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Y. Shi et al.
no fluxes, GTAW is considered as a clean welding process. Usually, low welding
currents is needed so the arc pressure performed on the surface of the liquid metal
is not enough. In this case, the bottom part of the metal weldment absorbs the heat
from the top in a way of heat conduction. For thicker weldment, edges preparation is
necessary to form V- or X-type edges. Otherwise, filler material and multiple passes
have to be added to complete the joint which leads to the time and economy cost [1].
GTAW can be operated under high current (>300 A) which results in the greater
penetration of the joint. As the current goes up, the arc pressure increases and forcing
the melting material going down which is called the displacement of the weld pool.
Joins between square-edged sections can be produced with this method. During the
process of this variant, a larger amount of heat can be transferred to the weldment
when the electrode works as the cathode. Besides, these advantages enable it to
become a popular manually welding method.
Goryachev seems to be the first researcher to carry out high-current GTAW tests
to form displacement of weld pool under the arc [2]. Liptak successfully welded the
aluminium plate with the thickness of 32 mm [3]. After that, more materials including
stainless steel, low-alloy steel and magnesium alloy were tested to be welded with
this method [4].
However, the control of the weld penetration is hard, especially if the weld is
not fully penetrating. Besides, some defects like hollow bead may appear when the
current is over 350 A, and the process may become unstable when it exceeds 500 A.
These situations can be improved by using hollow electrode [5].
Deep penetration welding with keyhole is usually seen as another kind of GTAW
with a cooling system. One of its advantage is to overcome these problems and has
gained significant industrial credibility. The displacement of the molten material
under high current results in a hole under the welding arc. Thus, the arc is thought
to be buried under the weld pool for a full penetration of the weldment. Therefore,
K-TIG welding has been seen as a suitable way to realize some welding with special
needs and has potential application in industrial production.
10.1.2 Keyhole Tungsten Inert Gas (K-TIG) Welding
The keyhole TIG welding connects metal weldment by forming small holes in the
weld bead. It happens if adequate heat is input melting the metal, and the increased
arc pressure widens the holes and push it to the bottom of the weldment. Then, the
keyhole will be formed. The formation of the keyhole can form a narrow channel
between the surface and the inside of the plate, which can directly transfer the energy
to the joint and improve the energy transfer efficiency compared. Besides, a little hole
at the weldment’s bottom side becomes a new way for the gas leaking away.
Its physical characteristic makes it unique and suitable for those material whose
thermal conductivity is low. Stainless steel and titanium alloy both belong to this
range of the materials, and some other expensive materials require a high quality
and good appearance. As a result, forming keyhole enables the fabricator to produce
Y. Shi et al.
no fluxes, GTAW is considered as a clean welding process. Usually, low welding
currents is needed so the arc pressure performed on the surface of the liquid metal
is not enough. In this case, the bottom part of the metal weldment absorbs the heat
from the top in a way of heat conduction. For thicker weldment, edges preparation is
necessary to form V- or X-type edges. Otherwise, filler material and multiple passes
have to be added to complete the joint which leads to the time and economy cost [1].
GTAW can be operated under high current (>300 A) which results in the greater
penetration of the joint. As the current goes up, the arc pressure increases and forcing
the melting material going down which is called the displacement of the weld pool.
Joins between square-edged sections can be produced with this method. During the
process of this variant, a larger amount of heat can be transferred to the weldment
when the electrode works as the cathode. Besides, these advantages enable it to
become a popular manually welding method.
Goryachev seems to be the first researcher to carry out high-current GTAW tests
to form displacement of weld pool under the arc [2]. Liptak successfully welded the
aluminium plate with the thickness of 32 mm [3]. After that, more materials including
stainless steel, low-alloy steel and magnesium alloy were tested to be welded with
this method [4].
However, the control of the weld penetration is hard, especially if the weld is
not fully penetrating. Besides, some defects like hollow bead may appear when the
current is over 350 A, and the process may become unstable when it exceeds 500 A.
These situations can be improved by using hollow electrode [5].
Deep penetration welding with keyhole is usually seen as another kind of GTAW
with a cooling system. One of its advantage is to overcome these problems and has
gained significant industrial credibility. The displacement of the molten material
under high current results in a hole under the welding arc. Thus, the arc is thought
to be buried under the weld pool for a full penetration of the weldment. Therefore,
K-TIG welding has been seen as a suitable way to realize some welding with special
needs and has potential application in industrial production.
10.1.2 Keyhole Tungsten Inert Gas (K-TIG) Welding
The keyhole TIG welding connects metal weldment by forming small holes in the
weld bead. It happens if adequate heat is input melting the metal, and the increased
arc pressure widens the holes and push it to the bottom of the weldment. Then, the
keyhole will be formed. The formation of the keyhole can form a narrow channel
between the surface and the inside of the plate, which can directly transfer the energy
to the joint and improve the energy transfer efficiency compared. Besides, a little hole
at the weldment’s bottom side becomes a new way for the gas leaking away.
Its physical characteristic makes it unique and suitable for those material whose
thermal conductivity is low. Stainless steel and titanium alloy both belong to this
range of the materials, and some other expensive materials require a high quality
and good appearance. As a result, forming keyhole enables the fabricator to produce