DNV AH40 Steel Plate | NV A40 Marine Steel Plate

Technical Reviewer: Jack | SHH STEEL Material Solutions Department · Updated: 2026-10-27

DNV AH40, officially stamped NV A40 on mill-approved plate, is a higher-strength hull structural steel under DNV rules for classification – Ships, which implement IACS UR W11 for the AH–FH 32/36/40 family. Strength level 40 means minimum yield 390 N/mm², tensile 510–650 N/mm² and elongation 20 % min. (A5). The letter AH fixes Charpy V-notch testing at 0 °C. In commercial enquiries it is called DNV AH40 or NV A40 marine steel plate.

Equivalent grades: DNV NV A40 ≈ ASTM A131 Grade AH40 ≈ ABS AH40 ≈ LR AH40 ≈ BV AH40 ≈ CCS A40 / AH40 ≈ NK KA40 ≈ KR RA40 ≈ RINA AH40 ≈ GB 712 Grade AH40 (all class-approved, stamped by the issuing society).

NV A40 is selected when scantlings need the higher yield of the 40 band and the material class assigns 0 °C toughness. Ordinary-strength NV A–E stay at 235 N/mm² yield and cannot replace AH40 without a drawing change. Within the 40 band, letter choice is toughness: AH 0 °C → DH −20 °C → EH −40 °C → FH −60 °C; within the AH letter, strength steps 32 → 36 → 40 raise yield from 315 to 355 to 390 N/mm².

Plates that pass mill tests under DNV survey are die-stamped or stencilled NV A40 (plus Z or U where through-thickness or ultrasonic requirements apply) and are supplied with a mill certificate the DNV Surveyor endorses. SHH STEEL supplies NV A40 from Chinese mills that hold DNV works approval for the grade, from stock in common sizes or from a mill rolling cycle, with DNV survey arranged at the mill.

Size range. Common market thicknesses for AH40 are about 6–80 mm (heavier plates available as per mill approval), widths 1500–3500 mm. Exact maximum thickness for a given delivery condition is as per standard and mill certificate / DNV works approval. Ask for confirmation above 100 mm.

Product (check) analysis column: DNV rules specify heat (ladle) limits; no numeric product-analysis tolerance is tabulated in the rule text reviewed, so product (check) limits are agreed on the order or taken from the approved mill specification and certificate.

Source: IACS UR W11 higher-strength chemistry tables (ladle samples) — the chemistry DNV applies to NV A40. AH/DH/EH share one chemistry column; FH is tighter on C, P, S and adds N control with higher Ni allowance. Toughness is differentiated by impact temperature and supply routes, not by separate C/Mn caps within AH/DH/EH. Product (check) analysis numeric tolerances are not tabulated in UR W11; when required, agree tolerances at enquiry. TMCP steels must also meet the applicable Ceq / Pcm limits on the mill approval — ask for Ceq on the certificate.

Alternative flat-specimen elongations by thickness (indicative UR W11 / industry table for strength 40):

Same tensile band applies to AH/DH/EH/FH 40; only impact temperature and chemistry group (FH vs AH/DH/EH) change across the letter.

Source: IACS UR W11 impact table for higher-strength Grade AH40 (full-size; either direction acceptable unless specified). Energies rise with thickness — a 60 mm plate must meet higher values than a 20 mm plate at the same 0 °C. Condition of supply and impact lot size depend on grain-refining practice and thickness (AR/CR/N/TM/QT as permitted). For TMCP AH40, respect Ceq caps ≈ 0.40 % (t≤50) / 0.42 % (50

DNV applies IACS UR W13 thickness tolerances unless the PO states otherwise (often 0.3 mm minus class — confirm on PO; see UNCERTAIN). Plus/flatness/width/length per agreed standard (ASTM A6 or EN 10029). Surface quality per EN 10163 or equivalent accepted by DNV; state primer/surface class on receipt if needed.

Quantities are approximate and change daily (indicative — confirm before booking); all stock plates carry NV A40 marking and DNV-endorsed mill certificates when sold as DNV class plate. Sizes outside the table (for example 3000 mm width, 60–100 mm thickness, or fixed lengths for a cutting plan) are produced in the next mill rolling cycle, typically 3–6 weeks including DNV survey. Send your size list and we will reply with what is in stock and what must be rolled.

Packing. Plates are bundled by size with steel strapping, marked with heat number, grade and DNV stamp, and shipped in containers (up to about 11.8 m) or break bulk for longer plates.

These are comparisons, not substitutions. Multi-class stamps require joint survey before rolling.

Pick AH40 when the drawing specifies higher-strength grade AH40 (or the society equivalent). Do not substitute ordinary Grade A/B unless the designer recalculates scantlings — yield differs (390 vs 235). Within the 40 band, letter choice is toughness: AH 0 °C → DH −20 °C → EH −40 °C → FH −60 °C. Within the AH letter, strength steps 32 → 36 → 40 raise yield from 315 to 355 to 390 N/mm².

For yields above 390 N/mm² DNV / IACS move to extra-high strength (UR W16 naming AH420… / NV A420…).

When DNV NV A40 is the right choice: typical uses are higher-strength hull girder plating (deck, bottom, side shell) of bulk carriers, tankers and container ships in normal service where 0 °C toughness suffices. The Charpy temperature (0 °C) is fixed by the letter, and the strength by the number (ReH 390 N/mm²). Pick the strength from the scantling calculation and the letter from the material class and design temperature on the approved drawing.

Typical uses: higher-strength hull girder plating (deck, bottom, side shell) of bulk carriers, tankers and container ships in normal service where 0 °C toughness suffices; weight-saving vs ordinary-strength plate in large tankers, bulkers and container ships. See offshore platform steel plates when primary offshore grades apply.

Welding: higher-strength hull steels need approved higher-strength consumables matched to 0 °C weld-metal toughness; preheat and heat input follow the approved WPS and often track Ceq/Pcm from the mill certificate. TMCP AH40 must respect the Ceq caps noted above. Cutting by oxy-fuel/plasma/laser is routine; thick FH plate may need hydrogen control — follow mill recommendations.

Processing notes for NV A40: cold forming is routine within normal shipyard radii. Line heating and fairing of TMCP plate should stay within the temperature limits recommended by the mill, because overheating can reduce the strength gained in controlled rolling. Check the delivery condition on the certificate before planning hot forming.

Every plate is tested and marked at the mill under DNV survey; the mill certificate lists heat number, ladle chemistry, Ceq where applicable, tensile results (ReH ≥ 390 N/mm², Rm 510–650 N/mm², A ≥ 20 %), Charpy at 0 °C, delivery condition and plate numbers, endorsed by the Surveyor. Optional EN 10204 3.2, UT (U), Z-direction, multi-class.

On receipt: verify NV A40 stamp, 0 °C impact data, energies for the delivered thickness band, thickness within UR W13 / PO tolerance, DNV endorsement present.

Charpy acceptance for NV A40 by thickness (IACS UR W11; actual results as per standard and mill certificate):

If UT or 3.2 was ordered, check the UT report and inspector’s plate list as well.

• Ordering “DNV 40” without the letter (AH/…) — toughness class missing
• Accepting ordinary-strength Grade A/B certificates for a AH40 PO
• Ignoring TMCP Ceq caps on TM plate
• Substituting a different letter (e.g. AH for AH) without drawing approval
• Coil-cut plate without coil approval
• Missing DNV endorsement on the MTC

Write grade, delivery condition, impact temperature and certificate type into the PO.

Specify DNV AH40 (NV A40), delivery condition (AR/CR/N/TM/QT as applicable), thickness × width × length × qty, Z/U, multi-class, certificate type, port. Send to SHH STEEL.

Sample PO line: “Steel plate to DNV rules for classification – Ships, Grade AH40 (NV A40), delivery condition [AR/CR/N/TM/QT], 20 × 2500 × 12000 mm, 30 pcs, marked NV A40, certificate endorsed by DNV Surveyor, EN 10204 3.2 [if required], UT [if required], CIF [port].”

DNV AH40 / NV A40 is higher-strength hull steel under DNV rules and IACS UR W11: yield 390 N/mm², tensile 510–650 N/mm², Charpy at 0 °C, marking NV A40. Lock on the order: delivery condition, impact lot size, TMCP Ceq if TM, product analysis if needed, multi-class and 3.2.

SHH STEEL supplies NV A40 plate rolled by Chinese mills that hold DNV works approval for the grade, so every plate carries the NV A40 stamp and a Surveyor-endorsed certificate traceable to its heat. Common thicknesses are available from stock; other sizes are scheduled into the mill rolling cycle with DNV survey arranged at the mill. On request we add EN 10204 3.2 certificates with third-party witness (TÜV, SGS, BV or another agency) and joint certification with ABS, LR, BV, CCS, NK, KR or RINA.

We accept T/T or L/C payment, with inspection before the balance is paid. Small quantities in several sizes, or NV A40 mixed with NV A/B/D/E or other AH–FH sizes, can be combined in one container. A dedicated coordinator sends production and shipping updates with photos, and our own workshop cuts to size, bevels, drills and machines plates before shipment so they arrive ready for fabrication.

Request a quotation: send SHH STEEL the grade (NV A40 / DNV AH40), thickness, width, length, quantity per size and destination port, plus any multi-class, Z/U or 3.2 certificate requirement. We reply with price, available stock and lead time.