Spectroscopic studies of GTA welding plasmas. Temperature calculation and dilution measurement

Abstract

A spectroscopic study of the GTAW plasma-plume created during the welding of stainless steel and other materials (iron, nickel and chromium) has been carried out. The spectra of these plasmas have been studied for several welding parameters. Temperature calculations are based on the observation of relative intensities and shapes of the emission peaks. We assume that the plasma is in local thermal equilibrium. The temperature is calculated with the Boltzmann plot method from twelve iron emission lines (in the range 368-385 nm): it varies between 9650 and 12 100 K. Dilution experiments have been carried out. We checked the mixing of metals: during welding of two different metallic plates and during welding with an Inconel wire. Dilution is monitored following the intensity of some characteristic emission lines (chromium and nickel). Comparison of spectroscopic results and metallographic ones is made.

Emission spectrometry evaluation in arc welding monitoring system

“…(2)) in the GMAW process, calculated by Lacroix et al [4], is N e ≥ 1.81 × 10 19 m −3 . This result is used in the present work.…”

“…Such wavelengths provide information on thermodynamic and quantum parameters that are necessary for calculating properties of interest. In the specific case of the welding process, a qualitative analysis (identification of chemical elements) allows the detection of weld contamination [10], helps in the selection and qualification of shielding gases [11] and provides a means of studying the rate of dilution in dissimilar metal welding [4]. On the other hand, the quantitative analysis involves the measurement of the intensities of each different wave length emitted by the plasma radiation and provides a means of calculating the most important plasma properties: its electronic temperature and its density.…”

“…The innovations generated by these studies are based on the physical phenomena involved in the arc welding processes, mainly those related to the plasma arc and its influence on the weld pool [1]. The applied techniques range from numerical simulation of the arc [2], image analysis [3], sound spectrum analysis and electromagnetic emission analysis [4][5][6] to the use of intelligent systems, based on neural networks and fuzzy logic [7].…”

Sensors for quality control in welding

“…Moreover, the non-conventional parameters, at the present, are not used enough to evaluate the welding quality. They are some non-contact methods for welding monitoring process as acoustical sensing [8][9][10][11][12][13][14][15], spectroscopy emission [16][17][18], infrared emission [19][20][21] and sensoring combination [22].…”

Utilização Da Espectroscopia Óptica De Emissão Para Monitoração E Controle Da Temperatura Da Soldagem Gtaw

“…(5) A análise quantitativa é a medição da intensidade de cada um dos comprimentos de onda emitidos pela radiação eletromagnética do plasma, permitindo o diagnóstico das principais propriedades do plasma, sua temperatura e densidade. (5) …”