Certified Welder Base and Filler Metals 2 — Questions and Answers
Question 1: Which AWS filler metal classification designates an electrode suitable for welding low-alloy, high-strength steel?
- E6013
- E7018 (Correct answer)
- E7024
- E6010
Correct answer: E7018
E7018 is a low-hydrogen electrode designed for high-strength, low-alloy steels requiring good toughness.
Question 2: What does the 'R' designation indicate in an ER70S-6 filler wire classification?
- Rod only
- Rod or electrode (Correct answer)
- Reverse polarity required
- Resistant to oxidation
Correct answer: Rod or electrode
The 'R' in ER70S-6 indicates the wire can be used as either a rod or an electrode.
Question 3: A base metal with a carbon equivalent (CE) above 0.45% typically requires which precaution?
- Post-weld annealing
- Preheat before welding (Correct answer)
- Use of flux-cored wire only
- Lower amperage settings
Correct answer: Preheat before welding
High carbon equivalent increases hardenability and crack risk, so preheating is required to slow the cooling rate.
Question 4: Which stainless steel series is considered non-hardenable by heat treatment?
- Martensitic (400 series)
- Austenitic (300 series) (Correct answer)
- Precipitation-hardening grades
- Duplex grades
Correct answer: Austenitic (300 series)
Austenitic stainless steels cannot be hardened by heat treatment because they remain face-centered cubic at all temperatures.
Question 5: When welding dissimilar metals such as carbon steel to stainless steel, which filler metal is most commonly recommended?
- ER308L
- ER70S-6
- E309L (Correct answer)
- E316L
Correct answer: E309L
E309L is formulated for joining dissimilar metals, especially carbon steel to stainless steel, due to its high alloy content.
Question 6: The mill scale on carbon steel base metal can cause which welding problem?
- Excessive penetration
- Porosity and incomplete fusion (Correct answer)
- Hot cracking in the HAZ
- Underbead cracking
Correct answer: Porosity and incomplete fusion
Mill scale traps gases and impedes fusion, leading to porosity and lack-of-fusion defects.
Question 7: What property of aluminum makes it challenging to weld compared to carbon steel?
- Higher melting point
- Tenacious oxide layer with a much higher melting point than the base metal (Correct answer)
- Tendency to form carbides
- Low thermal conductivity
Correct answer: Tenacious oxide layer with a much higher melting point than the base metal
Aluminum oxide melts at ~2050°C while aluminum itself melts at ~660°C, so the oxide must be removed before the base metal can fuse.
Certified Welder Base and Filler Metals 2
Which AWS filler metal classification designates an electrode suitable for welding low-alloy, high-strength steel?