1. 材料科学与工程学院 College of Materials Science & Engineering Page 1 Page 1 Fundamental of Materials Forming -Fusion Welding

2. 材料科学与工程学院 College of Materials Science & Engineering Page 2 Page 2 Fusion-Welding Processes

3. 材料科学与工程学院 College of Materials Science & Engineering Page 3 Page 3 General Characteristics of Fusion Welding Processes

4. 材料科学与工程学院 College of Materials Science & Engineering Page 4 Page 4 Oxyacetylene Flames Used in Welding Figure 27.1 Three basic types of oxyacetylene flames used in oxyfuel-gas welding and cutting operations: (a) neutral flame; (b) oxidizing flame; (c) carburizing, or reducing, flame. The gas mixture in (a) is basically equal volumes of oxygen and acetylene.

5. 材料科学与工程学院 College of Materials Science & Engineering Page 5 Page 5 Torch Used in Oxy acetylene Welding Figure 27.2 (a) General view of and (b) cross-section of a torch used in oxyacetylene welding. The acetylene valve is opened first; the gas is lit with a spark lighter or a pilot light; then the oxygen valve is opened and the flame adjusted. (c) Basic equipment used in oxyfuel-gas welding. To ensure correct connections, all threads on acetylene fittings are left-handed, whereas those for oxygen are right-handed. Oxygen regulators are usually painted green, acetylene regulators red.

6. 材料科学与工程学院 College of Materials Science & Engineering Page 6 Page 6 Shielded Metal-Arc Welding Figure 27.4 Schematic illustration of the shielded metal-arc welding process. About 50% of all large-scale industrial welding operations use this process.

7. 材料科学与工程学院 College of Materials Science & Engineering Page 7 Page 7

8. 材料科学与工程学院 College of Materials Science & Engineering Page 8 Page 8

9. 材料科学与工程学院 College of Materials Science & Engineering Page 9 Page 9 Multiple Pass Deep Weld Figure 27.6 A deep weld showing the buildup sequence of individual weld beads.

10. 材料科学与工程学院 College of Materials Science & Engineering Page 10 Page 10 Submerged-Arc Weldin g Figure 27.7 Schematic illustration of the submerged-arc welding process and equipment. The unfused flux is recovered and reused. Source: American Welding Society.

11. 材料科学与工程学院 College of Materials Science & Engineering Page 11 Page 11 Functions of Flux: -- as a shielding protection -- helps form the slag on the weld -- as thermal insulator (getting deeper welding )

12. 材料科学与工程学院 College of Materials Science & Engineering Page 12 Page 12 Gas Metal-Arc Welding Figure 27.8 Schematic illustration of the gas metal-arc welding process, formerly known as MIG (for metal inert gas) welding.

13. 材料科学与工程学院 College of Materials Science & Engineering Page 13 Page 13 Gas Tungsten-Arc Weldin g Figure 27.13 The gas tungsten-arc welding process, formerly known as TIG (for tungsten inert gas) welding.

14. 材料科学与工程学院 College of Materials Science & Engineering Page 14 Page 14

15. 材料科学与工程学院 College of Materials Science & Engineering Page 15 Page 15 GTAW: No flux but inert gas Constant gap  high quality Electrode needs to be cooled Heavy welding gun  skilled/mechanized operation

16. 材料科学与工程学院 College of Materials Science & Engineering Page 16 Page 16 Comparison of Laser-Beam and Tungsten-Arc Welding Figure 27.16 Comparison of the size of weld beads in (a) electron-beam or laser-beam welding to that in (b) conventional (tungsten-arc) welding. Source: American Welding Society, Welding Handbook (8th ed.), 1991.

17. 材料科学与工程学院 College of Materials Science & Engineering Page 17 Page 17 Comparison of Conventional and Laser-Beam Welding Figure 28.14 The relative sizes of the weld beads obtained by conventional (tungsten arc) and by electron-beam or laser-beam welding.

18. 材料科学与工程学院 College of Materials Science & Engineering Page 18 Page 18 LASER Welding (high-energy beam): High aspect (depth-to-width) ratio 4-10 High quality Small distortion

19. 材料科学与工程学院 College of Materials Science & Engineering Page 19 Page 19 Example of Laser Welding Figure Laser welding of razor blades.

20. 材料科学与工程学院 College of Materials Science & Engineering Page 20 Page 20 Equipment Used in Gas Metal-Arc Welding Figure 27.9 Basic equipment used in gas metal-arc welding operations. Source: American Welding Society.

21. 材料科学与工程学院 College of Materials Science & Engineering Page 21 Page 21 Flux-Cored Arc-Welding Figure 27.10 Schematic illustration of the flux-cored arc-welding process. This operation is similar to gas metal-arc welding, showing in Fig. 27.8.

22. 材料科学与工程学院 College of Materials Science & Engineering Page 22 Page 22 Equipment for Electroslag Welding Figure 27.12 Equipment used for electroslag welding operations. Source: American Welding Society.

23. 材料科学与工程学院 College of Materials Science & Engineering Page 23 Page 23 Designations for Mild Steel Coated Electrodes

24. 材料科学与工程学院 College of Materials Science & Engineering Page 24 Page 24 Gas Tungsten-Arc Weldi ng Figure 27.13 The gas tungsten-arc welding process, formerly known as TIG (for tungsten inert gas) welding. Figure 27.14 Equipment for gas tungsten-arc welding operations. Source: American Welding Society.

25. 材料科学与工程学院 College of Materials Science & Engineering Page 25 Page 25 Plasma-Arc Welding Figure 27.15 Two types of plasma-arc welding processes: (a) transferred, (b) nontransferred. Deep and narrow welds can be made by this process at high welding speeds.

26. 材料科学与工程学院 College of Materials Science & Engineering Page 26 Page 26 Weld Design Selection Figure 29.17

27. 材料科学与工程学院 College of Materials Science & Engineering Page 27 Page 27 Flame Cutting and Drag Lines Figure 27.18 (a) Flame cutting of steel plate with an oxyacetylene torch, and a cross-section of the torch nozzle. (b) Cross-section of a flame-cut plate showing drag lines.

28. 材料科学与工程学院 College of Materials Science & Engineering Page 28 Page 28 Summary A B Electrode Molten metal A B Electrode Extruded coating flux Molten metal Gas shielding A B Electrode Molten metal Granulated Powder A B Consumable Electrode (filler) Molten metal Inert gas A B Non-consumable Electrode Filler wire Inert gas TIG Submerged arc weldingShielded metal-arc weldingmetal-arc welding Filler A B Oxygen gas Acetylene gas Gas flow control taps Inner cone Outer envelope Gas welding using Oxyacetylene torch.

29. 材料科学与工程学院 College of Materials Science & Engineering Page 29 Page 29 Simple butt joint Simple butt joint (Thick plate) Single “V” joint Single “V” joint (thick plate 4-30mm) Double “V” joint Double “V” joint (thick plate 20-25mm) Single “U” joint Single “J” joint (thick plate >25mm) (a) Welding joints(b) Welding applications.

30. 材料科学与工程学院 College of Materials Science & Engineering Page 30 Page 30 Where, K: constant less than 1 related to heat losses. I : Current. R: Resistance of ionized air gap. t : Welding time.