Welding method and apparatus

A welding apparatus for welding a work-piece includes an energy source configured to generate a weld in a zone of the work-piece, with the work-piece characterized by a layer. The apparatus also includes a first wheel characterized by a first circumference and a first set of protrusions disposed on the first circumference, and a second wheel characterized by a second circumference and a second set of protrusions disposed on the second circumference. Each of the first and second wheels is configured to rotate relative to the work-piece, and the first and second sets of protrusions are configured to disrupt the layer as the work-piece is traversed between the first and second wheels. The energy source generates the weld in the zone of the work-piece following the disruption of the layer. A method employing the disclosed welding apparatus is also provided.

TECHNICAL FIELD

The invention relates to a method and an apparatus for welding of components.

BACKGROUND

Welding is a fabrication or process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the work-piece and/or adding a filler material to form a pool of molten material, a.k.a., the weld pool. After the weld pool cools, a high strength joint is produced.

The quality, and therefore the strength of the welded joint is closely related to surface conditions of the work-piece, such as contamination and oxide formation on the surface of the substrates. Furthermore, depending on the type and quality of the materials sought to be joined, the same welding process may expend/consume vastly different amounts of energy to generate a robust weld.

A welding process that expends more energy may require larger, heavier, more powerful, and thus more expensive welding equipment. Such increased consumption of welding energy tends to reduce the overall efficiency of the welding operation, and, coupled with the higher cost and footprint of the welding equipment, tends to increase the effective cost of the finished assembly.

SUMMARY

A welding apparatus for welding a work-piece includes an energy source configured to generate a weld in a zone of the work-piece, with the work-piece characterized by a layer. The apparatus also includes a first wheel characterized by a first circumference and a first set of protrusions disposed on the first circumference, and a second wheel characterized by a second circumference and a second set of protrusions disposed on the second circumference. Each of the first and second wheels is configured to rotate relative to the work-piece, and the first and second sets of protrusions are configured to disrupt the layer as the work-piece is traversed between the first and second wheels. The energy source generates the weld in the zone of the work-piece following the disruption of the layer.

At least one of the first and second wheels may be configured to vibrate at a predetermined frequency, wherein the predetermined frequency may be in the range of approximately 20-40 KHz.

The welding apparatus may also include a controller configured to regulate the traversal of the work-piece between the first and second wheels and regulate the energy source to generate the weld. The welding apparatus may additionally include a fixture configured to move the work-piece relative to the first and second wheels such that the first and second wheels are caused to rotate relative to the work-piece, wherein the controller may regulate the fixture. Furthermore, the welding apparatus may include a mechanism configured to rotate at least one of the first and second wheels such that the work-piece is caused to traverse relative to the first and second wheels, wherein the controller may regulate the mechanism.

The energy source may be configured as one of a laser beam, an electron beam, a plasma beam, a welding arc, and a hybrid energy source such as a laser/arc.

The work-piece may include adjacent substrates that contact at an interface, such that the zone is formed at the interface. At least one of the substrates may be formed from one of a ferrous and a non-ferrous material such as steel, aluminum, and magnesium.

The layer may include an oxide coating and/or material contaminants disposed on the surface of at least one of the adjacent substrates.

A method employing the welding apparatus is also disclosed.

DETAILED DESCRIPTION

Referring to the drawings in which like elements are identified with identical numerals throughout,FIGS. 1 and 2illustrate a welding apparatus10for welding a work-piece12. As shown, the work-piece12includes adjacent substrates14,16that are shown as two abutted sheets of material positioned with respect to the weld apparatus10in order to be joined by a weld. Although substrates14,16are shown as two sheets of material, each of the substrates may also have a largely variable shape that additionally includes two opposite, substantially planar surfaces configured to be joined by a weld. Each of the substrates14,16may be formed from either a ferrous or a non-ferrous material that is suitable for being welded, such as steel, aluminum, and magnesium.

As shown inFIGS. 1-2, the work-piece12is characterized by a layer18. The layer18is disposed on the outer surfaces of the substrates14,16and may include an oxide coating that covers one or more planes of each substrate. Accordingly, the layer18may surround each of the substrates14,16. The layer18is typically caused by oxidation of materials such as aluminum or magnesium that is formed when such materials are exposed to ambient conditions. The layer18may also include impurities or contaminants of the subject material. The layer18on the outer surfaces of the substrates14,16typically reflects heat energy generated by an appropriate heat source, e.g., laser, and therefore affects heat generation at an interface20between the substrates by the welding apparatus10when the work-piece12is being welded. Consequently, the presence of oxide coating and/or contaminants on the layer18is generally detrimental to the efficiency of the welding process and the quality of the finished weld joint, in part because the reflected heat is wasted energy which, in turn, must be compensated for by a more powerful welding apparatus10. Additionally, a surface layer that is formed from oxide typically decomposes at elevated temperatures, such as above 2,000 degrees Celsius that generally characterize laser welding processes. A decomposed oxide layer typically forms inconsistencies, such as porosity and/or cracks that become trapped in the weld pool and result in a weaker weld joint.

The welding apparatus10includes an energy source22configured to generate a weld in a zone24formed at the interface20(shown inFIG. 2). Accordingly, the energy source22may be configured as any appropriate generator of a pool of welded material in the zone24, for example a laser beam, an electron beam, a plasma beam, a welding arc, or a hybrid energy source such as a laser/arc. The heat generated by the heat source22typically penetrates the layer18at the interface20and extends at least partially into the substrates14,16. Consequently, the zone24formed at the interface20may include portions of the substrates14,16, such that the weld pool includes the metal of the substrates themselves.

The welding apparatus10also includes a first generally circular wheel26. The first wheel26is characterized by an outer surface28having a first circumference. The first wheel26includes a first set of protrusions or teeth30disposed on the first circumference. The first wheel26is configured to rotate relative to the work-piece12. The welding apparatus10also includes a second wheel32characterized by an outer surface34having a second circumference. The second wheel32includes a second set of protrusions or teeth36disposed on the second circumference. Similarly to the first wheel26, the second wheel32is also configured to rotate relative to the work-piece12.

The first and second sets of protrusions30,36are configured to disrupt the surface layer18as the work-piece12is effectively clamped between the first and second wheels26,32and is traversed there between. The disruption of the layer18is achieved by means of mechanical fracturing of the layer, thus permitting the energy generated by the energy source22to be absorbed more effectively by the substrates14,16. Accordingly, the energy source22is positioned to heat the work-piece12and generate a weld in the zone24of the work-piece shortly following the disruption of the layer18in order to generate a higher quality weld pool.

In order to disrupt the surface layer18as the work-piece12is traversed between the first and second wheels26,32at least one of the first and second wheels is configured to vibrate at a predetermined frequency as the wheels subject the work-piece to a clamping load. The subject frequency may be established empirically during development of the weld process using the weld apparatus10, wherein the objective would be sufficient disruption of the layer18to generate an effective weld with minimized power consumption by the weld apparatus. According to initially conducted development of the welding apparatus10, in one possible embodiment, the predetermined frequency may be in the ultrasonic range of approximately 20-40 KHz under a clamping load in the range of 0.5-10 kilonewtons (kN).

As shown inFIGS. 1 and 2, the welding apparatus10includes a controller38configured to regulate the traversal of the work-piece12between the first and second wheels26,32, and regulate the energy source22to generate the weld. As shown inFIG. 1, the welding apparatus10may also include a fixture40which may be incorporated into a conveyor. The fixture40may thus be configured to move the work-piece12at an appropriate rate relative to the first and second wheels26,32, such that the first and second wheels are caused to rotate relative to the work-piece12. In such a case, the controller38is configured to regulate the operation of the fixture40to traverse the work-piece12relative to the first and second wheels26,32. Accordingly, as the first and second wheels26,32are rotated and vibrated, the first and second sets of protrusions30,36repeatedly engage the surface of work-piece12and disrupt the layer18.

As shown inFIG. 2, the welding apparatus10may also include a mechanism42configured to rotate the first wheel26and may also be configured to rotate the second wheel32, such that the work-piece12is caused to traverse relative to the first and second wheels at an appropriate rate. In such a case, the controller38is configured to regulate the mechanism42to rotate and vibrate the first and second wheels26,32. Accordingly, as the first and second wheels26,32rotate relative to the work-piece12the first and second sets of protrusions30,36repeatedly engage the surface of work-piece and disrupt any oxides and/or contaminants of the layer18.

As shown inFIG. 1, in the case when the work-piece12is being traversed by the fixture40in the direction represented by an arrow44, the two wheels are rotated in opposite directions, thus permitting the work-piece to pass between the wheels. In particular, when the first wheel26is rotated counterclockwise, as shown by an arrow46, the second wheel32is rotated in the opposite direction, i.e., clockwise, as shown by an arrow48. Similarly, as shown inFIG. 2, whether the mechanism42is used to rotate both the first and second wheels26,32or just one of the wheels in order to pull the work-piece through the first and second wheels, or to simply move the assembly of the first and second wheels relative to the work-piece12, the two wheels rotate in opposite directions represented by the arrows46and48.

With continued reference toFIG. 2, and as noted above, the assembly of first and second wheels26,32may be moved by the mechanism42relative to the work-piece12. The direction of such movement of the assembly of first and second wheels26,32is represented by an arrow50. Additionally, as noted, either one or both of the first and second wheels26,32may be employed as the active wheel(s) driven by the mechanism42. In the case that the mechanism42is used to rotate only one of the first and second wheels26,32, either the first wheel26or the second wheel32may be employed as an idler wheel that is rotated in response to the other of the two wheels pulling the work-piece12through and between the first and second wheels.

FIG. 3depicts a method60of welding the work-piece10. The method60is described herein with respect to joining the substrates14and16of the work-piece12in the welding apparatus10shown inFIGS. 1 and 2. The method commences in frame62with substrates14,16being abutted for processing by the welding apparatus10. After frame62, the method proceeds to frame64with traversing the work-piece12between the first wheel26and the second wheel32, such that the first wheel and the second wheel are rotated relative to the work-piece12.

Following frame64, the method advances to frame66, where it includes disrupting the layer18of the work-piece12by the first and second sets of protrusions30,36as the work-piece is traversed between the first and second wheels26,32. While the work-piece12is traversed between the first and second wheels26,32, ultrasonic vibration of at least one of the first and second wheels may serve to further disrupt the layer18. From frame66, the method proceeds to frame68, where the method includes generating a weld in the zone24of the work-piece12by the energy source22following the disruption of the layer18. The controller38may be used to regulate the energy source22for generating the weld.

Between frames62and64, the method60may proceed to frame70where the method additionally includes regulating the traversal of the work-piece12between the first and second wheels26,32via the controller38. In frame70the method may include moving the work-piece12relative to the first and second wheels26,32via the fixture40such that the first and second wheels are caused to rotate and vibrate relative to the work-piece to disrupt and remove any oxides and/or contaminants of the layer18. Alternatively, in frame70the method may include rotating at least one of the first and second wheels26,32such that the work-piece12is caused to traverse relative to the first and second wheels via the mechanism42.