According to the American Society of Mechanical Engineers (ASME), the highest percentage of welding defect causes are:

Burn-through can result from poor joint fit-up.

Discontinuities are interruptions of the typical structure of a weldment, such as a lack of homogeneity in the mechanical, metallurgical or physical characteristics of the material or weldment that makes the weld rejectable.

When open holes have been completely melted through the base metal, generally caused by too much heat or poor welding motions, it is identified as:

Weld fatigue is related to dynamic weld loads over a period of time.

Welds can fail due to:

If I were welding 0.100 in. thick mild steel, initial amperage setting should be at:

What is a sign of inadequate post flow for the shielding gas?

A/an works like a filter to allow electrons from the desired polarity (electrode positive or electrode negative) to flow through the welding circuit, while blocking the electrons flowing in the opposite direction.

If you were welding thin, dirty aluminum, you should set the wave balance to more: