Abstract:
Embodiments of the invention relate generally to welding methods and, more particularly, to methods for welding in a horizontal position and a joint structure suitable for such methods. In one embodiment, the invention provides a method of forming a welded joint between two components, the method comprising: aligning a first and second component to form a joint therebetween, the joint comprising: a protrusion of the first component, and a recess of the second component, wherein the protrusion and recess have complimentary shapes; orienting the first and second components such that a major axis of each is oriented vertically; and welding the first and second components at a substantially horizontally-oriented root opening, the substantially horizontally-oriented root opening positioned along the joint.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Embodiments of the invention relate generally to welding methods and, more particularly, to methods for welding in a horizontal position and a joint structure suitable for such methods. 
         [0002]    The fabrication of steam turbine rotors and similar devices often involves gas-tungsten-arc welding (GTAW) of component parts. GTAW facilitates improved mechanical properties, including the ability to join components having different base materials, as is often desirable in high-performance machines. “Hot wire” GTAW, in which a filler metal is pre-heated to a temperature near its melting point before being introduced into the weld pool, is preferred in many instances because it is generally faster and more efficient than “cold wire” GTAW, which relies entirely on heat from the electric arc to melt the filler metal. 
         [0003]    A deficiency of known GTAW methods, and particularly hot wire GTAW methods, is their limitation to welding in a flat position. That is, such methods involve welding with the electrode facing downward into the weld joint. As such, employing GTAW, and particularly hot wire GTAW, in the fabrication of steam turbine rotors and similar devices generally requires the manipulation and movement of large components in order to properly orient the weld joint. Such manipulation and movement necessarily decreases the efficiency and increases the cost of fabricating the device. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    In one embodiment, the invention provides a method of forming a welded joint between two components, the method comprising: aligning a first and second component to form a joint therebetween, the joint comprising: a protrusion of the first component, and a recess of the second component, wherein the protrusion and recess have complimentary shapes; orienting the first and second components such that a major axis of each is oriented vertically; and welding the first and second components at a substantially horizontally-oriented root opening, the substantially horizontally-oriented root opening positioned along the joint. 
         [0005]    In another embodiment, the invention provides a method of forming a welded joint between two metallic components of a device, the method comprising: obtaining a first component having: a substantially cylindrical body, a mating face along a surface of the body, the mating face including a protrusion, and a concave face extending away from the mating face and toward the body; obtaining a second component having: a substantially cylindrical body, a mating face along a surface of the body, the mating face including a recess having a shape complimentary to a shape of the protrusion of the mating face of the first component, and a concave face extending away from the mating face and toward the body; aligning the first and second components such that the protrusion of the mating face of the first component lies within the recess of the mating face of the second component and the concave faces of the first and second components form a horizontally-oriented root opening along adjacent surfaces of the substantially cylindrical bodies of the first and second components; and welding the first component to the second component across the horizontally-oriented root opening. 
         [0006]    In still another embodiment, the invention provides a turbine rotor comprising: a first component having: a first body, a first mating face along a surface of the first body, the first mating face including a protrusion, and a first concave face extending away from the first mating face and toward the first body; a second component having: a second body, a second mating face along a surface of the second body, the second mating face including a recess having a shape complimentary to a shape of the protrusion of the first mating face, and a second concave face extending away from the second mating face and toward the second body; a root opening between the first and second components formed by the first and second concave faces; and a joint within the root opening, the joint formed by the protrusion and the recess and offset from a center of the root opening. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    These and other features of this invention will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various embodiments of the invention, in which: 
           [0008]      FIG. 1  shows a side cross-sectional view of components of a device suitable for forming a joint structure according to an embodiment of the invention 
           [0009]      FIG. 2  shows the components of  FIG. 1  aligned to form a joint; 
           [0010]      FIG. 3  shows a broader, cross-sectional elevation view of the components of  FIG. 2 ; 
           [0011]      FIG. 4  shows the components of  FIG. 3  being welded according to an embodiment of the invention; 
           [0012]      FIG. 5  shows a cross-sectional elevation view of aligned components according to another embodiment of the invention; and 
           [0013]      FIG. 6  shows a flow diagram of a method according to an embodiment of the invention. 
       
    
    
       [0014]    It is noted that the drawings of the invention are not to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Referring now to the drawings,  FIG. 1  shows a cross-sectional side view of a first component  100  and second component  200  of a steam turbine rotor or similar device. Each of the first and second components  100 ,  200  includes a body  110 ,  210 , a mating face  120 ,  220 , and a concave face  130 ,  230  extending away from the mating face  120 ,  220  toward the body  110 ,  210 , respectively. Mating faces  120 ,  220  are substantially complimentarily shaped, such that they may form a joint structure. As shown in  FIG. 1 , mating face  120  of first component  100  includes a protrusion  122  extending outward from mating face  120 , while mating face  220  of second component  200  includes a recess  222  into which protrusion  122  may reside. 
         [0016]      FIG. 2  shows first component  100  and second component  200  in a joined position and forming a joint  300  according to an embodiment of the invention. As can be seen in  FIG. 2 , concave face  130  of first component  100  and concave face  230  of second component form a root opening  310  (i.e., an opening between the components along which a weld may be formed). First component  100  and second component  200  will ultimately be joined by welding at root opening  310 . As such, deposition of a filler metal into root opening  310  is facilitated by its angled shape. That is, at least a portion of concave face  130  forms an angle α above a horizontal plane  320  and at least a portion of concave face  230  forms an angle β below horizontal plane  320 . Angles α and β are each, independently, between about 0 degrees and about 10 degrees. In some embodiments, each is between about 3 degrees and about 7 degrees. In some embodiments, each is about 5 degrees. As one skilled in the art will understand and as will be described and shown in greater detail below, horizontal plane  320  would lie along or parallel to the radial axes or radial planes of first component  100  and second component  200 . 
         [0017]    As can be seen in  FIG. 2 , joint  300  is offset  330  from the center of root opening  310 , through which horizontal plane  320  lies. That is, the point at which first component  100  and second component  200  meet within root opening  310  is offset from the center of root opening  310 . In  FIG. 2 , offset  300  is displaced toward the component having protrusion  112 , i.e., first component  100 , although this is not essential. 
         [0018]      FIG. 3  shows a broader, elevational view of first component  100  and second component  200  of  FIG. 2 . As can be seen in  FIG. 3 , first component  100  and second component  200  may each include, respectively, a substantially cylindrical or tubular body  110 ,  210  having a bore  150 ,  250 , a longitudinal axis  140 ,  240 , and a plurality of radial axes  142 ,  144  and  242 ,  244 . Although bodies  110  and  210  are described above as substantially cylindrical or tubular, it should be noted that the cross-sectional view of  FIG. 3  shows only arcuate segments of each body. Root opening  310  opens along the outer surfaces  112 ,  212  of first component  100  and second component  200 , respectively. First component  100  and second component  200  each further include an inner surface  114 ,  214  formed along their bores  150 ,  250 , respectively. 
         [0019]      FIG. 4  shows first component  100  and second component  200  in position during welding, wherein their longitudinal axes  140 ,  240  are oriented substantially vertically. Consequently, their radial axes  142 ,  144  and  242 ,  244 , and root opening  310 , are oriented substantially horizontally. 
         [0020]    As noted above, known GTAW methods, and particularly hot wire GTAW methods, are limited to welding in a flat position (i.e., with root opening  310  facing upward). As shown in  FIG. 4 , however, embodiments of the invention permit not only welding in a horizontal position (i.e., with root opening  310  opening substantially horizontally and longitudinal axes  140 ,  240  oriented substantially vertically), but also the use of a plurality of weld heads  700 ,  702 . That is, weld heads  700 ,  702  are capable of simultaneously welding  730  at different points along root opening  310 , with each weld head  700 ,  702  traveling about first and second components  100  while forming a weld  740 . 
         [0021]    In  FIG. 4 , weld head  700  is shown welding  730  along joint  300  as a filler rod  720  deposits a filler metal into root opening  310 . As will be recognized by one skilled in the art, a shielding gas  710 ,  712  protects the welding  730  from atmospheric gasses, such as oxygen and nitrogen. Suitable shielding gasses  710 ,  712  include, but are not limited to, argon, helium, hydrogen, and mixtures thereof. 
         [0022]    The filler metal deposited into root opening  310  will vary, of course, depending on any number of factors, including the materials of which the components are comprised. Suitable filler metals include, but are not limited to: nickel alloy, stainless steel, low alloy steel, high alloy steel, and mixtures thereof. 
         [0023]    As to the composition of the components themselves, one skilled in the art will recognize that any number of materials may be employed and will vary, for example, depending on the application to which the components or the finished device will be put. As such, in some instances, the components themselves may be comprised of different materials. This is often the case, for example, in the case of components employed in steam turbine rotors, where steam of varying temperatures will contact the different components. In such a case, it may be desirable to choose the materials of each component based on the temperature of the steam to which it will be exposed, thereby controlling for such factors as thermal expansion. Non-limiting examples of the materials of which components may independently be comprised include, for example, stainless steel, carbon steel, nickel alloy, low alloy steel, high alloy steel, and mixtures thereof. 
         [0024]      FIG. 5  shows another embodiment of the invention, wherein the root opening  610  opens along the inner surfaces  414 ,  514  of first component  400  and second component  500 , respectively. That is, root opening  610  opens within the bores  450 ,  550  of first component  400  and second component  500 , respectively. As such, forming a weld at joint  600  within root opening  610  requires passing a welding apparatus into one or both bores  450 ,  550 . As in the embodiment shown in  FIG. 4 , welding in a substantially horizontal position using a plurality of weld heads is possible. 
         [0025]      FIG. 6  shows a flow diagram of a method according to an embodiment of the invention. At A, first and second components  100 ,  200  ( FIG. 4 ) are aligned, such that protrusion  122  ( FIG. 1 ) on mating face  120  ( FIG. 1 ) of first component  100  lies within recess  222  ( FIG. 1 ) on mating face  220  ( FIG. 1 ) of second component  200 . Root opening  310  ( FIG. 2 ) is thereby formed by concave faces  130 ,  230  ( FIG. 2 ) of first component  100  and second component  200 . At B, first and second components  100 ,  200  are oriented such that their longitudinal axes  140 ,  240 , respectively, are substantially vertical and their radial axes  142 ,  144  and  242 ,  244  are substantially horizontal. As will be recognized by one skilled in the art the aligning of A and the orienting of B may be performed in either order or together. That is, in some embodiments of the invention, first and second components  100 ,  200  may first be aligned with respect to each other and then oriented such that their longitudinal and radial axes are oriented as described. In other embodiments of the invention, first and second components  100 ,  200  may first be oriented such that their longitudinal and radial axes are oriented as described and then aligned with respect to each other. In still other embodiments of the invention, first and second components  100 ,  200  may be both aligned and oriented at the same time. 
         [0026]    At C, a filler metal may optionally be introduced into root opening  310 . In such a case, the filler metal may optionally be heated to a temperature near its melting point (i.e., hot wire welding) at D. 
         [0027]    Finally, at E, first and second components  100 ,  200  are welded  730  ( FIG. 4 ) along root opening  310 . As noted above, the welding at E may be performed in a substantially horizontal direction, may include a GTAW method, and may include simultaneous welding by a plurality of weld heads  700 ,  702  ( FIG. 4 ). 
         [0028]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0029]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any related or incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.