Certified Welder Base Metal Preparation 2 — Questions and Answers
Question 1: When preparing stainless steel for welding, which cleaning agent should be avoided to prevent contamination?
- Acetone
- Chlorinated solvents (Correct answer)
- Isopropyl alcohol
- Mild detergent
Correct answer: Chlorinated solvents
Chlorinated solvents can leave residues that cause porosity and stress corrosion cracking in stainless steel welds.
Question 2: What is the primary purpose of beveling the edges of thick base metal before welding?
- To reduce distortion
- To ensure full penetration and fusion (Correct answer)
- To speed up the welding process
- To improve surface appearance
Correct answer: To ensure full penetration and fusion
Beveling creates a groove joint geometry that allows the weld to achieve full fusion and penetration through the entire joint thickness.
Question 3: Which condition on a base metal surface will most directly cause hydrogen-induced cracking in the weld?
- Light surface rust
- Mill scale
- Moisture or water (Correct answer)
- Paint overspray
Correct answer: Moisture or water
Moisture introduces hydrogen into the weld pool, and hydrogen diffusing into the heat-affected zone can cause delayed cracking.
Question 4: For a butt joint in ¾-inch carbon steel plate, a double-V groove is preferred over a single-V groove primarily because:
- It is faster to cut
- It reduces total weld metal required and distortion (Correct answer)
- It eliminates the need for back gouging
- It allows higher travel speed
Correct answer: It reduces total weld metal required and distortion
A double-V groove requires less filler metal than a single-V and distributes weld shrinkage on both sides, reducing angular distortion.
Question 5: A welder notices blue-gray discoloration on the surface of carbon steel plate. This most likely indicates:
- Oil contamination
- High carbon content
- Heat tinting from prior thermal cutting (Correct answer)
- Galvanized coating
Correct answer: Heat tinting from prior thermal cutting
Blue-gray oxidation is characteristic of heat tinting that occurs when steel is exposed to elevated temperatures during flame or plasma cutting.
Question 6: When using a grinding wheel to prepare a weld joint, the wheel used on stainless steel should:
- Be the same wheel used on carbon steel
- Be dedicated to stainless steel only (Correct answer)
- Contain iron-based abrasives
- Be run at the highest possible RPM
Correct answer: Be dedicated to stainless steel only
A grinding wheel previously used on carbon steel can embed iron particles into stainless steel, causing rust and potential corrosion in the weld area.
Question 7: What minimum preheat temperature is typically required for high-carbon steel (0.45% C) before welding to prevent cracking?
- No preheat required
- 100°F (38°C)
- 300–400°F (149–204°C) (Correct answer)
- 600°F (316°C)
Correct answer: 300–400°F (149–204°C)
High-carbon steels are susceptible to hydrogen cracking; a preheat of 300–400°F slows cooling and allows hydrogen to diffuse out of the HAZ.
Certified Welder Base Metal Preparation 2
When preparing stainless steel for welding, which cleaning agent should be avoided to prevent contamination?