On the design of fillet welds made of ultra-high-strength steel

Abstract

Current static design approaches for fillet arc welds made of high or ultra-high strength steel (UHSS) do not differ from design of welds made of conventional steels. However, important issues such as potential softening in heat affected zone (HAZ), strength at fusion lines, optimal reinforcement geometry, load capacity changes due to local bending moment and the effect of post weld treatments on the joint strength require careful consideration in order to ensure optimum performance from these steels. This paper reprises results of previous research works and recent findings, and summarizes key aspects of weld design specific to UHSS welds.

Overview on the digitized production of welded steel structures

“…These can be utilized, for example, when producing welded structures from high-and ultra-high-strength steels, of which use has increased during past decades in the engineering industry due to their potential in terms of payload capacity, structural durability [56,57], energy efficiency, emission control, life cycle management, and recycling [58,59]. However, the application of high-strength steels causes often restrictions on the rules for design [18,60], narrower parameter windows for fabrication (e.g., welding) [6,[61][62][63], and more specific precepts for inspection, due to the basic fracture mechanics law where the critical crack size decreases when the strength of the material increases [64], compared to the corresponding mild steel structures. Consequently, the management of the production chain by means of digitalization is emphasized in these types of demanding welded structural applications.…”

“…Other parts of the design tools will deal with the design of throat thicknesses for different applications, including adjustment of the optimal cooling rate (t 8/5 ) by control of heat input (Q) and also the static strength design of fillet welds according to EC3 [17,18] or more purposeful eccentric fillet welds, as discussed in [6]. The throat thickness of symmetric fillet weld defines the Q and thus, also fits the t 8/5 , which can be roughly estimated by means of following Eqs.…”

“…Prior studies, however, have clearly indicated that welding as a joining method can severely modify the high performance of parent UHSS materials. Welding of HSS and UHSS materials may incorporate several issues, such as a reduced static strength [6,7], ductility [8][9][10], and fatigue strength [11], as well as brittle failure susceptibility [12] and structural stiffness. These aspects demand a careful consideration of optimal process parameters, together with potential pre-and post-weld treatments, as well as advanced design phase to maintain the good properties of parent material, resulting in an increased amount of information needed in the fabrication.…”

On the interaction of axial and bending loads in the weld root fatigue strength assessment of load-carrying cruciform joints

“…The study continues the experimental work carried out in [22] with new tests on the interaction loads, and thus S960MC UHSS grade with the plate thickness of t = 9 mm was chosen for this study. The welded joints were prepared with gas metal arc welding (GMAW) using a strengthmatching filler metal, Böhler Union X96 [44,45] (nominally under-matching). The chemical composition and mechanical properties of the studied materials have been presented in Tables 2 and 3, respectively.…”

Comparison of mechanical behavior between longitudinal lap-welded joints and transverse fillet welded joints of high strength steel

“…For the past few years, mechanical properties of fillet welded joints made of HSS under static loading [21][22][23][24][25][26][27][28] , impact loading [29,30] and fatigue loading [31][32][33] were investigated. Several novel conclusions different to mild steels have been achieved.…”