What is the applicable temperature range for different types of stainless steel tubes in a liquid ni

The applicable temperature range of different types of stainless steel tubes in a liquid nitrogen environment (-196℃) is closely related to their material composition, crystal structure, and low-temperature toughness. The following is a detailed classification explanation based on material characteristics, standard specifications, and experimental data:

1. Austenitic Stainless Steel: The Core Choice for Liquid Nitrogen Environments

Austenitic stainless steel, with its face-centered cubic (FCC) crystal structure, has no transition from ductile to brittle behavior at low temperatures and is the preferred material for liquid nitrogen pipelines. Its applicable temperature range covers the entire temperature range of liquid nitrogen (-196℃), and some models can extend to even lower temperatures:

1. 304/304L Stainless Steel

Applicable temperature: -196℃ (boiling point of liquid nitrogen) and above.

Performance basis:

Low-temperature toughness: Impact energy ≥ 27J at -196℃ (GB/T 18984-2003), and no risk of martensite transformation.

Standard support: ASTM A312 allows TP304/304L to be tested without impact at -250℃.

Application cases: Liquid nitrogen storage tank outlet pipes, low-temperature pipeline systems.

2. 316/316L Stainless Steel

Applicable temperature: -196℃ to -269℃ (temperature of liquid helium).

Performance basis:

Nickel content advantage: 10-14% Ni strengthens the stability of austenite, impact energy ≥ 34J at -196℃ (ASME BPVC requirement).

Extreme low-temperature verification: 316L maintains 36% elongation at liquid helium temperature (-269℃).

Special scenarios: Low-temperature structural materials for nuclear fusion superconducting magnets (such as the ITER project).

3. 310S (25Cr-20Ni) Stainless Steel

Applicable temperature: -196℃ and below.

Performance basis:

High nickel-chromium combination: 20% Ni inhibits martensite transformation at low temperatures, stable magnetic permeability at liquid helium temperature (-269℃).

Experimental data: Tensile strength reaches 1248MPa at -196℃, suitable for high magnetic field environments.

4. Super Austenitic Stainless Steel (such as 904L, 254SMO)

Applicable temperature: -196℃ and above.

Performance characteristics:

Corrosion resistance priority: 904L (25Ni-4.5Mo) performs well in low-temperature media containing chloride ions, but low-temperature toughness data is limited.

Special design: 254SMO (6Mo) is suitable for high-pressure liquid nitrogen environments at -196℃, but impact performance needs additional verification. 

II. Restrictions on Other Types of Stainless Steels

1. Ferritic Stainless Steels (such as 430, 008Cr30Mo2)

Limiting Temperature: Above -100℃.

Failure Mechanism:

Hardenability-Crystallinity Transition: The impact toughness of ferritic steel drops sharply below -40℃ (e.g., 008Cr30Mo2 exhibits brittle fracture at -40℃).

Standard Prohibition: GB/T 18984 explicitly excludes ferritic steel for use in -196℃ scenarios.

2. Martensitic Stainless Steels (such as 410, 420)

Limiting Temperature: Above -50℃.

Risk Analysis:

Low Temperature Brittleness: Insufficient impact energy of less than 10J below -50℃, prone to brittle fracture.

Application Prohibition: Prohibited for use in liquid nitrogen pipelines, only suitable as an alternative to carbon steel for non-critical low-temperature components above -50℃.

3. Duplex Stainless Steels (such as 2205, 2507)

Limiting Temperature: Above -40℃.

Performance Limitations:

Percentage of Ferrite Phase: Approximately 50% ferrite leads to a decrease in toughness below -40℃, with impact energy ≤ 20J.

Special Treatment: Requires passing a -40℃ impact test to be used in LNG tanks (-162℃). 

III. Key Influencing Factors and Verification Requirements

1. Material Composition and Heat Treatment

Carbon content control: Low carbon (≤0.03%) can prevent intergranular corrosion. The loss of low-temperature toughness after 304L/316L welding at low temperatures is ≤30%.

Cold processing impact: Cold-rolled 316L has a strength increase of 15% at -196℃, but this needs to be verified through -196℃ impact tests.

2. Standards and Test Requirements

Domestic Standards:

GB/T 18984 requires -196℃ impact energy ≥27J, and the impact energy of the weld heat-affected zone should be ≥70% of the base material.

GB/T 150-2024 stipulates that austenitic vessels with a design temperature ≤-196℃ need additional verification.

International Standards:

ASME BPVC allows 304/316 to be tested without impact tests at -250℃, but material certification is required.

ASTM A312 requires the low-temperature impact energy of welded pipes to be ≥20J (-196℃).

3. Engineering Verification Methods

Low-temperature Impact Test: The Schmidle V-notch impact energy (KV₂) is the core indicator. Austenitic steel at -196℃ should be ≥27J.

Strain Control: The linear expansion coefficient of austenitic steel is 17×10⁻⁶/℃, and a bellows compensator needs to be set to absorb the contraction at -196℃. 

IV. Summary and Selection Suggestions

Picture 1 

Notes:

1. The liquid nitrogen pipelines should preferentially use seamless pipes (ASTM A312 seamless grade), and welded pipes should undergo 100% radiographic testing.

2. When the design pressure is greater than 10 MPa, the wall thickness of 316L needs to be ≥ 3mm, and a -196℃ burst test must be passed.

3. For pipelines with long-term service (＞10 years), the stability of the carburized layer needs to be regularly tested (for example, after low-temperature carburization of 316L, 300℃ aging verification is required).

By combining material properties, standard specifications, and engineering verification, the long-term reliability of stainless steel pipes in the liquid nitrogen environment can be ensured.