Abstract

We describe the development of a real-time nonintrusive monitor to detect degradation of a gas shield condition during laser welding by use of on-axis spectrally resolved detection of light emitted from the workpiece. Failure of gas shielding to the point at which there is a risk of contamination from the air is revealed by the marked increase in the intensity of a spectral feature around 426 nm. To avoid unwanted sensitivity to the overall intensity of the radiation, the intensity at 426 nm is normalized by that at 835 nm, where the spectrum is insensitive to gas shielding. We collected the radiation by using the same optics as are used to deliver the processing beam, and thus the detection process is entirely nonintrusive. We demonstrate successful operation for welding stainless steel and titanium under both helium and argon gas shielding.

© 2001 Optical Society of America

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References

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  1. A. Lang, H. W. Bergmann, “Mechanical properties of laser welded Al-alloys,” in Proceedings of the European Conference on Laser Treatment of Materials (ECLAT ’92), B. L. Mordike, ed. (DGM Metallurgy Information, New York, 1992), pp. 163–168.
  2. F. M. Haran, D. P. Hand, C. Peters, J. D. C. Jones, “Focus control system for laser welding,” Appl. Opt. 36, 5246–5251 (1997).
    [CrossRef] [PubMed]
  3. S. Beirmann, A. Topkaya, M. Jagiella, “Capacitive clearance sensor system for high quality Nd:YAG laser cutting and welding of sheet metals,” in Proceedings of the European Conference on Laser Treatment of Materials (ECLAT ’92), B. L. Mordike, ed. (DGM Metallurgy Information, New York, 1992), pp. 51–55.
  4. F. M. Haran, D. P. Hand, S. M. Ebrahim, C. Peters, J. D. C. Jones, “Optical signal oscillations in laser keyhole welding and potential application to lap welding,” Meas. Sci. Technol. 8, 627–633 (1997).
    [CrossRef]
  5. LWM 900 Laser Welding Monitor, manufactured by Jurca Optoelektronik GmbH, Raiffeisenstrasse, 5D-63110 Rodgau, Germany.
  6. W. Kluft, P. Boerger, R. Schwartz, “On-line monitoring of laser welding of sheet metal by special evaluation of plasma radiation,” (Prometec GmbH, Jülicher Strasse 338, D-52070 Aachen, Germany), Special Print document PVE.046.116.GB.
  7. E. J. Morgan-Warren, “Atmosphere control criteria for welding titanium,” in Conference on Advances in Welding Processes, Harrogate, May 1978, pp 343–349.
  8. D. D. Harwig, C. Fountain, W. Ittiwattana, H. Castner, “Oxygen equivalent effects on the mechanical properties of titanium welds,” Weld. J. 79, 3055–3165 (2000). (Edison Welding Institute, Columbus, Ohio, 1996).

2000 (1)

D. D. Harwig, C. Fountain, W. Ittiwattana, H. Castner, “Oxygen equivalent effects on the mechanical properties of titanium welds,” Weld. J. 79, 3055–3165 (2000). (Edison Welding Institute, Columbus, Ohio, 1996).

1997 (2)

F. M. Haran, D. P. Hand, C. Peters, J. D. C. Jones, “Focus control system for laser welding,” Appl. Opt. 36, 5246–5251 (1997).
[CrossRef] [PubMed]

F. M. Haran, D. P. Hand, S. M. Ebrahim, C. Peters, J. D. C. Jones, “Optical signal oscillations in laser keyhole welding and potential application to lap welding,” Meas. Sci. Technol. 8, 627–633 (1997).
[CrossRef]

Beirmann, S.

S. Beirmann, A. Topkaya, M. Jagiella, “Capacitive clearance sensor system for high quality Nd:YAG laser cutting and welding of sheet metals,” in Proceedings of the European Conference on Laser Treatment of Materials (ECLAT ’92), B. L. Mordike, ed. (DGM Metallurgy Information, New York, 1992), pp. 51–55.

Bergmann, H. W.

A. Lang, H. W. Bergmann, “Mechanical properties of laser welded Al-alloys,” in Proceedings of the European Conference on Laser Treatment of Materials (ECLAT ’92), B. L. Mordike, ed. (DGM Metallurgy Information, New York, 1992), pp. 163–168.

Castner, H.

D. D. Harwig, C. Fountain, W. Ittiwattana, H. Castner, “Oxygen equivalent effects on the mechanical properties of titanium welds,” Weld. J. 79, 3055–3165 (2000). (Edison Welding Institute, Columbus, Ohio, 1996).

Ebrahim, S. M.

F. M. Haran, D. P. Hand, S. M. Ebrahim, C. Peters, J. D. C. Jones, “Optical signal oscillations in laser keyhole welding and potential application to lap welding,” Meas. Sci. Technol. 8, 627–633 (1997).
[CrossRef]

Fountain, C.

D. D. Harwig, C. Fountain, W. Ittiwattana, H. Castner, “Oxygen equivalent effects on the mechanical properties of titanium welds,” Weld. J. 79, 3055–3165 (2000). (Edison Welding Institute, Columbus, Ohio, 1996).

Hand, D. P.

F. M. Haran, D. P. Hand, S. M. Ebrahim, C. Peters, J. D. C. Jones, “Optical signal oscillations in laser keyhole welding and potential application to lap welding,” Meas. Sci. Technol. 8, 627–633 (1997).
[CrossRef]

F. M. Haran, D. P. Hand, C. Peters, J. D. C. Jones, “Focus control system for laser welding,” Appl. Opt. 36, 5246–5251 (1997).
[CrossRef] [PubMed]

Haran, F. M.

F. M. Haran, D. P. Hand, C. Peters, J. D. C. Jones, “Focus control system for laser welding,” Appl. Opt. 36, 5246–5251 (1997).
[CrossRef] [PubMed]

F. M. Haran, D. P. Hand, S. M. Ebrahim, C. Peters, J. D. C. Jones, “Optical signal oscillations in laser keyhole welding and potential application to lap welding,” Meas. Sci. Technol. 8, 627–633 (1997).
[CrossRef]

Harwig, D. D.

D. D. Harwig, C. Fountain, W. Ittiwattana, H. Castner, “Oxygen equivalent effects on the mechanical properties of titanium welds,” Weld. J. 79, 3055–3165 (2000). (Edison Welding Institute, Columbus, Ohio, 1996).

Ittiwattana, W.

D. D. Harwig, C. Fountain, W. Ittiwattana, H. Castner, “Oxygen equivalent effects on the mechanical properties of titanium welds,” Weld. J. 79, 3055–3165 (2000). (Edison Welding Institute, Columbus, Ohio, 1996).

Jagiella, M.

S. Beirmann, A. Topkaya, M. Jagiella, “Capacitive clearance sensor system for high quality Nd:YAG laser cutting and welding of sheet metals,” in Proceedings of the European Conference on Laser Treatment of Materials (ECLAT ’92), B. L. Mordike, ed. (DGM Metallurgy Information, New York, 1992), pp. 51–55.

Jones, J. D. C.

F. M. Haran, D. P. Hand, C. Peters, J. D. C. Jones, “Focus control system for laser welding,” Appl. Opt. 36, 5246–5251 (1997).
[CrossRef] [PubMed]

F. M. Haran, D. P. Hand, S. M. Ebrahim, C. Peters, J. D. C. Jones, “Optical signal oscillations in laser keyhole welding and potential application to lap welding,” Meas. Sci. Technol. 8, 627–633 (1997).
[CrossRef]

Lang, A.

A. Lang, H. W. Bergmann, “Mechanical properties of laser welded Al-alloys,” in Proceedings of the European Conference on Laser Treatment of Materials (ECLAT ’92), B. L. Mordike, ed. (DGM Metallurgy Information, New York, 1992), pp. 163–168.

Morgan-Warren, E. J.

E. J. Morgan-Warren, “Atmosphere control criteria for welding titanium,” in Conference on Advances in Welding Processes, Harrogate, May 1978, pp 343–349.

Peters, C.

F. M. Haran, D. P. Hand, C. Peters, J. D. C. Jones, “Focus control system for laser welding,” Appl. Opt. 36, 5246–5251 (1997).
[CrossRef] [PubMed]

F. M. Haran, D. P. Hand, S. M. Ebrahim, C. Peters, J. D. C. Jones, “Optical signal oscillations in laser keyhole welding and potential application to lap welding,” Meas. Sci. Technol. 8, 627–633 (1997).
[CrossRef]

Topkaya, A.

S. Beirmann, A. Topkaya, M. Jagiella, “Capacitive clearance sensor system for high quality Nd:YAG laser cutting and welding of sheet metals,” in Proceedings of the European Conference on Laser Treatment of Materials (ECLAT ’92), B. L. Mordike, ed. (DGM Metallurgy Information, New York, 1992), pp. 51–55.

Appl. Opt. (1)

Meas. Sci. Technol. (1)

F. M. Haran, D. P. Hand, S. M. Ebrahim, C. Peters, J. D. C. Jones, “Optical signal oscillations in laser keyhole welding and potential application to lap welding,” Meas. Sci. Technol. 8, 627–633 (1997).
[CrossRef]

Weld. J. (1)

D. D. Harwig, C. Fountain, W. Ittiwattana, H. Castner, “Oxygen equivalent effects on the mechanical properties of titanium welds,” Weld. J. 79, 3055–3165 (2000). (Edison Welding Institute, Columbus, Ohio, 1996).

Other (5)

A. Lang, H. W. Bergmann, “Mechanical properties of laser welded Al-alloys,” in Proceedings of the European Conference on Laser Treatment of Materials (ECLAT ’92), B. L. Mordike, ed. (DGM Metallurgy Information, New York, 1992), pp. 163–168.

S. Beirmann, A. Topkaya, M. Jagiella, “Capacitive clearance sensor system for high quality Nd:YAG laser cutting and welding of sheet metals,” in Proceedings of the European Conference on Laser Treatment of Materials (ECLAT ’92), B. L. Mordike, ed. (DGM Metallurgy Information, New York, 1992), pp. 51–55.

LWM 900 Laser Welding Monitor, manufactured by Jurca Optoelektronik GmbH, Raiffeisenstrasse, 5D-63110 Rodgau, Germany.

W. Kluft, P. Boerger, R. Schwartz, “On-line monitoring of laser welding of sheet metal by special evaluation of plasma radiation,” (Prometec GmbH, Jülicher Strasse 338, D-52070 Aachen, Germany), Special Print document PVE.046.116.GB.

E. J. Morgan-Warren, “Atmosphere control criteria for welding titanium,” in Conference on Advances in Welding Processes, Harrogate, May 1978, pp 343–349.

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Figures (8)

Fig. 1
Fig. 1

General arrangement for gas shielding. Air is excluded from the gas shoe by saturation with inert gas whose positive pressure limits seepage of oxygen into the shoe.

Fig. 2
Fig. 2

When welding nonflat components, air can seep into the gas shoe.

Fig. 3
Fig. 3

Experimental arrangement. Light is collected from the workpiece, counterpropagated along the delivery fiber, and monitored by a miniature PC plug-in spectrometer.

Fig. 4
Fig. 4

(a) Spectrum obtained when we welded titanium with a reducing shield gas flow: lower trace, good gas shielding; upper trace, poor gas shielding. Vertical broken lines at 426 and 835 nm represent spectral points that were monitored to detect poor gas shield conditions. (b) Spectrum obtained when we welded stainless steel with a reducing shield gas flow: lower trace, good gas shielding; upper trace, poor gas shielding.

Fig. 5
Fig. 5

(a) Spectrum obtained for a titanium weld with poor gas shielding normalized by that for a weld with good shielding conditions. (b) Spectrum obtained for a stainless steel weld with poor gas shielding normalized by that for a weld with good shielding conditions.

Fig. 6
Fig. 6

Spectral ratio (ratio of amplitude at 426 and 835 nm) asa function of gas flow rate by use of both argon (▲) and helium (■).

Fig. 7
Fig. 7

Spectral ratio shown as a function of weld hardness expressed in Vickers hardness values. Note that weld hardness had already started to increase before visible deterioration could be seen. (The value of 400 HV as a good/bad cutoff point is arbitrary within a region approximately 30 HV above the best weld. The welds with a measured hardness greater than this started to exhibit discoloration.)

Fig. 8
Fig. 8

System control program flow diagram.

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