Tool Steel (Fe+C+alloy)
Tool steels are a family of high-carbon, high-alloy steels engineered for exceptional hardness, wear resistance, and toughness at elevated temperatures. They are essential for cutting tools, dies, molds, and precision components. Classified into series (A, D, H, M, O, S, T, W) based on quenching method and application.
Properties
- Density
- 7,700–8,100 kg/m³
- Melting Point
- 1,400–1,450 °C
- Boiling Point
- 2,750 °C
- Thermal Conductivity
- 20–30 W/(m·K)
- Electrical Resistivity
- 5.5 × 10⁻⁷ Ω·m
- Tensile Strength
- 700–2,500 MPa
- Yield Strength
- 400–2,000 MPa
- Hardness
- 58–67 HRC
- Elongation
- 1–15%
- Crystal Structure
- BCT (Martensite, tempered)
Common Grades
- A2 (1.2363): Air-hardening, medium-alloy cold-work steel. Punches, dies, gauges.
- D2 (1.2379): High-carbon, high-chromium cold-work steel. Excellent wear resistance. Blanking dies, knives.
- H13 (1.2344): Hot-work tool steel. Die casting dies, extrusion tools, forging dies.
- M2 (1.3343): Molybdenum high-speed steel. Drill bits, end mills, taps, saw blades.
- O1 (1.2510): Oil-hardening cold-work steel. Hand tools, jigs, templates, gauges.
- S7 (1.2357): Shock-resisting tool steel. Chisels, pneumatic tools, shear blades. Excellent impact toughness.
- CPM S30V: PM stainless tool steel. Premium knife blades — exceptional edge retention and corrosion resistance.
Applications
- Die Making: Stamping dies, forming dies, progressive dies, die casting molds
- Cutting Tools: Drill bits, end mills, lathe tools, saw blades, reamers
- Plastic Molds: Injection mold cavities, cores, inserts, hot runner components
- Metal Forming: Punches, blanking tools, bending tools, deep-drawing tools
FAQ
What is the best tool steel for general-purpose dies?
D2 (1.2379) is the most popular choice for general cold-work dies. It offers excellent wear resistance (high chromium and carbon), good dimensional stability during heat treatment, and can achieve 58–62 HRC. For hot-work applications, H13 is the standard choice.
What is the difference between hot-work and cold-work tool steel?
Cold-work tool steels (A, D, O series) are designed for operations below 200°C and prioritize hardness and wear resistance. Hot-work tool steels (H series) maintain strength and resist thermal fatigue at 300–600°C, making them suitable for die casting and forging dies.
How is tool steel heat treated?
The typical process is: (1) Austenitize — heat to 800–1,200°C depending on grade, (2) Quench — in oil (O-series), air (A-series), or water (W-series), (3) Temper — reheat to 150–600°C (usually twice) to achieve the target hardness and toughness balance. Each grade has specific temperatures that must be precisely controlled.
What is PM (Powder Metallurgy) tool steel?
PM tool steels like CPM S30V and ASP2060 are produced by atomizing molten steel into fine powder, then consolidating by hot isostatic pressing. This produces ultra-fine, uniform carbide distribution impossible in conventional casting — giving superior toughness, grindability, and wear resistance at the same hardness level.