbon due to carbon diffusion, as described above. As a result, a hardened zone is formed in the Ni-based welding material in the vicinity of the boundary where carbon is concentrated, and the creep characteristics are deteriorated. Such carbon diffusion can be suppressed by reducing the difference in carbon content (concentration) between the two alloys.

  In joining of multi-component alloys, even if the carbon concentration is the same, carbon may diffuse along the chemical potential gradient of elements in the alloy (J = −M · Δμ / ΔX, J: flux) , M: mobility, μ: chemical potential, X: distance).

Elements such as Cr, Mo, Co, etc. that can easily bond to carbon and can form carbides by combining with carbon have a negative interaction parameter with carbon, reducing the chemical potential of carbon in the alloy. It has a function to make it. In particular, Cr greatly affects the chemical potential of carbon. For example, if the difference (ΔCr) in the Cr component content (concentration) between the Fe-base heat-resistant steel and the Ni-base alloy is very large, the carbon chemical potential gradient between the Fe-base heat-resistant steel and the Ni-base alloy (Δμ _C ) increases and carbon diffuses easily. The diffusion of carbon based on the difference in the content (concentration) of the Cr component can be suppressed by reducing the difference in the content (concentration) of the Cr component.

  Therefore, the Ni-based welding material of the embodiment used when welding the first constituent member made of Fe-base heat-resistant steel and the second constituent member made of Ni-base alloy or Ni-Fe alloy is used. The following configuration was adopted.

  The difference in the Cr component content in the Ni-based welding material of the embodiment and the first and second constituent members is 14% by mass or less, respectively, and the Ni-based welding material of the embodiment, The difference of the content rate of C component in a 1st structural member and a 2nd structural member is 0.3 mass% or less, respectively.

The Ni-based welding material according to the embodiment, the difference in the Cr component content in the first component member and the second component member is 14% by mass or less, respectively. The difference in Cr component content (concentration) between the member and the second component member is reduced. Therefore, an increase in the chemical potential gradient (Δμ _C ) of carbon can be suppressed and carbon diffusion can be prevented. Here, the difference in Cr component content between the Ni-based welding material and the first and second constituent members is preferably as small as possible, and more preferably “0”.

  By making the difference in the C component content in the Ni-based welding material of the embodiment and the first and second structural members 0.3% by mass or less, the Ni-based welding material and the first The difference in the content (concentration) of the C component between the constituent member and the second constituent member becomes small. Therefore, an increase in the carbon concentration gradient can be suppressed and carbon diffusion can be prevented. Here, the difference in the content ratio of the C component in the Ni-based welding material, the first component member, and the second component member is preferably as small as possible, and more preferably “0”.

  The Ni-based welding material in the embodiment is in mass%, Cr: 8 to 25, Co: 1 to 12, Mo: 1 to 12, Al: 0.01 to 5, Ti: 0.01 to 3, C: 0.01-0.4, B: 0.001-0.01 is contained, and the balance consists of Ni and inevitable impurities.

  The Ni-based welding material in the embodiment may further contain Ta, Nb, or Ta and Nb in total and not more than 1% by mass. Moreover, the Ni-based welding material in the embodiment may contain 0.01 to 6% by mass of W.

  Examples of inevitable impurities in the Ni-based welding material in the embodiment include Fe, Si, and Mn.

  Next, the reason for limiting each composition component range in the Ni-based welding material in the above-described embodiment will be described. In the following description, “%” representing a composition component means “% by mass” unless otherwise specified.

(1) Cr (chromium)
Cr is easy to bond with carbon, and in the alloy forms a solid solution in the Ni base material or forms Cr ₂₃ C ₆ carbide to improve the strength of the material. When the Cr content is less than 8%, the above effects cannot be obtained sufficiently. On the other hand, when the Cr content exceeds 25%, the difference from the Cr content in the Fe-base heat-resisting steel, which is a joining member, increases and promotes carbon diffusion. Therefore, the Cr content is determined to be 8 to 25%. Moreover, the more preferable content rate of Cr is 10 to 22%, and the more preferable content rate of Cr is 12 to 18%.

(2) Co (cobalt)
Co is easily bonded to carbon, and solidifies in the Ni base material in the alloy and stabilizes the γ ′ (Ni ₃ (Al, Ti)) phase precipitated in the crystal grains. When the Co content is less than 1%, the above effects cannot be obtained sufficiently. On the other hand, when the Co content exceeds 12%, the difference from the Co content in the Fe-base heat-resisting steel that is the joining member increases, which promotes carbon diffusion. In addition, the σ phase (intermetallic compound) is likely to precipitate. Further, since Co is expensive, the manufacturing cost is increased. Therefore, the Co content is determined to be 1 to 12%. Further, the preferable Co content is 2 to 12%, the more preferable Co content is 4 to 12%, and the still more preferable Co content is 4 to 10%.

(3) Mo (molybdenum)
Mo is easily bonded to carbon, and in the alloy, it is solid-solved in the Ni base material or substituted with M ₂₃ C ₆ carbide to stabilize the carbide. Mo is suitable for addition to a high temperature member because it lowers the coefficient of thermal expansion of the material. When the Mo content is less than 1%, the above effects cannot be obtained sufficiently. On the other hand, when the Mo content exceeds 12%, the difference from the Mo content in the Fe-base heat-resisting steel, which is a joining member, increases and promotes carbon diffusion. Therefore, the Mo content is determined to be 1 to 12%. A more preferable Mo content is 4 to 12%, and a more preferable Mo content is 6 to 12%.

(4) Al (aluminum)
Since Al combines with Ni to form a γ ′ (Ni ₃ Al) phase, the creep strength is improved. Moreover, Al forms an oxide film on the surface and improves oxidation resistance. When the Al content is less than 0.01%, the above-described effects cannot be obtained sufficiently. On the other hand, if the Al content exceeds 5%, the workability decreases. Therefore, the Al content is determined to be 0.01 to 5%. A more preferable Al content is 0.01 to 3%.

(5) Ti (titanium)
Ti combines with Ni to generate a γ ′ (Ni ₃ (Al, Ti)) phase and improves the creep strength. When the Ti content is less than 0.01%, the above effects cannot be obtained sufficiently. On the other hand, when the Ti content exceeds 3%, the workability decreases. Therefore, the Ti content is determined to be 0.01 to 3%. A more preferable Ti content is 0.01 to 1%.

(6) C (carbon)
C dissolves in the Ni base material and improves the strength of the material. Further, C combines with Cr, Mo, Co, W, Ti, Nb, Ta, etc. to form M ₂₃ C ₆ or MC carbide. M ₂₃ C ₆ and MC carbide are mainly precipitated at the grain boundaries to suppress the coarsening of the crystal grains. When the C content is less than 0.01%, the above-described effects cannot be obtained sufficiently. On the other hand, when the C content exceeds 0.4%, the difference from the C content in the Fe-based heat-resistant steel as a joining member increases, and carbon diffuses toward the Fe-based heat-resistant steel. Therefore, the C content is determined to be 0.01 to 0.4%. A more preferable C content is 0.01 to 0.2%.

(7) B (boron)
Since B dissolves in the Ni base material and segregates particularly at the grain boundaries, the grain boundaries are strengthened. When the B content is less than 0.001%, the above-described effects cannot be obtained sufficiently. On the other hand, when the B content exceeds 0.01%, the melting point of the base material is lowered, and the hot workability is deteriorated. Therefore, the B content is determined to be 0.001 to 0.01%. A more preferable B content is 0.001 to 0.006%.

(8) Ta (tantalum) and Nb (niobium)
Ta and Nb are easily bonded to carbon, and are dissolved in the Ni base material in the alloy to promote the formation of the γ ′ (Ni ₃ (Al, Ti)) phase and stabilize it. Therefore, the strength of the material is improved. When the total content of Ta, Nb or Ta and Nb exceeds 1%, the difference between the content of Ta and Nb in the Fe-base heat-resisting steel as the joining member becomes large, and carbon diffusion is promoted. Therefore, the total content of Ta, Nb or Ta and Nb is set to 1% or less. A more preferable content ratio of Ta, Nb or Ta and Nb is 0.2 to 0.6%. In addition, the total content of Ta, Nb or Ta and Nb is at least 0.2% in order to obtain an effect of improving the strength of the material.

(9) W (tungsten)
W easily binds to carbon and forms a solid solution or WC carbide in the Ni base material in the alloy. Further, W is suitable for addition to a high temperature member because it lowers the thermal expansion coefficient of the material. When the W content is less than 0.01%, the above effects cannot be obtained sufficiently. On the other hand, when the W content exceeds 6%, the difference from the W content in the Fe-base heat-resisting steel, which is a joining member, increases and promotes carbon diffusion. Therefore, the W content is determined to be 0.01 to 6%. A more preferable W content is 0.01 to 4%.

(10) Fe (iron), Si (silicon) and Mn (manganese)
Fe, Si, and Mn are classified as inevitable impurities in the Ni-based welding material of the embodiment. Here, since Fe substitutes for Ni, the manufacturing cost can be reduced, but the creep strength is reduced and the thermal expansion coefficient is increased. Si and Mn function as a deoxidizing material when the alloy is melted. In particular, Si has an effect of improving the corrosion resistance, but decreases hot workability and toughness. It is desirable that the residual content of these inevitable impurities is as close to 0% as possible.

  Here, the manufacturing method of the Ni-base welding material of embodiment is demonstrated.

  In the Ni-based welding material of the embodiment, for example, a vacuum induction melting (VIM) is performed on the composition components constituting the Ni-based welding material, and the block shape is formed by a forging press or rolling machine, and the wire shape is drawn by a wire drawing machine or the like. It is made by forming it into a slender rod shape.

  In addition, the method for producing the Ni-based welding material of the above-described embodiment is not limited to the above-described method.

  Next, a dissimilar material welded turbine rotor welded using the Ni-based welding material of the embodiment will be described.

  FIG. 1 is a diagram schematically showing a cross section of a welded portion 50 of a dissimilar welded turbine rotor 10 welded using the Ni-based weld material of the embodiment.

  As shown in FIG. 1, an Fe-based turbine constituent member 20 that functions as a first constituent member made of Fe-base heat-resistant steel, and a Ni-base that functions as a second constituent member made of a Ni-base alloy or a Ni—Fe-based alloy. The turbine component 30 is welded and joined by the Ni-based welding material 40 in a state of being opposed to each other.

  The Fe-based turbine constituent member 20 and the Ni-based turbine constituent member 30 include cylindrical rotor body portions 21 and 31. For example, rotor disk portions 22 and 32 projecting outward in the radial direction are formed on the rotor body portions 21 and 31. The rotor disk portions 22 and 32 are provided in a plurality of stages in the turbine rotor axial direction, for example, and rotor blades are implanted in the rotor disk portions 22 and 32.

  On the center side of the joint surfaces 23 and 33 of the Fe-based turbine constituent member 20 and the Ni-based turbine constituent member 30, concave portions 24 and 34 that are recessed in the turbine rotor axial direction from the joint surfaces 23 and 33 are formed. In addition, these recessed parts 24 and 34 are formed in order to eliminate the weld joint surface of a turbine rotor center part, to improve workability, and to ease the stress concentration of a joint part.

  The joining surfaces 23 and 33 of the Fe-based turbine constituent member 20 and the Ni-based turbine constituent member 30 are welded together using the Ni-based welding material of the embodiment so that the respective central axes are coaxial, and the turbine The dissimilar material welded turbine rotor 10 is configured by integrating in the rotor axial direction.

  As a welding method, for example, TIG welding can be employed. For example, the welding is performed from the inner peripheral side to the outer peripheral side of the joint surfaces 23 and 33 while rotating the Fe-based turbine constituent member 20 and the Ni-based turbine constituent member 30.

  Here, the Fe-based turbine constituent member 20 is, for example, mass%, C: 0.1 to 0.2, Si: 0.01 to 0.4, Cr: 8 to 13, Mo: 0.5 to 1. .5, Mn: 0.01 to 0.8, V: 0.1 to 0.3, W: 0.5 to 2.0, Nb: 0.01 to 0.15, N: 0.01 to 0 0.1, Ni: 0.01 to 1.0, B: 0.001 to 0.005, Co: 2 to 4, with the balance being Fe-based heat-resistant steel made of Fe and inevitable impurities. Moreover, the Fe-based turbine constituent member 20 is, for example, mass%, C: 0.1 to 0.2, Si: 0.01 to 0.4, Cr: 8 to 13, Mo: 0.5 to 1. 5, Mn: 0.01-0.8, V: 0.1-0.3, W: 0.5-2.0, Nb: 0.01-0.15, N: 0.01-0. 1, Ni: 0.01 to 1.0 is contained, and the balance is made of Fe-based heat-resistant steel made of Fe and inevitable impurities. Furthermore, the Fe-based turbine constituent member 20 is, for example, mass%, C: 0.01 to 0.4, Si: 0.01 to 0.5, Cr: 0.5 to 2.5, Mo: 0.00. Fe-based heat resistance containing 1 to 2.0, Mn: 0.01 to 1.0, V: 0.05 to 0.4, Ni: 0.1 to 4.0, the balance being Fe and inevitable impurities Composed of steel. The Fe-based turbine constituent member 20 is not limited to these, and may be any Fe-based heat-resistant steel that is used as a turbine rotor material.

  The Ni-based turbine component 30 is, for example, in mass%, C: 0.01 to 0.15, Cr: 14 to 20, Co: 10 to 15, Mo: 8 to 12, Al: 0.5 to 4, Ti: 0.5 to 4, B: 0.001 to 0.006, Zr: 0.01 to 0.1, Ta: 0.1 to 0.7, Nb: 0.1 to 0.4 The balance is made of a Ni-based alloy composed of Ni and inevitable impurities.

  Further, the Ni-based turbine component 30 may be made of a Ni—Fe based alloy. Here, the Ni—Fe-based alloy refers to an alloy containing 30 mass% or more of Ni and mainly containing Fe and Cr as other composition components. The Ni—Fe based alloy contains Fe, for example, at least 10% by mass or more. As a Ni-Fe type alloy, for example, Cr: 14.5 to 17.5, Ti: 1.5 to 2.0, Nb: 2.5 to 3.3, Ni: 39.0 to 44 by mass% 0.0, C: 0.001 to 0.1, with the balance being Fe and inevitable impurities. Specific examples of the Ni-Fe alloy include Inconel 706 (manufactured by Special Metals).

  In addition, the material which comprises the Ni-based turbine structural member 30 is not restricted to these, What is necessary is just the Ni-based alloy or Ni-Fe type-alloy currently used as a turbine rotor material or a rotor disk material.

  Here, the difference in the Cr component content in the Ni-based welding material 40, the Fe-based turbine component 20 and the Ni-based turbine component 30 is 14% by mass or less, respectively, and the Ni-based welding material 40 and the Fe-based turbine configuration The difference in the C component content in the member 20 and the Ni-based turbine component 30 is set to be 0.3 mass% or less.

  Therefore, in FIG. 1, even after welding, the difference in the Cr component content in the Ni-based welding material 40, the Fe-based turbine component 20 and the Ni-based turbine component 30 is 14% by mass or less, respectively, and the Ni-based welding is performed. The difference of the content rate of the C component in the material 40, the Fe-based turbine constituent member 20, and the Ni-based turbine constituent member 30 is 0.3% by mass or less.

  Here, the welding method is not limited to the above-described method. FIG. 2 is a view schematically showing a cross section of a welded portion 50 of another configuration of the dissimilar material welded turbine rotor 10 welded using the Ni-based welding material of the embodiment.

  During TIG welding, the heat input may be increased and welding may be performed while melting the joint surfaces 23 and 33 of the Fe-based turbine component 20 and the Ni-based turbine component 30 together with the Ni-based weld material 40. In such a melted portion, for example, the concentrations of the Cr component and the C component change from the Ni-based welding material 40 side toward the Fe-based turbine component 20 side or the Ni-based turbine component 30 side. The graded composition layers 60 and 61 are formed.

  That is, in the joint part between the Fe-based turbine constituent member 20 and the Ni-base welding material 40 and the joint part between the Ni-base turbine constituent member 30 and the Ni-base welding material 40, the concentrations of Cr component and C component are Ni-base welding. For example, gradient composition layers 60 and 61 that continuously increase or decrease are formed from the material 40 side toward the Fe-based turbine component 20 side or the Ni-based turbine component 30 side. As a result, in the cross section of the welded portion 50 perpendicular to the axial direction of the dissimilar material welded turbine rotor 10, the concentrations of the Cr component and C component abruptly change in the axial direction of the dissimilar material welded turbine rotor 10, and the concentration difference increases. Can be prevented.

  FIG. 3 is a diagram schematically showing a cross section of a welded portion 50 of another configuration of the dissimilar material welded turbine rotor 10 welded using the Ni-based welding material of the embodiment.

  As shown in FIG. 3, bonding layers 70, 71, and 72 made of a Ni-based welding material 40 are provided between the Fe-based turbine component 20 and the Ni-based turbine component 30 in the axial direction of the dissimilar material welded turbine rotor 10. A plurality of stages may be formed. When the weld 50 is formed, first, the joining layer 70 is formed on the joint surface 23 of the Fe-based turbine constituent member 20 by buttering welding using a Ni-base welding material. Similarly, the Ni-base turbine constituent member 30 is formed. The joining layer 71 is formed on the joining surface 33 by buttering welding using a Ni-based welding material. Subsequently, the joining layer 70 and the joining layer 71 are TIG welded using a Ni-based welding material to form the joining layer 72.

  Here, the difference in the Cr component content in the Ni-based welding material 40, the Fe-based turbine component 20 and the Ni-based turbine component 30 is 14% by mass or less, respectively, and the Ni-based welding material 40 and the Fe-based turbine configuration The difference in the C component content in the member 20 and the Ni-based turbine component 30 is set to be 0.3 mass% or less.

  Therefore, in FIG. 3, even after welding, the difference in the Cr component content in the bonding layer 70 and the Fe-based turbine component 20 and the difference in the Cr component content in the bonding layer 71 and the Ni-based turbine component 30 are as follows. , Each is 14 mass% or less. Further, the difference in the C component content in the bonding layer 70 and the Fe-based turbine component 20 and the difference in the C component content in the bonding layer 71 and the Ni-based turbine component 30 are 0.3% by mass or less, respectively. It has become. Furthermore, the difference in the Cr component content in the bonding layer 72, the bonding layer 70, and the bonding layer 71 is 14% by mass or less, respectively, and the difference in the C component content in the bonding layer 72, the bonding layer 70, and the bonding layer 71. Is 0.3% by mass or less.

  As described above, after welding the Fe-based turbine component 20 and the Ni-based turbine component 30, the heat treatment for removing the residual stress at the joint is, for example, at a temperature of 560 to 680 ° C. for 2 to 10 hours. Heat treatment is applied.

The above-mentioned dissimilar material welded turbine rotor 10 can be applied to a power generation turbine such as a steam turbine, a gas turbine, or a CO ₂ turbine.

  According to the Ni-based welding material and the dissimilar material-welded turbine rotor of the above-described embodiment, the diffusion of carbon between the Ni-based welding material 40, the Fe-based turbine component member 20, and the Ni-based turbine component member 30 is suppressed. Can do. Therefore, excellent creep strength can be obtained without forming a carbon-deficient region or a carbon-concentrated region.

(Evaluation of chemical potential and creep strength)
Here, the chemical potential and creep strength of the dissimilar material welded turbine rotor welded and joined using the Ni-based welding material of the embodiment were evaluated. Table 1 shows the chemical compositions of Sample 1 to Sample 19 relating to the Ni-based welding material used for the evaluation.

  Samples 1 to 12 are Ni-based welding materials in the chemical composition range of the Ni-based welding material of the embodiment, and Samples 13 to 19 are chemistry of the Ni-based welding material of the embodiment. It is a Ni-based welding material that is not within the composition range and is a comparative example.

  In Sample 1 to Sample 8 and Sample 13 to Sample 17, the Fe-based turbine constituent member 20 is expressed by mass% in the range of materials constituting the Fe-based turbine constituent member 20 described above, and C: 0.14 , Si: 0.05, Cr: 10.5, Mo: 1, Mn: 0.5, V: 0.2, W: 1, Nb: 0.07, N: 0.05, Ni: 0.75 Fe-based heat-resisting steel with the balance being Fe and inevitable impurities was used.

  In Sample 9 to Sample 12 and Sample 18 to Sample 19, the Fe-based turbine component 20 is represented by mass% in the range of materials constituting the Fe-based turbine component 20 described above, and C: 0.3 Fe: Si: 0.25, Cr: 1.1, Mo: 1.2, Mn: 0.7, V: 0.25, Ni: 0.5, the balance being Fe and inevitable impurities Heat resistant steel was used.

  In Sample 1 to Sample 19, as the Ni-based turbine component 30, C: 0.05, Cr: 18, Co: in terms of mass% in the range of materials constituting the Ni-based turbine component 30 described above. 13, Mo: 9, Al: 1.3, Ti: 1.4, B: 0.004, Zr: 0.05, Ta: 0.1, Nb: 0.3, the balance being Ni and inevitable A Ni-based alloy composed of mechanical impurities was used.

Then, using the structure shown in FIG. 1 as an analysis model, using a thermodynamic equilibrium calculation software (Thermocalc), the difference in the chemical potential of carbon in the ferrite phase of Fe-base heat-resistant steel and the austenite phase of Ni-base alloy at 640 ° C. (Δμ _C ) was obtained by calculation. The results are shown in Table 1.

Table 1 shows the results for the joint between the Fe-based turbine component 20 and the Ni-based welding material 40. Table 1 also shows the difference in Cr content (ΔCr) and the difference in C content (ΔC) between the Fe-based turbine component 20 and the Ni-based welding material 40. FIG. 4 is a view showing the relationship between the C content difference (ΔCr) and the carbon chemical potential difference (Δμ _C ) between the Fe-based turbine constituent member 20 and the Ni-based welding material 40.

Here, although the results regarding the joint between the Ni-based turbine component 30 and the Ni-based welding material 40 are not illustrated, the Cr content difference (ΔCr) is 14 mass in all the samples. %, And the difference in C content (ΔC) was 0.3% by mass or less, so that no significant difference was found in the chemical potential difference (Δμ _C ) of carbon.

  The presence or absence of carbon diffusion was determined by aging the dissimilar welded turbine rotor welded and bonded using the Ni-based welding material of the embodiment at a temperature of 640 ° C. for 300 hours, and then the Fe-based turbine component 20 and the Ni. Judgment was made based on the mapping of carbon with an electron beam microprobe analyzer (EPMA) with respect to the boundary with the base welding material and the result of line analysis on a predetermined line. FIG. 5 is a diagram showing the results of carbon mapping and line analysis in Sample 5. As shown in FIG. FIG. 6 is a diagram showing the results of carbon mapping and line analysis in the sample 18. 5 and 6, the position where the position on the analysis line is 1.0 is the boundary between the Fe-based turbine constituent member 20 and the Ni-based welding material 40.

  In addition, although the result in the sample 5 and the sample 18 is shown here, the result in the sample 1 to the sample 4 and the sample 6 to the sample 12 showed the same tendency as the result in the sample 5 shown in FIG. Further, the results of Samples 13 to 17 and Sample 19 showed the same tendency as the results of Sample 18 shown in FIG.

As shown in Table 1 and FIG. 4, the chemical potential difference (Δμ _C ) of carbon increases as the Cr content difference (ΔCr) increases. The chemical potential difference (Δμ _C ) of carbon in Sample 1 to Sample 12 in which the Cr content difference (ΔCr) is 14% by mass or less is the Sample 13 to Sample in which the Cr content difference (ΔCr) exceeds 14% by mass. It can be seen that it is smaller than the chemical potential difference (Δμ _C ) of carbon at 19. That is, it can be seen that Sample 1 to Sample 12 hardly cause carbon diffusion, and Sample 13 to Sample 19 easily cause carbon diffusion.

  This is also apparent from the results of carbon mapping and line analysis in Sample 5 and Sample 18 shown in FIGS. 5 and 6, respectively. That is, as shown in FIG. 5, in sample 5, no clear intensity peak occurs in the line analysis, and the carbon at the boundary between the Fe-based turbine constituent member 20 and the Ni-based welding material is homogeneous even after aging treatment. It can be seen that the distribution is maintained. Therefore, it can be seen that in Sample 5, a normal structure is maintained at the boundary between the Fe-based turbine constituent member 20 and the Ni-based welding material even after the aging treatment.

  On the other hand, as shown in FIG. 6, the sample 18 has a clear intensity peak in the line analysis, and after the aging treatment, the carbon at the boundary between the Fe-based turbine component 20 and the Ni-based welding material has a homogeneous distribution. It can be seen that is not maintained. Further, in the sample 18, an embrittlement phase parallel to the boundary between the Fe-based turbine constituent member 20 and the Ni-based welding material was precipitated. The embrittlement phase was observed with a scanning electron microscope (SEM).

  From the above, in Sample 5 and Sample 1 to Sample 4 and Sample 6 to Sample 12, which showed the same tendency as Sample 5, at the boundary between the Fe-based turbine component 20 and the Ni-based welding material at a high temperature. It became clear that the diffusion of carbon was suppressed during long-term use and the tissue stability was excellent.

  Next, a creep rupture strength test was performed on a test piece in which a predetermined shape Fe-base heat-resistant steel and a Ni-base alloy were welded using the Ni-base welding material consisting of Sample 5 and Sample 18. The Fe-base heat-resistant steel and Ni-base alloy welded by the sample 5 were made of the same material as the Fe-base turbine constituent member 20 and the Ni-base turbine constituent member 30 welded and joined by the sample 5 described above. The Fe-base heat-resistant steel and Ni-base alloy welded by the sample 18 were made of the same material as the Fe-base turbine constituent member 20 and the Ni-base turbine constituent member 30 welded and joined by the sample 18 described above.

  And after welding, as heat processing which removes the residual stress of a junction part, the heat processing for 4 hours was performed at the temperature of 640 degreeC.

  The creep rupture test was performed according to JIS Z 2271 under a stress of 40 to 300 MPa and a temperature of 550 to 650 ° C. FIG. 7 is a diagram showing the creep rupture test results. FIG. 7 shows the results organized by Larson-Miller-Parameter (material constant C is 20).

  Here, the results for Sample 5 and Sample 18 are shown, but the results for Sample 1 to Sample 4 and Sample 6 to Sample 12 showed the same tendency as the results for Sample 5 shown in FIG. Further, the results of Samples 13 to 17 and Sample 19 showed the same tendency as the results of Sample 18 shown in FIG.

  As shown in FIG. 7, it was found that the breaking stress in sample 5 was higher than the breaking stress in sample 18. Further, the creep rupture portion was a boundary between the Ni-based alloy in the sample 5 and the boundary between the Fe-based heat-resistant steel and the Ni-based welding material in the sample 18. From this, it is considered that in Sample 5, the strength of the boundary between the Fe-base heat-resistant steel and the Ni-base weld material is improved.

  Although not shown, the breaking stress in sample 5 was higher than that in samples 13 to 17 and sample 19. Moreover, the breaking stress in Sample 1 to Sample 4 and Sample 6 to Sample 12 was also higher than the breaking stress in Sample 13 to Sample 19.

  From the above, it was revealed that Sample 1 and Sample 1 to Sample 4 and Sample 6 to Sample 12 showing the same tendency as Sample 5 have excellent creep strength.

  In addition, although said each evaluation was performed using the Ni base alloy of the range of the material which comprises the Ni base turbine structural member 30 mentioned above as the Ni base turbine structural member 30, the Ni base turbine structural member mentioned above Even when a Ni—Fe based alloy in the range of materials constituting 30 was used, the same result as that obtained when a Ni-based alloy was used was obtained.

  According to the embodiment described above, it is possible to weld-join dissimilar materials made of Fe-base heat-resistant steel and Ni-base alloy or Ni-Fe alloy so as to have excellent creep strength.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Dissimilar material welded turbine rotor, 20 ... Fe base turbine structural member, 21, 31 ... Rotor body part, 22, 32 ... Rotor disk part, 23, 33 ... Joining surface, 24, 34 ... Recessed part, 30 ... Ni base turbine structure 40, Ni-based welding material, 50, welded portion, 60, gradient composition layer, 70, 71, 72, bonding layer.

Claims (6)

A Ni-based welding material used when welding and joining a first constituent member made of Fe-base heat-resistant steel and a second constituent member made of a Ni-base alloy or a Ni-Fe-based alloy,
The difference in the content of Cr components in the Ni-based welding material, the first component member, and the second component member is 14% by mass or less, respectively, and the Ni-based welding material and the first configuration The difference in the content of C component in the member and the second component member is 0.3% by mass or less,
The Ni-based welding material is in mass%, Cr: 8 to 25, Co: 1 to 12, Mo: 1 to 12, Al: 0.01 to 5, Ti: 0.01 to 3, C: 0.01 A Ni-based welding material containing -0.4, B: 0.001-0.01, with the balance being Ni and inevitable impurities.   The Ni-based welding material according to claim 1, further comprising Ta, Nb, or Ta and Nb in total and further containing 1% by mass or less.   The Ni-based welding material according to claim 1 or 2, further comprising 0.01 to 6% by mass of W. The first constituent member made of Fe-base heat-resistant steel and the second constituent member made of Ni-base alloy or Ni-Fe alloy are contacted with the Ni-base welding material according to any one of claims 1 to 3. welding different materials turbine rotor, characterized by comprising a multiplexer.   Concentrations of at least the Cr component and the C component in the joint portion between the first constituent member and the Ni-base welding material and the joint portion between the second constituent member and the Ni-base welding material are such that the Ni-base welding is performed. 5. The dissimilar welded turbine rotor according to claim 4, further comprising a gradient composition layer that changes from a material side toward the first component member side and the second component member side.   5. The joining layer made of the Ni-based welding material is formed in a plurality of stages in the axial direction of the dissimilar material welded turbine rotor between the first constituent member and the second constituent member. The dissimilar welded turbine rotor described.

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