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Title: Modeling of Plasma Plume Induced During Laser Welding

Abstract

Theoretical modelling of the plasma plume induced during welding of iron sheets with CO2 laser are presented. The set of equations consists of equation of conservation of mass, energy, momentum and the diffusion equation and is solved with the use of commercially available program Fluent 6.2. The computations are made for the cases when the shielding gas is either argon or helium. The results show that in the case when argon is the shielding gas there are actually two plasmas; argon plasma and metal plasma.

Authors:
; ;  [1]
  1. Institute of Fundamental Technological Research, SwiePtokrzyska 21, 00-049 Warsaw (Poland)
Publication Date:
OSTI Identifier:
20797889
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 812; Journal Issue: 1; Conference: PLASMA 2005: International conference on research and applications of plasmas; 3. German-Polish conference on plasma diagnostics for fusion and applications; 5. French-Polish seminar on thermal plasma in space and laboratory, Opole-Turawa (Poland), 6-9 Sep 2005; Other Information: DOI: 10.1063/1.2168814; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ARGON; CARBON DIOXIDE LASERS; DIFFUSION EQUATIONS; HELIUM; IRON; LASER RADIATION; LASER WELDING; LASER-PRODUCED PLASMA; NUMERICAL ANALYSIS; PLASMA PRODUCTION; PLASMA SIMULATION; SHIELDING

Citation Formats

Moscicki, T., Hoffman, J., and Szymanski, Z. Modeling of Plasma Plume Induced During Laser Welding. United States: N. p., 2006. Web. doi:10.1063/1.2168814.
Moscicki, T., Hoffman, J., & Szymanski, Z. Modeling of Plasma Plume Induced During Laser Welding. United States. doi:10.1063/1.2168814.
Moscicki, T., Hoffman, J., and Szymanski, Z. Sun . "Modeling of Plasma Plume Induced During Laser Welding". United States. doi:10.1063/1.2168814.
@article{osti_20797889,
title = {Modeling of Plasma Plume Induced During Laser Welding},
author = {Moscicki, T. and Hoffman, J. and Szymanski, Z.},
abstractNote = {Theoretical modelling of the plasma plume induced during welding of iron sheets with CO2 laser are presented. The set of equations consists of equation of conservation of mass, energy, momentum and the diffusion equation and is solved with the use of commercially available program Fluent 6.2. The computations are made for the cases when the shielding gas is either argon or helium. The results show that in the case when argon is the shielding gas there are actually two plasmas; argon plasma and metal plasma.},
doi = {10.1063/1.2168814},
journal = {AIP Conference Proceedings},
number = 1,
volume = 812,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}
  • The plasma produced during laser welding of magnesium alloy is studied. The space-averaged electron densities are determined from the Stark broadening of the 4481.16 A Mg II spectral line. Their values reach 1.6x1023 m-3 near the metal surface. The intensities of the measured atomic 5528.41 A Mg I spectral line and 4481.16 A Mg II spectral line depend on the plasma temperature and their profiles vary with the temperature and electron density. This fact was used to reproduce the radial temperature distribution in the plasma plume. The shape of the temperature distribution was assumed according to numerical calculations of plasmamore » plume and exact values were found fitting the synthetic line profile to the experimental one. It has been found that the maximum plasma temperature is 8000 K.« less
  • A spectroscopic study of a laser-induced plume created during the welding of stainless steel and other materials (iron and chromium) has been carried out. A pulsed Nd:YAG laser of 1000 W average power is used. The evolutions of the electron temperature and electron density have been studied for several welding parameters. We use working powers from 300 to 900 W and pulse durations between 1.5 and 5 ms. The influence of shielding gases like nitrogen and argon has been taken into account. Temperature and density calculations are based on the observation of the relative intensities and shapes of the emissionmore » peaks. We assume that the plasma is in local thermal equilibrium. The temperature is calculated with the Boltzmann plot method and the density with the Stark broadening of an iron line. The electron temperatures vary in the range of 4500{endash}7100 K, electron density between 3{times}10{sup 22} and 6.5{times}10{sup 22} m{sup {minus}3}. The absorption of the laser beam in the plasma is calculated using the Inverse Bremsstrahlung theory. {copyright} {ital 1997 American Institute of Physics.}« less
  • Many papers have sought correlations between the parameters of secondary particles generated above the beam/work piece interaction zone, dynamics of processes in the keyhole, and technological processes. Low- and high-frequency oscillations of the current, collected by plasma have been observed above the welding zone during electron beam welding. Low-frequency oscillations of secondary signals are related to capillary instabilities of the keyhole, however; the physical mechanisms responsible for the high-frequency oscillations (>10 kHz) of the collected current are not fully understood. This paper shows that peak frequencies in the spectra of the collected high-frequency signal are dependent on the reciprocal distancemore » between the welding zone and collector electrode. From the relationship between current harmonics frequency and distance of the collector/welding zone, it can be estimated that the draft velocity of electrons or phase velocity of excited waves is about 1600 m/s. The dispersion relation with the properties of ion-acoustic waves is related to electron temperature 10 000 K, ion temperature 2 400 K and plasma density 10{sup 16} m{sup −3}, which is analogues to the parameters of potential-relaxation instabilities, observed in similar conditions. The estimated critical density of the transported current for creating the anomalous resistance state of plasma is of the order of 3 A·m{sup −2}, i.e. 8 mA for a 3–10 cm{sup 2} collector electrode. Thus, it is assumed that the observed high-frequency oscillations of the current collected by the positive collector electrode are caused by relaxation processes in the plasma plume above the welding zone, and not a direct demonstration of oscillations in the keyhole.« less
  • The vapour-plasma plume produced in the welding of 6-mm thick VT-23 titanium alloy plates by ytterbium fibre laser radiation of up to 10 kW power is studied in the protective Ar gas medium. High-speed video filming of the vapour-plasma plume is used to visualise the processes occurring during laser welding. The coefficient of inverse bremsstrahlung by the welding plasma plume is calculated from the data of the spectrometric study. (interaction of laser radiation with matter)
  • The authors study the laser-induced plume created during steel welding. The plume emission is measured with a spectrograph and a Photodiodes Array Detector (PDA). They study the evolution of temperature and electron density for several welding parameters (laser energy, pulse duration and shielding gases). Temperature and density calculations are based on the observation of line intensities and shapes. The other part of this study presents briefly a theoretical model which allows calculating the densities of each component of a complex plasma; like the one of stainless steel. These calculations yield the absorption of the laser energy in the plume.