Steel A9
AISI/SAE A9 · UNS T30109
A9 (T30109) is a nickel-modified, air-hardening cold-work tool steel developed to combine the shock resistance of the S-series steels with the dimensional stability of the A-series.
Reference datasheet — A9 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the ANN condition
A9 tempers and conditions
A9 is supplied in 4 conditions, soft to hard. ANN is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard mill supply condition for machining tool blanks before hardening. | 400 | 745 | 22 | 220 HB | — |
Hardened & tempered 44–48 HRC | Air-harden ~980–1010 °C, double temper ~590–620 °C when impact loading dominates over wear. | 1,300 | 1,500 | 8 | 46 HRC | — |
Hardened & tempered 50–52 HRC | Common working hardness for cold forming punches and heavy blanking dies with shock loading. | 1,550 | 1,750 | 5 | 51 HRC | — |
Hardened & secondary-hardened 54–56 HRC | Air quench ~1010 °C and double temper near 510–540 °C (secondary hardening peak) for abrasive cold-work tooling. | 1,750 | 1,950 | 3 | 55 HRC | — |
What is A9?
A9 (T30109) is a nickel-modified, air-hardening cold-work tool steel developed to combine the shock resistance of the S-series steels with the dimensional stability of the A-series. It is supplied annealed at about 220 HB (400 MPa yield, 745 MPa tensile, 22 % elongation, 200 GPa modulus) and air hardened from 980–1010 °C to 44–56 HRC for tooling that sees impact rather than pure abrasion. Tempering resistance is modest, with service around 200 °C, and weldability (30), formability (25) and corrosion resistance (18) are all low. Where wear resistance outweighs toughness, A2 or D2 are the usual alternatives. A9 has a density of 7.78 g/cm³ (0.281 lb/in³), lighter than 91% of steel grades. It melts at 1,420°C (2,588 °F). A9 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 745 MPa (108 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 200 GPa (29 Msi).
What is A9 used for?
- die inserts subject to impact
- cold forming dies
- punches
- trim tools
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 W/m·K (13.9 BTU/hr·ft·°F), worse than 90% of steel grades
- High embodied carbon — 2.7 kg CO₂/kg, worse than 89% of steel grades
A9 properties
Typical room-temperature values for A9-ANN; bars are the position among steel grades.
Physical3
A9 has a density of 7.78 g/cm³ (0.281 lb/in³), lighter than 91% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical15
A9 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 745 MPa (108 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
A9 is rated for continuous service to 200°C (392 °F). It conducts heat at 24 W/m·K (13.9 BTU/hr·ft·°F), worse than 90% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
A9 conducts electricity at 2.9 % IACS, worse than 93% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (18/100), better than 83% of steel grades.
Sustainability4
Producing a kilogram of A9 takes about 35 MJ of energy and emits 2.7 kg of CO₂ — more than 87% of steel grades. Typical recycled content is 45%.
Manufacturability8
A9's machinability is good (55/100, better than 62% of steel grades); weldability poor (30/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. A9 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A9
Is A9 easy to machine?
Machine in the annealed condition (~220 HB) with rigid setups and carbide tooling; vanadium carbides are abrasive, and above ~45 HRC only grinding or EDM is practical.
Can A9 be welded?
Repair-weld only: preheat 200–300 °C, use matching 5%Cr/Mo filler or Ni-base, keep interpass warm and temper immediately below the last tempering temperature.
Can A9 be formed, bent or molded?
Hot work at 1040–1120 °C and cool slowly; cold forming is limited to mild straightening in the annealed state — air hardening from 980–1010 °C gives minimal size change.
A9 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 | 0.45 – 0.55 | 0.5 |
| Mn | 0.2 – 0.8 | 0.5 |
| Siraises tempering resistance | 0.95 – 1.15 | 1.05 |
| Cr | 4.75 – 5.5 | 5.1 |
| Nitoughness / hardenability addition | 1.25 – 1.75 | 1.5 |
| Mosecondary hardening | 1.3 – 1.8 | 1.5 |
| Vgrain refinement, wear carbides | 0.8 – 1.4 | 1 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on A9?
Stress relieve before finish grinding; nitriding, black oxide or PVD (TiN/CrN, deposited below the temper temperature) are used for wear and rust protection — no anodizing.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel A9 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- T30109
How much does A9 cost?
A9 is a high-cost steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
A9 — frequently asked
What is A9 used for?
A9 is typically used for die inserts subject to impact, cold forming dies, punches and trim tools. In short: tough air-hardening cold-work steel; S-series toughness, A-series stability; low distortion on hardening.
What is the yield strength of A9?
A9 has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 745 MPa (108 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A9 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machine in the annealed condition (~220 HB) with rigid setups and carbide tooling; vanadium carbides are abrasive, and above ~45 HRC only grinding or EDM is practical.
Can A9 be welded?
Not readily — weldability is rated poor (30/100). Repair-weld only: preheat 200–300 °C, use matching 5%Cr/Mo filler or Ni-base, keep interpass warm and temper immediately below the last tempering temperature.
What surface finishes work on A9?
Stress relieve before finish grinding; nitriding, black oxide or PVD (TiN/CrN, deposited below the temper temperature) are used for wear and rust protection — no anodizing.
Can A9 be formed, bent or molded?
Hot work at 1040–1120 °C and cool slowly; cold forming is limited to mild straightening in the annealed state — air hardening from 980–1010 °C gives minimal size change.
What is the maximum service temperature of A9?
A9 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does A9 cost?
A9 is a high-cost steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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 Edition (Roberts, Krauss, Kennedy) — ASM International (1998)
- UNS T30109 alloy record — SAE/ASTM Metals & Alloys in the Unified Numbering System (2017)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.