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Tham khảo tài liệu 'lesson 9-welding', ngoại ngữ, anh văn thương mại phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Lesson 9-Welding Fabrication and welding for hull are two primary workmanship in shipbuilding and so the quality working efficiency and cost of shipbuilding directly rely on them. So far fabrication has been dwelled upon in Workmanship for Hull Building. Therefore this short passage will simply deal with the welding procedure. First of all we shall come to the definition of welding. Broadly speaking welding implies that two pieces of basic metal are melted by heat and joined to each other. The sources of heat may originate from laser acetylene electrical arc etc. But here we are going to confine ourselves to the electrical arc. In the nature the phenomena of electricity shedding may be observed every now and then for instance lightning before a heavy shower in the summer time. Similar to a lightning an electrical arc used for welding is also a process of electricity shedding and as blazing as a lightning but it is controllable. In short the main heat source for the shipbuilding welding comes from an electrical arc. Now let s go into the details of different welding procedures. 1. Hand Electrical Arc Welding As mentioned above gas cutting is fit for material cutting during fabrication while gas welding is appropriate to the welding of sheet plates ventilating pipes cast iron pieces and non-ferrous metals. With regard to hand electrical arc welding with an electrode adopted it is mainly suitable for hull welding and you can apply it at any position. In order to gain a high working efficiency of welding hand electrical arc welding has been minimized to some forty percent portion of the total welding and is being replaced by new welding procedures in our shipyards since it is of low efficiency. 2. Automatic Submerged Arc Welding SAW SAW is a also common arc welding process. It requires a continuously fed consumable solid or tubular metal cored electrode. The molten weld and the arc zone are protected from atmospheric contamination by being submerged under a blanket of
