Which electrode type is known for producing hydrogen-rich root passes and requires preheat to avoid cracking?

Which electrode type is known for producing hydrogen-rich root passes and requires preheat to avoid cracking?

• A. E7018
• B. E6010
• C. E316L
• D. E308L

Answer: (B)

Hydrogen cracking is a risk when hydrogen generated in the weld pool gets trapped as the metal cools, especially in the root pass where cooling is fast and restraints are high. An electrode with a cellulose-based coating creates a very hydrogen-rich weld pool, which makes it well known for producing hydrogen-rich root passes. To prevent cracking, preheating the base metal slows the cooling rate and gives hydrogen time to diffuse out of the weld before solidification. That combination—hydrogen-rich root passes and a preheat requirement to avoid cracking—fits the cellulose-based, deep-penetration electrode designed for root passes. The other choices don’t fit this pattern: one is a low-hydrogen, high-quality root-pass electrode used to minimize hydrogen cracking rather than promote it, and the remaining two are stainless-steel electrodes used for different materials and not associated with hydrogen-rich root passes in carbon-steel welding.

Hydrogen cracking is a risk when hydrogen generated in the weld pool gets trapped as the metal cools, especially in the root pass where cooling is fast and restraints are high. An electrode with a cellulose-based coating creates a very hydrogen-rich weld pool, which makes it well known for producing hydrogen-rich root passes. To prevent cracking, preheating the base metal slows the cooling rate and gives hydrogen time to diffuse out of the weld before solidification. That combination—hydrogen-rich root passes and a preheat requirement to avoid cracking—fits the cellulose-based, deep-penetration electrode designed for root passes.

The other choices don’t fit this pattern: one is a low-hydrogen, high-quality root-pass electrode used to minimize hydrogen cracking rather than promote it, and the remaining two are stainless-steel electrodes used for different materials and not associated with hydrogen-rich root passes in carbon-steel welding.