H13 vs A2 tool steel: A comprehensive comparison

H13 vs A2 tool steel: What is the difference between A2 and H13 steel? H13 and A2 are both widely used tool steels, but they belong to different classifications and have different compositions and properties, especially in terms of temperature resistance, wear resistance, and toughness.

H13 tool steel is a very popular hot work tool steel. It is designed for applications where tools are repeatedly subjected to high temperatures and loads, such as die casting molds, hot rolling, hot extrusion, and hot forging. It can also be used for cold-work applications on occasion. The most outstanding features are hot strength, tempering resistance, and toughness.

A2 tool steel is an air-hardening, medium-alloy cold-work steel. Primarily used for cold-work applications at room temperature, but also finds use in light-duty hot shearing tools and dies for hot extrusion of zinc. The most outstanding features are wear resistance, dimensional stability, and good toughness.

In the following text, we will compare the two types of steel in various aspects.

Composition

Symbol	H13 Tool Steel1 (%)	A2 Tool Steel (%)
C	0.32 – 0.45	0.95 – 1.05
Cr	4.75 – 5.50	4.75 – 5.50
Mo	1.10 – 1.75	0.90 – 1.40
V	0.80 – 1.20	0.15 – 0.50
Si	0.80 – 1.20	0.50 (Max)
Mn	0.20 – 0.50	1.00 (Max)
P	0.03 (Max)	0.03 (Max)
S	0.03 (Max)	0.03 (Max)

Properties Comparison

1. Wear Resistance. H13 contains vanadium, so it has good wear resistance. A2 has high wear resistance. Its wear resistance comes from high-carbon martensite and fine carbide dispersions.
2. Toughness. H13 has excellent impact strength and good toughness. A2 has high toughness.
3. Hot Hardness (Red Hardness) / Tempering Resistance. H13 is a hot-work steel designed specifically for high-temperature environments, combining red hardness with excellent wear resistance and impact resistance. It resists softening during continuous exposure up to 540 °C (1000 °F). It also has excellent tempering resistance and can maintain high hardness and strength at high temperatures. A2 has good tempering resistance, but its hot hardness is usually insufficient to meet the requirements of high-speed machining or hot working applications. It is not suitable for working conditions where it is exposed to temperatures above 205-260°C (400-500°F) for extended periods.

Heat Treatment

H13 and A2 are both air-hardening steels with deep hardenability. H13 is a secondary hardening steel that requires tempering at a higher temperature (above 510°C or 950°F) to achieve optimal performance, stress relief, and performance stability. A2 tool steel hardness is 61 HRC by tempering at 300°F (150°C) for one hour. For more details, please read H13 tool steel heat treatment and A2 steel heat treatment.

Dimensional Stability

As mentioned above, H13 and A2 are both air-hardening steels, and their advantage is that they maintain excellent dimensional stability.

Surface Treatments

For enhanced surface properties, treatments like nitriding can be applied to both H13 and A2. Nitriding creates a tough surface layer, significantly improving wear resistance and, in some cases, fatigue strength. H13, in particular, benefits greatly from nitriding for applications like die casting dies, where it faces both high temperatures and abrasive wear.

Applications

• H13 Tool Steel Applications: Widely used for general hot-work applications, die-casting dies (for aluminum, zinc, and magnesium), plastic-injection mold tooling, and forging tooling. It’s suitable for hot extrusion dies for aluminum, magnesium, steel, copper, and brass. Also used for punches, piercers, and mandrels for hot work. It can be used as a mold steel for machined cavities and is recommended for highly polished plastic molds after ESR refining, and sometimes employed for highly stressed structural parts in aerospace due to its resistance to softening at elevated temperatures and moderate toughness.
• A2 Tool Steel: A general-purpose air-hardening tool steel with a wide range of tooling applications. Commonly used for blanking and piercing dies in mass production. Also used for cold forming dies, coining dies, drawing and lamination dies, thread rolling dies, shear and slitter blades, and forming rolls. It’s a good choice for intermediate-service cold-work tools and dies. It can be used for small molds and inserts, and is preferred for large dies due to low distortion during heat treatment. Sometimes used as an alternative to hot-work steels for hot shearing tools and dies for hot extrusion of zinc.

Comparison Summary

Characteristic	H13 Tool Steel	A2 Tool Steel
Primary Application	Hot-work applications (e.g., die casting, forging, extrusion).	Cold-work applications (e.g., blanking, forming, drawing).
Wear Resistance	High abrasion resistance. Better than S-series but generally less than D-series. Suitable for long production runs on thin/medium-thickness stock.	High abrasion resistance. Better than S-series but generally less than D-series. Suitable for long production runs on thin/medium-thickness stock.
Toughness	Excellent impact strength and good toughness; high shock resistance makes it preferable for most hot-work operations.	Minimal residual stresses and minimal/no distortion upon air hardening.
Hot Hardness	Very high; maintains high hardness (e.g., ~52 HRC at 540 掳C) and strength at elevated temperatures; excellent tempering resistance (secondary hardening).	Good temper resistance and shows secondary hardening, but not adequate for high-speed machining or hot-work conditions (limited to below 205-260 掳C).
Hardenability	Deep hardening, air-hardening.	Deep hardening, air-hardening.
Dimensional Stability	Minimal residual stresses and minimal/no distortion upon air hardening.	Minimum movement and low distortion in hardening, high safety against cracking.
Machinability	Good in the hardened condition. Annealed rating: 70% compared to 1% carbon steel (W1).2	Easy machining. Annealed rating: 60-65% compared to 1% carbon steel (W1).
Typical Hardness	Normal working hardness for die casting: 44鈥?8 HRC; for shock resistance: 40鈥?4 HRC. Can be heat-treated to over 2070 MPa (300 ksi). As-quenched hardness ~53 HRC.	Normal working hardness: 58-60 HRC. As-quenched hardness ~64 HRC.

In essence, H13 is engineered for severe high-temperature environments, prioritizing hot hardness and strong impact resistance, whereas A2 is a versatile cold-work steel, excelling in wear resistance and dimensional stability for room-temperature operations. If you are having trouble deciding between these two materials, please get in touch with us for professional advice.

1. H13 Steel Composition ↩︎
2. H13 Tool Steel Machinability ↩︎