SkyDrill

Heat-treatment after welding steel

Aviation Mechanic General (AMG) practice question 18 of 33 on Aircraft Materials, Hardware, and Processes. ACS element AM.I.E.K14 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONAfter a steel part has been fabricated or repaired by welding, which heat-treatment should be applied to relieve the internal stresses and refine the grain?

  1. ACase hardening
  2. BTempering below the low critical point
  3. CNormalizing
Show the answer and explanation

Correct answer: C. Normalizing

  • A — incorrect Case hardening produces a hard, wear-resistant surface over a tough core; it does not address the strains and cast structure produced by welding.
  • B — incorrect Tempering reduces the brittleness of hardened steel. Normalizing, done above the upper critical point with air cooling, is the treatment for welded parts.
  • C — correct All welded parts should be normalized after fabrication to refine the grain and relieve the internal stresses set up by welding.

BACKGROUND

Normalizing removes the internal stresses set up by heat-treating, welding, casting, forming, or machining. One of its most important uses in aircraft work is in welded parts: welding sets up strains in the adjacent material, and the weld itself is a cast structure as opposed to the wrought structure of the rest of the material. These two structures have different grain sizes, so to refine the grain and relieve internal stresses, all welded parts should be normalized after fabrication. Normalizing is accomplished by heating the steel above the upper critical point and cooling it in still air, which yields a harder and stronger material than annealing.

STUDY TIP

Whenever a question pairs welding with a follow-up heat-treatment, the answer is normalizing.

KEY POINTS

  • Welding leaves internal strains and a cast-structure weld with a different grain size.
  • All welded parts should be normalized after fabrication.
  • Normalizing heats above the upper critical point and cools in still air.

SOURCES

  • FAA-H-8083-30B ch07 "Normalizing"
Practice the Aviation Mechanic General (AMG) test →Timed 60-question exam, by ACS area, or review your misses. Free.
MORE ON AIRCRAFT MATERIALS, HARDWARE, AND PROCESSES

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.