High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes) An International Journal

ISSN for PRINT: 1093-3611

For Online Access

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2002, Volume6

Issue 4

125 pages

Issue price - $144.00

J. Hoffman
Institute of Fundamental Technological Research - Polish Academy of Sciences 00-049 Warsaw, Swietokrzyska 21, Poland

Z. Szymanski
Instytut Podstawowych Problemow Techniki, PAN Swietokrzyska 21, 00-049 Warszawa, Poland

Experimental study of titanium plasma under laser welding conditions is presented. Both plasma plume temperature and radiation oscillations are studied. Welding was done with the continuous wave CO₂ laser, Photon Sources VFA 2500, operating at the power of 1ё2 kW. Emission spectra from laser produced plasmas were measured with a 1.3 m focal length spectrograph and a 1254 Silicon Intensified Target (SIT) detector connected to EG&G'PARC Optical Multichannel Analyzer (ОМА) III. Welded material was titanium alloy sheets OT-4 (containing besides Ti, 1.5% Al, and 1.3% Mn) 1-2.5 mm thick. The average electron temperature obtained from different Ti II spectral lines was ~14500 К near the metal surface and decreased to ~8000 К at a distance of 2 mm from the surface. The Fourier analysis of the fluctuations of plasma radiation observed during laser welding has also been made. Plasma fluctuations were registered both in monochromatic and broad band radiation with the use of monochromator and photomultiplier or photodiode. In the case of thin, 1 mm, sheets power spectral densities of the signals contain peaks at frequencies of 1.4 and 4 kHz, which are consistent with the theoretical model of keyhole oscillations.

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