Conference Papers
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Item 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.Item A study on HAZ behaviour in 800 MPa cold rolled and hot rolled steel weld(Elsevier Ltd, 2021) John, M.; Perka, P.; Udaya Bhat, K.; Bhat Panemangalore, D.In the automotive sector, the demand for advanced high strength steels (AHSS) is increasing day by day. Based on the application, cold rolled and hot rolled steels are used for various components in a vehicle body. Typically, cold-rolled grades with dual-phase, DP780 steel is used in the form of welded blanks. Hot rolled grades with Ti-Nb microalloy content, like HS800 steel are used in as long members. Welding is an important step to be considered in the design of materials for mass production as required in the automobile sector. In this investigation, Pulsed Gas Metal Arc Welding (P-GMAW) is carried out on both steels with a solid filler wire of strength 800 MPa. Static tensile tests indicated that failure in both steels welds occurred in the heat-affected zone region. The crack initiation and propagation behaviour were compared in both steels. In DP780 steels, the presence of the acicular ferrite and acicular martensite resisted the crack initiation and propagation in the weld region whereas, the chaotic nature of the acicular ferrite in HS800 steel. Microstructural studies revealed that the reason for heat affected zone (HAZ) failure in HS800 steel is due to the presence of hard TiN particles with a size of more than 1 µm which causes decohesion in the matrix. In DP780 steel failure is due to the presence of tempered martensite in the subcritical heat affected zone (SCHAZ). This study divulges the influence of filler wire chemistry, dilution, and welding parameters on cold rolled and hot rolled AHSS steels used in the automotive industry. © 2021 Elsevier Ltd. All rights reserved.Item AHSS welding using undermatching filler wires and process advantages with P-GMAW(Elsevier Ltd, 2021) John, M.; Perka, P.; Udaya Bhat, K.The major challenge during welding of advanced high strength steels (AHSS) is finding an appropriate low cost filler wire which minimizes the softening in the heat affected zone (HAZ). The fabricators always prefer undermatching wires to join the thinner sections. This study reports the differences in the microstructure and mechanical properties of Ti-Nb microalloyed steel prior welded using pulse gas metal arc welding (P-GMAW) and standard gas metal arc welding (GMAW). The results indicate that the microalloyed steel welded using P-GMAW has inherent advantage over the standard GMAW. The pulses intensified the vibration perturbation in the weld puddle which cause microstructural refining and increased formation of the acicular ferrite (AF) constituent. The higher percentage of AF present in the weldment resisted propagation of the crack during static tensile test. Microhardness, ultimate tensile strength and joint efficiency during P-GMAW are much higher than the samples welded by standard GMAW. © 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.