Mechanism of Zn Vapour Suppressed by Al In Laser Lap Welding of High Strength Zinc Coated Sheet Steel

Abstract:

The basic feasibility of laser fusion welding for prefabrication and assembly of zinc-coated sheet steel auto body components has been demonstrated in a significant number of prior studies. For trouble-free high volume manufacturing, however, one leading key technical concern remains incompletely resolved. In lap or similar weld joint geometries, venting of trapped Zn vapour can seriously disturb the molten weld pool and give rise to gross fusion defects. In this paper, the technical status of the issue has been reviewed, and various experiments were planned to explore Al foil as an interlayer and dual beam laser for suppressing Zn vapour. The results have shown that the welding processing is very sTable when the lap 1+1 mm sheet steel is welded by using Nd-Yag laser at 3KW power and 4m/min travel speed (defined as single beam) with 75μm Al foil as interlayer. However, if first using 2KW power and 4m/min travel speed, secondly using 3KW power and4m/min travel speed (defined as dual beam), only 25 μm Al foil can stabilize welding fusion pool. It is found that Al foil just store the Zn vapour in the single beam method and cannot mix with Zn to form Al-Zn binary alloy, because the laser heating is too fast that Zn has been vaporized before Al was melted. But Al can mix with Zn to form Al-Zn binary alloy in the dual beam method, therefore, the boiling temperature is raised to about 1600°C. So that, in laser lap welding of Zn coated (galvanized) sheet steel, the Al-Zn alloy will be more effective than Al metal for stabilizing welding process.

• Periodical: Applied Mechanics and Materials (Volumes 37-38)
• Pages: 634-642
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.37-38.634
• Online since: November 2010
• Authors: Shi Quan Zhou, Zhen Guo Peng
• Keywords: Dual Beam, Laser Lap Welding, Single Beam, Zinc Coated Steel Sheet, Zn Vapour

References

[1] R. Akhter: Proceedings of Lasers in Manufacturing LIM-55th International Conference, (published by IFS Publications, Kempston, UK, 1988), pp.195-206.

[2] U. Bethke: DVS Conference ECLAT '94 – Laser Treatment of Materials. (Deutscher Verband fur Schweisstechnik), (1994), pp.284-289.

[3] P. Ltd: Canadian patent Application 2209804. (1999).

[4] M.P. Graham: Welding Journal Research Supplement, Vol. 75 (1996) No. 5, pp.162-170.

[5] M.P. Graham, H.W. Kerr and D.C. Weckman: International Society for Optical Engineering (SPIE) Conference Proceedings, Vol. 2703 (1998), pp.170-183.

[6] P. Denny and J. Xie: Proceedings of Laser Applications in the Automotive Industry Conference, (Laser Institute of America, 2000), pp. A1-A9.

[7] M. Kielwasser: Proceedings of of Laser Applications in the Automotive Industry Conference, (Laser Institute of America, 2000), pp.10-19.

[8] H. Gu: Proceedings of of Laser Applications in the Automotive Industry Conference, (Laser Institute of America, 2000), pp.1-6.

[9] Y.F. Tzeng: Welding Journal, Research Supplement, Vol. 78 (1999) No. 7, pp.238-244.

[10] R.R.G.M. Pieters, R. Thiessen and I.M. Richardson：Laser welding of zinc coated steel in an overlap configuration, （IIW Doc. IV-838-03）.

[11] British Aerospace PLC：UK Patent Application 2274257A, (1994).

[12] N. Karube, Y. Nakata and A. Mori: proceedings of 25th ISATA International Symposium on Automotive Technology and Automation, (Florence Italy. Automotive Automation, Ltd., Croydon, UK, 1992), pp.119-137.

[13] K. Fukui, H. Fujimoto and M. Yasuyama: SAE International Body Engineering Conference, (Society of Automotive Engineers, Warrendale, PA, 1998), pp.179-190.

[14] X. Li, S. Lawson, F. Goodwin and Y. Zhou: J. Laser Appl., Vol. 19, (2007), pp.259-264.

[15] D. John, Jr. McKinley and E. John: The Tournal of Chemical Physics. Vol. 22 (1954), No. 6, pp.1120-1124.

[16] L. Yang, X. Peng and B. Wang: Int. J. Heat MassTransfer, Vol. 44 (2001), pp.4465-73.

[17] A.R. Marder: Progress in Materials Science, Vol. 45 (2000), pp.191-27.

[18] B. Ozturk: Vaporization of zinc from scrap, (Steelmaking Conference Proceedings, 1996), p.583.

[19] Sunil Mathew, Theo G. Keith Jr and Efstratios Nikolaidis: International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 16 (2006) No. 4, pp.393-416.

DOI: 10.1108/09615530610653055