Base Metal Preparation Flashcards

When preparing stainless steel for welding, which cleaning agent should be avoided to prevent contamination?

Answer: Chlorinated solvents

Chlorinated solvents can leave residues that cause porosity and stress corrosion cracking in stainless steel welds.

What is the primary purpose of beveling the edges of thick base metal before welding?

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.

Which condition on a base metal surface will most directly cause hydrogen-induced cracking in the weld?

Answer: Moisture or water

Moisture introduces hydrogen into the weld pool, and hydrogen diffusing into the heat-affected zone can cause delayed cracking.

For a butt joint in ¾-inch carbon steel plate, a double-V groove is preferred over a single-V groove primarily because:

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.

A welder notices blue-gray discoloration on the surface of carbon steel plate. This most likely indicates:

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.

When using a grinding wheel to prepare a weld joint, the wheel used on stainless steel should:

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.

What minimum preheat temperature is typically required for high-carbon steel (0.45% C) before welding to prevent cracking?

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.