10 A Novel High-Efficiency Keyhole Tungsten Inert Gas …
327
failure of the keyhole can be seen as a process of splitting the liquid into two part
and pulling them towards to different sides of the weld seam.
10.2.5 Arc Forces in K-TIG Welding Keyhole
The interface between the liquid and solid metal can be found within the cavity of
the keyhole. The material that filled in this cavity is called the weld pool whose
surface is exposed to the air or shielding gas atmosphere. In K-TIG welding, a crater
is generally found at the end of the joint, which has similar shape as keyhole. The
terminal crater is caused by the absence of the metal at the end of the joint. The
volume of the cavity could be measured by suddenly stop the welding process, and
the deficit can also be determined. During the K-TIG welding, arc force is important
in causing the cavity, and it can also be described in formula.
10.2.5.1 Radial Force Due to Magnetic Field
When the current is flowing through the arc plasma, the radial incremental compressive force f jbr and internal pressure are balanced with each other. r arc is the radius
of the arc flowing, which is presented as r for convenient. The current I (r arc ) can be
expressed in a different form which is a function of the r arc , and the total radial force
F jbr is given by [26]
F jbr =
I 0
0
μI (r arc )
4π
dI (r arc ) =
μI
2
0
8π
(10.4)
10.2.5.2 Axial Force Due to Magnetic Field
The geometrically divergent within the arc causes electromagnetic force parallel to
the arc axis. The model of the arc starts from z = e and ends at z = a. Letting R e
and R a be the arc radius at these two planes, the axial magnetic force of the is given
by integration:
F jbz =
μI
2
0
4π
ln
R a
R e
+
R e
0
μI
2
(r, e)
4πr
dr −
R a
0
μI (r, a)
4πr
dr
(10.5)
The combination of J z × B θ and J r × B θ is equal to the net force on the molten
pool. Therefore, the arc force caused by the arc which is axial symmetry and has a
327
failure of the keyhole can be seen as a process of splitting the liquid into two part
and pulling them towards to different sides of the weld seam.
10.2.5 Arc Forces in K-TIG Welding Keyhole
The interface between the liquid and solid metal can be found within the cavity of
the keyhole. The material that filled in this cavity is called the weld pool whose
surface is exposed to the air or shielding gas atmosphere. In K-TIG welding, a crater
is generally found at the end of the joint, which has similar shape as keyhole. The
terminal crater is caused by the absence of the metal at the end of the joint. The
volume of the cavity could be measured by suddenly stop the welding process, and
the deficit can also be determined. During the K-TIG welding, arc force is important
in causing the cavity, and it can also be described in formula.
10.2.5.1 Radial Force Due to Magnetic Field
When the current is flowing through the arc plasma, the radial incremental compressive force f jbr and internal pressure are balanced with each other. r arc is the radius
of the arc flowing, which is presented as r for convenient. The current I (r arc ) can be
expressed in a different form which is a function of the r arc , and the total radial force
F jbr is given by [26]
F jbr =
I 0
0
μI (r arc )
4π
dI (r arc ) =
μI
2
0
8π
(10.4)
10.2.5.2 Axial Force Due to Magnetic Field
The geometrically divergent within the arc causes electromagnetic force parallel to
the arc axis. The model of the arc starts from z = e and ends at z = a. Letting R e
and R a be the arc radius at these two planes, the axial magnetic force of the is given
by integration:
F jbz =
μI
2
0
4π
ln
R a
R e
+
R e
0
μI
2
(r, e)
4πr
dr −
R a
0
μI (r, a)
4πr
dr
(10.5)
The combination of J z × B θ and J r × B θ is equal to the net force on the molten
pool. Therefore, the arc force caused by the arc which is axial symmetry and has a