Ip and Ib and their continuous time tp and tb can be regulated according to requirements of the
process. The amplitude value of electric current changes periodically with certain frequency in
case of the pulse current , molten bath will be formed in the workpiece and the molten bath
will be solidified in case of base current. The welding seam is formed by reciprocal overlaps .
Welding heat input can be controlled by regulating pulse frequency, pulse current amplitude,
size of base current, continuous time of pulse current and base current and therefore the
welding seam, size and quality of the zone influenced from heat can be controlled.
(2) Advantages and application scope of pulse argon gas tungsten arc welding
a. Precisely control the size of the bath inputting heat to workpiece to increase penetration
resistance of molten seam and preservation of bath. It is easy to obtain even fusing deepness.
This process is specially applicable to omni - bearing welding of sheet and formation to be
done with both sides through one side welding.
b. Heating and cooling of each welding point is very fast . Therefore, the process is applicable
for the workpiece with great difference of heat conductivity and thickness.
c. Pulse arc can obtain greater fusing deepness with lower heat input. Therefore, under the same
condition, the zone influenced from welding heat and deformation from welding
can be reduced. This is very important for sheet and ultra -thin sheet welding.
d. Fast cooling of the bath metal and short duration time of high temperature during welding can
reduce cracks caused to the thermo-sensitive materials during welding.
(3) Selection of welding parameters
Except for pulse current and the width time(width ratio) as well as pulse frequency,welding
parameters of pulse argon gas tungsten arc welding are same as general tungsten DC argon
arc welding. Pulse current increasing means electric arc can obtain greater penetration ability.
But too much current can cause local melting of tungsten electrode. Generally, welding
CUR.
(A)
T (s)
t1
gas sending
in advance
arcing
up-slope
welding process
down-slope
arcing off
after flow
tp tb
T
Ip
Ib
Ip--pulse current
Ib--base current
tp--width time of pulse current
width time of base current
tb--
tp+tb=T
tp
tb
--- = D pulse width