H10 is a high-performance hot work tool steel classified under the ASTM (American Society for Testing and Materials) standard, belonging to the chromium-molybdenum-tungsten alloy system. It is specifically engineered to withstand repeated exposure to high temperatures, mechanical stress, and thermal cycling, making it ideal for applications in hot working processes. Below is a detailed overview:
Chemical Composition
The typical chemical composition of H10 hot work tool steel is as follows:
Element Content Range Role
Carbon (C) 0.30–0.40% Provides a balance of hardness, strength, and toughness; forms carbides with alloying elements to enhance wear resistance.
Chromium (Cr) 3.00–4.00% Improves oxidation resistance, heat resistance, and hardenability; critical for maintaining surface stability at elevated temperatures.
Molybdenum (Mo) 2.00–3.00% Enhances high-temperature strength, thermal fatigue resistance, and hardenability; reduces susceptibility to tempering softening.
Tungsten (W) 1.00–2.00% Works synergistically with molybdenum to boost red hardness (ability to retain hardness at high temperatures) and wear resistance.
Silicon (Si) 0.80–1.20% Aids in deoxidation, improves high-temperature strength, and enhances resistance to scaling.
Manganese (Mn) 0.20–0.50% Enhances hardenability and reduces brittleness.
Vanadium (V) 0.30–0.60% Refines grain structure, improves wear resistance, and stabilizes carbides at high temperatures.
Phosphorus (P) ≤0.030% Minimized to avoid embrittlement.
Sulfur (S) ≤0.030% Controlled to ensure good toughness and hot workability.
Key Properties
H10 hot work tool steel is designed to excel in high-temperature environments, offering a unique combination of properties:
1. Excellent Thermal Fatigue Resistance
Resists cracking caused by repeated heating (up to ~600°C) and cooling cycles, a critical feature for hot work tools that undergo rapid temperature fluctuations during operation.
2. Good Red Hardness
Maintains hardness and mechanical strength at elevated temperatures, ensuring consistent performance in prolonged hot working processes such as forging, extrusion, or die casting.
3. Balanced Toughness and Wear Resistance
Combines sufficient toughness to withstand mechanical impact (common in hot forging) with wear resistance to endure friction against hot workpieces, extending tool life.
4. High Hardenability
Achieves uniform hardness across thick sections, ensuring consistent performance in large or complex tool geometries.
5. Oxidation Resistance
Forms a protective oxide layer at high temperatures, reducing scaling and degradation when exposed to air, which is essential for maintaining tool integrity in high-heat environments.
Physical Properties
Density: ~7.85 g/cm³
Melting Point: ~1450–1500°C
Thermal Expansion Coefficient: ~11.0×10⁻⁶/K (at 20–500°C)
Thermal Conductivity: ~35 W/(m·K) (at room temperature)
Mechanical Properties (After Heat Treatment)
Property Typical Value
Hardness 42–48 HRC (quenched and tempered)
Tensile Strength (Rm) ~1200–1500 MPa
Yield Strength (Rp0.2) ~1000–1300 MPa
Elongation (A) ~10–15%
Impact Toughness (Charpy V-notch) ≥25 J/cm² (at room temperature)
Heat Treatment Process
Proper heat treatment is essential to maximize H10’s resistance to heat, wear, and thermal fatigue:
1. Annealing
Purpose: Soften the steel for machining, relieve internal stress, and improve workability.
Process: Heat to 830–860°C, hold for 2–4 hours, then furnace cool slowly (≤50°C/hour) to below 500°C before air cooling.
Result: Hardness ≤235 HBW, ensuring ease of machining.
2. Quenching
Preheating: Two stages—first at 650–750°C, then at 850–900°C (to avoid thermal shock and ensure uniform heating).
Austenitizing: Heat to 1000–1050°C, hold for 30–60 minutes (based on section thickness) to dissolve carbides evenly.
Cooling: Quench in oil or compressed air (oil for deeper hardness penetration; air for minimal distortion in large tools).
3. Tempering
Purpose: Relieve quenching stress, reduce brittleness, and optimize the balance between hardness, toughness, and thermal stability.
Process: Temper at 500–650°C, hold for 2–4 hours per 25mm thickness, then air cool. Double tempering is recommended to eliminate retained austenite.
Result: Hardness of 42–48 HRC with enhanced resistance to thermal fatigue and softening at high temperatures.
Application Fields
H10 hot work tool steel is widely used in high-temperature manufacturing processes:
Hot Forging Dies: Suitable for forging steel, aluminum, and brass alloys (e.g., automotive crankshafts, gears, and structural components).
Extrusion Dies: Used for extrusion of non-ferrous metals like aluminum and copper (e.g., profiles, pipes, and heat sinks).
Die Casting Molds: Applied in die casting of aluminum and magnesium alloys, where resistance to thermal cycling is critical.
Hot Stamping Tools: Utilized in hot stamping processes for high-strength steel components in automotive manufacturing.
Industrial Furnace Components: Employed in parts requiring heat resistance, such as furnace fixtures and hot work holders.
Comparison with Similar Hot Work Steels
Feature H10 Hot Work Steel H11 Hot Work Steel H13 Hot Work Steel
Alloy Focus Chromium-molybdenum-tungsten Chromium-molybdenum Chromium-molybdenum-vanadium
Red Hardness Good Very Good Excellent
Toughness Good Excellent Excellent
Wear Resistance Good Good Very Good
Best For General hot forging, extrusion High thermal fatigue applications Severe hot work, high-impact scenarios
Summary
H10 hot work tool steel offers a reliable balance of thermal fatigue resistance, red hardness, and toughness, making it suitable for a range of high-temperature manufacturing applications. Its ability to withstand repeated heating and cooling cycles while maintaining mechanical integrity ensures long tool life in hot forging, extrusion, and die casting processes. For general hot work applications requiring a cost-effective yet durable material, H10 is a practical and performance-driven choice.