Stainless Steel 20Cb-3
UNS N08020 · ASTM B473 · EN 2.4660 · also Carpenter 20
20Cb-3 is an iron-nickel-chromium-molybdenum-copper superaustenitic stainless (UNS N08020, 2.4660, ASTM B473, also sold as Carpenter 20) engineered for resistance to sulfuric acid and other hot corrosive chemical media.
Values for the Solution Annealed condition
20Cb-3 tempers and conditions
20Cb-3 is supplied in 3 conditions, soft to hard. Solution Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
mill annealed bar / forging (hot finished and annealed) | Pick for hot-finished bar, forgings and heavy sections where softest, most ductile condition is wanted for further forming or welding. | 310 | 600 | 45 | 150 HB | — |
Solution AnnealedDefault 925–1010 °C, rapid quench (mill standard for sheet, plate, pipe) | Standard as-supplied condition for plate, sheet, pipe and fittings; maximum corrosion resistance and ductility. | 345 | 620 | 42 | 160 HB | — |
cold drawn / cold finished bar and shapes | Choose for higher-strength bar, shafting and fasteners where tight tolerance and better surface are needed; ductility and formability are reduced. | 620 | 790 | 22 | 24 HRC | — |
Supply forms, finishes and certifications
Ways 20Cb-3 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
Cold Drawn Hard Wire | Cold Drawn Hard | Supply form |
What is 20Cb-3?
20Cb-3 is an iron-nickel-chromium-molybdenum-copper superaustenitic stainless (UNS N08020, 2.4660, ASTM B473, also sold as Carpenter 20) engineered for resistance to sulfuric acid and other hot corrosive chemical media. Annealed material gives 345 MPa yield, 620 MPa tensile, 42 % elongation and 160 HB (83 HRB), and is stocked as annealed and solution-annealed plate, sheet and bar plus cold-drawn bar and hard-drawn wire. Limits are about 500 °C maximum service, gummy work-hardening machining and the chloride pitting sensitivity common to austenitics; 904L or 316L are the usual alternatives when sulfuric acid is not the controlling medium. 20Cb-3 has a density of 8.08 g/cm³ (0.292 lb/in³), heavier than 99% of stainless steel grades. It melts at 1,425°C (2,597 °F). 20Cb-3 has a yield strength of 345 MPa (50 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 54% of stainless steel grades. Elongation at break is 42% and the elastic modulus is 193 GPa (28 Msi).
What is 20Cb-3 used for?
- Sulfuric acid pumps
- Pickling baths and tanks
- Chemical process piping and fittings
- Heat exchanger tubing and tubesheets
- Valve bodies and pump impellers
- Agitator shafts and mixing blades
- Pharmaceutical and food processing vessels
- Fasteners for acid service
Advantages
- Forms and bends easily — 70/100, better than 79% of stainless steel grades
Limitations
- Low electrical conductivity — 1.6 % IACS, worse than 99% of stainless steel grades
- High embodied carbon — 7.5 kg CO₂/kg, worse than 97% of stainless steel grades
- Poor heat conductor — 12.6 W/m·K (7.28 BTU/hr·ft·°F), worse than 88% of stainless steel grades
20Cb-3 properties
Typical room-temperature values for 20Cb-3-Solution Annealed; bars are the position among stainless steel grades.
Physical3
20Cb-3 has a density of 8.08 g/cm³ (0.292 lb/in³), heavier than 99% of stainless steel grades. It melts at 1,425°C (2,597 °F).
Mechanical14
20Cb-3 has a yield strength of 345 MPa (50 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 54% of stainless steel grades. Elongation at break is 42% and the elastic modulus is 193 GPa (28 Msi).
Thermal5
20Cb-3 is rated for continuous service to 500°C (932 °F). It conducts heat at 12.6 W/m·K (7.28 BTU/hr·ft·°F), worse than 88% of stainless steel grades. Thermal expansion is 14.8 µm/m·K (8.22 µin/in·°F).
Electrical3
20Cb-3 conducts electricity at 1.6 % IACS, worse than 99% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), better than 73% of stainless steel grades.
Sustainability4
Producing a kilogram of 20Cb-3 takes about 110 MJ of energy and emits 7.5 kg of CO₂ — more than 99% of stainless steel grades. Typical recycled content is 40%.
Manufacturability7
20Cb-3's machinability is poor (33/100, worse than 57% 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. 20Cb-3 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 20Cb-3
Is 20Cb-3 easy to machine?
Gummy and strongly work-hardening — use rigid setups, positive-rake carbide, heavy feeds with slow speeds (~25–40% of 1212 rates), never dwell, and flood with chlorine-free coolant.
Can 20Cb-3 be welded?
Readily welded by GTAW/GMAW/SMAW with over-alloyed Nb-bearing filler (ER320LR / E320LR); keep interpass temperature low, no preheat, avoid excessive heat input and post-weld sensitizing exposure.
Can 20Cb-3 be formed, bent or molded?
Cold forms like a tough austenitic — allow 2–3× the power of carbon steel, generous bend radii and interstage anneals at 925–1010 °C with rapid cooling; hot work 1150–1200 °C, finish above 925 °C.
Manufacturability
The process limits FabDigit applies to 20Cb-3. Every 20Cb-3 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Poor33 / 100 |
|---|---|
| ISO material group | M.1 |
| Cutting speed (rough / finish) | 150 / 180 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1.5 mm |
| Drill depth limit | 4× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Better70 / 100 |
|---|---|
| Weldability | Better75 / 100 |
| Bendable | Yes |
20Cb-3 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 |
|---|---|---|
| Ni | 32 – 38 | 34 |
| Cr | 19 – 21 | 20 |
| Mo | 2 – 3 | 2.5 |
| Cu | 3 – 4 | 3.5 |
| NbCb+Ta ≥ 8 × C (stabilizing); typically 0.3–1.0 % | ≈ 0.5 | 0.5 |
| C | ≤ 0.07 | 0.03 |
| Mn | ≤ 2 | 0.5 |
| Si | ≤ 1 | 0.5 |
| P | ≤ 0.05 | |
| S | ≤ 0.04 | |
| Febalance, nominally ~37 % | balance |
What surface finishes work on 20Cb-3?
Pickle and passivate (nitric-based) after welding or hot work to restore the passive film; polishes to a bright finish, cannot be anodized, and electroplating is only needed for special wear applications.
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).
Plating
Organic Coating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel 20Cb-3 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- N08020
- ASTM
- B473
- EN / DIN / Werkstoff-Nr.
- 2.4660
- Trade names
- Carpenter 20
- Also called
- Alloy 20
How much does 20Cb-3 cost?
20Cb-3 is a premium-cost stainless steel ($$$), pricier than about 58% 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.
20Cb-3 — frequently asked
What is 20Cb-3 used for?
20Cb-3 is typically used for sulfuric acid pumps, pickling baths and tanks, chemical process piping and fittings, heat exchanger tubing and tubesheets, valve bodies and pump impellers and agitator shafts and mixing blades. In short: sulfuric-acid-resistant austenitic stainless.
What is the yield strength of 20Cb-3?
20Cb-3 has a typical yield strength of 345 MPa (50 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 54% of stainless steel grades. Strength varies by condition: see the 3 listed tempers.
Is 20Cb-3 easy to machine?
Not especially — machinability is rated poor (33/100, worse than 57% of stainless steel grades). Gummy and strongly work-hardening — use rigid setups, positive-rake carbide, heavy feeds with slow speeds (~25–40% of 1212 rates), never dwell, and flood with chlorine-free coolant.
Can 20Cb-3 be welded?
Yes — weldability is rated very good (75/100). Readily welded by GTAW/GMAW/SMAW with over-alloyed Nb-bearing filler (ER320LR / E320LR); keep interpass temperature low, no preheat, avoid excessive heat input and post-weld sensitizing exposure.
What surface finishes work on 20Cb-3?
Pickle and passivate (nitric-based) after welding or hot work to restore the passive film; polishes to a bright finish, cannot be anodized, and electroplating is only needed for special wear applications.
Can 20Cb-3 be formed, bent or molded?
Cold forms like a tough austenitic — allow 2–3× the power of carbon steel, generous bend radii and interstage anneals at 925–1010 °C with rapid cooling; hot work 1150–1200 °C, finish above 925 °C.
What is the maximum service temperature of 20Cb-3?
20Cb-3 is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 20Cb-3 cost?
20Cb-3 is a premium-cost stainless steel ($$$), pricier than about 58% 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.
Can FabDigit make parts in 20Cb-3?
Yes — 20Cb-3 is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM B463 — Alloy N08020 Plate, Sheet and Strip — ASTM International (2020)
- ASTM B473 — UNS N08020 Bar and Wire — ASTM International (2020)
- ASTM B464/B729 — N08020 Welded and Seamless Pipe — ASTM International (2020)
- Carpenter 20Cb-3 Stainless Alloy Technical Datasheet — Carpenter Technology (2020)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Corrosion data for Fe-Ni-Cr-Mo-Cu alloys in sulfuric acid — NACE/AMPP compilations (2018)
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.