Tool steels are alloy steels specifically engineered for cutting, shaping, forming, and machining applications. Among them, O1, A2, D2, and S7 are the most widely used grades due to their optimal balance of hardness, toughness, wear resistance, and dimensional stability.
O1 Tool Steel (Oil-Hardening)
O1 is a high-carbon, oil-hardening cold-work tool steel known for excellent dimensional stability and fine grain structure, making it ideal for precision tools.
Key Characteristics
• High hardness with excellent edge retention
• Good toughness and machinability
• Oil-hardening minimizes distortion
• Fine grain structure ensures superior surface finish
Refining Properties
• Oil quenched for controlled hardening
• Uniform hardness and dimensional accuracy
• Tempering improves toughness without loss of hardness
A2 Tool Steel (Air-Hardening)
A2 is an air-hardening, medium-alloy tool steel offering a strong balance between toughness and wear resistance, widely used for general tooling.
Key Characteristics
• Very good toughness compared to O-series
• Air-hardening provides excellent dimensional stability
• Moderate wear resistance
• Good machinability in annealed condition
Refining Properties
• Air quenched to reduce warping and cracking
• Forms a uniform martensitic structure
• Tempering increases toughness for shock resistance
D2 Tool Steel (High-Carbon, High-Chromium)
D2 is a high-carbon, high-chromium tool steel offering exceptional wear resistance and long service life. It is often referred to as semi-stainless tool steel due to its high chromium content.
Key Characteristics
• Extremely high wear and abrasion resistance
• High hardness up to ~62 HRC
• Excellent dimensional stability
• Improved corrosion resistance (≈12% Cr)
Refining Properties
• Air or oil hardening depending on application
• Carbide-rich microstructure enhances wear resistance
• Requires controlled heat treatment to prevent cracking
S7 Tool Steel (Shock-Resisting)
S7 is a shock-resisting tool steel known for extreme toughness, making it ideal for impact tools, chisels, and punches.
Key Characteristics
• Exceptional impact and shock resistance
• Good machinability with moderate wear resistance
• Air-hardening with minimal distortion
• Retains toughness at elevated temperatures
Refining Properties
• Air quenched to preserve toughness
• High-temperature tempering improves heat resistance
• Produces strong martensitic structure for impact loads
Typical Applications
✔ Cutting tools, punches, dies, molds
✔ Industrial tooling and forming tools
✔ Shear blades and slitting knives
✔ Impact tools, chisels, and hammers
✔ Wear-resistant machine components
Why Choose These Tool Steels
O1, A2, D2, and S7 tool steels cover a wide performance range — from precision cutting and wear resistance to extreme shock loading. Their proven heat treatability, reliability, and cost-performance balance make them essential materials for tooling, manufacturing, automotive, construction, and heavy engineering industries.