Stainless Steel 310Cb
UNS S31040
AISI 310Cb (UNS S31040) is a niobium-stabilized 25Cr-20Ni austenitic stainless; the niobium ties up carbon so the alloy resists intergranular attack after long high-temperature exposure.
Reference datasheet — 310Cb 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 Annealed condition
310Cb tempers and conditions
310Cb is supplied in 4 conditions, soft to hard. Annealed 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 |
|---|---|---|---|---|---|---|
Stabilize annealed | Use when maximum immunity to intergranular attack/polythionic-acid cracking after service or welding is required, by tying carbon up as NbC. | 305 | 610 | 42 | 165 HB | 2.2 % IACS |
AnnealedDefault Annealed (solution annealed, 1050–1120 °C, rapid cool) | Standard stocked condition for plate, sheet, bar and pipe; maximum ductility and corrosion/oxidation resistance. | 310 | 620 | 45 | 160 HB | — |
As-welded deposit | Reference condition for welded pipe and fabrications used without post-weld solution anneal — the reason 310Cb exists. | 330 | 600 | 35 | 180 HB | 2.2 % IACS |
Cold drawn | Pick for machined fasteners, pins and shafts needing higher yield and better surface/tolerance than hot-finished bar. | 550 | 760 | 25 | 21 HRC | — |
Supply forms, finishes and certifications
Ways 310Cb is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
2B | Cold rolled, annealed, pickled and lightly skin-passed sheet | Surface finish |
HRAP | Hot rolled, annealed and pickled plate | Surface finish |
What is 310Cb?
AISI 310Cb (UNS S31040) is a niobium-stabilized 25Cr-20Ni austenitic stainless; the niobium ties up carbon so the alloy resists intergranular attack after long high-temperature exposure. It is used for welded furnace assemblies and hot-gas structures operating to 1100 °C and is supplied annealed, hot-rolled and pickled, 2B, cold-drawn, stabilization-annealed and as-welded. Annealed strength is about 310 MPa yield and 620 MPa tensile with 45 % elongation and 160 HB. Nb carbides shorten tool life and the fully austenitic weld metal is hot-crack sensitive; unstabilized 310S is cheaper and more widely stocked. 310Cb 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). 310Cb 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).
What is 310Cb used for?
- Furnace components and hangers
- Welded high-temperature ducting
- Radiant tubes
- Heat-treating fixtures
- Recuperator sections
- Flue and stack liners
- Burner components
Advantages
- High service temperature — 1,100°C (2,012 °F), better than 96% of stainless steel grades
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% of stainless steel grades
- Forms and bends easily — 70/100, better than 79% of stainless steel grades
- Ductile — tolerates forming and impact — 45%, better than 76% of stainless steel grades
Limitations
- High embodied carbon — 6 kg CO₂/kg, worse than 88% of stainless steel grades
310Cb properties
Typical room-temperature values for 310Cb-Annealed; bars are the position among stainless steel grades.
Physical3
310Cb 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
310Cb 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
310Cb is rated for continuous service to 1,100°C (2,012 °F). It conducts heat at 14.2 W/m·K (8.2 BTU/hr·ft·°F), worse than 76% of stainless steel grades. Thermal expansion is 15.9 µm/m·K (8.83 µin/in·°F).
Electrical3
310Cb conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (68/100), better than 63% of stainless steel grades.
Sustainability4
Producing a kilogram of 310Cb takes about 80 MJ of energy and emits 6 kg of CO₂ — more than 89% of stainless steel grades. Typical recycled content is 70%.
Manufacturability7
310Cb's machinability is poor (30/100, worse than 70% of stainless steel grades); weldability very good (75/100); formability very good (70/100).
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 stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. 310Cb is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 310Cb
Is 310Cb easy to machine?
Gummy and strongly work-hardening: use rigid setups, positive-rake carbide, 25–60 m/min, heavy constant feed, no dwell, flood coolant; Nb carbides accelerate edge wear.
Can 310Cb be welded?
Weld with GTAW/GMAW/SMAW using matching 310Cb/ER310 or Nb-stabilized filler, low heat input, no preheat, interpass below ~150 °C; stabilization means no post-weld solution anneal is normally needed, but watch hot cracking from fully austenitic structure.
Can 310Cb be formed, bent or molded?
Cold forms well but needs ~50 % more press force than 304 and generous bend radii due to high work-hardening and springback; hot work 1150–1200 °C, finish above 950 °C, then solution anneal.
310Cb 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 stabilization ties up carbon as NbC | ≤ 0.08 | 0.05 |
| Mn | ≤ 2 | 1.5 |
| Sisome specs limit to 0.75 max | ≤ 1.5 | 0.8 |
| P | ≤ 0.05 | — |
| S | ≤ 0.03 | — |
| Cr | 24 – 26 | 25 |
| Ni | 19 – 22 | 20.5 |
| NbNb (+Ta) stabilizer; historically written as Cb | 0.75 – 1.5 | 1 |
| Fe | balance | — |
What surface finishes work on 310Cb?
Pickle and passivate or electropolish after fabrication to restore the chromium oxide film; no anodizing — descale heat tint with acid paste or abrasive blast plus passivation.
Surface treatments FabDigit runs on stainless 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).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel 310Cb in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S31040
How much does 310Cb cost?
310Cb is a premium-cost stainless steel ($$$), cheaper than about 51% 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.
310Cb — frequently asked
What is 310Cb used for?
310Cb is typically used for furnace components and hangers, welded high-temperature ducting, radiant tubes, heat-treating fixtures, recuperator sections and flue and stack liners. In short: stabilized 310 for welding; resists post-service sensitization; 1100 °C furnace grade.
What is the yield strength of 310Cb?
310Cb 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 4 listed tempers.
Is 310Cb easy to machine?
Not especially — machinability is rated poor (30/100, worse than 70% of stainless steel grades). Gummy and strongly work-hardening: use rigid setups, positive-rake carbide, 25–60 m/min, heavy constant feed, no dwell, flood coolant; Nb carbides accelerate edge wear.
Can 310Cb be welded?
Yes — weldability is rated very good (75/100). Weld with GTAW/GMAW/SMAW using matching 310Cb/ER310 or Nb-stabilized filler, low heat input, no preheat, interpass below ~150 °C; stabilization means no post-weld solution anneal is normally needed, but watch hot cracking from fully austenitic structure.
What surface finishes work on 310Cb?
Pickle and passivate or electropolish after fabrication to restore the chromium oxide film; no anodizing — descale heat tint with acid paste or abrasive blast plus passivation.
Can 310Cb be formed, bent or molded?
Cold forms well but needs ~50 % more press force than 304 and generous bend radii due to high work-hardening and springback; hot work 1150–1200 °C, finish above 950 °C, then solution anneal.
What is the maximum service temperature of 310Cb?
310Cb is rated for continuous use to about 1,100°C (2,012 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 310Cb Annealed and 310Cb-CD?
Annealed is the default condition — standard stocked condition for plate, sheet, bar and pipe; maximum ductility and corrosion/oxidation resistance. CD: pick for machined fasteners, pins and shafts needing higher yield and better surface/tolerance than hot-finished bar. Yield strength is 310 MPa in Annealed versus 550 MPa in CD.
How much does 310Cb cost?
310Cb is a premium-cost stainless steel ($$$), cheaper than about 51% 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 A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip (UNS S31040) — ASTM International (2023)
- ASTM A479/A312 — stainless bar and welded/seamless pipe requirements — ASTM International (2022)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Specialty Handbook — Stainless Steels — ASM International (1994)
- 310/310S/310Cb heat-resisting stainless datasheets — Outokumpu / Sandvik / NAS (2022)
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.