Blading for a steam turbine of a combined cycle power generation system

Abstract: Blades for a steam turbine of a combined cycle power system where the high and low presure part are integrated into one single stage. The blades are made of a martensite steel including 8-13 wt% Cr, having blade length of 33 inches or more for 60Hz power generation and 40 inches for 50Hz power generation.

Description: The present invention relates to a high and low pressure integral steam turbine using the long blades according to the preamble of claim 1. At present, 12Cr-Mo-Ni-V-N steel is used for steam turbine blades. In recent years, it is desired to raise the thermal efficiency of a fossil fuel power plant in view of energy-saving, and make apparatuses used therefore compact in view of space-saving. Elongation of the turbine blades is an effective means for improving the thermal efficiency and making the apparatuses compact. Therefore, the length of blades of the final stage tends to be increased year by year. Thereby, the conditions that the steam turbine blades are used also becomes severe, a conventional 12Cr-Mo-Ni-V-N steel can not provide turbine blades having sufficient strength. Therefore, a stronger material is necessary. As the strength of material for long blades, tensile strength, which is a base of mechanical property, is required. Further, toughness also is required in view of securing safety against rupture. As a structural material having a higher tensile strength than the conventional 12Cr-Mo-Ni-V-N steel (martensite steel), a Ni-base alloy and Co-base alloy are known well, however, they are not enough in hot workability, machine-cutting property and vibration-attenuating property, so that they are not desirable. Material for gas turbine discs is disclosed in JP A 63-171856, however, it does not have a high tensile strength. Further, so-called integral turbine, which is a high pressure side and a low pressure side are integrated into one unit in view of space-saving in turbines of a small capacity less than 100,000 kW and a middle capacity of from 100,000 to 300,000 kW, has been put into practice. The length of final stage blades of this integral turbine is 33.5 inches at most because the strength of material for rotor and blade is limited. The blade length, however, is desired to be further elongated in order to increase a turbine output. JP A 3-130502 discloses blades for high and low pressure sides-integrated steam turbines, using 12% Cr steels. However, the steel is too low in tensile strength to provide long blades of recent low pressure steam turbines. EP 0 384 181 A2 discloses a high and low pessure sides integrating steam turbine comprising a rotor having a mono-block rotor shaft on which blades are planted in multi-stages from a high pressure side to a low pressure side. The inlet temperature of steam is 530°C. The final stage blades on the low pressure side having a length not less than 101.6 cm are fabricated from Ti alloy containing 5 to 7% Al and 3 to 5% V. SUMMARY OF THE INVENTION An object of the invention is to provide a high and low pressure side-integrating steam turbine, having blades using martensite steel having a high tensile strength. This object ist obtained by a high and low pressure sides integrating steam turbine comprising the features of claim 1. Prefered embodiments of the high and low pressure sides integrating steam turbine are the subject matters of claims 2 to 10. (1) The reasons for limiting components of long blade material for high and low pressure sides-integrating steam turbines: The present invention resides in long blades for a high and low pressure sides-integrating steam turbine, each made of a martensite stainless steel comprising, by weight percentage, 0.08-0.18% C, not more than 0.25% Si, not more than 0.9% Mn, 8.0-13.0% Cr, 2-3% Ni, 1.5-3.0% Mo, 0.05-0.35% V, 0.02-0.20% in total of at least one kind of Nb and Ta, and 0.02-0.10% N. The steam turbine long blade must have a high tensile strength and, at the same time, a high high-cycle fatigue strength because it must bear high centrifugal stresses due to high speed rotation and vibration stresses. Therefore, the metallurgical structure of blade material must be wholly tempered martensite structure because fatigue strength decreases remarkably when the material has poisonous δ ferrite. In the steel according to the present invention, the components are adjusted so that a Cr-equivalent calculated by an equation described later is 10 or less and it is necessary that any δ ferrite phase is not substantially contained. The tensile strength of the long blade is not less than 120 kgf/mm 2 , preferably, not less than 128.5 kgf/mm 2 . In order to obtain a steam turbine long blades of homogeneousness and high tensile strength, it is preferable to effect, as a thermally refining heat treatment, such hardening that heats, after melting and forging, to a temperature of 1000-1100°C (preferably, 1000-1055°C) preferably keeping the temperature for 0.5-3 hours and then rapidly cools from the temperature to a room temperature (particularly, oil quenching is preferable), next tempering at a temperature of 550-620°C, particularly, twice or more tempering of primary tempering at a temperature of 550-570°C, preferably keeping the temperature for 1-6 hours and then rapidly cooling to a room temperature and secondary tempering at a temperature of 560-590°C, preferably, keeping the temperature for 1-6 hours and then rapidly cooling to a room temperature. It is preferable that the secondary tempering temperature is higher than the primary tempering temperature, particularly, it is preferable to be higher by 10-30°C and, more preferable, higher by 15-20°C. The present invention resides in a 3600 rpm steam turbine for 60 hz power generation in which the length of each blade of a low pressure turbine final stage is 838 mm or more, preferably 914 mm or more, more preferably 965 mm or more, and a 3000 rpm steam turbine for 50 Hz power generation in which the length of each blade of a low pressure turbine final stage is 1016 mm or more, preferably 1092 mm or more, more preferably 1168 mm or more, wherein a value of (blade portion length (cm) x revolution (rpm)) is 304,800 or more, preferably, 317,500 or more, and more preferably, 350,520 or more. Further, in the heat resistant blade material of the present invention, it is preferable to adjust the components so that a Cr equivalent calculated using the contents (wt%) of each element in the following equation becomes 4-10 in order to obtain a high strength, low-temperature toughness and fatigue strength by adjusting metal compositions to become whole martensite structure; Cr equivalent = Cr + 6Si + 4Mo + 1.5W + 11V + 5Nb - 40C - 30N - 30B -2Mn - 4Ni - 2Co + 2.5Ta C is necessary to be at least 0.08% to obtain a high tensile strength. An excessive amount of C decreases toughness, so that it should be 0.2% or less. In particular, 0.10-0.18% is preferable, and 0.12-0.16% is more preferable. Si is a deoxidizer, Mn is a deoxidizing desulfurizing agent. They are added when steel is melted, and even adding a small amount brings about an effect. Si is a δ ferrite producing element. Addition of a large amount of Si becomes a cause to produce poisonous δ ferrite which reduces fatigue strength and toughness, so that it must be 0.25% or less. Further, according to carbon vacuum deoxidizing method and electroslag melting method, it is unnecessary to add Si and it is better not to add Si. In particular, 0.10% or less is preferable and 0.05% or less is more preferable. An addition of a small amount of Mn increases toughness, however, an addition of a large amount decreases toughness, so that it must be 0.9% or less. In particular, since Mn is effective as a deoxidizer, addition of 0.4% or less is preferable and 0.2% or less is more preferable. Cr increases corrosion resistance and tensile strength, however, an addition of 13% or more becomes a cause to generate a δ ferrite structure. The corrosion resistance and tensile strength are insufficient when 8% or less is added, so that an amount of Cr is determined to be 8-13%. In particular, from a point of view of strength, 10.5-12.5% is preferable and 11-12% more preferable. Mo has an effect to raise tensile strength by a solid solution enhancing action and a precipitation enhancing action. Mo, however, is insufficient in an effect to improve the tensile strength, and addition of 3% or more becomes a cause to generate δ ferrite, so that Mo is limited to 1.5-3.0%. In particular, 1.8-2.7% is preferable and 2.0-2.5% is more preferable. W and Co have a similar effect to Mo. V and Nb have an effect to raise tensile strength by precipitating carbides and at the same time elevate toughness. The effect is in sufficient when not more than 0.05% V and not more than 0.02% Nb are added, and addition of V 0.35% or more , Nb 0.2% or more become a cause to generate δ ferrite. In particular, as for V 0.15-0.30% is preferable and 0.25-0.30 is more preferable. As for Nb, 0.04-0.15% is preferable and 0.06-0.12 is more preferable. Ta can be added in the same manner instead of Nb and they can be compoundedly added. Ni has an effect to improve low temperature toughness and prevent δ ferrite being generated. The effect is insufficient when Ni is 2% or less and saturates by addition of 3% or more. In particular, 2.3-2.9% is preferable and 2.4-2.8% is more pref erable. N has an effect to improve tensile strength and prevent δ ferrite being generated, however, the effect is insufficient with 0.02% or less, and an addition of more than 0.1% decreases toughness. In particular, excellent characteristics can be obtained in a range of 0.04-0.08%, and more in a range of 0.06-0.08%. An decrease in Si, P and S brings about an effect to improve a low temperature toughness without lowering tensile strength, so that it is desirable to extremely reduce them. From a point of view of improvement of the low temperature toughness, Si of 0.1% or less, P of 0.015% or less and S of 0.015 or less are preferable, in particular, Si of 0.05% or less, P of 0.010% or less and S of 0.010% or less are desirable. An decrease of Sb, Sn and As also have an effect to raise low temperature toughness, and it is desirable to extremely reduce them. However, from a point of view of steel production technology level at present, they are limited to Sb of 0.0015% or less, Sn of 0.01 or less and As of 0.02% ore less. In particular, Sb of 0.0010% or less, Sn of 0.005% or less and As of 0.01% or less are preferable. Further, in the present invention, a ratio of Mn/Ni is preferable to be 0.11 or less. Heat treatment of the material of the present invention is preferably as follow: First of all, the material is uniformly heated to a temperature sufficient to transform it into perfect austenite, that is, to 1000°C at minimum and 1100°C at maximum, rapidly cooled (preferably, oil cooling), and then, heated and kept at a temperature of 550-570°C and cooled (primary tempering), next, it is heated and kept at a temperature of 560-680°C to effect secondary tempering to make it into a wholly tempered martensite structure. (2) Explanation of compositions and reasons for limiting heat treatment conditions of a low alloy steel forming a rotor of a high and low pressure side-integrating steam turbine of the present invention: C is an element necessary to raise hardenability and secure strength. The content of 0.18% or less can not provide a sufficient hardenability, soft ferrite structure is formed in the center of a rotor, and sufficient tensile strength and yield strength can not be obtained. C of 0.28% or more decreases toughness, so that a range of C is preferable to be 0.18-0.28% Si and Mn were added as deoxidizer hereto, however, according to a vacuum C deoxidizing method and an electroslag remelting method, a sound rotor can be produced through melting without particularly adding such elements. It is necessary for Si and Mn to be smaller in view of brittleness due to use for a long time, Si and Mn are preferable to be 0.1% or less and 0.3% or less, respectively, in particular, Si of 0.05% or less and Mn of 0.1-0.25% are preferable and Si of 0.01% or less and Mn of 0.20% or less are more preferable. Ni is an essential element to improve hardenability and toughness. 1.5% or more is preferable to improve toughness and 2.5% or less is preferable to prevent decrease in creep rupture strength. Particularly, a range of 1.6-2.0% is preferable and a range of 1.7-1.9 is more preferable. Further, an addition of Ni can obtain characteristics of a high high-temperature strength and toughness by making an amount of Ni larger than an amount of Cr by at most 0.20%, or smaller than an amount of Cr by 30% or less. An addition of Cr of 1.5% or more improves hardenability and provides an effect to improve toughness and strength, further, corrosion resistance in steam is improved thereby. An addition of Cr of 1.5% or less is insufficient to obtain such an effect. Addition of Cr of 2.5% or less is preferable to prevent decrease in creep rupture strength. Particularly, a range of 1.9-2.1% is more preferable therefor. Mo of 1% or more precipitates very fine carbides in crystal grains during tempering treatment, and brings about an effect of raising high-temperature strength and preventing brittleness due to tempering. 2.0% or less is preferable for preventing toughness being decreased. In particular, 1.0-1.5% is preferable from a point of view of strength and toughness and 1.1-1.3% more preferable. V of 0.15% or more precipitates very fine carbides in crystal grains during tempering treatment, and brings about an effect of raising high-temperature strength and preventing brittleness due to the tempering. However, 0.35% or less is sufficient to obtain such an effect. In particular, a range of 0.20-0.30% is preferable and the range of more than 0.25% and not more than 0.30% is more preferable. When a low alloy of the above compositions is formed by melting, toughness is improved by adding any one element of rare-earth elements, Ca, Zr and Al. Such an effect is insufficient by adding a rare-earth element of less than 0.05%, and the effect saturates by adding more than 0.4%. Ca has an effect of raising toughness by adding a small amount, however, the effect is insufficient by adding less than 0.0005% and saturates by adding more than 0.01%. Zr of less than 0.01% does not sufficiently bring about an effect of raising toughness, and the effect saturates by adding Zr of more than 0.2%. Al of 0.001-0.02% brings an effect of raising toughness and creep rupture strength. Further, oxygens are concerned with high-temperature strength. In the steel according to the present invention, a higher creep rupture strength can be obtained by controlling O 2 to be in the range of 5-25ppm. It is preferable to add 0.005-0.15% of at least one kind among Nb and Ta. In a large-sized construction such as a steam turbine rotor shaft, an addition of 0.005-0.15% is preferable for suppressing crystallization of those huge carbides and raising strength and toughness. Particularly, 0.01-0.05% is preferable. An addition of W of 0.1% or more is preferable for raising strength, however, an addition of more than 1.0% brings about a problem of precipitation in a large sized lump and lowers strength, so that 0.1-1.0% is preferable and 0.1-0.5% is more preferable. A ratio of Mn/Ni and a ratio of (Si + Mn)/Ni are preferable to be 0.13 and 0.18 or less, respectively. Thereby, brittleness due to heating in a low alloy steel Ni-Cr-Mo-V having bainitic structure can be remarkably prevented, the alloy steel can be used for a high and low pressure side-integrated mono-block type rotor shaft. Further, a high 538°C 10 5 h creep rupture strength of 12 kg/mm 2 can be obtained by making a ratio of Ni/Mo at least 1.25, a ratio of Cr/Mo at least 1.1, or a ratio of Cr/Mo at least 1.45 and a ratio of Cr/Mo more than a value calculated by (-1.11 x Ni/Mo + 2.78) and by effecting heat treatment of the whole alloy under the same conditions. Further, an alloy structure having a higher strength at a high pressure side and a high toughness at a low pressure side can be obtained by containing an amount of Ni in a specific range relative to an amount of Cr. In a high and low pressure side-integrating steam turbine rotor shaft, it is preferable that a 538°C 10 5 h flatness and notch creep rupture strength is 13 kg/mm 2 or more at a high pressure side thereof, tensile strength is 84 kg/mm 2 or more, and fracture appearance transition temperature (FATT) is 35°C or less. In order to obtain such an excellent mechanical property, it is preferable to effect the following inclined refining heat treatment. Before effecting this refining heat treatment, it is preferable to perform perlite treatment of keeping at 650-710°C for 70 hours or more to make fine metallurgical structure. A high pressure side or high and middle pressure side, of a rotor shaft: to obtain a high high-temperature strength. Hardening: heating and keeping at 930-970°C and then cooling. Tempering: heating and keeping at 570-670°C and then gradually cooling. (Twice tempering is preferable, and it is preferable to effect, at least once of them, heating and keeping at 650-670°C) A low pressure side or middle and low pressure side, of the rotor shaft: to obtain a high tensile strength and low-temperature toughness. Hardening: heating and keeping at 880-910°C and then cooling. Tempering: heating and keeping at 570-640°C and then gradually cooling. (Twice tempering is preferable, and it is preferable to effect, at least once of them, heating and keeping at 615-635°C) That is, in the present invention, such an inclined heat treatment is preferable that the high pressure side or high and middle pressure side is hardened at a higher hardening temperature than the low pressure side, whereby a high-temperature strength at the high pressure side or high and middle pressure side is made higher than at the lower pressure side so as to obtain creep rupture time of 180 hours or more at 550°C and 30 kg/mm 2 , and transition temperature at the lower pressure side is made lower by 10°C or more than at the high pressure side or high and middle pressure side. A tempering temperature also is preferable to be higher at the high pressure side or high and middle pressure side than at the low pressure side. In any of hardening and tempering, it is preferable to take deviation heating and same cooling that heating temperature is changed and cooling is effected with the same means. Further, the inclined heat treatment also can be performed between the high pressure side and the middle and low pressure side. In this manner, steel having both a high creep rupture strength and a high impact value can be obtained. In the high and low pressure sides integrated rotor shaft, blades can be planted on the rotor shaft, which blades each have the length of 40 inches or more, preferably, 43 inches or more for 50 Hz power generation, and 33 inches or more, preferably, 35 inches or more for 60 Hz power generation. By using such a noble material for the rotor shaft, the above-mentioned long blades can be planted as final stage blades, and a ratio L/D between a length L between bearings for the rotor shaft and a blade diameter D can be made compact, that is, 1.4-2.3, preferably, 1.6-2.0. Further, a ratio (d/l) between the maximum diameter (d) of the rotor shaft and the length (l) of the final stage long blade can be made 1.5-2.0, whereby an amount of steam can be increased to the maximum in a relation to the rotor shaft characteristics, and a power generation system of large size and large capacity is possible. Particularly, this ratio is preferable to be 1.6-1.8. The ratio of 1.5 or more can be obtained from a relation of the number of blades, and the more the number is the better the efficiency is, however, 2.0 or less is preferable from the point of view of centrifugal force. A steam turbine using the high and low pressure sides-integrated mono-block rotor shaft of the present invention can output form 100,000 kW to 300,000 kW with a compact type. Expressing a distance between the bearings of the rotor shaft as a distance per power generation unit, the distance between the bearings can be made very short, that is, it is 0.8m or less per 10,000 kW, preferably, 0.25-0.6 m per 10,000 kW. By using the above-mentioned Ni-Cr-Mo-V low alloy steel for the high and low pressure sides-integrated mono-block rotor shaft, blades of the length of 762 mm or more, particularly, 851 mm or more can be provided for at least a final stage, an output per unit machine and the efficiency of the machine can be increase and it can be made compact. According to the present invention, a high and low pressure side-integrating steam turbine having long blades of 838 mm or more and being usable at a higher temperature can be produced. The turbine can increase an output per one machine, with a compact size. As a result, thermal efficiency can be improved and power generation cost can be reduced. BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a diagram showing a relation between tensile strength and (Ni-Mo); Fig. 2 is a diagram showing a relation between impact values and (Ni-Mo); Fig. 3 is a diagram showing a relation between tensile strength and hardening temperature; Fig. 4 is a diagram showing a relation between tensile strength and tempering temperature; Fig. 5 is a diagram showing a relation between impact values and hardening temperature; Fig. 6 is a diagram showing a relation between impact values and tempering temperature; Fig. 7 is a diagram showing a relation between impact values and tensile strength; Fig. 8 is a diagram showing a relation between 0.2% yield strength and tensile strength; Fig. 9 is a diagram showing a relation between 0.2% yield strength and 0.02% yield strength; Fig. 10 is a diagram showing a relation between impact values after heating and Ni; Fig. 11 is a sectional view of a high and low pressure sides-integrating steam turbine; Fig. 12 is a sectional view of a high and low pressure sides-integrating steam turbine; Fig. 13 is a sectional view of a rotor shaft for a high and low pressure sides-integrating steam turbine; Fig. 14 is a sectional view of a high and low pressure sides-integrating steam turbine; Fig. 15 is a sectional view of a rotor shaft for a high and low pressure sides-integrating steam turbine; Fig. 16 is a perspective view of a final stage blade; Fig. 17 is a perspective view of a tip portion of a blade; Fig. 18 is a diagram showing a combined cycle power generation system. DESCRIPTION OF EMBODIMENTS OF THE INVENTION EMBODIMENT 1 Table 1 shows chemical compositions (weight %) of 12% Cr steel relating to a long blade material for a high and low pressure sides-integrating steam turbine. Samples Nos 1-6 are experimental raw material which is formed by melting 150 kg by vacuum high frequency melting, heating to 1150°C and then forging. Sample No. 1 is heated at 1000°C for 1 hours, then cooled to a room temperature by hardening or quenching, and then heated to 570°C, kept at the temperature for 1 hour then air-cooled to the room temperature. Sample No.2 is heated at 1050°C for 1 hours, then cooled to a room temperature by oil-quenching, and then heated to 570°C, kept at the temperature for 2 hours then air-cooled to the room temperature. Samples Nos. 3 to 7 each are heated at 1050°C for 1 hours, then cooled to a room temperature by oil-quenching, next heated to 560°C, kept at the temperature for 2 hour then air-cooled to the room temperature (primary tempering), further heated to 58 0°C, kept at the temperature for 1 hour and then cooled in a furnace to a room temperature (secondary tempering). In the table 1, Nos. 3, 4 and 7 are materials of the present invention, Nos. 5 and 6 are comparison materials, and Nos. 1 and 2 are long blade materials used at present. Table 2 shows mechanical properties of those samples at room temperature. It was confirmed that the invention materials (Nos. 3, 4 and 7)sufficiently satisfy a tensile strength (1177 N/mm 2 or more, or 1256 N/mm 2 or more) and a low temperature toughness (20°C V-notch Charpy impact value of 39.2 Nm/cm 2 or more), required as a steam turbine long blade material. On the contrary, when the comparison materials Nos. 1, 5 and 6 are used as steam turbine long blades, any one or both of a tensile strength and an impact value are low. The comparison material No. 2 is low in tensile strength and toughness. No. 5 is a little low in impact value, that is, 37.3 Nm/cm 2 , which value is a little insufficient for 1092 mm long blades because 39.2 Nm/cm 2 or more is required for the long blades. Sample No. Tensile stength (N/mm 2 ) Elongation (%) Drawing (%) Impact value (Nm/cm 2 ) 1 1122.3 19.0 60.1 78.5 2 * 1124.2 18 . 6 59.7 11.8 3 1299.8 21.0 67.1 51.0 4 1323.4 20.8 66.8 47.1 5 * 1344.0 18.5 59.8 37.3 6 * 1164.4 21.1 67.3 51.0 7 1309.6 20.1 60 . 4 50.0 Fig. 1 is a graph showing a relation between an amount of (Ni - Mo) and tensile strength. In this embodiment, Ni and Mo are contained so as to be equivalent contents, whereby both of strength and toughness at low temperature are raised. The strength tends to decrease according to an increase in difference (Ni - Mo) in the content between them. The strength rapidly decreases when an amount of Ni becomes less by 0.6% or more than an amount of Mo, and the strength also rapidly decreases when the amount of Ni becomes more by 1.0% or more than an amount of Mo. Therefore, the strength is highest when an amount (Ni - Mo) is -0.6-+1.0%. Fig. 2 is a graph showing a relation between an amount (Ni - Mo) and impact value. As shown in Fig. 2, an impact value decreases around an amount of (Ni - Mo) of about -0.5%, however, the impact value is high where the amount is smaller or larger than about -0.5%. Figs. 3 to 6 are graphs showing an influence of heat treatment (hardening temperature and secondary tempering temperature) on a tensile strength and toughness of sample No. 3. After hardening was effected at a temperature of 975-1125°C and 1-hour tempering was effected at a temperature of 550-560°C, secondary tempering was effected at a temperature of 560-590°C. As showing in this figure, it was confirmed that the property (tensile strength ≧ 1260.6/mm 2 , 20°C notch Charpy impact value ≧ 39.2 Nm/cm 2 ) required for the long blades is satisfied. Further, The secondary tempering temperature shown in Figs. 3 and 5 is 575°C, and the hardening temperature shown in Figs. 4 and 6 is 1050°C. In the 12% Cr steel according to the present invention, particularly, it is preferable that an amount of (C + Nb) is 0.18-0.35%, a ratio of Nb/C is 0.45-1.00 and a ratio of Nb/N is 0.8-3.0. EMBODIMENT 2 Table 3 shows chemical compositions (by weight %) of 12% Cr steel relating to a steam turbine long blade in the same manner as the embodiment 1. Each sample is melted by vacuum arc melting and forged at about 1150°C. Table 4 shows heat treatment, mechanical properties at that temperature and metallurgical structure, of each sample. All the samples have wholly tempered martensitic structure. Average crystal grain size of each sample is 5.5-6.0 by grain size number (GSNo.) Fig. 7 is a graph showing relations between 20°C V-notch Charpy impact value and tensile strength, together with the samples of the embodiment 1. As shown in Fig. 7, an impact value of any sample is high and 24.5 Nm/cm 2 or more. Impact value (y) is preferable to be at least a value obtained by extracting (tensile strength (x) x 0.6) from 77.2, and more preferable to be at least a value obtained by extracting (tensile strength (x) x 0.6) from 80.4, and particularly preferable to be at least a value obtained by extracting (tensile strength (x) x 0.6) from 84.0. Fig. 8 is a graph showing a relation between 0.2% yield strength and tensile strength. In the material according to the present invention, particularly, it is preferable that 0.2% yield strength is at least a value obtained by adding (tensile strength(x) x 0.5) to 36.0. Fig. 9 is a graph showing a relation between 0.02% yield strength and tensile strength. In the material according to the present invention, particularly, it is preferable that 0.2% yield strength is at least a value obtained by adding (0.02% yield strength(x) x 0.54) to 58.4. EMBODIMENT 3 Fig. 11 shows a sectional view of a high and low pressure sides-integrating steam turbine according to the present invention. In this steam turbine, an output per one turbine can be increased by raising steam pressure and temperature to 100 ata and 536°C, respectively, at a main steam inlet. In order to increase an output per one turbine, it is necessary to increase the length of a final stage blades and a flow rate of steam. For example, when the length of the final stage blades is made long from 66 cm to 85 cm, an annulus area is increased to about 1.7 times. Therefore, if an output of a conventional steam turbine is 100 MW, an output of the turbine having such long blades is increased to 170 MW. By making the blades longer into 101.6cm, the output per one turbine can be increased to two or more times. In a case where long blades of 83.8 cm or more or 101.6 cm or more are used according to power generation cycles, as a high and low pressure sides-integrated mono-block rotor shaft material, preferable is a material having tensile strength of 88 kg/mm 2 or more, a 538°C 10 5 h creep rupture strength of 15 kg/mm 2 or more and impact absorption energy of 2.5 kg-m(3kg-m/cm 2 ) at room temperature from the point of view of securing safety against brittleness rupture of a low pressure side. A middle pressure section has blades the length of which becomes gradually longer toward the low pressure side, and the blades are formed by forging of a martensite steel comprising, by weight, 0.05-0.15% C, not more than 1% Mn, not more than 0.5% Si, 10-13% Cr, not more than 0.5% Mo, not more than 0.5% Ni and balance Fe. The final stage has about 90 blades per one circle, the blade portion length of which is 89 cm for 60Hz power generation, and the blades are formed by forging of a martensite steel comprising, by weight, 0.08-0.18% C, not more than 1% Mn, not more than 0.25% Si, 8-13% Cr, 2.0-3.5% Ni, 1.5-3.0% Mo, 0.05-0.35% V, 0.02-0.10% N, at least one kind, 0.02-0.2% in total, of Nb and Ta. In particular, in this embodiment, the alloy of No. 2 in the table 1 of the embodiment 1 was used. Further, in the final stage, a shield plate of Stellite for erosion prevention is provided on a leading edge portion of the tip of each blades by welding. Further, partial hardening is performed in each blade other than provision of the shield plate. For blades for 50Hz, the blade portion length of which is 109 cm or more, a forging material of the same martensite steel as the above is used. Those blades are fixed by fixing 4 -5 blades per each stage to a shroud of the same material by caulking tenons provided on the tip of each of the blades (3) For stationary vanes 7, the stationary vanes of until the third stage of the high pressure section are made of a martensite steel having the same compositions as the blades, but, the same material as the blade material of the middle pressure section is used for the other vanes. (4) For the casing 6, Cr-Mo-V cast steel is used which comprises, by weight, 0.15-0.3% C, not more than 1% Mn, not more than 0.5% Si, 1-2% Cr, 0.5-1.5% Mo, 0.05-0.2% V and not more than 0.1% Ti. A generator 8 can generate electric power of 100,000-200,000 kW. In this embodiment, a distance between bearings 12 of the rotor shaft is about 520 cm, the outer diameter at the final stage blades is 316 cm, and a ratio of the distance to the outer diameter is 1.65. A power generation capacity is 100,000 kW. The distance between the bearings is 0.52m per power generation output 10,000 kW. Further, in this embodiment, in a case where 101.6 cm blades are used for the final stage, the outer diameter of the blades is 363 cm, a ratio of the distance between the bearings to the outer diameter is 1.43. Thereby, power generation of 200,000 kW is possible, and the distance between the bearings per 10,000 kW is 0.26 m. A ratio of an outer diameter of a blade planting portion of the rotor shaft to the blade length in the final stage is 1.70 for 85 cm blades, and 1.71 for 101.6 cm blades. In this embodiment, even steam temperature of 566°C can be applied and even steam pressure of 121 ata, 169 ata and 224 ata can be applied. A steam turbine according to the present invention has blades of 13 stages planted on a high and low pressure sides-integrated mono-block rotor shaft 3, and steam flows, at high temperature of 538°C and high pressure of 8.6 × 10 6 Pa, into between the blades from a steam inlet 1 through a steam control valve 5. The steam flows from the inlet 1 in one direction to become a temperature of 33°C and a pressure of 9.6 × 10 4 Pa and is exhausted from a steam outlet 2 through the final stage blades 4. The high and low pressure sides- integrated mono-block rotor shaft 3 according to the present invention is exposed to the steam of 538°C to a fluid of 33°C, the forging steel of Ni-Cr-Mo-V having the properties described in this embodiment is used for the shaft 3. A planting portion of the rotor shaft 3 in which the blades are planted is formed in disc-shape, and integrally formed from the shaft 3 by machining. The shorter the blade length is, the longer the length of the disc portion is, whereby vibrations are made small. Compositions of material of each part in this embodiment are as follows: (1) Rotor shaft Rotor shafts each are produced with shaft materials of the alloy compositions listed in the table 5 by electroslag remelting, and forged in diameter of 1.2m. Each rotor shaft is heated to 950°C and kept for 10 hours, and then cooled with sprayed water while rotating the rotor shaft so that a cooling speed at a central portion thereof is about 100°C/h. Next, each rotor shaft is tempered by heating to 665°C and keeping for 40h. Test pieces are cut out from a central portion of each rotor shaft, and a creep rupture test, V-notch impact test (cross sectional area of test piece 0.8 cm 2 ) before and after heating (500°C, 3,000h) and tensile strength test were conducted. The test values are substantially the same as values described later. (2) Blade The length of 3 stages at a high temperature and high pressure side is 40 mm and the blade is made of forged steel of martensite steel comprising, by weight, 0.20-0.30% C, 10-13% cr, 0.5-1.5% Mo, 0.5-1.5% W, 0.1-0.3% V, not more than 0.5% Si, not more than 1% Mn and balance Fe. The table 5 shows chemical compositions of typical samples served for tests of toughness and creep rupture of a high and low pressure integral steam turbine rotor. The samples are melted and formed in lump in a vacuum high frequency melting furnace, and hot-forged in 30 mm squire in cross secion at a temperature of 850- 1150°C. Sample Nos. 21 to 23 and 27 to 31 are materials according to the present invention, Sample Nos. 24 to 26 are melted and formed for comparison, sample No. 25 is a material corresponding to ASTM standard A470 class 8, and sample No. 26 is a material corresponding to ASTM standard A470 class 7. Those samples, which are simulated by the conditions of a central portion of a high and low pressure sides-integrated mono-block steam turbine rotor shaft, are heated to 950°C, transformed to austenitic structure, and then cooled at a speed of 100°C/h for hardening. Next, they are heated at 665°C for 40h and cooled thereby tempering. A Cr-Mo-V steel according to the present invention does not include any ferrite phase and it is whole bainitic structure. A temperature at which steel of the present invention is transformed into austenitic structure is necessary to be 900-1000°C. A high toughness can be obtained at a temperature less than 900°C, but a creep rupture strength becomes low. A high creep rupture strength can be obtained at a temperature higher than 1000°C, but toughness becomes low. A tempering temperature must be 630-700°C. A high toughness can not be obtained at a temperature less than 630°C and a high creep rupture strength can not be obtained at a temperature higher than 700°C. Table 6 shows results of tensile strength test, impact test and creep rupture test. Toughness is expressed by V-notch Charpy impact absorption energy tested at a temperature of 20°C. A creep rupture strength is expressed by a 538°C 10 5 h strength obtained by a Rurson mirror method. As is apparent from the table, in the materials according to the present invention, a tensile strength at room temperature is 88 kg/mm 2 or more, 0.2% yield strength is 70kg/mm 2 or more, FATT is 40°C or less, impact absorption energy before or after heating is 2.5kg-m or more and creep rupture strength is about 11 kg/mm 2 or more, and in any cases of which the value is high. The materials according to the present invention each are useful for high and low pressure sides-integrated mono-block steam turbine rotors. In particular, materials having strength of about 147.1 N/mm 2 or more are better for the turbine rotors on which long blades of 851mm are planted. Further, in order to examine characteristics of brittleness of sample No. 24 and No. 25 (each corresponding to currently used high pressure rotor material) and No. 26 (currently used low pressure rotor material),impact test were conducted of samples before and after treatment of 500°C for 3000h for embrittling, and a 50% fracture appearance transition temperature (FATT) was examined. FATT is increased (which means to be made brittle) from 119°C to 135°C (ΔFATT = 16°C) in No.25, from -20°C to 18°C (ΔFATT = 38°C) in No. 26 by the embrittling treatment. On the contrary, it was confirmed that FATT of the sample No. 23 according to the present invention is 38°C before and after the brittleness making treatment, that is, not made brittle. Sample Nos. 28 to 31 have rare-earth elements of (La-Ce), Ca, Zr and Al, added thereto, respectively and toughness of each of the samples is increased by adding the element or elements. Particularly, an addition of rare-earth elements is effective for improving the toughness. A material having Y added thereto other than La-Ce also was examined, as a result, it was confirmed that the addition brought an effect of remarkably improving the toughness. Further, a high creep rupture strength of 12 kg/mm 2 or more can be obtained by reducing O 2 to an amount of 100ppm or less, particularly, 15 kg/mm 2 or more by reducing it 80ppm or less and 18 kg/mm 2 or more by reducing it 40ppm or less. A 538°C 10 5 h creep rupture strength has a tendency to decrease according to an increase in an amount of Ni, particularly, the strength becomes about 11 kg/mm 2 or more when an amount of Ni is 2% or less, more particularly, 12 kg/mm 2 or more is exhibited at an amount of Ni of 1.9% or less. Fig. 10 is a graph showing a relation between impact values after heating for 3000h and an amount of Ni. As shown in Fig. 10, the materials, of which a ratio of (Si+Mn)/Ni is 0.18 or less or a ratio of Mn/Ni is 0.12 or less, have a high impact value according to an increase in an amount of Ni, however, a material or materials of the comparison samples No. 12 to No. 14, of which a ratio of (Si+Mn)/Ni is more than 0.18 or a ratio of Mn/Ni is more than 0.12, has a low impact value of 2.4 kg-m or less, and even if an amount of Ni becomes high, it influences little on the impact value. It is apparent that an influence of Mn or (Si+Mn) on the impact value is very large at a specific amount of Ni. When an amount of Mn is 0.2% or less or an amount of (Si+Mn) is 0.25% or less, a very high impact value is presented. Therefore, when a ratio of (Si+Mn)/Ni is 0.18 or less or a ratio of Mn/Ni is 0.12 or less, a high impact value of 2.5 kg-m or more is presented. Until a composition ratio between (V+Mo)/(Ni+Cr) relating to creep rupture strength and impact absorption energy reaches about 0.7, wherein V and Mo are elements forming carbides and Ni and Cr are element improving hardenability, the creep rupture strength and the impact absorption energy increase as the composition ratio (V+Mo)/(Ni+Cr) increases. The impact absorption energy becomes low as the above composition ratio becomes larger. Toughness and creep rupture strength, which are necessary for the high and low pressure sides-integrated mono-block turbine rotor can be made excellent in their property by making the composition ratio (V+Mo)/(Ni+Cr) into a range of 0.45-0.7. Relations between impact values after heating for making brittle and an amount of Mn or an amount of (Si+Mn) of material containing 1.6-1.9% Ni were examined, as a result, it was found that an influence of an amount of Mn or an amount of (Si+Mn) on impact value is very large at a specific amount of Ni, a very large impact value is presented at 0.2% or less of Mn or at 0.07-0.25% of (Si+Mn). Relations between impact values and a ratio Mn/Ni or (Si+Mn)/Ni in material containing 1.52-2.0% Ni were examined, as a result, it was found that a high impact value of 2.5 kg-m or more was presented when the ratio of Mn/Ni is 0.12 or less, the ratio of (Si+Mn)/Ni is 0.04-0.18. EMBODIMENT 4 Table 7 is chemical compositions (by weight %) of typical samples relating to high and low pressure integral steam turbine rotor shaft according to the present invention. Sample Nos. 41 and 42 are conventional steels used for high pressure rotor shafts and low pressure rotor shafts, respectively. Nos. 43-52 are steels of the present invention. Each steel of the present invention is melted in high frequency vacuum melting furnace, formed into lump and then hot-forged at 900-1150°C. Simulating the conditions of a central portion of a high and low pressure integrated steam turbine rotor shaft, those sample were heated to transform into austenitic structure, and then cooled at a speed 100°C/h to effect hardening. Next, they were heated at 665°C for 40h, cooled in the furnace thereby effecting a tempering treatment. A Ni-Cr-Mo-V steel of the present invention was whole bainitic structure without containing any ferrite phase. A temperature at which the steel of the present invention is transformed into austenitic structure is necessary to be 870-1000°C. The heating temperature of less than 870°C can obtain a high toughness, but creep rupture strength becomes low. When the temperature is higher than 1000°C, a high creep strength can be obtained, but the toughness becomes low. Tempering temperature is necessary to be 610-700°C. The heating temperature of less than 610°C can not obtain a high toughness, and when it is higher than 700°C, a high creep rupture strength can not be obtained. Table 8 is test results of tensile strength, impact, and notch creep rupture tests. The toughness is expressed by V-notch Charpy impact absorption energy tested at a temperature of 20°C. The creep rupture strength is expressed by a 538°C 10 5 h strength obtained by Raruson mirror method. As is apparent from the table, the materials of the present invention each have a tensile strength of 863.3 N/mm 2 or more at room temperature, a 0.2% yield strength of 686.7 N/mm 2 or more, FATT of 40°C or less, impact absorption energy before and after heating of 24.5 Nm or more and creep rupture strength of 686.7 N/mm 2 or more, which are excellent values, and the materials are very useful for high and low pressure sides-integrated mono-block turbine rotors. In particular, the material having about 15 kg/mm 2 or more is better for the turbine rotor having blades of 33.5" length. Samples Nos. 47-52 each have rare-earth elements (La-Ce), Ca, Zr and Al added thereto, and toughness increases by adding those elements. In particular, an addition of the rare-earth elements is effective for improving the toughness. A material with Y added thereto other than the rare-earth metal (La-Ce) was examined and it was confirmed that the material also had a remarkable effect of improving the toughness. Further, a ratio of Ni/Mo is 1.25 or more and a ratio of Cr/Mo is 1.1 or more, or a ratio of Cr/Mo is 1.45 or more, or a ratio of Cr/Mo is a value or more obtained by (-1.11 x (Ni/Mo) + 2.78), whereby the whole is subjected to the same heat treatment and a high 538°C 10 5 h creep rupture strength of 12 kg/mm 2 or more can be obtained. Fig. 12 shows a partially sectional view of reheating type high and low pressure sides-integrating steam turbine according to the present invention. The steam turbine according to the present invention is a reheating type and has 14 stages of blades 4 planted on the high and low pressure sides-integrate mono-block rotor shaft 3, that is, 6 stages of a high_pressure section or side, 4 stages of a middle pressure section or side and 14 stages of a low pressure section or side. A high pressure steam flows into a high temperature and high pressure side at 538°C and 169 atg from a steam inlet 21 through a control valve 5 as mentioned previously. The steam flows in a left direction of Fig. 12 from the steam inlet and goes out from a high pressure steam outlet 22, and the steam is heated again to 538°C and then sent from a reheated steam inlet 23 to a middle pressure turbine section. The steam which entered the middle pressure turbine section is sent to a low pressure turbine section together with steam from a low pressure steam inlet 24. The steam is turned into a steam of 33°C and 9.6 × 10 4 Pa and exhausted from a final stage blades 4. The high and low pressure sides-integrated mono-block rotor shaft 3 of the present invention is exposed to a temperature from 538°C to 33°C, and a forging steel of the above-mentioned Ni-Cr-Mo-V low alloy steel is used. A portion of the shaft 3 in which the blades are planted is shaped in a disc-shape, and formed as one piece by machining the shaft 3. The shorter the length of the blades is, the longer the length of the disc portion is, whereby vibrations are reduced. The blades 4 of the high pressure section are arranged in at least 5 stages, 6 stages in a current case. The stages other than first and second stages are arranged at the same distances therebetween, and a distance between the first stage and the second stage is 1.5 to 2.0 times the distance between the other stages. The axial thickness of the blade planting portion of the shaft 3 is the thickest at the first stage, and the thickness from the second stage to the final stage becomes gradually thicker and the thickness of the first stage is 2-2.6 times the thickness of the second stage. The blades of the middle pressure section are arranged in 4 stages, the axial thickness of a blade planting portion in the first and final stages is the same as each other and thickest, and the thickness of the second, third, increases in turn toward a downstream side of a steam flow. The low pressure section has blades arranged in 4 stages. The axial thickness of a blade planting portion in the final stage is 2.7-3.3 times the axial thickness of a blade planting portion at a stage planting portion just at a upstream side of steam flow, and the axial thickness of the blade planting portion of the stage at just upstream side of the final stage is 1.1-1.3 times the axial thickness of the blade planting portion of the stage at just upstream side of this stage. Distances between the central portions of blades from the first stage to the fourth stage of the middle pressure section are about the same as one another, distances between the central portion of blades of the low pressure section become larger from the first stage toward the final stage. A ratio of the distance in each stage to that in the stage at the upstream side becomes larger toward the downstream side, a ratio of the distance in the first stage to that in the stage at the upstream side of the first stage of the low pressure section is 1.1-1.2 and a ratio of the distance in the final stage to that in the stage at the upstream side is 1.5 to 1.7. The length of each blade of the middle and low pressure sides becomes gradually larger from the first stage toward the final stage. The length of each blade in each stage is 1.2-2.1 times the blade length in the stage at its upstream side, and 1.2-1.35 times and longer until the 5th stage, 1.5-1.7 times in the second stage of the low pressure section and 1.9-2.1 times in each of the third and fourth stages. The blade length in each stage from the middle pressure section to the low pressure section in this embodiment is 6.35cm, 7.62cm, 12.7cm, 16cm, 25.4 cm, 52.6cm and 101.6 cm. Reference number 14 denotes an inner casing and 15 an outer casing. Fig. 13 shows a shape of a high and low pressure sides-integrated mono-block rotor shaft 3 according to the present invention. The rotor shaft 3 is formed as follows: A forging steel of alloy compositions shown in the table 9 is melted in an arc melting furnace, then poured in a ladle and then refined in vacuum by blowing Ar gas into the ladle from its lower portion, and formed in lump. C Si Mn P S Ni Cr Mo V Fe 0.23 0.01 0.20 ≦0.005 ≦0.005 1.80 2.01 1.20 0.27 bal. (Sn ≦ 0.010, Al ≦ 0.008, Cu ≦ 0.10, Sb ≦ 0.005, As ≦ 0.008, O 2 ≦ 0.003) Next, it is forged at a temperature of 900-1150°C to be 1.7m in maximum diameter and about 8m in length, its high pressure side 16 is heated to 950°C and kept for 10h, its middle and low pressure side 17 is heated to 880°C and kept for 10h, and then cooled by sprayed water while rotating the rotor shaft so as to be cooling speed of 100°C/h at the central portion. Next, the high pressure side 16 is tempered by heating to 650°C keeping for 40h, and the low pressure side 17 also is tempered by heating to 625°C keeping for 40h. Test pieces are cut out from a central portion of the rotor shaft, and tested of creep rupture test, V-notch impact test (sectional area of the test piece is 0.8 cm 2 ), and tensile strength test. Table 10 shows the test results. Further, as shown in Fig. 13, blade planting portion 18 of the high pressure side 16, and middle and low pressure side 17 have the following thickness and distant as mentioned above. Reference number 19 denotes bearing portions and 20 a coupling. Diameters of moving blade portions and stationary vane portions of the high pressure section are same in each stage. The diameter of the moving blade portion from the middle pressure section to the low pressure section becomes gradually larger, the diameter in the stationary vane portion is same from the fourth stage to the sixth stage, same from the sixth stage to eighth stage and becomes larger from the eighth stage toward the final stage. The thickness of a blade planting portion of the final stage in the axial direction 0.3 times the length of blade portion, and the thickness is preferable to be 0.28 to 0.35 times the length. The rotor shaft has a maximum blade portion diameter at the final stage, the diameter is 1.72 times the blade portion length, and it is preferable to be 1.60-1.85 times. Further, the length between the bearings is preferable to be 1.65 times the diameter formed by the tip portions of final stage blades. In this embodiment, the generator can generates 100,000-200,000 kW. The distance between the bearings 32 of the rotor shaft in this embodiment is about 520 cm, the outer diameter of the final blades is 316 cm, and a ratio of the distance between the bearings to the outer diameter is 1.65. The distance (length) between the bearings is 0.52 m per an output of 10,000 kW. Further, the outer diameter of the tip portions of the final blades is 365 cm in a case where the final stage blades each have 101.6 cm length, and a ratio of the distance between the bearings to the outer diameter is 1.43. Thereby, an output of 200,000 kW is possible, and the distance between the bearings per 10,000 kW is 0.26m. A ratio of the outer diameter of a blade planting portion of the rotor shaft to the length of final stage blades is 1.70 when the blades have 85 cm length, and 1.71 when they have 101.6 cm length. This embodiment can be applied even if a steam temperature is 566°C, and each steam pressure of 1.19 × 10 7 Pa, 1.66 × 10 7 Pa and 2.2 × 10 7 Pa can be applied. EMBODIMENT 5 Fig. 14 is a sectional view showing an example of a reheating type high and low pressure sides-integrating steam turbine construction. In the steam turbine, a steam of 538°C 1.24 × 10 7 Pa enters at an inlet 21, turns to be 367°C and 3.73 × 10 6 Pa and is exhausted from a high pressure steam outlet 22 through a high pressure section of a high and low pressure integral rotor shaft 3. The steam heated to 538°C and 3.43 × 10 6 Pa by a reheater enters a middle pressure section of the rotor shaft 3 from a reheated steam inlet 23, flows into a low pressure section and turns to be a steam of about 46°C and 0.98 ×10 4 Pa, and then exhausted from an outlet. A part of the steam, which went out from the high pressure steam outlet 22, is used as a heat source of other, and supplied again from a low pressure steam inlet 24 as a heat source of the turbine. In this embodiment, also, as material of the high and low pressure sides-integrated mono-block rotor shaft 3, blades 4, stationary vanes 7 and a casing 6, the same material as in the embodiments 2 or 3 is used. Blades of 109.2 cm are used in the final stage, and a power generation output is 1,250,000 kW. The final stage blades are made of the same martensite steel as in the embodiment 3. A distance between bearings of the rotor shaft 3 is about 655 cm, a diameter by the final stage blades of 109.2 cm is 382 cm, and a ratio of the distance to the diameter is 1.72. The steam turbine according to the present invention is a reheating type and has a plurality of blades 4 planted on the high and low pressure sides-integrated mono-block rotor shaft 3 in 7 stages at a high pressure side, 6 stages in a middle pressure side and 5 stages at low pressure side, that is, 18 stages in total. A high pressure steam flows into a high temperature and high pressure side at 538°C and 1.66 × 10 7 Pa from the steam inlet 21 through a control valve as mentioned previously. The high pressure steam f lows in one direction from the steam inlet and goes out from the high pressure steam outlet 22, and the steam is heated again and then sent from the reheated steam inlet 23 to the middle pressure turbine section. The steam which entered the middle pressure turbine section is sent to the low pressure turbine section together with steam from the low pressure steam inlet 24. The steam is turned into a steam of 33°C and 9.6 × 10 4 Pa and exhausted from the final stage blades 4. The high and low pressure sides-integrated mono-block rotor shaft 3 of the present invention is exposed to a temperature from 538°C to 33°C, a forging steel of the above-mentioned Ni-Cr-Mo-V low alloy steel is used. A portion of the shaft 3 in which the blades are planted is shaped in a disc-shape, and formed as one piece by machining the shaft 3. The shorter the length of the blades is, the longer the length of the disc portion is, whereby vibrations are reduced. The blades 4 of the high pressure turbine section are arranged in 7 stages or at least 5 stages. The stages from the first stage to the stage just before the final stage are arranged at the same distances therebetween, and a distance between the final stage and the stage just before the final stage is 1.1 to 1.3 times the distance between the other stages than the first stage. The axial thickness of the blade planting portion of the shaft 3 is the thickest at the first and final stages, and the thickness is substantially the same in the other stages than the first and final stages. The thickness of the first stage is 2-2.6 times the thickness of the second stage. The blades of the middle pressure section are arranged in 6 stages, distance between the blade centers is largest at the first and second stages and it is the substantially the same from the second stage to the final stage. The distance between the first and second stages is 1.1-1.5 times the distance between the other stages. The low pressure section has blades arranged in 5 stages. Distance between the central portions of stage blades increase gradually from the first stage to the final stage, and the final stage is 4.0-4.8 times the first stage. The thickness of a blade planting portion in the axial direction is the thickest in the final stage, becomes smaller stepwise from the final stage toward the upstream side of the steam flow, and the axial thickness of the final stage is 2.0-2.8 times that in the stage just upstream side of the final stage, and the axial thickness of the blade planting portion of the stage at just upstream side of the final stage is 1.0-1.5 times the axial thickness of the blade planting portion of the stage at just upstream side of this stage. The first stage has a thickness 0.20-0.25 times that of the finals stage. The length of blade portion of each blade becomes gradually longer from the first stage to the final stage in the low pressure section, the blade length in the final stage is 109.2 cm, and the blade length of the final stage is 1.8-2.2 times that of the stage at a just upstream side of the final stage. The blade length of the stage just before the final stage is 1.7-2.1 times that of the stage just before that stage and the blade length of the stage just before that stage is 1.1-1.5 times that of the stage just before the above last mentioned stage. The length of each blade of the middle pressure section becomes gradually larger from the first stage toward the final stage. The length of final stage blades is 3-3.5 times the blade length of the first stage blades. The blade length in each stage from the middle pressure section 25 to the low pressure section 26 in this embodiment is 4cm, 5.3 cm, 5.3 cm, 6.6 cm, 7.6 cm, 11.5 cm, 15.7 cm, 23.6 cm, 30.2 cm, 56.4cm and 109.2cm. Reference number 14 denotes an inner casing and 15 an outer casing. Fig. 15 shows a shape of the high and low pressure sides-integrated mono-block rotor shaft 3 according to the present invention. The rotor shaft 3 in this embodiment is formed as follows: A forging steel of substantially the same alloy compositions as in the table 9 is produced and forged in the same manner in the embodiment 4 to be 1.7m in maximum diameter and about 8m in length. Its high and middle pressure sides are heated to 950°C and kept for 10h and its low pressure side is heated to 880°C and kept for 10h, and then cooled with sprayed water while rotating the rotor shaft so as to be a cooling speed of 100°C/h at the central portion. Next, the high and middle pressure sides are tempered by heating to 655°C keeping for 40h, and the low pressure side also is tempered by heating to 620°C keeping for 40h. Test pieces are cut out from a central portion of the rotor shaft, and tested of creep rupture test, V-notch impact test (sectional area of the test piece is 0.8 cm 2 ), and tensile strength test. The test results are the same as in the embodiment 4. The diameter of the final stage blades portion is 380 cm, a ratio of the distance between bearings to the diameter is 1.72, and it is preferable to be 1.60-1.85. The distance between bearings per power generation output of 10,000 kW is 0.52m and preferable to be 0.45-0.70. Diameters of moving blade portions and stationary vane portions in the high and middle pressure sides are same in each stage. The diameter of the moving blade portion in the final stage of the middle pressure is a little larger, the diameter in the low pressure section becomes gradually stepwise larger in the moving blade portion and the stationary vane portion. Further, the thickness of a blade planting portion in the axial direction is 0.30 times the length of the final stage blade portion, and the thickness is preferable to be 0.28 to 0.32 times the length. The blade planting portion diameter at the final stage is 1.50 times the blade portion length, and preferable to be 1.46-1.55 times. Fig. 16 is a perspective view of the final stage blade the blade portion length of which is 1092mm. In Fig. 16, reference number 51 denotes a blade portion on which a high speed steam impinges, 52 a planting portion into the rotor shaft, 53 holes for inserting pins for supporting centrifugal force of the blades, 54 an erosion shield (a Stellite plate of Co-base alloy is joined by welding) for preventing erosion by water drops in steam, and 57 a cover. In this embodiment, the blade is forged as one piece and then formed by machining. The cover can be mechanically formed as one piece with the blade. 109.2 cm long blades each were melted and formed by electroslag remelting method, forged and subjected to heat treatment. The forging was effected in a range of 850-1150°C, and the heat treatment was effected under the conditions (hardening: 1050°C, primary tempering: 560°C and secondary tempering: 580°C) as in the embodiment 1. Sample No. 7 of the table 1 shows chemical compositions of this long blade material. The metallurgical structure of this long blade was wholly tempered martensite structure. No. 7 of the table 1 has an excellent room temperature tensile strength and 20°C V-notch Charpy impact value. It was confirmed that this 1092 mm long blade has required mechanical properties, that is, a tensile strength of 1260.6 N/mm 2 or more and 20°C V-notch Charpy impact value of 39.2 Nm/cm 2 or more, and suff iciently satisfied mechanical properties. Fig. 17 is a perspective view sectioned in part showing a condition in which an erosion shield (Stellite alloy) 54 is joined by electron beam welding or TIG welding 56. As shown in Fig. 17, the shield 54 is welded at 2 positions, front and back sides. EMBODIMENT 6 Fig. 18 is a schematic diagram of a multi axis type combined cycle power generation system employing both of 2 gas turbines and one high and low pressure integral steam turbine. In a case where electric power is generated using a gas turbine, in recent years there is such tendency that a so-called compound power generation system is used in which the gas turbine is driven with liquified natural gas (LNG) as fuel, a steam turbine is driven with steam obtained by recovering energy of waste or exhaust gas of the gas turbine, and a generator is driven by the gas turbine and the steam turbine. By using the compound power generation system, the thermal efficiency can be improved greatly to be about 44% as compared with a conventional single steam turbine power generation of which the thermal efficiency is 40%. In such a compound power generation plant, recently, further, use of both of liquid natural gas(LNG) and liquid petroleum gas (LPG) is planned in stead of use of only LNG, and a smooth operation of plant and improvement of economy are planned by combustion of both of LNG and LPG. In the power generation system, first of all, air is transferred to an air compressor of the gas turbine through an inlet air filter and inlet air silencer, and the air compressor compresses the air and transfers the compressed air into low NOx combustors. In the combustors, fuel is injected into the compressed air and burned to generate high temperature gas of 1200°C or more and the gas works in the gas turbine to generates power. Exhaust gas of 530°C or more from the gas turbine is transferred into an exhaust or waste gas recovery boiler through an exhaust gas silencer. The boiler recovers energy of the exhaust gas to generate high pressure steam of 530°C or more. The boiler is provided with a denitration apparatus using dry type ammonia contact reducing system. The exhaust gas is exhausted from a several hundreds meters high stack with tripod. The generated high pressure steam and low pressure steam are transferred to the steam turbine having a high and low pressure integral rotor. The turbine is described later. Further, the steam gone out of the steam turbine flows into a condenser, in which it is deaerated in vacuum to be condensate. The condensate is pressurized by a condensate pump, and sent to the boiler as a feed water. The gas turbine and the steam turbine drives the generator at both shaft ends of the generator to generate electric power. For cooling gas turbine blades used in such a compound power generation plant, in some cases, steam used in the steam turbine may be used as cooling medium. Generally, air is used as a coolant for blades. However, steam also is used as such a coolant. Steam has a large cooling effect because the steam has a drastically large specific heat as compared with air and has light weight. Since the steam has a large specific heat, the temperature of a main flow gas is reduced remarkably and the thermal efficiency of the whole plant is decreased when the steam used as coolant is flowed into the main flow gas, so that steam of relatively low temperature (of example, about 300-400°C)is supplied to turbine blades from coolant supply ports, cools blade bodies, the coolant the temperature of which is elevated to relatively high temperature through heat-exchange is recovered and then returned into the steam turbine. Thereby decrease in the temperature (about 1300-1500°C) of the main flow gas is prevented and the efficiency of the steam turbine is raised, whereby the efficiency of the whole plant can be improved. By this multi-axis type combined power generation system, 100,000-500,000 kW in total can be generated, wherein the gas turbine can generate 50,000-300,000 kW and the steam turbine 50,000-200,000 kW. Thereby, the steam turbine in the embodiment is made compact and all the plant including a plurality of gas turbines and steam turbine can generate power of 700,000-1,000,000 kW. The plant having the same capacity as a large-sized steam turbine can be made at low cost, compared with the large sized steam turbine and has a large merit that the turbine can be effectively or ecomonically operated responding to fluctuation in power generation amount.

Claims: A high and low pressure sides integrating steam turbine comprising a rotor having a mono-block rotor shaft (3) on which blades (4) are planted in multi-stages from a high pressure side to a low pressure side, and a casing (6) covering said rotor, wherein an inlet temperature of steam to first stage blades (4) on the high pressure side is not less than 530°C, and final stage blades (4) on the low pressure side have a value of blade length in centimetres multiplied by revolutions per minute of not less than 304,800, characterized in that each of said final stage blades (4) on the low pressure side is made of martensite stainless steel comprising, by weight percentage, 0.08 to 0.18%C, not more than 0.25% Si, not more than 1.00% Mn, 8.0 to 13.0% Cr, more than 2.1% and not more than 3% Ni, 1.5 to 3.0% Mo, 0.05 to 0.35% V, 0.02 to 0.20% in total of a least one kind of Nb and Ta, and 0.02 to 0.10% N. A high and low pressure sides integrating steam turbine according to claim 1, characterized in that said martensite stainless steel forming said final stage blades (4) on the low pressure side has a tensile strength of not less than 128.5 kg /mm 2 at room temperature. A high and low pressure sides integrating steam turbine according to claim 1, characterized in that said high and low pressure side integrating steam turbine is for 50 cycle, and said final stage blades (4) on the low pressure side each have a blade portion length of at least 101.6 cm. A high and low pressure sides integrating steam turbine according to claim 1, characterized in that said high and low pressure side integrating steam turbine is for 60 cycle, and said final stage blades on the low pressure side each have a blade portion length of at least 83.82 cm. A high and low pressure sides integrating steam turbine according to claim 1, characterized in that said martensite stainless steel has a wholly tempered martensite structure. A high and low pressure sides integrating steam turbine according to claim 1, characterized in that said martensite stainless steel does not substantially include δ ferrite. A high and low pressure sides integrating steam turbine according to claim 1, characterized in that said martensite stainless steel has a ratio of Mn/Ni of 0.11 or less. A high and low pressure sides integrating steam turbine according to claim 1, characterized in that said martensite stainless steel has a Cr equivalent of 4 to 10, which is obtained by the following equation: Cr equivalent = Cr + 6Si + 4Mo + 1.5W + 11V + 5Nb - 40C - 30N - 30B - 2Mn - 4Ni - 2Co + 2.5Ta. A high and low pressure sides integrating steam turbine according to claim 1, characterized in that in said martensite stainless steel, P, S, Sb, Sn and As are suppressed to be 0.015% or less, 0.015% or less, 0.0015% or less, 0.01% or less and 0.02% or less, respectively. A high and low pressure sides integrating steam turbine according to claim 1, characterized in that said rotor shaft (3) is made of a Ni-Cr-Mo-V low alloy steel comprising, by weight percentage, 0.18 to 0.28% C, not more than 0.1% Si, 0.1 to 0.3% Mn, 1.5 to 2.5% Cr, 1.5 to 2.5% Ni, 1 to 2% Mo, 0.1 to 0.35% V, and not more than 0.003% O.

Inventors: HIRAGA RYO, NAKAMURA SHIGEYOSHI, ONODA TAKESHI, SIGA MASAO, HIRAGA, RYO, NAKAMURA, SHIGEYOSHI, ONODA, TAKESHI, SIGA, MASAO
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1997
Main classification: F01D5
IPC codes: F01D25, F01D5, C22C38, F01D1, F01K7