What Is ASTM A553 Type 1 Steel?
ASTM A553 Type 1 is a high-nickel alloy steel plate specification issued by ASTM International. The material is commonly called 9% nickel steel because its nickel content ranges from 8.50% to 9.50% by weight. The steel combines a tensile strength of 690–825 MPa with exceptional low-temperature toughness, which makes it one of the most widely specified materials for cryogenic pressure vessels operating down to −196 °C (−320 °F), the boiling temperature of liquefied natural gas. It has been used for LNG and cryogenic containment since the 1960s, and its martensitic microstructure remains ductile rather than brittle at cryogenic temperature.
Chemical Composition and Mechanical Properties
The chemical requirements are identical for both designations:
| Element | C max | Mn max | P max | S max | Si | Ni |
|---|---|---|---|---|---|---|
| Limit (%) | 0.13 | 0.90 | 0.035 | 0.04 | 0.15–0.30 | 8.50–9.50 |
Key mechanical requirements (both specifications):
| Property | Requirement |
|---|---|
| Tensile strength | 690–825 MPa (100–120 ksi) |
| Yield strength, min (0.2% offset) | 585 MPa (84.8 ksi) |
| Elongation in 50 mm, min | 20% |
| Charpy V-notch, transverse, −196 °C, min | 27 J |
| Lateral expansion, min | 0.381 mm |
| Heat treatment | Quenched and tempered |
The low carbon and manganese keep the steel weldable and clean, while the 9% nickel content is what delivers the cryogenic toughness.
What the "S" Prefix Changes
ASME SA553 Type 1 is the same steel with the same chemistry, mechanical properties and heat treatment. The difference is the issuing body: ASME adopts the ASTM specification into the Boiler and Pressure Vessel Code, Section II, Part A, and adds the S prefix. When a vessel is designed, fabricated and stamped under ASME BPVC Section VIII, the material documentation must in most jurisdictions carry the ASME designation. That is the single biggest reason a buyer specifies SA553 rather than A553: regulatory compliance, not any metallurgical difference.
Correcting Common Misunderstandings
"SA553 is a higher grade" is false: the chemical and mechanical requirements are identical. "ASTM A553 is less strict" is false: both require the same impact testing at −196 °C and the same quenched and tempered condition. "SA553 must be used for any pressure vessel" depends on jurisdiction: many countries accept ASTM material certifications for vessels that are not code-stamped. "ASME material costs more" is partially true: ASME traceability and documentation add cost, but the steel itself is the same.
Which Designation Should You Choose?
Choose ASTM A553 Type 1 when the project requires ASTM material compliance only, when pressure vessel code stamping is not mandatory, or for general cryogenic engineering applications. Choose ASME SA553 Type 1 when the project falls under ASME BPVC regulations, when code certification is required, or when international EPC standards demand it, for example LNG terminal projects. In both cases the acceptance criteria on the mill test certificate should be checked against the current edition of the governing standard.
Frequently Asked Questions
Are ASTM A553 Type 1 and ASME SA553 Type 1 the same material?
Yes. The composition, mechanical properties, quenched and tempered heat treatment and impact testing requirements are identical. Only the publishing body, and therefore the certification path, differs.
What is A553 Type 1 material used for?
It is used in the fabrication of cryogenic pressure vessels, primarily LNG storage tanks and related cryogenic containment operating at temperatures down to −196 °C.
Is there a price difference between A553 and SA553 plates?
ASME-certified plates typically carry a premium over ASTM-only plates because of the additional documentation, auditing and traceability requirements, even though the steel is metallurgically identical. For budget-sensitive, non-code projects, ASTM certification is the cost-effective route.
What is the difference between Type I, Type II and Type III?
Type I is the 9% nickel grade (8.50–9.50% Ni) tested at −196 °C and is the most widely used for LNG. Type II is an 8% nickel grade tested at −170 °C. Type III is a lower-nickel variant introduced for cost reduction; its nickel level and test temperature follow the current edition of A553/A553M.
What is the impact requirement for A553 Type 1?
The requirement is a minimum of 27 J average on transverse Charpy V-notch specimens at −196 °C, with a minimum lateral expansion of 0.381 mm. Acceptance values should be verified against the current standard edition.
Can A553 Type 1 plate be welded?
Yes. The grade is designed for welded pressure vessel fabrication and is compatible with nickel-based welding consumables. Welding procedures should be qualified for cryogenic service.
