ThePipingMart Blog Grades O7 Tool Steel (UNS T31507) – Composition, Properties and Uses

O7 Tool Steel (UNS T31507) – Composition, Properties and Uses

Tool Steel O7

Tool Steel O7 often referred to as “oils hardening” steel, is a highly versatile steel that can be used in many industries and applications. It is designed to have superior heat resistance and corrosion resistance and can withstand higher temperatures without degrading. If you’re in need of strong and reliable tool steel, look no further than O7 Tool Steel, also known as UNS T31507 or  SAE-AISI O7 steel. This alloy is known for its high carbon content and ability to withstand high compression levels. With chromium, molybdenum, and tungsten composition, O7 Tool Steel has excellent wear resistance and can maintain its hardness even in high temperatures. In addition to these properties, it also has good dimensional stability and can be easily machined. Whether you’re working in the manufacturing or construction industry, O7 Tool Steel is a top choice for your tool steel needs. This article will provide an overview of the benefits and uses of Tool Steel O7, its corrosion resistance, heat resistance, heat treatment process and machining requirements.

What Forms of O7 Tool Steel is Available at Piping Mart?

  • Nut
  • Bar
  • Bolt
  • Pipe
  • Screw
  • Tubing
  • Valves
  • Washers
  • Flanges
  • Fasteners
  • Electrodes
  • Stud Bolts
  • Sheet Plates
  • Pipe Fittings
  • Forged Fitting
  • Instrumentation Fittings

O7 Tool Steel Composition

Element Content (%)
Iron, Fe ~95%
Carbon, C 1.10-1.30
Manganese, Mn 1.00
Silicon, Si 0.60
Chromium, Cr 0.35-0.85
Nickel, Ni 0.30
Molybdenum, Mo 0.30
Tungsten, W 1.00-2.00
Vanadium, V 0.40
Copper, Cu 0.25
Phosphorous, P 0.03
Sulfur, S 0.03

O7 Tool Steel Physical Properties

Properties Metric Imperial
Density 7.80 g/cm3 0.282 lb/in3

O7 Tool Steel Mechanical Properties

Properties Metric Imperial
Hardness, Rockwell C 58.0-64.0 58.0-64.0
Bulk modulus 140 GPa 20300 ksi
Shear modulus 80.0 GPa 11600 ksi
Machinability (based on 1% carbon water-hardening tool steel) 85% 85%
Poisson’s ratio (25°C) 0.27-0.30 0.27-0.30
Elastic modulus (25°C) 190-210 GPa 27557-30458 ksi

O7 Tool Steel Thermal Properties

Properties Metric Imperial
CTE, linear 11.2 mm/m°C 6.22 min/in°F

O7 Tool Steel Equivalents

  • ASTM A681
  • FED QQ-T-570
  • UNS T31507

O7 Tool Steel Uses

Tool steel O7 is a carbon and manganese, oil-hardened steel that offers exceptional performance for a variety of industrial and commercial purposes. Its versatility makes it one of the most popular general-purpose tool steels used in a multitude of applications such as blanking, piercing, punch making, stamping, forming, thread rolling, deep drawing and broaching. Its unique hardness and resilience make it ideal for high-speed manufacturing cutting and cold work tools that demand longevity and resistance to wear over repeated exposure to extreme temperatures. Tool steel O7 is commonly employed in the construction of dies for cutting hard alloys, and dies are used for cold-forming metals with increased ductility. Top-grade manufacturers often use tool steel O7 for forging presses, shearing blades and mandrels due to its high fatigue resistance.

O7 Tool Steel Uses in Industries

Automotive Industry

O7 tool steel is commonly used in the automotive industry due to its high strength and wear resistance. It is often used to make parts such as engine components, gears, and bearings. Its ability to withstand high temperatures and resist deformation makes it an ideal choice for these critical components.

Aerospace Industry

In the aerospace industry, O7 tool steel is used for its high strength-to-weight ratio and resistance to corrosion. It is commonly used in the construction of aircraft engines, landing gear, and other structural components. Its durability and reliability make it a top choice for this safety-critical industry.

Oil and Gas Industry

The oil and gas industry relies on O7 tool steel for its toughness and resistance to corrosion in harsh environments. This type of steel is commonly used in drilling equipment, valves, and pumps exposed to extreme pressure and corrosive substances.

Defence Industry

In the defence industry, O7 tool steel is utilized for its strength, toughness, and ability to withstand extreme conditions. It can be found in various military equipment, such as firearms, tanks, and armoured vehicles, where reliability and performance are crucial factors.

O7 Tool Steel Benefits

Tool Steel O7 provides excellent toughness, wear resistance, abrasion resistance, shock resistance, strength at elevated temperatures and good stability in hardening. It can also be tempered at low temperatures making it suitable for cold work tools such as blanking dies or forming dies. It is also great for high-impact tools like chisels or punches because of its excellent high tensile strength.

O7 Tool Steel Corrosion Resistance

Tool Steel O7 has superior rust resistance compared to other tool steels due to its higher chromium content (1%). This makes it ideal for industrial environments with high humidity levels or areas where rust could be a major issue. This type of steel also has good weldability, although preheating may be required to ensure proper bonding between pieces.

O7 Tool Steel Heat Resistance

Tool Steel O7 has a higher melting point than other tool steels (2192°F), which makes it ideal for applications that require a high-temperature operation, such as jet engines and gas turbines. Additionally, this type of steel will not lose its hardness when exposed to extreme temperatures making it suitable for use in hot work operations such as forging or extrusion.

O7 Tool Steel Heat Treatment

The heat treatment process for Tool Steel O7 involves heating the material until it reaches around 1750°F, then oil quenching until it reaches room temperature before tempering at 350°F to achieve desired hardness properties. The tempering process helps to reduce brittleness while increasing strength and ductility, which are important factors in maintaining tool performance over time.

O7 Tool Steel Machining

When machining Tool Steel O7 it is important to remember that it is air-hardening steel, so it should not be ground after hardening as this could cause cracking or distortion due to uneven cooling rates within the material’s structure. Additionally, cutting speeds should be kept low to avoid overheating the material, which could lead to premature failure of the tooling components. Furthermore, coolants should always be used during machining processes in order to prevent any potential damage from friction-generated heat when drilling or milling this material type.


In conclusion, Tool Steel O7 is an excellent choice for many industrial applications due to its superior corrosion resistance, heat resistance and machinability characteristics, coupled with its ability to withstand higher temperatures without degradation over time. Its heat treatment process enables maximum hardness properties while maintaining strength and ductility, which are key factors for successful tool performance regardless of application usage scenario. When machined correctly using appropriate speeds and coolants along with proper preheating procedures prior to welding, if necessary, this type of steel can provide years of reliable service even under extreme conditions encountered in many industrial environments today.

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