Quick revision for PSC: soaking time, tempering, case hardening stages, carburizing, nitriding and induction hardening.
Quick Notes
Use these before attempting the MCQs.
Soaking time
Low alloy steels: ~5 minutes per 10 mm thickness (general guide).
Tempering
Relieves stress, reduces brittleness, and balances hardness & toughness.
Case hardening
Two stages: carburizing + heat treatment (core refined, case hardened).
Nitriding
Gas nitriding uses ammonia at about 500°C; nitrogen diffuses into the surface.
MCQs
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1) Recommended soaking time for hardening for low alloy steel?
2) Primary purpose of tempering in heat-treatment process?
3) Up to what percentage is carbon content increased in surface layer during case hardening?
4) Two stages of case hardening?
5) Primary purpose of energizer in pack carburizing?
6) Which method produces an abrupt change in carbon content (may cause flaking)?
Note: Option B and D are the same idea in many texts (liquid/salt-bath).
7) Why is the core refined after carburizing (case hardening)?
8) Temperature to reheat the core to refine it (case hardening)?
9) Temperature during gas nitriding process?
10) Purpose of circulating ammonia gas during gas nitriding?
11) Thickness formed during salt bath nitriding (nitrogen + carbon layer)?
12) In induction hardening, depth of hardening for high-frequency current?
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