Patent Application
20190061035
The disclosure relates generally to joining components together and more specifically to a system and method useful for joining components using a filler material.
The joining of metal components, such as by using brazing, involves preparation of the bonding surfaces, positioning the components closely together, and applying heat to a joint area and a brazing filler metal compound. The filler metal when molten is drawn into the joint gap between the bonding surfaces by liquid surface tension and capillary action. After filling, metal components and brazing metal is cooled. The preparation of the bonding surfaces may include machining, grinding or applying of flux.
Positioning the components relative to each other may include an assembly jig or fixture so that a gap suitable for brazing is provided. Another approach can be the use tack welds on exposed outer surfaces of the components using spot welding, arc welding, TIG welding with wire consumables or ball-tacking for example. Tack welds used to hold components during brazing can create stress concentrations due to the residual thermal stresses and due to abrupt transitions between the weld and the metal components joined. Removal of tack welds or grinding welds smooth is sometimes necessary to preserve the shape of the surfaces of the metal components and to reduce stress concentrations. It can be difficult to obtain a relatively uniform gap between the components that is suitable for brazing using existing approaches for positioning the components relative to each other in preparation for brazing.
In one aspect, the disclosure describes a method of joining two components at bonding surfaces, the components including one or more weld projections extending a weld projection height from at least one of the bonding surfaces and including one or more spacer projections extending a spacer projection height from at least one of the bonding surfaces, the weld projection height being greater than the spacer projection height. The method comprises:
contacting the one or more weld projections of one component with the other component;
projection welding the components together by:
melting a distal portion of each of the one or more weld projections; and
deforming the one or more distal portions of the one or more weld projections against the other component; and
ceasing the projection welding of the components when the one or more spacer projections of one component contact the other component, the one or more spacer projections defining a gap between the bonding surfaces.
The method may comprise, after ceasing the projection welding, brazing the components together using a brazing material at least partially filling the gap defined between the bonding surfaces.
In some embodiments, at least one of the bonding surfaces is planar.
In some embodiments, at least one of the bonding surfaces is curved.
The one or more weld projections may have a conical shape, cylindrical shape or pyramidal shape.
The one or more weld projections may comprise a rib.
The one or more spacer projections may have a semi-spherical shape.
The method may comprise:
conducting electric current from one component to the other component via the one or more weld projections to cause melting of the one or more weld projections; and
urging the two components toward each other when deforming the one or more distal portions of the one or more weld projections.
The method may comprise, after ceasing the projection welding, joining the components together using a filler material at least partially filling the gap defined between the bonding surfaces.
Embodiments may include combinations of the above features.
In one aspect, the disclosure describes a method of joining two components at bonding surfaces, a first component including a weld projection extending a weld projection height from a first bonding surface of the first component, the first component or a second component including a spacer projection extending a spacer projection height from the first bonding surface or from a second bonding surface of the second component, the weld projection height being greater than the spacer projection height. The method may comprise:
contacting the weld projection of the first component with the second component;
projection welding the first and second components together by:
melting a distal portion of the weld projection; and
deforming the distal portion of the weld projection against the second component; and
ceasing the projection welding of the first and second components when the spacer projection of the first or second component contacts the other of the first or second component, the spacer projection defining a gap between the first and second bonding surfaces.
The method may comprise, after ceasing the projection welding, joining the components together using a filler material at least partially filling the gap defined between the first and second bonding surfaces.
The method may comprise passing electric current between the first component and the second component via the weld projection to cause melting of the weld projection.
Embodiments may include combinations of the above features.
In one aspect, the disclosure describes a system for joining of first and second components. The system comprises:
one or more weld projections extending from the first component, the one or more weld projections extending a weld projection height from a bonding surface of the first component; and
one or more spacer projections extending from at least one of the first and second components, the one or more spacer projections extending a spacer projection height from at least one of the bonding surface of the first component and the bonding surface of the second component;
wherein the weld projection height is greater than the spacer projection height and the one or more spacer projections are sized to define a desired brazing gap between the bonding surfaces of the first and second components after welding deforms the weld projections.
In some embodiments, at least one of the bonding surfaces is planar.
In some embodiments, at least one of the bonding surfaces is curved.
The one or more weld projections may have a conical shape, cylindrical shape or pyramidal shape.
The one or more weld projections may comprise a rib.
The one or more spacer projections may have a semi-spherical shape.
Embodiments may include combinations of the above features.
Further details of these and other aspects of the subject matter of this application will be apparent from the detailed description included below and the drawings.
The following describes a system and method of joining two components each having a bonding surface using a combination of projection welding and brazing or soldering. In various embodiments, either or both components can have one or more weld projections that are used to tack weld the components together using projection welding. Either or both components can have one or more spacer projections that are used to define a desired gap between the two components after the projection welding so as to facilitate subsequent joining of the two components using a filler material at least partially filling the gap defined between the two components. In some embodiments, the system and method disclosed herein can be used to join parts of gas turbine engines. For example, such parts can include fuel injector pads being joined to a surface of a combustor wall of the gas turbine engine.
Projection welding is a form of resistance welding that does not use consumable filler metals such as wire, rods, flux or other welding consumables. Resistance welding creates localized heat by passing electric current through relatively small contact zones of the (e.g., metallic, electrically conductive) components to be joined together to cause melting at the contact zones via Joule heating. Projection welding is a variation of resistance welding where projections of suitable shape(s) are formed on at least one bonding surface or other part(s) of one or both components. The components are clamped together with the projections contacting the bonding (or other) surface of the other component. Electrical current passing between the components takes the path of least resistance through the projections in contact with the other component. The metal of the heated projection softens (i.e., melts) and the contact surface of the other metal component softens due to the heat caused by electric resistance. The components are urged together such that the softened metals of the projection and the adjacent surface fuse (i.e., weld) the components together when cooled.
Referring to the detailed view in
As indicated in
Those skilled in the art will be familiar with various spot and projection welding machines as well as fixtures that perform the functions of: securing the two components 1, 2 in position relative to each other; passing electric current between the two components 1, 2 or workpieces; urging/moving the two components 1, 2 together as materials are heated and melted; and terminating the passing of the electric current and motion when the resistance welding cycle has been completed. Therefore it is not considered necessary to explain the fixture or welding equipment in detail herein.
In the starting position shown in
In the position shown in
As indicated in
As indicated in
As indicated in
Alternatively, brazing filler alloy 12 could be in the form of a preformed sheet (not shown) disposed in the gap 11 in the position shown in
Brazing can be conducted in a batch process in an oven or autoclave under controlled pressure. In such circumstance projection tack welding is completed separately and final brazing occurs later in a separate oven or autoclave. In either case, after brazing is completed the joined components 1, 2 can be cooled to permit solidification of all the heated materials.
As apparent from the finished assembly of components 1, 2 shown in
The ceasing the projection welding of the components 1, 2 when the spacer projections 4 of one component 1 or 2 contact the other (i.e., opposite) component 1 or 2 can be done in any suitable way. For example, during projection welding, the electric current setting can be determined based on the number and configuration of weld projections 3 to be welded and set accordingly. This setting can be determined experimentally and can be used repeatedly for projection welding components 1, 2 of similar geometries. Power and time for projection welding can be determined experimentally to ensure that the spacer projections 4 will at least get in contact with the other component 1 or 2 during projection welding. As the gap 11 (see
Some resistance welding controllers can use power electronics that are able to detect component displacements and also changes in electrical resistance such as the sudden change in electrical resistance associated with the spacer projections 4 coming in contact with the other component 1 or 2. In some embodiments, suitable closed loop control approaches can be used to cease the projection welding process at the appropriate time.
7B shows weld projections 3 extending from both bonding surfaces 5 and 6, and also spacer projections 4 extending from both bonding surfaces 5 and 6. Based on the present disclosure, it will be understood that projections 3 and/or 4 need not necessarily project directly from corresponding bonding surfaces 5, 6. For example, even though the weld projection height and the spacer projection height may be measured relative to bonding surface(s) 5, 6, projections 3 and/or 4 may be connected and extend from other (i.e., non-bonding) surface(s) of components 1 and/or 2 in some embodiments.
The above description is meant to be exemplary only, and one skilled in the relevant arts will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. The present disclosure may be embodied in other specific forms without departing from the subject matter of the claims.
