Welding

Question 1

What type of weld joint must be used to weld magnesium?

Answer 1

Only butt welds are used to weld magnesium. This is to prevent the possibility of trapping
Contaminates.

Question 2

Why must all flux be removed from the metal after welding magnesium?

Answer 2

Any flux left on the metal will result in severe corrosion.

Question 3

What must be done in order to successfully weld titanium?

Answer 3

The weld zone must be shielded with an inert gas such as Helium or Argon.

Question 4

What is gas shielded arc welding?

Answer 4

A gas is used as a covering shield around the arc to prevent the atmosphere from contaminating the
Weld.

Question 5

What are the advantages of gas-shielded arc welding?

Answer 5

It results in a stronger, more ductile, and more corrosion resistant weld.

Question 6

What shielding gasses are used for gas tungsten arc (TIG) welding?

Answer 6

Helium and argon.

Question 7

What is an advantage of electric arc welding over gas welding?

Answer 7

It causes less buckling and warping of the welded material.

Question 8

What determines the amount of heat that will be applied to the work when welding by the
oxy-acetylene method?

Answer 8

size of tip opening.

Question 9

What is meant by a soft flame?

Answer 9

A soft flame is when the torch is adjusted so the flame makes no noise, and doesn’t push the weld
puddle.

Question 10

When gas welding, what should be turned off first?

Answer 10

First shut off the acetylene, then the oxygen source.

Question 11

What will be the result of using a torch tip that is too large or too small?

Answer 11

If the torch tip is too large, the heat will be too great and holes may be burned in the metal. If the
torch tip is too small, the heat provided may be not enough to produce penetration to the proper
depth causing a low strength weld.

Question 12

How do you determine the correct size filler rod to be used in welding?

Answer 12

The diameter of the rod to be used is governed by the thickness of the metals being joined. Welding
rods are made in standard 36 inch lengths, and in diameters from 1/16 to 3/8 inch. If the rod is too
small, it will not conduct heat away from the puddle rapidly enough, and a burned weld will result. A
filler rod that is too large will cool the puddle too quickly and not allow the proper penetration.

Question 13

What is the function of flux when used in soldering?

Answer 13

Flux erodes corrosion from the surface of the metal when it is heated so the solder can form a
strong bond.

Question 14

Why must acid-core solder never be used on electrical wire?

Answer 14

Any acid flux that is left over will cause severe corrosion to the wire.

Question 15

What is brazing?

Answer 15

Brazing is a metal joining process in which the bonding material is a non-ferrous metal with a
melting point lower than that of the metals being used. It includes silver soldering, copper brazing,
and aluminum brazing. It can be used to join metals that are damaged by high heat.

Question 16

What procedure will control expansion when welding a joint?

Answer 16

By tack welding at intervals along the joint

Question 17

Why is it especially desirable to use a soft flame when welding aluminum?

Answer 17

To avoid blowing holes in the metal when the puddle is formed.

Question 18

What fuel is used for gas welding aluminum?

Answer 18

Oxygen and hydrogen.

Question 19

What is the purpose of using flux when welding aluminum?

Answer 19

Aluminum and its alloys combine with air and form oxides very rapidly, and oxides form doubly fast
if the metal is hot. Aluminum welding flux is designed to remove the aluminum oxide by chemically
combining with it. Aluminum fluxes dissolve below the surface of the puddle and float the oxides to
the surface where they can be removed.

Question 20

What is the maximum safe pressure for acetylene gas when welding?

Answer 20

When acetylene gas is compressed in a container to a pressure greater than 15 psi, it becomes
dangerously unstable. At 29.4 psi, acetylene is self-explosive and only a slight shock can cause it
to ignite.

Question 21

What type of flame should be used when silver soldering?

Answer 21

The flame should be a soft neutral.

Question 22

How can dents at a steel tube cluster joint be repaired.

Answer 22

Weld a specially formed steel patch over the dented area.

Question 23

What are the procedures for preparing a metal fuel tank for welding?

Answer 23

The interior of the tank should be washed with hot water and detergent, and then steamed for a
minimum of thirty minutes. This procedure will vaporize and remove any residual fuel in the tank.
Then fill the tank with CO2 gas from a fire extinguisher and seal the tank except for a small vent hole.

Question 24

When splicing tubing by the inner sleeve method, what method can be used to insert a tight fitting inner sleeve into the replacement tube?

Answer 24

The inner sleeve can be chilled with dry ice or in cold water, and the outer sleeve can be heated.
This will allow for a tighter fit repair.

Question 25

Why is flux used on silver solder?

Answer 25

It cleans the base metal of oxide to ensure a good bond.

Question 26

What are the three general type of welding?

Answer 26

Gas, electric arc, and electric resistance.

Question 27

How is a soft flame obtained without reducing thermal output?

Answer 27

By using a large tip and adjusting the pressures.

Question 28

What valve should be turned off first when extinguishing a torch?

Answer 28

The acetylene to allow gas in the tip to burn out.

Question 29

What must be done with heat-treated aluminum alloys after a welding repair has been made?

Answer 29

They must be reheat treated.

Question 30

What is the preferred method of welding magnesium?

Answer 30

Gas shielded arc welding.

Question 31

What is the most extensively used method of welding aluminum?

Answer 31

Gas shielded arc welding.

Question 32

What safety precaution should be taken when gas welding has been completed?

Answer 32

Turn off the valves and relieve all pressure.

Question 33

What is the result of insufficient penetration?

Answer 33

A low strength weld.

Question 34

What does the size of the torch tip opening determine?

Answer 34

The amount of heat, not the temperature.