Electric heating – Metal heating – For bonding with pressure
Patent
1996-12-24
1998-08-04
Hecker, Stuart N.
Electric heating
Metal heating
For bonding with pressure
219 81, 2191171, B23K 1106
Patent
active
057897182
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE ART
This invention relates to a mash seam welding process and a mash seam welding apparatus for continuously welding together two plate-like workpieces by overlapping the workpieces at their edges and applying a welding current between a pair of roller electrodes while the overlapping edge portions of the two plate-like workpieces are squeezed to be mashed, by and between the pair of roller electrodes.
BACKGROUND TECHNOLOGY
High-speed welding is possible by mash seam welding in which two plate-like workpieces are continuously welded together at their overlapping edge portions while the edge portions are squeezed to be mashed by and between a pair of roller electrodes, with a welding current being applied between the pair of roller electrodes. Since the mash seam welding is suitable for mass production, it is widely employed in production lines for steel plates, automobiles, etc.
In the mash seam welding described above, the two plate-like workpieces are positioned relative to each other by a clamping or guiding device that predetermined portions of the workpieces overlap each other, and the workpieces are fed so that the overlapping portions are squeezed by the pair of roller electrodes. Then, the two plate-like workpieces are continuously welded with a welding current applied between the roller electrodes while the overlapping portions of the workpieces are firmly squeezed and mashed by the roller electrodes.
In such mash seam welding, a so-called "weld nugget" N is formed based on a welding current applied to the pair of roller electrodes, such that the weld nugget N is located in a central part of the thickness of a portion of two plate-like workpieces 12.sub.H, 12.sub.M squeezed by the pair of roller electrodes, as shown in FIG. 10. The formed weld nugget N extends across an interface G of the two plate-like workpieces 12.sub.H, 12.sub.M, so that the weld may be given a predetermined strength (tensile strength). In FIG. 10, W.sub.G represents a width dimension of the interface G, while W.sub.N represents a width dimension of the weld nugget N in the direction of the interface. The weld strength obtained by the mash seam welding depends upon a ratio W.sub.N /W.sub.G, namely, a nugget ratio R.sub.N, which is the ratio of the width dimension W.sub.N of the weld nugget N to the width dimension W.sub.G of the interface G. The weld strength of the mash seal welding increases as this nugget ratio R.sub.N increases.
Where two plate-like workpieces having different thickness values are welded according to a conventional mash seam welding process, the interface G of the two plate-like workpieces 12.sub.H, 12.sub.M mashed by the pair of roller electrodes is formed at a position which is offset from the center of the thickness of the mashed portion in the direction toward the thin plate-like workpiece 12.sub.M, as indicated in FIG. 11. However, the weld nugget N is formed at a position intermediate between the pair of roller electrodes, that is, at a central part of the thickness of the mashed portion of the two plate-like workpieces 12.sub.H, 12.sub.M squeezed between the pair of roller electrodes. Accordingly, it is difficult to form the weld nugget N in alignment with the interface G of the two plate-like workpieces 12.sub.H, 12.sub.M, and is therefore difficult to obtain the desired weld strength in some cases.
While it is of course possible to increase the nugget ratio R.sub.N indicated above by increasing the amount of the welding current to thereby form a large weld nugget N, an increase in the nugget ratio R.sub.N leads to easy occurrence of cracking on the surfaces of the plate-like workpieces due to enlargement of the weld nugget N which undergoes rapid volumetric expansion. This cracking may develop into rupture in a subsequent press-forming process, for example. In view of this, the application of the mash seam welding is conventionally limited to the workpieces whose thickness ratio is not larger than a predetermined upper limit, for example, about 1.5, and the mash seam welding is no
REFERENCES:
patent: 4568812 (1986-02-01), Panknin et al.
patent: 5042711 (1991-08-01), Iskenderian et al.
patent: 5131581 (1992-07-01), Geiermann
patent: 5290990 (1994-03-01), Bischofberger et al.
patent: 5343010 (1994-08-01), Urech
Fukushima Toshihiro
Tanzawa Masaki
Hecker Stuart N.
Toyota Jidosha & Kabushiki Kaisha
LandOfFree
Mash seam welding process and mash seam welding apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mash seam welding process and mash seam welding apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mash seam welding process and mash seam welding apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1179511