Mitsubishi Evolution X. Manual - part 4

WELDING

TSB Revision

BASE OF BODY REPAIR

9-13

GAS WELDING

Gas welding is a method in which a high temperature flame is
used to melt both a welding rod and the base metal (panels) to
make a fused joint. Oxy-acetylene is the most common type of
gas welding. However, because of the extremely high tempera-
ture of the fused joint, the strength of the steel plate deterio-
rates, and there is a higher possibility of warping. This method,
therefore, is not very suitable for body repair.

The flame in gas welding can be classified according
to the ratio of acetylene and oxygen.

1. Carburizing flame (acetylene-rich flame)

This flame has an excess of acetylene or a defi-
ciency of oxygen. The incomplete combustion
gives off a black smoke, and two flame cores can
be seen inside the deformed yellow flame. The
flame itself is large, but the temperature is rela-
tively low, making this flame unsuitable for weld-
ing.

2. Standard flame (neutral-mixture flame)

This flame has approximately equal amounts of
acetylene and oxygen. The length is shorter than
that of the carburizing flame; the flame core is
rounded; and it is clear and bright.
The carbon in the acetylene is burned completely,
resulting in the maximum obtainable temperature.
This is the flame most commonly used for weld-
ing.

3. Peroxide flame (oxygen-rich flame)

This flame has an excess of oxygen or a defi-
ciency of acetylene. The flame core is shorter
and sharper, and the entire flame has a black-
ish-purplish color. The combustion is unstable,
and the flame flickers continuously.

Notes with regard to gas welding

1. Handle the oxygen and acetylene tanks carefully.
2. Adjust the flame in accordance with the type of

metal being welded.

3. Select a nozzle to match the work to be done.

Avoid overheating and adhesion of foreign matter
(dirt, etc.)

4. The following points are particularly important

when welding mild steel plate.

• Melt a sufficient amount of welding rod, but be

careful not to melt the base metal. Use the
same amount of welding rod on both sides.

• Use the correct amount of welding rod in

accordance with the melting point of the base
metal.

• Avoid welding over places which have been

welded before.

• In order to avoid warping, do only the amount

of tack welding that is absolutely required.

AB200049

Deposite

Base metal

Welding
rod

Oxy-acetylene
flame

AB200050

Flame core

Outer flame

Acetylene cone

1. Carburizing flame

Outer flame

Flame core

2. Standard flame

3. Peroxide flame

BODY REPAIR

TSB Revision

BASE OF BODY REPAIR

9-14

BODY REPAIR

STANDARD BODY REPAIR PROCEDURES

M4090006000075

The following is an explanation of the standard repair
procedures for the monocoque body and the
frame-type body. Furthermore, please refer to the
replacement of welded panels for the applicable
model for information concerning the procedures for
replacement of panels (as classified by position) for
the various models.
NOTE: That reference should be made to page

P.9-27

concerning repair procedures for the frame of

frame-type vehicles.

STANDARD PROCEDURES FOR
REPLACEMENT OF WELDED PANELS

In order to maintain the proper levels of strength,
rigidity, and precision when making welded panel
replacements, it is essential to first gain a thorough
understanding of the body structure, and then to per-
form all repair operations carefully and correctly. In
addition, when performing the operations, be sure to
use the proper protective equipment for each opera-
tion.

CAUTION

• Select an appropriate location for the cutting operation,

and perform the work carefully, so as not to cut into the
reinforcements located inside the pillars, panels which
are not be replaced, or any other such parts.

• There are harnesses, hoses, and other such parts

routed inside the front pillar, the rear pillar, the fender
shield, the side sill, etc.; perform the repair work only
after any such material has been removed.

• For overlap cutting, allow an overlap of approximately

− 50 mm (1.18 − 1.97 inches) when performing the

cutting operation.

1. Rough cutting of panels

First make a rough cutting of a portion of the panel to be
replaced, and then remove that portion, thus making it
easier to break the spot welds.

2. Removal of the paint coat from spot-welded points

In order to clearly identify the spot-welded points, remove
the paint coat from areas where it is difficult to determine the
spot welds.

3. Cutting and separation of spot-welded points

In order to perform cutting and separation of spot-welded
points, use a spot weld cutter which is larger than the size of
the nugget to make a hole only in the panels to be replaced.
When cutting and separating spot-welded points in places
where the surrounding panel or other parts interfere with the
spot weld cutter, or if the operation is hampered by a lack of
space, bend back the flanges in order to make the work
easier.
If a spot-weld cutter cannot be used at all, cut and separate
the spot welds by using a chisel or similar tool.

AB200051

AB200052

AB200053

BODY REPAIR

TSB Revision

BASE OF BODY REPAIR

9-15

NOTE: If a replacement panel is to be mounted by doing
plug welding from the side of the panel remaining on the
body, either a hole can be made in the panel on the body, or
a hole can be made right through both the panel which is to
remain on the body and the panel to be replaced.

CAUTION

When performing this operation, warping of the surround-
ing panels may occur if an excessive amount of heat is
applied; therefore, be careful to avoid doing this.
4. Breaking of brazing and arc welds

Heat only the brazed or arc welded portion (such as the
upper portion of pillars, etc.), and then separate by using a
screwdriver while melting occurs.

5. Finishing work of spot welding

Grind and smooth any weld traces which might be left on the
body surface by using an air grinder or similar tool, being
careful not to damage any of the panels which is not to be
replaced. When performing this operation, be sure to wear
safety goggles (dust proof glasses).

6. Making of holes in new parts for MIG plug welding

Make holes approximately 5

− 6 mm (0.2 − 0.24 inch) in

diameter at points where plug welding is to be performed
because spot welding is not possible.

AB200054

AB200055

AB200056

AB200057

BODY REPAIR

TSB Revision

BASE OF BODY REPAIR

9-16

7. Flange correction for spot weld traces

Correct any flanges that become bent or deformed when
spot welds are broken or during other work.

CAUTION

Do not use a flame for paint coat removal because doing
so might damage the paint coat of panels which are not to
be replaced, thus causing corrosion.
8. Removal of the paint coat from new parts and from the

vehicle body
In order to provide for the proper flow of electric current
during spot welding operations, remove the paint coat from
both sides of the new part and the body by using a polisher
wheel or similar tool.

9. Rough cutting of new parts

Cut off the unnecessary portions of new parts. Allow an
overlap of approximately 30

− 50 mm (1.18 − 1.97 inches)

when performing overlap cutting of the pillars, side sills, or
other locations.

CAUTION

Carefully select the location for cutting, taking care not to
cut a reinforcement at the inner side of a pillar, etc. or a
panel that is not to be replaced.
10.Overlap cutting of new parts

For locations in which butt welding is to be done, first
temporarily attach the new parts to the body, and then cut
the two panels simultaneously.
NOTE: If a reinforcement or a panel which is not to be
replaced is cut accidentally, first repair the mistake by weld-
ing before proceeding with the rest of the work.

AB200058

AB200059

AB200060

AB200061

Edge of the
new part

Edge of the
panel on the body

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