A2 Tool Steel Hardness Chart and Heat Treatment HRC Guide
A2 tool steel typically has a hardness of 57–62 HRC after hardening and tempering, which is the standard working hardness range for punches, dies, gauges, forming tools, and other cold-work tooling applications. In the annealed condition, A2 is typically supplied at a hardness of about 200–250 HB for machining before heat treatment. After quenching, A2 can reach about 63.5–65 HRC, and with sub-zero or cryogenic treatment, the as-quenched hardness may increase slightly to about 65–66 HRC.
The final hardness selected for A2 depends on the balance between wear resistance and toughness. Higher hardness improves edge retention and abrasion resistance, while lower hardness reduces the risk of chipping and cracking under impact or side loading.
Suprimentos de aço Aobo A2 tool steel round and flat bars in an annealed condition for machining and subsequent heat treatment. If your project requires A2 steel for punches, dies, gauges, or cold-work tooling, you can contact us via [email protected] for bulk supply and size availability.
What Is the Hardness of A2 Tool Steel?
A2 tool steel hardness depends on whether the steel is annealed, as-quenched, cryogenically treated, or tempered for final use.
| A2 Tool Steel Condition | Dureza típica | Meaning |
| Annealed condition | 200–250 HB | Soft enough for machining |
| Properly annealed condition | usually up to about 235 HB | Controlled machinable condition |
| As-quenched condition | 63.5–65 HRC | Very hard but too brittle for normal use |
| As-quenched with sub-zero or cryogenic treatment | 65–66 HRC | Higher hardness due to retained austenite transformation |
| Tempered working condition | 57–62 HRC | Normal practical hardness range |
| Wear-resistance priority | 60–62 HRC | Used for punches, dies, gauges, and wear tools |
| Toughness priority | 56–58 HRC | Used where chipping, shock, or cracking is a concern |
For buyers and toolmakers, the most useful hardness of A2 steel is the final working hardness after tempering.
A2 Tool Steel Hardness by Condition
1. Annealed Condition
A2 tool steel is usually supplied in an annealed condition before machining and final heat treatment. The typical annealed hardness is about 200–250 HB. Many specifications control annealed A2 around 201–229 HB, with upper limits sometimes around 235 HB or 248 HBW, depending on the standard and supply condition.
2. As-Quenched Condition
After austenitizing and quenching, A2 reaches high hardness. The exact as-quenched hardness depends mainly on the hardening temperature.
| Temperatura de austenitização | Typical As-Quenched Hardness |
| 1700°F / 925°C | about 63.5 HRC |
| 1750°F / 955°C | about 64.5 HRC |
| 1775–1800°F / 970–980°C | about 64–65 HRC |
| Sub-zero or cryogenic treatment after quenching | about 65–66 HRC |
Conventional quenching may leave about 16–18% retained austenite in A2. Sub-zero or cryogenic treatment can transform some of this retained austenite into martensite, thereby slightly increasing hardness.
However, as-quenched A2 is highly stressed and brittle. It must be tempered before use.
3. Tempered Working Condition
After tempering, A2 is commonly used at about 57–62 HRC. This is the main working hardness range for industrial tooling.
For blanking dies, punches, gauges, forming tools, and wear-resistant cold-work tooling, 58–62 HRC is common. If the tool is exposed to impact, side loading, or edge chipping, the hardness is often reduced to 56–58 HRC to improve toughness.
A2 Tool Steel Tempering Chart
A2 should be tempered soon after quenching, typically once the part has cooled to about 120–150°F (50–66 °C). Tempering reduces residual stresses, improves toughness, and sets the final hardness. Double tempering is commonly used when dimensional stability is important.
| Condition or Tempering Temperature | Dureza típica |
| As-quenched | 63.5–65 HRC |
| As-quenched with sub-zero or cryogenic treatment | up to about 65–66 HRC |
| 345–350°F / 175°C | about 59.7–63 HRC |
| 400°F / 204°C | about 59.5–60 HRC |
| 400°F / 204°C after cryogenic treatment | about 61–62 HRC |
| 600°F / 315°C | about 55.5 HRC |
| 900°F / 480°C | about 51 HRC |
| 950–1000°F / 510–540°C | about 54–57 HRC |
| 1100°F / 595°C | about 46–47 HRC |
A2 normally loses hardness as the tempering temperature increases. One exception is the secondary hardening range around 950–1000°F / 510–540°C, where fine alloy carbides can raise hardness again to about 54–57 HRC.
For most cold-work tools that require high wear resistance, lower tempering temperatures are used to keep A2 at 58–62 HRC. For tools requiring greater toughness or stability, higher tempering temperatures may be selected, but the final hardness will usually be lower.
How Heat Treatment Controls A2 Tool Steel Hardness
A2 hardness is mainly controlled by austenitizing temperature, quenching rate, retained austenite, section size, and tempering temperature.
| Fator | Effect on A2 Hardness |
| Austenitizing temperature | Controls hardening potential |
| Quenching rate | Controls martensite formation |
| Section size | Affects core hardness |
| Austenita retida | Too much retained austenite lowers hardness and stability |
| Sub-zero or cryogenic treatment | Can slightly increase hardness |
| Temperatura de têmpera | Determines final working HRC |
| Double tempering | Improves stability after retained austenite transformation |
If the austenitizing temperature is too low, A2 may not reach full hardness. If the temperature is too high, excessive retained austenite may reduce hardness and dimensional stability.
A2 is an air-hardening tool steel. Because it contains sufficient chromium and molybdenum to harden deeply, it can achieve high hardness with a lower risk of distortion than oil-hardening grades such as O1.
Section size still matters. A2 can usually harden effectively in solid cross-sections up to about 4.5 inches (114 mm). Above about 5 inches (127 mm), the core may cool too slowly and not reach the same hardness as the surface.
For detailed austenitizing temperatures, tempering cycles, quenching methods, and dimensional stability considerations, see our full Guia de Tratamento Térmico de Aço para Ferramentas A2.
Recommended A2 Tool Steel Hardness for Different Applications
The correct A2 hardness depends on whether the tool requires greater wear resistance or greater toughness.
| Aplicativo | Recommended Hardness | Reason |
| Blanking dies and punches, long runs | 58–62 HRC | Better wear resistance and edge retention |
| Blanking dies and punches, short runs | 58–60 HRC | Resistência ao desgaste e tenacidade equilibradas |
| Piercing and trimming punches | 58–60 HRC | Reduces risk of breakage under side load |
| Matrizes de dobra | 58–60 HRC | Resistência ao desgaste e tenacidade equilibradas |
| Desenho morre | 58–62 HRC | Resists scoring and sliding wear |
| Forming and seaming rolls | 58–62 HRC | Maintains wear resistance and accuracy |
| Cold swaging dies | 56–60 HRC | Better toughness under repeated impact |
| Spinning mandrels | 50–58 HRC | Better ductility under heavy pressure |
| Matrizes de cunhagem | 58–60 HRC | Resists compressive stress |
| Embossing dies and punches | 58–61 HRC | Maintains detail and surface wear resistance |
| Cold extrusion dies and punches | 56–62 HRC | Depends on load and tool design |
| Die bases, anvils, and punch shanks | 56–58 HRC | Better shock absorption |
| Cold shear blades | 58–63 HRC | Durable cutting edge |
| Quills and knockout pins | 59–63 HRC | Resists tip wear and buckling |
| Cold rolling mill rolls | 58–62 HRC | Uniform wear resistance |
| Gages, squares, straight edges, and templates | 58–62 HRC | Wear resistance and dimensional stability |
If an A2 tool chips repeatedly under severe impact service, reducing hardness may help, but only to a point. In heavy shock applications, a tougher grade such as S7 may be a better choice than over-softening A2.
A2 Tool Steel Hardness vs D2 and O1
A2, D2, and O1 can achieve similar HRC values, but they do not perform the same at the same hardness level.
| Grau | Quenching Type | Dureza de trabalho típica | Main Strength | Main Limitation |
| O1 | Oil-hardening | 58–60 HRC | Good toughness and simple heat treatment | Lower wear resistance and higher distortion risk |
| A2 | Endurecimento ao ar | 58–62 HRC | Balanced wear resistance, toughness, and dimensional stability | Not as wear-resistant as D2 |
| D2 | Endurecimento ao ar | 58–62 HRC | Alta resistência ao desgaste | Lower toughness and higher chipping risk |
D2 has higher carbon and chromium content, so it forms harder carbides. This gives D2 better wear resistance but lower toughness. O1 has fewer alloy carbides, so it has lower wear resistance but can offer good toughness in suitable applications.
A2 sits between them. It is tougher than D2 and more dimensionally stable than O1. This is why A2 is often selected when D2 is too brittle, and O1 is not stable or wear-resistant enough.
If you are comparing wear resistance, toughness, and dimensional stability in real tooling applications, you can also read our detailed guides on A2 vs D2 Tool Steel e A2 vs O1 Tool Steel.
Common Problems When A2 Tool Steel Does Not Reach the Required Hardness
When A2 does not reach the expected hardness, the problem is usually related to heat treatment control, section size, or surface condition.
| Problem | Likely Cause | Resultado |
| Low as-quenched hardness | Austenitizing temperature too low | Not enough hardening response |
| Low hardness after high-temperature austenitizing | Excessive retained austenite | Soft retained austenite lowers measured hardness |
| Soft surface but hard core | Descarbonetação | Surface carbon loss prevents full surface hardness |
| Soft core in large section | Cooling rate too slow | Core may not fully transform to martensite |
| Final hardness too low | Tempering temperature too high | Martensite is over-softened |
| Local soft spots after grinding | Grinding burn or overtempering | Surface hardness becomes uneven |
A common mistake is assuming that a higher austenitizing temperature always means higher hardness. In A2, overheating can increase retained austenite and reduce final hardness.
Surface decarburization is another common cause. If A2 is heated without proper protection, the surface may lose carbon. The core may reach the correct hardness, but the surface remains soft.
Large section size can also cause hardness problems. A2 has good deep-hardening ability, but very large sections may still cool too slowly at the center. Above about 5 inches (127 mm), core hardness may be lower than surface hardness under still-air cooling.
Improper tempering can also reduce hardness. If the tempering temperature is too high for the target hardness, the final HRC will be lower. If grinding after heat treatment generates excessive heat, it may create local soft zones or uneven surface hardness.
For bulk A2 tool steel supply, size availability, export quotation, or technical support, please visit our A2 tool steel product page or contact us at [email protected].
Perguntas frequentes
A2 tool steel is usually supplied in an annealed condition at about 200–250 HB. After hardening and tempering, it is commonly used around 57–62 HRC. In the as-quenched condition, A2 can reach about 63.5–65 HRC, but it must be tempered before normal use.
The practical Rockwell C hardness of A2 steel is usually about 58–62 HRC after hardening and tempering. The exact value depends on austenitizing temperature, tempering temperature, section size, and sub-zero treatment.
A2 tool steel can reach about 63.5–65 HRC as-quenched. With sub-zero or cryogenic treatment after quenching, hardness may rise to about 65–66 HRC.
A2 punches and dies are commonly used around 58–62 HRC. For long production runs and wear resistance, 60–62 HRC is often selected. For impact or chipping risk, 56–60 HRC may be safer.
Common causes include low austenitizing temperature, overheating and retained austenite, slow cooling in large sections, surface decarburization, overtempering, or grinding burn.