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OPERATION CONTROL AND CONNECTORS
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4.6 Arc Welding Defect and Prevent Method
Defect name
Caused reasons
Prevent methods
Welding
The groove angle is not proper
Choosing the proper groove angle & assembly
seam
The root face and assembly gap is not equal gap, improve the assembly quality
doesn’t
Welding
technics
parameters
are
Choosing the proper welding parameters
meet the
unreasonable
Improve the operation skill of welders
requirement The welder’s operation skill is lower
Over current
Choosing the proper welding current & speed
Undercut
Arc length is too long
The arc can’t be drawn too long
The electrode angle is wrong
The electrode angle should be proper
Manipulation of electrode is not proper
Manipulation of electrode should be correct
The groove angle or gap is too small, the root Correctly to choose and process the groove
Incomplete face is too big
size
Welding parameters are not suitable, or the Correctly to assemble and ensure clearance
penetration assembly is not good
Choosing the suitable welding current & speed
The welder’s operation skill is lower
Improve the operation skill of welders
The welding thermal input is too low
Incomplete The arc direction is lean
Correctly to choose the welding parameters
There are rust & dust on the side of groove Operation seriously
fusion
The slag between the layers is not cleared Enhance the clearness of layers
well
The temperature of molten pool is too high Choosing parameters based on the welding
Overlap
different position
The liquid metal concretes slowly
Strictly to control the molten hole size
In the crater, electrode should be stayed for a
Crater
The crater time lasts too short
short time or round to manipulate electrode
Over current in the welding of thin plate
after the molten pool is filled in by metal, take
to the side for crater
There are some dust like oil, rust or water on Clear out the dust around groove for about
the work piece surface and groove
20 30mm
The coating of electrode is damped& is not
Strictly to dry the electrode according to
drying
manual
Under current or over speed in the welding
Blowhole
Correctly to choose parameters and to operate
The arc is too long
or lean burning, the
Using the short arc operation
molten pool protection is not good
Welding operation in the field should have
Over current, the coating of electrode falls
anti-wind protection
off and lose protection
Don’t use the invalid electrode
Manipulation of electrode is not proper
The slag clears bad in the middle layer in the
welding process
Choosing the electrode of good slag
Inclusion & Under current or over speed in the welding detachability
Welding operation is not proper
～
slag
Strictly to clear the slag in the layers
The welding material
can not match the Correctly to choose the welding parameters
inclusion
work piece
Adjusting the electrode angle
and
The groove design & processing are not
manipulation way
proper
In the process of solidification, the inter Strictly control the percentage of S and P in
Hot crack
crystal segregation is seriously caused. At the welding material.
same time, with the effect of welding stress, Adjust the structure of welding material.
the hot crack is formed.
Adopt the basic electrode.
Three reasons will cause cold crack:
Adopt low hydrogen type basic electrode.
Bake under the instruction before use.
The structure turned from the marten site
Remove the feculence before use, reduce the
Cold crack
The residual stress caused by big restraint percentage of hydrogen
intensity
Adopt appropriate parameters and heat input
The residual hydrogen in welding gap.
After welding, do dehydrogenation at once.
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