**1. Introduction**

The search for improvements in mechanized/automated welding processes has been in evidence for quite a long time, with remarkable recurrence and intensity nowadays due to shortage of qualified workforce. One way to exploit the mechanical/automated welding processes with

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more efficiency (productivity) has been through the combination of operating modes (polari‐ ty and/or metal transfer mode) within a single process, in addition to the possibility of combin‐ ing welding current levels. With the combination of operating modes (possible with modern power sources) andcurrentlevels inthe sameweldingoperation,itispossible tovarythe energy ofthe process, both thermal(heat delivered to the base metal) and mechanical(arc pressure and impact of droplets on the base metal,the latterin the case of consumable electrodes).In this line, aninterestingapproach,notmuchexploitedyet,butpromising,is tousethis featuretodistribute the energy of welding optimally into the workpiece to control the weld bead formation (molten materialfrom both electrode and workpiece). This could be done by synchronizing the welding operating modes and/or current levels with the position of the arc/torch. The arc position can be changedmechanically(bymovingthe torch) ormagnetically.Themagneticdeflectionof arcs (deviationofarc couplingwiththeworkpiecebyexternalmagnetic fields)isarelativelyversatile and inexpensive technique. The arc magnetic oscillation is composed of a series of magnetic deflections (pendulum-like movement of the arc when subjected to a variable and/or alternat‐ ing magnetic field). Once the electromagnetis positioned/mounted relative to the arc/torch and thereby the direction of the magnetic flux lines is defined (longitudinal for lateral/transversal oscillation and transversal for longitudinal oscillation), the extension of the arc movement in each position depends on the magnetic field level applied and the time spent in each position depends on the application time of the magnetic field. As shown in **Figure 1**, the direction of deflection (left and right or forward and backward in relation to the welding travel speed direction) depends on the direction of magnetic flux lines produced by the electromagnet; the inversion of arc positions/direction of deflection is given by the inversion of the electromag‐ net control signal (voltage/current).

form (amplitude and time) of the voltage/current signal applied to the electromagnet. A short schematic description of the idea of synchronizing the arc positions with its energy levels by the use of magnetic oscillation is shown in **Figures 2** and **3**. Examples of motivating applica‐ tions for the development of magnetic oscillation synchronized with welding processes are

**Figure 3.** Schematic welding transverse cross section with the arc at the centre, left, and right positions with different levels of thermal and mechanical energy in each position as result of synchronizing the arc positions with its energy

levels using magnetic oscillation in the case of transverse arc deflection.

**Figure 2.** Schematic description of the idea of synchronizing the arc positions with its energy levels using magnetic

Gas Tungsten Arc Welding with Synchronized Magnetic Oscillation

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55

oscillation.

**Figure 1.** Direction of magnetic deflection: on the left hand side—magnetic field parallel/aligned with the welding di‐ rection generates transversal/lateral arc deflection; on the right hand side—magnetic field transversal to the welding direction generates longitudinal arc deflection.

This work aims to better exploit the potential of magnetic oscillation. The overall goal is to synchronize the magnetic oscillation of the arc with the welding process (current levels), gas tungsten arc welding (GTAW) in this case, and evaluate the potential of this technique to control/modify the welding results, specifically in terms of the weld beads' external geometry. With the synchronization proposed, it would be possible to choose the thermal and mechanical energy of the arc (current levels) for each of its positions. The setting of arc position and time at each position with prechosen energies (welding current levels) is controlled by the wave‐ Gas Tungsten Arc Welding with Synchronized Magnetic Oscillation http://dx.doi.org/10.5772/64158 55

more efficiency (productivity) has been through the combination of operating modes (polari‐ ty and/or metal transfer mode) within a single process, in addition to the possibility of combin‐ ing welding current levels. With the combination of operating modes (possible with modern power sources) andcurrentlevels inthe sameweldingoperation,itispossible tovarythe energy ofthe process, both thermal(heat delivered to the base metal) and mechanical(arc pressure and impact of droplets on the base metal,the latterin the case of consumable electrodes).In this line, aninterestingapproach,notmuchexploitedyet,butpromising,is tousethis featuretodistribute the energy of welding optimally into the workpiece to control the weld bead formation (molten materialfrom both electrode and workpiece). This could be done by synchronizing the welding operating modes and/or current levels with the position of the arc/torch. The arc position can be changedmechanically(bymovingthe torch) ormagnetically.Themagneticdeflectionof arcs (deviationofarc couplingwiththeworkpiecebyexternalmagnetic fields)isarelativelyversatile and inexpensive technique. The arc magnetic oscillation is composed of a series of magnetic deflections (pendulum-like movement of the arc when subjected to a variable and/or alternat‐ ing magnetic field). Once the electromagnetis positioned/mounted relative to the arc/torch and thereby the direction of the magnetic flux lines is defined (longitudinal for lateral/transversal oscillation and transversal for longitudinal oscillation), the extension of the arc movement in each position depends on the magnetic field level applied and the time spent in each position depends on the application time of the magnetic field. As shown in **Figure 1**, the direction of deflection (left and right or forward and backward in relation to the welding travel speed direction) depends on the direction of magnetic flux lines produced by the electromagnet; the inversion of arc positions/direction of deflection is given by the inversion of the electromag‐

**Figure 1.** Direction of magnetic deflection: on the left hand side—magnetic field parallel/aligned with the welding di‐ rection generates transversal/lateral arc deflection; on the right hand side—magnetic field transversal to the welding

This work aims to better exploit the potential of magnetic oscillation. The overall goal is to synchronize the magnetic oscillation of the arc with the welding process (current levels), gas tungsten arc welding (GTAW) in this case, and evaluate the potential of this technique to control/modify the welding results, specifically in terms of the weld beads' external geometry. With the synchronization proposed, it would be possible to choose the thermal and mechanical energy of the arc (current levels) for each of its positions. The setting of arc position and time at each position with prechosen energies (welding current levels) is controlled by the wave‐

net control signal (voltage/current).

54 Joining Technologies

direction generates longitudinal arc deflection.

**Figure 2.** Schematic description of the idea of synchronizing the arc positions with its energy levels using magnetic oscillation.

form (amplitude and time) of the voltage/current signal applied to the electromagnet. A short schematic description of the idea of synchronizing the arc positions with its energy levels by the use of magnetic oscillation is shown in **Figures 2** and **3**. Examples of motivating applica‐ tions for the development of magnetic oscillation synchronized with welding processes are

**Figure 3.** Schematic welding transverse cross section with the arc at the centre, left, and right positions with different levels of thermal and mechanical energy in each position as result of synchronizing the arc positions with its energy levels using magnetic oscillation in the case of transverse arc deflection.

the ability to act differently on the geometry of the weld beads (molten and heat-affected zones), affect grain size for improvement of weld properties, allow weld pool control for outof-position welding operations, and facilitate narrow gap welding, root passes, among others.

proportional to the conductor length within the magnetic field, the electrical current flowing through this conductor and the magnetic flux density. Therefore, in welding, in a simplified manner, if a current *I* is flowing from the electrode to the workpiece through an arc of length *La* and this arc is in the presence of a magnetic field *Be* (externally produced by an electro‐ magnet, for example), a force *F* acting in the arc (perpendicular to the magnetic field and

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**Figure 5.** Diagrammatic explanation on how the deflection of an arc in the presence of an external magnetic field takes

Perhaps the main advantage of using magnetic oscillation is the virtually unlimited capability to create arc deflection patterns, either sideways or forward and backward relative to the direction of welding. Manufacturers of magnetic oscillation systems commonly point arc stabilization, arc positioning, heat distribution control, undercut minimization, porosity reduction, improved penetration, and uniform side melting in joints as advantages of this technique. In practical terms, the magnetic deflection is more adequate for high-frequency movements and with greater precision (no mechanism inertia, etc., typical of mechanical devices). Despite the fact that magnetic oscillation can be used in favour of welding, some

**2.1. Advantages and limitations of arc magnetic oscillation**

current flow) is generated.

place.
