Key Considerations for Selecting and Managing Low-Temperature Pressure Vessel Materials

Low-temperature pressure vessels play a crucial role in industries such as LNG storage, cryogenic chemical processing, and refineries, where materials are exposed to subzero conditions. The reliability and safety of these vessels depend largely on the selection and quality control of low-temperature steels.

This article explores the ASTM-equivalent materials, typical failure modes such as brittle fracture, and best practices in material inspection and management.

1.Classification of Low-Temperature Steels by Service Temperature

Low-temperature steels are typically classified by their working temperature ranges. The appropriate material selection depends on both operational temperature and required mechanical properties, especially impact toughness.

Steels like 16MnDR, 09MnNiDR, and 15MnNiDR in Chinese standards correspond to ASTM A333 Grade 6 or A350 LF2 for normalized carbon-manganese-nickel steels. For higher nickel content (5–9%), equivalents include ASTM A203 or A553 Type I. Austenitic stainless steel such as CF-62 is comparable to ASTM A240 Type 304 or 316L, widely used in cryogenic service.

Pressure vessels provided by Haihao Group

2.Preventing Brittle Fracture in Cryogenic Steels

At low temperatures, the primary failure mode is brittle fracture. This occurs when the service temperature drops below the steel’s Nil Ductility Transition Temperature (NDTT), and a sharp notch or flaw is present.

The steel’s Charpy V-notch impact value (Akv) reflects its ability to deform plastically and resist crack propagation at low temperatures. All materials selected must demonstrate sufficient low-temperature toughness through standardized impact testing.

3.Material Procurement and Inspection Requirements

To ensure compliance and material traceability, low-temperature steel procurement should follow strict internal quality standards and come from qualified suppliers.

Key Procurement Specifications:

Steelmaking Process: Fully killed, fine-grain practice recommended.

Heat Treatment: Normalizing, quenching, or tempering as required.

Microstructure Control: Verified for toughness and absence of segregation.

Mill and Incoming Inspection Includes:

Chemical Composition verification per ASTM standard.

Mechanical Properties: Tensile and yield strength testing at room temperature.

Low-Temperature Impact Testing: Usually at –46°C (–50°F) or specified operating temperature.

Ultrasonic Testing (UT): To detect internal flaws before fabrication.

Materials should be inspected by heat lot and according to specification, heat number, thickness, and heat treatment batch. For dished heads and spherical shell plates, testing is batch-based.

4.Welding Materials and Procedures for Low-Temperature Service

Welding consumables must closely match the chemical composition and mechanical properties of the base metal:

Use low-hydrogen basic electrodes (e.g., E7018-1 or E8018-C3) for SMAW.

Submerged Arc Welding (SAW) should use neutral or basic fluxes with proven low-temperature toughness.

Each batch of welding rods should be tested for diffusible hydrogen content and coating moisture.

5.On-Site Material Management and Identification

Improper handling of cryogenic steel on-site can result in material confusion, which poses a major safety risk. Therefore, strict management of storage, issuance, and labeling is essential.

Best Practices:

Dedicated warehouse and personnel for cryogenic steel and electrodes.

Post-receipt materials should be clearly color-coded and not stamped to avoid surface damage.

Segregate materials by heat number, size, and grade.

Store fabricated components on racks with 300mm minimum clearance from floors and walls.

Electrode Storage Room must maintain:

Temperature ≥ 10°C

Humidity ≤ 60%

Pre-use baking at 300–350°F (150–180°C) for 2 hours, stored in dry heated boxes.

6.Summary

Proper selection, inspection, and handling of low-temperature ASTM steels such as A333, A350 LF2, A553 Type I, and austenitic stainless steels are essential for ensuring safe and durable cryogenic pressure vessels. As brittle fracture remains a primary concern, attention must be paid to impact properties, welding quality, and traceability management from procurement to final assembly.

Haihao Group provides certified low-temperature fittings and piping components engineered for cryogenic environments. All products meet ASME, ASTM, and EN standards, with full MTR documentation and impact test records.

Contact us today for expert guidance and cryogenic-ready piping solutions. Email:sales@haihaogroup.com