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 area where filler metal was deposited

Answer

Base metal that was fully melted by the welding arc

Answer

The zone shielded by the welding gas

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

Grain refinement occurs

Answer

No change in grain structure takes place

Answer

Grains become uniformly equiaxed

Question 3

Residual stresses in weldments are primarily caused by:

Accepted Answer

Differential thermal expansion and contraction during welding and cooling

Answer

Improper electrode angle during welding

Answer

Excessive shielding gas flow rate

Answer

Incorrect wire feed speed setting

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

To increase weld deposit hardness

Answer

To add corrosion resistance to the weld surface

Answer

To increase the tensile strength of the weld metal

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

Occurring while the weld pool is still molten

Answer

Appearing immediately as the weld solidifies

Answer

Occurring only during post-weld heat treatment

Question 6

As carbon content and alloying elements increase in steel, the required preheat temperature generally:

Accepted Answer

Increases because the carbon equivalent rises, increasing hardenability and cracking risk

Answer

Decreases because the steel is more heat resistant

Answer

Stays the same regardless of carbon content

Answer

Is eliminated because high-alloy steels do not crack

Question 7

What is the primary risk of allowing interpass temperature to rise excessively above the specified maximum?

Accepted Answer

Degraded mechanical properties due to grain growth and over-tempering

Answer

Increased risk of porosity from trapped gases

Answer

Reduced penetration of subsequent passes

Answer

Increased spatter and arc instability