DNV E690 is an extra high strength shipbuilding steel plate specified for hull structures, ship body construction and offshore installations. Supplied in the quenched and tempered condition, it provides a minimum yield strength of 690 MPa, which places it among the strongest hull structural steels used in modern shipyards.
As vessel size and cargo capacity increase, designers look for higher strength plates so that scantlings and steel weight can be reduced without lowering safety margins. DNV E690 meets that requirement by combining very high strength with dependable low temperature toughness at -40 °C and predictable weldability when qualified procedures are followed.
What Does the Grade Designation DNV E690 Mean?
The grade name follows the DNV naming system for hull structural steels, and each element carries a specific meaning:
E – Charpy V-notch impact testing performed at -40 °C
690 – minimum yield strength of 690 MPa
DNV – plate approved under the rules of the classification society for ships and offshore units
Extra high strength plates are normally rolled and then quenched and tempered. Quenching produces a hard martensitic structure, and the following tempering treatment restores toughness, giving a fine tempered microstructure with a high strength to weight ratio. This is the reason E690 is preferred for structural members where every kilogram of steel directly affects deadweight and fuel consumption.
Typical Dimensional and Delivery Range
| Parameter | Typical range |
|---|---|
| Steel standard | DNV rules for classification of ships and offshore units |
| Rolling type | Extra high strength ship plate |
| Thickness | 6 mm – 250 mm |
| Width | 1500 mm – 4200 mm |
| Length | 3000 mm – 18000 mm |
| Heat treatment | Quenched and tempered |
Plates are supplied with a mill test certificate issued to EN 10204 3.1 or EN 10204 3.2, so heat identity and mechanical results can be traced from the melt to the delivered plate.
Chemical Composition of DNV E690
Typical ladle analysis limits for the grade are shown below. The low carbon content and restricted sulphur level support both toughness and weldability.
| Element | Content (%) |
|---|---|
| C | 0.20 max |
| Si | 0.10 – 0.55 |
| Mn | 1.70 max |
| P | 0.030 max |
| S | 0.030 max |
| Al | 0.015 – 0.080 |
| N | 0.020 max |
To reach the 690 MPa yield level together with adequate through-thickness toughness, the steel is micro-alloyed within the limits allowed by the DNV rules. Niobium, vanadium, titanium, copper, nickel, molybdenum and boron are used in combination for grain refinement, hardenability control and precipitation strengthening. The exact addition balance is fixed by the mill according to thickness and the agreed impact requirements, and it is reported on the inspection documents.
Mechanical Properties and Impact Toughness
Mechanical properties are guaranteed for the full thickness range, with Charpy V-notch testing carried out at -40 °C.
| Thickness (mm) | Yield strength, min (MPa) | Tensile strength (MPa) | Elongation, min (%) | Impact, transverse (J) | Impact, longitudinal (J) |
|---|---|---|---|---|---|
| t ≤ 50 | 690 | 770 – 940 | 14 | 46 | 69 |
| 50 < t ≤ 70 | 690 | 770 – 940 | 14 | 46 | 69 |
| 70 < t ≤ 150 | 690 | 770 – 940 | 14 | 46 | 69 |
Transverse specimens are taken perpendicular to the rolling direction and longitudinal specimens parallel to it, which is why the longitudinal energy requirement is the higher of the two. Plates thicker than 150 mm are produced and tested to an agreed specification with the same strength class.
Heat Treatment, Testing and Fabrication
Because of its high strength level, E690 is handled differently from ordinary hull steel. The main points to plan for are:
Plate pretreatment by shot blasting and shop priming before fabrication, which protects the surface during storage and cutting
Through-thickness testing on request, with Z15, Z25 or Z35 quality available for welded joints loaded in the thickness direction
Low temperature impact testing at -40 °C in the transverse and longitudinal directions
Ultrasonic examination to ASTM A435, ASTM A577 or ASTM A578 for internal soundness
Approval by the major classification societies, including ABS, LR, BV, DNV, KR, NK, CCS and RINA
Certificates to EN 10204 3.1 or 3.2 under the original mill test certificate format
Shot blasting, painting, cutting and welding carried out to the end user's specification
Welding of E690 requires a qualified welding procedure, low hydrogen consumables, controlled heat input and adequate preheating, with interpass temperature kept inside the range approved during procedure qualification. Thermal cutting edges should be dressed or machined before welding where the specification demands it, and any flame straightening should be agreed before it is carried out, since excessive heat input reduces the tempered strength of the plate.
Frequently Asked Questions
Q: What does DNV E690 mean?
The letter E indicates Charpy V-notch impact testing at -40 °C and the number 690 states the minimum yield strength of 690 MPa. The plate is approved under DNV rules for ships and offshore units.
Q: What is the difference between E690 and F690?
The strength class is identical; the difference is the impact test temperature. E690 is tested at -40 °C, while F690 is tested at -60 °C for service in colder environments.
Q: What delivery condition is used?
E690 is delivered in the quenched and tempered condition. Plates are quenched from the rolling or austenitising temperature and then tempered to obtain the required strength and toughness combination.
Q: Which thickness range is available?
Standard production covers 6 mm to 250 mm in thickness, 1500 mm to 4200 mm in width and 3000 mm to 18000 mm in length, subject to rolling capability at the ordered size.
Q: What tests are performed on the plates?
Chemical analysis, tensile testing, Charpy V-notch impact testing at -40 °C, optional through-thickness testing at Z15, Z25 or Z35 level, and ultrasonic examination under ASTM A435, ASTM A577 or ASTM A578.
Q: Where is DNV E690 typically used?
It is used for hull structures, ship body construction, offshore platform components, heavy lift frames and other welded structures where high strength and low weight are required.
