Chapter 15 Assignment - Welding Course

1. What are the two other names used for GTA welding? TIG & Heliarc 2. What are two advantages of GTA welding? It can be used to produce very high-quality welds and it can be used to weld on almost any metal. 3. List four major components that make up a GTA welding station. Welding power supply, welding torch, work clamp, and shielding gas cylinder. 4. List three advantages that using an air-cooled GTAW torch might have over using a water-cooled GTAW torch. Lighter weight for the same amperage range, easier to manipulate without the water hoses, easier to maintain. 5. List three advantages that using a water-cooled GTAW torch might have over using an air-cooled GTAW torch. Continuous operation without overheating, lower torch temperatures means less tungsten erosion, less torch handle temperature in the welders hands. 6. List the hoses and cables that might be attached to a water-cooled torch. Water inlet hose, Water outlet hose, Welding power cable, and shielding gas hose. 7. What type of antifreeze solution may be used in a water-cooling system? A low conductive antifreeze solution may be added to the water to prevent freezing and corrosion. 8. What is the purpose of the shielding gas nozzle? The nozzle or cup is used to direct the shielding gas directly on the welding zone. 9. Why is tungsten used as an electrode? It has a high melting temperature and good electrical conductivity. 10. List five ways to limit tungsten erosion. Use as low a ewelding current as possible, use a water cooled torch, use a direct current electrode negative (DCEN) current. 11. What are the AWS classifications for the following types of tungsten electrodes? ● Pure tungsten (EWP) ● 1% thorium tungsten (EWTh-1) ● 2% thorium tungsten (EWTh-2) ● ¼ to ½% zirconium tungsten (EWZr) ● 2% cerium tungsten (EWCe-2) ● 1% lanthanum tungsten (EWLa-1) 12. Which type of tungsten electrode has the poorest heat resistance and emission characteristics? Pure Tungsten 13. Which type of tungsten electrode has a very low level radioactive oxide additive? Thoriated Tungsten. 14. According to Table 15-2, what color tip does the EWCe-2 tungsten electrode have? Orange 15. What is La2O3? Lanthanum Oxide 16. What are the units of shielding gas flow? Cubic Feet per Hour (CFH) 17. How high should the shielding gas flow rate be? The rate of flow should be as low as possible and still give adequate coverage. 18. What is preflow time used for? Gas flows to clear out any air in the nozzle or surrounding the weld zone. 19. How is argon produced? Air is cooled to temperatures that cause it to liquefy; then its constituents are fractionally distilled. 20. What is the advantage of using helium as a shielding gas? Deeper penetration for shielding welds. 21. Nitrogen cannot be used as a shielding gas for GTA welding for what types of materials? Ferritic steels 22. What do the following abbreviations mean? DCEN, DCEP, and ACHF. Direct Current Electrode Negative, Direct Current Electrode Positive, and Alternating Current High Frequency. 23. What part of the AC cycle provides surface oxide cleaning? DCEP 24. What does a hot start provide to the GTA weld? It allows a controlled surge of welding current as the arc is started to establish a molten weld pool quickly. 25. What are the functions of a remote control? It can be used to start the weld, increase or decrease the current, and stop the weld. 26. List the ways of shaping the end of a tungsten electrode. Shaping the end of a tungsten can be achieved by grinding, breaking, remelting the end, or using chemical compounds. 27. When the end of a tungsten electrode is broken off to remove contamination, how should the broken end look? It should be square and relatively smooth. 28. How does a chemical cleaner remove tungsten contamination? It dissolves the contaminated tungsten. 29. Why must the power be off when you attach the GTA welding torch to a welding machine? An electrical shock or arc can occur 30. What is the maximum distance that the tungsten electrode should stick out of the nozzle? No more than the diameter of the nozzle