Patent Application
20110198318
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.
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.
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.
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.
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.
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.
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:
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.
Referring now to the drawings,
As can be seen in
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
In
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.
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.
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.
Finally, at E, first and second components 100, 200 are welded 730 (
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.
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.
