Abstract:
A steam turbine vane manufacturing method including: a groove processing step for forming a protective part connecting surface ( 14 ) on a steam turbine vane material ( 11 ) that was subjected to rough processing; a build-up welding step for forming, by build-up welding, a protective part build-up bead ( 15 ) on the protective part connecting surface ( 14 ); and a processing step for performing processing, by cutting the steam turbine vane material ( 11 ) that was subjected to rough processing and the protective part build-up bead ( 15 ), to finish the steam turbine vane material ( 11 ) that was subjected to rough processing so that the same becomes a steam turbine vane material ( 16 ) that was subjected to finishing processing. In this case, the steam turbine vane material ( 11 ) that was subjected to rough processing is larger than the steam turbine vane material ( 16 ) that was subjected to finishing processing.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a steam turbine vane manufacturing method and in particular, to a steam turbine vane manufacturing method which is utilized when producing a steam turbine vane with which a steam turbine is provided. 
       BACKGROUND ART 
       [0002]    A steam turbine is known which generates power by receiving high-temperature and high-pressure steam in a steam turbine vane. Water droplets contained in the steam come into contact with the steam turbine vane, whereby erosion sometimes occurs (refer to PTL 1). 
       CITATION LIST 
     Patent Literature 
       [0003]    [PTL 1] Japanese Unexamined Patent Application Publication No. 2008-190039 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    A measure against erosion is known which prevents erosion of a main body portion of a steam turbine vane by forming a protective part at a portion of the steam turbine vane. It is desirable to appropriately manufacture the steam turbine vane with such a measure against erosion applied thereto. 
         [0005]    An object of the present invention is to provide a steam turbine vane manufacturing method of appropriately manufacturing a steam turbine vane. 
       Solution to Problem 
       [0006]    According to a first aspect of the present invention, there is provided a steam turbine vane manufacturing method including: a groove processing step of forming a protective part joint surface in a steam turbine vane material; a build-up welding step of forming a protective part build-up bead on the protective part joint surface by build-up welding; and a processing step of processing the steam turbine vane material into a steam turbine vane by cutting the protective part build-up bead along with the steam turbine vane material. 
         [0007]    At this time, the steam turbine vane material is larger than a steam turbine vane material after finishing processing in which a steam turbine vane material has been subjected to finishing processing, and thus is not easily deformed by heat input due to build-up welding, as compared to the steam turbine vane material after finishing processing. For this reason, in such a steam turbine vane manufacturing method, as compared to another steam turbine vane manufacturing method in which a protective part build-up bead is formed after a steam turbine vane material is subjected to finishing processing, it is possible to reduce the deformation amount of the steam turbine vane material which is deformed by build-up welding, and thus it is possible to appropriately manufacture a steam turbine vane. 
         [0008]    The steam turbine vane manufacturing method according to the first aspect further includes: a forging step of manufacturing the steam turbine vane material by forging. 
         [0009]    The steam turbine vane material manufactured by forging is larger than a steam turbine vane material after rough processing formed by performing cutting on a forged part, and thus is not easily deformed by heat input due to build-up welding. For this reason, in such a steam turbine vane manufacturing method, as compared to another steam turbine vane manufacturing method in which a protective part build-up bead is formed on a protective part joint surface which is formed in the steam turbine vane material after rough processing, it is possible to reduce the deformation amount of the steam turbine vane material which is deformed by build-up welding, and thus it is possible to appropriately manufacture a steam turbine vane. 
         [0010]    The steam turbine vane manufacturing method according to the first aspect further includes: an aging treatment step of performing aging treatment on the steam turbine vane material along with the protective part build-up bead before the processing step is carried out. 
         [0011]    According to such a steam turbine vane manufacturing method, the steam turbine vane material is hardened by being subjected to aging treatment, and thus it is possible to easily perform straightening on the steam turbine vane material before it is cut, and thus it is possible to easily manufacture a steam turbine vane. 
         [0012]    According to a second aspect of the present invention, there is provided a steam turbine vane which is manufactured by carrying out the steam turbine vane manufacturing method according to the present invention. In such a steam turbine vane, as compared to another steam turbine vane in which a protective part build-up bead is formed after a steam turbine vane material is subjected to finishing processing, it is possible to reduce the deformation amount of the steam turbine vane material which is deformed by build-up welding, and thus it is possible to appropriately manufacture the steam turbine vane. 
       Advantageous Effects of Invention 
       [0013]    According to the steam turbine vane manufacturing method according to the present invention, by performing finishing processing on the steam turbine vane material after build-up welding, it is possible to reduce the deformation amount of the steam turbine vane material which is deformed by build-up welding, and thus it is possible to appropriately manufacture a steam turbine vane. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a perspective view showing a steam turbine vane. 
           [0015]      FIG. 2  is a flowchart showing an embodiment of a steam turbine vane manufacturing method. 
           [0016]      FIG. 3  is a cross-sectional view showing a steam turbine vane material. 
           [0017]      FIG. 4  is a flowchart showing another embodiment of the steam turbine vane manufacturing method. 
           [0018]      FIG. 5  is a cross-sectional view showing another steam turbine vane material. 
           [0019]      FIG. 6  is a flowchart showing still another embodiment of the steam turbine vane manufacturing method. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0020]    An embodiment of a steam turbine vane according to the present invention will be described below with reference to the drawings. A steam turbine vane  1  is utilized in a steam turbine and provided with a root section  2  and an aerofoil profile section  3 , as shown in  FIG. 1 . The root section  2  is mounted on a rotor of a steam turbine. The aerofoil profile section  3  is formed in an aerofoil profile and fixed to the root section  2 . The aerofoil profile section  3  is exposed to steam flowing through the steam turbine when the root section  2  is mounted on the rotor of the steam turbine. 
         [0021]    The aerofoil profile section  3  is provided with a main body portion  5  and a protective part  6 . The main body portion  5  is formed in a substantially aerofoil profile and formed integrally with the root section  2 , thereby being fixed to the root section  2 . The protective part  6  is formed of Stellite (registered trademark). The protective part  6  is joined to the main body portion  5  so as to form a leading edge portion of an airfoil tip of the aerofoil profile section  3 . 
         [0022]    An embodiment of a steam turbine vane manufacturing method is utilized when manufacturing the steam turbine vane  1 . In the steam turbine vane manufacturing method, first, as shown in  FIG. 2 , a steam turbine vane material after forging is manufactured by forging a solid metal blank (Step S 1 ). The steam turbine vane material after forging is formed in a predetermined shape with high accuracy by being further subjected to coining. After the coining, the steam turbine vane material after forging is formed in a predetermined shape with higher accuracy by being subjected to hot straightening (Step S 2 ). 
         [0023]    After the hot straightening, the steam turbine vane material after forging is subjected to solution heat treatment. After the solution heat treatment, the steam turbine vane material after forging is subjected to stabilization heat treatment (Step S 3 ). After the heat treatment, the steam turbine vane material after forging is further subjected to aging treatment, thereby being hardened (Step S 4 ). 
         [0024]    After the aging treatment, the steam turbine vane material after forging is subjected to straightening so as to be formed in a predetermined shape. After the straightening, the steam turbine vane material after forging is subjected to cutting, thereby being formed into a steam turbine vane material after rough processing (Step S 5 ). As shown in  FIG. 3 , most of the surface formed in a steam turbine vane material after forging  12  is removed by cutting, and thus a steam turbine vane material after rough processing  11  is smaller than the steam turbine vane material after forging  12 . 
         [0025]    The steam turbine vane material after rough processing  11  is further subjected to cutting, whereby a protective part joint surface  14  is formed (Step S 6 ). The protective part joint surface  14  is formed in an area corresponding to a leading edge portion of the steam turbine vane  1 , of the steam turbine vane material after rough processing  11 , and formed to be concave. 
         [0026]    In the steam turbine vane material after rough processing  11 , after the protective part joint surface  14  is formed, filler metal which contains Stellite (registered trademark) is buildup-welded to the protective part joint surface  14  by using a laser beam which is emitted from a CO 2  laser. In the steam turbine vane material after rough processing  11 , a protective part build-up bead  15  is formed by the build-up welding (Step S 7 ). For this reason, the protective part build-up bead is formed of Stellite (registered trademark) and solidly joined to the protective part joint surface  14 . The protective part build-up bead  15  is formed in an area corresponding to the leading edge portion of the steam turbine vane  1 , of the steam turbine vane material after rough processing  11 , and formed as a projection. 
         [0027]    After the protective part build-up bead  15  is formed, the steam turbine vane material after rough processing  11  is subjected to straightening so as to be formed in a predetermined shape. After the straightening, the steam turbine vane material after rough processing  11  is subjected to cutting, thereby being formed into a steam turbine vane material after finishing processing  16  (Step S 8 ). The steam turbine vane material after finishing processing  16  is formed such that most of the surface of the steam turbine vane material after rough processing  11  is removed and such that most of the surface of the protective part build-up bead  15  is removed. For this reason, the steam turbine vane material after finishing processing  16  is smaller than the steam turbine vane material after rough processing  11 . The steam turbine vane material after finishing processing  16  is subjected to polishing, thereby being formed into the steam turbine vane  1  (Step S 9 ). The steam turbine vane  1  is manufactured in this manner, whereby a portion of the protective part build-up bead  15  is formed into the protective part  6 . 
         [0028]    In a comparative example of the steam turbine vane manufacturing method, the steam turbine vane  1  is manufactured by joining a Stellite plate to the protective part joint surface  14  of the steam turbine vane material after finishing processing  16  by brazing. In a case of joining the Stellite plate to the protective part joint surface  14  by brazing, it is necessary for the protective part joint surface  14  to be sufficiently heated, and thus it is necessary to heat the surface on the side opposite to the protective part joint surface  14 , of a base material. For this reason, the amount of heat which is input to the base material due to the brazing is relatively large. 
         [0029]    In this steam turbine vane manufacturing method, the protective part build-up bead  15  is formed by build-up welding, whereby it is not necessary to heat the surface on the side opposite to the protective part joint surface  14 , of the steam turbine vane material after rough processing  11 . For this reason, in this steam turbine vane manufacturing method, as compared to the steam turbine vane manufacturing method of the comparative example in which the steam turbine vane is manufactured by joining the Stellite plate to the protective part joint surface  14  by brazing, it is possible to reduce the amount of heat which is input to the steam turbine vane material after rough processing  11 . As a result, in this steam turbine vane manufacturing method, as compared to the comparative example, it is possible to reduce the deformation amount of the steam turbine vane material after rough processing  11 , and thus it is possible to more appropriately manufacture the steam turbine vane  1 . 
         [0030]    The deformation amount of a relatively large base material which is deformed by build-up welding is smaller than the deformation amount of a relatively small base material which is deformed by build-up welding. For this reason, in this steam turbine vane manufacturing method, the protective part build-up bead  15  is formed on the protective part joint surface  14  of the steam turbine vane material after rough processing  11 , whereby the deformation amount of the base material can be reduced, as compared to a case of forming the protective part build-up bead  15  on the protective part joint surface  14  of the steam turbine vane material after finishing processing  16 . As a result, in this steam turbine vane manufacturing method, it is possible to more appropriately manufacture the steam turbine vane  1 , as compared to another steam turbine vane manufacturing method in which build-up welding is performed on the steam turbine vane material after finishing processing  16 . 
         [0031]      FIG. 4  shows another embodiment of the steam turbine vane manufacturing method according to the present invention. In the steam turbine vane manufacturing method, first, in the same manner as in the steam turbine vane manufacturing method shown in  FIG. 2 , a steam turbine vane material after forging is manufactured by forging a solid metal blank (Step S 11 ) and then subjected to coining and hot straightening (Step S 12 ). 
         [0032]    After the hot straightening, a steam turbine vane material after forging  21  is subjected to cutting, as shown in  FIG. 5 , whereby a protective part joint surface is formed (Step S 13 ). In the steam turbine vane material after forging  21 , after the protective part joint surface  22  is formed, the protective part joint surface  22  is subjected to build-up welded, whereby a protective part build-up bead  23  is formed (Step S 14 ). 
         [0033]    After the protective part build-up bead  23  is formed, the steam turbine vane material after forging  21  is subjected to solution heat treatment and subjected to stabilization heat treatment (Step S 15 ). After the heat treatment, the steam turbine vane material after forging  21  is subjected to straightening so as to be formed in a predetermined shape. After the straightening, the steam turbine vane material after forging  21  is subjected to cutting, thereby being formed into a steam turbine vane material after rough processing  24  (Step S 16 ). 
         [0034]    The steam turbine vane material after rough processing  24  is subjected to aging treatment (Step S 17 ). After the aging treatment, the steam turbine vane material after rough processing  24  is subjected to straightening so as to be formed in a predetermined shape. After the straightening, the steam turbine vane material after rough processing  24  is subjected to cutting, thereby being formed into a steam turbine vane material after finishing processing  25  (Step S 18 ). The steam turbine vane material after finishing processing  25  is subjected to polishing, thereby being formed into the steam turbine vane  1  (Step S 19 ). The steam turbine vane  1  is manufactured in this manner, whereby a portion of the protective part build-up bead  23  is formed into the protective part  6 . 
         [0035]    In the steam turbine vane material after forging  21  with the protective part joint surface  22  formed therein, a portion of the surface formed by forging remains, and thus the steam turbine vane material after forging  21  is larger than the steam turbine vane material after rough processing  11  in the above-described embodiment. For this reason, the deformation amount of the steam turbine vane material after forging  21  which is deformed by build-up welding is smaller than the deformation amount of the steam turbine vane material after rough processing  11  which is deformed by build-up welding. In this steam turbine vane manufacturing method, as compared to the steam turbine vane manufacturing method in the above-described embodiment, it is possible to more appropriately manufacture the steam turbine vane  1 . 
         [0036]      FIG. 6  shows still another embodiment of the steam turbine vane manufacturing method according to the present invention. In the steam turbine vane manufacturing method, first, in the same manner as in the steam turbine vane manufacturing method shown in  FIG. 4 , the steam turbine vane material after forging  21  is manufactured by forging a solid metal blank (Step S 21 ) and then subjected to coining and hot straightening (Step S 22 ), whereby the protective part joint surface  22  is formed (Step S 23 ). 
         [0037]    After the protective part joint surface  22  is formed, the steam turbine vane material after forging  21  is subjected to solution heat treatment and subjected to stabilization heat treatment (Step S 24 ). After the heat treatment, in the steam turbine vane material after forging  21 , the protective part joint surface  22  is subjected to build-up welding, whereby the protective part build-up bead  23  is formed (Step S 25 ). 
         [0038]    After the protective part build-up bead  23  is formed, the steam turbine vane material after forging  21  is subjected to aging treatment (Step S 26 ). After the aging treatment, the steam turbine vane material after forging  21  is subjected to straightening so as to be formed in a predetermined shape. After the straightening, the steam turbine vane material after forging  21  is subjected to cutting, thereby being formed into the steam turbine vane material after rough processing  24  (Step S 27 ). 
         [0039]    The steam turbine vane material after rough processing  24  is subjected to straightening so as to be formed in a predetermined shape. After the straightening, the steam turbine vane material after rough processing  24  is subjected to cutting, thereby being formed into the steam turbine vane material after finishing processing  25  (Step S 28 ). The steam turbine vane material after finishing processing  25  is subjected to polishing, thereby being formed into the steam turbine vane  1  (Step S 29 ). The steam turbine vane  1  is manufactured in this manner, whereby a portion of the protective part build-up bead  23  is formed into the protective part  6 . 
         [0040]    Also in this steam turbine vane manufacturing method, it is possible to appropriately manufacture the steam turbine vane  1 , in the same manner as in the above-described steam turbine vane manufacturing method shown in  FIG. 4 . In general, the higher the hardness of the steam turbine vane material after forging  21 , the easier the straightening for forming the steam turbine vane material after forging  21  into a predetermined shape. According to this steam turbine vane manufacturing method, the steam turbine vane material after forging  21  is subjected to aging treatment and then subjected to straightening so as to be formed in a predetermined shape, whereby the hardness of the steam turbine vane material after forging  21  immediately before it is subjected to rough processing is higher, as compared to the above-described steam turbine vane manufacturing method shown in  FIG. 4 . For this reason, according to this steam turbine vane manufacturing method, it is possible to more easily manufacture the steam turbine vane  1 , as compared to the steam turbine vane manufacturing method shown in  FIG. 4 . 
         [0041]    In addition, the protective part  6  can be formed of a material which is different from Stellite (registered trademark). The material is a material having superior erosion resistance to a material for forming the main body portion  5 , and for example, austenitic stainless steel is exemplified. Also in a steam turbine vane manufacturing method in which such a material is utilized, it is possible to more easily manufacture the steam turbine vane  1 , in the same manner as in the steam turbine vane manufacturing methods in the above-described embodiments. 
         [0042]    In addition, the laser beam which is utilized in the build-up welding can be replaced by another laser beam which is emitted from a laser oscillator which is different from the CO 2  laser. As the laser oscillator, a YAG laser, a laser diode (LD), or the like is exemplified. In addition, the build-up welding can also be carried out by welding which is different from laser welding. As the welding, TIG welding is exemplified. Also in a steam turbine vane manufacturing method to which such welding is applied, it is possible to appropriately manufacture the steam turbine vane  1 , in the same manner as in the steam turbine vane manufacturing methods in the above-described embodiments. 
       REFERENCE SIGNS LIST 
       [0043]      1 : steam turbine vane 
         [0044]      2 : root section 
         [0045]      3 : aerofoil profile section 
         [0046]      5 : main body portion 
         [0047]      6 : protective part 
         [0048]      11 : steam turbine vane material after rough processing 
         [0049]      12 : steam turbine vane material after forging 
         [0050]      14 : protective part joint surface 
         [0051]      15 : protective part build-up bead 
         [0052]      16 : steam turbine vane material after finishing processing 
         [0053]      21 : steam turbine vane material after forging 
         [0054]      22 : protective part joint surface 
         [0055]      23 : protective part build-up bead 
         [0056]      24 : steam turbine vane material after rough processing 
         [0057]      25 : steam turbine vane material after finishing processing