Welds welding techniques

Aluminum and Alloys Aluminum and its alloys are made in practically all the forms in which metals are produced, including castings. Thermal conductivity of aluminum is 60 percent of that of pure copper, and unalloyed aluminum is used in many heat-transfer applications. Its high electrical conductivity makes aluminum popular in electrical apphcations. Aluminum is one of the most workable of metals, and it is usually joined by inert-gas-shielded arc-welding techniques. 

Eiimination. The welding technique must he such that the melting points of the metals to be joined are reached and maintained until a... 

Locations. Slag inclusions are principally a result of improper welding techniques and therefore may he found wherever welds are present. 

Elimination. The sensitization that leads to weld decay is a reversible process, and elimination can be achieved by appropriate heat treatment of the affected metal. Weld decay may also be avoided by specifying proper materials and welding techniques. 

Residual stresses caused by large temperature differences between the weld bead and adjacent metal can be reduced by preheating the metals to be welded, especially if the sections are thick, or by stress-relief-annealing following the welding procedure. Proper welding techniques, especially the use of appropriate weld filler metals to minimize weld-metal shrinkage, can minimize residual stresses. 

Specify appropriate welding techniques for stainless steels that may form more than one phase in the weldment (note Case History 15.1). 

Dispersion-strengthened lead (DSL), obtained by a uniform dispersion of lead oxide through the lead particle matrix, has the traditional corrosion resistance of lead but much greater stiffness. DSL is fabrieated as pipe and other extruded items, but has a limited applieation for proeess plant construction because the welding technique does not provide adequate strengths in joints. 

Figure 10-158B. Platecoil double- and single-embossing designs for standard units. The Platecoil is fabricated using resistance, spot, seam, and Tungsten Inert Gas (TIG) and/or Metal Inert Gas (MIG) welding techniques in order to hold and seal the two plates together. (Used by permission Cat. 5-63, 1994. Tranter , Inc.)...

Experience has proven that pulsation drums/bottles/ dampeners must be designed and fabricated using exceptionally heavy construction and good welding techniques and that the addition of support gusset plates to reinforce nozzles and other attachments is essential. 

Fabrication and welding techniques to be used. In connection with welding it should be emphasised that the correct grade of steel and electrode or filler rod must be used. 

Table 8-42 Percent tensile strength retention using welding techniques... 

Metal powder can also be coated onto the workpiece. The 3M Company has developed a cold welding technique in which the workpiece, the metal powder, water, glass shot and additives are tumbled together in a barrel. Coatings are limited to ductile metals such as Cd, An, Sn, Pb, In, Ag, Cu, brass, and tin/lead solder the method is generally suitable only for small parts, and it doesn t produce a fine surfaced, cosmetic coating. Costs are comparable to those for electroplating with afterbake (Kirk-Othmer 1981). 

Before the development of this laser welding technique, the repair of a detached retina required major surgery the photophysical process is now the technique of choice. 

Hardfaeing and Wear-resistant Alloys. These materials, essentially quaternary alloys of cobalt chromium, tungsten (or molybdenum) and carbon, are widely used for industrial hardfaeing purposes. They can be deposited by welding techniques, sprayed on as powders, or produced as separate castings. By using the weld deposition technique, a highly alloyed heat-, wear-, and corrosion-resistant surface can be applied to a... 

Teams of welders join the pipe sections into a continuous tube. The most modern welding techniques involve automatic welding machines. X-ray equipment is used to inspect welds, When several sections of pipe have... 

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