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Manufacturing Processes Lab I, MET 1321 Gas Tungsten Arc Welding ( TIG )

Manufacturing Processes Lab I, MET 1321 Gas Tungsten Arc Welding ( TIG ). Welding Processes. Shielded Metal Arc Welding ( Stick welding ) Gas Metal Arc Welding ( MIG ) Gas Tungsten Arc Welding ( TIG ) Flux Cored Arc Welding Submerged Arc Welding Plasma Arc Welding. ARC Welding (AW).

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Manufacturing Processes Lab I, MET 1321 Gas Tungsten Arc Welding ( TIG )

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  1. Manufacturing Processes Lab I, MET 1321Gas TungstenArc Welding (TIG) Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  2. Welding Processes • Shielded Metal Arc Welding (Stick welding) • Gas Metal Arc Welding (MIG) • Gas Tungsten Arc Welding (TIG) • Flux Cored Arc Welding • Submerged Arc Welding • Plasma Arc Welding ARC Welding (AW) Oxyfuel Welding OFW Oxyacetylene Welding (OAW) Resistance Welding RW Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  3. Gas Tungsten Arc Welding (GTAW)Tungsten Inert Gas (TIG) GTAW or TIG is an arc welding process in which a shielding gas protects the arc between a non consumabletungsten electrod and the weld area. Gas is fed through the torch to shield the electrode and molten weld pool.  If filler wire is used, it is added to the weld pool separately.  Usage: Joining thin-wall tubing and depositing the root pass in pipe joints. GTAW Produces high quality weldment. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  4. TIG equipment • Equipment consists of the welding torch plus additional apparatus to supply electrical power, shielding gas, and a water inlet and outlet. • Personal protective equipment should be worn to protect the operator from the arc rays during welding operations. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  5. TIG equipment • TIG welding torch Argon regulator with flowmeter (1) Cap. Prevents the escape of gas from the top of the torch and locks the electrode in place. (2) Collet. Made of copper; the electrode fits inside and when the cap is tightened, it squeezes against the electrode and leeks it in place. (3) Gas orifice nut. Allows the gas to escape. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  6. Shielding Gas • In general, the shielding gas is Argon or its mixture with other gases. The gas is regulated by a flowmeter. • Summary of all gases used: • Argon •  Argon + Hydrogen •  Argon + Helium Helium is generally added to increase heat input (increase welding speed or weld penetration).  Hydrogen will result in cleaner looking welds and also increase heat input, however, Hydrogen may promote porosity or hydrogen cracking. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  7. Advantages • TIG welding benefits: • It can weld more types of metal and metal alloys than any other welding process.  • Superior quality welds •  Welds can be made with or without filler metal •  Precise control of welding variables (heat) • Free of slag and spatter • Low distortion Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  8. Current • The welding machine used for TIG can provide eitherAC or DC current. • The choice of using AC or DC current depends on the metal to be welded. • TIG requires precise current control, especially in the low range (to maintain a stable arc), particularly for welding light-gauge metals. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  9. Derating • A welding machine originally designed for use with SMAW (stick welding) must be de-rated to protect it from the effect of internal heating that occurs during GTAW. • Derating is a lowering of the current output level (or the duty cycle or both) of an AC welding machine. • Duty cycle is a welding equipment specification which defines the number of minutes, within a 10 minute period, during which a given welder can safely produce a particular welding current. • For example, a 150 amp. welder with a 30% duty cycle must be "rested" for at least 7 minutes after 3 minutes of continuous welding. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  10. The diameter of the electrode selected for a welding operation is determined by the required welding current. How to weld • Before starting to weld, ensure that the Tungsten electrode has the proper stickout beyond the end of the gas nozzle. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  11. How to weld • The type and amount of shielding gas used is determined by current, type of weld, base metal and welding conditions. • Gas nozzles that are too small for the welding task may overheat, crack, or deteriorate rapidly. • A water-cooled torch is recommended when using currents over 200A. Ensure cooling water is flowing before welding. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  12. How to weld • When welding light-gauging metals, a copper backing bar is usually required. • Filler metalcontainingdeoxidizers should be used when welding with GTAW to prevent porosity in the weld. • Medium and high-carbon steels require preheat and postheating to avoid loss of toughness and ductility. Ensure that there is good ventilation when welding copper or copper alloys. Fumes of these metals are highly toxic. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  13. Striking an arc • Set the welding current and hold the torch in a horizontal position about 2” above the workpiece. When using DC current, lower the torch until the electrode touches the workpiece. Once the arc is started, withdraw the electrode so it is about 1/8” above the workpiece. When using AC (ACHF or Alternating current high frequency), the electrode should not touch the workpiece to start the arc. Keep it 1/8” above the workpiece. Use this method for the DC welding machine with a high-frequency start up. • To stop the arc during welding, swing the electrode back to the horizontal position without touching the welding area. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  14. Striking an arc • Establish an arc. • Create a weld puddle. • Add filler metal "dip" into the puddle while pushing the weld puddle along the weld joint. • End the arc and leave the torch over the weld puddle to protect it until the puddle cools. • CleanCleaning both the weld joint area and the filler metal is an important preparation. Remove all oil, grease, dirt, paint, etc. The presence of these contaminants may result in arc instability or contaminated welds. • ClampClamping may be required if the work piece cannot be supported during welding. • Tack weldMake short 1/4 in. tack welds along the work pieces to hold them together. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  15. How do I position my TIG torch for different types of joints? Work angle Push angle Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  16. How do I position my TIG torch for different types of joints? Work angle Push angle Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  17. non-consumable DC (DCEN) Test yourself! • GTAW or TIG is an arc welding process in which a shielding gas protects the arc between a consumable tungsten electrod and the weld area. • True • False • In TIG welding, the main shielding gas is Argon. • True • False • The TIG current used for welding the most ferrous metals(Steel, Thick Stainless Steel, Cast Iron),is AC. • True • False Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  18. Test yourself • Derating (lowering of the current output level or the duty cycle of an AC welding machine) is done • to increase the minutes during which a given welder can safely produce a particular welding current. • to protect the machine from the effect of internal heating that occurs during GTAW. • to have a high-frequency start up in welding. Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

  19. Test yourself • Filler metal containing deoxidizers should be used when welding with GTAW to prevent …… in the weld. • contaminations • porosity • instability Manufacturing Processes Lab 1 (MET 1321) Prof S. Nasseri

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