Shielding Gases - A major consumable in Welding l On an average 2 Tons of gas used per tonne of wire l Extensive research on Shielding gases to improve welding performance quality and economy l CO 2 widely used previously, now replaced with Argon based mixtures l With improved Argon availability, rapidly increasing application in India

Shielding Gas Functions l Protects the weld from atmospheric contamination l Stabilises the welding arc l Defines metal transfer mode along with welding parameters l Controls weld geometry l Controls weld composition / properties

Shielding Gases for Arc Welding processes

Spatter generation from Argon-CO 2 mixtures

Fume Formation Rate CO 2 vs. Argon mixture

Effect of CO2 and O2 on welding speed ( 4mm throat fillet on 6mm plate)

Gases for GMAW of Carbon / low alloy steels

Shielding gas profiles & effect on weld length

Savings with Argon / CO 2 / O 2 gas mixtures

Direct Welding Cost Elements UK INDIA

Spatter generated 1 metre of weld at 260 amps using 1.2mm dia. A18 solid wire CO grams Argon/CO2 Mix. 8.6 grams Argon/CO2/Oxy Mix 5.5 grams

Benefits of using gas mixtures Three component with oxygen l Improved arc stability leading to lower spatter loss l Improved weld bead geometry leading to weld metal saving l Faster welding speeds leading to higher productivity and reduced labour costs l Improved weld quality leading to lesser rejects l Reduced clean up time l Lower distortion

Benefits of using gas mixtures Three component with oxygen l Improved aesthetics due to bright bead and neat finish l Higher weld metal strength and toughness l Reduced welder fatigue due to ease of welding l Lower distortion l Lower fume levels than Argon/CO2

MODES OF METAL TRANSFER l DIP TRANSFER Low current - low voltage used to produce short circuiting arc, freq. 200 times / minute. Used for sheet metal and postional welding l 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 TRANSFER CONTD. l 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 l 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