Weld Defects & Quality Assessment
Porosity, undercut, incomplete fusion, overlap, crater cracks, solidification cracking, lamellar tearing, and HAZ characteristics.
- Identify the causes and characteristics of porosity in welds
- Explain undercut, incomplete fusion, and overlap defects
- Describe crater cracks, solidification cracking, and lamellar tearing
- Define the heat affected zone and its significance
- Recognize radiographic indications of weld defects
Lección 1
Porosity, Gas Entrapment & Slag Inclusions
What Causes Porosity?
Porosity in welds is caused by gas trapped in the weld pool. As the molten metal solidifies, dissolved gases form bubbles that become locked in the weld metal. Common sources of gas contamination include moisture on the base metal, contaminated filler metal, inadequate shielding gas coverage, and organic materials such as oil or paint on the joint surfaces.
Types of Porosity
Porosity appears in several forms. Scattered porosity consists of random small pores distributed throughout the weld. Linear porosity follows a line along the weld axis, often indicating a consistent source of contamination. Cluster porosity appears as a group of pores in a localized area, typically caused by a momentary loss of shielding gas or a contamination source at a specific location.
Exam Tip
When the exam asks what causes porosity, the answer is always about gas trapped in the weld pool - not excessive travel speed, incorrect electrode angle, or high amperage.
Porosity is caused by gas trapped in the weld pool during solidification. Preventing porosity requires clean base metal, dry electrodes, and adequate shielding gas coverage.