Mitsubishi MOTORS Lancer Evolution 2008, Body Repair Manual

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WELDING
TSB Revision
BASE OF BODY REPAIR
9-3
ELECTRIC RESISTANCE SPOT WELDING
M4090002000040
Electric resistance spot welding is a method for fus-
ing metal parts together. Two or three metal sheets
are positioned between two copper-alloy electrode
tips, and pressure and a large current are then
applied, thus causing the contacting surfaces to heat
up and fuse together because of the electric contact
resistance.
ADVANTAGES OF ELECTRIC
RESISTANCE SPOT WELDING
•
Because the time required for welding at each
point is brief, the work can be done quickly and at
reduced cost.
•
Because both metals are fused and pressure
applied to make the weld, the strength and reli-
ability are both high.
•
Because the time required to make the welds is
short, there is little occurrence of distortion of the
panel due to heat.
.
PROCEDURE
There are three basic stages in electric resistance spot weld-
ing.
1. Initial pressure application stage
This stage precedes the current application. Applying
pressure to the steel panels through the electrode tips
ensures a uniform contact resistance and a smoother
current flow.
2. Current application stage
While an ample amount of pressure is being applied, the
current is sent through the electrode tips. The contact
resistance causes the contact surfaces of the steel panels to
heat up and fuse together.
3. Holding stage
When the current application is finished and a nugget (a
solidified piece of molten metal) forms at the weld, the
pressure application is continued in order to strengthen the
weld. This is the most important stage of electric resistance
spot welding in ensuring the strength of the weld.
.
AB200026
AB200027
AB200028