Stainless Steel CN7M-ST (Solution annealed)
Heat-treated state · default condition
ASTM CN7M · UNS J95150, N08007
Standard supply condition for all corrosion service — heated ≥1120 °C, held, and rapidly quenched to dissolve carbides and Cu-rich phases.
Values for the ST condition
Other CN7M tempers and conditions
CN7M is listed in 4 conditions; see the grade overview at CN7M.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
STDefaultThis page 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-ST?
CN7M-ST is CN7M heat treated to ST — standard supply condition for all corrosion service — heated ≥1120 °C, held, and rapidly quenched to dissolve carbides and Cu-rich phases. CN7M-ST 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). CN7M-ST 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).
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-ST properties
Typical room-temperature values for CN7M-ST; 23 are specific to this condition. Other listed values are CN7M reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
CN7M-ST 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-ST 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-ST 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-ST 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-ST 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-ST'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. Confirm any required mill or lot documentation when quoting.
Working with CN7M-ST
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.
What surface finishes work on CN7M?
Pickle and passivate (nitric or citric) after grinding; electropolish for high-purity chemical service — anodizing does not apply.
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 | — |
CN7M-ST — frequently asked
What is CN7M-ST used for?
CN7M-ST 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-ST?
CN7M-ST 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-ST 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-ST 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-ST?
Pickle and passivate (nitric or citric) after grinding; electropolish for high-purity chemical service — anodizing does not apply.
Can CN7M-ST 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-ST?
CN7M-ST 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.