Overview
O1 Tool Steel is an oil-hardening cold-work tool steel known for its excellent machinability, dimensional stability, toughness, wear resistance, and reliable heat treatment response.
O1 is widely used in:
- Cutting Tools
- Punches & Dies
- Gauges
- Fixtures
- Machine Knives
- Forming Tools
- Precision Tooling
- Wear Components
Compared with A2, O1 is easier to machine but has slightly higher heat-treatment distortion. Compared with D2, O1 offers better toughness and machinability but lower wear resistance.
Material Specification
| Property | Value |
|---|---|
| Material Designation | O1 Tool Steel |
| Standard | ASTM A681 |
| UNS Number | T31501 |
| Material Family | Oil-Hardening Cold Work Tool Steel |
| Density | 7.85 g/cm³ |
| Magnetic Property | Magnetic |
| Typical Supply Condition | Annealed |
| Standard Forms | Round Bar, Flat Bar, Plate, Block, Tooling Stock |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Carbon (C) | 0.85–1.00 |
| Manganese (Mn) | 1.00–1.40 |
| Chromium (Cr) | 0.40–0.60 |
| Tungsten (W) | 0.40–0.60 |
| Vanadium (V) | 0.15–0.30 |
| Silicon (Si) | ≤0.50 |
| Phosphorus (P) | ≤0.030 |
| Sulfur (S) | ≤0.030 |
Mechanical Properties
Annealed Condition
| Property | Value |
|---|---|
| Tensile Strength | 700–900 MPa |
| Yield Strength | 450–650 MPa |
| Hardness | 190–230 HB |
| Elastic Modulus | 210 GPa |
Hardened & Tempered Condition
| Property | Value |
|---|---|
| Hardness | 57–62 HRC |
| Wear Resistance | Good |
| Toughness | Good |
| Dimensional Stability | Good |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1420–1460°C |
| Thermal Conductivity | 31 W/m·K |
| Electrical Resistivity | 0.55 μΩ·m |
| Thermal Expansion Coefficient | 11.0 × 10⁻⁶/K |
| Specific Heat Capacity | 460 J/kg·K |
Corrosion Resistance
| Environment | Performance |
|---|---|
| Indoor Environment | Moderate |
| Dry Atmosphere | Good |
| Humid Environment | Poor |
| Outdoor Environment | Poor |
| Marine Environment | Very Poor |
| Chemical Environment | Poor |
O1 is not corrosion resistant and should be protected with coatings or oiling.
Recommended surface treatments:
- Black Oxide
- Oil Coating
- Phosphate Coating
- TiN Coating
- DLC Coating
- Hard Chrome Plating
Weldability
| Welding Process | Rating |
|---|---|
| TIG Welding | Poor |
| MIG Welding | Poor |
| Arc Welding | Poor |
| Laser Repair Welding | Fair |
| Tool Steel Repair Welding | Fair |
Welding O1 requires preheating, controlled cooling, and post-weld tempering.
Machinability
| Process | Rating |
|---|---|
| CNC Turning | Excellent |
| CNC Milling | Excellent |
| Drilling | Excellent |
| Grinding | Excellent |
| EDM Machining | Good |
| Wire EDM | Good |
O1 is one of the easiest tool steels to machine in the annealed condition.
Heat Treatment
Annealing
| Parameter | Value |
|---|---|
| Temperature | 760–790°C |
| Cooling Method | Furnace Cool |
Hardening
| Parameter | Value |
|---|---|
| Temperature | 780–820°C |
| Cooling Medium | Oil |
Tempering
| Parameter | Value |
|---|---|
| Temperature | 150–300°C |
| Cycles | Double Temper Recommended |
Hardness After Heat Treatment
| Condition | Hardness |
|---|---|
| Annealed | 190–230 HB |
| Hardened | 62–65 HRC |
| Hardened & Tempered | 57–62 HRC |
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| ASTM / AISI | O1 |
| UNS | T31501 |
| GB/T (China) | 9CrWMn |
| EN (Europe) | 90MnCrV8 |
| DIN (Germany) | 1.2510 |
| JIS (Japan) | SKS3 |
| ISO | 90MnCrV8 |
Available Forms
| Product Type | Availability |
|---|---|
| Round Bar | Yes |
| Flat Bar | Yes |
| Tool Steel Plate | Yes |
| Precision Ground Plate | Yes |
| Drill Rod | Yes |
| Mold Blocks | Yes |
| Tooling Stock | Yes |
Typical Applications
Tool & Die Industry
- Punches
- Dies
- Blanking Tools
- Forming Tools
Cutting Tool Industry
- Machine Knives
- Shear Blades
- Cutting Dies
- Slitting Tools
Precision Manufacturing
- Gauges
- Fixtures
- Measuring Tools
- Precision Tooling
Mold Industry
- Mold Inserts
- Core Pins
- Small Mold Components
Industrial Machinery
- Wear Plates
- Guide Components
- Wear-Resistant Parts
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Machining | Outstanding |
| Precision Grinding | Outstanding |
| Heat Treatment | Excellent |
| EDM Machining | Good |
| Wire EDM | Good |
| Black Oxide | Excellent |
| Tool Grinding | Outstanding |
Advantages
Excellent Machinability
Easier to machine than many cold-work tool steels.
Good Toughness
Performs well in moderate-impact applications.
Good Wear Resistance
Suitable for many cutting and forming tools.
Reliable Heat Treatment
Easy to harden using oil quenching.
Cost Effective
Lower cost than many air-hardening tool steels.
Good Edge Retention
Suitable for knives, punches, and cutting tools.
Limitations
Higher Heat Treatment Distortion Than A2
Oil quenching can create more dimensional change.
Lower Wear Resistance Than D2
Not ideal for severe abrasion applications.
Poor Corrosion Resistance
Requires protection in humid environments.
Limited High-Temperature Performance
Not suitable for hot-work tooling.
Comparison with Other Tool Steels
| Property | O1 | A2 | D2 | D3 | W1 |
|---|---|---|---|---|---|
| Machinability | Excellent | Good | Fair | Fair | Excellent |
| Wear Resistance | Good | Excellent | Outstanding | Exceptional | Moderate |
| Toughness | Good | Excellent | Moderate | Lower | Good |
| Dimensional Stability | Good | Outstanding | Excellent | Excellent | Poor |
| Hardness | 62 HRC | 62 HRC | 62 HRC | 64 HRC | 65 HRC |
Comparison with Engineering Materials
| Material | Hardness Potential | Wear Resistance | Toughness |
|---|---|---|---|
| O1 Tool Steel | 62 HRC | Good | Good |
| A2 Tool Steel | 62 HRC | Excellent | Excellent |
| D2 Tool Steel | 62 HRC | Outstanding | Moderate |
| D3 Tool Steel | 64 HRC | Exceptional | Lower |
| 4140 Steel | 58 HRC | Good | Excellent |
| W1 Tool Steel | 65 HRC | Moderate | Good |
Available Surface Finishes
Raw Finishes
- Annealed Finish
- Ground Finish
- Precision Machined Finish
Functional Finishes
- Hardened Finish
- Precision Ground Finish
- EDM Finish
- Tool Ground Finish
Protective Finishes
- Black Oxide
- Oil Coating
- Phosphate Coating
- TiN Coating
- DLC Coating
- Hard Chrome Plating
Frequently Asked Questions (FAQ)
What is O1 tool steel?
O1 is an oil-hardening cold-work tool steel known for excellent machinability, good toughness, and reliable heat treatment performance.
What is O1 steel used for?
Typical applications include:
- Punches
- Dies
- Gauges
- Fixtures
- Machine Knives
- Precision Tools
What is the equivalent material to O1?
Common equivalents include:
- 9CrWMn
- 1.2510
- SKS3
- 90MnCrV8
What is the difference between O1 and A2?
| Property | O1 | A2 |
|---|---|---|
| Hardening Method | Oil Hardening | Air Hardening |
| Machinability | Better | Good |
| Dimensional Stability | Lower | Better |
| Toughness | Good | Better |
What is the difference between O1 and D2?
| Property | O1 | D2 |
|---|---|---|
| Wear Resistance | Lower | Higher |
| Toughness | Better | Lower |
| Machinability | Better | Lower |
| Cost | Lower | Higher |
What hardness can O1 achieve?
O1 can typically reach 57–62 HRC after hardening and tempering.
Is O1 suitable for knives?
Yes. O1 is commonly used for knives and blades because of its good edge retention and ease of sharpening.
Can O1 be welded?
Welding is difficult and generally not recommended unless proper tool-steel welding procedures are used.
Why is O1 widely used in toolmaking?
Because it combines:
- Excellent Machinability
- Good Wear Resistance
- Good Toughness
- Reliable Heat Treatment
- Cost Efficiency
Does GCNOV provide custom manufacturing services for O1 steel?
Yes. GCNOV provides:
- CNC Machining
- Tool & Die Manufacturing
- Wire EDM
- Precision Grinding
- Heat Treatment
- Black Oxide Finishing
- Surface Coating
- Prototype Development
- Low-Volume Production
- Mass Production