Abstract
Aiming at existing methods unable to reveal the definition of dilution in welding accurately, such as the limited formula’s range of 0~1 mathematically, a new way which can be widely applied to various welds alloying either one or more compositions was proposed. Dilution values obtained using different methods through chemical composition analysis were compared and the effect of heat inputs on dilution was researched. The results show that the proposed method fabricated mathematically agrees well with the definition of dilution in welding. Especially, by dilution increasing to a level higher than the critical value, it reveals the fact that a weld can be concentrated as well when the filler wire is rich in the same composition as the substrate does. Besides, the method demonstrates that the gross dilution for a bead is a combined result that is affected by each individual composition. However, whether a composition is diluted or concentrated, composition’s concentrations are propelled by the increase of heat input toward that of the original substrate. During the process, the dilution value changes sharply before the heat input reaches the transition point (TP) of 0.18 kJ/mm, while once the heat input is beyond TP, the dilution becomes stable.
Highlights
Dilution is a significant factor affecting the mechanical property of bead in gas metal arc welding (GMAW) [1,2,3,4,5]
In welding the substrate is undoubtedly diluted by the filler wire, the dilution ratio cannot be expressed as Equation (1) [12], which irrationally correlates the original concentration of the substrate and the filler wire just to make it easier for the dilution calculation
Dilution is defined as the level at which the composition(s) in substrate mixes with that in the filler wire [17], it can be determined as a ratio of the compositions concentration in fusion zone to that in original substrate, which can be expressed mathematically as Equation (3)
Summary
Dilution is a significant factor affecting the mechanical property of bead in gas metal arc welding (GMAW) [1,2,3,4,5]. Considering that the dilution values obtained from the two techniques are quite close [11], most researchers adopted the geometric calculations method to calculate the dilution in various processes owing to its simplicity and efficiency compared with the chemical analysis [12,14,17,18]. These two methods, cannot reflect the definition of dilution in welding well and accurately. It can be only employed to assess the weld alloying one element but not able to measure the gross dilution for a weld containing more compositions [13,16], for which case its only value cannot be used to represent different dilution ratios
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