More sophisticated thermodynamic designs of welds between dissimilar steels

Abstract

In the present paper, steels that are mostly used in technical practice as base materials, filler metals and consumable electrodes in the design of dissimilar weld joints are studied. These steels differ mainly in the content of Cr, Mo, V, W and N. It is explained and emphasised in the present paper that the effect of thermodynamics, diffusion and phase transformations on the stability of dissimilar weld joints that are exposed to temperatures of over y500uC cannot be underrated during operation. For all the materials under study the carbon activity at 600uC is given as calculated by the CALPHAD method, and a correlation is shown to exist between the carbon activity and the total chromium content. This correlation can be used as a most general alternative in the selection of filler metals or consumable electrodes in the design of dissimilar weld joints. The primary goal of the present paper is, however, to present a more sophisticated alternative based on a mutual comparison of the temperature dependence of the carbon activities of the base alloys, filler metals and consumable electrodes under consideration. This alternative is suitable for routine engineering purposes. Attention is also drawn to the currently most advanced alternative, which enables the prediction of the redistribution of elements and phases after prolonged exposure.

Hydrogen pre-charging effects on the notch tensile properties and fracture behaviour of heat-affected zones of thermally aged welds between T24 and T92 creep-resistant steels

“…Generally, the long-term holding of dissimilar weldments at elevated temperatures induces microstructural changes in individual steels including carbon and nitrogen redistribution [25,26]. Therefore, Ni-based transition weldments, i.e.…”

Invetigations of mechanical properties after dissimilar steels post-weld of Q345B steel

“…Since the amount of thermal conduction of the different elements in the chemical structure is different, the amount of heat input differs. This change can be observed in Table 4 with KV levels given [6], [7], [14], [26], [37]. As a result, Figure 9 (b) shows a broken QM showing a brittle structure with a lower KV level.…”

“…For example, Q345B steel is combined with different materials for use. The aim of this study is to determine and report the most suitable welding parameters for this steel [1]- [6].…”

Microstructure and creep characteristics of dissimilar T91/TP316H martensitic/austenitic welded joint with Ni-based weld metal

“…In addition, the creep resistance of these weldments was found to be rapidly reduced compared to the used base materials. The main reason for deteriorated creep strength was attributed to the formation of soft carbon-depleted zone at the bainitic side of the weld metal interface due to the carbon migration from bainitic steel to austenitic weld metal, driven by carbon activity gradient [6]. To overcome this problem, the alternative Ni-based welding consumables of Inconel-type have been introduced [1,[7][8][9].…”