AWS Certified Welding Inspector — FundamentalsWelding ProcessesHard
A CWI is evaluating a Weld Procedure Specification (WPS) for the repair of heavy machinery components using Shielded Metal Arc Welding (SMAW). The base material is a low-alloy steel that is susceptible to hydrogen-induced cracking. The WPS specifies an E7018 electrode. What is the most critical pre-welding requirement for this electrode to prevent hydrogen-induced cracking?
- AUsing a high travel speed to minimize heat input.
- BBaking the electrodes at 700°F (371°C) for 1 hour and storing in a heated oven.
- CMaintaining a long arc length.
- DPreheating the base metal to 200°F (93°C).
Show answer & explanationAnswer & explanation
Correct answer: B. Baking the electrodes at 700°F (371°C) for 1 hour and storing in a heated oven.
E7018 electrodes are low-hydrogen electrodes, meaning they have a coating designed to minimize moisture absorption. To ensure their low-hydrogen properties are maintained, they must be properly baked (reconditioned) at specified temperatures and then stored in a heated holding oven. This prevents moisture pickup which is a primary source of diffusible hydrogen leading to cracking.
Why the other options are wrong
- A. Using a high travel speed would increase the cooling rate, which can actually exacerbate hydrogen-induced cracking in susceptible steels, opposite to the desired effect.
- C. Maintaining a long arc length would actually increase the risk of hydrogen pickup and atmospheric contamination, directly contradicting the purpose of E7018.
- D. Preheating is important for low-alloy steels to slow the cooling rate and allow hydrogen to diffuse out, but it's a separate measure from ensuring the electrode itself is low-hydrogen. The question asks about the *electrode* requirement.
E7018 Electrode Handling
E7018 are low-hydrogen SMAW electrodes requiring specific handling, baking, and storage procedures to maintain their moisture resistance and prevent hydrogen-induced cracking.
- Must be kept dry.
- Requires reconditioning (baking) if exposed to atmosphere.
- Stored in heated holding ovens (rod ovens).
Memory trick: Keep E7018 dry, or cracks will cry.