ASTM A553 Type III | SA553 7% Nickel Steel Plate

ASTM A553 Type III steel plate, also written as ASME SA553 Type III, A553 Type III 7% Ni plate, SA553M Type III, is a 7% nickel (7% Ni steel (reduced-nickel LNG steel)) alloy steel plate supplied in the water quenched and tempered condition for welded pressure vessels at low temperature. Gangsteel (HENAN GANG IRON AND STEEL) produces and exports A553/SA553 Type III plates cut to size with Charpy impact tests at -320°F [-196°C], UT and EN 10204 3.1/3.2 mill certificates.

Data source: ASTM A553/A553M-22 / ASME SA553/SA553M (BPVC II-A 2023, identical with A553/A553M-17) (Pressure Vessel Plates, Alloy Steel, Quenched and Tempered 7, 8, and 9% Nickel). The current edition defines three types: Type I (9% Ni), Type II (8% Ni) and Type III (7% Ni). General requirements follow ASTM A20/A20M. Verify the contracted edition and supplementary requirements before ordering.

ASTM A553 Type III Chemical Composition

Silicon may be below the minimum for Types I and II when total Al is 0.030% min or acid-soluble Al is 0.025% min. Vacuum carbon-deoxidized steel per A20 S17 may modify Si limits when specified.

ASTM A553 Type III Mechanical Properties

Elongation adjustments follow A20/A20M. Yield may be determined by the 0.005 in./in. extension-under-load method by agreement. Drop-weight tests per S-supplement when ordered for LNG tank projects.

Heat Treatment and Delivery Condition

Per A553/A553M section 5.2 (SA-553 in ASME BPVC II-A): heat to 1475–1700°F [800–925°C] and quench in water; temper Type III at 1000–1125°F [540–615°C] (Types I and II 565–635°C, Type III 540–615°C), holding at least 30 min/in. [1.2 min/mm] of thickness and not less than 15 min, then cool in air or water at not less than 300°F/h [165°C/h]. Before tempering, an optional intermediate heat treatment at 1205–1330°F [650–720°C] for Type III may be applied to enhance elongation and notch toughness. Plates should not be handled with lifting magnets after heat treatment where residual magnetism matters.

Thickness, Size and Inspection

A553 sets no fixed maximum thickness; it is limited by the ability to meet mechanical properties. Gangsteel supplies widths 1500–3500 mm, lengths up to 12 m, thickness 5–100 mm (typical LNG range 6–50 mm), ultrasonic testing to A435/A577/A578, residual magnetism checks, and third-party inspection (BV, SGS, TUV, Lloyd's).

Applications of ASTM A553 Type III

LNG storage tanks and other -196°C service where owners accept the lower-nickel, Mo-Nb microalloyed 7% Ni steel as a cost-saving alternative to 9% Ni.

Equivalent / Related Grades of ASTM A553 Type III

Equivalents are engineering references only; chemistry, heat treatment and impact temperature differ. Dual certification requires the stricter combined limits on the PO and MTC.

FAQ about ASTM A553 Type III Steel Plate

What is ASTM A553 Type III steel plate?

ASTM A553 Type III is a 7% nickel alloy steel plate supplied water quenched and tempered for welded pressure vessels in cryogenic service. It is ordered as ASTM A553/A553M or ASME SA553/SA553M Type III. Full tables are on the ASTM A553 Type III page.

What is the chemical composition of A553 Type III?

Heat analysis: C 0.13 max, Mn 0.90 max, P 0.010 max, S 0.010 max, Si 0.05–0.30 (heat and product), Ni 6.50–7.50, Mo 0.10–0.30, Nb 0.03 max.

What are the yield and tensile strength of A553 Type III?

Tensile strength 100–120 ksi [690–825 MPa], 0.2% offset yield 85 ksi [585 MPa] min, elongation 20% min in 2 in. [50 mm]. All three A553 types share these values.

At what temperature is A553 Type III impact tested?

Charpy V-notch tests are made at -320°F [-196°C] unless another temperature is agreed. Acceptance is 0.015 in. [0.38 mm] lateral expansion min (Charpy V-notch, transverse), specimens transverse to the final rolling direction.

What is the difference between A553 Type I, Type II and Type III?

Type I is 9% Ni (8.50–9.50%) for -196°C; Type II is 8% Ni (7.50–8.50%) for -170°C; Type III is 7% Ni (6.50–7.50%) with Mo 0.10–0.30% and Nb 0.03% max, tighter P/S 0.010% max, tested at -196°C. Other types: A553 Type I / A553 Type II.

How is A553 Type III heat treated?

Per A553/A553M 5.2, plates are heated to 1475–1700°F [800–925°C] and water quenched, then tempered at 1000–1125°F [540–615°C] for Type III, held at least 30 min/in. [1.2 min/mm] (min 15 min) and cooled in air or water at not less than 300°F/h [165°C/h]. An optional intermediate heat treatment at 1205–1330°F [650–720°C] may be applied before tempering. Gangsteel ships QT with the heat treatment record on the MTC.

What is the difference between ASTM A553 and ASTM A353?

Both cover 9% Ni plate. A553 Type I is quenched and tempered; ASTM A353 / SA353 is double normalized and tempered. Tensile is 100–120 ksi for both, but A553 QT gives higher yield (85 vs 75 ksi) and is usually chosen for thicker LNG shell courses.

Is ASME SA553 the same as ASTM A553?

SA553 is the ASME Boiler and Pressure Vessel Code Section II adoption of A553 and is technically identical. Order SA553 when the vessel will be code stamped; dual marked ASTM A553/ASME SA553 plates are common.

Why should magnets not be used to lift A553 Type III plate?

Nickel steels are easily magnetized. Residual magnetism from magnet lifting after heat treatment causes arc blow during welding, so Gangsteel handles and ships these plates with clamps or slings and checks residual magnetism when ordered.

What thickness and inspection can Gangsteel supply for A553 Type III?

Maximum thickness is limited only by meeting the mechanical properties; typical supply is 5–50 mm for LNG shells and up to about 100 mm on request. UT to A435, A577 or A578, EN 10204 3.1 or 3.2 certificates and third-party inspection are available.

Related ASTM A553 / Low Temperature Pressure Vessel Grades

ASTM A553 / SA553 Hub | A553 Type I | A553 Type II | A553 Type III | ASTM A353 | ASTM A203 | A203 Grade E | GB/T 3531 | ASTM A533 | ASTM A537 | ASTM A516 | Pressure Vessel Steel Plate