ITMC Welding Fundamentals 4

Question 1

Which type of crack forms in the heat-affected zone (HAZ) and is associated with hydrogen embrittlement?

Accepted Answer

Cold crack (hydrogen-induced crack)

Answer

Cold cracks, also called hydrogen-induced or delayed cracks, form in the HAZ after the weld has cooled, driven by hydrogen, residual stress, and a susceptible microstructure.

Question 2

What is the recommended tungsten electrode type for welding aluminum with AC GTAW?

Accepted Answer

Pure tungsten or zirconiated tungsten

Answer

Pure tungsten or zirconiated tungsten electrodes form a balled end under AC current, which is ideal for AC GTAW welding of aluminum.

Question 3

A welder is cutting with an oxyfuel torch and the flame is oxidizing. What adjustment should be made to produce a neutral flame?

Accepted Answer

Increase acetylene flow until the feather disappears

Answer

An oxidizing flame has excess oxygen; increasing acetylene flow adds fuel until the inner cone becomes sharp and the excess-acetylene feather disappears, achieving a neutral flame.

Question 4

What does a 'fisheye' discontinuity in a weld cross-section indicate?

Accepted Answer

Hydrogen entrapment causing an internal void with a bright center

Answer

A fisheye is a hydrogen-induced discontinuity visible in a fractured weld surface, appearing as a bright circular area surrounding a void or inclusion.

Question 5

When welding stainless steel, why is it important to control heat input and use backing purge gas?

Accepted Answer

To avoid carbide precipitation and oxidation of the root pass

Answer

Excessive heat causes carbide precipitation (sensitization) at grain boundaries in austenitic stainless steel, and oxygen exposure of the root pass causes sugaring, both of which reduce corrosion resistance.

(ITMC) Industrial Technology Maintenance Certification Practice Test

(ITMC) Industrial Technology Maintenance Certification Practice Test

ITMC Welding Fundamentals 4