Welding technology for stainless steel AISI 316L – the problem of reducing deformations on decks in stern trawler hull

Abstract

The development of international trade is directly connected to the shipbuilding industry. That means that, economically, ships have great value for the world’s trade, as many goods are transported by ships. Thus, the ship’s quality plays a crucial part in the functioning of the system, not only for trade but also for offshore uses, cruises, and fishing activities. In shipbuilding industry, several criteria affect the performance of a shipyard and the vessels themselves, from material’s choice, going through the construction process, until the delivery of the ship. Structure deformation is one of the biggest issues faced by the shipbuilding industry because it is extremely dependent on welded structures and equipment. The consequences of the deformation in ship structures are costly (maintenance, replacement, shorter lifetime) along with customer dissatisfaction and the inefficiency of the hull, especially for ships, where the contractual penalty is very high. As deformations are mainly caused by the welding process, it is important to study the effect of its parameters, considering the material, weld joint, welding type - Submerged Arc Welding (SAW), Flux- Cored Arc Welding (FCAW) – and its welding sequence. Accordingly, to perceive the welding behavior at the workshop and its deformation, welding procedure of the stainless steel AISI 316L was followed and deformations after butt welds, fillet welds and straightening were measured using a tachometer. These measurements were done on the decks of two fishing vessel’s projects - NB 395 and NB 396. In this work, the biggest challenge was to deal with stainless steel AISI 316L, as its use is not conventional for the ship industry. Further, welding type FCAW still need to be fully developed even though; gas electric arc welding principle is the most common in the industry. The design of experiments was performed in spite of confronting numerical analysis with experimental results. By using the diagnosis of the construction process and welding procedure, different assumptions were made in pursuance of improvement of the activities aiming high quality of services, consequently achieving a better quality of delivered vessels