JP5003130B2 - Turbine rotor - Google Patents

Description

  The present invention relates to a turbine rotor having a highly reliable weld.

  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 large rotating body such as a steam turbine rotor, coupled with the development of forging heat treatment technology. 1% CrMoV steel (Non-patent Document 1) and 12% Cr steel (Patent Document 1) are used for high-pressure and medium-pressure steam turbines with steam temperatures of 538 to 600 ° C., and low pressures with steam temperatures of 400 ° C. or less. 3-4% Ni—Cr—Mo—V steel (Non-patent Document 2) is used for the steam turbine.

  Moreover, in order to reduce the weight of the turbine and simplify the structure, a high-low pressure integrated rotor integrally formed from the same material from high pressure to low pressure at a steam temperature of 538 to 566 ° C. is 2% Ni-2% Cr—Mo—. V-based steel (Patent Document 2) or the like is used, but is not suitable for further increase in temperature and capacity.

  The properties required for the rotor material are high temperature creep rupture strength at high pressure (high temperature), and tensile strength and toughness at low pressure. Thus, it is difficult for a steam turbine rotor to satisfy both high pressure and low pressure characteristics with a single material, and the required characteristics differ from one paragraph to another.

  A method is known in which an optimal material is selected for each paragraph or for each of a plurality of paragraphs, and a single rotor is formed by bolt fastening, welding joining, or the like.

  Moreover, there is Patent Document 3 as a method of joining different materials at the time of remelting in the manufacturing process. Small steel ingots such as every paragraph or every plurality of paragraphs are easy to obtain high-quality steel ingots compared to the production of large rotors, and do not require large-scale production equipment.

  In the conventional turbine rotor welding method, a hole for back shield injection is provided in advance in the groove bottom (Non-patent Document 4), and a hole is provided in the center hole of the turbine rotor from the periphery of the weld (patent) Reference 4).

Japanese Patent No. 1833108 Japanese Patent No. 3106121 Japanese Patent Publication No. 56-14842 JP 2000-64805 A ASTM A470 Class8 ASTM A470 Class7 Mitsubishi Heavy Industries Technical Review, Vol.37, No.3 (2000-5) Fuji Times Vol.77, No.2 (2004)

  In order to reduce the load applied to the turbine rotor at the time of starting and stopping the plant, the turbine rotor is provided with a center hole. When welding the turbine rotor, first, the bottom of the butt portion that is grooved on the turbine rotor is welded. In the first layer, it is necessary to completely melt the groove bottom and to penetrate to the inner periphery of the turbine rotor. In general butt welding, when the first layer is penetrated to the back surface of the plate, an inert gas is injected from the back side of the groove bottom portion to be welded in order to suppress oxidation of the surface of the weld bead.

  However, the center hole of the turbine rotor is closed by abutting the turbine rotor during welding. Therefore, the inert gas cannot be injected into the center hole of the turbine rotor from the back side of the groove bottom. For this reason, the inner peripheral side of the turbine rotor in the first layer is excessively oxidized, and surface roughness is generated as a starting point of crack propagation. Furthermore, since the weld bead on the inner periphery of the turbine rotor cannot be observed, the possibility of crack propagation cannot be determined.

  Moreover, the hole provided in the turbine rotor which is a rotary body is unpreferable on intensity | strength. This is because the hole may become a stress concentration. Accordingly, it is necessary to provide a highly reliable turbine rotor that does not have a strength reduction origin.

  An object of the present invention is to provide a turbine rotor having no defect that causes a decrease in strength in a welded part in an environment where a back shield cannot be used.

  The turbine rotor of the present invention has a center hole in which a turbine rotor divided into at least two parts is connected via a welded portion by butt welding, and the welded portion has a C content of 0.1 to 0.2% by mass, 0.1 to 0.3 mass% of Si, 0.3 to 0.7 mass% of Mn, 0.2 to 2.3 mass% of Ni, 1.7 to 4.8 mass% of Cr, Mo It has at least a steel material composed of 0.4 to 1.1 mass% and Fe as the balance.

  Further, the turbine rotor has a C content of 0.17 to 0.32 mass%, a Mn content of 0.20 to 0.40 mass%, a Ni content of 3 to 4 mass%, a Cr content of 1.25 to 2.0 mass%, Ni-Cr-Mo-V based steel having a bainite structure composed of 0.24 to 0.6% by mass of Mo, 0.05 to 0.15% by mass of V, and the balance as Fe is preferable. .

  Further, the welded portion is 0.1 to 0.2% by mass of C, 0.1 to 0.3% by mass of Si, 0.3 to 0.7% by mass of Mn, and 0.3 to 2.3% by mass of Ni. %, Cr is 1.9 to 4.8% by mass, Mo is 0.4 to 1.0% by mass, and the balance is preferably at least a steel material composed of Fe.

Further, the turbine rotor has a C content of 0.17 to 0.32 mass%, a Mn content of 0.20 to 0.40 mass%, a Ni content of 3 to 4 mass%, a Cr content of 1.25 to 2.0 mass%, Ni-Cr-Mo-V based steel having a bainite structure composed of 0.24 to 0.6% by mass of Mo, 0.05 to 0.15% by mass of V, and Fe as the balance; .25 to 0.35 mass%, Mn 1 mass% or less, Ni 1 mass% or less, Cr 0.8 to 1.5 mass%, Mo 1.0 to 1.5 mass%, and V 0.2 -0.3 mass%, and Cr- having a bainite structure composed of Fe as the balance
A combination with Mo-V steel is preferable.

In this case, the weld zone is 0.1 to 0.2% by mass of C, 0.1 to 0.3% by mass of Si, 0.4 to 0.7% by mass of Mn, 0.2 to 1% of Ni. It is preferable to have at least a steel material composed of 0.3 mass%, Cr 1.7-4.8 mass%, Mo 0.6-1.1 mass%, and the balance Fe.

  Further, the welded portion has a C content of 0.03 to 0.3% by mass, Si of 0.06 to 0.3% by mass, Mn of 0.6 to 1.7% by mass, Ni on the outer periphery of the steel material. 2.2 to 3.6% by mass of Cr, 0.4 to 1.6% by mass of Cr, 0.4 to 1.1% by mass of Mo, and the second steel material composed of Fe as the balance Is preferred.

  In the turbine rotor of the present invention, the welded portion is composed of at least two regions having different chemical components, and the chemical component in the first region located on the inner peripheral side of the welded portion has C of 0.1 to 0.00. 2 mass%, Si 0.1-0.3 mass%, Mn 0.3-0.7 mass%, Ni 0.2-2.3 mass%, Cr 1.7-4.8 mass% %, Mo is 0.4 to 1.1% by mass, and the balance is Fe, and the chemical component of the second region located on the outer peripheral side of the weld zone is C. 3 mass%, Si 0.06-0.3 mass%, Mn 0.6-1.7 mass%, Ni 2.2-3.6 mass%, Cr 0.4-1.6 mass% %, Mo is 0.4 to 1.1% by mass, and the balance is preferably made of steel composed of Fe.

Further, in the present invention, in a turbine rotor having a center hole in which a turbine rotor divided into at least two parts is connected via a welded portion by butt welding, the welded portion has a C of 0.04 to 0.04.
0.22 mass%, Si 0.08-0.46 mass%, Mn 0.3-1.05 mass%, Ni 0.15-2.3 mass%, and Cr 1.8-5. It is characterized by including at least a steel material composed of 0% by mass, Mo of 0.4 to 1.1% by mass, and the balance being Fe.

  Further, the turbine rotor has a C content of 0.17 to 0.32 mass%, a Mn content of 0.20 to 0.40 mass%, a Ni content of 3 to 4 mass%, a Cr content of 1.25 to 2.0 mass%, In the case of a 3-4 mass% Ni—Cr—Mo—V steel having a bainite structure containing 0.24 to 0.6 mass% of Mo and 0.05 to 0.15 mass% of V, the weld is made of C. 0.05 to 0.20 mass%, Si is 0.08 to 0.46 mass%, Mn is 0.3 to 1.1 mass%, Ni is 0.3 to 2.3 mass%, and Cr is 2. It is desirable that the steel material is 0 to 2.3 mass%, Mo is 0.6 to 1.01 mass%, and the balance is Fe.

Moreover, the combination of turbine rotors is 0.17 to 0.32% by mass of C, 0.20 to Mn.
0.40 mass%, Ni 3-4 mass%, Cr 1.25-2.0 mass%, Mo 0.24-
0.6 to 4% by mass, 3 to 4% by mass having a bainite structure containing 0.05 to 0.15% by mass of V
Ni-Cr-Mo-V steel and C0.25-0.35 mass%, Mn 1 mass% or less, Ni 1 mass% or less, Cr 0.8-1.5 mass%, Mo 1. In the case of a 1 mass% Cr-Mo-V steel having a bainite structure containing 0 to 1.5 mass% and V of 0.2 to 0.3 mass%, the weld zone has a C content of 0.05 to 0.25. Mass%, Si 0.08-0.46 mass%, Mn 0.4-1.1 mass%, Ni 0.2-1.3 mass%, Cr 1.8-2.3 mass%. It is desirable that the steel material be composed of 0.9 to 1.1 mass% of Mo and Fe as the balance.

  The turbine rotor has a C content of 0.05 to 0.25 mass%, a Si content of 0.08 to 0.46 mass%, a Mn content of 0.3 to 1.05 mass%, and a Ni content of 0.2 to 2.2. It is desirable to have a butt portion made up of a steel material composed of 3% by mass, Cr of 1.8 to 2.3% by mass, Mo of 0.6 to 1.1% by mass and the balance of Fe.

  Further, the welded portion is composed of at least two regions having different chemical components, and the chemical components in the first region located on the inner peripheral side of the turbine rotor are 0.04 to 0.22% by mass of C and 0.08 of Si. ~ 0.46 mass%, Mn 0.3 to 1.05 mass%, Ni 0.15 to 2.3 mass%, Cr 1.8 to 5.0 mass%, Mo 0.4 to 1 It is desirable that the steel material be composed of 0.1% by mass and the balance being Fe.

  Moreover, as for the 1st area | region, it is desirable for the height of a 1st area | region to be 5 mm or more and the height of a protruding part.

In the second region, the chemical components of the second region are 0.03 to 0.21% by mass of C, 0.05 to 0.3% by mass of Si, 0.6 to 1.5% by mass of Mn, Ni 2.2 to 3.6 mass%, Cr is 0.4 to
It is desirable that the steel material is composed of 1.6 mass%, Mo is 0.4 to 1.0 mass%, and the balance is Fe.

  ADVANTAGE OF THE INVENTION According to this invention, the turbine rotor containing the weld part without a defect can be provided in the construction environment which cannot use a back shield.

  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.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a welding rotor for a low-pressure double-flow steam turbine according to the present invention. This welding rotor for a low-pressure double-flow steam turbine has a structure in which six stages of turbine rotor blades are implanted symmetrically, and is a double-flow type in which steam flows from the center to the left and right. In the present embodiment, the final stage rotors 31 and 33 having journal portions in which the final stage turbine rotor blades are implanted on both sides of the central steam inflow side rotor 32 in which turbine blades other than the final stage are implanted. However, it has the structure weld-joined by the welding parts 36 and 37, respectively.

  The structure of the welded portion of this embodiment is provided with hollow portions 34 and 35 to reduce the weight. Further, both the steam inflow side rotor 32 and the final stage side rotors 31 and 33 were made of 3 to 4% Ni—Cr—Mo—V steel shown in Table 1 and joined through welds 36 and 37. The welding rotor for a steam turbine according to this embodiment is solid except for the hollow portions 34 and 35.

  FIG. 2: is the fragmentary sectional view (a) which shows the welding part which concerns on this invention, and the fragmentary sectional view (b) which shows a welding part. The two turbine rotors 1 and 2 are joined via a weld. The welded portion 3 is provided at the end of the turbine rotor to be welded. A butting portion 4 is provided at the bottom of the groove portion in order to align with the other turbine rotor. A welded portion is formed on the outer side from the central portion of the groove portion by melting the welding wire.

FIG. 3 is a schematic diagram showing a turbine rotor welding apparatus. Here, the tungsten / inert gas welding method is illustrated. The turbine rotor welding apparatus 8 includes a torch 10 to which an electrode 9 is attached, a welding wire 11 that forms a weld, an arm 12 that supports and fixes the torch 10 and the welding wire 11, and a welding power source 13 that supplies a predetermined current to the electrode 9. In order to suppress oxidation of the welded portion, a gas cylinder 14 for supplying an inert gas injected from around the electrode 9, a turbine rotor rotating device 15 for rotating the turbine rotor 1 while supporting it, and a welding wire 11 are sent to the welded portion. A welding wire feeding device 16 for feeding is provided. A power transmission line 17 is attached to the electrode 9 in order to receive a current supply from the welding power source 13. A gas hose 18 is attached to the torch 10 in order to receive an inert gas from the gas cylinder 14. An electric wire 19 is attached to the turbine rotor 1 in order to generate an electric arc between the electrode 9 and the turbine rotor 1. A rotation signal line 20 is attached to the turbine rotor rotating device 15 in order to receive control signals for the rotation speed and rotation direction from the welding power source 13. The welding wire feeding device 16 is provided with a feeding signal line 21 for receiving a control signal of the feeding speed of the welding wire 11 . In the present invention, in addition to the illustrated tungsten / inert gas welding method, a submerged arc welding method, a covering arc welding method, a metal / inert gas welding method, and a combination thereof can be employed.

  FIG. 4 is an example of a turbine rotor welding process flow in the present invention. First, when an instruction to start the welding process is issued (S101), the turbine rotor is preheated to relieve the thermal stress during welding (S102). And a welding wire is attached to a welding apparatus (S103). The degree of excessive oxidation on the surface of the welded portion varies depending on the type (element component) of the wire to be welded. Therefore, as a preliminary test, welding was performed using welding wires having different elemental components, and the surface morphology was observed. Table 2 shows the welding conditions in the preliminary test, and Table 3 shows the elemental components of the welding wire used and the results of observation of excess oxidation.

  As a result of the preliminary test, it was found that when the welding wires No. 4 and No. 5 were used, excessive oxidation of the back surface of the welded portion did not occur. The weld is composed of a mixed phase of a welding wire component and a base material component. Therefore, the excessive oxidation occurrence form of the weld is determined not only by the welding wire element component but also by mixing with the base material element component.

Based on these findings, the element component range of the turbine rotor weld that does not generate excessive oxidation was examined. Relational expressions (1) to chemical composition and volume of welds, base metal and welding wire
Formula (4) was derived based on (3).
C _p V _p = C _s V _s + C _w V _w Formula (1)
_{V p = V s + V w} = 100 formula (2)
R = V _s / V _p formula (3)
_{C p = C w + (C} s -C w) R (4)
Here, C is the chemical composition concentration, and V is the volume ratio in the weld. The subscript p is a welded portion, s is a turbine rotor, and w is a welding wire. R is a dilution ratio defined by the equation (3), and is a volume ratio of the rotor base material in the welded portion. The dilution ratio R of the welds manufactured under the welding conditions shown in Table 2 was about 10%. From this, when the chemical composition of the welded part when using the welding wire 4 is obtained based on the formula (4), C is 0.1% by mass, Si is 0.3% by mass, and Mn is 0.7% by mass. %, Ni was 0.4% by mass, Cr was 2.2% by mass, Mo was 1.0% by mass, and the balance was Fe. C has a quenching effect, Si has a deoxidation effect, Mn has a desulfurization / deoxidation effect, Ni has a quenching effect, Cr has an oxidation inhibiting effect, and Mo has a tempering embrittlement preventing effect. In addition to the effect of suppressing the oxidation of Cr, the excessive oxidation of the weld could be suppressed by the synergistic effect of these elements.

Next, after welding (S104), post-heat treatment is performed in order to equalize the heat that has locally entered only around the weld (S105) . Further, the inside of the weld is inspected in order to confirm the presence or absence of defects due to poor penetration or poor gas discharge during welding (S106) . A defect is detected in the weld and the defect size is estimated (S108). If the mechanical strength is not acceptable, the welded portion including the defective portion is removed (S109), and the removed welded portion is welded again (S104). When no defect is detected in the welded portion and when the detected defect is acceptable, stress removal annealing is performed to remove the residual stress that has entered the welded portion (S110), and the joining process is terminated (S111). .

  As described above, by limiting the chemical composition of the welded portion, excessive oxidation of the welded portion can be suppressed in a construction environment where the back shield cannot be used.

A second embodiment of the present invention will be described with reference to FIG. The welding apparatus and the procedure of the welding process are the same as in the first embodiment (FIGS. 3 and 4). The structure and steel type of the turbine rotor are the same as those in the first embodiment (FIG. 1 and Table 1). This example differs from the first example (Table 2) only in welding conditions. Since the amount of penetration of the base material varies depending on the welding conditions, the dilution rate R changes. Table 4 shows examples of welding conditions and dilution rate measurement results used in this example. The welding wire used is the same as that in the first embodiment (Table 3).

  As a result of producing a weld using the welding wire of Table 3 according to the welding conditions of Table 4, excessive oxidation did not occur only when the welding wires No. 4 and 5 were used as in the first example. From this, it was found that the chemical composition of the weld that does not cause excessive oxidation is not a single combination but a combination within a certain range. Based on the above results, the chemical composition in the weld was determined. The calculation was based on the same formula (4) as in the first example.

  FIG. 5 shows the influence of the material composition of the welding wire on the chemical composition in the weld. Here, although the figure about Cr is shown as a typical example of an element, it can calculate similarly about C, Si, Mn, Ni, and Mo. It was found that the Cr content in the welded portion produced using the welding wires 4 and 5 and not causing excessive oxidation was 1.9 to 4.8% by mass. Cr is an element that easily oxidizes. Since the weld includes Cr, a chromium oxide layer is formed on the surface of the weld. The chromium oxide layer is a stable passivation and does not oxidize further. Thereby, oxidation does not advance in the welded part itself. When the Cr content in the weld zone is less than 1.8% by mass, the oxidation of the weld zone by Cr is not sufficient. As a result, the weld is oxidized, and as a result, excessive oxidation occurs. The weld is formed by obtaining a process of solidifying from the liquid phase to the solid phase. The welded portion in the liquid phase is internally stirred as the arc fluctuates and the electrodes are scanned. Therefore, the chromium oxide layer formed on the surface of the welded portion is stirred in the welded portion. As a result, the chromium oxide layer is continuously formed on the surface of the welded portion in the liquid phase, and chromium oxide is contained inside the welded portion. Therefore, when the Cr content in the weld is greater than 5.0% by mass, the amount of chromium oxide in the weld is too much to be ignored with respect to the excessive oxidation, and excessive oxidation occurs. Other elements also have an upper limit and a lower limit, although their effects on excess oxidation are different. As a result of calculating the composition of the welded portion that does not cause excessive oxidation like Cr, C is 0.1 to 0.2 mass%, Si is 0.1 to 0.3 mass%, and Mn is 0.3 to 0.3 mass%. 7 mass%, Ni was 0.3 to 2.3 mass%, and Mo was 0.4 to 1.0 mass%. C is an element that improves hardenability. If the amount is 0.1% by mass or less, sufficient hardenability cannot be obtained.

  Moreover, since it will reduce toughness when it becomes 0.2 mass% or more, the range of C is limited to 0.1-0.2 mass%. Si is a deoxidizing agent, and Mn is a desulfurizing / deoxidizing agent, which is added when the steel is melted. Therefore, in order to obtain a sufficient deoxidizing effect, Si needs to be 0.1% by mass or more.

However, since Si has the property of being more easily combined with O than Fe, it forms SiO ₂ and decreases weldability. Therefore, Si is made 0.3 mass% or less. Appropriate amount of Mn is added as an impurity element in the steel and has an effect of fixing harmful S which deteriorates hot workability as sulfide MnS. For this reason, the addition of an appropriate amount of Mn has the effect of reducing the above-mentioned harm of S. Therefore, in the production of a large forged product such as a rotor shaft for a steam turbine, it should be 0.3% by mass or more.

  On the other hand, if added in a large amount, creep embrittlement tends to occur and the notch weakens, so the content is made 0.7 mass% or less. Ni is an element that improves hardenability and is essential for improving toughness. When Ni is less than 0.3% by mass, the effect of improving toughness is not sufficient. Further, addition of a large amount exceeding 2.3% by mass reduces the creep rupture strength. 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 the amount is less than 0.4% by mass, these effects are not sufficient, and a large amount of addition exceeding 1.0% by mass reduces toughness.

  For these reasons, the welded portion that does not cause excessive oxidation can be formed by selecting the welding wire so that the chemical composition of the welded portion falls within the above range.

A third embodiment of the present invention will be described with reference to FIGS. The steel type combination of the turbine rotor 1 and the turbine rotor 2 may weld a different type of steel from the case of welding the same type of steel shown in Examples 1 and 2 depending on the use of the turbine rotor. The former is used when a small steel ingot is welded to a steel type that is difficult to produce a large steel ingot and used as a large steel ingot. The latter is used when different steel types are used depending on the parts with different steam conditions such as pressure and temperature. In the third embodiment, the case where the latter dissimilar material is welded will be described. Table 5 shows the chemical composition of these steel types. FIG. 6 is a cross-sectional view of a welding rotor for a high / low pressure integrated turbine according to the present invention. It was divided into a high temperature side rotor 38 and a low temperature side rotor 39 and joined at the hollow portion 34. The structure of the welded portion is the same as that of the first embodiment, and the joint portion forms the final stage rotor 33 to reduce the weight. The high temperature side rotor 38 is made of 1% CrMoV steel shown in Table 5, and the low temperature side rotor 39 is made of 3-4% NiCrMoV steel shown in Table 5. The welding apparatus used in this embodiment and the procedure of the welding process are the same as in the first embodiment (FIGS. 3 and 4), and only the chemical components of the welding wire used and the weld formed by welding are different.

As described in the first embodiment, the chemical composition of the weld is determined by the chemical composition and dilution ratio of the base material and the welding wire. Since the chemical compositions of the two base materials are different, the chemical composition of the weld is determined by the formula (8) from the relational expressions (5) to (7).
C _p V _p = C _s1 V _s1 + C _s2 V _s2 + C _w V _w formula (5)
_{V p = V s1 + V s2} + V w = 100 Equation (6)
R = (V _s + V _s2 ) / V _p formula (7)
_{C p = C w + (C} s -C w) R (8)
Here, the subscript s1 is the turbine rotor 1, and s2 is the turbine rotor 2. FIG. 8 shows the influence of the material composition of the welding wire on the chemical composition in the weld. Here, although the figure about Cr is shown as a typical example of an element, it can calculate similarly about C, Si, Mn, Ni, and Mo. Here, it was assumed that the base metal penetration amount during welding was the same (V ₁ = V ₂ ). It was found that the Cr content in the weld zone where no excessive oxidation occurred was 1.7 to 4.8% by mass. As a result of calculating the composition of the welded portion that does not cause excessive oxidation like Cr, C is 0.1 to 0.2% by mass, Si is 0.1 to 0.3% by mass, and Mn is 0.4 to 0.3%. 7 mass%, Ni was 0.2 to 1.3 mass%, Mo was 0.6 to 1.1 mass%, and the balance was Fe. This chemical composition range is different from that shown in the second embodiment. In the second example, the Ni content in the weld is less than in the first example. Therefore, since the toughness of the welded portion is relatively low, the welded portion is easily cracked. In order to cover this influence, the chemical composition of other elements is different from that of the first embodiment.

  As described above, by adjusting the chemical composition range of the welded portion by combining the turbine rotor steel types, it is possible to suppress excessive oxidation of the welded portion in a construction environment where the back shield cannot be used.

  A fourth embodiment of the present invention will be described with reference to FIGS. The welding apparatus used is the same as that in the first embodiment (FIG. 3). The structure and steel type of the turbine rotor are the same as in the first to third embodiments (FIGS. 1 and 1 and FIGS. 6 and 5). In this embodiment, the chemical composition of the welded portion is classified into at least two stages in the height direction of the welded portion. This point is different from the first and second embodiments. In this embodiment, the bottom of the welded portion is defined as a first region, and the upper portion of the welded portion is defined as a second region.

  FIG. 9 is an example of a turbine rotor welding process flow in the present invention, and FIG. 10 is an example of a schematic view of a turbine rotor weld in the turbine rotor welding process. First, when an instruction to start a welding process is issued (S201), the turbine rotor is preheated to relieve thermal stress during welding (S202). Then, a welding wire suitable for forming the first region is attached to the welding apparatus (S203). The turbine rotor at the end of S203 is fixed as shown in (1) of FIG. Here, the welding wire for the first region is selected according to the procedure described in the first to third embodiments. That is, the welding wire is selected so that the welded portion that does not generate excessive oxidation satisfies the chemical composition.

Next, the first region is welded (S204). The turbine rotor at the end of S204 is as shown in (2) of FIG. After the first region welding, the first region welding wire is removed (S205), and the second region welding wire is attached (S206). The first region welding wire is suitable for suppressing excessive oxidation, but does not have the mechanical strength necessary for actual operation.

  11 shows the tensile strength of the welding wire No. and the weld metal. The welding wire No. has the chemical composition shown in Table 3. The tensile strength is shown as a relative value to the tensile strength required for the turbine rotor during actual operation. From FIG. 11, when the welding wires No. 4 and 5 suitable for suppressing excessive oxidation are used, the welded portion cannot secure the strength required for actual machine operation.

  On the other hand, when the welding wires No. 6 to 9 are used, although the welded portion is excessively oxidized, the strength necessary for the actual machine operation can be ensured. Therefore, the second region is welded using a welding wire that places importance on the strength of the welded portion, with the portion to be welded without using the back shield originally (S207).

FIG. 12 shows details of (2) in FIG. In FIG. 12, h ₁ is the first region thickness, and h ₀ is the height of the raised portion. The raised portion is a portion provided on the inner peripheral side of the rotor in order to relieve stress concentration on the welded portion. As a preliminary experiment, a welded portion in which the thickness of the first region was changed was formed.

  As a result, as shown in FIG. 12 (1), when the thickness of the first region was 5 mm or less, the molten pool generated during the second region welding to be laminated on the first region penetrated the first region. Thereby, excessive oxidation occurred on the inner peripheral side of the welding rotor in the first region.

  On the other hand, as shown in FIG. 12 (3), when the thickness of the first region is equal to or higher than the height of the raised portion, the strength of the entire welded portion is reduced. This is because the first region having a low strength reduces the strength of the welded portion due to an increase in the volume ratio between the first region and the entire welded portion.

  Therefore, the thickness of the first region is desirably in the range of 5 mm to the height of the raised portion as shown in FIG. In this embodiment, the example in which the welded portion is classified into two regions has been described. However, the welded portion may be classified into three or more regions.

  The chemical components in the second region are 0.03 to 0.21 mass% for C, 0.05 to 0.3 mass% for Si, 0.6 to 1.5 mass% for Mn, and 2.0 for Ni. It is desirable to be 2 to 3.6 mass%, Cr is 0.4 to 1.6 mass%, Mo is 0.4 to 1.0 mass%, and the balance is Fe.

  The turbine rotor at the end of S207 is as shown in (3) of FIG. Thereafter, post-heat treatment is performed in order to uniformize the heat that is locally entered only around the welded portion (S208). Furthermore, the inside of the welded portion is inspected to confirm the presence or absence of defects due to poor penetration or poor gas discharge during welding (S209). When a defect is detected in the welded part (S210) and the defect size is not acceptable in mechanical strength (S211), the welded part including the defective part is removed (S212), and the removed welded part is welded again. Note that (S204, S207). If no defect is detected in the weld and if the detected defect is acceptable, stress removal annealing is performed to remove the residual stress that has entered the weld (S213), and the joining process is terminated (S114). .

  As described above, the reliability of the turbine rotor can be improved by classifying the chemical composition of the welded portion into two or more regions and setting the chemical composition according to each region.

  A fifth embodiment of the present invention will be described with reference to FIGS. In Examples 1 to 4, the rotor surface is ground into a predetermined shape to produce a butt portion. On the other hand, in this embodiment, the protruding portion is manufactured by overlaying with a material composition that does not cause excessive oxidation in advance. The apparatus used is the same as in the first to third embodiments (FIG. 3). The structure and steel type of the turbine rotor are the same as those in the first and second embodiments (FIGS. 1 and 1 and FIGS. 6 and 5).

  FIG. 13 is an example of a turbine rotor welding process flow according to the present invention, and FIG. 14 is an example of a schematic view of a section of a turbine rotor butt section in each work step.

First, overlaying is performed on the groove bottom in a state where there is no butt portion as shown in FIG. 14 (1) (S301), and a butt portion as shown in FIG. 14 (2) is manufactured. In addition to the tungsten / inert gas welding method, the overlay uses a submerged arc welding method, a covering arc welding method, a metal / inert gas welding method, a plasma powder cladding method and a plasma spraying method.

  Then, groove processing is performed on the butt portion in a predetermined shape (S302), resulting in the state shown in FIG. 14 (3). When an instruction to start the welding process is issued (S303), the turbine rotor is preheated to relieve the thermal stress during welding (S304). Then, the first region is welded. In the present embodiment, the first region corresponds to a butt portion. In the welding of the first region, the butt portion is melted by arc heat without using a welding wire. This is to prevent the chemical composition of the first region from deviating from the excessive oxidation suppression range due to dilution of the welding wire.

The turbine rotor at the end of S305 is as shown in FIG. 14 (4). After finishing the welding of the first region, a welding wire for the second region is attached to the welding apparatus (S306), and the second region is welded (S307). The turbine rotor at the end of S305 is as shown in FIG. Thereafter, post-heat treatment is performed in order to uniformize the heat locally entered only around the welded portion (S308). Further, in order to confirm the presence or absence of defects due to poor penetration or gas discharge during welding, the inside of the welded portion is inspected (S309). When a defect is detected in the welded part (S310) and the defect size is not acceptable in mechanical strength (S311), the welded part including the defective part is removed (S3121), and the removed welded part is welded again. The correction is made (S306). When no defect is detected in the welded portion and when the detected defect is acceptable, stress removal annealing is performed to remove the residual stress that has entered the welded portion (S313), and the joining process is terminated (S314). .

  As described above, according to the present invention, it is possible to eliminate the work of replacing the welding wire and perform welding without excessive oxidation of the first region in a construction environment where the back shield cannot be used.

It is sectional drawing of the welding rotor for low pressure double flow turbines concerning this invention. It is the fragmentary sectional view (a) which shows the whole structure of the turbine rotor which concerns on 1st Example of this invention, The fragmentary sectional view (b) which shows a coupling part. It is a mimetic diagram showing the turbine rotor welding device concerning the 1st example of the present invention. It is a flow which shows the turbine rotor welding process which concerns on 1st Example of this invention. It is a figure which shows the chemical composition calculation result example which does not weld based on the 2nd Example of this invention. It is sectional drawing of the welding rotor for high-low pressure integrated steam turbines based on this invention. It is a schematic diagram of the turbine rotor which concerns on the 3rd Example of this invention. It is a figure which shows the chemical composition calculation result example which does not weld based on the 3rd Example of this invention. It is a flow which shows the turbine rotor welding process which concerns on the 4th Example of this invention. It is an example of the schematic diagram of the turbine rotor butt | matching part cross section which concerns on the 4th Example of this invention. It is a figure which shows the example of the tensile strength of the welding part which concerns on the 4th Example of this invention. It is an example of the schematic diagram which shows the height of the 1st area | region which concerns on the 4th Example of this invention. It is an example of a turbine rotor welding process flow concerning the 5th example of the present invention. It is an example of the schematic diagram of the turbine rotor butt | matching part cross section which concerns on the 5th Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Turbine rotors 3, 36, 37 Welding part 4 Butting part 5 1st area | region 6 2nd area | region 7 Overlaying part 8 Turbine rotor welding apparatus 9 Electrode 10 Torch 11, 22 Welding wire 12 Arm 13 Welding power supply 14 Gas cylinder 15 Turbine Rotor rotator 16 Welding wire feeder 17 Transmission line 18 Gas hose 19 Electrical line 20 Rotation signal line 21 Feed signal line 31, 33 Final stage rotor 32 Steam inlet side rotors 34, 35 Hollow part 38 High temperature side rotor 39 Low temperature side Rotor

Claims (3)

In a turbine rotor having a center hole in which a turbine rotor divided into at least two parts is connected via a weld by butt welding,
The weld is composed of at least two regions having different chemical components,
The chemical component of the first region located on the inner peripheral side of the weld is
C is 0.1 to 0.2 mass%, Si is 0.1 to 0.3 mass%, Mn is 0.3 to 0.7 mass%, Ni is 0.3 to 2.3 mass%, Cr is 1.9 to 4.8% by mass, Mo is 0.4 to 1.0% by mass, and the steel material composed of Fe as the balance (provided that the turbine rotor is 3 to 4% NiCrMoV steel), or
C is 0.1 to 0.2 mass%, Si is 0.1 to 0.3 mass%, Mn is 0.4 to 0.7 mass%, Ni is 0.2 to 1.3 mass%, Cr is 1.7 to 4.8% by mass, Mo is 0.6 to 1.1% by mass, and the balance is Fe steel (provided that the turbine rotor is made of 3 to 4% NiCrMoV steel and 1% CrMoV steel) If)
The chemical composition of the second region located on the outer peripheral side of the welded portion is 0.03 to 0.21 mass% for C, 0.05 to 0.3 mass% for Si, and 0.6 to 1.5 for Mn. It is made of a steel material composed of 0.2% to 3.6% by mass of Ni, 0.4 to 1.6% by mass of Cr, 0.4 to 1.0% by mass of Mo, and Fe as the balance. Turbine rotor characterized by this. The turbine rotor of the 3-4% NiCrMoV steel according to claim 1, wherein C is 0.24 mass%, Si is 0.04 mass%, Mn is 0.27 mass%, Ni is 3.71 mass%, Cr Is 1.83 mass%, Mo is 0.36 mass%, V is 0.08 mass%, and the balance is Fe. In claim 1, the turbine rotor of the 3-4% NiCrMoV steel and 1% CrMoV steel,
3-4% NiCrMoV steel turbine rotor, C is 0.24 mass%, Si is 0.04 mass%, Mn is 0.27 mass%, Ni is 3.71 mass%, Cr is 1.83 mass% Mo is 0.36% by mass, V is 0.08% by mass and the balance is Fe.
1% CrMoV steel is 0.29% by mass of C, 0.04% by mass of Si, 0.77% by mass of Mn, 0.52% by mass of Ni, 1.13% by mass of Cr and 1.1% of Mo. A turbine rotor comprising 353 mass%, V being 0.27 mass%, and the balance being Fe.

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