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RINA D550 steel plate, also written as RI/D550, RINA Grade D550, Registro Italiano Navale D550 or market names such as DH55 / DQ56, 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 -20°C [-4°F]. In the grade name, "D" is the toughness class, and "550" is the yield-strength level in MPa (not AH550). Gangsteel, a steel plate exporter, supplies RINA D550 / RI/D550 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 DH55 / ABS DQ56 sibling pages on gangsteel.net. Official mill/certificate grade is RINA D550 (RI/D550). Verify the current RINA edition before ordering.
| Element | C | Mn | Si | P | S | Al (acid sol.) |
|---|---|---|---|---|---|---|
| RINA D550, % | 0.20 max | 1.70 max | 0.10-0.55 | 0.030 max | 0.030 max | 0.015 min |
| Element | N | Nb | V | Ti | B | Notes |
| RINA D550, % | 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.
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 | 0.20 max | 0.24 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 | 0.030 max | 0.040 max |
| S | 0.030 max | 0.040 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.
| Grade | Yield strength, min | Tensile strength | Elongation, min |
|---|---|---|---|
| RINA D550 | 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.
| Thickness | Test temperature | Longitudinal, avg min | Transverse, avg min |
|---|---|---|---|
| t≤50 mm | -20°C [-4°F] | 55 J | 37 J |
| 50<t≤70 mm | -20°C [-4°F] | 55 J | 37 J |
| 70<t≤100 mm | -20°C [-4°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.
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. D-class (D550) grades are typically normalized or TMCP; controlled-rolled delivery may apply within rule limits. Optional extras: UT, Z15/Z25/Z35, RINA survey.
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.
| Society / Standard | Equivalent grade |
|---|---|
| RINA (Registro Italiano Navale) | RINA D550 steel plate (RI/D550; LR DH55 / ABS DQ56) |
| LR (Lloyd's Register) | LR DH55 steel plate |
| ABS | ABS DQ56 steel plate |
| CCS | CCS D550 steel plate |
| GL | GL D550 steel plate |
| DNV | DNV D550 steel plate |
| NK | NK D56 steel plate |
| KR | KR D56 steel plate |
| BV | BV D550 steel plate |
IACS societies align extra-high-strength hull grades under UR W16; naming differs (RINA D550, LR DH55, ABS DQ56). Dual certification is common when ordered that way.
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 -20°C [-4°F]. The mill certificate grade is RINA D550 (RI/D550).
RINA is Registro Italiano Navale (RI on certificates). The letter D is the toughness class (Charpy at -20°C [-4°F]), and 550 is the yield-strength level in MPa. Market/LR naming often uses DH55; ABS often uses DQ56. Note: RINA does not use AH550 — the grade is D550, not AH550.
Minimum 550 MPa (80 ksi), tensile 670-830 MPa (97-120 ksi), elongation about 16% min (for the common thickness range).
Charpy V-notch at -20°C [-4°F]. Typical longitudinal average minimum is 55 J (transverse 37 J) for the tabulated thickness range on this grade page.
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.
RINA AH40 is UR W11 higher-strength (390 MPa). RINA D550 is UR W16 extra-high-strength (550 MPa) with different chemistry and delivery practice (often TM/QT).
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.
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.
Extra-high-strength grades are typically delivered TMCP or quenched and tempered (QT), sometimes normalized/normalized-rolled depending on strength level and thickness. D-class (D550) grades are typically normalized or TMCP; controlled-rolled delivery may apply within rule limits. Optional extras: UT, Z15/Z25/Z35, RINA survey.
Common supply is about 6-100 mm (thicker by agreement under UR W16 / RINA rules), 1500-4000 mm wide and 6000-18000 mm long.
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 A550 steel plate | RINA A620 steel plate | RINA A690 steel plate | RINA D420 steel plate | RINA D460 steel plate | RINA D500 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
RINA D550 corresponds to extra-high-strength counterparts under other IACS societies (LR DH55, ABS DQ56, etc.): LR DH55 steel plate, ABS DQ56 steel plate, CCS D550 steel plate, GL D550 steel plate, DNV D550 steel plate, NK D56 steel plate, KR D56 steel plate, BV D550 steel plate, RINA D550 steel plate.
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