12Ni14 Low-Temperature Nickel Steel
12Ni14 is a 12-14% nickel alloy steel designed for extreme cryogenic applications, primarily used in liquefied natural gas (LNG) storage and transportation systems.
Key Characteristics
Material Type: Nickel-alloyed ferritic steel (not a carbon steel)
Primary Standard: EN 10028-4 (Flat products for pressure purposes - Nickel alloy steels)
Temperature Range: Suitable for service down to -196°C (-321°F)
Main Application: LNG storage tanks, cryogenic vessels
Heat Treatment: Double normalized and tempered, or quenched and tempered
Chemical Composition (EN 10028-4)
| Element | Content (%) | Notes |
|---|---|---|
| C | ≤ 0.15 | Low carbon for weldability |
| Si | ≤ 0.35 | |
| Mn | ≤ 0.70 | Limited manganese content |
| P | ≤ 0.020 | Very low for cryogenic toughness |
| S | ≤ 0.010 | Very low for weldability |
| Ni | 12.0-14.0 | High nickel content for extreme low-temperature toughness |
| Cr | ≤ 0.25 | |
| Mo | ≤ 0.10 | |
| Cu | ≤ 0.25 | |
| Al | ≤ 0.050 |
Mechanical Properties
| Property | Value | Test Condition |
|---|---|---|
| Yield Strength (Rp0.2), min | 500 MPa | After heat treatment |
| Tensile Strength (Rm) | 620-780 MPa | |
| Elongation (A), min | 20% | |
| Impact Energy (KV), min | At -196°C: Average of 3 tests: ≥ 70 J Single value: ≥ 50 J |
Charpy V-notch |
Comparison with Other Nickel Steels
| Grade | Nickel Content | Min Yield Strength | Key Application Temperature |
|---|---|---|---|
| 12Ni14 | 12-14% | 500 MPa | -196°C |
| X10Ni9 | 8.5-10% | 585 MPa | -196°C |
| X8Ni9 | 8-9% | 640 MPa | -196°C |
| 9% Ni Steel | 9% | 585-690 MPa | -196°C |
Heat Treatment Requirements
12Ni14 requires specific heat treatment to achieve its properties:
Double Normalizing and Tempering:
First normalize: 900-950°C
Second normalize: 800-850°C
Temper: 550-600°C
Quenching and Tempering:
Quench from 800-850°C
Temper at 550-600°C
Application Areas
Primary Applications:
LNG Industry:
Primary and secondary containment of LNG storage tanks
LNG ship tanks and cargo holds
LNG processing equipment
Cryogenic Engineering:
Liquid hydrogen storage (with special considerations)
Ethylene storage at cryogenic temperatures
Specialized cryogenic research equipment
Energy Sector:
Components for LNG-fueled power plants
Cryogenic energy storage systems
Pipe Specifications
Pipes made from 12Ni14 are covered under:
EN 10216-4: Seamless steel tubes for pressure purposes with specified low temperature properties
EN 10217-4: Welded steel tubes for pressure purposes with specified low temperature properties
Welding Considerations
| Aspect | Requirement |
|---|---|
| Filler Metals | High-nickel consumables (typically 12-13% Ni) |
| Preheating | Generally not required |
| Interpass Temperature | Controlled below 150°C |
| Welding Processes | SMAW, GTAW, SAW with qualified procedures |
| PWHT | Required to restore HAZ properties |
Design and Fabrication Notes
Material Selection: Used when exceptional toughness at -196°C is required
Fabrication Costs: High material and fabrication costs due to nickel content and special procedures
Thickness Limitations: Available in various thicknesses, but fabrication becomes more challenging with increasing thickness
Testing Requirements: Extensive NDT and mechanical testing required
Equivalent Grades
| Standard | Equivalent Designation |
|---|---|
| ASTM/ASME | Similar to SA 645 (5% Ni) but higher Ni content |
| ISO | Similar designations in development |
| JIS | No direct equivalent |
| GB (China) | Under development in Chinese standards |
Important Technical Notes
Phase Transformation: 12Ni14 operates in the fully ferritic phase at cryogenic temperatures
Fracture Toughness: Excellent resistance to brittle fracture at -196°C
Thermal Expansion: Lower thermal expansion coefficient than austenitic stainless steels
Magnetic Properties: Ferritic structure makes it magnetic
Market and Availability
Limited Production: Produced by specialized steel mills
Lead Times: Longer delivery times compared to conventional steels
Certification: Requires extensive certification and traceability
Global Suppliers: Limited number of manufacturers worldwide
Comparison with Austenitic Alternatives
| Parameter | 12Ni14 Steel | Austenitic Stainless (304L) |
|---|---|---|
| Thermal Conductivity | Higher | Lower |
| Thermal Expansion | Lower | Higher |
| Magnetic Properties | Magnetic | Non-magnetic |
| Cost at Equal Strength | Comparable or lower | Higher |
| Yield Strength | Higher | Lower |
Summary
12Ni14 is a specialized high-nickel (12-14%) alloy steel designed specifically for LNG storage and cryogenic applications at temperatures down to -196°C. It offers excellent fracture toughness at cryogenic temperatures while maintaining ferritic microstructure. Although referred to in some contexts for "boiler steel pipe," its actual application is far more specialized-primarily in the cryogenic and LNG industries rather than conventional boiler systems. The material requires careful heat treatment, specialized welding procedures, and rigorous quality control to ensure performance in critical cryogenic service.
