Revisiting fundamental welding concepts to improve additive manufacturing: From theory to practice

Gas tungsten arc welding of as-rolled CrMnFeCoNi high entropy alloy

https://run.unl.pt/bitstream/10362/76536/1/Microstructure_and_mechanical_properties.pdf

Microstructure and mechanical properties of gas tungsten arc welded Cu-Al-Mn shape memory alloy rods

Arc behaviour is a significant factor in all arc welding processes. Understanding of arc types and their inherent properties can help enhance weld prediction and weld quality and reduce welding cost and production cycle time. Advanced welding processes utilize real-time control and prediction, increasing the need for detailed knowledge of arc characteristics and arc applications. This paper analyses the types of welding arcs used in the welding industry, explains corresponding features and characteristics, provides guidance for suitable applications, and presents arc type comparisons, benefits, and weaknesses. The study is based on a review of the literature, and it provides a comprehensive overview of arc phenomena. The results of this work show that in many applications, greater benefit accrues from spray and pulsed arcs than short and globular arc modes. Controlled short arc, heavy deposition rate arc, and controlled spray arc are enhanced arc processes offering significant improvements in efficiency and usability. This review can assist companies in making appropriate choices of arc and welding process for different materials and applications. Furthermore, it can be utilized as a basis for further research.

/pdf/usability-of-arc-types-in-industrial-welding-34uxyhd6bo.pdf

Usability of arc types in industrial welding

Control of welding parameters is an important factor in gas metal arc welding (GMAW) because these parameters determine the heat input, cooling conditions, and time during which the microstructure and the geometry of the weld are formed. It is therefore essential that sufficient heat is transferred to highly conductive metals like aluminum and appropriate heat input used with very sensitive metals such as stainless steel and high-strength steels or when welding dissimilar metals. The objective of this study is to identify parameters of current, voltage waveforms, and electrode feeding motion that directly contribute to improvement in metal and heat transfer conditions from the electrode to the base metals. The effects of these parameters on welded joint geometry are determined. The work critically reviews research on the effect on welded joints of control of current waveform, voltage, and the alternating electrode and analyzes the different parameters that promote forces acting during metal transfer. Experiments and case studies based on controlled waveforms are discussed. The analysis shows that in controlled short-circuit gas metal arc welding (CS-GMAW), all identified parameters contribute to control of heat input and reduction in the amount of spatter and fumes generated. Variable polarity gas metal arc welding (VP-GMAW) is found to be particularly effective for aluminum welding because of its good control of mass metal transfer and weld penetration. Mixed waveform approaches (i.e., 20 pulses/controlled short circuit) improve weldability in difficult welding positions.

Review of current waveform control effects on weld geometry in gas metal arc welding process

Optimization procedures for GMAW of bimetal pipes

Butting bimetal pipes in duplex stainless steel are quite recent and present a set of interesting characteristics especially for oil and gas transportation, namely weight to corrosion resistance ratio. Gas tungsten arc (GTA) welding is used to join these pipes, but several problems are identified as lack of penetration and cracking resulting not only from the material itself, but also from the difficulty to weld in orbital position. In the present work, autogenous GTA pipe welding and pulse Rapid Arc gas metal arc welding of the pipes were studied. Current intensity, welding speed, electrode diameter, shielding gas and orbital positions were defined as variables. It was shown that under appropriate conditions, it is possible to obtain sound welds with proper geometry and defect free. The major limitation to penetration is the outwards flow pattern in the molten pool driven by the Marangoni effect, as a result of low sulphur content. Sulphur is an active surface element which reverses the surface tension coefficient to a positive effect. For penetrations of about 2 mm, a combination of current intensity of 170 A and a welding speed of 200 mm/min with an electrode angle of 30° under a shielding gas protection of He–25%Ar was defined for narrow groove welding of a J-bevelled pipe in flat position. No defects were detected in the inner layer in duplex stainless steel.

A. M. Torbati

Papers

Optimization procedures for GMAW of bimetal pipes

Welding bimetal pipes in duplex stainless steel