OPERATION CONTROL AND CONNECTORS
15
Incomplete
penetratio
n
The groove angle or gap is too small, the
root face is too big
Welding parameters are not suitable, or the
assembly is not good
The welder’s operation skill is lower
Choose correct groove size
Assemble correctly to and ensure clearance
Choose a suitable welding current & speed
Improve the operation skill of welders
Incomplete
fusion
The welding thermal input is too low
The arc direction is lean
There are rust & dust on the side of groove
The slag between the layers is not cleared
well
Choose the correct welding parameters
Enhance the clearness of layers
Clean the area.
Remove all slag.
Overlap
The temperature of molten pool is too high
The liquid metal cools too slowly.
Choose correct parameters.
Pay attention to the molten pool and its
location.
Crater
The crater time lasts too short
Over current in the welding of thin plate
Hold the arc at the finish of the weld to fill the
crater of the weld pool before finishing the
weld.
Reduce current.
Blowhole
Dust, oil rust or water on the work piece
surface and groove
The coating of electrode is in poor condition.
Under current or over speed in the welding
The arc is too long or lean burning, the
molten pool protection is not good
Over current, the coating of electrode falls
off and protection is lost.
Manipulation of electrode is not correct
Clear out the dust around groove for about
20
～
30mm
Dry the electrodes to guidelines.
Choose correct parameters
Keep a close arc
Inclusion & slag
inclusion
The slag clears bad in the middle layer in the
welding process
Under current or over speed in the welding
Welding operation is not correct.
The welding material cannot match the work
piece
The groove design & processing are not
proper
Choose the correct electrode
Clean slag from between runs.
Choose correct parameters.
Utilize correct electrode angle and
manipulation.
Hot crack
In the process of solidification, inter crystal
segregation is caused. At the same time,
with the effect of welding stress, the hot
crack is formed.
Strictly control the percentage of S and P in
welding material.
Adjust the structure of welding material.
Adopt the basic electrode.
Cold crack
Three reasons will cause cold crack:
The structure turned from the marten site
The residual stress caused by big restraint
intensity
The residual hydrogen in welding gap.
Adopt low hydrogen type basic electrode.
Preheat as required.
Reduce the percentage of hydrogen
Adopt appropriate parameters and heat input
After welding, do dehydrogenation at once.
4.7 Operational Environment
·Height above sea level is below 1000m.
·Operation temperature range: -10
℃
～
+40
℃
.
·Relative humidity is below 90 % (+20
℃
). relative humidity is below 50 % (40
℃
).
· The inclination of the power source must not exceed 10°.
·Protect the machine against heavy rain or in hot circumstance against direct
sunshine.
·The content of dust, acid, corrosive gas in the surrounding air or substance
