tig welding introduction

1. TIG Welding Introduction by Daniel Min

2. ENBE 499 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

3. ENBE 499 3 Background What is TIG? Tungsten Inert Gas Also referred to as GTAW Gas Shielded Tungsten Welding In TIG welding, a tungsten electrode heats the metal you are welding and gas (most typically Argon) protects the weld from airborne contaminants

4. ENBE 499 4 Background TIG welding uses a non-consumable tungsten Filler metal, when required, is added by hand Shielding gas protects the weld and tungsten

5. ENBE 499 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

6. ENBE 499 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

7. ENBE 499 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

8. ENBE 499 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

9. ENBE 499 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

10. ENBE 499 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

11. ENBE 499 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

12. ENBE 499 12 Control 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 Preparation for TIG Welding

13. ENBE 499 13 Control 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 Preparation for TIG Welding

14. ENBE 499 14 Preparing 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 Preparation for TIG Welding

15. ENBE 499 15 Cleaning 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 Preparation for TIG Welding

16. ENBE 499 16 Preparing 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 Preparation for TIG Welding

17. ENBE 499 17 Preparing 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 Preparation for TIG Welding

18. ENBE 499 18 Preparing 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 Preparation for TIG Welding

19. ENBE 499 19 Preparing Mild Steel for Welding Should be mechanically cleaned Scale, rust, paint, oil, grease, or any surface contaminants should be removed Preparation for TIG Welding

20. ENBE 499 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

21. ENBE 499 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

22. ENBE 499 22 Techniques for Basic Weld Joints Electrode 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

23. ENBE 499 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

24. ENBE 499 24 Techniques for Basic Weld Joints Manual Torch Movement

25. ENBE 499 25 Techniques for Basic Weld Joints Manual 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

26. ENBE 499 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

27. ENBE 499 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

28. ENBE 499 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

29. ENBE 499 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

30. ENBE 499 30 TIG Shielding Gases Argon Helium Argon/Helium Mixtures

31. ENBE 499 31 TIG Shielding Gases Argon Good arc starting Good cleaning action Good arc stability Focused arc cone Lower arc voltages 10-30 CFH flow rates Helium Faster travel speeds Increased penetration Difficult arc starting Less cleaning action Less low amp stability Flared arc cone Higher arc voltages Higher flow rates (2x) Higher cost than argon

32. ENBE 499 32 TIG Shielding Gases Argon/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

33. ENBE 499 33 Welding Parameters

34. ENBE 499 34 Welding Parameters

35. ENBE 499 35 Welding Parameters

36. ENBE 499 36 Welding Parameters

37. ENBE 499 37 Welding Parameters

38. ENBE 499 38 Tungsten Electrode Selection

39. ENBE 499 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

40. ENBE 499 40 References “Gas tungsten arc welding.” Wikipedia. http://en.wikipedia.org/wiki/Gas_tungsten_arc_welding. 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. http://www.weldingengineer.com/1tig.htm. 18 October 2007. “TIG Welding Tips.” Miller Electric Mfg Co. http://www.millerwelds.com/education/tech_tips/TIG_tips. 29 January 2008.