H10 Hot-Work Tool Steel Properties and Applications

H10 Tool Steel is a specialized material engineered for challenging hot-work environments. With our extensive experience in tool steel, we provide this information to help you determine if H10 is the right fit for your needs.

1. H10 Tool Steel Chemical Composition

The performance of H10 is attributed to its carefully controlled chemical composition. The typical weight percentages are:

• Carbon (C): 0.35-0.45%
• Manganese (Mn): 0.20-0.70%
• Silicon (Si): 0.80-1.25%
• Chromium (Cr): 3.00-3.75%
• Molybdenum (Mo): 2.00-3.00%
• Vanadium (V): 0.25-0.75%
• Phosphorus (P): 0.030% max
• Sulfur (S): 0.030% max
• Nickel + Copper (Ni+Cu): 0.75% max

2. H10 Tool Steel Properties

H10 steel delivers a combination of properties essential for hot-work tooling:

• Heat Resistance: Excellent resistance to softening at elevated temperatures, crucial for maintaining tool integrity during operation.
• Hot Hardness: Retains high hardness levels even at high operating temperatures. Typical working hardness is 45–50 HRC, with quenched hardness reaching 56-59 HRC.
• Toughness: Good toughness at normal working hardness, attributed to its lower carbon and alloy content compared to some other grades.
• Thermal Fatigue Resistance: Withstands repeated heating and cooling cycles.
• Wear Resistance: Good resistance to wear, particularly erosive wear at high temperatures, enhanced by the vanadium content.
• Thermal Conductivity: Possesses relatively high thermal conductivity (approx. 32 W/m·K) due to its ~3% chromium content, compared to ~26 W/m·K for 5% chromium steels like H11/H13. This aids in heat dissipation.
• Hardenability: High hardenability allows for air cooling (air quenching) to achieve through-hardening, even in large sections.

3. H10 Tool Steel Heat Treatment

Proper heat treatment is essential to optimize H10’s performance. The process controls the steel’s microstructure to achieve the desired mechanical properties.

3.1 Annealing

Annealing softens the steel, relieves stress, and prepares the microstructure for hardening.

1. Heating: Heat the steel to 845–900°C (1550–1650°F).
2. Soaking: Ensure uniform temperature throughout the material.
3. Cooling: Slow cool at a controlled rate of 22°C/h (40°F/h).
4. Result: Target annealed hardness of 192–229 HB.
5. Protection: Due to its Molybdenum content, protect H10 from decarburization during annealing.

3.2 Hardening

Hardening involves transforming the steel’s structure to achieve high hardness.

1. Preheating: Preheat uniformly to 815°C (1500°F).
2. Austenitizing: Rapidly heat to the hardening temperature range of 1010–1040°C (1850–1900°F).
3. Soaking: Hold at the austenitizing temperature for 15 to 40 minutes to allow for phase transformation and carbide dissolution.
4. Quenching: Air quench (A) is the recommended method. Air hardening allows for through-hardening, even in larger sections. Rapid air cooling transforms austenite into hard, martensitic steel.
5. Result: Typical as-quenched hardness is 56–59 HRC.

3.3 Tempering

Tempering is crucial after quenching to improve toughness and stability.

1. Process: Reheat the hardened steel to a specific temperature below the transformation range, hold it, and then cool it.
2. Purpose: Relieve internal stresses, enhance toughness and ductility, and stabilize the microstructure for service conditions.
3. Temperature: Hot-work steels, such as H10, require high-temperature tempering to ensure stability during high-temperature operation. H10 demonstrates superior resistance to softening above 540°C (1000°F) compared to H11, maintaining properties effectively at service temperatures.

4. H10 Tool Steel Applications

H10’s property profile makes it suitable for various demanding hot-work applications:

• Die Casting: Dies for light metal and copper casting, particularly components subject to high thermal stress.
• Forging: Press forging dies where prolonged contact generates significant heat.
• Extrusion: Mandrels for hot extrusion processes.
• General Hot Work: Tooling requiring good heat checking resistance and resistance to softening at high temperatures.

Compared to grades like H14/H19, H10 offers better ductility. While its lower chromium content slightly reduces hardenability compared to H11 and H13 tool steel, the high molybdenum content largely compensates. Its higher thermal conductivity remains a key advantage in certain applications.