Overview
O2 Tool Steel is a high-carbon, manganese-alloyed oil-hardening cold-work tool steel known for its excellent wear resistance, dimensional stability, edge retention, and machinability. Compared with O1 tool steel, O2 offers higher wear resistance and hardness due to its increased manganese content, while maintaining relatively simple heat treatment characteristics.
O2 is widely used in:
- Precision Punches
- Blanking Dies
- Machine Knives
- Shear Blades
- Measuring Tools
- Woodworking Tools
- Forming Tools
- Wear Components
Because of its combination of high hardness, good wear resistance, and cost-effectiveness, O2 remains a popular tool steel for medium-duty tooling applications.
Material Specification
| Property | Value |
|---|---|
| Material Designation | O2 Tool Steel |
| Standard | ASTM A681 |
| UNS Number | T31502 |
| 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, Tooling Stock |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Carbon (C) | 0.85–0.95 |
| Manganese (Mn) | 1.60–2.00 |
| Silicon (Si) | 0.10–0.40 |
| Chromium (Cr) | ≤0.30 |
| Tungsten (W) | ≤0.30 |
| Vanadium (V) | Trace |
| Phosphorus (P) | ≤0.030 |
| Sulfur (S) | ≤0.030 |
The elevated manganese content improves hardenability and wear resistance compared with O1.
Mechanical Properties
Annealed Condition
| Property | Value |
|---|---|
| Tensile Strength | 700–900 MPa |
| Yield Strength | 450–650 MPa |
| Hardness | 190–240 HB |
| Elastic Modulus | 210 GPa |
Hardened & Tempered Condition
| Property | Value |
|---|---|
| Hardness | 58–64 HRC |
| Wear Resistance | Very Good |
| Toughness | Good |
| Edge Retention | Excellent |
Precision Tooling Condition
| Property | Value |
|---|---|
| Hardness | 60–64 HRC |
| Service Life | Excellent |
| Dimensional Stability | Good |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1410–1460°C |
| Thermal Conductivity | 29 W/m·K |
| Electrical Resistivity | 0.58 μΩ·m |
| Thermal Expansion Coefficient | 11.1 × 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 |
O2 is not corrosion resistant and should be protected during storage and service.
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 |
Due to its high carbon content, O2 is difficult to weld and requires specialized procedures.
Recommended:
- Preheating
- Controlled Cooling
- Post-Weld Tempering
Machinability
| Process | Rating |
|---|---|
| CNC Turning | Excellent |
| CNC Milling | Excellent |
| Drilling | Excellent |
| Grinding | Excellent |
| EDM Machining | Good |
| Wire EDM | Good |
Machinability Comparison
| Material | Machinability |
|---|---|
| O1 Tool Steel | Excellent |
| O2 Tool Steel | Excellent |
| A2 Tool Steel | Good |
| D2 Tool Steel | Fair |
| D3 Tool Steel | Fair |
O2 machines very well in the annealed condition and is suitable for precision tooling production.
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 | 190–240 HB |
| Hardened | 62–65 HRC |
| Hardened & Tempered | 58–64 HRC |
Surface Hardening
| Process | Result |
|---|---|
| Nitriding | 65–70 HRC |
| PVD Coating | Improved Wear Resistance |
| DLC Coating | Reduced Friction |
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| ASTM / AISI (USA) | O2 |
| UNS | T31502 |
| GB/T (China) | Similar to 9Mn2V |
| EN (Europe) | 90MnV8 (Closest Equivalent) |
| DIN (Germany) | 1.2842 |
| JIS (Japan) | Equivalent Grade Available by Application |
| ISO | 90MnV8 |
Note: O2 has fewer global equivalents than O1 and is less commonly used internationally.
Available Forms
| Product Type | Availability |
|---|---|
| Round Bar | Yes |
| Flat Bar | Yes |
| Tool Steel Plate | Yes |
| Precision Ground Plate | Yes |
| Tooling Stock | Yes |
| Mold Blocks | Limited |
Typical Applications
Tool & Die Industry
- Blanking Dies
- Punches
- Forming Dies
- Trimming Tools
Cutting Tool Industry
- Machine Knives
- Shear Blades
- Slitting Tools
- Cutting Dies
Precision Manufacturing
- Gauges
- Fixtures
- Measuring Instruments
- Alignment Tools
Woodworking Industry
- Wood Cutting Knives
- Planer Blades
- Specialty Cutting Tools
General Engineering
- Wear Parts
- Tool Holders
- Precision Mechanical Components
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Machining | Outstanding |
| Precision Grinding | Outstanding |
| Heat Treatment | Excellent |
| EDM Machining | Good |
| Wire EDM | Good |
| Black Oxide Finishing | Excellent |
| Tool Grinding | Outstanding |
Advantages
Excellent Machinability
Easy to machine before heat treatment.
High Hardness
Capable of achieving up to 64 HRC.
Good Wear Resistance
Suitable for most cold-work tooling applications.
Good Edge Retention
Ideal for cutting and trimming tools.
Simple Heat Treatment
Reliable oil-hardening process.
Cost Effective
More economical than many high-alloy tool steels.
Limitations
Lower Toughness Than A2
Less suitable for heavy-impact tooling.
Higher Distortion Than Air-Hardening Steels
Oil quenching may increase dimensional change.
Limited Corrosion Resistance
Requires protective coatings.
Lower Wear Resistance Than D2 or D3
Not ideal for extreme abrasion applications.
Comparison with Other Tool Steels
| Property | O2 | O1 | A2 | D2 | D3 |
|---|---|---|---|---|---|
| Hardness | 64 HRC | 62 HRC | 62 HRC | 62 HRC | 64 HRC |
| Wear Resistance | Very Good | Good | Excellent | Outstanding | Exceptional |
| Toughness | Good | Good | Excellent | Moderate | Lower |
| Machinability | Excellent | Excellent | Good | Fair | Fair |
| Heat Treatment Distortion | Moderate | Moderate | Low | Low | Low |
Comparison with Engineering Materials
| Material | Hardness Potential | Wear Resistance | Toughness |
|---|---|---|---|
| O2 Tool Steel | 64 HRC | Very Good | Good |
| 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 |
Available Surface Finishes
Raw Finishes
- Annealed Finish
- Ground Finish
- Precision Machined Finish
Functional Finishes
- Hardened Finish
- Precision Ground Finish
- Tool Ground Finish
- EDM Finish
Protective Finishes
- Black Oxide
- Oil Coating
- Phosphate Coating
- TiN Coating
- DLC Coating
- Hard Chrome Plating
Frequently Asked Questions (FAQ)
What is O2 tool steel?
O2 is an oil-hardening cold-work tool steel that provides high hardness, good wear resistance, excellent machinability, and reliable heat treatment performance.
What is O2 steel used for?
Typical applications include:
- Punches
- Dies
- Machine Knives
- Gauges
- Fixtures
- Cutting Tools
What is the equivalent material to O2?
Common equivalents include:
- DIN 1.2842
- 90MnV8
- Similar to 9Mn2V (China)
What is the difference between O2 and O1?
| Property | O2 | O1 |
|---|---|---|
| Manganese Content | Higher | Lower |
| Wear Resistance | Better | Good |
| Toughness | Similar | Similar |
| Hardness | Slightly Higher | High |
What hardness can O2 achieve?
O2 typically achieves:
- Hardened: 62–65 HRC
- Hardened & Tempered: 58–64 HRC
Is O2 suitable for knives?
Yes. O2 offers good edge retention and wear resistance for industrial knives and cutting tools.
Can O2 be welded?
Welding is generally not recommended without specialized tool-steel welding procedures.
Why is O2 used for tooling?
Because it combines:
- High Hardness
- Good Wear Resistance
- Excellent Machinability
- Cost Efficiency
- Reliable Heat Treatment
Is O2 better than O1?
For wear resistance and hardness, O2 generally performs slightly better. For general-purpose tooling, both grades are widely used.
Does GCNOV provide custom manufacturing services for O2 steel?
Yes. GCNOV provides:
- CNC Machining
- Tool & Die Manufacturing
- Precision Grinding
- EDM Processing
- Heat Treatment
- Black Oxide Finishing
- Surface Coating
- Prototype Development
- Low-Volume Production
- Mass Production