DNV F32 steel plates are high strength hull structural plates produced under the DNV rules for classification of ships and offshore units. The grade combines a minimum yield strength of 315 MPa with Charpy V-notch impact toughness verified at -60 °C, making it suitable for ships and marine equipment that operate in low temperature service.
In the DNV strength series, normal strength grades are followed by high strength grades such as F32 and F36 and by extra high strength grades such as E690. F32 is one of the most widely ordered high strength grades because it offers a balanced combination of strength, toughness, weldability and cost.
What Is DNV F32 Steel Plate?
The grade designation has three parts:
F – Charpy V-notch impact testing at -60 °C, the lowest test temperature in the DNV hull structural series
32 – strength class with a minimum yield strength of 315 MPa
DNV – approval under the rules of the classification society for ships, barges and marine equipment
F32 plates are readily welded with all common arc processes when suitable consumables and heat input control are applied. The grade is delivered in the as-rolled, controlled rolled or normalized condition depending on thickness and on the toughness level required by the application.
Specification Range and Delivery Condition
| Parameter | Typical range |
|---|---|
| Thickness | 6 mm – 220 mm |
| Width | 1000 mm – 4000 mm |
| Length | 3000 mm – 12000 mm, or as agreed |
| Delivery condition | Hot rolled, controlled rolled or normalized |
| Surface treatment | Shot blasting and priming available |
| Packing | Standard export packing or to customer specification |
Cutting can be carried out by CNC flame cutting, plasma cutting, waterjet cutting, laser cutting or oxy-fuel cutting, which allows plates to be delivered as cut-to-size components for hull blocks and marine structures.
Chemical Composition of DNV F32
The table below lists typical maximum values. Carbon, phosphorus and sulphur are kept low to support toughness at -60 °C and to reduce the risk of weld cracking.
| Element | Content (%) |
|---|---|
| C | 0.16 max |
| Si | 0.10 – 0.50 |
| Mn | 0.90 – 1.60 |
| P | 0.025 max |
| S | 0.025 max |
| Al | 0.015 – 0.080 |
| N | 0.009 max |
Small additions of niobium, vanadium, titanium, copper, chromium, nickel and molybdenum are used in combination to refine the grain structure and to meet the strength and impact requirements of the F class, with typical levels of Nb 0.02 – 0.05 %, V 0.05 – 0.10 %, Ti 0.02 % max, Cu 0.35 % max, Cr 0.20 % max, Ni 0.80 % max and Mo 0.08 % max.
Mechanical Properties and Charpy Impact Values
Mechanical properties are guaranteed for the full thickness range and are verified on a per-heat, per-rolling-lot basis, with impact testing carried out at -60 °C.
| Thickness (mm) | Yield strength, min (MPa) | Tensile strength (MPa) | Elongation, min (%) | Impact, transverse (J) | Impact, longitudinal (J) |
|---|---|---|---|---|---|
| t ≤ 50 | 315 | 440 – 590 | 22 | 22 | 31 |
| 50 < t ≤ 70 | 315 | 440 – 590 | 22 | 26 | 38 |
| 70 < t ≤ 150 | 315 | 440 – 590 | 22 | 31 | 46 |
Energy requirements rise with plate thickness, which reflects the greater difficulty of achieving toughness in heavier sections. Transverse testing, taken perpendicular to the rolling direction, is the more demanding of the two directions and is the value usually specified for design verification.
Applications, Fabrication and Inspection
DNV F32 is widely used in the shipbuilding industry for structural parts of ships, barges and marine equipment, as well as in decks, bulkheads, hatch covers and offshore support structures. Key fabrication and quality points include:
Weldability with shielded metal arc, submerged arc, gas metal arc and flux cored processes using approved consumables
Controlled heat input and, for thicker sections, preheating to prevent cold cracking
Ultrasonic testing of the plate and of welded joints where specified, to American Bureau of Shipping or classification society requirements
Mill test certificates to EN 10204 3.1 or 3.2 with full heat traceability
Blast cleaned and primed surfaces for improved coating performance during construction
Because the grade is impact tested at -60 °C, F32 is often selected for vessels trading in cold climates, ice-class related structures and other applications where low temperature brittle fracture resistance is a primary design concern.
Frequently Asked Questions
Q: What does the F in DNV F32 stand for?
F indicates that Charpy V-notch impact testing is carried out at -60 °C. The number 32 identifies the strength class, with a minimum yield strength of 315 MPa.
Q: How does F32 differ from E32 or A32?
The strength class is the same in all three cases. The difference is the impact test temperature: A32 is tested at 0 °C, E32 at -40 °C and F32 at -60 °C.
Q: What is the delivery condition of F32 plates?
Plates are supplied hot rolled, controlled rolled or normalized, depending on thickness and the toughness requirement of the project.
Q: Which thickness range can be supplied?
Standard production covers 6 mm to 220 mm in thickness, 1000 mm to 4000 mm in width and 3000 mm to 12000 mm in length, with other sizes possible by agreement.
Q: Which cutting methods are available?
CNC cutting, plasma cutting, waterjet cutting, laser cutting and oxy-fuel cutting are all available, allowing delivery as ready-to-fabricate cut parts.
Q: What documents are provided with the plates?
Mill test certificates are issued to EN 10204 3.1 or 3.2, including chemical analysis, tensile results and Charpy impact values at -60 °C, together with classification society approval where required.
