Tool steel is a category of carbon and alloy steels designed specifically for manufacturing tools, dies, and molds. These steels are characterized by their high hardness, wear resistance, and ability to retain a cutting edge at elevated temperatures. They are essential in industries ranging from automotive manufacturing to aerospace, mold making, and construction.
Different grades of tool steel have varying chemical compositions, heat treatment capabilities, and performance characteristics. Understanding these grades and their applications helps engineers, manufacturers, and buyers select the right steel for the job.
In this article, we will explore the most common tool steel grades, their properties, and where they are used.
Tool steels are generally classified into six main types based on their properties and intended applications:
Water-Hardening Tool Steels (W-Series)
Cold-Work Tool Steels (O, A, D-Series)
Shock-Resisting Tool Steels (S-Series)
High-Speed Tool Steels (T, M-Series)
Hot-Work Tool Steels (H-Series)
Special-Purpose Tool Steels
Each category has its own strengths, limitations, and best-use cases.
Example Grades: W1, W2
Key Features:
Hardened by water quenching
High hardness and good wear resistance
Affordable but less resistant to high temperatures
Applications:
Hand tools such as chisels, hammers, and punches
Woodworking tools like plane blades and carving tools
Example Grades: O1, O2
Key Features:
Hardened by oil quenching to reduce distortion
Good wear resistance and toughness
Easy to machine in the annealed state
Applications:
Gears and shafts
Punches and dies
Knives and cutting tools
Example Grades: A2, A6
Key Features:
Hardened by air cooling, minimizing distortion during heat treatment
Good balance of wear resistance and toughness
High dimensional stability
Applications:
Shear blades
Molding dies
Forming tools
Example Grades: D2, D3
Key Features:
Very high wear resistance
Moderate toughness
Retains hardness up to 425°C
Applications:
Punches and dies for long production runs
Industrial knives
Cold extrusion tools
Example Grades: S1, S7
Key Features:
Exceptional toughness and impact resistance
Good wear resistance
Can withstand repeated shock loading
Applications:
Impact tools such as hammers and chisels
Dies for drop forging
Punches for heavy-duty work
Example Grades: M2, M42
Key Features:
Excellent cutting performance at high speeds
Good red hardness (maintains hardness at elevated temperatures)
High wear resistance
Applications:
End mills and drill bits
Gear cutters
Broaches and taps
Example Grades: T1, T15
Key Features:
Outstanding red hardness
Maintains sharp cutting edges under extreme heat
Very high wear resistance
Applications:
Heavy-duty cutting tools
Industrial machining operations
Milling and turning tools
Example Grades: H11, H13, H21
Key Features:
Designed to work at elevated temperatures
Good toughness and heat resistance
High thermal fatigue strength
Applications:
Die casting dies
Hot extrusion tools
Forging dies
These steels are developed for very specific industrial needs, such as plastic mold steels, corrosion-resistant tool steels, or high-impact resistance grades.
Example Grades: P20 (plastic mold steel), CPM 10V (powder metallurgy)
Applications:
Injection mold bases and cavities
Wear parts in severe service conditions
When selecting a tool steel grade, manufacturers consider:
Wear Resistance – For tools subject to abrasion
Toughness – For tools exposed to shock loads
Hardness – For maintaining sharp edges
Heat Resistance – For high-temperature applications
Machinability – For ease of manufacturing
Balancing these factors ensures the best performance and cost-effectiveness.
The performance of tool steel is heavily influenced by heat treatment, which includes hardening, tempering, and sometimes cryogenic treatment. Proper heat treatment maximizes the steel’s potential hardness, wear resistance, and toughness.
H13 hot-work tool steel is used in die casting dies for aluminum engine parts due to its high heat resistance.
D2 cold-work tool steel is chosen for long-run stamping dies because of its excellent wear resistance.
M42 high-speed steel is used for drill bits in high-speed CNC machining because it maintains hardness under heat.
Tool steel differs from structural or stainless steel in that it is optimized for hardness and wear resistance rather than general load-bearing or corrosion resistance. While stainless steels like 440C have good hardness, tool steels are designed for much more demanding cutting and forming operations.
Regular Sharpening: Keeps edges effective and reduces wear.
Proper Storage: Prevents corrosion, especially for carbon-rich grades.
Surface Coatings: Applying PVD coatings like TiN improves wear resistance.
Correct Use: Avoiding overload extends tool life.
Tool steel is a critical material in manufacturing industries, offering unique combinations of hardness, toughness, and wear resistance. From high-speed steel drill bits to heavy-duty forging dies, each grade serves a specialized purpose.
By understanding the strengths of each grade, manufacturers can select the most suitable tool steel for their specific applications. As a trusted supplier, sakysteel offers a wide range of tool steel grades in bars, plates, and customized forms, ensuring consistent quality for demanding industrial needs.