Stainless Steel CN7M
ASTM CN7M · UNS J95150, N08007
CN7M is a high-nickel cast austenitic alloy with molybdenum and copper additions — the casting version of Alloy 20 — covered by ASTM A351/A743/A744 (UNS J95150, related to wrought N08020).
Reference datasheet — CN7M 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 ST condition
CN7M tempers and conditions
CN7M is supplied in 4 conditions, soft to hard. ST 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 |
|---|---|---|---|---|---|---|
STDefault Solution annealed | Standard supply condition for all corrosion service — heated ≥1120 °C, held, and rapidly quenched to dissolve carbides and Cu-rich phases. | 220 | 480 | 45 | 140 HB | 1.6 % IACS |
Hot isostatically pressed then solution annealed | For critical pressure-retaining or fatigue-loaded castings where internal porosity must be closed. | 225 | 500 | 50 | 140 HB | 1.6 % IACS |
As fabricated | Only for non-corrosive structural or trial castings — grain-boundary carbides sharply reduce acid resistance, so it is not accepted by A351/A743. | 240 | 460 | 25 | 155 HB | 1.6 % IACS |
Centrifugally cast, solution annealed | Choose for pipe, sleeve and ring shapes — finer, denser structure from centrifugal casting gives slightly higher strength and better soundness. | 240 | 510 | 42 | 145 HB | 1.6 % IACS |
What is CN7M?
CN7M is a high-nickel cast austenitic alloy with molybdenum and copper additions — the casting version of Alloy 20 — covered by ASTM A351/A743/A744 (UNS J95150, related to wrought N08020). It is used where sulfuric acid and other strong acids attack CF8M, with solution-treated properties of 220 MPa yield, 480 MPa tensile, 45 % elongation and about 140 HB, and is produced as static, centrifugal and HIP-processed castings. Strength is the lowest in this group, service is limited to roughly 500 °C, chloride pitting resistance is below CK3MCuN, and the nickel-copper content makes it costly and slow to machine. CN7M has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,370°C (2,498 °F). CN7M has a yield strength of 220 MPa (31.9 ksi) and a tensile strength of 480 MPa (69.6 ksi) — weaker than 99% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 180 GPa (26.1 Msi).
What is CN7M used for?
- Sulfuric acid process valves and pumps
- Chemical processing equipment
- Fertilizer plant components
Advantages
- Good corrosion resistance — 85/100, better than 92% of stainless steel grades
- Ductile — tolerates forming and impact — 45%, better than 76% of stainless steel grades
Limitations
- Low strength — 220 MPa (31.9 ksi), worse than 99% of stainless steel grades
- Low electrical conductivity — 1.6 % IACS, worse than 99% 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
- High embodied carbon — 5.5 kg CO₂/kg, worse than 77% of stainless steel grades
CN7M properties
Typical room-temperature values for CN7M-ST; bars are the position among stainless steel grades.
Physical3
CN7M has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,370°C (2,498 °F).
Mechanical16
CN7M has a yield strength of 220 MPa (31.9 ksi) and a tensile strength of 480 MPa (69.6 ksi) — weaker than 99% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 180 GPa (26.1 Msi).
Thermal6
CN7M 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 14.7 µm/m·K (8.17 µin/in·°F).
Electrical3
CN7M conducts electricity at 1.6 % IACS, worse than 99% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 92% of stainless steel grades.
Sustainability4
Producing a kilogram of CN7M takes about 70 MJ of energy and emits 5.5 kg of CO₂ — more than 81% of stainless steel grades. Typical recycled content is 60%.
Manufacturability8
CN7M's machinability is fair (35/100, better than 51% of stainless steel grades); weldability very good (70/100); formability fair (40/100).
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. CN7M is highlighted; hover a dot for its name, or open the interactive family chart.
Working with CN7M
Is CN7M easy to machine?
Gummy and strongly work-hardening — use sharp positive-rake carbide, heavy positive feed, rigid setup, low-to-moderate speed (~50–90 m/min) and flood coolant to avoid glazing.
Can CN7M be welded?
Readily welded by GTAW/SMAW with matching CN7M or ER320LR / E320LR (Nb-stabilized) filler; keep interpass low, minimal dilution, and re-solution-anneal repaired pressure castings where the code allows.
Can CN7M be formed, bent or molded?
Wide freezing range demands generous risering, chills and controlled pouring (~1500–1540 °C) to avoid shrinkage porosity; always solution treat and water quench after cleaning.
CN7M 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 |
|---|---|---|
| CASTM A743/A351 max | ≤ 0.07 | 0.05 |
| Mn | ≤ 1.5 | 1 |
| Si | ≤ 1.5 | 1 |
| P | ≤ 0.04 | |
| S | ≤ 0.04 | |
| Cr | 19 – 22 | 20.5 |
| Ni | 27.5 – 30.5 | 29 |
| Mo | 2 – 3 | 2.5 |
| Cukey for sulfuric-acid resistance | 3 – 4 | 3.5 |
| Feremainder, ~40% | balance |
What surface finishes work on CN7M?
Pickle and passivate (nitric or citric) after grinding; electropolish for high-purity chemical service — anodizing does not apply.
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 CN7M in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- J95150N08007
- Also called
- Cast Alloy 20
- Similar grades
- N08020
How much does CN7M cost?
CN7M is a high-cost stainless steel ($$$$), pricier than about 78% 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.
CN7M — frequently asked
What is CN7M used for?
CN7M is typically used for sulfuric acid process valves and pumps, chemical processing equipment and fertilizer plant components. In short: best sulfuric acid resistance; cast Alloy 20; most ductile grade here.
What is the yield strength of CN7M?
CN7M has a typical yield strength of 220 MPa (31.9 ksi) and a tensile strength of 480 MPa (69.6 ksi) — weaker than 99% of stainless steel grades. Strength varies by condition: see the 4 listed tempers.
Is CN7M easy to machine?
Not especially — machinability is rated fair (35/100, better than 51% of stainless steel grades). Gummy and strongly work-hardening — use sharp positive-rake carbide, heavy positive feed, rigid setup, low-to-moderate speed (~50–90 m/min) and flood coolant to avoid glazing.
Can CN7M be welded?
Yes — weldability is rated very good (70/100). Readily welded by GTAW/SMAW with matching CN7M or ER320LR / E320LR (Nb-stabilized) filler; keep interpass low, minimal dilution, and re-solution-anneal repaired pressure castings where the code allows.
What surface finishes work on CN7M?
Pickle and passivate (nitric or citric) after grinding; electropolish for high-purity chemical service — anodizing does not apply.
Can CN7M be formed, bent or molded?
Wide freezing range demands generous risering, chills and controlled pouring (~1500–1540 °C) to avoid shrinkage porosity; always solution treat and water quench after cleaning.
What is the maximum service temperature of CN7M?
CN7M 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.
What is the difference between CN7M-ST and CN7M-F?
ST is the default condition — standard supply condition for all corrosion service — heated ≥1120 °C, held, and rapidly quenched to dissolve carbides and Cu-rich phases. F: only for non-corrosive structural or trial castings — grain-boundary carbides sharply reduce acid resistance, so it is not accepted by A351/A743. Yield strength is 220 MPa in ST versus 240 MPa in F.
How much does CN7M cost?
CN7M is a high-cost stainless steel ($$$$), pricier than about 78% 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 A743/A743M — Castings, Iron-Chromium-Nickel, Corrosion Resistant, for General Application — ASTM International (2021)
- ASTM A744/A744M — Castings, Iron-Chromium-Nickel, Corrosion Resistant, for Severe Service — ASTM International (2021)
- ASM Specialty Handbook: Stainless Steels — Cast Stainless Steels (ACI grades) — ASM International (1994)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- Alloy 20 (UNS N08020) technical data — Special Metals / Rolled Alloys (2020)
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.