1. Page 27-1 Fusion-Welding Processes CHAPTER 7-1

2. Page 27-2 General Characteristics of Fusion Welding Processes

3. Page 27-3 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.

4. Page 27-4 Torch Used in Oxyacetylene 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.

5. Page 27-5 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. Figure 27.5 Schematic illustration of the shielded metal-arc welding operations (also known as stick welding, because the electrode is in the shape of a stick).

6. Page 27-6 Multiple Pass Deep Weld Figure 27.6 A deep weld showing the buildup sequence of individual weld beads.

7. Page 27-7 Submerged-Arc Welding Figure 27.7 Schematic illustration of the submerged-arc welding process and equipment. The unfused flux is recovered and reused. Source: American Welding Society.

8. Page 27-8 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.

9. Page 27-9 Equipment Used in Gas Metal-Arc Welding Figure 27.9 Basic equipment used in gas metal-arc welding operations. Source: American Welding Society.

10. Page 27-10 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.

11. Page 27-11 Equipment for Electroslag Welding Figure 27.12 Equipment used for electroslag welding operations. Source: American Welding Society.

12. Page 27-12 Designations for Mild Steel Coated Electrodes

13. Page 27-13 Gas Tungsten-Arc Welding 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.

14. Page 27-14 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.

15. Page 27-15 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.

16. Page 27-16 Example of Laser Welding Figure 27.17 Laser welding of razor blades.

17. Page 27-17 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.

18. Page 27-18 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 Fig 6.3 Gas welding using Oxyacetylene torch.

19. Page 27-19 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) (b) (a) Welding joints(b) Welding applications.

20. Page 27-20 Where, K: constant less than 1 related to heat losses. I : Current. R: Resistance of ionized air gap. t : Welding time.