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Many engineered products use welding as one of the fabrication methods to fasten parts permanently. Structures such as bridges and buildings have welded steel components. Parts for mechanical devices, such as automobiles and aircraft, are also fabricated using welding. In technical drawings, the welding of parts must be specified by standard ANSI and American Welding Society (AWS) symbols. This chapter describes the different welding processes, the various types of welded joints, and the symbols used to specify welded joints on technical drawings.
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OVERVIEW |
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| 25.1 Welding drawings are a specialized type of technical drawing which differs from many other types of drawings in that its main focus is to specify how parts are joined together. Since welds are both permanent and structural, proper location and orientation of the welded members and the type of weld used are important to properly specify. As with other types of specialized technical drawings, there is a specific symbology used to represent the welding process. |
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WELDING PROCESSES |
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| 25.2 Welding is a process by which material is jointed by bringing two abutting surfaces together in a molten state. This can be done under many different situations: by humans or robots, under tightly controlled conditions in a factory, or in the field. Welding processes tend to fall into two general categories: liquid state solid state The most common welding processes are: Arc Gas Resistance |
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WELDED JOINT TYPES |
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| 25.3 There are five basic types of weld joints: Butt Lap Tee Corner Edge Looking at Figure 25.7, note the difference in the orientation of the pieces to each other and the relative difference in the amount of metal contact. Though the illustration shows flat metal stock, the pieces could be other geometries. |
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WELD SYMBOLS |
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| 25.4 The AWS/ANSI weld symbol standard has eight basic parts: Reference line Leader line and arrow Basic weld symbol (location and depth of weld) Finish symbol Weld symbol (type of weld) Dimensions Supplementary symbols Tail and specifications As with geometric dimensioning and tolerancing (Chapter 16), a common set of symbols, a framework, and alphanumeric notation are used to specify the manufacture of the product. |
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WELD TYPES |
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| 25.5 Weld types are categorized by the weld shape and the type of groove to be filled with weld material. Common types of welds include: Fillet. Located at the interior corner of two parts. Groove. Grouped by their characteristic appearance: Plug or slot. The metal is overlapped and the pieces are joined by welding through and filling hole in one of the pieces. Spot. A type of resistance welding generally used on sheet metal. Seam. A line or seam welded between overlapping parts. Surface. A surface treatment done on a single piece. |
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| 25.6 If the weld is not continuous, the weld length must be specified. The distance between the centers of weld segments is called the pitch distance. |
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| 25.7-8 One of the most time consuming aspects of welding drawings is creating the symbols. For that reason templates are used extensively for hand drawings and symbol libraries with CAD generated drawings. As with other specialized technical drawing areas, third party software is available for creating welding drawings. |
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SUMMARY |
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Welding drawings are a special type of technical drawing that describes how parts are fabricated. A welding drawing uses standard graphic symbols to describe to the welder how to join two materials. Weld symbols conform to ANSI standards and are summarized in Figures 25.29 and 25.30. Weld symbols are drawn with hand tools, a template, or CAD. If CAD is used, a symbol library is created or one is purchased through a third-party software company. |