RINA A550 Steel Plate | A550 Shipbuilding Steel Plate

RINA A550 steel plate, also written as RI/A550, RINA Grade A550, Registro Italiano Navale A550 or market names such as AH55 / AQ56, is the extra-high-strength hull structural steel of RINA Rules for the Classification of Ships (IACS UR W16 extra-high-strength family) with 550 MPa minimum yield, 670-830 MPa tensile strength and Charpy V-notch toughness at 0°C [32°F]. In the grade name, "A" is the toughness class, and "550" is the yield-strength level in MPa (not AH550). Gangsteel, a steel plate exporter, supplies RINA A550 / RI/A550 plates cut to size for shipbuilding, offshore platforms and marine structures.

Data source: Per IACS UR W16 (extra-high-strength hull structural steel) as adopted in RINA (Registro Italiano Navale) hull structural steel rules, cross-checked with LR AH55 / ABS AQ56 sibling pages on gangsteel.net. Official mill/certificate grade is RINA A550 (RI/A550). Verify the current RINA edition before ordering.

RINA A550 Chemical Composition (Heat Analysis)

 

Element	C	Mn	Si	P	S	Al (acid sol.)
RINA A550, %	0.21 max	1.70 max	0.10-0.55	0.035 max	0.035 max	0.015 min
Element	N	Nb	V	Ti	B	Notes
RINA A550, %	0.020 max	0.02-0.05	0.04-0.10	0.02 max	0.005 max	Ni/Cu/Cr/Mo per delivery condition (N/TM/QT) in UR W16

Per IACS UR W16 / RINA extra-high-strength rules. Exact maxima for Ni, Cu, Cr and Mo depend on delivery condition (N/NR, TM or QT). Carbon equivalent / CET / Pcm limits apply by thickness and condition; confirm on the mill certificate and current rule edition.

Product Analysis (Check Analysis)

 

When product analysis is required, apply ASTM A6/A6M Table A permitted variations to the heat limits unless the element is min-only or not listed in Table A.

Element	Heat analysis limit	Product analysis (heat ± A6)
C	0.21 max	0.25 max
Mn	1.70 max	see A6 Table A vs heat upper limit
Si	0.10-0.55	0.05–0.61 (approx. A6)
P	0.035 max	0.045 max
S	0.035 max	0.045 max
Al (acid sol.)	0.015 min	no A6 Table A tolerance; product value not tabulated
N	0.020 max	0.025 max (typical A6 +0.005)
Nb	0.02-0.05	0.010–0.060
V	0.04-0.10	0.030–0.110
Ti	0.02 max	0.03 max
B	0.005 max	product analysis often not applicable

Product analysis applies only when specified; for a range, results may not vary both above and below it.

RINA A550 Mechanical Properties

 

Grade	Yield strength, min	Tensile strength	Elongation, min
RINA A550	550 MPa [80 ksi]	670-830 MPa [97-120 ksi]	16%

Per IACS UR W16 / RINA rules (common t≤50 mm values). Yield may step down for thicker plates per UR W16; confirm thickness-dependent values on the order.

Charpy V-Notch Impact Requirements (0°C [32°F])

 

Thickness	Test temperature	Longitudinal, avg min	Transverse, avg min
t≤50 mm	0°C [32°F]	55 J	37 J
50<t≤70 mm	0°C [32°F]	55 J	37 J
70<t≤100 mm	0°C [32°F]	55 J	37 J

Per IACS UR W16 / RINA extra-high-strength practice. Average of three full-size specimens; transverse values apply when required. Thicker plates by agreement.

Delivery Condition and Deoxidation

Deoxidation: Killed, fine-grain practice. Delivery condition: typically TMCP or QT for extra-high-strength plates; N/NR may apply at lower extra-high levels per rules. A-class (A550) grades may be as-rolled, controlled rolled, normalized or TMCP depending on thickness; thicker plates usually N or TMCP. Optional extras: UT, Z15/Z25/Z35, RINA survey.

Thickness Coverage

Extra-high-strength RINA A/D/E/F 420-690 plates are commonly supplied from about 6 mm to 100 mm thick (thicker by agreement under UR W16). Width 1500-4000 mm and length 6000-18000 mm are typical.

Equivalent Steel Grades of RINA A550

 

Society / Standard	Equivalent grade
RINA (Registro Italiano Navale)	RINA A550 steel plate (RI/A550; LR AH55 / ABS AQ56)
LR (Lloyd's Register)	LR AH55 steel plate
ABS	ABS AQ56 steel plate
CCS	CCS A550 steel plate
GL	GL A550 steel plate
DNV	DNV A550 steel plate
NK	NK A56 steel plate
KR	KR A56 steel plate
BV	BV A550 steel plate

IACS societies align extra-high-strength hull grades under UR W16; naming differs (RINA A550, LR AH55, ABS AQ56). Dual certification is common when ordered that way.

FAQ about RINA A550 Steel Plate

What is RINA A550 steel plate?

It is an extra-high-strength hull structural steel under RINA Rules (IACS UR W16 extra-high-strength family), with 550 MPa minimum yield, 670-830 MPa tensile strength and Charpy toughness at 0°C [32°F]. The mill certificate grade is RINA A550 (RI/A550).

What does RINA A550 / RI/A550 stand for?

RINA is Registro Italiano Navale (RI on certificates). The letter A is the toughness class (Charpy at 0°C [32°F]), and 550 is the yield-strength level in MPa. Market/LR naming often uses AH55; ABS often uses AQ56. Note: RINA does not use AH550 — the grade is A550, not AH550.

What is the yield strength of RINA A550?

Minimum 550 MPa (80 ksi), tensile 670-830 MPa (97-120 ksi), elongation about 16% min (for the common thickness range).

What is the impact test temperature for RINA A550?

Charpy V-notch at 0°C [32°F]. Typical longitudinal average minimum is 55 J (transverse 37 J) for the tabulated thickness range on this grade page.

What is the difference between RINA A550, D550, E550 and F550?

Same 550 MPa strength class. Toughness class differs: A at 0°C, D at -20°C, E at -40°C, F at -60°C. Chemistry (C, P, S, Mn) is tightened for colder classes.

How does RINA A550 differ from higher-strength RINA AH40?

RINA AH40 is UR W11 higher-strength (390 MPa). RINA A550 is UR W16 extra-high-strength (550 MPa) with different chemistry and delivery practice (often TM/QT).

Is RINA A550 the same as LR AH55 or ABS AQ56?

They are IACS counterparts in the extra-high-strength family; exact chemistry/delivery options differ by society edition. Dual certification is available when surveys are arranged.

Is RINA A550 weldable?

Weldable with approved procedures for extra-high-strength ship steel. Preheat, heat input and consumable matching are critical; follow the mill WPS and RINA welding requirements.

What heat treatment is required for RINA A550?

Extra-high-strength grades are typically delivered TMCP or quenched and tempered (QT), sometimes normalized/normalized-rolled depending on strength level and thickness. A-class (A550) grades may be as-rolled, controlled rolled, normalized or TMCP depending on thickness; thicker plates usually N or TMCP. Optional extras: UT, Z15/Z25/Z35, RINA survey.

What thickness is available for RINA A550?

Common supply is about 6-100 mm (thicker by agreement under UR W16 / RINA rules), 1500-4000 mm wide and 6000-18000 mm long.

Other RINA Steel Plate Grades

RINA Grade A steel plate | RINA Grade B steel plate | RINA Grade D steel plate | RINA Grade E steel plate | RINA AH32 steel plate | RINA AH36 steel plate | RINA AH40 steel plate | RINA DH32 steel plate | RINA DH36 steel plate | RINA DH40 steel plate | RINA EH32 steel plate | RINA EH36 steel plate | RINA EH40 steel plate | RINA FH32 steel plate | RINA FH36 steel plate | RINA FH40 steel plate | RINA A420 steel plate | RINA A460 steel plate | RINA A500 steel plate | RINA A620 steel plate | RINA A690 steel plate | RINA D420 steel plate | RINA D460 steel plate | RINA D500 steel plate | RINA D550 steel plate | RINA D620 steel plate | RINA D690 steel plate | RINA E420 steel plate | RINA E460 steel plate | RINA E500 steel plate | RINA E550 steel plate | RINA E620 steel plate | RINA E690 steel plate | RINA F420 steel plate | RINA F460 steel plate | RINA F500 steel plate | RINA F550 steel plate | RINA F620 steel plate | RINA F690 steel plate

Equivalent Class Society Grades

RINA A550 corresponds to extra-high-strength counterparts under other IACS societies (LR AH55, ABS AQ56, etc.): LR AH55 steel plate, ABS AQ56 steel plate, CCS A550 steel plate, GL A550 steel plate, DNV A550 steel plate, NK A56 steel plate, KR A56 steel plate, BV A550 steel plate, RINA A550 steel plate.