Contents
O6 Cold Work Steel: Properties, Heat Treat And Uses
- John
O6 tool steel offers outstanding hardness and superior wear resistance, making it perfect for precision-driven applications. Its distinctive graphite composition and oil-hardening characteristics guarantee consistent performance in challenging industrial environments.
In this article, we will highlight the key characteristics, heat treatment methods, and typical uses of O6 steel, helping you understand how it can meet the needs of your projects.
What Is O6 Tool Steel?
O6 tool steel is an oil-tempered graphite-based steel, also categorized as a cold-work material. Thanks to its evenly dispersed graphite particles, it provides excellent hardness and resistance to wear. O6 is supplied in forms such as bars and rods and is used for cutting dies, punches, and other tool applications. Its hardness up to 65 HRC can be achieved by hardening at 850°C – 880°C (1562°F – 1616°F).
At SteelPro Group, we specialize in providing high-quality O6 tool steel that meets the rigorous demands of precision tooling and manufacturing.
Standards And Equivalents of O6 Tool Steel
At SteelPro Group, we are dedicated to helping you make informed choices when it comes to O6 tool steel. Below is a simple breakdown of the key standards and their equivalent grades, designed to guide you in selecting the perfect steel for your specific requirements.
| Standards | Grades |
| UNS | T31506 |
| ASTM A681 | AISI O6 |
| FED QQ-T-570 | AISI O6 |
| SAE J437 | SAE 1065 |
| SAE J438 | SAE 1075 |
Chemical Composition of O6 Tool Steel
O2 tool steel, with its balanced carbon and low chromium content, offers excellent hardness and wear resistance. The carbon enhances hardenability and strength, while the minimal chromium ensures better toughness without compromising machinability.
| Element | Composition |
| Carbon (C) | 1.25 – 1.55% |
| Chromium (Cr) | ≤ 0.30% |
| Iron (Fe) | 96% |
| Manganese (Mn) | 0.70% |
| Molybdenum (Mo) | 0.25% |
| Phosphorus (P) | ≤ 0.030% |
| Silicon (Si) | 1.03% |
| Sulfur (S) | ≤ 0.030% |
Mechanical Properties of O6 Tool Steel
O6 steel is recognized for its superior hardness and outstanding strength. Its remarkable machinability and shear modulus emphasize its resilience and ability to resist deformation. Below is a summary of the mechanical properties of O6 tool steel:
| Property | Metric Units | Imperial Units |
| Hardness, Brinell | 752 | 752 |
| Hardness, Knoop | 850 | 850 |
| Hardness, Rockwell C | 65 | 65 |
| Hardness, Vickers | 819 | 819 |
| Bulk Modulus | 160 GPa | 23200 ksi |
| Shear Modulus | 80.0 GPa | 11600 ksi |
| Machinability | 130 % | 130 % |
- The values for Hardness (Brinell, Knoop, and Vickers) have been converted from the Rockwell C hardness measurement.
- Machinability is based on 100% machinability for a 1% carbon tool steel.
Physical Properties of O6 Tool Steel
O6 tool steel has high density, providing significant strength and hardness. It features low thermal conductivity, which helps to retain heat. Here is an overview of the main physical characteristics of O6 tool steel:
| Property | Metric Units | Imperial Units |
| Density | 7.85 g/cm³ | 0.284 lb/in³ |
| Thermal Conductivity | 30.0 W/m·K | 17.4 BTU·in/h·ft²·°F |
| Specific Heat Capacity | 0.45 J/g·K | 0.107 BTU/lb·°F |
| Melting Point | 1425 °C | 2597 °F |
| Coefficient of Thermal Expansion (20-100°C) | 11.0 µm/m·°C | 6.1 µin/in·°F |
O6 Tool Steel Fabrication And Heat Treatment
With our expertise in tool steel, SteelPro Group offers precise heat treatment services tailored to the specific needs of each client, maximizing the steel’s performance.
Forging
O6 tool steel is typically forged at temperatures between 1050°C (1922°F) and 1150°C (2102°F). The forging process should be followed by a controlled cooling rate to avoid warping.
Annealing
Heat the steel to 800°C (1472°F) to 850°C (1562°F) and allow it to cool slowly in the furnace to soften the steel and relieve stresses.
Hardening
Austenitizing
- For thicknesses less than 12.7 mm (0.5 in): Heat to 790°C(1450°F) – 815°C(1500°F).
- For thicknesses between 12.7 mm(0.5 in) and 50.8 mm(2 in): Heat to 815°C(1500°F) – 845°C(1550°F).
- For thicknesses greater than 50.8 mm (2 in): Heat to 845°C(1550°F) – 870°C (1600°F).
Quenching
Following austenitizing, quench the steel in oil or air, depending on the thickness, to rapidly cool and harden it. The quenching medium and process ensure the formation of martensite for hardness.
Tempering
Tempering should be performed at temperatures between 150°C – 650°C (300°F – 1200°F). Here is the hardness data for O6 tool steel after tempering in a table format:
| Temperature | Hardness |
| 150°C (300°F) | 63 – 64 HRC |
| 200°C (400°F) | 60 – 62 HRC |
| 250°C (500°F) | 58 – 60 HRC |
| 300°C (600°F) | 55 – 57 HRC |
| 350°C (650°F) | 52 – 54 HRC |
O6 Tool Steel Product Forms
SteelPro Group provides a comprehensive selection of O6 tool steel products, available in a variety of standard sizes. If you have specific requirements outside these ranges, we also offer custom sizes to meet your precise needs.
Below are the typical forms and dimensions of O6 tool steel available in the market:
O6 Tool Steel Bars
Diameter: 10 mm – 300 mm (0.4 in – 12 in)
Length: 3 m – 6 m (10 ft – 20 ft)
O6 Tool Steel Plates
Thickness: 5 mm – 100 mm (0.2 in – 4 in)
Width: 200 mm – 2500 mm (8 in – 98 in)
Length: 200 mm – 6000 mm (8 in – 236 in)
O6 Tool Steel Rounds
Diameter: 20 mm – 100 mm (0.8 in – 4 in)
O6 Tool Steel Sheets
Thickness: 1 mm – 10 mm (0.04 in – 0.4 in)
O6 Tool Steel Applications
With high hardness, wear resistance, and strength, O6 steel is an excellent choice for precise tooling applications. Its ability to maintain sharpness and resist wear under stress allows it to perform effectively in demanding environments.
- Die Casting Dies
- Wire Drawing Dies
- Injection Molds
- Perforating Dies and Punches
- Ring Gauges and Plug Gauges
- Cutting Tools
Reliable O6 Tool Steel for Your Precision Needs
At SteelPro Group, we understand that precision and reliability are crucial when selecting tool steel for your projects. That’s why we offer high-quality O6 tool steel and other cold work steel in various forms, including:
- Bars
- Plates
- Rounds
- Sheets
We provide both standard and custom sizes to meet your exact specifications. With our expertise in heat treatment and tailored solutions, we ensure you receive the right material, processed to maximize performance.
