Which statement about tempering steel after hardening is true?

• A. To increase hardness
• B. To relieve internal stresses and reduce brittleness
• C. To improve electrical conductivity
• D. To reduce weight

Answer: (B)

Tempering after hardening is done to relieve internal stresses and reduce brittleness. Quenching hardens steel by forming martensite, but that process traps stress and makes the metal very brittle. Heating to a lower temperature allows the structure to relax, increases toughness, and makes the steel less prone to cracking, even though some hardness is reduced. Electrical conductivity and weight aren’t the goals of tempering, and increasing hardness is typically the result of hardening, not tempering. So the statement about tempering’s purpose being to relieve internal stresses and reduce brittleness is the correct one.