TIG Welding Introduction by Daniel Min

ENBE 4992 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 4993 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

ENBE 4994 Background ► TIG welding uses a non-consumable tungsten ► Filler metal, when required, is added by hand ► Shielding gas protects the weld and tungsten

ENBE 4995 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 4996 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 4997 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 4998 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 4999 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 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 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 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

ENBE 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

ENBE 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

ENBE 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

ENBE 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

ENBE 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

ENBE 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

ENBE 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

ENBE 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 *Figure copied from “TIG Handbook”

ENBE 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, 5-Gas cup, 6-Tungsten electrode *Figure copied from “TIG Handbook”

ENBE 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

ENBE 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 *Figure copied from “TIG Handbook”

ENBE Techniques for Basic Weld Joints Manual Torch Movement *Figure copied from “TIG Handbook”

ENBE 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

ENBE 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 bead *Figure copied from “TIG Handbook”

ENBE 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 *Figure copied from “TIG Handbook”

ENBE 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 *Figure copied from “TIG Handbook”

ENBE 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 *Figure copied from “TIG Handbook”

ENBE TIG Shielding Gases ► Argon ► Helium ► Argon/Helium Mixtures

ENBE TIG Shielding Gases Argon ► Good arc starting ► Good cleaning action ► Good arc stability ► Focused arc cone ► Lower arc voltages ► 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

ENBE 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

ENBE Welding Parameters Aluminum weld parameters *Figure copied from “TIG Handbook”

ENBE Welding Parameters Aluminum with advanced squarewave weld parameters *Figure copied from “TIG Handbook”

ENBE Welding Parameters Stainless steel weld parameters *Figure copied from “TIG Handbook”

ENBE Welding Parameters Titanium weld parameters *Figure copied from “TIG Handbook”

ENBE Welding Parameters Mild steel weld parameters *Figure copied from “TIG Handbook”

ENBE Tungsten Electrode Selection Guide to selecting a tungsten electrode based on amperage range *Figure copied from “Guidelines to Gas Tungsten Arc Welding (GTAW)”

ENBE Conclusion ►T►T►T►TIG welding is an exciting skill that proves itself useful in countless applications ►B►B►B►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 ►W►W►W►Welding parameters and tungsten electrode selection tables are recommended values and should be used as a guideline ►I►I►I►Information presented here is only the tip of the iceberg, and further research and hands-on involvement should be pursued to be comprehensive

ENBE References ► “Gas tungsten arc welding.” Wikipedia February ► “Guidelines to Gas Tungsten Arc Welding (GTAW).” Miller Electric Mfg Co. July ► “Installation and Operating Instructions for HELIARC 306 Welding Power Supply.” L-TEC Welding and Cutting Systems. January ► “TIG Handbook.” Miller Electric Mfg Co. July ► “TIG Welding.” American Metallurgical Consultants October ► “TIG Welding Tips.” Miller Electric Mfg Co January 2008.