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NK A70 steel plate, also written as KA70, K A70, ClassNK A70, NK Grade A70 or market names such as AH69 / AQ70, is the extra-high-strength hull structural steel of ClassNK (Nippon Kaiji Kyokai) Rules for the Survey and Construction of Steel Ships (IACS UR W16 extra-high-strength family) with 690 MPa minimum yield, 770-940 MPa tensile strength and Charpy V-notch toughness at 0°C [32°F]. In the grade name, "A" is the toughness class, and "70" is the site strength label for about 690 MPa yield (ABS AQ70 family). Gangsteel, a steel plate exporter, supplies NK A70 / KA70 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 ClassNK hull structural steel rules, cross-checked with LR AH69 / ABS AQ70 sibling pages on gangsteel.net. Official mill/certificate grade is typically KA70 (K A70); NK A70 names the same class on this site. Verify the current ClassNK edition before ordering.
| Element | C | Mn | Si | P | S | Al (acid sol.) |
|---|---|---|---|---|---|---|
| NK A70, % | 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 |
| NK A70, % | 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 / ClassNK 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 | 0.21 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.
| Grade | Yield strength, min | Tensile strength | Elongation, min |
|---|---|---|---|
| NK A70 / KA70 | 690 MPa [100 ksi] | 770-940 MPa [112-136 ksi] | 14% |
Per IACS UR W16 / ClassNK 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 | 0°C [32°F] | 69 J | 46 J |
| 50<t≤70 mm | 0°C [32°F] | 69 J | 46 J |
| 70<t≤100 mm | 0°C [32°F] | 69 J | 46 J |
Per IACS UR W16 / ClassNK 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. A-class (K A70 / AQ70) 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, ClassNK survey.
Extra-high-strength NK A/D/E/F 43/47/51/56/63/70 plates (about 420-690 MPa family) 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 |
|---|---|
| NK (ClassNK) | NK A70 / KA70 (LR AH69 / ABS AQ70) |
| LR (Lloyd's Register) | LR AH69 steel plate |
| ABS | ABS AQ70 steel plate |
| CCS | CCS A690 steel plate |
| GL | GL A690 steel plate |
| DNV | DNV A690 steel plate |
| BV | BV A690 steel plate |
| KR | KR A70 steel plate |
| RINA | RINA A690 steel plate |
IACS societies align extra-high-strength hull grades under UR W16; naming differs (NK A70, LR AH69, ABS AQ70, DNV A690). Dual certification is common when ordered that way.
It is an extra-high-strength hull structural steel under ClassNK Rules (IACS UR W16 extra-high-strength family), with 690 MPa minimum yield, 770-940 MPa tensile strength and Charpy toughness at 0°C [32°F].
NK (ClassNK) is Nippon Kaiji Kyokai. The K prefix (KA70) is the ClassNK mill designation. The letter A is the toughness class (Charpy at 0°C [32°F]), and 70 is the yield-strength level in MPa. Market/LR naming often uses AH69; ABS often uses AQ70. This site uses ABS-like numbers (A43…A70), corresponding to about 690 MPa (ABS AQ70 / LR AH69 / DNV A690 family); there are no A420 paths under /nk/.
Minimum 690 MPa (100 ksi), tensile 770-940 MPa (112-136 ksi), elongation about 14% min (for the common thickness range).
Charpy V-notch at 0°C [32°F]. Typical longitudinal average minimum is 69 J (transverse 46 J) for the tabulated thickness range on this grade page.
Same 690 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.
NK A40 is UR W11 higher-strength (390 MPa). NK A70 is UR W16 extra-high-strength (690 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 ClassNK 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. A-class (K A70 / AQ70) 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, ClassNK survey.
Common supply is about 6-100 mm (thicker by agreement under UR W16 / ClassNK rules), 1500-4000 mm wide and 6000-18000 mm long.
NK Grade A steel plate | NK Grade B steel plate | NK Grade D steel plate | NK Grade E steel plate | NK A32 steel plate | NK A36 steel plate | NK A40 steel plate | NK D32 steel plate | NK D36 steel plate | NK D40 steel plate | NK E32 steel plate | NK E36 steel plate | NK E40 steel plate | NK F32 steel plate | NK F36 steel plate | NK F40 steel plate | NK A43 steel plate | NK A47 steel plate | NK A51 steel plate | NK A56 steel plate | NK A63 steel plate | NK D43 steel plate | NK D47 steel plate | NK D51 steel plate | NK D56 steel plate | NK D63 steel plate | NK D70 steel plate | NK E43 steel plate | NK E47 steel plate | NK E51 steel plate | NK E56 steel plate | NK E63 steel plate | NK E70 steel plate | NK F43 steel plate | NK F47 steel plate | NK F51 steel plate | NK F56 steel plate | NK F63 steel plate | NK F70 steel plate
NK A70 / KA70 corresponds to extra-high-strength counterparts under other IACS societies (LR AH69, ABS AQ70, etc.): LR AH69 steel plate, ABS AQ70 steel plate, CCS A690 steel plate, GL A690 steel plate, DNV A690 steel plate, BV A690 steel plate, KR A70 steel plate, RINA A690 steel plate.
NK E36 (KE36) shipbuilding steel plate: 355 MPa yield, 490-620 MPa tensile, Charpy at -40C, chemistry and equiv
NK D36 (KD36) shipbuilding steel plate: 355 MPa yield, 490-620 MPa tensile, Charpy at -20C, chemistry and equiv
NK A36 (KA36) shipbuilding steel plate: 355 MPa yield, 490-620 MPa tensile, Charpy at 0C, chemistry and equival
NK F32 (KF32) shipbuilding steel plate: 315 MPa yield, 440-590 MPa tensile, Charpy at -60C, chemistry and equiv
