Tool Steels used in the CNC Machine Shop
Introduction
Tool steels play a crucial role in various industries, providing the backbone for the creation of cutting tools, dies, and molds. Among the diverse array of tool steels available, A2, D2, H13, M2, O1, S7, and W1 stand out as high-performance options, each with unique properties suited for specific applications. In this article, we will delve into the characteristics and applications of these tool steels to better understand their strengths and limitations.
A2 Tool Steel:
Composition:
Carbon (C): 1%
Molybdenum (Mo): 1%
Chromium (Cr): 5%
Iron (Fe): Remainder
Physical Properties (Hardened):
Up to Rockwell 62 HRC Hardness
Ultimate tensile strength of 295 ksi
Yield tensile strength of 230 ksi
Use Cases:
Blanking and forming dies
Stamping dies
Shear blades
Thread rolling dies
Extrusion tooling
A2 tool steel is an air-hardening, cold-work steel known for its excellent combination of toughness and wear resistance. Comprising chromium, molybdenum, and vanadium, A2 provides good stability during heat treatment. Its ability to maintain high hardness at elevated temperatures makes it suitable for applications such as blanking dies, forming dies, and gauges.
D2 Tool Steel:
Composition:
Carbon (C): 1.5%
Molybdenum (Mo): 1%
Chromium (Cr): 12%
Vanadium (V): 1%
Iron (Fe): Remainder
Physical Properties (Hardened):
Up to Rockwell 61 HRC Hardness
Ultimate tensile strength of 290 ksi
Yield tensile strength of 219 ksi
Use Cases:
Cutting and stamping tools
Punches and dies
Forming tools
Thread rolling dies
Cold work applications
D2 tool steel is a cold-work tool steel and is renowned for its exceptional wear resistance. With a high level of hardness and good dimensional stability, D2 is often chosen for applications requiring high abrasion resistance, such as cutting tools for metal forming and stamping.
H13 Tool Steel:
Composition:
Carbon (C): 0.35%
Molybdenum (Mo): 1.5%
Chromium (Cr): 5%
Vanadium (V): 1%
Iron (Fe): Remainder
Physical Properties (Hardened):
Up to Rockwell 53 HRC Hardness
Ultimate tensile strength of 289 ksi
Yield tensile strength of 239 ksi
Use Cases:
Die casting dies
Extrusion dies
Forging dies
Hot shear blades
Injection molding tools
H13 is a hot-work tool steel recognized for its outstanding combination of toughness, heat resistance, and wear resistance. This steel is frequently employed in applications such as die casting, extrusion dies, and forging dies. H13's ability to maintain its hardness even at high temperatures makes it a preferred choice for demanding hot-work applications.
M2 Tool Steel:
Composition:
Carbon (C): 0.85% - 1.00%
Tungsten (W): 6%
Molybdenum (Mo): 5%
Chromium (Cr): 4%
Vanadium (V): 2%
Iron (Fe): Remainder
Physical Properties (Hardened):
Up to Rockwell 65 HRC Hardness
Ultimate tensile strength of 311 ksi
Use Cases:
High-speed cutting tools
Drill bits
End mills
Taps and reamers
Saw blades
M2 tool steel is a high-speed steel known for its excellent red hardness, wear resistance, and cutting ability. With tungsten, molybdenum, and vanadium in its composition, M2 performs well in high-speed machining applications, making it suitable for cutting tools like drills, end mills, and taps.
O1 Tool Steel:
Composition:
Carbon (C): 0.9%
Manganese (Mn): 1%
Tungsten (W): 0.5%
Chromium (Cr): 0.5%
Iron (Fe): Remainder
Physical Properties (Hardened):
Up to Rockwell 62 HRC Hardness
Ultimate tensile strength of 245 ksi
Yield tensile strength of 218 ksi
Use Cases:
Cutting tools
Blanking and forming dies
Thread cutting tools
Gauges and measuring tools
Woodworking tools
O1 tool steel is a general-purpose oil-hardening steel, recognized for its excellent machinability, wear resistance, and dimensional stability. O1 is commonly used for forming dies, blanking dies, and gauges. It is versatile and well-suited for applications that require a balance of hardness and toughness. O1 is commonly used in cold-work applications
S7 Tool Steel:
Composition:
Carbon (C): 0.5%
Molybdenum (Mo): 1.4%
Chromium (Cr): 3.25%
Iron (Fe): Remainder
Physical Properties (Hardened):
Up to Rockwell 57 HRC Hardness
Ultimate tensile strength of 293 ksi
Yield tensile strength of 220 ksi
Use Cases:
Chisels and punches
Shear blades
Forming dies
Impact tools
Hot work tools with high-impact resistance
S7 tool steel is an air-hardening shock-resistant steel known for its high-impact toughness. With added molybdenum and tungsten, S7 exhibits excellent wear resistance and machinability. This steel is commonly used for applications involving high-impact and shock-loading conditions, such as chisels, punches, and shearing blades.
W1 Tool Steel:
Composition:
Carbon (C): 0.6%-1.4%
Vanadium (V): 0.1%
Chromium (Cr): Varies
Manganese (Mn): Varies
Silicon (Si): Varies
Iron (Fe): Remainder
Physical Properties (Hardened):
Up to Rockwell 64 HRC Hardness
Ultimate tensile strength of 244 ksi
Yield tensile strength of 218 ksi
Use Cases:
Chisels and woodworking tools
Punches and stamps
Bending and forming tools
Knife blades
Cold-heading dies
W1 tool steel is a water-hardening carbon tool steel that is easy to machine and heat treat. W1 is often utilized for applications requiring a combination of high hardness and good toughness, such as woodworking tools, chisels, and punches. Its water-quenching properties make it a simple yet effective tool steel for various applications.
Conclusion
The selection of the right tool steel is crucial for achieving optimal performance in various industrial applications. A2, D2, H13, M2, O1, S7, and W1 tool steels each offer unique advantages, catering to specific requirements in terms of hardness, toughness, wear resistance, and heat resistance. Understanding the properties and applications of these high-performance tool steels is essential for making informed decisions in tool and die manufacturing processes.
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*Physical Property values based on Machinery’s Handbook 31