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Sequence of tempering and hardening

Aviation Mechanic General (AMG) practice question 26 of 33 on Aircraft Materials, Hardware, and Processes. ACS element AM.I.E.K2 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONIn the heat-treatment of steel, when is the tempering operation performed?

  1. ABefore the hardening operation, to refine the grain
  2. BAfter the hardening operation
  3. CIn place of hardening when brittleness must be avoided
Show the answer and explanation

Correct answer: B. After the hardening operation

  • A — incorrect Tempering never precedes hardening; it is applied to steel that has already been hardened. Grain refinement is a purpose of normalizing.
  • B — correct Tempering always follows, never precedes, hardening. It reduces the brittleness imparted by hardening and softens the steel.
  • C — incorrect Tempering is not a substitute for hardening. It is a separate operation performed on hardened steel to reduce brittleness.

BACKGROUND

Heat-treatment of ferrous metals includes hardening, tempering, normalizing, annealing, and case hardening. Hardening heats the steel above its upper critical point and quenches it rapidly, which increases hardness and strength but leaves the steel brittle and highly stressed. Tempering reheats the hardened steel to a temperature below the low critical point, reducing brittleness and producing definite physical properties. Because of the high internal stresses in the as-quenched condition, the steel must be tempered just before it becomes cold. Tempered steels used in aircraft work have from 125,000 to 200,000 psi ultimate tensile strength.

STUDY TIP

Remember the order as a pair: harden first, temper second. Tempering is the only common steel heat-treatment done below the critical range.

KEY POINTS

  • Tempering always follows hardening; it never precedes it.
  • Tempering reduces brittleness and softens hardened steel.
  • Tempering is done below the low critical point, unlike hardening, normalizing, and annealing.

SOURCES

  • FAA-H-8083-30B ch07 "Tempering"
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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.