Unit 16.2: Medium Carbon Steel
Engineering Materials → Engineering Materials → Ferrous Materials → Ferrous Materials → Plain Carbon Steels | Author: admin | Mar 10, 2026
Medium carbon steel is a plain carbon steel with moderate carbon content, providing a balance between strength and ductility.
It is widely used in mechanical engineering for components that require higher strength than low carbon steel but still some ductility.
Definition
Medium Carbon Steel
Medium carbon steel is a plain carbon steel containing 0.25% to 0.60% carbon, with small amounts of manganese and silicon.
Core Concept Explanation
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Increasing carbon content compared to low carbon steel increases tensile strength and hardness, but reduces ductility and toughness.
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Medium carbon steel can be heat treated (quenched and tempered) to improve hardness and strength.
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It is stronger than low carbon steel, but less weldable.
Important Classifications (Carbon Content Range)
| Type | Carbon % | Key Features |
|---|---|---|
| Low Carbon Steel | < 0.25% | Ductile, malleable, easily welded |
| Medium Carbon Steel | 0.25 – 0.60% | Good strength and hardness, moderate ductility |
| High Carbon Steel | 0.60 – 1.5% | Hard, brittle, wear-resistant |
Key Principles / Concepts
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Relationship between Carbon and Mechanical Properties
| Property | Low Carbon | Medium Carbon | High Carbon |
|---|---|---|---|
| Strength | Low | Medium | High |
| Ductility | High | Medium | Low |
| Hardness | Low | Medium | High |
| Toughness | High | Medium | Low |
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Heat Treatment
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Medium carbon steel can be quenched and tempered.
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Quenching → increases hardness and strength
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Tempering → improves toughness and reduces brittleness
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Weldability
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Weldable, but less than low carbon steel due to higher carbon content
Properties / Characteristics
| Property | Description |
|---|---|
| Carbon Content | 0.25 – 0.60% |
| Tensile Strength | 500 – 800 MPa |
| Ductility | Medium |
| Toughness | Medium |
| Hardness | Medium |
| Weldability | Moderate |
| Machinability | Good |
| Heat Treatability | Can be quenched and tempered |
Applications in Engineering
Medium carbon steel is widely used for engineering components requiring higher strength:
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Shafts, axles, and crankshafts
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Gears and pinions
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Railway tracks
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Couplings and fasteners
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Heavy-duty machinery parts
Exam-Focused Points
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Carbon content: 0.25% – 0.60%
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Moderate strength and ductility
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Can be hardened by quenching and tempering
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Used for shafts, gears, rails, and couplings
Common Exam Traps
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Confusing medium carbon steel with low carbon steel (remember: low carbon <0.25%)
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Forgetting that it can be heat treated for hardness
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Misidentifying applications – not used for highly ductile sheets
Example Competitive Exam Questions
Question: What is the carbon content of medium carbon steel?
Answer: 0.25% – 0.60%
Question: Can medium carbon steel be hardened by heat treatment?
Answer: Yes, by quenching and tempering.
Question: Give one typical application of medium carbon steel.
Answer: Shafts and axles.
Question: Compare ductility of low and medium carbon steel.
Answer: Medium carbon steel has lower ductility than low carbon steel.
Quick Revision Summary
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Carbon content: 0.25 – 0.60%
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Strength & hardness: Medium, can be increased by heat treatment
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Ductility & toughness: Medium
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Weldability: Moderate
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Applications: Shafts, gears, railway tracks, couplings