Addition of ______________ to steel compositions assists in increasing hardenability depth?
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Answer: A. Chromium
Explanation
Chromium decreases the critical cooling rate required to form martensite during quenching. This alteration in transformation kinetics allows thicker steel sections to harden throughout. Adding chromium directly enhances the depth of hardenability in alloy steel components. Hardenability refers to the ability of a steel alloy to be hardened by forming martensite in depth. Alloy elements dissolved in austenite delay the formation of softer pearlite or bainite phases. Jominy end-quench tests are standard laboratory procedures used to measure steel hardenability.
Large automotive gears and shafts require deep hardenability to ensure uniform strength profiles. Heat treaters select chromium-alloyed steels to achieve thorough hardening in heavy cross-sections. Consistent microstructural hardness prevents premature wear and fatigue failure in service. Sulphur is added to improve machinability by forming inclusions that break up chips easily. Vanadium is primarily used to refine grain size and form stable wear-resisting carbide precipitates. Tungsten forms hard carbides for high-speed cutting tools rather than acting as the primary hardenability agent.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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