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Shielding Gases - A major consumable in Welding. On an average 2 Tons of gas used per tonne of wire Extensive research on Shielding gases to improve welding performance quality and economy CO 2 widely used previously, now replaced with Argon based mixtures
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Shielding Gases - A major consumable in Welding • On an average 2 Tons of gas used per tonne of wire • Extensive research on Shielding gases to improve welding performance quality and economy • CO2 widely used previously, now replaced with Argon based mixtures • With improved Argon availability, rapidly increasing application in India
Shielding Gas Functions • Protects the weld from atmospheric contamination • Stabilises the welding arc • Defines metal transfer mode along with welding parameters • Controls weld geometry • Controls weld composition / properties
Effect of CO2 and O2 on welding speed( 4mm throat fillet on 6mm plate)
Direct Welding Cost Elements UK INDIA
Spatter generated1 metre of weld at 260 amps using 1.2mm dia. A18 solid wire CO2 19.1 grams Argon/CO2 Mix. 8.6 grams Argon/CO2/Oxy Mix 5.5 grams
Benefits of using gas mixturesThree component with oxygen • Improved arc stability leading to lower spatter loss • Improved weld bead geometry leading to weld metal saving • Faster welding speeds leading to higher productivity and reduced labour costs • Improved weld quality leading to lesser rejects • Reduced clean up time • Lower distortion
Benefits of using gas mixturesThree component with oxygen • Improved aesthetics due to bright bead and neat finish • Higher weld metal strength and toughness • Reduced welder fatigue due to ease of welding • Lower distortion • Lower fume levels than Argon/CO2
MODES OF METAL TRANSFER • DIP TRANSFER Low current - low voltage used to produce short circuiting arc, freq. 200 times / minute. Used for sheet metal and postional welding • SPRAY TRANSFER Higher currents and voltage used , droplet size same as or lower than the wire diameter. Higher deposition rate penetration and fluidity of the molten pool , increases the productivity
MODES OF METAL TRANSFERCONTD. • GLOBULAR TRANSFER An intermediate stage between dip and spray transfer . droplet sizes are more than the wire dia . Produces excessive spatter and erratic arc behavior viz. CO2 • PULSED TRANSFER Controlled method of spray transfer. Heat input to the job is controlled by low background current with high pulses using special type of equipment