In welding processes, many factors contribute in achieving a required quality of the welds. Those factors are numerous and they may interact with each other, affecting response parameters such as welding penetration and the Heat Affected Zone (HAZ) size. Some factors are more important while the influence of others is negligible.To find an optimum factor combination in order to maximize penetration and minimize the HAZ is not an easy task. This contribution is aimed to evaluate the influence of welding energy (E) versus the influence of current (I) and welding speed (Vw) on the penetration and HAZ volume in the autogenous Tungsten Inert Gas (TIG) welding process. For this purpose, phenomenological and empirical models are proposed. The first considers an in-house Finite Volume numerical model, and the second is based on Response Surface Method. A sensitivity analysis of the empirical model using two strategies is also performed. In addition, to determine the best-operating conditions, a multi-objective optimization problem is proposed and solved. The presented empirical models were found to provide good concordance in terms of coefficient of determination and p-value, indicating its significance. Each model (with one or more independent variables) represents detailed information about the physical process and can be used for optimization. The sensitivity analysis demonstrates that the current affects penetration and HAZ volume much stronger than the welding speed does. Physically, this is due to the fact current has linear (arc coupling) and non-linear (Joule effect and pressure gradient) influence, and the welding speed contributes linearly, modulating the heat conduction. Finally, it was demonstrated a compromise between the penetration and the HAZ volume by addressing multi-objective optimization. In this context, point C (I = 250 A; VW= 24.8 cm/min) of the Pareto curve is the optimal option for operation since it provides a lower relative HAZ volume while keeping the same penetration and higher productivity (welding speed).

In the present paper, the information on the influence of various factors on the carbon block cartridges production technology and their potential impact on the properties of the finished product is presented. The possibilities of increasing the sorption-filtering efficiency of carbon block cartridges are presented. The technical and exploitation characteristics are influenced by the size of the mixture components granules, the physicochemical properties of active carbon and binder polymers, their ratio in the mixture, and the addition of bactericidal additives into the composition. The study of this topic is relevant, as evidenced by the analysis of the increasing number of publications on this matter over the past ten years. However, the production technology of carbon block cartridges is the know-how of manufacturing companies. This information is confirmed by the analysis of the technical characteristics of sixty carbon block cartridges from nine world manufacturers, whose products are WQA certified according to the NSF/ANSI 42 standard. The recommendations given by a number of authors on the size of activated carbon granules in the range from 40 to 120 mesh and polyethylene particles from 80 to 160 mesh with a flow rate of 1.4-3 g/10 min, can be taken as "reference points" in the development of extrusion mixtures with different components ratio. The following factors play an important role in obtaining effective cartridges: the quality of pre-extrusion mixing of the composition, its resistance to delamination during the “transition” from the mixer to the extruder loading zone, extrusion temperature regimes by zones, product cooling temperature, backpressure on the billet leaving the extruder. The information given in this article will be useful when producing new carbon block cartridges, improving the parameters of existing technologies, as well as in the research development of cartridges with new properties.

In welding processes, many factors contribute in achieving a required quality of the welds. Those factors are numerous and they may interact with each other, affecting response parameters such as welding penetration and the Heat Affected Zone (HAZ) size. Some factors are more important while the influence of others is negligible. To find an optimum factor combination in order to maximize penetration and minimize the HAZ is not an easy task. This contribution is aimed to evaluate the influence of welding energy ( E ) versus the influence of current ( I ) and welding speed ( V w ) on the penetration and HAZ volume in the autogenous Tungsten Inert Gas (TIG) welding process. For this purpose, phenomenological and empirical models are proposed. The first considers an in-house Finite Volume numerical model, and the second is based on Response Surface Method. A sensitivity analysis of the empirical model using two strategies is also performed. In addition, to determine the best-operating conditions, a multiobjective optimization problem is proposed and solved. The presented empirical models were found to provide good concordance in terms of coefficient of determination and p-value, indicating its significance. Each model (with one or more independent variables) represents detailed information about the physical process and can be used for optimization. The sensitivity analysis demonstrates that the current affects penetration and HAZ volume much stronger than the welding speed does. Physically, this is due to the fact current has linear (arc coupling) and non-linear (Joule effect and pressure gradient) influence, and the welding speed contributes linearly, modulating the heat conduction. Finally, it was demonstrated a compromise between the penetration and the HAZ volume by addressing multiobjective optimization. In this context, point C ( I = 250 A; V W = 24.8 cm/min) of the Pareto curve is the optimal option for operation since it provides a lower relative HAZ volume while maintaining the same penetration and higher productivity (welding speed).

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