Welding processes8 GTAW
Trang 1Welding Processes – Non-Consumable Electrode
Trang 2Welding with Non-Consumable Electrode
Arc Characteristics in Argon and Helium
Trang 3Welding with Non-Consumable Electrode
Trang 4Welding with Non-Consumable Electrode
Trang 5Welding with Non-Consumable Electrode
Trang 6Welding with Non-Consumable Electrode
Trang 7Welding with Non-Consumable Electrode
Trang 8Gas Tungsten Arc Welding
Trang 9Gas Tungsten Arc Welding
An arc Welding process that uses an arc between a tungsten electrode (nonconsumable) and the weld pool The process is used with a
shielding gas and without application of pressure Filler metal may or may not be used
•.Autogenous Welding
•.Filler feeding is Cold
•.Filler is not transferred across the arc
Trang 10Gas Tungsten Arc Welding
• High quality Welds in almost all metals and alloys
• Very little, if any, postweld cleaning is required
• The arc and weld pool are clearly visible to the welder
• There is no filler metal carried across the arc, so there is little or no spatter
• Welding can be performed in all positions
• There is no slag produced that might get trapped in weld
Trang 11Gas Tungsten Arc Welding
• Thinner Materials, thin wall tubing
and root pass in pipes
• High Precision work due to extreme control
Main Consumables
• Filler Metals
• Shielding Gases
• Tungsten Electrodes
Trang 12Gas Tungsten Arc Welding
• Thinner Materials, thin wall tubing
and root pass in pipes
• High Precision work due to extreme control
Main Consumables
• Filler Metals
• Shielding Gases
• Tungsten Electrodes
Trang 13Gas Tungsten Arc Welding
Main Consumables
• Filler Metals
• AWS Provide specifications for filler metals
• Uses straight lengths of rods for manual application
• Automatic applications uses metal wire from coils or spools
• Tungsten Electrodes
Trang 14Gas Tungsten Arc Welding
Main Consumables
• Shielding Gases
• Must be an inert gas – Only Argon and Helium are used (others too expensive)
• Argon is more common – Heavier than Helium, Air (efficient shielding at lower flow rates) and easily available
• Argon is better for arc starting and operates at lower voltage
• Helium is lighter – higher flow rates are required
• Provides higher voltage and higher heat in the arc (also possible to weld at a higher speed)
• Sometimes a mixture is used
Trang 15Gas Tungsten Arc Welding
Trang 16Gas Tungsten Arc Welding
• Mostly the same as for SMAW
• Related to Design for Welding
• Follow the schedule
• Currents are based on type of metal and joint detail
• Preselected variables are tungsten type, tungsten size, nozzle size and gas type (part of a welding procedure)
• Primary variables are welding current, arc voltage, travel speed, pulsing (if used), upslope and downslope for
programmed welding
• Secondary variable include rod feed speed, torch angles and possibly tungsten angles
• Factors of interests are penetration, bead width or weld reinforcemnt
Trang 17Gas Tungsten Arc Welding
• Better than any of the arc welding processes
• Highest quality obtained when all precautions are taken
• Cleanliness plays a critical role (joints, worktables, fixtures, filler etc)
• Welder skill also is critical
10 Suitability For Materials
Trang 18Gas Tungsten Arc Welding
• Pulsed-Currnet GTAW