Stainless Steel 309Cb Annealed
Temper · default condition
UNS S30940
Standard mill condition for plate, sheet, bar, pipe and fittings; maximum ductility and corrosion resistance.
Values for the Annealed 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 |
|---|---|---|---|---|---|---|
AnnealedDefaultThis page 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 | — |
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 Annealed?
309Cb Annealed is 309Cb in the Annealed temper — standard mill condition for plate, sheet, bar, pipe and fittings; maximum ductility and corrosion resistance. 309Cb Annealed has a yield strength of 310 MPa (45 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 63% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 200 GPa (29 Msi). 309Cb Annealed 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).
Advantages
- High service temperature — 1,000°C (1,832 °F), better than 88% of stainless steel grades
- Readily welded — 80/100, better than 80% of stainless steel grades
- Ductile — tolerates forming and impact — 45%, better than 76% of stainless steel grades
309Cb Annealed properties
Typical room-temperature values for 309Cb Annealed; 12 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 Annealed 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 Annealed has a yield strength of 310 MPa (45 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 63% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
309Cb Annealed is rated for continuous service to 1,000°C (1,832 °F). It conducts heat at 15.6 W/m·K (9.01 BTU/hr·ft·°F), better than 55% of stainless steel grades. Thermal expansion is 14.9 µm/m·K (8.28 µin/in·°F).
Electrical3
309Cb Annealed conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (66/100), better than 59% of stainless steel grades.
Sustainability4
Producing a kilogram of 309Cb Annealed 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 Annealed's machinability is fair (38/100, better than 63% of stainless steel grades); weldability very good (80/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 309Cb Annealed
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 Annealed — frequently asked
What is 309Cb Annealed used for?
309Cb Annealed 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 Annealed?
309Cb Annealed has a typical yield strength of 310 MPa (45 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 63% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is 309Cb Annealed easy to machine?
Not especially — machinability is rated fair (38/100, better than 63% 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 Annealed 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 Annealed?
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 Annealed 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 Annealed?
309Cb Annealed is rated for continuous use to about 1,000°C (1,832 °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.