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Fusion welding. Submitted to: By Sri. M.P.Gururajan Srihari prasad Gorti 2008AMD2919. FUSION Welding. What is fusion welding . Fusion welding is a secondary manufacturing process.
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Fusion welding Submitted to: By Sri. M.P.Gururajan Srihari prasad Gorti 2008AMD2919
FUSION Welding What is fusion welding. Fusion welding is a secondary manufacturing process. Repair works also possible.
Fusion welding Gas welding Arc welding High energy beam welding Oxy-acetylene welding Shielding metal arc welding(SMAW) Electron beam welding(EBW) (OAW) Gas-tungsten arc welding(GTAW) Plasma arc welding (PAW) Laser beam welding(LBW) Gas-metal arc welding(GMAW) Flux-cored arc welding(FAW) Submerged arc welding(SAW) Electroslag welding (ESW)
Fusionweldingmechanism • Solidification of crystalline materials • formation of a liquid pool • interface between liquid and solid • Solidification • Micro-structure casting in a mould,
Gas welding • Heat is generated in the gas welding by chemical reactions • Stage 1 • C2H2+O2 2 CO+H2+448 KJ/Mol (18.75 MJ/m3of acetylene) • Stage 2: • 4CO+2H2+3O2 CO2+2H2O+812 KJ/mol (35.77 MJ/ m3)
NEUTRAL FLAME • Equal amounts of oxygen • Does not alter the composition, best for most metals. • Temperature is approximately 3232°C.
CARBURIZING FLAME • Burning an excess of acetylene, • Three distinct colors.
Oxidizing FLAME • Burning an excess of oxygen. • Appearance is similar to the neutral flame, but the inner cone is shorter, slightly pointed, and has a purplish tinge. • This flame burns with a hissing sound. • For ferrous metals Numerous sparks Foam that forms on the surface.
Arc welding Principle of arc welding • Arc is generated between two conductors of electricity. Heat is liberated by • Electrons • Charged ions • The positively charged ions, 65 to 75 % of heat at the anode
Arc Shielding • Metals are reactive at high temperatures • Formation oxides and nitrides are formed. • Protective shield of gas, vapor, or slag (arc shielding)
Nature of arc • Arc functions in welding • To melt the metal • To transport the molten metal from the tip of the electrode to the work. • Surface Tension Transfer • Metal Spray Arc • Globular transfer
In Direct current there will be two types depending upon the direction of flow of current. • Direct current electrode negative (DCEN): • Electrode is cathode. • 2/3rd of heat is at anode. • Non-consumable electrode welding processes. Arc welding may be done with • Direct current (DC) • Alternating current (AC). • Direct current electrode positive (DCEP): • Electrode is anode. • consumable electrode welding processes.
Applicability of process S:sheet up to 3 mm; I: intermediate, 3-6 mm; M: medium, 6-19 mm; T: thick, 19 mm and up; X: recommended
Effects on welding • The weldability of steels is inversely proportional to a property known as the hardenability of the steel. As the hardness of the steel is high there may be possibility of hot cracking. • For the aluminum alloys proper shielding has to be provided otherwise the metal gets oxidized. • Excessive heat supply leads to distortion of welded parts.
Advantages of welding: • Strong and tight joining • Cost effectiveness • Simplicity of welded structures design • Welding processes may be automated. • Applications of welding: • Buildings and bridges structures • Automotive, ship and aircraft constructions • Pipe lines • Tanks and vessels • Railroads • Machinery elements. Disadvantages of welding: • Internal stresses, distortions and changes of micro-structure in the weld region • Harmful effects: light, ultra violate radiation, fumes, high temperature.
