Power Fist 8630196, Руководство пользователя

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8630196 120 Volt spot Welder V 4.2
14 For technical questions call 1-800-665-8685
Previously, the formula for heat generation was used. With the addition of the time element, the formula is
completed as follows:
H=I
2
RTK
Values
H
Heat
I
2
Welding Current Squared
R Resistance
T Time
K Heat Loss
Control of time is important. If the time element is too long, the base metal in the joint may exceed the melting
(and possibly the boiling) point of the material. This could cause faulty welds due to gas porosity. There is also
the possibility of expulsion of molten metal from the weld joint, which could decrease the cross section of the
joint weakening the weld. Shorter weld times also decrease the possibility of excessive heat transfer in the
base metal. Distortion of the welded parts is minimized, and the heat affected zone around the weld nugget is
substantially smaller.
PRESSURE
The effect of pressure on the resistance spot weld should be carefully considered. The primary purpose of
pressure is to hold the parts to be welded in intimate contact at the joint interface. This action assures
consistent electrical resistance and conductivity at the point of the weld. The tongs and electrode tips should
NOT be used to pull the workpieces together. The resistance spot welding machine is not designed as an
electrical “C” clamp. The parts to be welded should be in intimate contact BEFORE pressure is applied.
Investigations have shown that high pressure exerted on the weld joint decrease the resistance at the point
of contact between the electrode tip and the workpiece surface. The greater the pressure, the lower the
resistance factor.
Proper pressures, with intimate contact of the electrode tip and the base metal, will tend to conduct heat away
from the weld. Higher currents are necessary with greater pressure and, equally, lower pressures require less
amperage from the resistance spot welding machine.
NOTE: This fact should be carefully noted particularly when using a heat control with the various
resistance spot welding machines.