Moinuddin, S Q and Sharma, Abhay (2018) ASSESSMENT OF ARC STABILITY AND ITS IMPACT IN ANTI-PHASE SYNCHRONIZED TWIN-WIRE GAS METAL ARC WELDING. PhD thesis, Indian institute of technology Hyderabad.

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Gas Metal Arc Welding (GMAW) process is a well-established process, widely used in industries due to its economic efficiency. The present scenario in industries is to increase the productivity with low cost. Due to this necessity, improvement of existing process and development of new process came in to existence with help of advanced technology. One such process is arc-welding process wherein single wire has extended to multiple-wire welding process. Twin-wire welding process is one of a kind in multiple-wire welding process that has been fully developed and used at shop floor. This technique was first implemented in submerged arc welding process later on gas metal welding process. From literature, it is known that submerged arc twin-wire welding process has been full-fledged developed, whereas gas metal arc welding is in developing stage. The major concern in twin-wire gas metal arc welding is that arc interactions caused by electromagnetic fields affect arc stability of the process. The present work addresses the solution to this issue with help of experimental study. Process parameters such as current values and wire diameters at lead and trail position were considered as variables. Bead-onplate experiments conducted on low carbon alloy steel. Welding signals were captured with the help of data acquisition system. A qualitative (cyclograms and probability density distribution) and quantitative analysis (wavelet energy entropy) were carried out on stability of the process. Further, mathematical formulation has developed to calculate the melting efficiencies that has been related to arc stability, heat input and weld bead features. The interconnection between process – structure – properties has been analyzed. The two-stage arcing in twin-wire welding facilitates slow heating and cooling that leads to weld metal and heat affected zone softening. A combination of polygonal ferrite, pearlite, and bainite with varying compositions are observed across the weldment. Hardness in the heat affected zone and weldment reduced with increase in heat input. The maximum transverse residual stresses found at the weld toe region that is close to the yield strength of the base material. From the combined analysis, the present investigation suggest that for a stable arc the current value at lead should be more than trail and current difference between them should be large. In addition the wire diameter at lead should be large than trail. Combination of both process variables allow the process with stable metal transfer with reduced arc interactions. The difference in process variables between lead and trail wire has made the arc to concentrate towards one wire and withdraw sufficient energy to interact with fresh material and thereby enhanced structure along with properties. The scope of the present work in future may be directed towards the additive manufacturing, fabrication of functionally graded material using two different electrodes. Applications in which the present work can be utilized includes joining huge pipes for oil industries, boilers, automotive industries, subway transportation industries and shipbuilding industries etc

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IITH CreatorsORCiD
Item Type: Thesis (PhD)
Subjects: Others > Mechanics
Divisions: Department of Mechanical & Aerospace Engineering
Depositing User: Team Library
Date Deposited: 03 Aug 2018 12:01
Last Modified: 21 Sep 2019 07:25
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