DNV Grade A Steel Plate | NV A Marine Steel Plate

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

DNV Grade A, officially stamped NV A on mill-approved plate, is the base ordinary-strength (normal-strength) hull structural steel under DNV rules for classification – Ships, which implement the IACS Unified Requirement W11 for normal and higher strength hull structural steels. In commercial enquiries it is also called DNV Grade A or NV A marine steel plate. It has a minimum yield strength of 235 N/mm², a tensile strength of 400–520 N/mm² and 22 % minimum elongation (A5). Among the four normal-strength grades (A, B, D, E), Grade A is the only one for which Charpy V-notch impact testing is generally not required on plates up to and including 50 mm.

Equivalent grades: DNV NV A ≈ ASTM A131 Grade A ≈ ABS A ≈ LR Grade A ≈ BV Grade A ≈ CCS Grade A ≈ NK KA ≈ KR RA ≈ RINA Grade A ≈ GB 712 Grade A (all class-approved, stamped by the issuing society).

Because NV A carries no low-temperature toughness guarantee at ordinary thicknesses, it is used where the hull member stays in temperate service and the approved drawing allows Grade A: inner bottom and internal structure of small and medium vessels, superstructures, deckhouses, non-critical bulkheads, inland and coastal barges, pontoons, hatch covers and many shipyard fittings. Where the drawing calls for NV B, NV D or NV E in a strake, NV A cannot be substituted; the reverse (supplying B, D or E for A) is normally accepted because the tougher grades meet every Grade A tensile and chemistry requirement.

Plates that pass mill tests under DNV survey are die-stamped or stencilled NV A (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 DNV NV A plate 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. NV A is rolled on wide plate mills in China from about 5 mm to 100 mm and more, widths 1500–3500 mm and lengths up to about 18 m depending on mill; 6–25 mm plate in 1800–2500 mm width is the bulk of the market. Plates under about 6 mm are often cut from DNV-approved hot-rolled coil, which needs separate approval of the coil process. Ask for confirmation for plates over 100 mm or wider than 3200 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 Table 1 (ladle samples) for normal-strength Grade A — the chemistry DNV applies to NV A hull plate. Heat (ladle) analysis is determined by the mill on each heat and must meet Table 1. Product (check) analysis on the finished plate is not given numeric tolerances in UR W11 itself; W11 4.2 accepts the manufacturer’s declared analysis subject to occasional Surveyor checks. When a purchaser or Surveyor requires product analysis on the certificate, ask at enquiry and record the agreed tolerances (national standard or mill practice) — do not invent numbers. Slight chemistry deviations for plates over 50 mm may be allowed only as approved by DNV.

Grade A is the only normal-strength grade with manganese written as a ratio of carbon (2.5 × C) instead of a fixed minimum: Grade B needs 0.80 % Mn (0.60 % if impact-tested), D 0.60 % and E 0.70 %. Grade A also has the widest silicon allowance (0.50 %), which is why any deoxidation except rimmed steel is legitimate up to 50 mm. In practice, Chinese mills supply aluminium-killed NV A with ladle C typically around 0.14–0.18 % and Mn 0.5–1.0 %; treat those figures as indicative only and check the actual mill certificate.

On the 200 mm gauge full-thickness flat specimen (25 mm width), minimum elongation depends on thickness:

One frequent certificate error is quoting a relaxed upper tensile limit on plate: IACS allows the Society to exceed the upper Rm limit for Grade A sections only, not for plate. For each batch, one tensile test is taken from one piece (extra tests when finished weight exceeds 50 t, and for every 10 mm variation in thickness from the same cast), unless otherwise agreed by DNV.

Where a Charpy test applies to Grade A over 50 mm, average energies at +20 °C (full-size specimens, long / trans) per IACS UR W11 Table 6:

One individual value may fall below the average if it is at least 70 % of it. Generally only longitudinal specimens are prepared unless the purchaser or DNV asks for transverse. For buyers: if you order 60 mm or 80 mm NV A for foundations or heavy brackets, agree N/TM (often no impact) or AR with impact testing at enquiry; both routes can be legitimate under special approval, but the certificate must match the supply condition. If the design needs a 0 °C or −20 °C guarantee on thinner plate, order NV B or NV D instead of adding a special test to Grade A.

DNV applies the thickness tolerances of IACS UR W13 (Thickness tolerances of steel plates and wide flats) unless the purchase order states otherwise. In practice class-approved hull plate is ordered to the class minus-tolerance band commonly associated with UR W13 (often 0.3 mm minus — confirm the exact class and plus tolerance on the PO; see UNCERTAIN for the DNV rule paragraph without a local DNV PDF). Plus tolerance, flatness, width and length follow the agreed national or international standard (for example ASTM A6 or EN 10029) unless specified otherwise.

Surface quality follows a recognised standard such as EN 10163 parts 1–2 (or equivalent accepted by DNV). Surface defects may be ground within UR W11 limits; grinding areas are checked so remaining thickness stays within the allowed minus tolerance. If you plan to shot-blast and prime at the yard, state any surface class on receipt in the order.

Quantities are approximate and change daily (indicative — confirm before booking); all stock plates carry NV A 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. A DNV-classed hull needs plate made by a mill approved by DNV for NV A and certified under DNV survey. Dual or multi-class certification (for example DNV + ABS, or DNV + CCS) can be arranged at the mill when the heat is surveyed by both societies.

All four normal-strength grades share the same 235 N/mm² yield and 400–520 N/mm² tensile range; they differ in deoxidation and toughness. NV B is tested at 0 °C where the thickness/condition table requires it (generally not required ≤ 25 mm for Grade B); NV D is tested at −20 °C and must be fine-grain treated above 25 mm; NV E is killed fine-grain steel tested at −40 °C, with each plate tested when supplied normalized or TM. The hull steel grade for each strake is set by the classification rules according to structural member category and thickness, so check the approved drawing first. In general, NV A is used for internal and lightly stressed members, while sheer strakes, bilge strakes, deck stringers and ice-belt plating usually call for B, D, E or higher-strength plates under DNV GL Steel Plates.

Compared with land structural steels, NV A is close in strength to ASTM A36, ASTM A283 Grade C and S275JR class steels but differs in three practical ways: class thickness tolerance practice, the C + Mn/6 ≤ 0.40 cap, and above all the DNV survey and NV A stamp. For a barge or pontoon that will be DNV-classed, only DNV-certified plate is accepted; for an unclassed workboat or a dock structure, buyers sometimes choose A36 or S235 for price, and NV A can also be dual-certified to A131 and DNV for such use.

When DNV NV A is the right choice: typical uses are non-critical hull plating, internal structure, decks and bulkheads of vessels working in temperate water, barges and pontoons. The Charpy temperature (+20 °C, only where required above 50 mm) is fixed by the letter A, and the strength by the normal-strength level (ReH 235 N/mm²). Pick the strength from the scantling calculation and the letter from the material class and design temperature on the approved drawing. Swapping to a different letter or strength needs class approval of the drawing change, not just a new purchase order.

Typical uses: internal hull structure, double-bottom floors and girders, non-watertight and watertight bulkheads in lightly stressed areas, superstructure and deckhouse plating, hatch covers, inland and coastal barges, pontoons, floating docks, fishing vessels and tugs, rudder and skeg internal plates, and ship repair replacement steel. Offshore and port structures also use Grade A for secondary steel; see offshore platform steel plates for primary structure grades.

Cutting: oxy-fuel, plasma and laser cutting all work without preheat in normal thicknesses. Welding: with C + Mn/6 at or below 0.40 %, NV A is welded with ordinary-strength consumables approved for the grade and toughness level required by the shipyard’s DNV-approved WPS; preheat is generally unnecessary below about 25–30 mm except in cold or humid conditions — follow your approved welding procedure, not a generic number from a catalogue. Forming: plates intended for cold flanging should be ordered with the flanging quality agreed on the PO (lower S where required).

Processing notes for NV A: cold forming and flanging of normal-strength plate are routine. Keep the cut edges of plate thicker than 50 mm free of notches, because thick plate of this grade is controlled more tightly for deoxidation (killed above 50 mm) and supply condition.

Every plate is tested and marked at the mill under DNV survey; the mill certificate lists heat number, ladle chemistry (elements required by UR W11 Table 1, plus intentionally added elements), tensile results, impact results where required, condition of supply and plate numbers, and is endorsed by the attending Surveyor. On request we add EN 10204 3.2 certificates with third-party witness by TÜV, SGS, BV or another agency, ultrasonic testing (U mark) or through-thickness testing (Z mark), and multi-class certification with other major class societies (ABS, LR, BV, CCS, NK, KR, RINA).

On receipt, check: NV A stamp and heat number on each plate match the certificate; the certificate shows DNV endorsement, not just a mill stamp; thickness at several points meets the ordered UR W13 / PO tolerance; for plates over 50 mm, the condition of supply and impact results agree with the table above.

Charpy acceptance for NV A by thickness (from IACS UR W11 Table 6 where a test applies; actual results as per standard and mill certificate):

On receipt, check that where Charpy is shown the test temperature is +20 °C and that the energy matches the band for the delivered thickness. Also check that the plate number on the stamp matches the certificate line, and that the DNV Surveyor endorsement is present. If UT was ordered (e.g. EN 10160 or ASTM A578 level), check the UT report as well. If the PO asked for 3.2, the inspector’s report must name the witnessed tests and plate numbers.

• Ordering “DNV A” or “Grade A” without specifying that DNV certification (NV A stamp + Surveyor-endorsed certificate) is required, then receiving GB 712 or A131 plate without class endorsement.
• Accepting a relaxed upper tensile limit on plate that only applies to Grade A sections under IACS.
• Ordering heavy plate (> 50 mm) without agreeing N/TM/CR or impact testing, then finding no Charpy results or an AR certificate without special approval.
• Substituting NV A where the drawing requires NV B, NV D or NV E in a high-stress or low-temperature strake.
• Plates cut from coil without the mill holding DNV approval for coiled product.
• Ignoring the ordered thickness tolerance class when accepting re-rolled or trader stock.
• Confusing commercial “DNV Grade A” with higher-strength NV A36 / AH36 — different yield, chemistry and impact rules.

Each of these is avoided by writing the requirement into the purchase order and checking it on the certificate before the plates are cut.

State the grade and rule (DNV NV A / DNV Grade A, DNV rules for ships – metallic materials), whether multi-class certification is needed, thickness, width, length and quantity per size, condition of supply for plates over 50 mm, any Z or U requirement, surface or primer requirements, certificate type (mill certificate with DNV endorsement, EN 10204 3.2 with third-party witness), packing and destination port. Send the list to SHH STEEL for price, available stock and lead time.

Sample PO line: “Steel plate to DNV rules for classification – Ships, Grade A (NV A), delivery condition [AR/CR/N/TM], 20 × 2500 × 12000 mm, 30 pcs, marked NV A, certificate endorsed by DNV Surveyor, EN 10204 3.2 [if required], UT [if required], CIF [port].” Each bracketed item changes price, lead time and which mills can supply, so fix them at enquiry stage.

DNV Grade A / NV A is the economical base hull steel under DNV rules and IACS UR W11: 235 N/mm² minimum yield, 400–520 N/mm² tensile, generally no impact test up to 50 mm, and class survey with the NV A stamp. What the rules leave open has to be fixed in the order: DNV (or multi-class) certification, the supply condition and impact testing for plates over 50 mm, whether product analysis is required on the certificate, the thickness-tolerance class, and the certificate type (3.1 vs 3.2).

SHH STEEL supplies NV A plate rolled by Chinese mills that hold DNV works approval for the grade, so every plate carries the NV A 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 A mixed with NV B, NV D or higher-strength grades such as NV A36, 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 (DNV NV A / DNV Grade A), 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.