Low manganese steel
Carbon Tool Steel is a type of tool steel with carbon as the main alloying element and no or only trace amounts of other alloying elements. It typically has high hardness, good wear resistance, and machinability, mainly used for manufacturing cutting tools, molds, measuring instruments, etc.
🔩 Key Characteristics of Carbon Tool Steel:
|
Characteristic |
Description |
|
High Hardness |
Can reach above HRC 60 after quenching |
|
Good Wear Resistance |
Suitable for cutting tools and molds |
|
Medium Machinability |
Machinability is acceptable before quenching but has high risk of distortion after heat treatment |
|
Poor Heat Resistance |
Hardness rapidly decreases at high temperatures (<200°C) |
|
Low Cost |
Lower raw material cost but shorter lifespan than alloy tool steels |
🔠 Classification according to JIS (Japanese Industrial Standards):
JIS G4401 designates carbon tool steel with the code SKx (Steel for tools, carbon)
📘 Common JIS G4401 grades (SK series):
|
Grade |
Carbon Content (%) |
Characteristics and Uses |
|
SK1 |
1.00 ~ 1.10 |
Ultra-high hardness, excellent wear resistance, used for blades, files, etc. |
|
SK2 |
0.95 ~ 1.04 |
Similar to SK1, slightly lower hardness but better machinability |
|
SK3 |
0.90 ~ 1.00 |
Common high carbon tool steel, used for saw blades, scissors |
|
SK4 |
0.85 ~ 0.94 |
Commonly used for hand tools and simple molds |
|
SK5 |
0.80 ~ 0.89 |
Balances strength and machinability, used for springs, steel rulers, scrapers, etc. |
|
SK6 |
0.75 ~ 0.84 |
Medium carbon content, slightly lower hardness, commonly used for general cutting tools |
|
SK7 |
0.70 ~ 0.79 |
Lowest carbon content, suitable for tools requiring high toughness |
📏 Chemical composition range (example: SK3):
|
Element |
Content (%) |
|
C (Carbon) |
0.90 ~ 1.00 |
|
Si (Silicon) |
≤ 0.35 |
|
Mn (Manganese) |
≤ 0.50 |
|
P (Phosphorus) |
≤ 0.030 |
|
S (Sulfur) |
≤ 0.030 |
Higher carbon content → higher hardness and wear resistance but lower toughness and machinability.
🛠 Typical Application Areas:
- Hand tools (saw blades, files, planes)
- Molds (simple cold-working molds)
- Measuring tools (steel rulers)
- Spring clips (especially SK5)
- Scissors, scrapers, carving knives
🔥 Heat Treatment Characteristics (example: SK3/SK5):
- Quenching temperature: 760°C ~ 800°C
- Tempering temperature: 150°C ~ 200°C (low temperature tempering maintains high hardness)
- Hardness (after quenching): HRC 60 ~ 66
⚠️ Notes:
- High hardness → brittle, not suitable for impact loads
- Prone to distortion → heat treatment must be carefully controlled
If higher toughness and heat resistance are required → consider alloy tool steels (e.g. SKS3, SKD11)