O1 Tool Steel
O1 tool steel, also known as 1.2510 steel, is an extremely versatile and popular material for a variety of cold work applications. O1, known for its high wear resistance and dimensional stability, strikes a compelling mix between performance and cost. Its oil hardening process makes it easily machinable and attainable with minimum equipment, making it a popular choice among tool and die manufacturers worldwide.
Chemical Composition
The following table shows the chemical composition of O1 tools steels.
| Element | Content (%) |
| C | 0.85-1.00 |
| Mn | 1.00-1.40 |
| Si | 0.50 |
| Cr | 0.40-0.60 |
| Ni | 0.30 |
| W | 0.40-0.60 |
| V | 0.30 |
| Cu | 0.25 |
| P | 0.03 |
| S | 0.03 |
Physical Properties
The physical properties of O1 tool steels are outlined in the following table.
| Properties | Metric | Imperial |
| Density (hardened to 62 HRC) | 7.81 g/cm3 | 0.282 lb/in3 |
| Density (@399°C/ 750°F, hardened to 62 HRC) | 7.70 g/cm3 | 0.278 lb/in3 |
| Density (@191°C/ 375°F, hardened to 62 HRC) | 7.75 g/cm3 | 0.280 lb/in3 |
| Melting point | 1421°C | 2590°F |
Mechanical Properties
The mechanical properties of O1 steels are tabulated below.
| Properties | Metric | Imperial |
| Hardness, Brinell (soft annealed -delivery condition) | 190 | 190 |
| Hardness, Rockwell C (tempering temp 300-1200°F) | 34.0-64.0 | 34.0-64.0 |
| Elastic modulus (hardened to 62 HRC) | 193 GPa | 28000 ksi |
| Elastic modulus (@399°C/750°F, hardened to 62 HRC ) | 172 GPa | 25000 ksi |
| Elastic modulus (@191°C/375°F, hardened to 62 HRC) | 186 GPa | 27000 ksi |
| Compressive yield strength (0.2%, hardened to 50 HRC) | 1350 MPa | 196000 psi |
| Compressive yield strength (0.2%, hardened to 55 HRC) | 1800 MPa | 261000 psi |
| Compressive yield strength (0.2%, hardened to 60 HRC) | 2150 MPa | 312000 psi |
| Compressive yield strength (0.2%, hardened to 62 HRC) | 2200 MPa | 319000 psi |
O1 boasts impressive wear resistance, making it ideal for applications where tools encounter high levels of friction and abrasion. This characteristic allows tools made from O1 to retain their sharp edges and functionality for extended periods, minimising downtime and maintenance requirements.
Thanks to its oil hardening process, O1 exhibits excellent machinability. This allows for efficient shaping and finishing with minimal equipment, making it accessible to a wider range of toolmakers and reducing production costs.
O1 offers a good balance between hardness and toughness. This combination ensures that tools can withstand the stresses and impacts encountered during cold work applications without succumbing to brittle fractures.
Thermal Properties
The table below shows the thermal properties of O1 tool steels.
| Properties | Conditions | ||
| T (°C) | Treatment | ||
| Thermal expansion | 10.6 x 10-6/ºC | 20-260 | - |
O1 tool steel offers a compelling combination of wear resistance, dimensional stability, machinability, toughness, and affordability. Its versatility and ease of use make it a favourite amongst tool and die makers worldwide, suitable for a vast array of cold work applications.
