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Chemical compositions of a weld can be varying locally as a result of the welding process. These local variations can be due to the vaporization of individual alloying elements. In this work, tungsten inert gas (TIG) bead-on-plate stainless steel welds of EN grade 1.4404 and 1.4435 were investigated using laser-induced breakdown spectroscopy (LIBS) on the completed welds. This study aims to reveal the welding parameters’ influence on the resulting local chemical compositions of the stainless steel welds. We demonstrated Mn vaporize before Cr due to its lower latent enthalpy of vaporization. Hence, Mn accumulates on the heat-affected zone (HAZ) both sides across the weld bead by being swept away through the circulation flow of the welding plasma. Additionally, increasing the heat input tends to enhance the accumulated Mn content on the HAZ as well as increasing the shielding gas flow rate. The results are in good agreement with the literature and proved that LIBS is an effective method to inspect completed welds.
Chemical compositions of the welds have significant effect on weld quality. Current inspection methods for the weld seams employ mostly post factum methods and cannot prevent weld defects.Elemental burn offs may significantly affect solidification leading to embrittlement or cracking. Control of weld chemical compositions insures a controlled solidification and resistance to related weld defects.
TIG welding process was monitored using LIBS for the in situ measurement of chemical compositions in austenitic stainless steels. This research aims to prototype a real-time chemical composition analysis system for welding applications and prove the feasibility of such a quality control loop.
The chemical compositions of the weld pool, considering the welding metallurgy, is the most critical parameter for any occurring weld defects, e.g. hot cracking. Hence, controlling the weld pool chemical composition allows governing of the weld pool solidification behavior by monitoring and adjusting the respective welding parameters, e.g. welding current.
LIBS measurements were conducted during a TIG-welding process. The effect of the welding plasma on the LIBS signal was thoroughly investigated by varying various LIBS settings, e.g. delay and exposure time. Quantification of the main alloying elements Cr and Ni in the weld pool during welding was achieved by univariate calibration procedure.
Chemical composition of the welding seam and HAZ has significant effect on weld quality.
Current inspection methods for weld seams measure and investigate post factum and cannot prevent weld defects. Element burn-off may significantly affect solidification leading to embrittlement or cracking. Control of weld chemical compositions insures a controlled solidification and resistance to related weld defects. “Industry 4.0” is the current trend of automation and data exchange in manufacturing technologies. With this trend “intelligent” welding machines will be developed. LIBS can provide significantly important online data for such systems.
Chemical composition of the welding seam and HAZ has significant effect on weld quality. Current inspection methods for weld seams measure and investigate post factum and cannot prevent weld defects. Element burn-off may significantly affect solidification leading to embrittlement or cracking Control of weld chemical compositions insures a controlled solidification and resistance to related weld defects.
A laser-induced breakdown spectroscopy (LIBS) system was combined with a bead-on-plate Tungsten Inert Gas (TIG) welding process for the in situ measurement of chemical compositions in austenitic stainless steels during welding.Monitoring the weld pool's chemical composition allows governing the weld pool solidification behavior, and thus enables the reduction of susceptibility to weld defects. Conventional inspection methods for weld seams (e.g. ultrasonic inspection) cannot be performed during the welding process. The analysis system also allows in situ study of the correlation between the occurrence ofweld defects and changes in the chemical composition in theweld pool or in the two-phase regionwhere solid and liquid phase coexist. First experiments showed that both the shielding Ar gas and the welding arc plasma have a significant effect on the selected Cr II, Ni II and MnII characteristicemissions, namely an artificial increase of intensity values via unspecific emission in the spectra.
In situ investigations showed that this artificial intensity increase reached a maximum in presence of weld plume. Moreover, an explicit decay has been observedwith the termination of thewelding plumedue to infrared radiation during sample cooling. Furthermore, LIBS can be used after welding to map element distribution. For austenitic stainless steels,Mnaccumulations on both sides of theweld could be detected between the heat affected zone (HAZ) and the base material.