Stainless Steel CK20
ASTM CK20 · UNS J94202
CK20 is a 25Cr-20Ni cast austenitic stainless steel (UNS J94202), the casting equivalent of wrought 310 in the heat-resistant casting family.
Reference datasheet — CK20 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 HT condition
CK20 tempers and conditions
CK20 is supplied in 4 conditions, soft to hard. HT 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 |
|---|---|---|---|---|---|---|
HTDefault Solution heat treated | Standard supply condition for ASTM A351 CK20 pressure castings: maximum ductility, toughness and corrosion resistance. | 250 | 520 | 37 | 170 HB | 2 % IACS |
Spheroidize annealed | Used for non-pressure heat-resistant furnace hardware where interdendritic carbides are acceptable; slightly harder, lower ductility and toughness. | 260 | 490 | 22 | 180 HB | 2 % IACS |
Centrifugally cast pipe/tube, heat treated | Choose for high-temperature piping and furnace tubes; the centrifugal structure gives cleaner, denser walls and slightly better strength than static castings. | 260 | 540 | 35 | 175 HB | 2 % IACS |
Service-exposed / thermally aged | Reference condition for assessing parts after long furnace service: carbide and sigma precipitation raise hardness but sharply cut room-temperature toughness. | 300 | 560 | 8 | 14 HRC | 2 % IACS |
What is CK20?
CK20 is a 25Cr-20Ni cast austenitic stainless steel (UNS J94202), the casting equivalent of wrought 310 in the heat-resistant casting family. The high nickel content stabilizes the austenite and supports oxidation resistance to 1100 °C, with 250 MPa yield, 520 MPa tensile, 37 % elongation and about 170 HB in the heat-treated condition; parts are produced as static, centrifugal and HIP-processed castings. Chloride and acid resistance is moderate, the fully austenitic weld metal is hot-crack sensitive, and the nickel level makes it costlier than CH20. Where 1000 °C service is sufficient, CH20 is the cheaper choice. CK20 has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,400°C (2,552 °F). CK20 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 37% and the elastic modulus is 193 GPa (28 Msi).
What is CK20 used for?
- Furnace parts
- High-temperature process equipment
- Heat treating baskets and fixtures
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
Limitations
- Low strength — 250 MPa (36.3 ksi), worse than 91% of stainless steel grades
- Hard to polish — 55/100, worse than 89% of stainless steel grades
- Limited formability — 20/100, worse than 86% of stainless steel grades
- Low electrical conductivity — 2 % IACS, worse than 77% of stainless steel grades
CK20 properties
Typical room-temperature values for CK20-HT; bars are the position among stainless steel grades.
Physical3
CK20 has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical16
CK20 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 37% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
CK20 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
CK20 conducts electricity at 2 % IACS, worse than 77% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (68/100), better than 63% of stainless steel grades.
Sustainability4
Producing a kilogram of CK20 takes about 55 MJ of energy and emits 4.5 kg of CO₂ — more than 50% of stainless steel grades. Typical recycled content is 75%.
Manufacturability8
CK20's machinability is poor (28/100, worse than 79% of stainless steel grades); weldability good (60/100); formability poor (20/100).
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. CK20 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with CK20
Is CK20 easy to machine?
Machine with rigid setups, sharp carbide tooling, low speed and heavy positive feed to cut under the work-hardened skin; flood coolant is essential.
Can CK20 be welded?
Weld with 310/ER310 filler using GTAW or SMAW, low heat input and no preheat; interpass temperature control limits hot cracking and sigma formation.
Can CK20 be formed, bent or molded?
Supplied as a casting — design generous risers and fillets for the high solidification shrinkage; no cold forming.
CK20 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 |
|---|---|---|
| C0.20 max per ASTM A351/A451 CK20 | ≤ 0.2 | 0.15 |
| Mnsome standards/foundries limit to 1.50 max | ≤ 2 | 1.2 |
| Si | ≤ 1.75 | 1.2 |
| P | ≤ 0.04 | 0.03 |
| S | ≤ 0.04 | 0.02 |
| Cr | 23 – 27 | 25 |
| Ni | 19 – 22 | 20.5 |
| Moresidual, per purchaser agreement | ≤ 0.5 | |
| Fe | balance |
What surface finishes work on CK20?
Grind/blast and passivate or pickle to restore the chromium oxide film; do not anodize, and avoid carbon-steel contamination during cleaning.
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 CK20 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- J94202
- Also called
- Cast 310
How much does CK20 cost?
CK20 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.
CK20 — frequently asked
What is CK20 used for?
CK20 is typically used for furnace parts, high-temperature process equipment and heat treating baskets and fixtures. In short: cast 310 equivalent; 1100 °C oxidation service; stable fully austenitic structure.
What is the yield strength of CK20?
CK20 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 CK20 easy to machine?
Not especially — machinability is rated poor (28/100, worse than 79% of stainless steel grades). Machine with rigid setups, sharp carbide tooling, low speed and heavy positive feed to cut under the work-hardened skin; flood coolant is essential.
Can CK20 be welded?
Yes — weldability is rated good (60/100). Weld with 310/ER310 filler using GTAW or SMAW, low heat input and no preheat; interpass temperature control limits hot cracking and sigma formation.
What surface finishes work on CK20?
Grind/blast and passivate or pickle to restore the chromium oxide film; do not anodize, and avoid carbon-steel contamination during cleaning.
Can CK20 be formed, bent or molded?
Supplied as a casting — design generous risers and fillets for the high solidification shrinkage; no cold forming.
What is the maximum service temperature of CK20?
CK20 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 CK20-HT and CK20 Aged?
HT is the default condition — standard supply condition for ASTM A351 CK20 pressure castings: maximum ductility, toughness and corrosion resistance. Aged: reference condition for assessing parts after long furnace service: carbide and sigma precipitation raise hardness but sharply cut room-temperature toughness. Yield strength is 250 MPa in HT versus 300 MPa in Aged.
How much does CK20 cost?
CK20 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 A351/A351M — Castings, Austenitic, for Pressure-Containing Parts — ASTM International (2018)
- ASTM A451/A451M — Centrifugally Cast Austenitic Steel Pipe for High-Temperature Service — ASTM International (2021)
- ASM Handbook Vol. 1: Properties and Selection: Irons, Steels, and High-Performance Alloys (Cast Stainless Steels) — ASM International (1990)
- Steel Castings Handbook — Steel Founders' Society of America / ASM International (1995)
- ASM Handbook Vol. 13B: Corrosion — Materials — ASM International (2005)
- GB/T 8492 (ZG40Cr25Ni20 ) (2014)
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.