Steel X7Ni9
EN X7Ni9
X7Ni9 (1.5663, ASTM A353 equivalent) is the low-carbon variant of the 9% nickel cryogenic steel family, heat treated as +QT, +NT or +NNT and also stocked annealed (+A).
Reference datasheet — X7Ni9 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 +QT condition
X7Ni9 tempers and conditions
X7Ni9 is supplied in 4 conditions, soft to hard. +QT 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 |
|---|---|---|---|---|---|---|
Annealed | Soft interim condition for heavy machining or forming of forgings/bar; parts are re-hardened to +QT or +NT before cryogenic service. | 450 | 640 | 28 | 10 HRC | 3.8 % IACS |
Normalized and tempered | Lower-yield (490 MPa class) condition used for thick plate and forgings where quench distortion or hardenability limits apply. | 550 | 700 | 25 | 200 HB | — |
Double normalized and tempered | ASTM A353-style delivery condition: two normalizing cycles plus temper for uniform toughness in heavy plate without quenching facilities. | 570 | 720 | 25 | 205 HB | — |
+QTDefault Quenched and tempered | Highest-strength standard condition for LNG inner-tank plate and pressure parts; pick when the design uses the 585 MPa yield class. | 640 | 730 | 24 | 19 HRC | — |
What is X7Ni9?
X7Ni9 (1.5663, ASTM A353 equivalent) is the low-carbon variant of the 9% nickel cryogenic steel family, heat treated as +QT, +NT or +NNT and also stocked annealed (+A). The reduced carbon improves weldability while keeping toughness for pressure vessels operating near -196 °C; default properties are 640 MPa yield, 730 MPa tensile, 24% elongation and about 215 HB (19 HRC). Machinability is low at 40, the steel has no inherent corrosion resistance and hot service is limited to about 350 °C. Choose X8Ni9 or X10Ni9 when a higher yield strength is needed. X7Ni9 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,430°C (2,606 °F). X7Ni9 has a yield strength of 640 MPa (92.8 ksi) and a tensile strength of 730 MPa (106 ksi) — stronger than 79% of steel grades. Elongation at break is 24% and the elastic modulus is 195 GPa (28.3 Msi).
What is X7Ni9 used for?
- LNG tanks
- cryogenic pressure vessels
- gas piping
Advantages
- Tough — resists crack growth — 180 MPa·√m (163.8 ksi·√in), better than 99% of steel grades
- High strength — 640 MPa (92.8 ksi), better than 79% of steel grades
Limitations
- High embodied carbon — 3 kg CO₂/kg, worse than 91% of steel grades
- Low electrical conductivity — 3.8 % IACS, worse than 84% of steel grades
- Poor heat conductor — 30 W/m·K (17.3 BTU/hr·ft·°F), worse than 83% of steel grades
- Difficult to machine — 40/100, worse than 77% of steel grades
X7Ni9 properties
Typical room-temperature values for X7Ni9-+QT; bars are the position among steel grades.
Physical3
X7Ni9 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,430°C (2,606 °F).
Mechanical17
X7Ni9 has a yield strength of 640 MPa (92.8 ksi) and a tensile strength of 730 MPa (106 ksi) — stronger than 79% of steel grades. Elongation at break is 24% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
X7Ni9 is rated for continuous service to 350°C (662 °F). It conducts heat at 30 W/m·K (17.3 BTU/hr·ft·°F), worse than 83% of steel grades. Thermal expansion is 10.2 µm/m·K (5.67 µin/in·°F).
Electrical3
X7Ni9 conducts electricity at 3.8 % IACS, worse than 84% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (16/100), better than 79% of steel grades.
Sustainability4
Producing a kilogram of X7Ni9 takes about 40 MJ of energy and emits 3 kg of CO₂ — more than 91% of steel grades. Typical recycled content is 25%.
Manufacturability7
X7Ni9's machinability is fair (40/100, worse than 77% of steel grades); weldability good (55/100); formability fair (48/100).
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 steel family
Yield strength against density for every steel grade FabDigit runs. X7Ni9 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with X7Ni9
Is X7Ni9 easy to machine?
Machine like a tough 200–230 HB alloy steel: rigid setup, positive-rake carbide, moderate speed with heavy feed and copious coolant to avoid work-hardened glazing.
Can X7Ni9 be welded?
Weld with Ni-base consumables (ENiCrMo-6, ERNiCrMo-3/ERNiCrMo-4); control heat input, demagnetize plate before welding (arc blow), preheat usually ≤100 °C and PWHT normally not required.
Can X7Ni9 be formed, bent or molded?
Hot form at 850–950 °C followed by the specified NT/QT cycle; cold forming is possible but springback is high and severe cold work should be followed by re-heat treatment.
X7Ni9 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 |
|---|---|---|
| CEN 10028-4 max; ASTM A553 Type I allows 0.13 max | ≤ 0.1 | 0.06 |
| Si | 0.1 – 0.35 | 0.25 |
| Mn | 0.3 – 0.8 | 0.55 |
| Plow P/S for cryogenic toughness | ≤ 0.02 | 0.01 |
| S | ≤ 0.01 | 0 |
| NiASTM A553 Type I: 8.5–9.5 | 8.5 – 10 | 9 |
| Crresidual | ≤ 0.3 | 0.05 |
| Moresidual | ≤ 0.1 | 0.03 |
| Curesidual | ≤ 0.3 | 0.05 |
| Vresidual | ≤ 0.05 | 0.01 |
| N | ≤ 0.01 | 0.01 |
| AlAl-killed / grain refinement | 0.02 – 0.06 | 0.03 |
| Fe | balance |
What surface finishes work on X7Ni9?
Not anodizable — shot-blast then epoxy/zinc-rich paint or metallize; keep surfaces dry, and verify residual magnetism and cleanliness before cryogenic commissioning.
Surface treatments FabDigit runs on 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).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel X7Ni9 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- EN / DIN / Werkstoff-Nr.
- 1.5663
- Similar grades
- A353
How much does X7Ni9 cost?
X7Ni9 is a premium-cost steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
X7Ni9 — frequently asked
What is X7Ni9 used for?
X7Ni9 is typically used for LNG tanks, cryogenic pressure vessels and gas piping. In short: most weldable 9Ni grade; service near -196 °C; low-carbon cryogenic plate steel.
What is the yield strength of X7Ni9?
X7Ni9 has a typical yield strength of 640 MPa (92.8 ksi) and a tensile strength of 730 MPa (106 ksi) — stronger than 79% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is X7Ni9 easy to machine?
Not especially — machinability is rated fair (40/100, worse than 77% of steel grades). Machine like a tough 200–230 HB alloy steel: rigid setup, positive-rake carbide, moderate speed with heavy feed and copious coolant to avoid work-hardened glazing.
Can X7Ni9 be welded?
Yes — weldability is rated good (55/100). Weld with Ni-base consumables (ENiCrMo-6, ERNiCrMo-3/ERNiCrMo-4); control heat input, demagnetize plate before welding (arc blow), preheat usually ≤100 °C and PWHT normally not required.
What surface finishes work on X7Ni9?
Not anodizable — shot-blast then epoxy/zinc-rich paint or metallize; keep surfaces dry, and verify residual magnetism and cleanliness before cryogenic commissioning.
Can X7Ni9 be formed, bent or molded?
Hot form at 850–950 °C followed by the specified NT/QT cycle; cold forming is possible but springback is high and severe cold work should be followed by re-heat treatment.
What is the maximum service temperature of X7Ni9?
X7Ni9 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does X7Ni9 cost?
X7Ni9 is a premium-cost steel ($$$), 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
- EN 10028-4: Flat products of steels for pressure purposes — Nickel alloy steels with specified low temperature properties — CEN (2017)
- ASTM A553/A553M Quenched and Tempered 7, 8 and 9% Nickel Alloy Steel Pressure Vessel Plates — ASTM International (2022)
- ASTM A353/A353M Double-Normalized and Tempered 9% Nickel Alloy Steel Plates — ASTM International (2022)
- EN 10222-3 Steel forgings for pressure purposes — Nickel steels with specified low temperature properties — CEN (1998)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (cryogenic Ni steels) — ASM International (1990)
- ASME BPVC Section II Part D — Material properties (thermal/elastic data, 9Ni) — ASME (2023)
- 9% Nickel cryogenic pressure vessel plate datasheets (Dillinger / JFE / Nippon Steel / ) — various mills (2023)
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.