WELDABILITY OF HSLA STEELS IN RELATION TO APPROPRIATE TOUGHNESS REQUIREMENTS FOR USE IN SAFE AND ECONOMIC STEEL CONSTRUCTION

摘要

Research efforts in the development of high strength steels during the past 4 decades have led to a bundle of new steels which provide not only high strength to the designer, but also have excellent toughness, low transition temperature behavior in view to cold climate application and good weldability. However, application of such modern steels in many cases seems to be restricted which means that advantages resulting from light weight design such as lower working costs, lower transportation weights and lower energy consumption cannot be fully realized. Reasons for that are manifold and can either be technically justified (e.g. for highly fatigue loaded structures as bridges) or may result from lack of design knowledge, fabrication knowledge with respect to weldability and heat treatment, a diffuse understanding of the toughness issue and finally lack of appropriate standards. To overcome such obstacles worldwide research has been performed on modern structural integrity concepts and weldability of HSLA steels for long time. Taking account of such research, which has led to practical welding aspects for such steels (such as t8/5 concept), it has become possible to produce safe weldments and to derive toughness requirement in a realistic and safe way. As a result of such efforts, new toughness oriented design methods have been included in European design rules like EN 1993-1-10 (Eurocode 3) and EN 13445 (unfired pressure vessels). They provide better opportunities for the application of modern fine grain high strength steel within the legal frame of such highly safety demanding public areas. The contribution will reflect upon this development with respect to a discussion of the material properties, the effect of fabrication on the latter and the effect of both on the necessary design assumptions. Specifically the derivation of toughness requirements that is closely related to the discussion for low temperature applications is presented. Examples of application close this contribution.