Abstract
Activated TIG welding has been performed on Al – 8% SiC composite 5mm plate with various fluxes such as Al2O3, MnO2, CaO, MgO, SiO2 & TiO2, to study & analyze the Microstructure, Micro hardness and cooling rate. Correlation study between micro hardness, microstructure and cooling rate for Constant Current TIG welding and Activated TIG welding on Al-SiC composite are also carried out to analyze the relation between the effect of cooling rate on microstructure & the effect of microstructure on micro hardness. The experimental results of ATIG welding on Al-SiC composite shows fine grain weld microstructure on ATIG – SiO2 & ATIG – TiO2, which results in higher micro hardness. Micro hardness values are taken in different locations of weld surface at 1mm, 2mm & 3mm below the weld surface and the same is also observed along the weld zone to heat affected zone upto 12mm for the center of the weldment. Minimum micro hardness values found in ATIG – MnO2, ATIG – CaO & ATIG – MgO are due to intermediate micro structure between coarse and fine in heat affected zone. ATIG – Al2O3 weld zone & heat affected zone and heat affected zone of ATIG – MnO2, ATIG – CaO & ATIG – MgO shows coarse microstructure leading to reduction in micro hardness value. Cooling rate for the different CCTIG & ATIG welding are recorded and correlation between the micro structures are studied. Coarse micro structure in weld zone and heat affected zone have least cooling rate whereas fine micro structure in weld zone resulted at higher cooling rate. Heat affected zone strongly depends on temperature gradient between the weld center and weldment’s heat affected zone.
Highlights
Gas Tungsten Arc Welding (GTAW) known as Tungsten Inert Gas (TIG) welding showed high quality weld than other arc welding process
During welding, cooling rate at 10mm away weld zone was calculated from time - temperature profile acquired using data acquisition system (DAQ) through LabView software coupled with National Instrument NI cDAQ 9174 kit which employs a temperature acquiring module -NI 9211 with K type thermocouple
Correlation between micro hardness, microstructure and cooling rate of Constant Current TIG welding and Activated TIG welding on Al-SiC composite has been studied and validated
Summary
Gas Tungsten Arc Welding (GTAW) known as Tungsten Inert Gas (TIG) welding showed high quality weld than other arc welding process. Since non ferrous metals requires quality weld with reduced defects and improved mechanical properties of the weld, TIG welding is considered to be more suitable and appropriate welding process. To reduce the heat input into weld the Activated TIG welding (ATIG) a new variant was found out. ATIG welding process was developed in early 1960's by the Paton Welding Institute, Ukraine to improve the weld penetration [3, 4]. By improving the weld penetration, number weld passes get reduced by reducing the weld pass the heat input given the weld material is get reduced [5]. The activated flux TIG welding may have two types of mechanisms that are mostly accepted, first one is based on the reverse Marangoni convection effect[6,7,8], and the other one is based on arc construction effect [9, 10]
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