Stainless Steel 1.4309-AT
Precip hard · default condition
EN 1.4309 · UNS J92500 · ASTM CF3
AT = solution annealed ~1050 °C and water quenched
Default and virtually the only shipped condition — restores full corrosion resistance and ductility after casting.
Values for the AT condition
Other 1.4309 tempers and conditions
1.4309 is listed in 4 conditions; see the grade overview at 1.4309.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Only for non-critical, non-corrosive duty or as an intermediate state before machining and heat treatment. | 245 | 500 | 40 | 150 HB | 2.3 % IACS |
ATDefaultThis page Solution annealed ~1050 °C and water quenched | Default and virtually the only shipped condition — restores full corrosion resistance and ductility after casting. | 250 | 520 | 55 | 140 HB | — |
hot isostatically pressed then solution annealed | Choose for pressure-tight, radiographically clean valve/pump bodies and cryogenic parts where porosity must be closed. | 255 | 535 | 60 | 140 HB | 2.4 % IACS |
centrifugally cast, solution annealed (ASTM A451/A452 style) | Pick for tubes, sleeves and rings where the fine, dense centrifugal structure gives slightly higher strength and soundness. | 265 | 545 | 50 | 150 HB | 2.3 % IACS |
What is 1.4309-AT?
1.4309-AT is 1.4309 in the AT condition — default and virtually the only shipped condition — restores full corrosion resistance and ductility after casting. 1.4309-AT has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 91% of stainless steel grades. Elongation at break is 55% and the elastic modulus is 195 GPa (28.3 Msi). 1.4309-AT has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Advantages
- Readily welded — 92/100, better than 98% of stainless steel grades
- Ductile — tolerates forming and impact — 55%, better than 97% of stainless steel grades
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% of stainless steel grades
Limitations
- Low strength — 250 MPa (36.3 ksi), worse than 91% of stainless steel grades
- Hard to polish — 60/100, worse than 80% of stainless steel grades
1.4309-AT properties
Typical room-temperature values for 1.4309-AT; 11 are specific to this condition. Other listed values are 1.4309 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
1.4309-AT has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical16
1.4309-AT has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 91% of stainless steel grades. Elongation at break is 55% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
1.4309-AT is rated for continuous service to 425°C (797 °F). It conducts heat at 16.2 W/m·K (9.36 BTU/hr·ft·°F), better than 64% of stainless steel grades. Thermal expansion is 16.5 µm/m·K (9.17 µin/in·°F).
Electrical3
1.4309-AT conducts electricity at 2.3 % IACS, better than 55% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), worse than 52% of stainless steel grades.
Sustainability4
Producing a kilogram of 1.4309-AT takes about 55 MJ of energy and emits 4.8 kg of CO₂ — more than 50% of stainless steel grades. Typical recycled content is 75%.
Manufacturability7
1.4309-AT's machinability is fair (42/100, better than 79% of stainless steel grades); weldability excellent (92/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 1.4309-AT
Is 1.4309 easy to machine?
Gummy and work-hardening — use sharp positive-rake carbide, rigid setups, heavy positive feed, ~40 % of 1212 speeds and copious coolant; avoid dwelling in the cut.
Can 1.4309 be welded?
Excellent — GTAW/SMAW with ER308L/E308L filler, no preheat and no PWHT required; keep interpass <150 °C and maintain 5–15 FN ferrite to avoid hot cracking.
Can 1.4309 be formed, bent or molded?
Sand or investment cast with generous feeding (long freezing range, ~2.3 % solidification shrinkage); solution anneal at 1040–1100 °C and water quench after casting or weld repair.
What surface finishes work on 1.4309?
Pickle and passivate (ASTM A967) or electropolish; not anodisable — bead blasting, grinding and mechanical polish are limited by casting skin and micro-porosity.
1.4309 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 |
|---|---|---|
| Cextra-low carbon, key to intergranular corrosion resistance | ≤ 0.03 | 0.02 |
| SiEN 10283 ≤1.5; ASTM A351 CF3 allows ≤2.00 | ≤ 1.5 | 1 |
| MnASTM CF3 ≤1.50 | ≤ 1.5 | 1 |
| P | ≤ 0.04 | 0.03 |
| SASTM A351 CF3 ≤0.040 | ≤ 0.03 | 0.02 |
| CrASTM CF3 range 17.0–21.0 | 18 – 20 | 19 |
| NiASTM CF3 range 8.0–12.0 | 9 – 12 | 10.5 |
| Moresidual only | ≤ 0.5 | 0.2 |
| Nresidual/optional; higher N raises yield | ≤ 0.2 | 0.05 |
| Fe | balance | — |
1.4309-AT — frequently asked
What is 1.4309-AT used for?
1.4309-AT is typically used for welded pump/valve castings, food and pharmaceutical equipment and cryogenic fittings. In short: best as-welded corrosion resistance; extra-low-carbon cast 304L; good cryogenic toughness.
What is the yield strength of 1.4309-AT?
1.4309-AT has a typical yield strength of 250 MPa (36.3 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 91% of stainless steel grades. Strength varies by condition: see the 4 listed tempers.
Is 1.4309-AT easy to machine?
Not especially — machinability is rated fair (42/100, better than 79% of stainless steel grades). Gummy and work-hardening — use sharp positive-rake carbide, rigid setups, heavy positive feed, ~40 % of 1212 speeds and copious coolant; avoid dwelling in the cut.
Can 1.4309-AT be welded?
Yes — weldability is rated excellent (92/100). Excellent — GTAW/SMAW with ER308L/E308L filler, no preheat and no PWHT required; keep interpass <150 °C and maintain 5–15 FN ferrite to avoid hot cracking.
What surface finishes work on 1.4309-AT?
Pickle and passivate (ASTM A967) or electropolish; not anodisable — bead blasting, grinding and mechanical polish are limited by casting skin and micro-porosity.
Can 1.4309-AT be formed, bent or molded?
Sand or investment cast with generous feeding (long freezing range, ~2.3 % solidification shrinkage); solution anneal at 1040–1100 °C and water quench after casting or weld repair.
What is the maximum service temperature of 1.4309-AT?
1.4309-AT is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 1.4309-AT and 1.4309-F?
AT is the default condition — default and virtually the only shipped condition — restores full corrosion resistance and ductility after casting. F: only for non-critical, non-corrosive duty or as an intermediate state before machining and heat treatment. Yield strength is 250 MPa in AT versus 245 MPa in F.
Sources
- EN 10283 — Corrosion resistant steel castings (GX2CrNi19-11, 1.4309) — CEN (2010)
- ASTM A351/A351M — Castings, Austenitic, for Pressure-Containing Parts (CF3) — ASTM (2018)
- ASTM A743/A743M — Castings, Iron-Chromium-Nickel, Corrosion Resistant (CF3) — ASTM (2019)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Cast Stainless Steels) — ASM International (1990)
- Steel Castings Handbook, 6th ed. — Steel Founders' Society of America / ASM (1995)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
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.