Certified Welder Heat Input and Distortion Control 3

Question 1

The heat affected zone (HAZ) in a weldment is best described as:

Accepted Answer

Base metal that was not melted but had its microstructure altered by welding heat

Answer

The HAZ is the portion of the base metal that was never melted but experienced temperatures high enough to alter its microstructure and mechanical properties.

Question 2

In the HAZ region immediately adjacent to the fusion line, what typically happens to grain structure?

Accepted Answer

Grain coarsening occurs due to exposure to very high temperatures

Answer

The coarse-grain HAZ region closest to the fusion line reaches near-melting temperatures, promoting significant grain growth that can reduce impact toughness.

Question 3

Residual stresses in weldments are primarily caused by:

Accepted Answer

Differential thermal expansion and contraction during welding and cooling

Answer

Residual stresses are locked in because different regions of the weld and HAZ heat and cool at different rates, causing non-uniform plastic deformation that remains after cooling.

Question 4

What is the primary purpose of post-weld heat treatment (PWHT)?

Accepted Answer

To relieve residual stresses and improve toughness in the HAZ

Answer

PWHT reduces residual stresses and HAZ hardness while improving toughness, making it essential for pressure vessels, high-strength steels, and code-required applications.

Question 5

Cold cracking (hydrogen-induced cracking) in steel weldments is characterized by:

Accepted Answer

Potentially occurring hours or days after welding as hydrogen migrates to stress points

Answer

Hydrogen-induced cracking is delayed because it requires time for diffusible hydrogen to migrate to stress concentration areas; cracking may not appear until hours or days after welding.

Certified Welder Practice Test

Certified Welder Practice Test

Certified Welder Heat Input and Distortion Control 3