Electric heating – Metal heating – By arc
Patent
1983-09-08
1985-10-08
Albritton, C. L.
Electric heating
Metal heating
By arc
219121LC, B23K 2600
Patent
active
045462305
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a welding process using a laser beam and, more particularly, to a welding process using a laser beam for joining metals such as steel plates along a see-through groove such as a square groove formed between opposed edges of the metals without use of any backing strip but by supplying a filler wire, in which the filler wire is inserted into the groove to apoint therein coincident with the focused spot of the laser beam so that the globule or droplet produced from the filler wire properly proceeds to the opposed edge faces of metals defining the groove, thereby improving the permissible gap of the groove and increasing the welding speed.
BACKGROUND TECHNIQUES
The welding process using a laser beam generally is a high speed, low heat input and high efficiency welding process as is well known in the art. In this welding process, the permissible gap of the groove is very small because a very high positioning precision is required.
In the laser beam welding, a laser beam is converged through a lens or like optical system, and its intensified energy density spot is used as a heat source for the welding. A weld bead of high bead shape index (i.e., depth of penetration divided by width of bead) thus can be obtained with a low heat input. For this reason, the laser welding is extensively utilized in applications where thermal deformation due to the welding heat input is undesired. However, since a spot of a laser beam converged by a lens or like optical system is used as the source of heat, the permissible gap of the groove is very small, and the edge preparation and butt of metals to be joined require high precision.
Usually, the permissible groove gap is 15 20% of the thickness of metals to be joined, and when joining welding coils in a steel process line or like case where the weld line is long, it is difficult to maintain the groove gap within the permissible value. By way of example, when joining cold rolled steel plates with a thickness of 1 mm by welding, the permissible groove gap is approximately 0.1 mm. When a cold rolled steel plate is cut to a length of 1 m or more using an ordinary shearing machine, the cut edge is liable to have at least locally curved portions. If it is intended to join such steel plates by square groove butt welding, the groove gap is liable to exceed 0.2 mm. In such a case, local failure of deposition of the weld bead is liable when the metal pieces are joined by the laser welding, thus spoiling the soundness of the joint.
Various measures have been proposed for the purpose of increasing the permissible value of the groove gap. These proposed measures, however all have problems in the operability. In addition, the groove gap is rather increased to deteriorate the features of the laser welding, while the permissible groove gap is not improved so much.
As an example, U.S. Pat. No. 4,167,662 discloses a welding process, in which an electric arc is produced between an electrode and a heat-affected zone (hereinafter referred to as HAZ) including the weld zone produced by a laser beam directed to the metals to be joined. More specifically, as shown in FIG. 1, a laser beam 1 generated from a laser (not shown) is converged by a lens 2 so that it is focused at a point 4 on metals 3 to be joined, thus forming a HAZ at the point 4 of focus. An electric arc is produced between an electrode 5 and the HAZ. Reaction gas, e.g., oxygen, is jet from a nozzle 7 toward the point 4. The metals 3 are joined by this welding process. In this welding process, as the electrode 5 may be used those employed for the TIG welding or MIG welding. In addition, the heat source that is constituted by the laser beam may be augmented by the heat of the electric arc and further by the reaction heat of the oxygen jet, if desired. The permissible groove gap thus can be increased. On the demerit side, however, the welding heat input is inevitably increased, which is undesired from the standpoint of the low heat input welding, a primary feature of the laser welding.
FIG. 2 shows
Kamada Akio
Nishiyama Noboru
Sasaki Hiroaki
Albritton C. L.
Kawasaki Steel Corporation
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