Shipbuilding Steels: Part One

Abstrakt:

Various shipbuilding requirements, such as reduction in welding man-hours, shortening of welding lines, elimination of cutting steps, stabilization of fabricated part quality and reduction in control costs, have been met by developing TMCP high-strength steels that require no preheating for welding, irregular-section plates and plates with close dimensional tolerances, and by increasing the stringency of pre-shipment plate quality control.

A demand for heavy thick plates with a good combination of high strength, toughness, and weldability has been widely growing in recent years for large container ship building. Because of this, e tra high-strength termomechanically processed steels TMCP have been developed to be more user friendly than the traditional steels.

E cellent handling properties are based on thermomechanical treatment that reduces the need for e cessive use of alloying elements to strengthen the steel. TMCP plates are thermomechanically controlled rolled, and with greater plate thicknesses, also accelerated cooled after rolling.

Generally, TMCP steels are supplied as heavy plates, surface treated plates and plate components. Due to the very low carbon equivalent, TMCP steels are easily weldable using all common processes. In addition, they are easy to form, bend and edge.

TMCP steels give many monetary advantages to the shipbuilder:

  • Reduced plate thickness
  • Saving weight in the final structure
  • Greater effective loads during use
  • Cost savings in welding and fabrication.

The successful application of thermo-mechanical control process (TMCP) with the recent innovative technology has induced the development of EH36, EH40, and EH47 grade steel plates. The alloying elements such as boron, copper, and nickel were added and the rolling and cooling processes were strongly and precisely controlled to improve the strength and toughness at the same time. EH36 steel plate for high heat input welding was successfully developed with good toughness at the heat affected zone (HAZ) by increasing the thermal stability of TIN particles at the high temperature.

The quality of shipbuilding steels has an e tremely large impact on the quality, efficiency and cost of ships built from those steels. Many steel producers established a system to supply wide and long plates to the shipbuilding industry.

Various shipbuilding requirements, such as reduction in welding man-hours, shortening of welding lines, elimination of cutting steps, stabilization of fabricated part quality and reduction in control costs, have been met by developing TMCP high-strength steels that require no preheating for welding, irregular-section plates and plates with close dimensional tolerances, and by increasing the stringency of pre-shipment plate quality control. Table 1 shows the common steel grades for shipbuilding.

Table 1: Steel for Ship Building

Lloyds Norske
Veritas
Germanischer
Lloyds
Bureau
Veritas
American Bureau
of Shipping
USSR
Register
Nippon
Kaigi Kyoka
A A A A A A A
B B B B B B B
D D D D SS D D
        CD/DS    
  NV A27S          
  NV D27S          
AH 32 NV A32 A 32 AH 32 AH 32 A 32  
DH 32 NV 32 D 32 DH 32 DH 32 D 32  
EH 32 NV E32 E 32 EH 32 EH 32 E 32  
AH 34S            
DH 34S            
EH 34S            
AH 35 NV A36 A 36 AH 36 AH 36 A 36  
DH 36 NV D36 D 36 DH 36 DH 36 D 36  
EH 36 NV E36 E 36 EH 36 EH 36 E 36  
  NV A40          
  NV D40          
  NV E40          
  NV A420          
  NV D420          
  NV E420          

Steel in shipbuilding

Shipbuilding traditionally uses structural steel plate to fabricate ship hulls. Modern steel plates have much higher tensile strengths than their predecessors, making them much better suited to the efficient construction of large container ships.

A particular type of plate is available with a designed-in resistance to corrosion, ideal for building oil tankers. Such steels make possible much lighter vessels than before, or larger capacity vessels for the same weight, offering significant opportunities to save on fuel consumption and hence CO2 emission.

The advanced steels used in these steel-plate applications also find uses in a number of related industries. Offshore oil rigs, bridges, civil engineering and construction machines, rail carriages, tanks and pressure vessels, nuclear, thermal and hydroelectric plants – all these applications benefit from the attributes of modern steels.







Figure 1: Ships: Navy, Cargo and Cruise

In recent years, more attention has been paid to the safety and durability of ships and environment protection of sea, which have lead to the development of new structural steel plates. One of them is the development of more corrosion resistant plates for double-hull tankers. Crude oil carriers are now required to have double hulls to prevent oil spill, and an increase in temperature in oil tanks with the double hull structure increases the likelihood of corrosion of upper deck steel plates exposed to the vapor space in the tanks. To prevent the corrosion and to increase the life time of the ships, different corrosion resistant steel palates have been developed.

The development of new steel plates has also been made to increase construction efficiency and thereby to decrease construction cost. Longitudinally profiled (LP) steel plates were developed in this context. Thickness change within a plate was achieved by controlled rolling, which made it possible to replace the plates which had been made by welding steel plates of different thickness, and therefore to reduce the welding time and cost.

Another development is concerned with residual stress retaining in steel plates. TMCP steel plates are likely to possess residual stresses from their production, and this often results in distortion in different ways after cutting and welding of the plates. In order to achieve residual stress-reduced steel plates, temperature differences over the large surface area in a wide and long plate and through the thickness should be minimized and cold levering is also used for the purpose of reducing inhomogeneous stress for block shape accuracy.

A number of research projects are currently being carried out on the European and national levels to improve the application of lasers and optical technologies in shipbuilding. In laser beam welding, centre line solidification cracks in the fused zone are in issue and can limit the travel speed and hence productivity.

The fused zones are typically of the same composition as the steel being welded and whilst there are several welding procedural factors which can be used to minimize the risk of cracking, the problem hinges on the steel composition. Lower S and P levels may thus be required as shown in Table 2.

Table 2: Classification society guidelines for laser welding of ship hull

C 0.12% max (lower speeds ≤ 0.15%)
S 0.005% max (≤ 0.010% for ≤ 12 mm, 0.6 m/min)
P 0.010% max (≤ 0.015% for ≤ 12 mm, 0.6 m/min)
CE 0.38% max  
Weld hardness ≤ 380 HV5 max (≤ 400 HV5 isolated)

Durchforschen Sie bitte den Informationsteil der Datenbank

Geben Sie bitte eine Anfrage, um Suche einzuleiten:

Suche nach

Vollständiger Text
Schlüsselwörter

Überschriften
Abstracts

Dieser Artikel ist Teil einer Artikelserie. Klicken Sie die Links um mehr über dieses Thema zu lesen.

Die Total Materia Datenbank, enthält mehrere tausende von Baustählen aus vielen Ländern und Normen.

Wenn zur Verfügung stehend, können alle Informationen über die Werkstoffeigenschaften angezeigt werden, einschliesslich chemische Zusammensetzung, mechanische und physikalische Eigenschaften, vortschrittliche Daten und vieles mehr.

Auf der Seite der erweiterten Suche ist es möglich Werkstoffe nach Anwendung mit Hilfe der Volltextsuche zu finden.

Es kann auch notwendig sein daß Sie Ihre Suche weiter einschränken indem Sie die anderen Felder der erweiterten Suche, wie z.B. Land/Norm benutzen.

Klicken Sie auf "Absenden".


Es wird danach eine Liste von Werkstoffen angezeigt von welcher Sie auswählen können.


Nachdem Sie auf der Ergebnisliste auf den entsprechenden Werkstoff geklickt haben, wird eine Liste der Untergruppen, welche Normspezifikationen sind, angezeigt.


Von hieraus ist es möglich, spezifische Eigenschaften für den ausgewählten Werkstoff anzuzeigen und äquivalente Werkstoffe mit unseren leistungsstarken Cross-Reference Tabellen zu finden.

Es ist, zum Beispiel möglich, durch klicken auf den entsprechenden Link, der Seite der Untergruppen, die chemische Zusammensetzung des erwünschten Werkstoffs anzuzeigen.


Andere kritische Werkstoffeigenschaften für Baustähle, wie mechanische Eigenschaften, mit Fließspannung, Zugspannung, Dehnung und Kerbschlagarbeit, können auch angezeigt werden.


Um unsere Datenbank auszuprobieren, laden wir Sie ein sich unserer Nutzergemeinschaft von über 150 000 angemeldeten Benutzern, mit einem kostenlosen Probeaboanzuschliessen.