1. Fusion-Welding Processes
CHAPTER 7-1

2. General Characteristics of Fusion Welding Processes

3. Oxyacetylene Flames Used in Welding
Figure 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. Torch Used in Oxyacetylene Welding
Figure (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. Shielded Metal-Arc Welding
Figure Schematic illustration of the shielded metal-arc welding process. About 50% of all large-scale industrial welding operations use this process.
Figure 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. Multiple Pass Deep Weld
Figure A deep weld showing the buildup sequence of individual weld beads.

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

8. Gas Metal-Arc Welding
Figure Schematic illustration of the gas metal-arc welding process, formerly known as MIG (for metal inert gas) welding.

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

10. Flux-Cored Arc-Welding
Figure Schematic illustration of the flux-cored arc-welding process. This operation is similar to gas metal-arc welding, showing in Fig

11. Equipment for Electroslag Welding
Figure Equipment used for electroslag welding operations. Source: American Welding Society.

12. Designations for Mild Steel Coated Electrodes

13. Gas Tungsten-Arc Welding
Figure The gas tungsten-arc welding process, formerly known as TIG (for tungsten inert gas) welding.
Figure Equipment for gas tungsten-arc welding operations. Source: American Welding Society.

14. Plasma-Arc Welding
Figure 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. Comparison of Laser-Beam and Tungsten-Arc Welding
Figure 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. Example of Laser Welding
Figure Laser welding of razor blades.

17. Flame Cutting and Drag Lines
Figure (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. Summary metal-arc welding Shielded metal-arc weldingB
Electrode
Molten metal A B
Electrode
Extruded coating flux
Molten metal
Gas shielding A B
Electrode
Molten metal
Granulated
Powder
metal-arc welding
Shielded metal-arc welding
Submerged arc welding A B
Consumable Electrode
(filler)
Molten metal
Inert gas
Filler A B
Oxygen gas
Acetylene gas
Gas flow control taps
Inner cone
Outer envelope
Fig 6.3 Gas welding using Oxyacetylene torch.
TIG A B
Non-consumable Electrode
Filler wire
Inert gas
TIG

19. (b) Welding applications.
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)
(b)
(a)
(a) Welding joints
(b) Welding applications.

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