Application of high strength steel of the S690QL class for application to welded structures

Abstract

In this paper are considered the most important properties of a special class of high strength steels S690QL, which can be classified into the group of special low alloyed steels. The high strength steels belong into a group of high quality steels. They possess exceptional mechanical properties, especially tensile strength and toughness. Those favorable properties are being achieved by application of special procedures of thermo-mechanical processing and simultaneous alloying with adequate elements. The advantages that the S690QL steels have with respect to other steels are being presented here. However, possibilities for application of those steels in responsible welded structures are limited due to their only relatively good weldability. The special procedures for improving it are discussed here, primarily preheating, controlled heat input during welding and additional heat treatment of the welded joint. The aim of this paper is to point to the possibility of application of these steels for manufacturing of the responsible welded structures, and simultaneously to point to the fact that the properties of steels as declared by manufacturer (chemical composition, mechanical properties etc.) are not always reliable and that they can vary depending on the batch.