Presentation on theme: "GTAW (TIG). Definition Gas Tungsten Arc Welding (GTAW) is an arc welding process that uses a non consumable tungsten electrode to establish the arc and."— Presentation transcript:
Definition Gas Tungsten Arc Welding (GTAW) is an arc welding process that uses a non consumable tungsten electrode to establish the arc and gas from a cylinder to provide shielding. The filler metal is supplied by a manual rod. 2 Also called Tungsten Inert Gas (TIG) welding.
Machine Functions 1Store and provide shielding gas at the correct rate 2Provide desired welding current 3Variable current control 4Store and circulate water through the torch (watered cooled) 5Semiautomatic control
Machine Nomenclature A.Torch B.Power switch C.AC balance control D.Mode switch E.Digital Amp meter F.Output (Amp) control G.Cylinder H.Flow meter I.Roto meter J.Flow control valve K.Regulator L.Post flow timer M.Pulse frequency control N.Polarity switch O.Output connector P.Remote pedal Q.Ground clamp R.Remote receptacle Explain the function(s) of each one of these controls/parts.
Torch Nomenclature A.Cap B.Collet C.Torch body D.Collet body E.Gas orifice F.Cup G.Electrode What is the function of each part? How are GTAW torches cooled?
Introduction HeatShieldingFiller metal GTAW How does the GTAW process meet the three requirements of arc welding?
Hazards Associated with GTAW Hot metal Harmful rays Fumes High frequency RF Flying objects Loud Noise What is the best management practices for these hazards?
Heat The heat produced by an electric arc between the nonconsumable tungsten and the metal is sufficient to melt the base metal and the filler rod. What determines the amount of heat produced by the electric arc? For the TIG welding process, is the current adjusted by changing the amperage or the voltage?
Heat – Currents Three common currents: DC- DC+ AC--HF Note: many power supplies have the option of pulsed current for better puddle control. Why is HF (high frequency) used with AC?
Heat – Current - Polarity For the best welds, and ease of welding, the correct current must be used for the metal being welded.
Heat - Tungsten The tungsten electrode is nonconsumable and is used to form the arc between the torch and the metal. Different alloys of tungsten are available. EWP100 % TungstenGreen EWTh-22 % ThoriumRed EWZr-11 % ZirconiumBrown EWCe-22 % CeriumOrange EWLa-22 % LanthanumBlack Good arc stability with AC Better Arc with DC AC when high weld quality is required Better starting, higher current 50% greater current capacity with AC ID% AlloyColorCharacteristic Which alloy/color should be used when welding thicker aluminum with AC?
Heat – Tungsten - Preparation The shape of the tungsten electrode end must be appropriate for the current being used. ACHemispheric or balled end no more than 1.5 times the electrode diameter. Grinder lines parallel with electrode. DC-Needle point for very thin metal, blunt point for thicker metal. Taper = 2 to 2-1/2 times the diameter. What does it mean if the end of the electrode appears dull? What does it mean if the end of the electrode is blue or blackened? How long should the the shielding gas flow after the welding has stopped?
Shielding In the GTAW process shielding is supplied from a cylinder. For best results the shielding gas must be appropriate for the type and thickness of metal. How is the flow of the shielding gas controlled? How much gas (ft 3 ) will each gallon of liquid argon produce?
Filler Metal A welding rod is used to fill in the joint. Most common type is 36 inch rods that are fed into the weld pool by hand. What are three important characteristics of GTAW rods?
Preparation for Welding Three (3) steps in preparing to weld: 1Safety check 2Metal preparation 3Set up machine
Preparation - Safety 1Check the machine, cables, torch and ground clamp. 2Insure the helmet is in good condition and the correct shade of lens. 3Cover all exposed skin.
Preparation – Metal – Aluminum Contamination is the biggest problem when welding aluminum with the GTAW process. The metal must be cleaned with a stainless steel wire brush. The brush can only be used to clean aluminum. Must clean the adjoining faces and the back edge Insure the filler rod is clean also.
Preparation - Machine Attach the GTAW torch to the output connector. Attach the remote control pedal to the remote receptacle. Position the polarity switch on AC. Turn on the machine. Insure the torch is not grounded Set the mode switch to TIG Set the amperage. 150 amp maximum for air cooled torch. Set the AC balance control. Set the pulse control. Set the postflow timer.
Preparation – Machine - Torch If the torch has been used to weld carbon steel or stainless steel then the cup and electrode must be replaced. The tungsten electrode must be clean and the correct shape. The torch cup must be clean The electrode must be set with the correct stickout.
Setting Amperage Aluminum is a good conductor of heat. Aluminum melts at a lower temperature that steel. Aluminum Amperage ACHF ThicknessJoint Tungsten electrode diameter Filler rod diameterAmperage Gas TypeCFH 1/8 in Butt3/32 – 1/8 in3/32 in125 - 150Argon20 Lap3/32 – 1/8 in3/32 in130 - 160Argon20 Corner3/32 – 1/8 in3/32 in120 - 140Argon20 Fillet3/32 – 1/8 in3/32 in130 - 160Argon20 3/16 in Butt1/8 – 5/32 in1/8 in180 - 225Argon20 Lap1/8 – 5/32 in1/8 in190 - 240Argon20 Corner1/8 – 5/32 in1/8 in180 - 225Argon20 Fillet1/8 – 5/32 in1/8 in190 – 240Argon20 1/4 in Butt5/32 – 3/16 in 3/16 in240 - 280Argon25 Lap5/32 – 3/16 in 3/16 in250 – 320Argon25 Corner5/32 – 3/16 in 3/16 in240 - 280Argon25 Fillet5/32 – 3/16 in 3/16 in250 - 320Argon25
Troubleshooting GTAW Troubleshooting is the process of determining the cause of a problem. Assumes the welder is in proper working order. Requires gathering information and a logical thought process.
Troubleshooting - 1 ProblemCause Excessive electrode consumption Inadequate gas flow DCEP electrode Excessive current density Tungsten oxidation during cooling What would you do to remedy these causes?
Troubleshooting - 2 ProblemCause Aluminum contamination of electrodeElectrode contacting filler rod Electrode contacting metal What would you do to remedy these causes?
Troubleshooting - 3 ProblemCause Weld porosity and dark colorCondensation in system Atmospheric contamination Contaminated filler metal Contaminated base metal What should be done to remedy these causes?
Troubleshooting - 4 ProblemCause Yellow powder or smoke on cupInsufficient gas flow Atmospheric contamination Inadequate post flow Incorrect shielding gas What should be done to remedy these causes? Incorrect tungsten size or cup size