Stainless Steel 309Cb-AW (As-welded deposit)
Heat-treated state
UNS S30940
Condition of dissimilar-metal joints and stainless overlays on carbon/low-alloy steel; Nb stabilization is what lets the joint go into service unannealed.
Values for the AW condition
Other 309Cb tempers and conditions
309Cb is listed in 5 conditions; see the grade overview at 309Cb.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault solution annealed (1040–1120 °C, rapid cool) | Standard mill condition for plate, sheet, bar, pipe and fittings; maximum ductility and corrosion resistance. | 310 | 620 | 45 | 165 HB | — |
AWThis page As-welded deposit | Condition of dissimilar-metal joints and stainless overlays on carbon/low-alloy steel; Nb stabilization is what lets the joint go into service unannealed. | 400 | 590 | 32 | 180 HB | 2.2 % IACS |
Cold drawn | Use for machined shafts, bolting and fixture pins where tighter tolerance and higher yield are wanted. | 480 | 720 | 30 | 15 HRC | 2.2 % IACS |
Quarter hard | Special-order strip/sheet temper when higher room-temperature strength is needed and forming demands are mild. | 515 | 860 | 20 | 25 HRC | 2.2 % IACS |
Half hard | Rarely stocked; only for flat springs/clips where strength outweighs formability and no hot service is involved. | 760 | 1,035 | 10 | 32 HRC | 2.2 % IACS |
What is 309Cb-AW?
309Cb-AW is 309Cb heat treated to AW — condition of dissimilar-metal joints and stainless overlays on carbon/low-alloy steel; Nb stabilization is what lets the joint go into service unannealed. 309Cb-AW has a yield strength of 400 MPa (58 ksi) and a tensile strength of 590 MPa (85.6 ksi) — stronger than 57% of stainless steel grades. Elongation at break is 32% and the elastic modulus is 198 GPa (28.7 Msi). 309Cb-AW has a density of 7.98 g/cm³ (0.288 lb/in³), heavier than 85% of stainless steel grades. It melts at 1,400°C (2,552 °F). Annealed is the default condition FabDigit quotes; AW is available on request or by drawing note.
Advantages
- High service temperature — 900°C (1,652 °F), better than 85% of stainless steel grades
- Readily welded — 80/100, better than 80% of stainless steel grades
309Cb-AW properties
Typical room-temperature values for 309Cb-AW; 23 are specific to this condition. Other listed values are 309Cb reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
309Cb-AW has a density of 7.98 g/cm³ (0.288 lb/in³), heavier than 85% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
309Cb-AW has a yield strength of 400 MPa (58 ksi) and a tensile strength of 590 MPa (85.6 ksi) — stronger than 57% of stainless steel grades. Elongation at break is 32% and the elastic modulus is 198 GPa (28.7 Msi).
Thermal6
309Cb-AW is rated for continuous service to 900°C (1,652 °F). It conducts heat at 15.2 W/m·K (8.78 BTU/hr·ft·°F), better than 51% of stainless steel grades. Thermal expansion is 14.9 µm/m·K (8.28 µin/in·°F).
Electrical3
309Cb-AW conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (63/100), better than 53% of stainless steel grades.
Sustainability4
Producing a kilogram of 309Cb-AW takes about 60 MJ of energy and emits 4.8 kg of CO₂ — more than 70% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
309Cb-AW's machinability is poor (34/100, worse than 55% of stainless steel grades); weldability very good (80/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 309Cb-AW
Is 309Cb easy to machine?
Machine like 310: rigid setups, positive-rake sharp carbide, heavy feeds at low-to-moderate speed (~25–40 % of 1212 rates), flood coolant, and avoid dwelling — the alloy work-hardens fast and Nb carbides are abrasive.
Can 309Cb be welded?
Readily welded by GTAW/GMAW/SMAW with matching 309Cb, ER309LNb or 309L filler; no post-weld anneal is required thanks to Nb stabilization, but keep interpass temperature low and avoid long holds at 700–850 °C to limit sigma phase.
Can 309Cb be formed, bent or molded?
Cold forms and roll-bends well but needs about 50 % more press force than carbon steel with large springback; hot work at 1150–1200 °C and finish above 950 °C, then solution anneal at 1040–1120 °C with rapid cooling.
What surface finishes work on 309Cb?
Pickle and passivate (ASTM A967) or grit-blast plus acid clean after hot forming; can be ground, brushed or electropolished — anodizing does not apply, and high-temperature service will grow a tight dark oxide scale.
309Cb 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 |
|---|---|---|
| CNb is set at ≥10×C | ≤ 0.08 | 0.06 |
| Si | ≤ 1 | 0.6 |
| Mn | ≤ 2 | 1.5 |
| P | ≤ 0.05 | — |
| S | ≤ 0.03 | — |
| Cr | 22 – 24 | 23 |
| Ni | 12 – 15 | 13.5 |
| NbNb+Ta, minimum 10×C (stabilizer) | ≤ 1.1 | 0.8 |
| Nreported when specified | ≤ 0.1 | — |
| Fe | balance | — |
309Cb-AW — frequently asked
What is 309Cb-AW used for?
309Cb-AW is typically used for high-temperature welded assemblies, furnace components and heat exchanger tubing. In short: nb-stabilized 309; sensitization-free after welding; 1000 °C service ceiling.
What is the yield strength of 309Cb-AW?
309Cb-AW has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 590 MPa (85.6 ksi) — stronger than 57% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is 309Cb-AW easy to machine?
Not especially — machinability is rated poor (34/100, worse than 55% of stainless steel grades). Machine like 310: rigid setups, positive-rake sharp carbide, heavy feeds at low-to-moderate speed (~25–40 % of 1212 rates), flood coolant, and avoid dwelling — the alloy work-hardens fast and Nb carbides are abrasive.
Can 309Cb-AW be welded?
Yes — weldability is rated very good (80/100). Readily welded by GTAW/GMAW/SMAW with matching 309Cb, ER309LNb or 309L filler; no post-weld anneal is required thanks to Nb stabilization, but keep interpass temperature low and avoid long holds at 700–850 °C to limit sigma phase.
What surface finishes work on 309Cb-AW?
Pickle and passivate (ASTM A967) or grit-blast plus acid clean after hot forming; can be ground, brushed or electropolished — anodizing does not apply, and high-temperature service will grow a tight dark oxide scale.
Can 309Cb-AW be formed, bent or molded?
Cold forms and roll-bends well but needs about 50 % more press force than carbon steel with large springback; hot work at 1150–1200 °C and finish above 950 °C, then solution anneal at 1040–1120 °C with rapid cooling.
What is the maximum service temperature of 309Cb-AW?
309Cb-AW is rated for continuous use to about 900°C (1,652 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 309Cb Annealed and 309Cb-CD?
Annealed is the default condition — standard mill condition for plate, sheet, bar, pipe and fittings; maximum ductility and corrosion resistance. CD: use for machined shafts, bolting and fixture pins where tighter tolerance and higher yield are wanted. Yield strength is 310 MPa in Annealed versus 480 MPa in CD.
Sources
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip (S30940) — ASTM International (2023)
- ASTM A479/A479M — Stainless Steel Bars and Shapes for Boilers and Pressure Vessels — ASTM International (2021)
- ASTM A312/A312M — Seamless, Welded and Heavily Cold Worked Austenitic Stainless Steel Pipes — ASTM International (2022)
- AWS A5.9 / A5.4 — Bare and Covered Corrosion-Resisting Chromium-Nickel Electrodes (309Cb/309LNb) — American Welding Society (2017)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
- 309/309S/309Cb heat-resisting stainless product data — Cleveland-Cliffs (AK Steel) / Outokumpu (2021)
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.