What is the correct arrangement of materials in descending order of machinability _____________________?
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Answer: A. grey cast iron, low carbon steel, wrought iron
Explanation
Grey cast iron exhibits superior machinability due to lubricating graphite flakes that break chips cleanly during cutting operations. Low carbon steel has moderate machinability because its ductility causes continuous, stringy chips that adhere to cutting tools. Wrought iron displays the poorest machinability among the three due to fibrous slag inclusions that resist clean tool shearing. Machinability measures how easily a metallic material can be cut, shaped, and finished by industrial machine tools. The presence of free graphite in grey cast iron acts as a natural chip breaker and solid lubricant during cutting. Wrought iron is nearly pure iron containing embedded fibrous silicate slag, giving it high toughness but poor cutting qualities.
Option B incorrectly places low carbon steel ahead of grey cast iron, ignoring the chip-breaking benefits of graphite. Option C reverses the order entirely, placing the least machinable material first incorrectly. Option D places wrought iron incorrectly at the top despite its fibrous slag making clean machining extremely difficult.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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