Fusion welds

The aim of this work which enter in a research project on NDT, is to conceive a system of aid for interpretation and taking decisions, on imperfections in metallic fusion welds, we have studied and tested several segmentation techniques based on the two approaches ( contour and regions ). A quantitative analysis will be applied to extract some relatives geometricals parameters. To the sight of these characteristics, a first classification will be possible. 

Pig. 10. Double-v inlay, batten-strap technique for fusion welding of an explosion-clad plate containing titanium and zirconium. 

In many cases, the deposited material can retain some of the original chemical constituents, such as hydrogen in siUcon from the deposition from silane, or chlorine in tungsten from the deposition from WCl. This can be beneficial or detrimental. For example, the retention of hydrogen in siUcon allows the deposition of amorphous siUcon, a-Si H, which is used in solar cells, but the retention of chlorine in tungsten is detrimental to subsequent fusion welding of the tungsten. 

Welding (qv) of titanium requires a protected atmosphere of iaert gas. Furthermore, parts and filler wire are cleaned with acetone (trichloroethylene is not recommended). The pieces to be welded are clamped, not tacked, unless tacks are shielded with iaert gas. A test sample should be welded. Coated electrodes are excluded and higher purity metal (lower oxygen content) is preferred as filler. Titanium caimot be fusion-welded to other metals because of formation of brittle intermetallic phases ia the weld 2oae. 

X-ray imaging tests are widely used to examine interior regions of metal castings, fusion welds, composite stmctures, and brazed components. 

Y = coefficient naving value in Table 10-50 for ductile ferrous materials, 0.4 for ductile nonferrous materials, and zero for brittle materials such as cast iron t,n = minimum required thickness, in, to which manufacturing tolerance must be added when specifying pipe thickness on purchase orders. [Most ASTM specifications to which mill pipe is normally obtained permit minimum wall to be 12V percent less than nominal. ASTM A155 for fusion-welded pipe permits minimum wall 0.25 mm (0.01 in) less than nominal plate thickness.] Pipe with t equal to or greater than D/6 or P/SE greater than 0.385 reqmres special consideration. 

X ilues of C relating to material compatibility for selected fusion welding processes (3)... 

Table 3.7. Rods and Electrodes for Fusion-Welding Cast Iron...

Rods and electrodes for fusion-welding cast iron. 61... 

Sizes and thicknes.ses to which no Standard designation applies are largely the more commonly used dimensions to which Taylor B orge Electric Fusion Welded Pipe is produced for a wide variety of applications including river crossings, penstocks, power plant and other piping. 

Part 2 Specification for automotive LPG BS 5500 Unfired fusion welded pressure vessels BS 7122 Welded steel tanks for the road transport of liquefiable gases... 

Fig. 1.9(a) Curves showing the variation of temperature with time at various points adjacent to a fusion weld in an austenitic stainless steel and (b) weld decay in an unstabilised austenitic... 

Cold forming Machining Fusion welding Inert gas xy gos arc Resistance spot welding Protective anodising... 

Fusion welding operations are rather more difficult with brasses than with other copper alloys (because of evolution of zinc fume from brasses). 

Mechanical fasteners Soldering and brazing Fusion welding... 

Fig. 9.26 Weld definitions, (a) Fusion weld and (b) resistance spot weld...

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