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==== ==== Acerca de los distintos tipos de soldadura: ==== ==== GAS WELDING In gas welding, gas flame is used for heating and melting the joining surfaces and the filler rod. Gas welding is done by burning a combustible gas with air or oxygen in a concentrated flame of high temperature. Most important combustible gas which gives highest temperature is acetylene. Hydrogen is also used in gas welding of low melting point metals such as aluminum. Temperature oxyacetylene flame is about 3200 C and is sufficient to weld the steel. Acetylene is a compound of carbon and hydrogen (C2H2) containing 92.3% carbon and 7.7% hydrogen by weight. It is a colorless and has a sweet and distinguished odour. Whereas oxygen is a colorless, odorless and tasteless gas. Use of pure oxygen speeds up reactions and increases flame temperature. The reaction of oxygen with organic substances produce large, quantities of heat. ARC WELDING Arc welding is widely used method of joining metal parts. In this, source of heat is an electric arc. An arc is produced between an anode (positive pole of direct current power supply) and the cathode (negative pole). Arc welding is done by producing an arc between the work to be welded and the tip of the electrode. This type of welding has the advantages of(i) less heat loss and(ii)less oxidation as compared to oxyacetylene flame. An electric arc is an electric discharge in gases, accompanied by high heat and a bright glow. When two conductors of an electric current are brought together make electrical contact, and then separated, an electric arc is formed. A considerable resistance to the flow of the current is thus introduced, the electrode tips are raised to high temperature due to air gap between them. The electrons which emerge from the negative electrode collide with the molecules and atoms of air, break them up into ions and free electrons and cause the air gap to become a conductor of electricity due to ionization. This maintains the current through the air gap and sustains the arc. Welding is a process of joining similar metals by the application of heat with or without application of pressure and addition of filler material. Welded joints between two parts produces continuous and homogeneous material. Each metal has different weld ability. The term weld ability means the capacity of being welded into inseparable joints. Good weld ability for a metal means, it can be welded readily so as to perform its object satisfactorily.

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