Browsing by Author "Kumar, P.A."

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    Effect of filler wire strength on high strength low alloy steels
    (Elsevier Ltd, 2021) John, M.; Kumar, P.A.; Bhat, K.U.
    Fusion welding of Ti-Nb microalloyed steels often leads to softening in the heat affected zone (HAZ) due to weld thermal cycles. Apart from heat input and width of HAZ, selection of filler wire also plays an important role, to achieve the minimum strength requirement of the parent material. Steel plates with 800 MPa ultimate tensile strength were butt welded using pulsed gas metal arc welding (P-GMAW) process, with undermatching, matching and overmatching strength filler wires. Welding parameters were selected in such a way that the heat input per unit weld length is almost constant. In all the samples, microstructural features were similar in the HAZ region. Static tensile tests indicated that failure in the samples welded using undermatching filler occurred at welded region, whereas the samples welded with matching and overmatching fillers failed at HAZ region. Further fracture studies indicated that, in case of under matching filler wire samples, crack propagates along the Widmanstatten ferrite present in the weld zone, whereas in other two samples, crack initiated at coarse TiN - matrix interface in the HAZ region. This study shows that overmatching fillers are recommended to overcome strength loss due to HAZ softening. © 2021 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the Global Conference on Recent Advances in Sustainable Materials 2021.
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    Effect of wire feed rate on microstructure development during bead on plate welding of microalloyed steel using P-GMAW
    (Elsevier Ltd, 2020) John, M.; Kumar, P.A.; Udaya Bhat, K.
    Welding of advanced high strength steel has been challenging because of difficulties associated with retaining high strength and toughness in the weldment. In this investigation, Ti-Nb microalloyed 800 MPa steel was subjected to bead on plate welding trials using ER70S-6 filler wire. Synergic pulsed mode was used for welding. Here the system could optimize the welding current and voltage once the selection of wire feed rate was done. Analysis of weld bead was done by measuring the weld bead parameters, observing microstructural details and calculating microhardness values. The investigation indicates that 6 m/min wire feed rate produces good weld bead, minimum reinforcement and optimum dilution. The microstructure is predominantly acicular in nature and microhardness in weld and HAZ is higher compared to the beads produced using other wire feed rates. © 2020 Elsevier Ltd. All rights reserved.