Weld quality mainly depends on the weld bead geometry and mechanical-metallurgical characteristics of the welded joint which has a direct relationship with the type of welding process being used and its input process parameters i.e. welding current, arc voltage, travel speed etc. In the present study, determination of tungsten inert gas (TIG) welding input parameters for achieving maximum tensile strength of 316L austenitic stainless steel is investigated. Box-Behnken design of response surface methodology has been employed to formulate the experimental plan to identify the effect of process parameters on tensile strength. Square butt joint configuration has been made using three factors - three levels of welding input parameters. Joint strength has been evaluated by notch tensile strength (NTS) and Unnotch tensile strength (UTS) method and correlated with microstructure and micro hardness of the weld. The results indicate that gas flow rate has greater influence on both NTS and UTS followed by welding current.

AISI 316L stainless steel materials of thickness 3 mm have been united by tungsten inert gas (TIG) welding in square butt joint configuration as per Box-Behnken design technique of response surface methodology (RSM) to indentify the effects of input parameters on the quality of the TIG welded joints. The output responses have been measured after experimentation. Mathematical correlation between input parameters and output responses has been developed using RSM. The factors which influences on responses have been analyzed by generating the response surface and contour plots. Desirability function analysis (DFA) is employed for finding optimum parametric setting to achieve the most favourable mechanical properties. Microstructures of welded samples are also investigated to correlate the metallurgical-mechanical characteristics of the welded specimens. The result indicates that at the intermediate values of welding parameters create fine grain structure and superior mechanical properties.

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This paper presents the study of effect of heat input on the joint quality of tungsten inert gas (TIG) welded specimens. Three different heat input combinations selected as low heat (0.75kJ/mm), medium heat (0.90kJ/mm) and high heat (1.05kJ/mm) have been applied during the operation of TIG welding process on 316L austenitic stainless steel. Welded joints being prepared using a semiautomatic TIG welding machine, the effect of heat input is investigated on the weld bead geometry and mechanical-metallurgical characteristics of the joints. It is observed that as heat input increases, the width of weld bead increases, where as height of weld bead decreases with increasing heat input. Tensile strength as well as hardness increases with increase of heat input up to a threshold value and thereafter it start decreasing. The results of the investigation indicate that the joint prepared using medium heat input depicts higher tensile strength, percentage elongation, yield strength and higher micro hardness value than those joints made using low and high heat input due to smaller dendrite size and lesser interdendritic spacing in the weld zone and formation of very fine skeletal δ-ferrite in plain austenitic matrix. A large number of very fine and shallow dimples are observed in SEM fractograph of the joint made using medium heat input.

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