10 A Novel High-Efficiency Keyhole Tungsten Inert Gas …
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the voltage and current could be got through serious of experiments under a certain
welding condition.
10.2.2.4 Shielding Gas
One of the influence of the shielding gas flow is that it will change the transformation
of the heat and momentum, so the changing of its composition has influence on the
threshold current. For pure argon, adding helium into the pure argon increases the
threshold current while adding nitrogen or hydrogen reduces it, as shown in Fig. 10.6.
When other parameters were fixed, the threshold current in pure argon was 40%
higher than in mixture of Ar-10 N.
Different strategies of the gas backing were compared in the K-TIG welding in
C–Mn steel carried out by Liu. The weldments were jointed with gas shielding. In
addition, more tests are carried out with argon as covering and jet flow on the back,
respectively. It showed that unstable keyhole existed without gas backing, and a
narrow range of current from 410 to 450 A was suitable for keeping a stable keyhole.
When the gas jets of argon flowed towards the back of the weldment, the current
range could be expanded to 420–560 A. This finding gives a possible method to get
a stable weld pool during full penetration welding [16].
Fig. 10.6 Two different kinds of backing gas shielding. a K-TIG with static backing gas shielding.
b K-TIG with jet flow gas [16]
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the voltage and current could be got through serious of experiments under a certain
welding condition.
10.2.2.4 Shielding Gas
One of the influence of the shielding gas flow is that it will change the transformation
of the heat and momentum, so the changing of its composition has influence on the
threshold current. For pure argon, adding helium into the pure argon increases the
threshold current while adding nitrogen or hydrogen reduces it, as shown in Fig. 10.6.
When other parameters were fixed, the threshold current in pure argon was 40%
higher than in mixture of Ar-10 N.
Different strategies of the gas backing were compared in the K-TIG welding in
C–Mn steel carried out by Liu. The weldments were jointed with gas shielding. In
addition, more tests are carried out with argon as covering and jet flow on the back,
respectively. It showed that unstable keyhole existed without gas backing, and a
narrow range of current from 410 to 450 A was suitable for keeping a stable keyhole.
When the gas jets of argon flowed towards the back of the weldment, the current
range could be expanded to 420–560 A. This finding gives a possible method to get
a stable weld pool during full penetration welding [16].
Fig. 10.6 Two different kinds of backing gas shielding. a K-TIG with static backing gas shielding.
b K-TIG with jet flow gas [16]