Specialty GMAW/MIG Welding 4th year

Question 1

What is GMAW?

Answer 1

Gas metal arc welding

Question 2

List some possible electrical shock hazards when MIG welding.

Answer 2

not having gloves and shoes in a dry and good condition, welding on a wet surface or wet weather condition, not checking electrical connections and insulation on the welding gun and cables are in good condition.

Question 3

Eyes should be protected from what when welding?

Answer 3

electric arc

Question 4

The face and body should be protected, why?

Answer 4

Radiation reflected from shiny surfaces can cause sunburn to the skin, the reflected light can become a concern when work is done inside tanks.

Question 5

Should ear plugs be worn?

Answer 5

yes

Question 6

What protective clothing is preferred?

Answer 6

dark-coloured tightly woven denim clothing is preferred.

Question 7

Is ventilation mandatory?

Answer 7

yes, adequate ventilation is mandatory for all GMAW operations.

Question 8

Extreme caution should be taken when welding metals that contain zinc, why?

Answer 8

Fumes from these metals can be toxic, you should use adequate ventilation.

Question 9

Should the valves be closed and protective caps be installed when handling cylinders?

Answer 9

Yes, when returning cylinders you should ensure that valves are closed.

Question 10

What are three metal transfer methods?

Answer 10

Short-circuit transfer
Globular transfer
Spray arc transfer

Question 11

The welding of sheet metal uses which of the three methods?

Answer 11

Short-circuit transfer

Question 12

The globular transfer is generally avoided why?

Answer 12

Due to spatter problems and poor weld metal appearance.

Question 13

The spray mode of metal transfer is used for joining materials_____and greater in thickness.

Answer 13

2.4 mm

Question 14

When the wire speed is increased the_______are increased.

Answer 14

currents

Question 15

What will happen if the voltage is too high or the wire is too low?

Answer 15

the wire will burn back,feed,make contact, burn back, feed, make contact ans so forth.

Question 16

What will happen if the voltage is too low or the wire speed is too high?

Answer 16

you will get stubbing ( which is where the wire in not burning off at a fast rate and is actually striking the bottom of the weld pool.

Question 17

After setting the machine recommendations
( charts) what must be done to insure good set-up conditions are achieved?

Answer 17

play around with it to make sure that if the wire seems to be burning off, losing the arc, advancing, re-establishing the arc and burning off again, you are definitely running too high voltage or too low a wire speed.

Question 18

What are the benefits of flux cored welding?

Answer 18

-All position capability
-leaves a good quality weld metal deposit
higher deposition rates than shielded metal arc welding.
-low operator skill required
-metallurgical benefits that can be gained from a flux

Question 19

Each type of shielding gas can affect the weld characteristics in what way?

Answer 19

each have a specific effect on the arc characteristics, the depth of fusion, the weld bead profile, the weld speed, the cleaning action and the mode of metal transfer,

Question 20

What is the primary purpose of shielding gas?

Answer 20

to prevent the molten weld metal from absorbing elements such as oxygen and nitrogen from atmospheric air.

Question 21

List some items that should be considered when selecting shielding gas.

Answer 21

base metal type and thickness
welding process
joint design and positioning
type of metal transfer

Question 22

Argon has a high or low thermal conductivity?

Answer 22

low

Question 23

helium has a high or low thermal conductivity?

Answer 23

high

Question 24

Can argon cause suffocation?

Answer 24

yes

Question 25

carbon dioxide can act as an asphyxia. True or False?

Answer 25

true

Question 26

Co2 is the cheapest gas available. True or false?

Answer 26

true

Question 27

When oxygen is added to shielding gas it can help with the puddle fluidity. True or false?

Answer 27

true

Question 28

Hydrogen is the lightest know element and highly combustible. True or false?

Answer 28

true

Question 29

Nitrogen is considered inert. True or false?

Answer 29

true

Question 30

Nitrogen is flammable. True or false?

Answer 30

false

Question 31

C-25( argon-carbon dioxide) is characterized by____?

Answer 31

a stable arc, good puddle control and little spatter.

Question 32

What is the current and polarity for GMAW of stainless steel?

Answer 32

DCEP

Question 33

What is the correct traverse and longitudinal gun angles?

Answer 33

For GMAW welding, the gun angle is typically held at a 15-30 degree angle to the workpiece for both traverse and longitudinal welds. A slight drag angle is also commonly used, which means that the gun is pulled in the direction of travel. This angle helps reduce spatter and allows for proper gas coverage.

Question 34

Which gas is preferred for welding stainless steel?

Answer 34

helium

Question 35

Must the material be cleaned before welding?

Answer 35

yes

Question 36

Stainless steel has a high or low thermal conductivity?

Answer 36

low

Question 37

Stainless steel has a high thermal expansion rate. True or false?

Answer 37

yes

Question 38

What is the ore of aluminum?

Answer 38

bauxite

Question 39

What are some advantages of GMAW on aluminum?

Answer 39

enables aluminum welding to be done at high speeds in all positions,less distortion and deep penetration.

Question 40

Aluminum has a high or low thermal conductivity?

Answer 40

high

Question 41

What is the melting point of aluminum?

Answer 41

The melting point of aluminum is 660.32°C (1220.58°F).

Question 42

What precautions should be taken when dealing with the highly reflective materials?

Answer 42

eye and skin protection

Question 43

Does aluminum develop an oxide?

Answer 43

yes

Question 44

Aluminum coefficient of expansion is how much greater than steel?

Answer 44

twice as much

Question 45

Higher heat is needed when welding aluminum, why?

Answer 45

Due to its high thermal’s conductivity,aluminum requires a heat input 4 times more rapid than mild steel to raise its temperature to melting point. This requires the the use of an intense heat source for successful welding.

Question 46

GMAW enables aluminum welding to be done at high speeds. True or false?

Answer 46

True

Question 47

What gas is normally used to weld aluminum?

Answer 47

Aragon

Question 48

What is the current and polarity use for welding GMAW aluminum?

Answer 48

DCEP

Question 49

Name two types of wire feeders used for welding aluminum?

Answer 49

Push type, pull type

Question 50

Dirty materials will cause what problems to the welds?

Answer 50

Porosity

Question 51

A lack of shielding gas will cause what problems to the welds?

Answer 51

Porosity, incomplete fusion, weld splatter.

Question 52

What is the correct traverse gun angle for a lap seam?

Answer 52

45 degrees

Question 53

How far should the electrode stick out?

Answer 53

Between 0.5-1.5 inches

Question 54

What is stubbing?

Answer 54

The proccess of accidentally striking the electrodes or wire against the base metal.

Question 55

What are the correct gas flow settings?

Answer 55

For GMAW, the recommended gas flow rate typically ranges from 20 to 50 cfh, depending on the type of gas being used and the welding application. A lower flow rate is typically used for welding thinner materials, while a higher flow rate is used for thicker materials or for welding in a windy environment.

Question 56

How is the electrode sized?

Answer 56

The diameter of the electrode is typically measured if fraction of an inch or millimeters.

Question 57

Where should the contact tip be placed?

Answer 57

The contact tip should be placed as close as possible to the workpiece without making contact with it.

Question 58

Sketch the symbol to a fillet weld?