Abstract
Welding distortion is a critical issue as it leads to severe deterioration of structural integrity of welded work piece and dimensional precision. This study aims at studying the effects of shielded metal arc welding (SMAW) parameters on the evolution of mechanical properties, including tensile strength, impact toughness, and hardness, along with angular distortion on a welded joint from SA 516 grade 70. Such parameters are analyzed and optimized by employing the Taguchi method and Grey relational analysis. SA 516 grade 70 is commercially used for fabrication of storage tanks, boilers and pressure vessels. SMAW is investigated with three levels of root gap, groove angle, electrode diameter, and pre-heat temperature, which were varied on a butt joint in flat (1 G) position to determine their effects on response variables at room temperature. Nine experiments were designed using a Taguchi L9 orthogonal array, welded according to American Society of Mechanical Engineers (ASME) section IX, and samples were prepared and tested as per ASTM A 370. The Taguchi method and Grey relational analysis were employed to observe the most significant parameters and optimal levels that synergically yield improved responses. Results are validated by conducting confirmatory experiments that show good agreement with optimum results.
Highlights
In small to heavy industries, steel is utmost important material for fabrication, structural components, weapons and machines due to low cost, high tensile strength and considerable toughness [1, 2]
The Anderson Darling (ADT) test, a powerful statistical tool generally employed for outlier detection from normality, is employed for validation of normality assumption [47]
Confirmation experiment was conducted on optimal levels of welding parameters identified by Grey relational analysis (GRA) and W-GRA to evaluate and verify the improvement in quality response of SMA weld joint on SA 516 grade 70
Summary
In small to heavy industries, steel is utmost important material for fabrication, structural components, weapons and machines due to low cost, high tensile strength and considerable toughness [1, 2]. Shielded metal arc welding (SMAW) is oldest, most rapid, convenient, and commonly used joining process for the fabrication of variety of products such as pressure vessels, gears, machines, ship hulls, mining equipment, boilers, etc. SMAW results in good quality when employed for construction, pressure vessels, military armors, and vehicles [3]. SMAW is a multi-objective process involving multiple parameters, such as welding speed, electrode diameter, root gap, welding current, groove angle, and polarity, the judicious and precise setting of which results in targeted weld quality [5]. Efficient, and sound when the deposition rate is maximum [6]
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