When does a structural discontinuity take place?

When does a structural discontinuity take place?

• A. During welding
• B. Before welding
• C. During cooling
• D. After welding

Answer: (A)

A structural discontinuity is created when the weld is being formed. The welding process dumps heat into the metal, melting the filler and base metal, then allows it to solidify. This molten state and rapid cooling can trap gases (porosity), fail to fuse properly with the base metal (lack of fusion), or cause cracks and other defects. These defects interrupt the weld’s uniform structure at the moment of deposition, so they’re formed during welding. If a flaw exists in the base metal before welding, it isn’t a discontinuity created by welding, though it can affect the joint. Issues that occur only during cooling or after welding are consequences of the welding process, but the actual discontinuity is produced as the weld metal is deposited and solidifies.

A structural discontinuity is created when the weld is being formed. The welding process dumps heat into the metal, melting the filler and base metal, then allows it to solidify. This molten state and rapid cooling can trap gases (porosity), fail to fuse properly with the base metal (lack of fusion), or cause cracks and other defects. These defects interrupt the weld’s uniform structure at the moment of deposition, so they’re formed during welding. If a flaw exists in the base metal before welding, it isn’t a discontinuity created by welding, though it can affect the joint. Issues that occur only during cooling or after welding are consequences of the welding process, but the actual discontinuity is produced as the weld metal is deposited and solidifies.