729 Causes of defects in MMA Welding
Defect name
Cause of occurrence
Preventive countermeasures
blowhole
Bad or damp electrode
Welds with grease stains or rust
Go too fast
Current is too strong
Arc length does not fit
Heavy thickness of weldment and rapid cooling of metal
Excessive wind speed
Select appropriate electrode and pay attention to drying
Clean the welded part before welding
Slow down and make internal gas easy to spill
Use appropriate current
Adjust appropriate arc length
Carry out proper preheating work
Windshield
Welding corrosion
1. Current is too strong
2. Electrode not suitable
3. Arc too long
4. Bad method of operation; the speed of moving the rod is too fast.
5. Base metal is unclean
6. Base metal overheating
1. Use lower current
2. Select appropriate types and sizes of electrode
3. Maintain an appropriate short arc
4. Right angle, slower speed, shorter arc and narrower weaving
5. Remove solder grease or rust
6. Use a smaller electrode
[化] cinder inclusion
1. The welding slag of the front layer is not completely removed.
2. Welding current is too low
3. Welding speed is too slow
4. Electrode weaving too wide
5. Bad slotted shape design
1. Thoroughly remove front welding slag
2. Higher current
3. To increase the speed of welding; chase the slag behind the weld pool.
4. Reduce electrode weaving width
5. Correct appropriate slotting angle and clearance
Bad appearance
1. Electrode moisture absorption
2. Run the rod too fast or too slow.
3. Welding current is too high, electrode diameter is too thick
4. Weld overheating
5. Base metal is not clean
1. Select appropriate electrode and reweld after drying
2. Adopt uniform and appropriate speed and welding sequence; pay attention to the angle of welding rod and the covering property of welding slag
3. Select the appropriate current and the electrode with the proper diameter
4. Lower current and interlaminar temperature
5. Remove the dirt from the base metal
Insufficient penetration
1. Electrode inappropriate
2. Current is too low
3. The speed of the process is too fast to increase the temperature is not enough, and the speed of the arc is too slow to be blocked by the welding slag, can not reach the base metal
4. The slotting angle is too small, the root surface gap is too narrow, and the root is too deep.
1. Choose a more penetrating electrode
2. Use appropriate higher current
3. Correct proper speed, pay attention to arc length and angle, make welding slag and weld pool distinct, prevent welding slag from flowing into groove first to prevent penetration of arc.
4. Increase slotting degree and clearance, and reduce root depth
lapping
1. Current is too low
2. The speed is too slow; the electrode is not angled properly.
3. Wire diameter is too large
1. Use the appropriate current
2. Use the right Speed and Angl
3. Use a smaller diameter electrode
be out of shape
1. Overheating of base metal; too large heat-affected zone
2. Too many welding layers
3. Improper welding sequence
4. Insufficient preparation for construction; no amount of deformation reserved for false welding
5. Base metal cooling overspeed
6. Poor design of grooves and welds
1. Select electrode with low permeability
2. Use of large electrode and high current
3. Correct welding order
4. Fix the weldment before welding to avoid warpage; reserve the amount of deformation during false welding
5. Avoid overcooling or preheating of base metal
6. Reduce weld gap, slotting degree
be full of cracks
1. The base metal contains too much carbon, manganese and gold
2. Electrode of poor quality or humidity
3. Weld restraint force is too strong
4. Too high sulfur content in base metal is not suitable for welding
5. Insufficient preparation for construction
6. The base metal is thicker and the cooling rate is too fast.
7. Current is too strong
8. There's too little molten metal in the first.
9. Indentation and malaise at the end of the tail
1. Use of low hydrogen electrode with high base degree
2. Use suitable electrode and pay attention to drying
3. Improved structural design, pay attention to welding sequence, heat treatment after welding
4. Avoid the use of bad steel
5. Warm-up or post-heat should be taken into account in welding
6. Preheating base metal
7. Use appropriate current
8. The first weld metal shall be sufficient to resist shrinkage stress
9. To fill the indentation of the end.
Indentation (pinhole)
1. Improper use of electrode
2. Wet electrode
3. Base metal cooling overspeed
4. Unclean electrode and base metal
5. Weld contains carbon and manganese content is too high
1. Use an appropriate electrode, if not eliminated, with a low hydrogen electrode
2. Use a dry electrode
3. Reduce welding speed, avoid rapid cooling, preferably preheat or post-heat
4. Remove unclean matter
5. Use of low hydrogen electrode with high base degree
