Han dinh (E)

Subject 7 Butt welding of thin steel plate in flat position
1. Finished image
2. Materials
(1) The size of materials
1
 Back bead
5. Tack welding and its position
(1) Tack welding condition
Tack welding current 120 A
Arc voltage 19~20 V
CO
2
flow rate 15 L/min
Crater-filler switch “OFF”
(2) How to do tack welding and its position
 Do tack welding at the opposite side that
file the material.
 Decide the root gap (G) of material.
 Do tack welding at both ends of material.
 After doing tack welding, check the deformation of the part of butt-
welding joint.
 Do not set present distortion method.
6. Welding of the first layer by forehand welding
(1) Welding condition
Welding current 90~110A Crater-filler switch
OFF  ON
Arc voltage 19~20V Crater-filler current A
CO
2
flow rate 15 L/min Crater-filler voltage V
2

(2) Operating angle of the welding torch
[Notes]
1. Molten pool
2. Arc
3. Roundness cut
3
■ Start the arc at the end of material.
Good Not Good
1■ Operating angle of the welding torch that see
from the front of the welding direction.
2■ Aim the arc (wire tip) at the center of root gap
of square (I) groove joint.
[[Notes]
1. Molten pool
2. Arc
3. Roundness cut
(4) Treatment of the end of welding

Return to
starting
point
about 5～
10 mm at
the
welding
end slowly
then fill the crater by melting wire.
7. Self-check
 Adherence of slag
 Adherence of spatters

 Uniformity of bead appearance
 Uniformity of bead width
 Uniformity of reinforcement of weld
 Treatment at welding starting point
 Treatment at welding end
 Undercuts
4
 If do welding with weaving motion, the width of
weaving is the root gap or under.
(2) In case undercuts occur after
welding.
5