SUNSTONE AC 15 kVA, Руководство пользователя, Страница: 11 / 12

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Welds magnetized metal very well .
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Welds thicker metals .
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Makes clean welds that require little or no sanding or filling .
WELD FORMATION
Spot welding relies on metal resistivity (resistance) to heat and fuse metal . A large current is passed through
the workpiece metal . Energy is dissipated due to metal resistance in the form of heat which melts and fuses
the weld materials . There are two phases to the melting process . The welder must overcome both the
material contact resistance and the bulk resistance of the material .
On the micro-scale, material surfaces are rough and only contact in a limited number of locations . In the first
few milli-seconds of weld formation, the high-resistance metal bridges melt, allowing other bridges to come into
contact to continue the melting process . When all of the bridges have fused, the contact resistance is zero .
The bulk resistance of the metal then plays the final role in the weld formation . On the micro-scale, surface
roughness limits surface-to-surface contact . More contact points result in a lower contact resistance .
TIPS
WELD PRESSURE
Several other factors play a part in the contact resistance . The larger the contact resistance the hotter the
resultant weld . On the micro-scale, contact resistance is reduced when more metal bridges or contact points
are formed . Using more electrode pressure creates more metal bridges . This results in a lower contact
resistance and a cooler weld . Conversely, light electrode pressure results in less metal contact, higher
resistance, and a hotter weld . An appropriate amount of pressure should be used to ensure good weld
strength .
ELECTRODE CONFIGURATIONS
Figure 1 shows several electrode configurations used in resistance welding . Figure 1a is called a direct weld .
Current is passed from one electrode through both workpieces and out an opposing electrode . Figure 1b
shows a step electrode configuration . This configuration is used when there is access to only one side of the
workpiece and an electrode can be placed on both materials . Figure 1c is a series configuration . Electrodes
can only be placed on one metal surface from one side . Current is divided between the two parts . This weld
configuration requires more weld energy .
FIGURE 1: Examples of resistance welding electrode configurations:
a . direct, b . step, c . series .