Tempering steel after quenching primarily achieves which outcome?

• A. Tempering after quenching reduces brittleness and adjusts hardness.
• B. Annealing softens steel and relieves stresses, improving ductility.
• C. Tempering permanently hardens steel to its maximum hardness.
• D. Annealing increases strength and decreases ductility.

Answer: (A)

Tempering after quenching is about tuning the balance between hardness and toughness. When steel is quenched it becomes martensite, a very hard but brittle structure with lots of internal stresses. Tempering heats the steel to a lower temperature and then cools it slowly enough to let carbon atoms rearrange a bit and form fine carbides, while relieving those stresses. This changes the microstructure to tempered martensite, which stays hard enough for wear resistance but becomes much tougher and less prone to cracking under impact.

That’s why the primary outcome is reduced brittleness and an adjusted hardness to a more useful level. It’s not the same as annealing, which softens steel more broadly and relieves stresses for maximum ductility. It also doesn’t aim to push steel to maximum hardness, and tempering typically reduces some hardness while boosting toughness, rather than strictly increasing strength at the expense of ductility.