Patent Application
20130240490
The present disclosure relates to a welding method and more particularly to a tack welding method complementary to a hybrid laser arc welding process.
Hybrid laser arc welding and laser beam welding for joining work pieces is known. Hybrid laser arc welding combines laser beam welding and arc welding, typically gas metal arc welding. U.S. Pat. No. 7,312,417 relates to a laser beam welding process which ensures maintaining a maximal gap width between the sheets and makes possible a maximal utilization of the achievable welding speed. The sheets, prior to welding, are first spot welded, wherein they are clamped only during this spot welding in order to ensure the maintenance of a maximum gap width. However, for narrow groove weld geometries (i.e. the width of the gap is approximately ½ the depth or less), tack welds may not penetrate fully to the root of the weld joint, causing the work pieces to buckle when a final seam weld is applied.
In one aspect of the present disclosure, a method of forming a tack weld is provided. The method provides a recess on an edge of a first piece. The edge of the first piece is configured to cooperate with a second piece. The method positions the first piece relative to the second piece so as to provide a gap between the first piece and the second piece. Subsequently, the method provides a tack weld within the recess of the first piece. The recess is configured to accommodate placing the tack weld at a root of the gap.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.
A weld joint 114 may be defined as the gap between the first piece 102 and the second piece 104. The configuration of the first piece 102 relative to the second piece 104 may define a width W and a depth D for the weld joint 114, as shown in
It should be understood that the weld joint 114 described herein may have a relatively smaller weld joint size as compared to that typically used for gas metal arc welding. The weld joint 114 may be relatively narrow such that it may be utilized for hybrid laser arc welding or laser beam welding of the first and second pieces 102, 104. Moreover, the weld joint 114 described herein is merely on an exemplary basis. Although the present disclosure is being described herein primarily with respect to J-groove weld joints, it should be apparent that the present disclosure may be applied to other weld geometries, such as single bevel joint with backing material, and the like, which also lie within the scope of the disclosure.
As shown in
The recess 202 may be configured to accommodate reception of a tack weld 302. In one embodiment, as shown in
As shown in the
In another embodiment of the present disclosure, as shown in
In one embodiment, a hybrid laser arc welding method may be used to join the first piece 102 and the second piece 104. After providing the tack weld 302 in the recess 202 of the first piece 102, and the second piece 104 a laser beam may be directed at the root 116, melting a portion of the first and second pieces 102, 104 forming a molten pool. A welding electrode may be placed in the weld joint 114 formed by the first and second pieces 102, 104 to deposit welding material within the weld joint 114 by an arc welding method. The welding material combines with the molten pool, thereby forming a seam between the first and second pieces. The welding electrode may be a solid, metal core or flux core welding electrode. The laser beam may be a sharp focus or de-focused laser beam. Depending on the size of the weld joint 114, a center of the laser beam may be aligned to a center of the weld joint 114 or with some offset. It should be noted that, for the exemplary embodiment, the laser beam to electrode distance may vary between 0 to 8 mm.
The hybrid laser arc welding may involve using a gas metal arc welding torch and the laser beam. In an exemplary setup, the laser beam may lead and the gas metal arc welding torch may trail in the hybrid laser arc welding process. Moreover, in one embodiment, the gas metal arc welding torch may be positioned substantially perpendicular with respect to a welding direction, while the laser beam may be oriented obliquely with respect to the welding direction. Conversely, in another embodiment, the gas metal arc welding torch may be oriented obliquely with respect to the welding direction, while the laser beam may be substantially perpendicular to the welding direction.
The process of forming the tack welding geometry will be described in detail in connection with
Gas metal arc welding is a known welding technique used to join large structural work pieces. Gas metal arc welding has a low energy density, resulting in a high tolerance for joint variability.
If using a gas metal arc welding process, a relatively larger root opening would be required at a joint formed between the first and second pieces 102, 104, in order for the gas metal arc weld to reach a root end of the joint. Hence, in such situations, the larger joint size would have facilitated in providing the tack weld 302 at the root end of the joint formed between the first and second mating surfaces 102, 104.
Another welding technique used is laser beam welding, which makes use of concentrated energy from the laser beam to produce joints with large penetration and very low distortion. However, laser beam welding has relatively lesser tolerance for joint variability.
Hybrid laser arc welding is a welding process that merges the high penetration and welding speed of laser beam welding with a gap-bridging ability of the gas metal arc welding. Hybrid laser arc welding involves combining gas metal arc welding and laser beam welding to form a welding process which is performed simultaneously in one process zone. It may be understood that depending on the kind of arc, laser beam process used, and other process parameters, the gas metal arc welding process and the laser beam welding process may influence each other in different ways.
Hybrid laser arc welding may hence have an improved weld penetration depth and welding speed compared to any of the gas metal arc welding or laser beam welding processes alone. In hybrid laser arc welding, the size of the weld joint 114 may be reduced compared to a joint configured for a gas metal arc welding process and thus allowing the weld size to become smaller. Hybrid laser arc welding may also result in less distortion due to reduced heat input, less filler material required due to a relatively smaller weld size, as well as minimized joint preparation due to elimination of beveling requirements. Also, time required for joint completion may be reduced.
However, in hybrid laser arc welding, the reduced size of the weld joint 114 leads to the tack weld 302 to reside at a top portion of the weld joint 114, leading to development of a root gap between the first and second pieces 102, 104. The presence of the tack weld 302 at the top portion of the weld joint 114 may also cause a reduction in the penetration of the hybrid laser arc weld and/or laser beam weld, by obstructing a path of the laser beam to reach the root 116 of the weld joint 114. Further, the tack weld 302 residing at the top portion of the weld joint may also lead to instability of the hybrid laser arc welding process which could result in spatters, welding fumes, porosity, and the like.
One solution may include providing the tack weld 302 from behind the first and second mating surfaces 102, 104. However, in some instances providing the tack weld 302 from the reverse side of the weld joint 114 may not be feasible due to accessibility issues based on factors like enclosed structural design, limited groove size, and the like.
The present disclosure relates to a tack welding method complementary to a relatively narrow grooved joint size. Referring to
Subsequently, at step 504, the first piece 102 may be positioned relative to the second mating surface 104 to define the weld joint 114 between the first and second pieces 102, 104. In one embodiment, the weld joint 114 may be configured as a J-groove joint, a single bevel joint, a flare joint, and the like. It should be understood that the disclosure may be utilized in any application making use of a narrow groove weld joint 114 as disclosed herein. The disclosure may also be utilized in regular grooved joints without any limitation.
At step 506, the tack weld 302 is provided within the recess 202 between the first piece 102 and the second piece 104. The recess 202 on the vertical edge 112 of the first piece 102 is provided such that the tack weld 302 may be accommodated at the root 116 of the weld joint 114. It should be understood that the recess 202 provided on the vertical edge 112 of the first piece 102 may increase the space between the first and second pieces 102, 104 to accommodate the reception of the tack weld 302 at the root 116 of the weld joint 114. The tack weld 302 when provided at the root 116 of the weld joint 114 may hold the first and second pieces 102, 104 in a tight and strong manner.
In one embodiment, as shown in
When the backing material 402 is being used, the recess 202 of the first piece 102 may be initially half-filled or filled such that at least a portion of the recess 202 is provided with the tack weld 302. The tack welding is provided by suitably placing a welding wire and melting the root 116 of the weld joint 114. Subsequently, the backing material 402 may be placed in the weld joint 114 such that the sharp edge 404 of the backing material 402 is in contact with the tack weld 302, causing the straight edge to be formed on the tack weld 302. Then, a remaining portion of the recess 202 may be fully filled by the tack weld 302. It may be understood that the tack welding may be provided by any known method.
The backing material 402 may be configured to form a straight edge on the tack weld 302. The straight edge formed on the tack weld 302 may facilitate in subsequent welding of the first and second pieces 102, 104 using the laser beam. The formation of the straight edge may result in less metal in the weld joint 114, facilitating the laser beam to melt the root 116 of the weld joint 114 without a lack of fusion or porosity defect.
Thereafter, the first and second pieces 102, 104 may be joined together by a known welding method. In one embodiment, hybrid laser arc welding may be used. A person of ordinary skill in the art will appreciate that the first and second pieces 102, 104 and the weld joint 114 described above are merely on an exemplary basis. Other applications not described herein also lie within the scope of this disclosure.
While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.
