Best Tool Steels for Aluminum Extrusion Dies

For most general aluminum extrusion dies, H13 should be the first choice. It offers the best overall balance of wear resistance, hot hardness, toughness, and resistance to heat checking.

For mandrels, rams, dummy blocks, and other highly stressed tooling components, H11 may be a better choice when the main concern is cracking, bending stress, or fracture.

For tooling requiring higher hot hardness and dimensional stability, H12 can be considered, especially for hot extrusion dies, liners, and rams. The wider grade selection for extrusion tooling is in the tool steel selection guide for hot extrusion dies.

For mandrel tips and high-wear inserts, M2 or T1 high-speed steel may be used when localized friction and heat exceed what H13 or H11 can handle. M2 is usually the more balanced choice, while T1 is mainly used when maximum red hardness is required.

What Limits Aluminum Extrusion Die Life

Aluminum extrusion runs with billet temperatures around 340-510°C and normally without lubrication, so the die carries two loads at the same time: sustained compressive stress that can reach 1035 MPa (150 ksi), and continuous thermal cycling. Aluminum also tends to adhere to the die surface, which raises friction and shear stress at the bearing area.

Die life is therefore limited by three mechanisms: abrasive wear from metal flow, adhesive wear from sticking, and thermal fatigue. Heat checking, the network of surface cracks formed by repeated heating and cooling, is usually the dominant factor, and a grade that only looks hard on paper will not solve a heat-checking problem.

What each selection factor costs when it is under-specified. Heat checking, not hardness, is the factor that decides die life most often.

Working hardness for extrusion tooling sits in the 42-51 HRC band depending on the component, so the difference between H11, H12 and H13 comes from composition and carbide structure rather than from hardness itself. In European and Japanese nomenclature the two standard grades are 1.2343 (SKD6) for H11 and 1.2344 (SKD61) for H13.

Tool Steel Selection Table for Aluminum Extrusion Die Components

Grade by tooling component. The die body, the mandrel and the localized high-wear inserts are three different duty cycles inside one die set.

Aluminum extrusion tooling is not selected based on a single universal steel grade. The right choice depends on the component, stress level, wear risk, thermal exposure, and required service life.

H13 vs H11: How to Choose Between Wear Resistance and Toughness

H13 contains more vanadium than H11, typically around 1.0% compared with about 0.5% in H11. This higher vanadium content helps form harder vanadium carbides, which improve wear resistance and heat-checking resistance. For this reason, H13 is widely used as the standard general-purpose material for solid and hollow aluminum extrusion dies.

Choose H13 when the tooling is needed:

• Balanced General Performance: H13 provides a strong mix of hot hardness, toughness, wear resistance, and thermal fatigue resistance.
• Better Wear Resistance Than H11: Higher vanadium content supports more hard carbide formation.
• Resistance to Heat Checking: H13 is suitable for die surfaces that are repeatedly heated and cooled.
• Standard Extrusion Die Performance: It is usually the safest first choice for general solid and hollow dies.

H11 has lower vanadium content, which gives it slightly lower wear resistance than H13, but better fracture toughness and ductility. This makes H11 a strong choice for components exposed to high bending stress, shock loading, or a risk of cracking.

Choose H11 when the tooling is needed:

• Higher Toughness: H11 is suitable when fracture resistance matters more than wear resistance.
• Lower Cracking Risk: Useful for long mandrels and highly stressed structural tooling.
• Better Ductility: H11 can withstand bending stress and mechanical shock better.
• Structural Reliability: Suitable for rams, dummy blocks, die backers, and other support components.

Choose H13 when wear resistance and general die life are the main concerns. Choose H11 when cracking resistance and toughness are more important.

When to Use H12 for Aluminum Extrusion Tooling

H12 is also a chromium hot-work tool steel, but its role is more specific than H13 or H11.

H12 contains tungsten in addition to chromium, molybdenum, and vanadium. This gives it greater resistance to softening at high temperatures and improved dimensional stability under demanding hot-work conditions. H12 may be selected for hot extrusion dies, liners, and rams where hot hardness and warpage control are important.

Choose H12 when the tooling is needed:

• Complex Die Geometry: Better dimensional stability helps reduce the risk of warpage and distortion.
• High Thermal Load: Tungsten alloy support improves resistance to softening at elevated temperatures.
• Heavy-Duty Support Tooling: H12 can be used for liners, rams, and hot-extrusion dies where high hot hardness is important.
• Specific Stability Requirements: It is useful when dimensional control matters more than simply choosing the most common grade.

In most practical buying decisions, H13 and H11 remain the primary choices, while H12 is an alternative for specific requirements in hot hardness and stability.

When to Use M2 or T1 for Mandrel Tips and High-Wear Inserts

M2 and T1 are high-speed steels. They are not general die-body materials for aluminum extrusion dies. They are used selectively for mandrel tips, die inserts, or other localized high-wear areas.

The main die body needs toughness and structural strength. Tips and inserts may need much higher local wear resistance and hot hardness.

Compared with H13 or H11, M2 and T1 can be heat-treated to higher hardness and can maintain hardness under severe localized heat. This makes them suitable when the friction and thermal load at a small tooling area are too high for standard hot-work steel.

Choose M2 when the tooling needs:

• Severe Localized Friction: High carbide content provides the wear resistance needed for mandrel tips and inserts.
• Balanced Chipping Resistance: M2 offers a better balance of toughness than many heavier-alloyed high-speed steels.
• Mixed Wear and Impact Conditions: It is suitable for applications where the insert must resist both abrasion and mechanical stress.
• Cost-Effective Performance: M2 is usually more economical than tungsten-rich high-speed steels.

M2 is usually the more practical high-speed steel choice for mandrel tips and inserts because it provides strong wear resistance and a better toughness balance than many higher-alloyed high-speed steels.

Choose T1 when the tooling is needed:

• Maximum Red Hardness: T1 is suitable for applications where the insert must resist thermal softening at high temperatures.
• High Thermal Stability: Its tungsten-rich composition helps retain hardness at elevated temperatures.
• Thermal Softening Resistance: Useful when softening is the primary failure mode.
• Lower Chipping Risk: T1 is less attractive if impact failure or edge chipping is common.

T1 is a classic tungsten high-speed steel with excellent red hardness, but it is usually more expensive and less tough than M2. In most cases, M2 is the more balanced choice, while T1 is reserved for extreme thermal softening problems.

Why Nitriding Response Matters in Aluminum Extrusion Die Steel Selection

The nitriding response is an important reason H11, H12, and H13 are widely used for aluminum extrusion dies.

Aluminum extrusion dies need a hard, wear-resistant surface supported by a tough core. H-series hot-work steels contain chromium, molybdenum, and vanadium, which can form stable nitrides during nitriding. This allows the die surface to achieve high wear resistance while the core remains tough enough to support heavy extrusion pressure.

The two halves of a nitrided extrusion die: a hard working surface carried by a core that is still tough enough to take the press load.

For this reason, nitriding should not be treated as a separate afterthought. If the selected steel does not respond well to nitriding, it may not perform well in aluminum extrusion service even if its base hardness looks acceptable.

This is one reason why H13, H11, and H12 are more suitable than many general-purpose alloy steels for aluminum extrusion dies. They can combine a nitrided working surface with a tough supporting core.

Die design decisions that decide the steel

The grade is only half the answer. Four design choices change the load a die carries, and they can move the choice away from the standard H13 answer.

• Solid or hollow. A hollow die splits the metal into ports and rewelds it in the welding chamber, so the mandrel and the bridges take bending load that a solid die never sees. On those components toughness outranks wear resistance. The two families are compared on the aluminum extrusion die types page.
• Bearing length. A longer bearing raises the pressure and the friction at the land, which is where adhesive wear starts, so it pushes the requirement towards the more wear-resistant end of the H11 / H12 / H13 range. How the bearing is measured is on the die bearing length page.
• Die size against the billet. A profile that needs a large circumscribing circle leaves less steel around the bearing for support, so the die has to be thicker and tougher for the same shape. The limit is set out on the circumscribing circle diameter page.
• The load path behind the die. The backer, bolster, liner and dummy pad carry the press load instead of forming the profile, so they are chosen for toughness and hot strength rather than for the hardest available grade.

A die that balances the flow avoids the hot spots where one part of the profile runs faster than the rest, and a bearing that stays cooler wears more slowly whatever grade it is made of. How a die fails when the design is wrong is described on the aluminum extrusion die wear page.

Practical Recommendation

For most aluminum extrusion dies, H13 is the best starting choice because it gives the most balanced combination of wear resistance, hot hardness, toughness, thermal fatigue resistance, nitriding response, and cost.

Choose H11 when the tooling component is highly stressed, and the main risk is cracking, bending, or fracture.

Choose H12 when hot hardness, dimensional stability, or warpage control is especially important.

Choose M2 for mandrel tips and high-wear inserts when local wear resistance needs to be improved without making the entire die body too hard or too costly.

Choose T1 only when maximum red hardness is required, and the insert primarily fails due to thermal softening rather than chipping.

In a practical aluminum extrusion tooling package, the best solution is often not one steel for every part. A strong design may use H13 for the main die, H11 for highly stressed mandrels or support tooling, and M2 or T1 for localized high-wear inserts. This gives the tooling a better balance of wear life, crack resistance, and hot-work stability.

What sets the cost of an aluminum extrusion die

The price of the die steel is a small part of what an aluminum extrusion die costs. What a press shop actually pays is the cost per tonne of profile: the price of the die divided by the billets it presses before rework, plus the scrap produced while the die settles in, plus the press time lost changing it.

That is why the cheapest grade on a quotation is often the most expensive die. H13 and H11 cost more per kilogram than a general-purpose hot-work steel, but they hold their hardness and their bearing longer, so the die presses more billets between reworks. A grade that heat checks early does the opposite: it is reworked, re-nitrided and fitted again, and every one of those cycles costs press time.

Three things decide the answer in practice: the extrusion alloy, because a 7000 series profile loads the die several times harder than 6063; the profile itself, because wall thickness and the number of hollows set the bearing load; and the surface treatment, because a nitrided bearing runs longer between reworks than a bare one. Grade, size, quantity, extrusion alloy and profile are the five things needed to quote die steel against a die life rather than against a price list.

Where to go next

Related selection pages on this site: Selection of Tool Steels for Cold Forming Hexagon Nuts; Hot Extrusion Die Steel Selection | H13 H11 H21 H10 Tool Steel Supplier; Copper & Brass Extrusion Tool Steel Selection | H21 H26 Supplier; Cold Extrusion Die Steel Selection Guide; ESR Tool Steel.