JP2008093668A - Steam turbine welding rotor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welded rotor of a steam turbine, which rotor is composed by joining different kinds of materials and has excellent welded portions. <P>SOLUTION: The welded rotor of the steam turbine is formed by welding a rotor made of a high Cr steel and a rotor made of a low Cr steel containing Cr smaller than that of the rotor made of the high Cr steel. The welding metal joining the high Cr steel and the low Cr steel contains 0.05 to 0.15 mass% C, 1 mass% or less Si, 2 mass% or less Mn, 0.03 mass% or less P, 0.03 mass% or less S, 0.5 mass% or less Cu, 0.5 mass% or less Ni, 1.0 to 3.5 mass% Cr, 0.4 to 1.2 mass% Mo, 0.05 to 0.4 mass% V, at least one of Nb, Ta, Zr, and Hf in an amount of 0.01 to 0.1 mass% in total, and the balance being Fe. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steam turbine welded rotor.

  Due to increasing environmental problems, steam turbine power plants are required to have higher efficiency and higher output capacity, and steam temperatures are being increased at higher temperatures and pressures.

  Conventionally, an integrated rotor has been applied to a steam turbine rotor with the development of forging heat treatment technology.

  Further, in order to reduce the weight and simplify the structure of the steam turbine, a high-low pressure integrated rotor that is integrally formed of the same material from high pressure to low pressure is used.

  However, it can be said that these steam turbine rotors have limitations with regard to higher temperatures and larger capacities.

  The properties (materials) required for the material (rotor material) forming the steam turbine rotor (hereinafter sometimes simply referred to as “rotor”) are high-temperature creep rupture strength at high pressure and tensile strength and toughness at low pressure. It is.

  Thus, it is difficult for the rotor to satisfy both high and low pressure characteristics with a single material, and the required characteristics are different for each stage of the steam turbine.

  For example, Patent Document 1 and Patent Document 2 show welded structure rotors in which optimum materials are selected for each paragraph or each of a plurality of paragraphs and welded to each other.

  Moreover, there is Patent Document 3 as a method of joining (integrating) different materials at the time of remelting in the manufacturing process.

  Compared to the case of manufacturing a large integral rotor, small steel ingots such as each paragraph or multiple paragraphs have the advantage that high-quality steel ingots can be easily obtained and large-scale production equipment is not required. .

USP 6152697 JP 2000-64805 A Japanese Patent Publication No. 56-14842

  Conventional rotor materials are difficult to produce large steel ingots corresponding to high temperatures and large capacities, and it is necessary to form a rotor by welding a high-quality small steel ingot in a divided structure.

  In particular, in the case of a welded structure rotor in which an optimum material is selected for each paragraph or every plurality of paragraphs and they are welded, it is necessary to join different materials (different materials).

  When welding dissimilar materials, buttering welding for forming a concentration gradient layer is required due to differences in alloy component concentrations and temper softening resistance. That is, two types of weld metal are required. Buttering welding requires groove processing before stress welding, stress relief annealing, and groove rework before main welding. The increase in weld volume due to buttering and main welding increases the possibility of weld defects. Let

  Therefore, the present invention provides a steam turbine welding rotor formed by joining different materials without performing such buttering welding.

A steam turbine welded rotor according to an embodiment of the present invention is formed by welding at least a high Cr steel rotor and a low Cr steel rotor having a lower Cr content than a high Cr steel rotor. The weld metal joining the high Cr steel rotor and the low Cr steel rotor is C:
0.05 to 0.15%, Si: 1% or less, Mn: 2% or less, P: 0.03% or less, S: 0.03% or less, Cu: 0.5% or less, Ni: 0.5 % Or less, Cr: 1.0 to 3.5%, Mo: 0.4 to 1.2%, V: 0.05 to 0.4%, and at least four of Nb, Ta, Zr, and Hf 1 type is contained, the sum total is 0.01-0.1%, and the remainder consists of Fe.

  And it is preferable that the welding part of a high Cr steel rotor and a low Cr steel rotor makes hollow the center side of the surface which crosses an axis | shaft, and forms a narrow groove part.

  Moreover, it is preferable that the segregation index | exponent P defined by 2Mo + 10V + 7 (Nb + Ta + Zr + Hf) (mass%) is 3-7 in a weld metal.

  The high Cr steel rotor is characterized by containing 8 to 13% Cr by mass, and the low Cr steel rotor is characterized by containing 0.8 to 2.5% Cr by mass. . And it is preferable that the difference in Cr content between the high Cr steel rotor and the low Cr steel rotor is 6% or more.

The steam turbine welded rotor according to an embodiment of the present invention is formed by welding at least a high Cr steel rotor and a low Cr steel rotor having a lower Cr content than a high Cr steel rotor. 2Mo + of weld metal that joins high Cr steel rotor and low Cr steel rotor
The segregation index P defined by 10V + 7 (Nb + Ta + Zr + Hf) (mass%) is 3-7.

  Hereinafter, the reason for limiting the component of each element of the weld metal will be described.

  The component of each element contained in Fe of the weld metal is C: 0.05 to 0.15%, Si: 1% or less, Mn: 2% or less, P: 0.03% or less, S: 0% by mass. 0.03% or less, Cu: 0.5% or less, Ni: 0.5% or less, Cr: 1.0 to 3.5%, Mo: 0.4 to 1.2%, V: 0.05 to 0 .4% and at least one of Nb, Ta, Zr, and Hf is contained, and the total is 0.01 to 0.1%.

  C is an element indispensable for ensuring hardenability and precipitating carbides in the annealing process to increase the high temperature strength, and 0.05% or more is necessary, but addition exceeding 0.15% In order to raise the cracking sensitivity of welding, it is limited to 0.05 to 0.15%. Desirably, it is 0.06 to 0.14%, and 0.06 to 0.12% is particularly preferable.

  Si is added as a deoxidizing material, and the effect can be achieved by adding a small amount. Addition in excess of 1% is not preferable because it tends to cause solidification cracking.

  Mn is added as a desulfurization / deoxidation material, and the effect can be achieved by adding a small amount. Moreover, S mentioned later raises the cracking sensitivity of welding, but Mn reacts with S to form a MnS compound and also has an effect of fixing S, and suppresses cracking of welding. Addition in excess of 2% is not preferable because it reduces the creep rupture strength.

P and S are contained as impurities in the steel. Since it concentrates at the grain boundary at the final stage of solidification and segregation occurs, it is desirable to reduce it because it increases the cracking susceptibility of the weld, and each is preferably 0.03% or less.

  Cu is contained as an impurity in steel and reduces toughness while being used at high temperatures. Separation from Fe is difficult, and considering the current steelmaking level, it is preferably 0.5% or less.

  Ni is an effective element that increases toughness and suppresses the formation of δ ferrite, but is preferably 0.5% or less in order to reduce the creep rupture strength.

  Cr improves hardenability and has the effect of improving toughness and high-temperature strength. It also improves the corrosion resistance in steam. If less than 1.0%, these effects are not sufficient, and addition exceeding 3.5% lowers the creep rupture strength. Desirably, it is 1.1 to 3.0%, and 1.2 to 2.8% is particularly preferable.

  Mo is added to increase the high temperature strength. If less than 0.4%, these effects are not sufficient, and addition exceeding 1.2% lowers toughness. Desirably, it is 0.5 to 1.1%, and particularly preferably 0.6 to 1.0%.

  V precipitates fine carbides in the crystal grains during the tempering treatment, and has an effect of improving high temperature strength and toughness. If it is less than 0.05%, these effects are not sufficient, and if it exceeds 0.4%, the effect is saturated. Desirably, it is 0.10 to 0.33%, and 0.15 to 0.30% is particularly preferable.

  The addition of at least one of the four types of Nb, Ta, Zr, and Hf has the effect of generating carbides, fixing C, and increasing toughness.

  0.01% or more is necessary, but addition exceeding 0.1% increases the cracking susceptibility of the weld. A sufficient effect can be obtained with addition of 0.01 to 0.10%, alone or in combination.

  When welding materials having different Cr contents, C moves to the high Cr content material side, forms Cr carbide at the weld interface, reduces the toughness of the weld interface, and decreases the strength of the weld metal part. For this reason, it is necessary to suppress the movement of C.

  The segregation index P of the weld metal is defined as 2Mo + 10V + 7 (Nb + Ta + Zr + Hf) (mass%). The index P is preferably 3-7.

  Moreover, the specific composition of a low Cr steel rotor and a high Cr steel rotor is shown below.

  The low Cr steel rotor is in mass%, C: 0.15 to 0.40%, Si: 0.15% or less, Mn: 0.05 to 1.50%, Ni: 0.2 to 1.5% , Cr: 0.8-1.5%, Mo: 0.8-1.8%, V: 0.1-0.3%, P: 0.012% or less, S: 0.015% or less And the balance is substantially made of Fe.

The high Cr steel rotor is, by mass%, C: 0.05 to 0.25%, Si: 0.15% or less, Mn: 1.00% or less, Ni: 0.75% or less, Cr: 9.0 -13.0%, Mo: 0.05-
1.50%, W: 3.0% or less, V: 0.05 to 0.30%, Nb: 0.01 to 0.20%,
Co: 5.0% or less, N: 0.01 to 0.10%, B: 0.0001 to 0.030%, with the balance being substantially made of Fe.

  The steam turbine welded rotor according to an embodiment of the present invention is formed by welding at least a high Cr steel rotor and a low Cr steel rotor having a lower Cr content than the high Cr steel rotor. And the high Cr steel rotor and the low Cr steel rotor are joined by one kind of weld metal.

  A steam turbine according to an embodiment of the present invention includes at least a high Cr steel rotor and a rotor formed by welding a low Cr steel rotor having a lower Cr content than a high Cr steel rotor, A first moving blade formed on a Cr steel rotor, a second moving blade formed on a low Cr steel rotor, a stationary blade for introducing steam to the first moving blade and the second moving blade, And a casing covering the stationary blade, and the high Cr steel rotor and the low Cr steel rotor are joined by one kind of weld metal.

  The high Cr steel rotor and the low Cr steel rotor of the rotor are connected by butt welding with the center side of the surface crossing the shaft being hollow.

  The reason why the respective components of the low Cr steel rotor and the high Cr steel rotor are limited will be described below.

  The low Cr steel rotor is, by mass%, C: 0.15 to 0.40%, Si: 0.15% or less, Mn: 0.05 to 1.50%, Ni: 0.2 to 1.5% , Cr: 0.8-1.5%, Mo: 0.8-1.8%, V: 0.1-0.3%, P: 0.012% or less, S: 0.015% or less And the balance is substantially made of Fe.

  It shows about a low Cr steel rotor.

  C is an element necessary for improving hardenability and ensuring high temperature strength. If it is 0.15% or less, sufficient hardenability cannot be obtained, and a soft ferrite structure is formed at the center of the rotor, so that sufficient tensile strength and yield strength cannot be obtained. Moreover, addition exceeding 0.40% reduces toughness. Therefore, C is limited to 0.15 to 0.40%. The range of 0.20 to 0.35% is particularly preferable, and the range of 0.23 to 0.32% is more preferable.

  Si is a deoxidizer and is added when steel is melted, and even a small amount is effective. When a carbon vacuum deoxidation method or an electroslag remelting method is used, it is not necessary to add Si, and it is preferable to add no Si. Therefore, Si is preferably 0.15% or less, particularly preferably 0.10% or less, and more preferably 0.05% or less.

Mn is a desulfurization / deoxidation agent, which is added when steel is melted, and is effective even in a small amount. Mn exists as an impurity element in steel, and has the effect of fixing S, which deteriorates hot workability, as sulfide MnS. For this reason, Mn should be 0.05% or more in the production of large forgings such as steam turbine rotor shafts. On the other hand, addition over 1.5% tends to cause creep embrittlement and weakens the notch, so it is made 1.5% or less. In particular, a range of 0.10 to 1.3% is preferable, and a range of 0.15 to 1.2% is more preferable.

  Ni is an element that improves hardenability and is essential for improving toughness. If it is less than 0.2%, the effect of improving toughness is not sufficient. Addition exceeding 1.5% lowers the creep rupture strength. In particular, the range of 0.3 to 1.3% is preferable, and the range of 0.4 to 1.2% is more preferable.

  Cr improves hardenability and has the effect of improving toughness and high-temperature strength. It also improves the corrosion resistance in steam. If less than 0.8%, these effects are not sufficient, and addition exceeding 1.5% reduces the creep rupture strength. The range of 0.9 to 1.4% is particularly preferable, and the range of 1.0 to 1.3% is more preferable.

  Mo precipitates fine carbides in crystal grains during the tempering treatment, and has the effect of improving the high-temperature strength and preventing temper embrittlement. If less than 0.8%, these effects are not sufficient, and addition exceeding 1.8% lowers toughness. In particular, a range of 1.0 to 1.6% is preferable, and a range of 1.2 to 1.5% is more preferable.

  V precipitates fine carbides in the crystal grains during the tempering treatment, and has an effect of improving high temperature strength and toughness. If it is less than 0.10%, these effects are not sufficient, and if it exceeds 0.30%, the effect is saturated. The range of 0.15 to 0.28% is particularly preferable, and the range of 0.20 to 0.25% is more preferable.

Reduction of P and S has an effect of increasing creep rupture strength and low temperature toughness, and it is desirable to reduce it as much as possible. From the viewpoint of improving low temperature toughness, P is preferably 0.012% or less, and S is preferably 0.015% or less. In particular, P is preferably 0.010% or less and S is preferably 0.013% or less, more preferably P is 0.008% or less and S is 0.010% or less.

  Reduction of Sb, Sn and As also has the effect of increasing low temperature toughness, and it is desirable to reduce it as much as possible. However, from the viewpoint of the current steelmaking technology level, Sb is 0.0015% or less, Sn is 0.01% or less, and As is 0.02. % Or less is preferable. In particular, Sb is 0.0010% or less, Sn 0.005% and As 0.01% or less.

  In the heat treatment of the low Cr steel rotor material, first, it is uniformly heated and held at a temperature sufficient for transformation into complete austenite, at least 900 ° C., and at maximum 1000 ° C. for a predetermined time, and then rapidly cooled (preferably oil cooling or water spray) . When the temperature is lower than 900 ° C., high toughness is obtained, but high creep rupture strength cannot be obtained. When the temperature exceeds 1000 ° C., high creep rupture strength is obtained, but high toughness cannot be obtained.

  Next, it is preferable to perform tempering by cooling after heating and holding at a temperature of 630 to 700 ° C. for a predetermined time to obtain a fully tempered bainite structure. If it is less than 630 ° C., high toughness cannot be obtained, and if it exceeds 700 ° C., high creep rupture strength cannot be obtained.

  Further, in order to further adjust the strength and toughness after tempering, tempering by heating and holding at a temperature of 630 to 700 ° C. can be repeated as necessary. By repeating tempering, the strength is reduced but the toughness is improved.

The high Cr steel rotor is, by mass%, C: 0.05 to 0.25%, Si: 0.15% or less, Mn: 1.00% or less, Ni: 0.75% or less, Cr: 9.0 ˜13.0%, Mo: 0.05-
1.50%, W: 3.0% or less, V: 0.05 to 0.30%, Nb: 0.01 to 0.20%,
Co: 5.0% or less, N: 0.01 to 0.10%, B: 0.0001 to 0.030%, with the balance being substantially made of Fe.

  It shows about a high Cr steel rotor.

  C is an indispensable element for improving hardenability and precipitating carbides during the tempering heat treatment process to ensure high temperature strength. Moreover, in order to obtain high tensile strength, 0.05% or more is necessary. However, if it exceeds 0.25%, the metal structure becomes unstable when exposed to high temperature for a long time, so that Reduces creep rupture strength. Therefore, it is limited to 0.05 to 0.25%. In particular, a range of 0.07 to 0.20% is preferable, and a range of 0.09 to 0.16% is more preferable.

  Si is added as a deoxidizer, but when a carbon vacuum deoxidation method or the like is used, it is not necessary to add Si, and it is preferable to add no Si. Lowering the addition of Si has the effect of preventing the formation of δ ferrite structure and the reduction in toughness due to segregation of grain boundaries. When it is added, it is preferably 0.15% or less, particularly preferably 0.10% or less, and more preferably 0.05% or less.

  Mn is added as a desulfurization / deoxidation agent, and the effect can be achieved even when added in a small amount. Addition in excess of 1.00% is not preferable because it reduces the creep rupture strength. The range of 0.03% to 0.70% is particularly preferable. When the addition of Mn is small, the strength is high, but when the addition of Mn is large, the workability is good.

  Ni is an effective element for increasing toughness and preventing the formation of δ ferrite structure. However, if it is less than 0.05%, this effect is not sufficient, and addition exceeding 0.75% causes creep rupture. Reduce strength.

  Cr is an indispensable element for increasing the high temperature strength and high temperature oxidation resistance, and 9.0% or more is necessary. However, if it exceeds 13.0%, a δ ferrite structure is formed, and the high temperature strength and In order to reduce toughness, the range of 9.0 to 13.0% is preferable, particularly the range of 9.5 to 12.0% is preferable, and the range of 10.0 to 11.5% is more preferable. .

  Mo precipitates fine carbides in crystal grains during the tempering treatment, and is effective in improving high-temperature strength and preventing temper embrittlement. If it is less than 0.05%, these effects are not sufficient, and if it exceeds 1.50%, the toughness is lowered. In particular, a range of 0.15 to 1.30% is preferable, and a range of 0.2 to 1.1% is more preferable.

  W suppresses agglomeration and coarsening of carbides at high temperatures and strengthens the matrix by solid solution, so that it has an effect of remarkably increasing the high temperature strength at 620 ° C. or higher. Addition over 3.0% produces a δ ferrite structure and lowers toughness, so 3.0% or less is preferable.

V precipitates fine carbides in the crystal grains during the tempering treatment, and has an effect of improving high temperature strength and toughness. If it is less than 0.05%, these effects are not sufficient, and if it exceeds 0.30%, the effect is saturated. In particular, a range of 0.10 to 0.28% is preferable, and more preferably,
It is in the range of 0.15 to 0.25%.

  Nb is an effective element for precipitating NbC carbide and increasing the high-temperature strength, but the addition exceeding 0.2% produces coarse eutectic NbC carbide, particularly in large steel ingots, and lowers fatigue strength. Since it causes precipitation of δ ferrite structure, 0.20% or less is preferable. Further, if it is less than 0.01%, these effects are not sufficient. The range of 0.02 to 0.15% is particularly preferable, and the range of 0.04 to 0.10% is more preferable.

  Co significantly improves high-temperature strength and increases toughness. Addition exceeding 5.0% decreases ductility. For this reason, 5.0% or less is preferable. In particular, a range of 0.1 to 4.0% is preferable, and a range of 1.0 to 3.0% is more preferable.

  N is effective in improving the creep rupture strength and preventing the formation of δ ferrite structure, but if less than 0.01%, this effect is not sufficient, and the addition exceeding 0.10% reduces the toughness and creep rupture strength. Also reduce. In particular, the range of 0.01 to 0.06% is preferable, and more preferably 0.015 to 0.050%.

B has an effect of strengthening the grain boundary. B is solid-dissolved in the M23C6 type carbide,
There exists an effect | action which prevents the aggregation coarsening of M23C6 type carbide, and there exists an effect which raises high temperature strength. Although 0.0001% or more is effective, addition exceeding 0.03% harms weldability and forgeability, so 0.0001 to 0.03% is preferable. In particular, the range of 0.0001 to 0.018% is preferable, and the range of 0.001 to 0.013% is more preferable.

Reduction of P and S has an effect of increasing creep rupture strength and low temperature toughness, and it is desirable to reduce it as much as possible. From the viewpoint of improving low temperature toughness, P is preferably 0.012% or less, and S is preferably 0.015% or less. In particular, P is preferably 0.010% or less and S is preferably 0.013% or less, more preferably P is 0.008% or less and S is 0.010% or less.

  Reduction of Sb, Sn and As also has the effect of increasing low temperature toughness, and it is desirable to reduce it as much as possible. However, from the viewpoint of the current steelmaking technology level, Sb is 0.0015% or less, Sn is 0.01% or less, and As is 0.02. % Or less is preferable. In particular, Sb is 0.0010% or less, Sn 0.005% and As 0.01% or less.

  In the heat treatment of the high Cr steel rotor material, first, it is uniformly heated and held at a temperature sufficient for transformation into complete austenite, a minimum of 1000 ° C. and a maximum of 1125 ° C. for a predetermined time, and then rapidly cooled (preferably oil cooling or water spray). . When the temperature is lower than 1000 ° C., high toughness can be obtained, but high creep rupture strength cannot be obtained. When the temperature exceeds 1125 ° C., high creep rupture strength can be obtained, but high toughness cannot be obtained.

  Next, it is preferable to perform tempering by cooling after heating and holding at a temperature of 630 to 750 ° C. for a predetermined time to obtain a fully tempered martensite structure. If it is less than 630 ° C., high toughness cannot be obtained, and if it exceeds 750 ° C., high creep rupture strength cannot be obtained.

  Further, in order to further adjust the strength and toughness after tempering, tempering by heating and holding at a temperature of 630 to 750 ° C. can be repeated as necessary. By repeating tempering, the strength is reduced but the toughness is improved.

  The present invention can provide a steam turbine welding rotor formed by joining different materials without performing buttering welding.

  Hereinafter, the best mode for carrying out the present invention will be described in detail by way of specific examples, but the present invention is not limited to these examples.

  FIG. 1 is a configuration diagram of a joint portion of a steam turbine welding rotor according to the present embodiment.

  The high Cr steel rotor 1 and the low Cr steel rotor 2 are abutted.

  The groove 6 has an R (curved surface) 5 so that the welding surface is not flush with the shaft surface, and forms a raised portion 3 on the inner peripheral side of the rotor and a raised portion 4 on the outer peripheral side of the rotor. And ensuring the strength at the weld. The narrow groove 7 is welded by TIG welding or the like.

  FIG. 2 is an enlarged view of a joint portion of the steam turbine welding rotor shown in FIG.

  The height b of the raised portion 3 and the height a of the raised portion 4 are 10 mm, the groove depth d is 100 mm, the distance w between the narrow grooves 7 is 12 mm, the root face e is 2 mm, and the distance at the root face is 0 mm. To do.

  In order to investigate the characteristics of the joint, which is a welded portion, the high Cr steel rotor 1 and the low Cr steel rotor 2 were joined by TIG welding in a simulated manner, the cross-sectional structure was observed, and a fracture investigation was performed.

  Table 1 shows the chemical composition of each rotor, and Table 2 shows the chemical composition of the weld metal as a welding wire.

  Base material A in Table 1 simulates a low Cr steel rotor 2, and base material B in Table 1 simulates a high Cr steel rotor 1.

  Moreover, weld metal No.1-No.2, No.7-No.10, and No.12 in Table 2 are the chemical compositions shown as a comparative example with respect to this form, and weld metal No.3 in Table 2 is shown. ~ No.6 and No.11 are chemical compositions in this embodiment.

  Welding was performed at a temperature between passes of 400 ° C. or less after preheating the joint to 250 ° C. to 300 ° C. After welding, the temperature was kept at 400 ° C., dehydrogenation treatment was performed, and the temperature was raised to 630 ° C. to remove residual stress.

  FIG. 3 shows the hardness distribution of the joint when weld metals No. 7, No. 10, and No. 11 are used.

As shown in FIG. 3, the hardness of the HAZ portion hardly changed in any of the weld metals of No. 7, No. 10 and No. 11. The HAZ portion is a base material portion in the vicinity of the welded portion, and is a portion where the temperature of the base material rises due to the influence of welding. In the case of this embodiment, since the interval w of the narrow groove 7 is 12 mm, −6 to −6.5 mm and +6 to +6.5 mm correspond to the HAZ portion.

  FIG. 4 shows the results of a creep test performed on the weld metal shown in Table 2 at a temperature of 550 ° C. and a load stress of 196 MPa.

  The weld metals No. 1 to No. 2 and No. 7 to No. 10 having chemical compositions shown as comparative examples for this embodiment have a fracture position of the HAZ part on the high Cr steel side and a short fracture time. all right. On the other hand, it was found that weld metals No. 3 to No. 6 and No. 11 which are chemical compositions in this embodiment have a fracture position of the HAZ portion on the low Cr steel side and a long fracture time.

  As a result of the penetration test for the welded portion, almost no defects in the welded portion were observed in the weld metals No.1 to No.11. However, in weld metal No. 12, weld cracking occurred, and defects in the weld were observed.

  The weld metals No. 3 to No. 6 and No. 11 in which the segregation index P defined by 2Mo + 10V + 7 (Nb + Ta + Zr + Hf) (mass%) of the weld metal is 3 to 7 have a long fracture time of about 1100 hours. all right. In contrast, the weld metals No. 1 to No. 2 and No. 7 to No. 10 having a segregation index lower than 3 were found to have a short fracture time of 800 hours or less. Further, in the welding material No. 12 having a segregation index higher than 7, a weld crack occurred and the fracture time could not be measured. For this reason, the weld metal No. 12 is not shown in FIG.

  FIG. 5 shows an example of a divided structure rotor for a high-pressure turbine according to the present embodiment, and FIG. 6 shows an example of a divided structure rotor for a high-medium pressure turbine.

The divided structure rotor for a high-pressure turbine shown in FIG. 5 is divided into a front side paragraph 61, a rear side paragraph 62, and a shaft portion 63, which are high pressure parts. Then, the front paragraph 61 and the rear paragraph 62 are joined at the welded portion 66, and the rear paragraph 62 and the shaft portion 63 are joined at the welded portion 67.

  A hollow portion 64 is formed at a joint portion between the front paragraph 61 and the rear paragraph 62, and a hollow portion 65 is formed at a joint portion between the rear paragraph 62 and the shaft portion 63, so that weight reduction is achieved.

  In the case of such a rotor, the steam flows into the front paragraph 61 and then into the rear paragraph 62.

  The front paragraph 61 uses the high Cr steel material described in Table 1, and the rear paragraph 62 and the shaft 63 use the low Cr steel material shown in Table 1.

  Moreover, No. 11 of Table 2 was used for the weld metal.

That is, the chemical composition of the weld metal used is as follows: C: 0.10%, Si: 0.14%, Mn: 0.42%, P: 0.005%, S: 0.008%, Cu : 0.3%, Ni: 0.24%, Cr: 2.3%, Mo: 1.04%, V: 0.28%, Nb: 0.03%, and Ta:
It is 0.01%, and the balance is made of Fe.

  Welding was performed at a temperature between passes of 400 ° C. or less after preheating the joint to 250 ° C. to 300 ° C. After welding, the temperature was kept at 400 ° C., dehydrogenation treatment was performed, and the temperature was raised to 630 ° C. to remove residual stress.

  As a result of nondestructive inspection of the weld (magnetic particle inspection test, penetration inspection test, ultrasonic inspection test), no defects were detected and the welding result was good.

  The length of the shaft, the number of divisions, and the body diameter vary depending on the output and the rotational speed of the steam turbine, but similar welding joints are possible for various rotor shapes.

  FIG. 6 is divided into a front paragraph 71, a rear paragraph 72, and a rear paragraph 73, which are a high-pressure portion and an intermediate-pressure portion. The steam in such a rotor flows into the front paragraph 71 and then into the rear paragraph 72. Thereafter, the steam heated again by the reheater or the like flows into the front paragraph 71 and then into the rear paragraph 73.

The front paragraph 71 and the rear paragraph 72 are joined at the weld portion 76, and the front paragraph 71 and the rear paragraph 73 are joined at the weld portion 77.

A hollow portion 74 is formed at a joint portion between the front paragraph 71 and the rear paragraph 72, and a hollow portion 75 is formed at a joint portion between the front paragraph 71 and the rear paragraph 73, thereby reducing the weight.

  The front paragraph 71 uses the high Cr steel material described in Table 1, and the rear paragraph 72 and the rear paragraph 73 use the low Cr steel material shown in Table 1.

  Moreover, No. 11 of Table 2 was used for the weld metal.

  Welding was performed at a temperature between passes of 400 ° C. or less after preheating the joint to 250 ° C. to 300 ° C. After welding, the temperature was kept at 400 ° C., dehydrogenation treatment was performed, and the temperature was raised to 630 ° C. to remove residual stress.

  As a result of nondestructive inspection of the weld (magnetic particle inspection test, penetration inspection test, ultrasonic inspection test), no defects were detected and the welding result was good.

  The length of the shaft, the number of divisions, and the body diameter vary depending on the output and the rotational speed of the steam turbine, but similar welding joints are possible for various rotor shapes.

  According to the present embodiment, by providing a new weld metal, it is possible to provide a split structure type steam turbine welding rotor having good weld characteristics, and the steam temperature is a high temperature and high pressure, steam turbine power plant. Thus, a turbine welded rotor corresponding to higher efficiency and higher output capacity can be produced.

  Note that the split structure type steam turbine rotor described in the present embodiment can be hollowed by making it a welded structure, so that a hollow structure can be used, and an integral structure type using a solid structure Compared with the steam turbine rotor of, the weight can be reduced, and the thermal stress at the time of starting and stopping is small, so that it is not easily damaged by fatigue.

  Along with the weight reduction of the steam turbine rotor, thermal stress can be reduced, and the time required for starting and stopping can be shortened to improve operability.

  Moreover, the bearing part of a high Cr steel rotor carries out overlay welding of the low Cr steel material which is excellent in sliding characteristics from the viewpoint of ensuring sliding characteristics, or shrinks the ring of low Cr steel materials.

  According to this embodiment, even if the rotor blade implantation part must be made of a high Cr steel material, the bearing part can be made of a low Cr steel material, and no overlay welding or the like is required. It is.

  FIG. 7 shows an example of a steam turbine with an output of 600 MW. The rotor 30 is divided into a front paragraph 31, a rear paragraph 33, and a rear paragraph 35 of the high pressure portion and the intermediate pressure portion.

  The front paragraph 31 and the rear paragraph 33 are joined at the welded portion 32, and the front paragraph 31 and the rear paragraph 35 are joined at the welded portion 34.

  Moreover, No. 11 of Table 2 is used for a weld metal.

  The front paragraph 31 uses the high Cr steel material of Table 1, and the rear paragraph 33 and the rear paragraph 35 use the low Cr steel material of Table 1.

  Since the bearing portion 37 is made of a low Cr steel material, build-up welding or the like of the low Cr steel material for ensuring sliding characteristics is unnecessary.

  In the steam turbine shown in FIG. 7, steam having a steam temperature of 600 ° C. and a steam pressure of 25 MPa supplied from the boiler is guided to the high-pressure casing 18 through the main steam pipe 28. The steam guided to the high pressure casing 18 passes through the nozzle 38 and is guided to the high pressure blade group 16. Steam energy is converted into rotational energy by the high-pressure blade group 16, and the rotor 30 rotates.

  Further, the steam discharged from the high-pressure casing 18 is guided again to the intermediate pressure blade group 17 and contributes to the rotation of the rotor 30.

  As the rotor 30 rotates, power can be generated in the generator coupled to the rotor 30.

  The present invention relates to a steam turbine welding rotor and can be used in a power plant using a steam turbine.

The block diagram of a division structure rotor joint part. The expansion block diagram of a division structure rotor joint part. The figure which shows the hardness distribution of the welded joint part. The figure showing the fracture | rupture time based on a creep test result. The figure which shows an example of the division structure rotor for high pressure turbines. The figure which shows an example of the division structure rotor for high intermediate pressure turbines. The figure which shows an example of a steam turbine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High Cr steel rotor 2 Low Cr steel rotor 3 Raised part on the inner peripheral side of the rotor 4 Raised part 5 R (curved part) on the outer peripheral side of the rotor
6 groove 7 narrow groove

Claims (14)

A steam turbine welded rotor formed by welding at least a high Cr steel rotor and a low Cr steel rotor having a lower Cr content than the high Cr steel rotor,
The weld metal joining the high Cr steel rotor and the low Cr steel rotor is C: 0.05 to 0.15%, Si: 1% or less, Mn: 2% or less, P: 0.03% or less in mass%. , S: 0.03% or less, Cu: 0.5% or less, Ni: 0.5% or less, Cr: 1.0 to 3.5%, Mo: 0.4 to 1.2%, V: 0 0.05 to 0.4% and at least one of four types of Nb, Ta, Zr, and Hf is contained, the total is 0.01 to 0.1%, and the balance is Fe Steam turbine welding rotor.   2. The steam according to claim 1, wherein a welded portion between the high Cr steel rotor and the low Cr steel rotor is formed with a hollow at the center side of a surface crossing the shaft to form a narrow groove portion. Turbine welding rotor.   2. The steam turbine welded rotor according to claim 1, wherein a segregation index P defined by 2Mo + 10V + 7 (Nb + Ta + Zr + Hf) (mass%) of the weld metal is 3 to 7. 3.   The steam turbine welded rotor according to claim 1, wherein the high Cr steel rotor contains 8 to 13% Cr by mass.   The steam turbine welded rotor according to claim 1, wherein the low Cr steel rotor contains 0.8 to 2.5% Cr by mass.   The steam turbine welding rotor according to claim 1, wherein a difference in Cr content between the high Cr steel rotor and the low Cr steel rotor is 6% or more. A steam turbine welded rotor formed by welding at least a high Cr steel rotor and a low Cr steel rotor having a lower Cr content than the high Cr steel rotor,
2Mo + 10V + of weld metal that joins the high Cr steel rotor and the low Cr steel rotor
7. A steam turbine welded rotor having a segregation index P defined by 7 (Nb + Ta + Zr + Hf) (mass%) of 3 to 7.   The low Cr steel rotor is, by mass%, C: 0.15 to 0.40%, Si: 0.15% or less, Mn: 0.05 to 1.50%, Ni: 0.2 to 1.5. %, Cr: 0.8-1.5%, Mo: 0.8-1.8%, V: 0.1-0.3%, P: 0.012% or less, S: 0.015% or less The steam turbine welded rotor according to claim 1, wherein the balance is substantially made of Fe.   The high Cr steel rotor is, by mass%, C: 0.05 to 0.25%, Si: 0.15% or less, Mn: 1.00% or less, Ni: 0.75% or less, Cr: 9. 0 to 13.0%, Mo: 0.05 to 1.50%, W: 3.0% or less, V: 0.05 to 0.30%, Nb: 0.01 to 0.20%, Co: The steam according to claim 1, comprising 5.0% or less, N: 0.01 to 0.10%, B: 0.0001 to 0.030%, and the balance being substantially made of Fe. Turbine welding rotor. A rotor formed by welding at least a high Cr steel rotor and a low Cr steel rotor having a lower Cr content than the high Cr steel rotor;
A first rotor blade formed on the high Cr steel rotor; a second rotor blade formed on the low Cr steel rotor;
A stationary blade for directing steam to the first moving blade and the second moving blade;
A casing covering the first moving blade, the second moving blade, and the stationary blade;
A steam turbine having
The steam turbine, wherein the high Cr steel rotor and the low Cr steel rotor are joined together by one kind of weld metal.   11. The steam turbine according to claim 10, wherein a segregation index P defined by 2Mo + 10V + 7 (Nb + Ta + Zr + Hf) (mass%) of the weld metal is 3 to 7. 11.   The steam turbine according to claim 10, wherein the high Cr steel rotor and the low Cr steel rotor of the rotor are connected by butt welding with a center side of a surface crossing the shaft being hollow. The weld metal is, by mass%, C: 0.05 to 0.15%, Si: 1% or less, Mn: 2% or less, P: 0.03% or less, S: 0.03% or less, Cu: 0 0.5% or less, Ni: 0.5% or less,
Cr: 1.0 to 3.5%, Mo: 0.4 to 1.2%, V: 0.05 to 0.4%, and at least one of four types of Nb, Ta, Zr, and Hf The steam turbine according to claim 10, wherein the steam turbine is contained in an amount of 0.01 to 0.1%, and the balance is Fe. A steam turbine welded rotor formed by welding at least a high Cr steel rotor and a low Cr steel rotor having a lower Cr content than the high Cr steel rotor,
The steam turbine welded rotor, wherein the high Cr steel rotor and the low Cr steel rotor are joined by one kind of weld metal.

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