O1 Tool Steel

O1 is an oil-hardening cold-work tool steel offering good hardness, wear resistance, and machinability. Compared with A2 and D2, O1 is generally more economical and easier to machine in the annealed condition, making it suitable for dies, cutting tools, and precision tooling components with moderate wear requirements.

Appearance & Properties

Color: Silver-gray to dark gray

Density: Approx. 7.85 g/cm³

Hardness: Typically approx. 57–62 HRC after heat treatment

Corrosion Resistance: Poor

Machinability: Good when annealed; difficult after hardening

Wear Resistance: Good

Toughness: Moderate

Weldability: Poor

Magnetism: Magnetic

Heat Treatment: Oil hardening, annealing, tempering, etc.

Surface Treatments: Black oxide, nitriding, PVD coating, grinding, polishing, etc.

Typical Applications

O1 Tool Steel is widely used in die making, metalworking, precision machinery, stamping, and general industrial tooling.

Typical parts include punches, dies, shear blades, gauges, fixtures, guide components, forming tools, and precision parts requiring moderate wear resistance.

Advantages

• Good hardness and wear resistance

• Good machinability in the annealed condition

• Well-established heat-treatment process

• Generally lower cost than A2 and D2

• Suitable for general-purpose dies and tooling components

Limitations

• Higher heat-treatment distortion risk than A2 during oil quenching

• Generally lower wear resistance than D2

• Poor corrosion resistance

• Difficult to CNC machine after hardening