Mitsubishi Galant (2004+). Manual — part 32

WELDING

TSB Revision

BASE OF BODY REPAIR

9-7

Galvanized steel plate (SECC)

CAUTION

If the total thickness of the plates at the weld
places is 3 mm (0.1 inch) or more, use plug weld-
ing, because spot welding will not provide suffi-
cient welded strength.

*: For welding steel plates of different thicknesses,
conform to the welding conditions for the thinner
plate.

.

USING A TEST PIECE TO CHECK NUGGET FORMATION
Weld a test piece of the same type of steel plate as the panels
to be welded. Try to twist the piece, and also check the nugget
diameter.
Using the weld point as an axis, apply force in the direction indi-
cated by the arrows in the illustration, and determine the
strength of the weld.

1. Good (The welded part remains at one side).
2. and 3.

The weld conditions are unsatisfactory; adjust the welding
current, the current application time, and/or the applied
pressure.

.

CHECKING NUGGET STRENGTH FOLLOWING SPOT
WELDING

CAUTION

•

Stop wedging the tip or the chisel or flat-tipped screw-
driver as soon as the size of the nuggets can be deter-
mined; do not wedge it in more than 30 mm (1.2
inches).

•

After checking the nugget diameter, correct the place
where the checking was done.

Wedge the tip of a chisel or flat-tipped (-) screwdriver into the
space between two weld points.

•

The nuggets should not break apart.

•

The nugget diameter should be 3 mm (0.1 inch) or more.

PANEL
THICKNESS*
[mm (in)]

NUMBER OF REPAIR WELD (PERCENTAGE OF FACTORY WELD)

SAFETY
EQUIPMENT
AREA

0.9 (0.04) or
less

100% Same number as factory welds

1.0 (0.04)

200% Maintain pitch of at least 18 mm (0.7 inch); if not possible, plug weld.

1.2 (0.05) or
more

100% Same number as factory welds; plug welding

OTHER
AREA

0.9 (0.04) or
less

100% Same number as factory welds

1.0 (0.04)

140% Maintain pitch of at least 18 mm (0.7 inch); if not possible, plug weld.

1.2 (0.05) or
more

100% Same number as factory welds; plug welding

AB200032AB

WELD POINT

1

2

3

AB200033AB

3 mm (0.1 in)

WELDING

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BASE OF BODY REPAIR

9-8

GAS SHIELD ARC WELDING

M4090003000021

Gas shielded arc welding is one method of arc weld-
ing. In this method, while the area to be welded is
shielded from the air by a layer of inert gas (such as
argon) or carbon dioxide gas, the filler metal (wire) is
fed from the torch nozzle at a constant rate and an
electric arc is generated between the tip of the wire
and the area being welded, thus generating heat to

fuse the area. There are two types of gas shielded
arc welding, classified according to the gas they use
as the shield gas: carbon dioxide (CO

2

) gas shielded

arc welding, and MIG welding, which uses an inert
gas (such as argon).
However, herein we will refer to all gas shielded arc
welding as MIG welding.

MIG SPOT WELDING

This welding method is used in areas where regular
spot welding cannot be done. The two panels are
stacked together, the tip of the torch (one designed
for use in MIG spot welding) is positioned on one
side, an arc is generated for a short time, and a par-
tial melting is done to obtain a spot weld.

.

Procedure

CAUTION

•

Make sure that the area to be welded is per-
fectly clean; remove oxidation film, scales,
rust, dirt, etc.

•

The two panels to be welded must be in per-
fect contact with each other.

•

The number and pitch of the weld points
should be approximately the same as for the
factory welds.

1. Position the tip of the nozzle at a right angle to the

surface to be welded.

2. Being sure that the two prongs are not leaning to

either side, set them in direct contact with the
panel to the welded.

AB301456

NOZZLE

WIRE

CONTACT TIP

METAL VAPOR

SHIELD GAS

AB

AB200036

GAS CUP

GAS OUTLET

WIRE

AC

WELDING

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BASE OF BODY REPAIR

9-9

3. Welding will begin when the torch trigger is

squeezed, and will stop automatically when the
weld is complete.

.

FEATURES OF MIG SPOT WELDING
In comparison to resistance spot welding, MIG spot
welding has the following advantages and disadvan-
tages.

.

ITEM

MIG SPOT WELDING

ELECTRIC RESISTANCE SPOT WELDING

Working
characteristics

•

Light weight

•

Welding possible at various
positions (no limit upon welding
positions)

•

Although the torch with separate
transformer is lightweight, the torch
combined with transformer type is heavy.

•

The arm must be exchanged to conform
to the weld location.

Weld time/point

Slow (0.5 second or more)

Fast (0.5 second or less)

Treatment after
welding

Necessary (grinding by grinder,
etc.)

Unnecessary

Power

High voltage, low current
(15

−

30 V, 50

−

200 A)

Low voltage, high current
(2

−

4 V, 4

−

10 kA)

Flux material

•

CO

2

(carbonic acid gas)

•

Weld wire

Unnecessary

Weld points/10
minutes
(rate of use)

•

25 points or less

•

Arc instability and contact tip
burn if rate of use is exceeded.

•

50

−

60 points

•

Welding rod deformation and transformer
overheating if rate of use is exceeded.

Distortion caused by
welding

Occurs easily

Rare

Welding strength

Depends on strength of welding
wire itself.

•

Same as base material

•

Little oxidation

•

Uniform welding quality

Weld traces

Button head (slightly convex)

Slight concave
(Almost no indentation if swivel tip
used.)

Re-repairability
(cutting away welded
area)

Difficult
(Much welding trace High hardness
of weld points)

Easy
(Can be separated by spot cutter.)

AB200037AB

SWIVEL TIP

WELDING

TSB Revision

BASE OF BODY REPAIR

9-10

The MIG welding done around the doors, wheelhouse arches,
etc., to prevent the flanges from coming undone after hemming
work is also called MIG spot welding.

PLUG WELDING

CAUTION

In order to prevent the formation of blowholes, fill in each
hole completely in one pass.Be sure that the two panels
are in perfect contact.Be sure that the penetration goes all
the way to the bottom panel.
Plug welding is done by making holes 5

−

6 mm (0.2 inch) in

diameter in one of the panels to be welded together, positioning
the torch at a right angle to the holes and then filling in the
holes one at a time.

CONTINUOUS WELDING

There are several types of continuous welding: fillet (lap joint)
welding, butt welding, T joint welding, gap welding, etc.; these
are called short-circuit arc welding, and provide a stable arc at
a relatively low current.

.

AB200038 AB

AB301460AB

TORCH

PERFECT
CONTACT

5 – 6 mm
(0.2 in)
DIAMETER
HOLE

AB200041