Sweiss SKYMAX 2040 Nx Manual De Usuario página 81

Defect name
Overlap
Crater
Blowhole
Inclusion &
slag
inclusion
Hot crack
Cold crack
Caused reasons
The temperature of molten pool
is too high.
The liquid metal concretes slowly.
The crater time lasts too short
Over current in the welding of thin plate
There are some dust like oil, rust or
water on the work piece surface and
groove.
The coating of electrode is damped
& is not drying.
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 o and lose
protection.
Manipulation of electrode is not
proper.
The slag clears bad in the middle
layer in the welding process.
Under current or over speed in the
welding.
Welding operation is not proper
The welding material can not match
the work piece.
The groove design & processing are
not proper.
In the process of solidi cation, the
inter crystal segregation is seriously
caused. At the same time, with the
e ect of welding stress, the hot crack
is formed.
Three reasons will cause cold crack:
The structure turned from the
molten site
The residual stress caused by big
restraint intensity
The residual hydrogen in welding
gap.
33 SWEISSWELD.COM
Prevent methods
Choosing parameters based on
the welding di erent position
Strictly to control the molten
hole size.
In the crater, electrode should be
stayed for a short time or round to
manipulate electrode
after the molten pool is lled in by
metal, take to the side for crater
Clear out the dust around groove
for about 20〜30mm.
Strictly to dry the electrode
according to manual.
Correctly to choose parameters
and to operate.
Using the short arc operation
Welding operation in the eld
should have antiwind protection.
Don't use the invalid electrode.
Choosing the electrode of good
slag detachability.
Strictly to clear the slag in the
layers.
Correctly to choose the welding
parameters.
Adjusting the electrode angle
and manipulation way.
Strictly control the percentage of
S and P in welding material.
Adjust the structure of welding
material.
Adopt the basic electrode.
Adopt low hydrogen type basic
electrode.
Bake under the instruction before use.
Remove the feculence before use, reduce
the percentage of hydrogen.
Adopt appropriate parameters and heat
input.
After welding, do dehydrogenation at
once.