CALIDAD
CALIDAD
WHAT IS UNDERCUT? A DEFECT OR DISCONTINUITY.
Undercut is a surface discontinuity that occurs in the base metal directly adjacent to the weld bead; depending…
The work of a welder is not only to join metals, but to do everything possible to ensure that this joint is made in the best way and that the weld beads do not present discontinuities and defects. The work of metallurgical surgeons (Welders) is to produce quality weld joints; to do so, they must know what a defect is and what a discontinuity is.
Defect. It is an interruption that can occur in the weld metal and must be repaired; that is, a defect can cause an accident or fracture of the weld material, which is why codes and standards do not accept defects.
Discontinuity. It is any interruption that is very small and is not considered a defect; therefore, it is acceptable in a weld bead. Below, we will review the most relevant welding defects.
SPATTER AND SPARKING
Causes.
- Arc blow.
- Amperage too high.
- Arc length too long.
- Defective electrode.
- Improper technique.
How to correct it
- Ensure a proper ground connection.
- Adjust the amperage according to the electrode type and diameter.
- Adjust the arc to the proper length.
- Use the appropriate electrode.
- Use the correct polarity.
- Clean properly.
ARC STRIKES.
Cause
- Arc initiation outside the bevel or joint.
- Current too low.
- Poor ground connection.
- Buildup of coating at the electrode tip.
How to correct it
- Set the current properly.
- Clean the workpiece thoroughly (wire brush).
- Connections must be completely clean.
- Clean the electrode tip.
- Visualize the joint.
SLAG INCLUSIONS
Cause
- Arc length too short.
- Improper electrode manipulation.
- Current too low.
- Insufficient cleaning of each weld bead.
How to correct it
- Use a medium arc length.
- Maintain a wide molten weld pool.
- Use the recommended current and travel speed.
- Remove all slag residue from the bead before applying the next pass.
POOR APPEARANCE OR LACK OF UNIFORMITY.
Cause
- Poor quality electrode.
- Improper electrode usage.
- Overheating.
- Long arc; excessive amperage and voltage.
How to correct it
- Use certified electrodes.
- Use the recommended technique.
- Avoid overheating.
- Use the correct arc length, and the amperage and voltage values recommended by the manufacturer.
- Use uniform travel movements.
POROSITY
Cause
- Short arc, except with stainless or low-hydrogen electrodes.
- Insufficient fusion time.
- Excessive amperage.
- Dirty base material.
- Damp coating.
- Excessive travel speed.
How to correct it.
- Maintain a longer arc length.
- Allow sufficient fusion time for gases to escape.
- Use appropriate amperage.
- Clean the surface thoroughly.
- Dry the electrode.
- Use an appropriate travel speed.
LACK OF PENETRATION AND INCOMPLETE FUSION
Cause
- Excessive travel speed.
- Electrode diameter too large.
- Amperage too low.
- Defective penetration.
How to correct it
- Leave sufficient root opening at the bottom.
- Select the appropriate electrode.
- Use sufficient amperage to achieve the desired penetration.
- Correctly calculate electrode penetration.
- Correct the travel speed.
- Clean the joint of foreign matter.
UNDERCUT
Cause
- Improper electrode manipulation.
- Use of incorrect electrode diameter.
- Excessive amperage.
How to correct it
- Use a uniform weaving motion in butt welding.
- Avoid using electrodes with larger diameters.
- Use appropriate amperage.
- Avoid excessive welding.
- Hold the electrode at a safe distance from the vertical plane when making horizontal fillet welds.
CRACKS
Causes
- Inappropriate electrode.
- Weld size disproportionate to the base metal thickness.
- Defective welds.
- Defective joint preparation.
- Rigid joint.
How to correct it.
- To eliminate rigid joints, adopt an appropriate structural design and method.
- Match the electrode diameter to the base metal thickness.
- Avoid sequential bead-on-bead welds.
- Keep the joint edges unrestrained for as long as possible.
- Make sound welds with good fusion.
- Preheat the workpieces.
- Ensure that joints have a uniform and adequate root gap between plates.
- Work with the lowest amperage possible.
- Use low-hydrogen electrodes.