Other Welding Techniques

In the laser welding technique, a high intensity laser beam is used to increase the temperature at the joint interface of thermoplastic material to or above the melting point. 

Microwave welding uses high frequency electromagnetic radiation to heat material located at the joint surface. The generated heat melts thermoplastic materials at the joint surface, producing weld on cooling. 

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Many TPs can be heat welded. However, as with other welding techniques, certain fillers or too much of a particular filler, could prevent good bonding. There are nevertheless, certain fillers that can improve bonding action. Heat welds can also be used with friction or spin welding of TP joints. 

The force (F) required to cause failure of the welded specimens in shear was measured on an Instron Model 4206 Universal testing machine at a cross-head speed of 5 mm/min. The stress at break was normalized by the weld cross-sectional area. The weld length was fixed at 15nun and the width was measured using a calibrated computer scanner. It is important to note that, nnlike many other welding techniques, the weld width W) is a function of LTW power, material properties and part thickness. It therefore needs to be measured for each weld. 

Residual stresses occur from welding and other fabrication techniques even at very low stress values. Unfortunately, stress relief of equipment is not usually a reliable or practical solution. Careful design of equipment can eliminate crevices or splash zones in which chlorides can concentrate. The use of high-nickel stainless steel alloy 825 (40% nickel, 21% chromium, 3% molybdenum and 2% copper) or the ferritic/austenitic steels would solve this problem. 

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. 

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. 

Plastic sections, which are too thick to be heat-sealed, may usually be welded. There are three major methods in commercial use heat, solvent, and ultrasonic. In general, these methods are limited to use with thermoplastic materials. These welding techniques have done much to lower the total cost of using plastics in the construction and other industries. 

FEP parts can be joined by the spin welding technique. Joints can be designed to allow the rotation of one part relative to the other at a fast rate. Heat generated during the rotation melts the FEP at the joint and allows the formation of a weld. FEP requires minimal speed (3,000 rpm) for spin welding. In one example, a joint with better than 60% of the tensile strength of base FEP was obtained,... 

When thick-walled hollow molded artieles and molded articles with a shape having thick-walled sections and thin-walled sections are produced, the molded article is produced in two parts. These parts are eventually eon-nected by welding. Alternatively, the two parts are placed in another mold so that they face each other at the parting lines. Then, molten resin is injected about the periphery of the opposed faces to connect the parts. This technique is addressed as insert molding, or overlap molding. Other welding methods include ... 

Hardfacing, on the other hand, is a thick layer process. By means of varions welding techniques, wear-resistant alloys in rod, wire, or powder form build strong metallurgical bonds in the fused state with the surface, which is also fused. Mixing should be kept as low as possible. There is an exceptionally large variety of additives available therefore, the requirement for mechanical workability... 

Flash welding has the following advantages compared with other polymer welding techniques that use... 

Adhesive bonding of wood is very well established see Wood adhesives - basics. A relatively novel joining technique is discussed here. Thermoplastic welding techniques, which are widely used in the plastic and car industries, have recently been applied also to joining wood, by melting a thermoplastic polymer between the two wood surfaces to be joined. A variety of techniques such as uldasound, mechanical friction and others have been used to melt the thermoplastic polymer in situ. 

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