Steel A8 Stress Relieved
Heat-treated state
AISI/SAE A8 · UNS T30108
Intermediate step for large or asymmetric dies to minimise distortion during air hardening.
Values for the Stress Relieved condition
Other A8 tempers and conditions
A8 is listed in 6 conditions; see the grade overview at A8.
- Annealed
- Stress Relieved
- H&T 56-58 HRC
- Q&T
- H&T 58-60 HRC
- H&T 60-62 HRC
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault soft, as-supplied bar/plate | Standard stock condition for machining dies and inserts before hardening. | 500 | 780 | 18 | 220 HB | — |
Stress RelievedThis page rough-machined and stress relieved at 650–700 °C | Intermediate step for large or asymmetric dies to minimise distortion during air hardening. | 510 | 790 | 17 | 19 HRC | 2.9 % IACS |
High-temper, maximum-toughness condition | Pick for heavy shear blades, thick-section punches and impact-loaded dies where chipping is the failure mode. | 1,600 | 1,900 | — | 57 HRC | — |
Quenched and tempered | General working condition: good balance of toughness and wear for blanking and forming tools. | 1,700 | 2,000 | 2 | 59 HRC | — |
Standard die working hardness | The usual compromise between wear resistance and toughness for blanking and forming dies. | 1,700 | 2,000 | — | 59 HRC | — |
Low-temper, maximum-wear condition | Choose for thin-stock blanking punches and wear inserts where abrasion, not impact, dominates. | 1,850 | 2,150 | — | 61 HRC | — |
What is A8 Stress Relieved?
A8 Stress Relieved is A8 heat treated to Stress Relieved — intermediate step for large or asymmetric dies to minimise distortion during air hardening. A8 Stress Relieved has a yield strength of 510 MPa (74 ksi) and a tensile strength of 790 MPa (115 ksi) — stronger than 65% of steel grades. Elongation at break is 17% and the elastic modulus is 207 GPa (30 Msi). A8 Stress Relieved has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,420°C (2,588 °F). Annealed is the default condition FabDigit quotes; Stress Relieved is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Low electrical conductivity — 2.9 % IACS, worse than 93% of steel grades
- Poor heat conductor — 24.5 W/m·K (14.2 BTU/hr·ft·°F), worse than 89% of steel grades
- High embodied carbon — 2.6 kg CO₂/kg, worse than 87% of steel grades
- Limited formability — 19/100, worse than 84% of steel grades
A8 Stress Relieved properties
Typical room-temperature values for A8 Stress Relieved; 23 are specific to this condition. Other listed values are A8 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A8 Stress Relieved has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical13
A8 Stress Relieved has a yield strength of 510 MPa (74 ksi) and a tensile strength of 790 MPa (115 ksi) — stronger than 65% of steel grades. Elongation at break is 17% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
A8 Stress Relieved is rated for continuous service to 200°C (392 °F). It conducts heat at 24.5 W/m·K (14.2 BTU/hr·ft·°F), worse than 89% of steel grades. Thermal expansion is 12.4 µm/m·K (6.89 µin/in·°F).
Electrical3
A8 Stress Relieved conducts electricity at 2.9 % IACS, worse than 93% of steel grades.
Chemical & Environmental2
Corrosion resistance is poor (20/100), better than 87% of steel grades.
Sustainability4
Producing a kilogram of A8 Stress Relieved takes about 34 MJ of energy and emits 2.6 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 40%.
Manufacturability7
A8 Stress Relieved's machinability is fair (44/100, worse than 71% of steel grades); weldability poor (22/100); formability poor (19/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A8 Stress Relieved
Is A8 easy to machine?
Machine only in the annealed state (~220 HB) with rigid setups and coated carbide; after hardening use grinding or EDM plus a stress-relief temper.
Can A8 be welded?
Weld only for repair — preheat 300–370 °C, use matched 5 % Cr tool-steel filler, keep interpass temperature and temper immediately below the last tempering temperature.
Can A8 be formed, bent or molded?
Hot work at 1050–900 °C followed by slow cooling; no meaningful cold forming — air harden from 980–1010 °C with minimal size change and double temper at 200–540 °C.
What surface finishes work on A8?
Takes a good ground/lapped finish; protect with oil, black oxide, nitriding or PVD TiN/CrN coatings since the 5 % Cr gives no stainless behaviour.
A8 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 0.5 – 0.6 | 0.55 |
| Mn | 0.2 – 0.5 | 0.35 |
| Si | 0.75 – 1.1 | 0.95 |
| Cr | 4.75 – 5.5 | 5.1 |
| Mo | 1.15 – 1.65 | 1.3 |
| W | 1 – 1.5 | 1.25 |
| Voptional/residual per ASTM A681 | ≤ 0.25 | 0.2 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
A8 Stress Relieved — frequently asked
What is A8 Stress Relieved used for?
A8 Stress Relieved is typically used for cold-work blanking and forming dies, slitter knives, shear blades, punches and die inserts, trim and pierce tooling and cold-forming die inserts for shock loading. In short: air-hardening tool steel.
What is the yield strength of A8 Stress Relieved?
A8 Stress Relieved has a typical yield strength of 510 MPa (74 ksi) and a tensile strength of 790 MPa (115 ksi) — stronger than 65% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is A8 Stress Relieved easy to machine?
Not especially — machinability is rated fair (44/100, worse than 71% of steel grades). Machine only in the annealed state (~220 HB) with rigid setups and coated carbide; after hardening use grinding or EDM plus a stress-relief temper.
Can A8 Stress Relieved be welded?
Not readily — weldability is rated poor (22/100). Weld only for repair — preheat 300–370 °C, use matched 5 % Cr tool-steel filler, keep interpass temperature and temper immediately below the last tempering temperature.
What surface finishes work on A8 Stress Relieved?
Takes a good ground/lapped finish; protect with oil, black oxide, nitriding or PVD TiN/CrN coatings since the 5 % Cr gives no stainless behaviour.
Can A8 Stress Relieved be formed, bent or molded?
Hot work at 1050–900 °C followed by slow cooling; no meaningful cold forming — air harden from 980–1010 °C with minimal size change and double temper at 200–540 °C.
What is the maximum service temperature of A8 Stress Relieved?
A8 Stress Relieved is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in A8 Stress Relieved?
Yes — A8 Stress Relieved is available for CNC machining; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A681 — Standard Specification for Tool Steels Alloy — ASTM International (2022)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Tool Steels) — ASM International (1990)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
- A8 air-hardening cold-work tool steel datasheet — Tool-steel producers (Crucible/Latrobe/Böhler-type data) (2020)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.