Abstract:
The invention relates to a method for manufacturing a stator component that is intended in operation to guide a gas flow and to transfer loads. The component is constructed of at least two sectors in the direction of its circumference. The sectors are cast in separate pieces, positioned adjacent to each other and joined together by welding.

Description:
BACKGROUND AND SUMMARY  
       [0001]     The present invention relates to a method for manufacturing a stator component that is intended in operation to guide a gas flow and to transfer loads.  
         [0002]     The stator component can, for example, be utilized in a gas turbine and, in particular, in a jet engine.  
         [0003]     By jet engine is meant various types of engine that take in air at a relatively low speed, heat it up by combustion and expel it at a much higher speed. The term jet engine includes, for example, turbo-jet engines and turbo-fan engines.  
         [0004]     Such a stator component that comprises an outer and an inner ring with wall elements arranged between the rings, can be arranged with the aim of primarily being load-transferring in a radial and axial, and also in a tangential, direction. The wall elements can, for example, form hollow blades, which are usually such a shape that they present as little air resistance as possible. The component can, for example, be arranged in a rear or front support, or in an intermediate housing in a jet engine. In such cases, the blades are often called struts. Struts can, however, also be created by other types of part than hollow blades.  
         [0005]     According to a previously-known technique, wall elements in the form of hollow blades are arranged spaced apart in the direction of the circumference of the component between an inner and an outer ring. The joining of the hollow blades to the rings is carried out by welding. Each of the rings is manufactured first with parts projecting in a radial direction that have the same cross-section and dimension as the blades.  
         [0006]     Such projecting parts are often called stubs. Each of the blades is thereafter welded on to such a projecting part using a butt joint. The parts projecting in a radial direction are normally milled out of a ring.  
         [0007]     This is a time-consuming and expensive operation.  
         [0008]     According to another previously-known technique, the whole stator component is cast in a single stage. This requires, however, a large and very complicated casting facility.  
         [0009]     It is desirable to achieve a method for manufacturing a stator component that provides a better weight-optimized component in relation to previously-known techniques, with the same or increased durability and life. In particular, however, a timesaving and more cost-effective manufacturing method is sought.  
         [0010]     According to an aspect of the present invention, the component is constructed of at least two sections in the direction of its circumference, and the sectors are cast in separate pieces, positioned adjacent to each other and joined together by welding.  
         [0011]     As the sectors are cast individually, there are certain advantages in relation to casting the whole stator component in a single step. One advantage is that in the event of a fault or a defect, it is not necessary to reject a whole stator component, but only one sector. An additional advantage is that the casting is less complex, with smaller parts of a less complicated design.  
         [0012]     According to an aspect of the invention, the surface of each of the sectors that is intended to be welded is continuous. In other words, the welding surface has no interruptions or sudden changes in direction. By this means, it is possible to have an efficient welding process that provides a highly durable welded joint. In addition, the surface of each of the sectors that is intended to be welded is essentially of the same thickness in cross-section over the length of the whole surface. By this means, there is considerably less need to change the welding parameters during the welding process.  
         [0013]     According to another aspect of the invention, other parts of the sector adjacent to the surface that is intended to be welded are set back slightly in the direction of the circumference relative to the welding surface in order not to interfere with the weld path. This applies, in particular, when the sectors are cast in such a shape that they each have at least one rib that extends in the direction of the circumference and projects in an axial direction. The sector is then cast in such a shape that the the rib extends in such a way that there is a gap in the direction of the circumference between the end of the rib and the edge of the sector. This makes it possible to join the sectors together in a simple way after the sectors have been placed adjacent to each other. After the sectors have been placed adjacent to each other in the direction of the circumference, the sectors are thus joined by welding together the sectors&#39; adjacent edges between the ends of the ribs in a radial direction.  
         [0014]     According to a further aspect of the invention, after the the welding together, the space between two adjacent rib edges is filled by deposition of material so that the ribs form a continuous structure in the direction of the circumference. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The invention will be described in greater detail in the following, with reference to the embodiment that is shown in the attached drawings, in which  
         [0016]      FIG. 1  shows a cast sector in perspective view,  
         [0017]      FIG. 2  shows the stator component constructed of a plurality of sectors according to  FIG. 1  in the direction of its circumference, and  
         [0018]      FIG. 3  shows an enlarged view of a part of the component according to  FIG. 2 , and more specifically the dividing area between two sectors, where the ribs of two adjacent sectors have been joined together by the deposition of metallic material. 
     
    
     DETAILED DESCRIPTION  
       [0019]      FIG. 1  shows a cast sector  1  in a perspective view.  
         [0020]     The sector  1  has a gas duct  2  that goes right through, principally in an axial direction. It is also possible to have one or more gas ducts in a radial direction for compressor flow (not shown), and also in certain cases fan flow.  
         [0021]     The sector  1  has been cast with wall elements  4 ,  5 ,  6 ,  7 ,  8  that form a continuous structure in the radial direction in order to transfer loads. In the illustrated embodiment, the sector  1  comprises a first wall element  3  and a second wall element  4 , which extend in the intended radial direction of the stator component and are arranged at a distance from each other in order to define between them the gas duct  2  in the direction of the circumference of the stator component.  
         [0022]     When two sectors are joined together, the continuous wall structure  4 ,  5 ,  6 ,  7 ,  8  together with a corresponding wall structure  21  of an adjacent sector form a device  11  extending in the radial direction of the component for guiding the the gas flow and transferring loads in a radial/axial/tangential direction during operation of the component, see  FIG. 2 . This device  11  for guiding/load transference is usually called a strut. In the illustrated embodiment, the division between two adjacent sectors is thus made straight through such a strut. For certain applications, it can, however, be more appropriate to make the division between the struts. According to the illustrated embodiment, however, the stator component comprises such a complicated inner hub section that the only reasonable division is to go through the struts.  
         [0023]     The sector  1  comprises, in addition, a third wall element  5 , that extends between the first wall element  3  and the second wall element  4  and defines the gas duct  2  radially outwards. The sector  1  comprises, in addition, a fourth wall element  6  that extends between the first wall element  3  and the second wall element  4  and defines the gas duct radially inwards.  
         [0024]     The ends  9 ,  10  of the sector  1  in the direction of the circumference have a design that complements the ends of the adjacent sector, in order that, when they are placed next to each other, they will at least essentially fit tightly against each other. The ends  9 ,  10  in the direction of the circumference have, more specifically, a rectilinear delimitation in the radial direction. As a result of this design, two adjacent sectors can be joined together in the direction of the circumference in a relatively easy way from the outside.  
         [0025]     Each of the ends  9 ,  10  of the sector  1  comprises an elongated continuous surface  22 ,  23 ,  24 ,  25 ,  26  which delimits the sector  1  in the direction of the circumference and which is intended to be welded. The welding surface extends at least partially around the sector body at the periphery of the sector. The welding surface comprises a first section  22  which extends principally in a radial direction, a second section  23  which extends principally in an axial direction, and a third section  24  which extends principally in a radial direction. The welding is carried out in one continuous operation, from a boss  12  at an outer end of the welding surface in a radial direction, radially inwards, thereafter axially and finally radially outwards, back to the boss  12 . The welding surface thus forms essentially a U shape. Each of the parts  25 ,  26  of the welding surface that form a change of direction between radial and axial direction is evenly rounded off. In addition, the welding surface is essentially of the same thickness in cross section over the whole length of the surface. The welding surface can thus be the to constitute one continuous curve.  
         [0026]     Other parts of the sector adjacent to the surface that is intended to be welded are set back slightly in the direction of the circumference relative to the welding surface in order not to interfere with the weld path.  
         [0027]     Examples of such parts are the edges of the third and fourth wall elements  5 ,  6  in the direction of the circumference.  
         [0028]     Several different welding methods are possible, but preferably laser or electron beam welding are used. The first and the second wall elements  3 ,  4  thus extend essentially in the radial direction of the component  1 .  
         [0029]     In addition, they have an extent essentially in the axial direction of the component.  
         [0030]     In addition, the sector  1  has a curved plate  14  for delimiting the sector radially inwards and a curved plate  15  for delimiting the sector radially outwards.  
         [0031]     The sector  1  is cast in such a shape that it has at least one rib  16 ,  17 , see  FIG. 1 , which extends in the direction of the circumference and projects in an axial direction. The ribs  16 ,  17  extend different distances in the radial direction. In addition, there is a gap in the direction of the circumference between the end  18  of the rib  17  and the edge  19  of the sector, see  FIG. 3 . This is in order to make the welding surface accessible for the welding process.  
         [0032]     After the positioning of the sectors next to each other in the direction of the circumference, see  FIG. 2 , the sectors are thus joined by welding the sectors&#39; adjacent edges  19  between the ends  18 ,  18 ′ of the ribs in a radial direction. Due to the design of the sectors described above, it is possible to weld the dividing line between two adjacent sectors. This is carried out, as mentioned above, preferably in one continuous run per weld path.  
         [0033]     After the the joining together, the space between two adjacent rib edges  18 ,  18 ′ is filled by deposition of metallic material  21  so that the ribs form a continuous structure in the direction of the circumference. The continuous rib structure in the direction of the circumference forms a reinforcing structure in the form of a circular flange, and is used to make a joint in an axial direction to adjacent parts and/or to bearings and seals in the gas turbine.  
         [0034]     A plurality of identical sections  1 ,  20 , or sections that have different shapes but identical cross-sections, manufactured according to the description above, are thus arranged alongside each other, see  FIG. 2 .  
         [0035]     The stator component can, for example, forma load bearing structure between bearings arranged radially or axially internally and structures attached externally.  
         [0036]     During the welding together, a space is created between two wall elements of two adjacent sectors. These spaces can now be used to house various means for supplying the component with, for example, oil and/or air, such as intakes and outlets, for housing instruments, such as electrical and metallic cables for transmission of information relating to measured pressure and/or temperature. The spaces can also be used for the introduction of coolants.  
         [0037]     The stator component can, for example, form an intake part, an intermediate housing, a turbine exhaust housing (that is, a terminating housing part), or a part of a housing for a gas turbine. Its main task is acting as an attachment for bearings, transferring loads, and providing a duct for gasses.  
         [0038]     In the present application, the use of terms such as “including” is open-ended and is intended to have the same meaning as terms such as “comprising” and not preclude the presence of other structure, material, or acts. Similarly, though the use of terms such as “can” or “may” is intended to be open-ended and to reflect that structure, material, or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or acts are presently considered to be essential, they are identified as such.  
         [0039]     The invention is not to be regarded as being limited to the embodiments described above, a number of additional variants and modifications being possible within the framework of the following claims.