AISI H11 Tool Steel Technical Overview

At Aobo Steel, we understand the importance of selecting the right material for demanding applications. With over 20 years of forging experience, particularly in tool steels such as H11 tool steel, we offer both high-quality products and the technical expertise to support your needs. Here’s a straightforward look at H11 (1.2343) steel.

H11 steel is a 5% chromium hot-work tool steel (AISI designation). It belongs to a group known for its exceptional performance in high-temperature applications, thanks to its chromium content and additions such as molybdenum and vanadium.

1.  H11 tool steel Chemical Composition

The specific composition can have slight variations, but typically, H11 steel includes:

• Carbon (C): 0.37-0.43%
• Mangan (Mn): 0.80-1.00%
• Crom (Cr): 4.75-5.25%
• Molibden (Mo): 1.20-1.40%
• Vanadiu (V): 0.40-0.60%

This balance of elements gives H11 its distinct characteristics, making it suitable for both tooling and structural uses. Aobo Steel can provide exact specifications for the H11 material we supply.

2. Key Properties of H11 tool steel

H11 offers a solid combination of properties vital for hot-work tooling:

2.1 Hardenability

H11 has deep hardenability. This means large sections, even up to 150 mm (6 inches), can be hardened throughout by simple air cooling. The benefit is less risk of distortion or stress compared to faster oil or water quenching.

2.2 Secondary Hardening

This steel exhibits secondary hardening when tempered at temperatures above 510°C (950°F). Fine alloy carbides form, increasing hardness and helping the steel resist softening at operating temperatures. This is critical for tools used in hot environments.

2.3 Toughness and Shock Resistance

Compared to some higher-alloy hot-work steels, such as H19 or H21, H11 offers excellent toughness and shock resistance. Its higher ductility means it’s less likely to fracture under impact.

2.4 Hot Hardness and Temper Resistance

H11 maintains good hardness at elevated temperatures, performing reliably up to around 540°C (1000°F) in many applications. Its temperature resistance ensures it retains strength even after exposure to heat.

2.5 Wear Resistance

While H11 offers reasonable wear resistance, other tool steels might be selected if wear is the primary concern. However, for many hot-work applications, its wear performance is adequate.

2.6 Resistance to Heat Checking

H11 is specifically designed to resist thermal fatigue, a common issue for tools that undergo repeated heating and cooling cycles.

2.7 Machinability

In its annealed (softened) state, H11 exhibits good machinability, with a rating of around 70, compared to a 1% carbon steel benchmark of 100.

3. Heat Treatment of H11 tool steel

Correct heat treatment is crucial to achieve optimal performance from H11.

3.1 Annealing

To soften the steel for machining, heat to 845-900°C (1550-1650°F) and cool slowly (approx. 22°C/h or 40°F/h). Target hardness is typically 192-229 HB.

3.2 Întărire

Preheat around 815°C (1500°F). Austenitize at 995-1025°C (1825-1875°F) for 15-40 minutes (depending on size), then air cool. Expected as-quenched hardness is 53-55 HRC.

3.3 Revenirea

Tempering reduces stress and adjusts the hardness and toughness. For H11, tempering is usually done above the secondary hardening temperature (510°C / 950°F).

• Tempering at 540°C (1000°F) typically yields a hardness of around 56 HRC.
• Higher tempering temperatures (e.g., 650°C / 1200°F) reduce hardness (approx. 33 HRC) but increase toughness.
• Double tempering is often recommended for optimal results.

4. Applications for H11 Steel

H11’s properties make it suitable for:

• Matrice de turnare sub presiune: Especially for aluminum, zinc, and magnesium.
• Forging Dies & Tooling: Inserts, punches, piercers, mandrels for hot forging aluminum, magnesium, and steel.
• Scule de extrudare la cald: Dies, dummy blocks, mandrels for aluminum and magnesium.
• Lame de forfecare la cald: For light to medium-duty shearing.
• Componente structurale: High-strength parts, particularly in aerospace (e.g., H11 Mod for landing gear, airframes).
• Mandrels: Widely used for mandrels in various extrusion processes.
• Coining Dies: Where resistance to splitting stress is needed.

5. H11 vs. H13 Steel

H13 is very similar to H11. The primary difference is that H13 has a higher vanadium content (approximately 1.0% vs. 0.5% in H11). This gives H13 slightly better wear resistance, hot hardness, and temper resistance. However, H11 often offers slightly better toughness and can be preferred for general aluminum die casting hardness levels. H13 is also commonly used for plastic injection molds.

6. Weldability

H11 is considered readily weldable, using standard inert-gas or coated electrode methods with filler metal of similar composition.

7. Availability

Aobo Steel can supply H11 in various forms, including bars, blocks, and forgings, meeting standard specifications. Modified versions, such as the H11 Mod (for higher strength), also exist.

8. Surface Treatments

For enhanced wear resistance, H11 can be nitrided. This surface hardening process can create a very hard case (over 1000 HV / >70 HRC), which is beneficial for applications such as forging and extrusion dies.

Concluzie

H11 tool steel provides a reliable combination of toughness, hardenability, shock resistance, and good performance at high temperatures. It’s a versatile choice for many hot-work tools and demanding structural parts.

Understanding these technical details helps in selecting the right steel and treatment for your specific factory needs, whether for die casting, forging, extrusion, or other applications.

At Aobo Steel, we have the experience to help you select and utilize H11 effectively. Contact us with your specific requirements or questions.