AWS AWS Weld Metallurgy & Heat Treatment 5

Question 1

Which weld zone is defined as the region that reached temperatures above the liquidus but below the solidus during welding?

Accepted Answer

Partially melted zone (PMZ)

Answer

The partially melted zone (PMZ) experienced temperatures between the solidus and liquidus, resulting in partial melting at grain boundaries.

Question 2

What type of transformation occurs in plain carbon steel when rapidly cooled from the austenite region?

Accepted Answer

Martensitic transformation

Answer

Rapid cooling (quenching) of austenite in plain carbon steel produces martensite, a hard and brittle body-centered tetragonal (BCT) structure.

Question 3

What is the role of interpass temperature control in multi-pass welding of low-alloy steels?

Accepted Answer

Maintains heat input within acceptable limits to control microstructure and avoid excessive softening or cracking

Answer

Controlling interpass temperature prevents excessive cumulative heat input, which could cause grain coarsening, loss of toughness, or reheat cracking in certain steels.

Question 4

Sigma phase formation in stainless steel welds is most problematic because it:

Accepted Answer

Reduces toughness and corrosion resistance, especially at elevated temperatures

Answer

Sigma phase is a hard, brittle intermetallic compound that forms in duplex and ferritic stainless steels, severely reducing impact toughness and corrosion resistance.

Question 5

In welding carbon steel, what is the purpose of a stress relief heat treatment performed below the lower critical temperature (Ac1)?

Accepted Answer

To reduce residual welding stresses without significantly altering the existing microstructure

Answer

Stress relief at sub-critical temperatures reduces residual stresses through plastic flow without causing phase transformation, preserving the existing microstructure.

AWS Practice Test

AWS Practice Test

AWS AWS Weld Metallurgy & Heat Treatment 5