NV F620, also written DNV Grade F620, is an extra-high-strength Det Norske Veritas hull steel with a specified minimum yield strength of 620 MPa and F-level impact testing at −60°C. It belongs to Sec.1 D of the January 2016 metallic-materials chapter, which is a different family from the ordinary-strength and high-strength 32/36/40 grades, and those families’ numbers must not be copied onto this grade. Gangsteel welcomes enquiries for NV F620 plate for shipbuilding and export projects; dimensions, delivery condition and documentation are agreed for the individual order.
The numerical requirements on this page for DNV Grade F620 (NV F620) are transcribed from the official predecessor Det Norske Veritas Rules for Classification of Ships, Part 2 Chapter 2 Metallic materials, January 2016 edition, entering into force on 1 July 2016, Sec.1 D, including Tables D1 and D2 and clause D300, together with the general requirements of Sec.1 A. That January 2016 chapter is a predecessor document family; it is not the current DNV-RU-SHIP Part 2 Chapter 2. The current listed official ship-rules edition is DNV-RU-SHIP, July 2026, which enters into force on 1 January 2027. The later edition’s numerical tables have not been independently verified here. The edition named in the contract, the applicable certificate and the attending surveyor’s requirements govern any actual supply. The figures below are January 2016 rule requirements for plate, not a statement that material offered today complies with the July 2026 rules, and not measured results for a particular heat.
Grade Designation
NV F620 is the official designation in Sec.1 D; DNV Grade F620 is the usual commercial writing of the same extra-high-strength grade. The number 620 is the specified minimum yield stress in MPa; the letter F is the toughness level (Charpy test temperature) within that strength level. Extra-high-strength steels are a separate family from the high-strength 32, 36 and 40 grades and from ordinary-strength NV A to NV E. Marking follows Sec.1 A1101, for example NV F620. This page covers plate; other product forms are not treated as plate data.
Under Sec.1 A102, the plate and wide-flat requirements summarized here apply to thicknesses not exceeding 150 mm. For greater thicknesses, variations in the requirements may be permitted for particular applications. Through-thickness (‘Z’) quality, where needed, is a supplementary Sec.1 E requirement (quality classes Z25 and Z35) and is not implied by the base grade name or by this product title.
Key Advantages of F620 Steel Plate
- Defined extra-high-strength level: a specified minimum yield stress of 620 MPa and a tensile-strength range of 720–890 MPa under Table D2, which must not be confused with the 32/36/40 family figures.
- F-level toughness is verified at −60°C, with a single Table D2 impact-energy requirement applying through the tabulated thickness range. That temperature is a laboratory condition, not a minimum service temperature.
- The grade is killed and fine-grain treated. Table D1 chemistry depends on the toughness letter (A, D/E, or F) across strength levels 420 to 690; carbon-equivalent and Pcm maxima are not numerically specified for these grades in that table.
- Strength levels above 500 MPa are supplied in the TM or QT condition only (Sec.1 D300). Delivery condition must be confirmed against the manufacturer’s approval.
Chemical Composition (Heat Analysis)
Table values are taken from a heat analysis (Sec.1 A401): the composition of each heat is determined on a sample taken preferably during pouring of the heat. When several heats are tapped into a common ladle, the ladle analysis applies and shall remain within the same specified limits. Values are percentage by mass, maximum unless shown as a range or as a minimum. They are rule limits, not typical mill results and not product-analysis tolerances.
Table D1 gives chemical composition limits for extra-high-strength steel, for t ≤ 150 mm. NV F620 shall be killed and fine-grain treated. The values below are from the column “Grade F of strength levels 420 to 690”. The separate NV D47/E47 column is not used on this page.
| Element | Heat-analysis requirement (t ≤ 150 mm) |
|---|---|
| Carbon, C | 0.18 max |
| Silicon, Si | 0.10–0.55 |
| Manganese, Mn | 1.60 max |
| Phosphorus, P | 0.025 max |
| Sulphur, S | 0.025 max |
| Chromium, Cr | 0.20 max; see residual-addition note |
| Molybdenum, Mo | 0.08 max; see residual-addition note |
| Nickel, Ni | 0.80 max; see residual-addition note |
| Copper, Cu | 0.35 max; see residual-addition note |
| Aluminium, Al | Minimum 0.020% total when used as required below (acid-soluble alternative: minimum 0.015%) |
| Niobium, Nb | 0.02–0.05, subject to the grain-refining rule below |
| Vanadium, V | 0.05–0.10, subject to the grain-refining rule below |
| Titanium, Ti | 0.007–0.05, subject to the grain-refining rule below |
| Nitrogen, N | 0.009 max; 0.012 max if aluminium is present; Al:N ≥ 2:1 applies (not applicable for titanium-killed steel) |
| Boron, B | No limit stated in Table D1 (“–”) |
| Carbon equivalent Ceq | No numerical maximum is stated in Table D1 for Grade F of strength levels 420–690 (“–”). No value is invented here. |
| Pcm | No numerical maximum is stated in Table D1 for this column (“–”). |
The steel shall contain aluminium, niobium, vanadium or titanium, either singly or in any combination. When an element is used singly, the specified minimum for that element applies. When aluminium and niobium are used together, the minimum total aluminium is 0.015% and the minimum niobium is 0.010%. When aluminium and vanadium are used together, the minimum total aluminium is 0.015% and the minimum vanadium is 0.030%. The maximum of Nb+V+Ti is 0.13% (Table D1, note 5); this limit is not the 0.12% figure used in the high-strength Table C1.
Table D1 note 3: the stated chromium, molybdenum, nickel and copper limits do not apply when those elements are intentionally added according to an approved specification. Note 1 of the continued table records composition as a maximum percentage unless shown as a range or minimum.
Mechanical Properties
Table D2 mechanical properties apply to extra-high-strength steel. MPa is numerically equal to N/mm². Unless otherwise agreed, for plates and wide flats 600 mm wide or more, tensile test pieces are transverse; for extra-high-strength steel, impact tests are required in the transverse direction (Sec.1 A605).
| Property | NV F620 requirement (Table D2) |
|---|---|
| Yield stress ReH, minimum | 620 MPa |
| Tensile strength Rm | 720–890 MPa |
| Elongation A5, minimum | 15% |
For full-thickness flat tensile test pieces 25 mm wide with a 200 mm gauge length, Table D2 reduces the minimum elongation (%) to the following values. These figures must not be copied onto the A5 basis.
| Thickness, mm | t ≤ 10 | 10 < t ≤ 15 | 15 < t ≤ 20 | 20 < t ≤ 25 | 25 < t ≤ 40 | 40 < t ≤ 50 | t > 50 |
|---|---|---|---|---|---|---|---|
| Strength level 620 | 9 | 11 | 12 | 12 | 13 | 14 | 15 |
Sec.1 D401: the extent of tensile and impact testing for extra-high-strength steel is each piece.
These tables state January 2016 rule requirements for DNV Grade F620, not evidence of certificates currently held by Gangsteel and not test results for a particular plate. Before purchase, confirm the contractual rules edition, the manufacturer’s approval for the grade, thickness and delivery condition, the inspection and certification scope, and the actual test results in the documentation for the offered material.
Charpy V-Notch Impact Requirements
Energies are minimum averages for a set of three standard Charpy V-notch test pieces (Sec.1 A703). Table values are average minima; a single-specimen minimum is not stated in these mechanical-property tables and is not invented here. The test temperature is a laboratory condition, not an approved minimum service temperature.
| Plate thickness t | Test temperature | Minimum average, longitudinal (J) | Minimum average, transverse (J) |
|---|---|---|---|
| t ≤ 150 mm (single merged Table D2 cell for this strength level) | −60°C | 62 | 41 |
Table D2 presents a single L (T) value of 62 (41) spanning the tabulated thickness columns for the 620 strength level (A/D/E/F of this level share the energy and differ by temperature: 0°C, −20°C, −40°C and −60°C respectively). Because A605 requires transverse impact tests for extra-high-strength plates and wide flats 600 mm wide or more, the transverse figure is the required direction for that usual plate width, unless otherwise agreed.
Delivery Condition and Weldability
Abbreviations follow Sec.1 A500: AR as-rolled, NR normalising rolling, N normalising, TM thermo-mechanical rolling, and QT quenching and tempering. Where more than one condition is permitted, the manufacturer may supply only conditions for which it is approved. The following entries are the plate column of the official table; section-column permissions are not shown as plate data.
Under Sec.1 D300, steel grades of strength levels over 500 MPa shall be supplied in the TM or QT condition. The manufacturer may supply only those conditions for which it is approved (A501). Other conditions may be accepted only on special evaluation and approval (A508).
Table D1 shows “–” for both Ceq and Pcm in the Grade A, D/E and F columns of strength levels 420 to 690. No carbon-equivalent or Pcm maximum is assigned on this page for NV F620. When a value is required, Sec.1 A405 gives the heat-analysis formulae; numerical limits are not invented from other families or other societies.
Available Dimensions
Under Sec.1 A102 of the January 2016 chapter, the plate and wide-flat requirements summarized here apply to thicknesses not exceeding 150 mm. Greater thicknesses may be considered only with the variations permitted for the particular application. Sec.1 A903 states that, for plates and wide flats, the minus tolerance on the ordered nominal thickness shall not exceed 0.3 mm; this is a rule tolerance, not a stock-size list. Width, length, edge condition, quantity and processing are agreed for the order. This page does not list inventory quantities or implied mill stock sizes.
Main Applications
Sec.1 A101 applies extra-high-strength rolled steels, like the other structural families in this chapter, to hulls and other marine structures. NV F620 is considered where the approved design calls for the 620 MPa yield level and F-level toughness, typically in highly loaded members. It is a different family from NV A32–F40 and must not be ordered or calculated as if it were a 32/36/40 grade. Impact-test temperatures are laboratory conditions, not approved minimum service temperatures.
Equivalent Grades of F620
NV F620 and the commercial writings of DNV Grade F620 name the same Det Norske Veritas grade; they are not cross-society equivalents of one another. The table below lists similarly named official product pages on gangsteel.com for comparison only. Other-society figures are not used as DNV requirements. Automatic substitution is not permitted.
| Society / standard | Comparable grade | Qualification |
|---|---|---|
| ABS | ABS Grade FQ63 | ABS extra-high-strength grade in the 63 class, commercially compared with the DNV 620 MPa strength level. This is a strength-level comparison only, not a certified equivalent, and the letter correspondence (F versus FQ) does not mean exact grade equivalence. Impact-test temperatures and energies follow each society’s own rules and must not be assumed identical; ABS numerical requirements are not used as DNV figures on this page. The ABS product title also refers to Z35, a through-thickness quality which, under the January 2016 DNV rules, is specified separately in Sec.1 E and is not implied by NV F620 alone. Not a drop-in substitute. |
No official gangsteel.com product pages were identified in the BV, CCS, LR, KR, GL official shipbuilding categories for a corresponding extra-high-strength grade, so no URL is listed for those societies. No missing-grade address is invented.
Any proposed replacement requires a complete comparison of chemistry, strength, toughness, test temperature, thickness scope, delivery condition, sampling, mill approval and certification, and must be accepted by the designer and the relevant classification society under the contractual rules edition.
Related Products
- NV A620 steel plate
- NV D620 steel plate
- NV E620 steel plate
- NV F550 steel plate
- NV F690 steel plate
- DNV Grade FH40 steel plate
- DNV shipbuilding steel plates
Frequently Asked Questions (FAQ)
What is NV F620 (DNV Grade F620) steel plate?
NV F620, also written DNV Grade F620, is a Det Norske Veritas extra-high-strength hull plate with a specified minimum yield stress of 620 MPa and F-level toughness. It is specified in Sec.1 D, separately from the 32/36/40 high-strength family. The numerical tables here follow the January 2016 predecessor chapter.
Does the impact test temperature define the service limit of DNV Grade F620?
No. DNV Grade F620 is associated with a Charpy test temperature of −60°C under the January 2016 Table D2 requirements, including any thickness exemptions described above, but that laboratory temperature is not a blanket minimum operating temperature. The vessel or component requires its own approved material selection.
Is DNV Grade F620 always supplied in the same delivery condition?
No. Permitted plate conditions for DNV Grade F620 are those in Sec.1 D300 of the January 2016 chapter, subject to the manufacturer’s approval. The grade name alone does not fix the delivery condition.
Does DNV Grade F620 automatically include through-thickness Z quality?
No. DNV Grade F620 identifies the base grade. Through-thickness quality (Z25 or Z35) is a supplementary requirement under Sec.1 E and must be specified, produced and tested separately. These product titles do not state Z35, and this page does not imply stock Z-quality plate.
Can another shipbuilding grade replace DNV Grade F620?
Not automatically. DNV Grade F620 must match the approved design and the contractual classification requirements. A different toughness letter, strength family, rules edition or society designation needs a technical and approval review before substitution. Similarly named grades of other societies are comparison candidates only.
What should an enquiry for DNV Grade F620 include?
Include DNV Grade F620 (and the official designation NV F620), the rules edition that will govern the contract, dimensions, quantity, delivery condition, required inspection documentation, and any additional testing or through-thickness requirements. Availability, documentation and delivery are confirmed for the specific enquiry; none is implied by this overview.
Contact Gangsteel with your DNV Grade F620 plate specification and project requirements for an order-specific technical and commercial review.