HF25D LINEAR DC RESISTANCE WELDING CONTROL
990-333
F-1
APPENDIX F
THE BASICS OF
RESISTANCE WELDING
Resistance Welding Parameters
Resistance welding heat is produced by passing electrical current through the parts for a fixed time
period. The welding heat generated is a function of the magnitude of the weld current, the electrical
resistance of the parts, the contact resistance between the parts, and the weld force applied to the parts.
Sufficient weld force is required to contain the molten material produced during the weld. However, as
the force is increased, the contact resistance decreases. Lower contact resistance requires additional
weld current, voltage, or power to produce the heat required to form a weld.
The higher the weld force, the greater the weld
current
,
voltage
,
power
, or
time
required to produce a
given weld. The formula for amount of heat generated is
I
2
RT
-- the square of the weld current [
I
]
times the workpiece resistance [
R
] times the weld time [
T
].
Welding Parameter Interaction
Interaction of Welding Parameters
HEAT
Excessive
Insufficient
CAUSE
PR OBLEM
Parts Overheating
W eak W eld
Insufficient Nugget
Metal Expulsion
W arping
Discoloration
Electrode Dam age
FO RC E
Excessive
Insufficient
CAUSE
PR OBLEM
Parts Overheating
W eak W eld
Insufficient Nugget
Metal Expulsion
W arping
Discoloration
Electrode Dam age
TIME
Excessive
Insufficient
CAUSE
PR OBLEM
Parts Overheating
W eak W eld
Insufficient Nugget
Metal Expulsion
W arping
Discoloration
Electrode Dam age
Summary of Contents for HF25A
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