AISI O7 Cold Work Steel: Properties, Heat Treat and Uses

What Is O7 Tool Steel?

O7 tool steel is a high-carbon, high-alloy cold work material recognized for its outstanding durability, strength, and ability to maintain hardness under high-temperature conditions. It is commonly used in forms such as bars, rounds, plates, and sheets for making cutting tools, punches, dies, and mold components. After heat treatment, O7 can achieve a hardness of 58-64 HRC. 

SteelPro Group is a professional supplier of O7 tool steel, offering a range of products including O7 tool steel rounds, flats, and plates. We additionally offer a range of tailored services to suit your specifications.

Standards:

• UNS T31507
• ASTM A681
• FED QQ-T-570 
• GB/T1299

Equivalent Grades:

• JIS SKS3
• GB GCr12 

Chemical Composition of O7 Tool Steel 

O7 is able to maintain its strength at high temperatures and resist heat deformation. The presence of vanadium and molybdenum further boosts its wear resistance, while controlled carbon levels ensure a balanced mix of hardness and toughness. 

The table below outlines the elemental makeup of O7 tool steel..

Mechanical Properties of O7 Tool Steel 

O7 tool steel is known for its excellent hardness, toughness, and machinability, making it ideal for tools that require a balance of wear resistance and strength. 

The table below presents the mechanical characteristics of O7 tool steel.

• The machinability of O7 steel is based on 1% carbon water-hardening tool steel.

Physical Properties of O7 Tool Steel

O7 tool steel is known for its excellent dimensional stability and resistance to heat deformation. Its unique weight, heat transfer efficiency, and expansion traits guarantee consistent functionality across different working environments. 

The following table highlights the main physical attributes of O7 tool steel.

O7 Tool Steel Fabrication And Heat Treatment

Forging

O7 tool steel should be heated to a temperature range of 900-1200°C (1652-2192°F) for forging. It is important not to forge below 790°C (1454°F), as the steel could become brittle. 

Annealing

heat it uniformly to a temperature between 790-815°C (1454-1499°F). After reaching the target temperature, allow the steel to cool slowly in a furnace or another controlled environment. The cooling rate typically around 4-5°C per hour (7.2-9°F per hour).

After annealing, the hardness is typically reduced to about 217 HB (Brinell Hardness), making the steel easier to machine.

Hardening

O7 tool steel is heated to a uniform temperature between 790-820°C (1454-1508°F). If the tool steel has a thick cross-section, preheating to 300-500°C (572-932°F) is beneficial. Once the steel has reached the target temperature, it should be rapidly quenched in oil. This results in a hardness of approximately 58-64 HRC, depending on the specific conditions of the quenching process.

Tempering

After hardening, O7 tool steel should be tempered at temperatures ranging from 100-400°C (212-752°F). The steel should be held at the tempering temperature for at least 1 hour per 25mm (1 inch) of thickness. 

This ensures that the hardness is uniform throughout the material. The resulting hardness after tempering can vary depending on the temperature, typically falling between 50-64 HRC.

Here is a quick reference table for tempering temperatures and resulting hardness:

O7 Tool Steel Product Forms

SteelPro Group offers a wide range of O7 tool steel products in various forms to meet your specific needs. Even if your requirements fall outside the standard size ranges, we can provide custom solutions to accommodate special dimensions.

O7 Tool Steel Bars

Used for making shafts, pins, and other cylindrical components.

• Diameter: 10 mm – 300 mm (0.39 in – 11.81 in)
• Length: 100 mm – 4000 mm (3.94 in – 157.48 in)

O7 Tool Steel Rounds

Used for producing gears, axles, and rotary tools.

• Diameter: 20 mm – 250 mm (0.79 in – 9.84 in)
• Length: 500 mm – 3000 mm (19.69 in – 118.11 in)

O7 Tool Steel Plates

Ideal for making tool bases, die plates, and large components requiring high wear resistance.

• Thickness: 5 mm – 200 mm (0.20 in – 7.87 in)
• Width: 50 mm – 2500 mm (1.97 in – 98.43 in)
• Length: 200 mm – 6000 mm (7.87 in – 236.22 in)

O7 Tool Steel Sheets

Suitable for stamping dies, cutting tools, and thin-walled parts.

• Thickness: 0.5 mm – 10 mm (0.02 in – 0.39 in)
• Width: 100 mm – 1500 mm (3.94 in – 59.06 in)
• Length: 100 mm – 4000 mm (3.94 in – 157.48 in)

O7 Tool Steel Applications

O7 tool steel is well-suited for applications that require high wear resistance, toughness, and the ability to maintain hardness under heat. Its excellent stability during heat treatment and resistance to thermal deformation make it a preferred choice in industries like tooling and manufacturing.

Dies and Punches

Used for stamping and punching dies, its toughness and wear resistance make it durable under high-stress, high-impact conditions.

Cutting Tools

Ideal for knives, blades, and shear tools, O7 maintains a sharp edge and resists wear, ensuring long-lasting cutting performance.

Mold Components

O7 is used for injection molds, where its dimensional stability and resistance to wear make it suitable for complex, high-precision molds.

Machining Parts

Suitable for gears, shafts, and bushings, its toughness and hardness make O7 durable for heavy-load, high-wear applications.

High-Quality O7 Tool Steel

At SteelPro Group, we recognize the importance of choosing the right tool steel for your applications. That is why we offer a comprehensive range of O7 tool steel products, including bars, rounds, plates, and custom sizes to meet your exact specifications. We also offer a variety of D2 high-carbon tool steels.

Our Services:

• Turning, milling, and grinding
• Honing for precise dimensions and smooth finishes

• Annealing for stress relief
• Hardening to achieve desired hardness levels
• Tempering for enhanced toughness and durability

With SteelPro Group, you can rely on high-quality O7 tool steel and comprehensive processing services to ensure your components perform optimally!