Gtaw 03


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Gtaw 03

  1. 1. TIG Welding Introduction by Daniel Min
  2. 2. Outline► Background► Advantages and Disadvantages► Safety► Preparation for TIG Welding► Techniques for Basic Weld Joints► TIG Shielding Gases► Welding Parameters► Tungsten Electrode Selection► Conclusion ENBE 499 2
  3. 3. Background► What is TIG?  Tungsten Inert Gas► Also referred to as GTAW  Gas Shielded Tungsten Welding► InTIG welding, a tungsten electrode heats the metal you are welding and gas (most typically Argon) protects the weld from airborne contaminants ENBE 499 3
  4. 4. Background► TIG welding uses a non-consumable tungsten► Filler metal, when required, is added by hand► Shielding gas protects the weld and tungsten ENBE 499 4
  5. 5. Advantages► Welds more metals and metal alloys than any other process► High quality and precision► Pin point control► Aesthetic weld beads► No sparks or spatter► No flux or slag► No smoke or fumes ENBE 499 5
  6. 6. Disadvantages ► Lower filler metal deposition rates ► Good hand-eye coordination a required skill ► Brighter UV rays than other processes ► Slower travel speeds than other processes ► Equipment costs tend to be higher than other processes ENBE 499 6
  7. 7. Safety► Electric shock can kill.  Always wear dry insulating gloves  Insulate yourself from work and ground  Do not touch live electrical parts  Keep all panels and covers securely in place► Fumes and gases can be hazardous to your health.  Keep your head out of the fumes  Ventilate area, or use breathing device ENBE 499 7
  8. 8. Safety► Welding can cause fire or explosion.  Do not weld near flammable material  Watch for fire; keep extinguisher nearby  Do not locate unit over combustible surfaces  Do not weld on closed containers► Arc rays can burn eyes and skin; Noise can damage hearing.  Wear welding helmet with correct shade of filter  Wear correct eye, ear, and body protection ENBE 499 8
  9. 9. Safety► Hot parts can cause injury.  Allow cooling period before touching welded metal  Wear protective gloves and clothing► Magnetic fields from high currents can affect pacemaker operation.► Flying metal can injure eyes.  Welding, chipping, wire brushing, and grinding cause sparks and flying metal; wear approved safety glasses with side shields ENBE 499 9
  10. 10. Safety► Welding current can damage electronic parts in vehicles.  Disconnect both battery cables before welding on a vehicle  Place work clamp as close to the weld as possible ENBE 499 10
  11. 11. Preparation for TIG Welding► Basic preparations should be made before establishing an arc, including base metal prep, set up of the machine and its controls► Picture on right shows front panel of a typical AC/DC machine designed for TIG welding (L-TEC HELIARC 306)► Control functions of the L-TEC HELIARC 306 are named in the following slides, but the manual should be consulted for more detail► Not all power sources will have all the features or controls of this machine ENBE 499 11
  12. 12. Preparation for TIG WeldingControl Functions► A: Power On-Off Switch► B: Tig-Stick Mode Switch► C: Remote Contactor Receptacle► D: Current Selector Switch► E: Current Range Selector Switch► F: Current Control Potentiometer► G: Current Panel-Remote Switch and Remote Current Control Receptacle► H: Post Flow Control► I: High Frequency Selector Switch► J: High Frequency Intensity Control ENBE 499 12
  13. 13. Preparation for TIG WeldingControl Functions► K: Gas and Water Torch Connections► L: Soft Start Switch► M: Arc Force Potentiometer► N: Slope/Spotweld Control Module► O: AC/DC Analog Meter Module► P: Panel Mounted Pulse Control► R: Balance Control Feature► S: Front Panel 3-Amps Fuse► T: Rear Panel Auxiliary 115V Receptacle ENBE 499 13
  14. 14. Preparation for TIG WeldingPreparing the Weld Joint► Many problems are a direct result of using improper methods to prepare the weld joint► One of the most common is the improper use of grinding wheels► Soft materials like aluminum may get embedded with abrasive particles resulting in excessive porosity► Grinding wheels should be cleaned and dedicated only to the material being welded ENBE 499 14
  15. 15. Preparation for TIG WeldingCleaning► Oil, grease, shop dirt, paint, marking crayon, and rust or corrosion deposits must be removed from the joint and metal surfaces to a distance beyond the heat affected zone► Their presence may lead to arc instability and contaminated welds ENBE 499 15
  16. 16. Preparation for TIG WeldingPreparing Aluminum for Welding► Very susceptible to contaminants► Surface oxide must be removed► Special abrasive wheels are available for aluminum► Stainless steel wire brushes recommended► Both sides of the joint should be cleaned if it contains foreign material ENBE 499 16
  17. 17. Preparation for TIG WeldingPreparing Stainless Steel for Welding► Should be thoroughly cleaned► Foreign material may cause porosity in welds and carburetion of the surface which decreases the corrosion resistance► Stainless steel wire brushes recommended ENBE 499 17
  18. 18. Preparation for TIG WeldingPreparing Titanium for Welding► Essential that weld area and filler metal be cleaned► Mill scale, oil, grease, dirt, grinding dust, and any other contamination must be removed► If titanium is scale free, only degreasing required► Joint should be brushed with stainless steel wire brush and degreased with acetone► Be cautious of fine titanium dust particles as they are flammable ENBE 499 18
  19. 19. Preparation for TIG WeldingPreparing Mild Steel for Welding► Should be mechanically cleaned► Scale, rust, paint, oil, grease, or any surface contaminants should be removed ENBE 499 19
  20. 20. Techniques for Basic Weld Joints Arc Length ► Arc length normally one electrode diameter, when AC welding with a balled end electrode ► When DC welding with a pointed electrode, arc length may be much less than electrode diameter ENBE 499 20*Figure copied from “TIG Handbook”
  21. 21. Techniques for Basic Weld Joints Gas Cup Size ► Inside diameter of gas cup should be at least three times the tungsten diameter to provide adequate shielding gas coverage ► Picture on right shows example of gas cup size and torch position 1-Workpiece, 2-Work clamp, 3-Torch, 4-Filler rod, ENBE 499 5-Gas cup, 6-Tungsten electrode 21*Figure copied from “TIG Handbook”
  22. 22. Techniques for Basic Weld JointsElectrode Extension► Refers to distance the tungsten extends out beyond the gas cup► May vary from flush with the gas cup to no more than the inside diameter of the gas cup► Longer the extension, the more likely it may contact something by accident► General rule would be to start with an extension of one electrode diameter ENBE 499 22
  23. 23. Techniques for Basic Weld Joints Arc Starting with High Frequency ► Torch position on left shows recommended method of starting the arc with high frequency when the torch is held manually ► By resting gas cup on base metal there is little danger of touching the electrode to the work ► After arc is initiated, torch can be raised to proper welding angle ENBE 499 23*Figure copied from “TIG Handbook”
  24. 24. Techniques for Basic Weld Joints Manual Torch Movement ENBE 499 24*Figure copied from “TIG Handbook”
  25. 25. Techniques for Basic Weld JointsManual Torch Movement► Torch and filler rod must be moved progressively and smoothly so the weld pool, the hot filler rod end, and the solidifying weld are not exposed to air that will contaminate the weld metal area or heat affected zone► When arc is turned off, postflow of shielding gas should shield the weld pool, electrode, and hot end of the filler rod ENBE 499 25
  26. 26. Techniques for Basic Weld Joints Butt Weld and Stringer Bead ► Be sure to center weld pool on adjoining edges ► When finishing a butt weld, torch angle may be decreased to aid in filling the crater Torch and rod position for welding the butt weld and stringer ENBE 499 bead 26*Figure copied from “TIG Handbook”
  27. 27. Techniques for Basic Weld Joints Lap Joint ► Pool is formed so that the edge of the overlapping piece and the flat surface of the second piece flow together ► Torch angle is important because the edge will become molten before the flat surface ► Enough filler metal must be added to fill the joint as illustrated on the right Torch and rod position for welding the lap joint ENBE 499 27*Figure copied from “TIG Handbook”
  28. 28. Techniques for Basic Weld Joints T-Joint ► Edge will heat up and melt sooner ► Torch angle illustrated will direct more heat onto the flat surface ► Electrode may need to be extended further beyond the cup in order to hold a short arc Torch and rod position for welding the T-joint ENBE 499 28*Figure copied from “TIG Handbook”
  29. 29. Techniques for Basic Weld Joints Corner Joint ► Both edges of the adjoining pieces should be melted and the pool kept on the joint centerline ► Sufficient filler metal is necessary to create a convex bead as shown Torch and rod position for welding the corner joint ENBE 499 29*Figure copied from “TIG Handbook”
  30. 30. TIG Shielding Gases ► Argon ► Helium ► Argon/Helium Mixtures ENBE 499 30
  31. 31. TIG Shielding Gases Argon Helium► Good arc starting ► Faster travel speeds► Good cleaning action ► Increased penetration► Good arc stability ► Difficult arc starting► Focused arc cone ► Less cleaning action► Lower arc voltages ► Less low amp stability► 10-30 CFH flow rates ► Flared arc cone ► Higher arc voltages ► Higher flow rates (2x) ► Higher cost than argon ENBE 499 31
  32. 32. TIG Shielding GasesArgon/Helium Mixtures► Improved travel speeds over pure argon► Improved penetration over pure argon► Cleaning properties closer to pure argon► Improved arc starting over pure helium► Improved arc stability over pure helium► Arc cone shape more focused than pure helium► Arc voltages between pure argon and pure helium► Higher flow rates than pure argon► Costs higher than pure argon ENBE 499 32
  33. 33. Welding Parameters Aluminum weld parameters ENBE 499 33*Figure copied from “TIG Handbook”
  34. 34. Welding Parameters Aluminum with advanced squarewave weld parameters ENBE 499 34*Figure copied from “TIG Handbook”
  35. 35. Welding Parameters Stainless steel weld parameters ENBE 499 35*Figure copied from “TIG Handbook”
  36. 36. Welding Parameters Titanium weld parameters ENBE 499 36*Figure copied from “TIG Handbook”
  37. 37. Welding Parameters Mild steel weld parameters ENBE 499 37*Figure copied from “TIG Handbook”
  38. 38. Tungsten Electrode Selection Guide to selecting a tungsten electrode based on amperage range ENBE 499 38*Figure copied from “Guidelines to Gas Tungsten Arc Welding (GTAW)”
  39. 39. Conclusion► TIG welding is an exciting skill that proves itself useful in countless applications► Because it welds more metal and metal alloys than any other process, TIG welding should be regarded as an important tool where experience is the teacher► Welding parameters and tungsten electrode selection tables are recommended values and should be used as a guideline► Information presented here is only the tip of the iceberg, and further research and hands-on involvement should be pursued to be comprehensive ENBE 499 39
  40. 40. References► “Gas tungsten arc welding.” Wikipedia. 19 February 2008.► “Guidelines to Gas Tungsten Arc Welding (GTAW).” Miller Electric Mfg Co. July 2003.► “Installation and Operating Instructions for HELIARC 306 Welding Power Supply.” L-TEC Welding and Cutting Systems. January 1988.► “TIG Handbook.” Miller Electric Mfg Co. July 2003.► “TIG Welding.” American Metallurgical Consultants. 18 October 2007.► “TIG Welding Tips.” Miller Electric Mfg Co. 29 January 2008. ENBE 499 40