Objectives Worksheet

Automotive Steel GMA (MIG) Welding Qualification Test v.4.2© 2002 Inter-Industry Conference On Auto Collision Repair

1

Notes

WSC01-STHO01-E

STEEL GMA (MIG) WELDING–OBJECTIVES WORKSHEETModule 1–Principals And Setup

A-2

GMA (MIG) welding is a consumable electrode, wire feed, __________

welding process.

A-3

Advantages of GMA (MIG) welding include:

• a _________ heat-affected zone.

• that it can be used to weld all commercial metals and alloys.

• it works well in all welding positions.

• it requires minimal postweld cleaning.

B-2

The amount of heat put into the base metal during GMA (MIG) weld-

ing is a function of voltage and ____________ outputs of the welding

machine and the travel speed at which the welding gun is moving.

B-3

The current, or amperage, ___________ of a GMA (MIG) welder is

adjusted by changing the wire speed setting.

B-5

The voltage output of a typical GMA (MIG) welder remains

____________ once set. The voltage controls the rate at which the

electrode wire burns and must be matched to the current or amper-

age being used.

B-7

GMA (MIG) welders are plugged into an ____ power source and the

power is converted to a ____ output.

Please refer to the Student CD-ROM for a copy of the:

• Textbook.• Video Scripts.• Self-Study Narration

Scripts.• Student Handouts (if

applicable).


2

NotesB-8

______________ polarity is when the electrode is positive and the

workpiece is negative, and is used with solid electrode wire. It is used

most often for collision repairs because it provides a stable arc with

the best fusion and less weld surface to grind off.

B-9

_________ polarity is when the workpiece is positive and the electrode

is negative. It puts most of the heat on the workpiece and is used with

flux-cored electrode wire.

B-12

Because less heat is generated and the metal stays cooler, the

________-___________ transfer method is the preferred method for

welding on sheet metal.

C-2

For every .025 mm (.001") of metal thickness, ______ amp is

required.

C-4

Duty cycle is how many minutes out of ______ a welding machine can

operate continuously at a rated amperage.

C-5

ER: Electrode rod

70: Tensile strength of at least __________ psi

S: Solid electrode wire

6: Chemical makeup of wire and ability to keep oxygen out of weld

C-8

_________ wire is the recommended electrode wire for collision repair

welding.


3

NotesC-9

_________ wire can also be used for collision repair welding, but its

availability may be limited.

C-10

______-___________ wire requires no shielding gas and is not recom-

mended for metal thinner than 18 gauge.

C-13

115-volt welders may be originally set up for flux-cored wire and require

a conversion kit for solid wire. These machines may also require the

___________ be switched for collision repair welding.

C-14

The electrode wire diameter used depends on the ______________

required for the welding being done.

C-18

The cast of a spool of electrode wire should have a ______________

of at least 300 mm (12").

The helix of a spool of electrode wire should have a height of more

than 25 mm (1").

C-19

If the pressure of the drive rolls against the wire is not high enough,

the wire will not be pulled through the wire feeder.

If the pressure of the drive rolls against the wire is too _______, the wire

may deform and wind into a spiral that causes it to bind.


4

NotesC-20

Shielding gas protects the weld from gases that cause _____________.

C-22

A mix of 75% ___________ 25% CO2 is the preferred gas for collision

repair welding on mild and high-strength steels.

Pure argon shielding gas is used for welding on aluminum or when

using silicon bronze electrode wire.

C-24

Pure ______ shielding gas produces a much hotter weld bead, and

therefore is not recommended for welding on high-strength steel.

C-26

The shielding gas flow meter should be set at __________ cfh for col-

lision repair welding.

C-29

The welding gun liner guides the electrode wire from the drive rolls to

the contact tip. The inside diameter must be matched to the diameter

of the electrode wire being used.

Copper-coated wire tends to leave copper particles that can build up

in the liner and affect wire _____________. Liners can be cleaned of

copper particles by blowing compressed air through them.

C-30

The contact tip transfers ____________ to the electrode wire and must

match the electrode wire diameter.


5

NotesC-31

Shielding gas nozzles can have an anti-spatter compound applied to

the __________ to reduce the buildup of spatter between the nozzle

and contact tip.

C-32

_____________ shielding gas nozzles are typically used with the short-

circuit transfer method.

C-33

The work clamp completes the output circuit of the welder and is not

the electrical ground for the welding machine.

The work clamp should be placed as ________ to the weld site as

possible.

D-1

Before setting up a welding machine read the equipment maker’s

______________.

E-1

It is important that surfaces to be welded are cleaned of all finish,

undercoating, corrosion, dirt, oil, and grease. Do NOT remove any

________________ coatings.

E-2

Weld-through primer should be applied to any bare metal mating

surfaces where galvanized coatings have been removed.


6

NotesE-3

Weld-through primer does not allow proper adhesion of other coatings

and should have any excess _____________ before applying additional

topcoats.

Some vehicle makers do not recommend the use of weld-through

primer.

F-2

Travel speed is how fast the technician moves the welding gun along

the joint and affects weld bead _______________, size, and shape.

F-5

__________ angle is the angle the welding gun is pointed either towards

or away from the direction of gun travel. It affects weld bead penetra-

tion and shielding gas coverage.

F-6

________ angle is the angle that the plane of the welding gun has in

relation to the joint being welded. It controls where the wire is being

pointed at the joint, and affects penetration, shielding gas coverage,

and undercut.

F-7

The _____ technique increases penetration and is when the welding

gun is pointed at and dragged away from the weld bead. It produces

a higher, narrower bead.

F-8

The _____ technique decreases penetration and is when the welding

gun is pointed and pushed away from the weld bead. It produces a

flatter, wider bead.


7

NotesF-9

The distance from the end of the contact tip to the end of the

wire is called stick-out. For 0.6mm (.023") wire, stick-out should be

_______ mm (________").

F-10

Changes in stick-out result in changes in resistance, which causes a

change in amperage output.

Increasing stick-out _____________ the amperage output and therefore

the penetration of the weld, and decreasing stick-out increases these

same parameters.

F-11

Welding positions include:

• Flat–This is the easiest position to weld in.

• Horizontal–This is easiest if the welding gun is angled upward.

• Vertical–On thin-gauge metal this is easiest if the welding gun is

angled upward and pulled downward.

• _____________–This requires lower heat settings than the other

positions.

G-2

When tuning a welding machine, use the same _____________ metal

as that to be welded on the vehicle, use proper stick-out, and test the

strength of the sample weld.

G-4

Causes of ______ ___________ include too much drive roll tension,

tangled wire, clogged gun liner, and too small a contact tip for the

wire diameter.


8

NotesH-1

Heat management techniques that can be used limit heat buildup and

help avoid metal _____________ include stitch welds, skip welds, and

alternating plug welds.

H-2

A _________ weld is made by starting and stopping briefly between

welds.

H-3

_______ welds are made by making short 13–19 mm (1⁄2–3⁄4") long welds

in random locations along the joint and then filling in the spaces.

Cold starts can be a problem when making skip welds on heavy gauge

metal.

H-4

_____________ plug welds are made by randomly alternating the loca-

tion that plugs welds are made at and not making two or more welds

next to each other concurrently.

I-1

Causes of poor weld ______________ include too low of heat settings,

travel speed too fast, stick-out too long, and improper root gaps.

I-2

Melt-through that creates a ripple is a sign of _________ weld

penetration.

I-4

_________________ may be caused by heat settings that are too high,

travel speed too slow, stick-out that is too short, incorrect welding gun

angles, and root gaps that are too wide.


9

NotesJ-2

Causes of _____________ include:

• Shielding gas not turned on

• Shielding gas flow rate too low

• Pinched or leaking shielding gas hose

• Improper shielding gas type

• Dirty electrode wire

• Dirty of plugged shielding gas nozzle

• Contaminated base metal

• Stick-out too long

J-4

A _______________ bead may be caused by an unsteady hand, a worn

contact tip, too much stick-out, voltage settings too high, and uneven

travel speeds.

J-5

Causes of ___________ include unbalanced voltage and amperage

settings, worn or recessed contact tips, improper shielding gas flow,

excessive welding gun angles, and contamination or corrosion of the

base metal.

J-6

______________ is a groove cut into the base metal at one or both

sides of the weld bead, and may be caused by unbalanced voltage and

amperage settings, or improper welding gun angles.


1

NotesSTEEL GMA (MIG) WELDING–OBJECTIVES WORKSHEETModule 2–GMA (MIG) Plug Weld

A-2

GMA (MIG) _______ welds join two or more lapped pieces together

and are used to replace factory spot welds.

A-3

Plug weld holes should be the size recommended by the vehicle maker

or ____ mm (____") if no recommendation exists.

When plug welding three pieces together, the hole in the top piece

should be larger than the hole in the middle piece.

A-4

GMA (MIG) plug welds are made by aiming the electrode, at a ____°

angle, at the base metal through the hole in the top piece and circling

around the hole to fuse the edges.

B-1

Test plug welds should be made on the same_______ and thickness

metal and in the same position as that to be welded on the vehicle.

Weld-through primer should be used if it is going to be used on the

vehicle.

Test welds should be visually and destructively tested.

B-2

When visually inspecting a plug weld, the ______ must be completely

filled, with a nugget height of no more than 3 mm (1⁄8"), with no cracks,

porosity, or undercut.


2

NotesB-3

The _____________ of a plug weld should show melt-through as evi-

dence of penetration, but have a melt-through height no greater than

1.5 mm (1⁄16").

B-4

Plug welds may be destructively tested using tensile shear testing or

by doing a twist test.

To do a twist test on a plug weld:

1. Secure in a vise

2. Twist top piece off

3. Measure nugget hole diameter

The nugget hole diameter for a plug weld made through an 8 mm (5⁄16")

hole must be at least ___ mm (____").

B-5

Making plug welds on a vehicle:

1. ________ the mating surfaces.

2. Drill or punch holes the size recommended by the vehicle maker,

or 8 mm (5⁄16") if no recommendation exists, in the same location

as the spot welds being replaced.

3. Prime bare metal with weld-through primer if applicable.

4. Clamp the joint tightly together.

B-6

Making plug welds on a vehicle:

5. ______________ weld-through primer form the immediate weld

zone.

6. Attach the work clamp as close to the weld site as possible.

7. Make the plug welds, ensuring that the hole is completely filled.

8. Dress the welds if necessary.


1

NotesSTEEL GMA (MIG) WELDING–OBJECTIVES WORKSHEETModule 3–GMA (MIG) Fillet Weld

A-2

GMA (MIG) fillet welds are ______________ shaped beads deposited

in a corner formed by a lap, corner, or T-joint.

A-3

When making a fillet weld the electrode should be aimed at the base

metal and the welding gun held at a ____° travel angle.

B-2

To pass a visual inspection, a fillet weld must have the joint completely

filled with no cracks or undercut. ______________, skips, and voids,

can be no greater than 3 mm (1⁄8") and the total of all not to exceed

6 mm (1⁄4").

B-3

The backside of the fillet weld must have ______-_____________ as

evidence of penetration. The melt-through width should be 5 mm (3⁄16")

or less and melt-through height can be no more than 1.5 mm (1⁄16").

B-4

To destructively test a fillet weld on lap joint:

1. Secure the bottom piece in a vise.

2. Rock the top piece back and forth until it breaks free.

3. Look for evidence of complete ___________. Metal should pull out

of the top piece along the entire length of the weld, and the weld

should hold firm to the bottom piece.


2

NotesB-5

Avoid removing the zinc coating when cleaning mating surfaces.

_____________ weld-through primer from the immediate weld zone.

B-6

Attach the work clamp as __________ to the weld site a possible.


1

NotesSTEEL GMA (MIG) WELDING–OBJECTIVES WORKSHEETModule 4–GMA (MIG) Butt Joint With Backing Weld

A-2

A butt joint with backing is two pieces nearly butted against each other

with a backing piece usually the same thickness as the other pieces

behind the joint.

The root gap between the top pieces should be 2–3 times the metal

thickness. The size of the root gap will affect weld ________________

into the backing piece.

A-3

The butt joint with backing weld is made using a ____° work angle and

a 70° travel angle. The electrode wire is aimed at the backing piece

and the weld is either pushed or pulled.

B-2

To pass a visual inspection, a butt joint with backing weld must have

the joint completely filled with no cracks or undercut. Porosity, skips,

and voids can be no greater than ____ mm (____") and the total of all

should not exceed 6 mm (1⁄4").

B-3

The backside of the butt joint with backing weld must have melt-

through as evidence of penetration. The melt-through width should be

____ mm (____") or less and melt-through height can be no more than

1.5 mm (1⁄16").


2

NotesB-4

To destructively test a butt joint with backing weld:

1. Bend top pieces towards each other.

2. Bend the backing piece in towards itself.

3. Hammer the sample flat.

4. Tighten the top pieces in a vise, just below the joint.

5. Rock the backing back and forth until it breaks free.

6. Look for complete fusion. There should be metal ______________

from the pieces that the weld separates from, and the weld should

remain firmly on the other piece.

B-5

When making a butt joint with backing weld on a vehicle, some pro-

cedures may call for the backing to have ________ welds in one or

both of the top pieces.

B-6

Do not reduce the thickness of the surrounding metal when

_____________ welds.


1

NotesSTEEL GMA (MIG) WELDING–OBJECTIVES WORKSHEETModule 5–GMA (MIG) Open Butt Joint Weld

A-2

An open butt joint is two pieces in the same plane ________ against

each with a gap between of 0–1 times the metal thickness.

A-3

The open butt joint weld is made using a 90° work angle and a 70°

travel angle. The electrode wire is aimed at the ___________ of the

joint and the weld is either pushed or pulled.

B-2

To pass a visual inspection, an open butt joint weld must have the joint

completely _________ with no cracks or undercut. Porosity, skips, and

voids can be no greater than 3 mm (1⁄8") and the total of all should not

exceed 6 mm (1⁄4").

B-3

The backside of the open butt joint weld must have melt-through as

evidence of penetration. The melt-through width should be the same

as the weld bead on the front side, and melt-through height can be no

more than _____ mm (___").

B-4

To destructively test an open butt joint weld:

1. Bend the pieces along the weld axis, with the ______ of the weld

on the face of the bend.

2. Hammer the sample flat.

3. Inspect for weld metal cracks. Cracks are allowed as long as they

show no visibly detected flaws and the pieces do not completely

separate.


2

NotesB-5

When making an open butt joint weld on a vehicle, it may be neces-

sary to make the weld as a series of short ________ welds to avoid

burn through.

Documents

Objectives Worksheet