Spot welding resistance

Figure 10-158A. Styles of Mueller Temp-Plate heat transfer plates. (1) Double-embossed surface, inflated both sides. Used in immersion applications, using both sides of the heat transfer plate. (2) Single-embossed surface, inflated one side, used for interior tank walls, conveyor beds. (3) Dimpled surface (one side), available MIG plugwelded or resistance spot welded. Used for interior tank walls, conveyor belts. (Used by permission Bui. TP-108-9, 1994. Paul Mueller Company.)...

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

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

A reliable determination of the adsorbent temperature is obviously a crucial requirement of the thermal desorption method. Thermocouples are mostly used to this end. With disks and foils, a thermocouple can be spot-welded onto the back or edge of the sample. Thermocouples can be attached also to ribbons as well as to the wall of the vessel containing an evaporated film. With powdered adsorbents, thermocouples are located in the layer of the sample. The adsorbents in the form of filaments and ribbons are frequently used simultaneously as resistance thermometers, switched... 

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...

Bonding enables stresses to be distributed over large areas in the joint, thus avoiding the local stress concentrations present in riveted or spot-welded joints which can reduce fatigue resistance. 

Zinc—Cobalt. Alloys of Zn—Co usually contain 0.3—0.8% cobalt. Higher cobalt alloys, from 4—8%, have shown better salt spray resistance (156), but the commonly plated alloy is 0.3—0.8%. One automotive company specifies 0.3—1.0%. Cobalt is expensive, and economics favor the lower alloys. Costs have been quoted for zinc—cobalt at 1.2 times the cost of chloride zinc, with zinc—nickel alloys at 1.5—1.6 times the chloride zinc. Deposits can be very bright, but the improved corrosion resistance advantage requires yellow or bronze chromates. Alkaline baths give fewer problems in plating components with lapped, spot-welded seams. 

In these approaches, several different forms of welding can be utilized such as resistance spot welding, gas tungsten spot welding, laser spot welding, and electron beam spot welding. However, resistance spot welding is the most popular and well accepted of these methods. 

The surface preparation method must be carefully considered, especially if the completed weldbond is to have long-term durability to hostile environments. The surface preparation should provide an optimal surface for both adhesion and welding. Thus, the choice of surface treatment is crucial, and there can be a conflict of requirements. The spot welding process requires a low electrical surface resistance, and many adhesive surface preparation processes provide a high surface resistance because of oxide layer buildup. When it is impossible to harmonize on a surface treatment, current practice tends to favor treatments that yield good weld nuggets at the expense of the adhesive bond. 

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