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Types of welding

Welding Do you fear in welding? Don’t worry, it is nothing. It is the process of inter molecular bonding of two similar or dissimilar metals by heating and brings its melting point temperature, in this condition the external pressure may or may not be used, or third metal viz filler rod may or may not be used. The heating is produced by electric arc, oxy-acetylene flame or oxy-hydrogen flame etc. where the metal’s end portion to be weld. The basic requirement of welding is i) heat energy, ii) cleaning the edge before the welding, iii) atmospheric contamination, iv) weld metal properties, v) application of pressure. Heat: During welding it should required sufficient amount of heat for fusion. Otherwise the joint may produced incomplete fusion. Cleaning: Cleaning the welding edges should be properly maintained. Because the unwanted materials are may be damaged the welding joints. The unwanted materials are- oxides, nitrides, oil, grease, dirt, sand etc. These should be properly cleaned by either mechanically or chemically. Atmospheric contamination: The main atmospheric contamination is nitrogen, oxygen and humidity. During welding flux, various inert gas or other types of gas should be used, which may helps to avoid the reaction with these contamination. Welding metal properties: It is very important for obtaining the cleanness weld joint. These processes are which can be controlled with successfully- i) de-oxidizers used during welding, ii) to mixing up the alloy in filler rod, iii) by the controlling of base metal composition, iv) by the post weld heat treatment. Application of pressure: In few welding process the sufficient amount of pressure is required for weld joint. This pressure may be obtained from mechanically, pneumatically or hydraulically. Advantages of welding: a) Similar or dissimilar metals can be joining. b) The joint can produce same or more strength than base metals. c) The welding machine portability is the good advantage for anywhere welding. d) The welding can easily performed in very big size like structure under budget. e) The welding is the only one process which can make joint the broken parts easily. f) It has extra facility that the joint can performed under water. Disadvantages of welding: a) Highly trained persons are required for good welding. b) Initially investment cost is very high. c) During welding the metallic structure of base metal may be changed for high temperature. d) Often heat treatment may require after welding process. e) In welding the edge preparation should required, so more than one man power is required. f) The welding equipments handling required with carefully. g) The welder should have sufficient knowledge about general electric. h) The very dangerous ultraviolet ray and fumes are produced, so safety should be taken properly. Classification of welding: There are different types of welding process are classified into two main groups. One is fusion and another is pressure welding. The fusion welding are sub-classified in gas welding, thermit welding, metal arc welding, carbon arc welding, atomic hydrogen welding, TIG welding, MIG welding. The pressure welding are forge welding, spot welding, seam welding, butt welding, flash welding. The general condition of welding: The welding joint will be easy if the weld joint portion is cleaned by wire brush or machining or sand blasting. By these processes the unwanted materials or impurity is cleaned properly. If these impurity presences in weld pull then it may be weakened the joint by inclusion. So the quality joint is cannot be made. The oxidation rate is directly proportional to temperature. Most welding process performed in high temperature and that time the oxidation acting as a weakening agent in weld metal. This is prevented by the using of fluxes and makes a strong weld joint. In manual welding process the flux is covered on the electrode. This flux is melted in high temperature and covered on the weld metal. Then it creates an artificial anti oxidation gaseous covered on weld metal. Powder type flux is used in gas and forged welding. In other welding process there are used non oxidation gaseous components like Argon, Helium etc. which covered on the weld metal and prevent the oxidation. Industrial application of welding: Today the welding process is very easy because the machines are much modernized. So the weld joint can be performed in any position. It has very much application in workshop to fabricate the small/big structure, repair and maintenance of various components. In fabrication work there various type angle, channel or beam is used to make a structure. There may be used the nut bolt to join together, but it is less strong than welding. The structure can be made by casting. But this process is very expensive. In other way the welding process is less expensive, labor cost and easy. Due to this causes the welding is very popular in fabrication industry.

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