Resistance wire welding

Large parts can require considerable power requirements. Resistance welding has been applied to complex joints in automotive applications, including vehicle bumpers and panels, and joints in plastic pipe, and in medical devices. Resistance wire welding is not restricted to flat surfaces. If access to the heating element is possible, repair of badly bonded joints is possible, and joints can be disassembled in a reverse process to which they were made. 

Resistance wire welding can be used on any plastic that can be joined effectively by heated tool welding. The process is typically applied to relatively large structures. Contacting the plastic resin manufacturer for details concerning the specific parameters of this process is recommended. 

See also heated tool welding hot-gas welding resistance wire welding laser... 

With resistance wire welding, surface preparation steps are necessary only when one of the substrates cannot be melted (e.g., thermosets and metals). Standard adhesive joining surface preparation processes such as those suggested in the next chapter can be used with these substrates. 

Figure 8.4 Resistance wire welding of thennoplastic joints.

With continuous wire welding processes, it is particularly important to maintain a constant stickout when results need to be critically compared. There is evidence that increasing the stickout reduces the hydrogen level as a result of the increased resistive heating driving off more hydrogen from the wire before it is melted. 

The length of wire in a continuous wire welding process between the contact tip and the arc. A longer stickout results in resistive heating of the welding wire in this region, which may be sufficient to drive off a part of any hydrogenous material embedded in the wire surface. 

Hot Wire Welding. A bonding method whereby a resistance wire is placed between the surfaces to be joined the heat generated melts the adjacent surfaces enough to effect a fused bond. Exposed ends of the resistance wire can then be snipped off. 

Welding by direct heating (heated tool, hot gas, resistance wire, infrared, laser, extrusion)... 

Yokes. The need to couple the end cover to the body of the vessel may be avoided if yokes, external to the vessel, are used to resist the load arising from the internal pressure acting on the closures. However the necessity to move the vessel out of the yoke and remove one of the closures to gain access to the inside of the vessel limits its use for chemical process equipment. Yokes may be pinned, welded, bolted, or wire wound. Both the vessel and yoke maybe wire wound (136). 

Titanium can be forged, bent, cut, stamped, rolled, extruded and successfully welded under argon, making possible a large variety of electrode shapes, i.e. rod, sheet, tube, wire or mesh. It is a very light yet strong material with a high resistance to abrasion. 

Figure 7.6. Experimental set up for temperature-programmed desorption in ultrahigh vacuum. The heat dissipated in the tantalum wires resistively heats the crystal the temperature is measured by a thermocouple spot-welded to the back of the crystal. A temperature programmer heats the crystal at a rate of typically 1-5 K s b Desorption of gases...

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