Status & Prospects of Shipbuilding Steel and Its Weldability

Posted:5/27/2011 11:19:02 AM

Being combined with TMCP steels, a variety of welding technologies have been developed to increase welding speed, deposition rate and integrity of welds. More, concerns have been extended to the safety and the durability of ships, and thereby, improved HAZ toughness, crack arrestability, corrosion resistance and fatigue strength have been demanded for structural steel plates for shipbuilding Reducing weight and increasing energy efficiency have been prime concerns to achieve the large-size ships
such as ultra large crude oil carriers (ULCC), very large crude oil carriers (VLCC), liquefied gas carriers, cargo ships, and passenger carriers , while reducing construction
cost and time also has been increasingly required in shipbuilding industry. Steel plates produced by thermo-mechanical control processes (TMCP) have provided an effective solution to those requirements, offering better combinations of strength and toughness
without losing weldability, as compared with conventional normalized steels1-3). The use of the TMCP steel plates with higher strength has made it possible not only to reduce the weight of the ship but also to apply high speed, high heat input welding to the construction, because of better weldability and HAZ toughness. Being combined with TMCP steels, a variety of welding technologies have also been developed to increase welding speed, deposition rate and integrity of welds. More recently, concerns have been extended to the safety and the durability of ships, and thereby, improved HAZ toughness, crack arrestability, corrosion resistance and fatigue strength have been demanded for structural steel plates for shipbuilding
In recent years, high performance high strength steel plates have been mass-produced by TMCP technologies. Because optimum adjustment of the hot-rolling and subsequent cooling conditions can be realized with these technologies, product properties are superior to those obtained with off-line heat treatment The TMCP steels have offered improved combinations of strength and toughness as compared with conventional steels, owing to the refined mixed microstructure of ferrite and bainite. This characteristic
microstructure of TMCP steels is primarily achieved by hot-rolling in the non-recrystallized temperature region and subsequent accelerated cooling