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- Ducharme, R., et al.
(författare)
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Effects of different shielding gas compositions on the process of cw CO2 laser welding in the hyperbaric range
- 1996
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Ingår i: XI International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference. - Bellingham, Wash : SPIE - International Society for Optical Engineering. ; , s. 530-533
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Konferensbidrag (refereegranskat)abstract
- A continuous carbon-dioxide laser of 1.35 kW has been used to study the welding of 5 mm thick stainless steel for pressures ranging from 0.1 to 0.8 MPa in increments of 0.1 MPa. Experimental data, including penetration depths, weld widths, and in some cases weld pool profiles, has been obtained for each value of the pressure using different mixtures of argon and helium shielding gases. In a previous paper it has been reported that keyhole welding could not be carried out for pressures significantly in excess of atmospheric pressure using pure argon and nitrogen shielding gases, but that the process was possible at pressures up to 0.8 MPa using helium. In the present paper the critical pressure for keyhole welding is determined as a function of the mixed shielding gas composition. The laser material interaction is analyzed by solving the heat conduction equation with line and point heat sources representing the keyhole and plume respectively. The line source strength is itself calculated from consideration of the inverse bremsstrahlung and Fresnel absorption processes in the keyhole. It is concluded that successful laser welding in the hyperbaric range crucially hinges on good plume control through the effective delivery of an appropriate shielding gas mixture.
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| 2. |
- Sarady, Istvan, et al.
(författare)
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Joining of cemented tungsten carbide to tool steel using Nd:YAG-laser and optical fibres
- 1992
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Ingår i: Proceedings of the Laser Materials Processing Symposium : ICALEO '92. - Orlando, Fla : Laser institute of America. - 0912035498 ; , s. 529-533
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Konferensbidrag (refereegranskat)abstract
- The aim of the present work was to produce tools for powder compacting by joining cemented tungsten carbide to high-quality tool steels by laser welding. The conventional method of joining such materials is by brazing or by using adhesives (glue), both of which have disadvantages: low strength and poor positional accuracy. In the case of laser welding, the components were positioned exactly in a jig or fixture, heated to 200-300°C and finally welded by using a pulsed Nd:YAG laser giving a positional accuracy in the order of a few micrometers. The laser beam was optically split and guided by optical fibers to opposite sides of the joint greatly reducing the effect of thermal distortion. The use of optical fibers also result in a smooth energy distribution in the beam spot reducing the risk of crack formation. Compressive fatigue strength of the joined components was determined. Cross-sectioned samples were examined for microstructure, microhardness and the distribution of alloying elements in the joint zone. The weld surface was also examined for evidence of microcracking. The method described can complement conventional and vacuum brazing techniques in certain applications.
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