Why is hydrogen content considered when selecting a filler metal for carbon steel welding?

• A. It has no effect
• B. It can influence hydrogen-induced cracking risk
• C. It changes color
• D. It affects welding speed only

Answer: (B)

Hydrogen content in filler metal matters because hydrogen released during welding can diffuse into the weld metal and the heat-affected zone. Under restraint, this hydrogen can lead to hydrogen-induced cracking as the weld cools and contracts. Using a filler metal with low hydrogen content lowers the amount of hydrogen introduced, reducing the risk of this cracking and improving weld integrity in carbon steels. The other options don’t reflect the real mechanism: hydrogen doesn’t simply change color or affect welding speed, and it does have a significant effect on weld quality through cracking risk.