D-2
MAINTENANCE AND TROUBLESHOOTING
D-2
ARC WELDING DEFECT AND PREVENTION METHOD
Problem
Possible Cause
What to do
Welding bead
doesn
’t
meet
the
requirement
The groove angle is not correct
The root face and assembly gap is not
equal.
Welding techniques are in correct.
Choosing the proper groove angle & assembly
gap, improve the assembly quality.
Choosing the correct welding parameters
Improve the operator skill.
Undercut
Over current
Arc length is too long
The electrode angle is wrong.
Choosing the correct welding current & travel
speed
Shorten the arc length
The electrode angle should be correct.
Incomplete
penetration
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 low.
Choose the correct process and groove size
Correctly assemble and ensure clearance
Choose the suitable welding current & speed
Improve the operator skill.
Incomplete
fusion
The welding thermal input is too low
There is rust or contamination on the side
of groove
The slag between the layers is not
removed completely.
Choose the correct welding parameters
Ensure joint is clean prior to welding
Ensure slag is removed between layers
Overlap
The temperature of molten pool is too high.
The liquid metal solidifies slowly
Choosing parameters based on the welding in
different positions.
Control the molten pool size
Crater
The crater time is too short.
Over current in the welding of thin plate.
In the crater, the electrode should be held for a
short time after the molten pool is filled in by
metal, take to the side for crater
Prorosity
There is some contamination on the work
piece surface and groove.
The coating of electrode is damp.
Under current or over speed in the welding.
The arc is too long or lean burning, the
molten pool protection is not sufficent
Over current, the coating of electrode falls
off or gas sheilding issues.
Clean around joint for about 20
～
30mm
Strictly to dry the electrode according to
manual.
Choose the correct welding parameters and
travel speed.
Using the short arc operation.
Welding operation in the field should have
protection from wind.
Inclusion
&
slag inclusion
The slag sticks to the middle layer in the
welding process.
Under current or over speed in the welding.
Welding operation is not correct.
The welding filler does not match the work
piece.
The groove design & processing are not
correct.
Choose the electrode with easy slag removal.
Ensure all slag is removed between runs.
Choose correct welding parameters
Use the correct electrode angle
Hot cracking
In the process of solidification, the 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.
Use low hydrogen electrodes.
Cold cracking
Three reasons will cause cold cracking:
The structure turned from the martensite
The residual stress caused by over
restraint
The residual hydrogen in welding gap.
Use low hydrogen type basic electrodes.
Bake electrodes per the instruction before use.
Reduce the percentage of hydrogen.
Adopt appropriate parameters and heat input.
After welding, do dehydrogenation at once.
