Indian Welding Journal

P. C. Gupta ¹, P. K. Ghosh ¹

Affiliations
1 Dept. of Mechanical and Industrial Engineenng, Welding Research Laboratory, University of Roorkee, Roorkee-247 667, IN

Abstract

Developments of new materials, requirements of sophisticated constructions and the demand for an assurance of safety in service, calls for development of technologies which shall satisfy the service requirements and produce goods of best quality and reliability at competitive cost. Welding technology is emerging as one of the key technologies of twenty first century, the application of which can not be avoided in various works ranging from the building construction and erection of onshore and offshore structures to underwater constructions, surface transportation, aerospace vehicle manufacturing and construction of nuclear vessel.

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P. C. Gupta ¹, P. K. Ghose ¹, S. K. Sharma ¹

Affiliations
1 Welding Research Laboratory, Deptt. of Mechanical & Industrial Engg., University of Roorkee, Roorkee - 247 667, IN

Abstract

The influence of polarity at various levels of welding currents varying from 300 Amp to 700 Amp between the arc voltage of 28 volt and 32 volt on the melting rate, and the bead geometry has been investigated. It has been observed that at a given value of welding current and voltage the melting rate is larger at DCEN as compared to that at DCEP. At a given arc voltage the difference in melting rate increases with the increase in current. However, at a given welding current the variation in crc voltage shows an insignificant effect on melting rate under straight polarity (DCEN). The DCEN produces an irregular bead shape due to piling up of metal deposition and gives lower penetration along with lower bead width and higher bead height than those observed at DCEP.

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P. C. Gupta ¹, D. Rehfeldt ², F. Erdmann-Jesnitzer ³

Affiliations
1 Department of Mechanical and Industrial Engineering, University of Roorkee, Roorkee, IN
2 Welding Department, Institute of Material Science, Technical University, Hannover, DE
3 Institute of Material Science, Technical University, Hannover, DE

Abstract

Although a number of reports (1-6) are available on the application of longitudinal magnetic field during submerged arc welding, it is far from clear how much is the influence of such magnetic field on weld cross section affected by the selection of welding parameters.

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P. K. Ghosh ¹, H. M. Hussain ², P. C. Gupta ¹

Affiliations
1 Welding Research Laboratory, Dept. of Mech. & Industrial Engg., University of Roorkee, Roorkee-247667, IN
2 PO. Box 61263, Hoon, LY

Abstract

The growing interest of using thick section of high strength aluminum alloy like Al- Zn-Mg in the fabrication of lightweight large transport container and pressure vessels necessitates the gas metal arc welding (GMAW) of this alloy. Due to its high strength, the weld joint of AI-Zn-hAg alloy is highly sensitive to fatigue failure, thus in any engineering application, an assurance about its desired tensile, fatigue and fracture toughness properties are of utmost importance. In the light of the recent observations on the superiority of using pulsed current GMAW over the conventional continuous current one to improve the mechanical properties of single pass weld of A/-Zn-Mg alloy, the present investigation has been planned to study the characteristics of multipass weld of thick section of this alloy prepared by employing pulsed current GI^AW process. The multipass welding of 25mm thick extruded section of an Al-Zn-Mg alloy has been carried out using pulsed current and continuous current gas metal arc welding (GMAW) processes. The welding has been carried out by employing 1.6mm diameter AI-!\/lg ('/41VS ASME: SFA-5.10 ER 5183) filler wire and commercial argon as shielding gas. The pulsed current welding has been performed by varying the pulse parameters such as the pulse frequency and duration and their effects on dilution, zinc pick-up, precipitation behavior, porosity content and tensile properties of the weld are studied. It is observed that the variation in pulse parameters affects the microstructure and dilution of weld deposit. The change in weld dilution has been found to control its chemistry (especially zinc level) and precipitate content dictating tensile properties of the weld. The characteristics of the pulsed current weld has been compared to those of the weld prepared by continuous current GMAW. The properties of the pulsed current weld are found superior to those of the conventional continuous current weld.

Keywords

Al-Zn-Mg Alloy, Pulsed and Continuous Current GMAW, Multipass Weld, Weld Chemistry, XRD Analysis, Porosity Microstructure, Fractography Mechanical Properties.

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P. K. Ghosh ¹, P. C. Gupta ¹

Affiliations
1 Welding Research Laboratory. Deptt. of Mech. and Ind. University of Roorkee. Roorkee 247 667, IN

Abstract

Extruded sections of commercial Al-Zn-Mg alloy have been welded by continuous and pulsed current MIG welding processes, using 1.6mm diameter Al-Mg filler wire. During welding the current and other pulse parameters such as its frequency and duration are varied and their influence on the weld bead geometry, chemical composition, hardness and porosity content are studied. The influence of various parameters on the recrystallization at HAZ adjacent to the fusion line has been examined. Finally the performance of the weldments under static and dynamic tensile loading are also investigated. The properties of the weldments prepared under pulsed MIG process are correlated to those of the weldments prepared by the conventional continuous current welding. It has been observed that a critical and selective use of pulse parameters improve the weldment properties as compared with those of the conventional weldments.

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S. R. Gupta ¹, P. C. Gupta ¹, S. N. Dubey ¹

Affiliations
1 Department of Mechanical & Industrial Engineering, University of Roorkee, Roorkee, IN

Abstract

Experimental investigations have been carried out to study the influence of various welding variables on arc efficiency in TIG (GTA) process using water cooled copper block as work piece. Heat collected by the water flowing through the hollow block, has been used to calculate the arc efficiencies. It has been shown that the welding current, arc length and electrode polarity have appreciable influence on the arc efficiencies over the entire range of investigations. Gas flow rate and torch angle also influence efficiency significantly but only under certain conditions.

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