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Remanufacturing and Advanced Machining
the material. As a rule, PAC employs plasma gases Ar, N, H 2 or their mixtures,
the torch is often equipped with a secondary shielding gas flow that surrounds the
plasma to confine it and clean the kerf. A variant of the process is carbon arc cutting (CAC), where carbon electrodes and an air flux are applied (Biesuz et al., 2021).
Most plasma cutting machines are dedicated to rather simple processing, without
loading/unloading automation, and they commonly work with a single piece at a
time with limited geometries (Kanyilmaz, 2019). PAC is a productive method for
linear cutting or 2D profiles, but if a second cut plan is required, engineers tend
to use traditional tools. Nevertheless, plasma arc cutting has acquired a massive
ground in the industry (Gani et al., 2021).
Among methods shaping a workpiece, plasma arc drilling is widely applied to
materials processing. It is a novel drilling method that has emerged in recent years
to overcome such problems as tool wear and low efficiency in the drilling of thick
plates or plates made of difficult-to-machine materials. It provides high-quality
drilled holes. For drilling of a 12 mm thick mild steel plate, a penetration time of
about 0.75 s, a minimum specific energy of about 30 J/mm 3 , and a maximum material removal rate of about 300 mm 3 /s are reported (Sun and Kusumoto, 2010).
In the plasma arc welding (PAW) process, the arc can pass through a nozzle
which constricts the arc reducing its cross-sectional area. As a result of increased
energy density and velocity of the plasma, the temperature dramatically increases
to ca. 25,000°C. Plasma arc welding uses nonconsumable tungsten electrodes and
shielding gas (Sahoo and Tripathy, 2021). According to the process current, three
types of plasma arc welding processes can be distinguished:
1. Micro-plasma arc welding with a forming current below 15 A. It produces
low energy density and low plasma velocity and thus is suitable for thin
sheet processing.
2. Melt-in mode plasma arc welding, where current varies between 15 and
400 A. It is usually applied to the welding of thicker, up to 2.4 mm sheets.
3. Keyhole mode plasma arc welding is used for 2.5-mm thick materials. The
plasma-forming current works at more than 400 A.
To improve weld efficiency in terms of mechanical strength, weld penetration at a
low cost, and faster production, the process can be modified in different ways, e.g.,
by varying the plasma formation current range, applying different orifice diameters
to adjust plasma gas flow rate and thus to increase weld penetration and stability
of the arc. Just to name several techniques aimed at increasing the weld efficiency,
variable polarity plasma arc welding, double-sided arc welding, ternary gas plasma
arc welding, laser-assisted plasma arc welding, PAW–MIG hybrid welding process,
soft plasma arc welding, plasma spot welding process, manual pulse keyhole plasma
arc welding, or increased power density plasma arc welding can be listed (Sahoo and
Tripathy, 2020).
The arc used in PAW has a much higher velocity (300–2,000 m/s) and heat input
intensity (10 9 –10 10 W/m 2 ) than that in conventional gas tungsten arc welding (GTAW).
As a consequence, PAW has many advantages over GTAW, namely (Wu et al., 2014):
Remanufacturing and Advanced Machining
the material. As a rule, PAC employs plasma gases Ar, N, H 2 or their mixtures,
the torch is often equipped with a secondary shielding gas flow that surrounds the
plasma to confine it and clean the kerf. A variant of the process is carbon arc cutting (CAC), where carbon electrodes and an air flux are applied (Biesuz et al., 2021).
Most plasma cutting machines are dedicated to rather simple processing, without
loading/unloading automation, and they commonly work with a single piece at a
time with limited geometries (Kanyilmaz, 2019). PAC is a productive method for
linear cutting or 2D profiles, but if a second cut plan is required, engineers tend
to use traditional tools. Nevertheless, plasma arc cutting has acquired a massive
ground in the industry (Gani et al., 2021).
Among methods shaping a workpiece, plasma arc drilling is widely applied to
materials processing. It is a novel drilling method that has emerged in recent years
to overcome such problems as tool wear and low efficiency in the drilling of thick
plates or plates made of difficult-to-machine materials. It provides high-quality
drilled holes. For drilling of a 12 mm thick mild steel plate, a penetration time of
about 0.75 s, a minimum specific energy of about 30 J/mm 3 , and a maximum material removal rate of about 300 mm 3 /s are reported (Sun and Kusumoto, 2010).
In the plasma arc welding (PAW) process, the arc can pass through a nozzle
which constricts the arc reducing its cross-sectional area. As a result of increased
energy density and velocity of the plasma, the temperature dramatically increases
to ca. 25,000°C. Plasma arc welding uses nonconsumable tungsten electrodes and
shielding gas (Sahoo and Tripathy, 2021). According to the process current, three
types of plasma arc welding processes can be distinguished:
1. Micro-plasma arc welding with a forming current below 15 A. It produces
low energy density and low plasma velocity and thus is suitable for thin
sheet processing.
2. Melt-in mode plasma arc welding, where current varies between 15 and
400 A. It is usually applied to the welding of thicker, up to 2.4 mm sheets.
3. Keyhole mode plasma arc welding is used for 2.5-mm thick materials. The
plasma-forming current works at more than 400 A.
To improve weld efficiency in terms of mechanical strength, weld penetration at a
low cost, and faster production, the process can be modified in different ways, e.g.,
by varying the plasma formation current range, applying different orifice diameters
to adjust plasma gas flow rate and thus to increase weld penetration and stability
of the arc. Just to name several techniques aimed at increasing the weld efficiency,
variable polarity plasma arc welding, double-sided arc welding, ternary gas plasma
arc welding, laser-assisted plasma arc welding, PAW–MIG hybrid welding process,
soft plasma arc welding, plasma spot welding process, manual pulse keyhole plasma
arc welding, or increased power density plasma arc welding can be listed (Sahoo and
Tripathy, 2020).
The arc used in PAW has a much higher velocity (300–2,000 m/s) and heat input
intensity (10 9 –10 10 W/m 2 ) than that in conventional gas tungsten arc welding (GTAW).
As a consequence, PAW has many advantages over GTAW, namely (Wu et al., 2014):