Wire feed welding shielding gases Flashcards
state the primary purpose of a shielding gas
The primary purpose of a shielding gas is to prevent the molten weld metal from absorbing elements from atmospheric air such as oxygen and nitrogen.
when oxygen and nitrogen from the atmosphere become mixed in the molten weld metal, they:
a) increase the tensile strength of the weld metal
b) form harmful oxides and nitrides in the weld metal
c) help increase the ductility of the weld zone.
d) increase the fracture toughness of the weld metal
b) form harmful oxides and nitrides in the weld metal
Which gas is the lightest??
a) hydrogen
b) argon
c) helium
d) oxygen
a) hydrogen
Argon and helium are:
a) reactive gases
b) inert gases
c) ionized gases
d) non-conductive gases
b) inert gases
Where would you use pre argon shielding gas with GMAW
welding non-ferrous materials such as aluminum, magnesium and their alloys.
What is carbon dioxide gas primarily used for?
welding mild and low alloy steels
List three factors to consider when selecting a gas for GMAW
base metal type and thickness filler metal type welding process cost of gas width and depth of penetration desired bead shape importance of spatter and post-weld cleanup joint design and positioning jigging and fixturing type of metal transfer
Is carbon dioxide a monatomic gas or compound gas?
compound gas
A characteristic of carbon dioxide shielding gas used with short-circuiting metal transfer is:
a) a deep, narrow penetration pattern
b) high weld metal loss in the form of spatter
c) excellent surface cleaning action
d) a shallow, wider penetration pattern
b) high weld metal loss in the form of spatter
Which modes of metal transfer are possible with GMAW using 0.9mm (.035”) mild steel wire and carbon dioxide shielding gas?
a) spray and globular
b) globular and short circuiting
c) short circuiting and pulse spray
d) spray and pulse spray
b) globular and short circuiting
The addition of oxygen to argon causes the temperature of the molten metal to:
a) decrease
b) increase
c) stabilize
d) oxidize
b) increase
Compared to Co2, argon is an excellent shielding for GMAW because it promotes the use of:
a) spray metal transfer
b) globular metal transfer
c) short-circuit metal transfer
d) low gas flow rates in globular transfer
a) spray metal transfer
When 1%-9% oxygen is added to argon shielding gas it is to:
a) reduce spatter
b) increase the deposition rate
c) improve wetting action
d) reduce welding costs
c) improve wetting action
Which of the following gas mixes tends to produce low-crowned weld beads on stainless steels?
a) helium-carbon dioxide
b) argon-carbon dioxide
c) nitrogen-carbon dioxide
d) argon - helium -carbon dioxide
d) argon - helium -carbon dioxide
What is an advantage of using a 75% argon + 25% CO2 gas mix on carbon steel?
a) lower cost
b) deeper penetration
c) improved arc characteristics
d) Argon is less dangerous when used in confined spaces
c) improved arc characteristics
Name 4 factors that can influence gas flow rates.
type of shielding gas used type and thickness of the material position of the welding joint design diameter of wire size and shape of gas diffuser and nozzle size of weld pool presence of drafts or air currents design of welding fixtures
Which gas is generally used for shielding when using MCAW?
a) argon only
b) no gas shielding with certain wires
c) oxygen only
d) a mixture of argon and carbon dioxide
a) argon only
The purpose of a flowmeter is to:
a) maintain a constant flow rate of gas
b) maintain a constant pressure of gas
c) maintain a post flow of gas
d) reduce source pressure to working pressure
a) maintain a constant flow rate of gas
The preferred method of measuring shielding gas supply is:
a) kilograms per square centimetre
b) kilograms per minute
c) litres per minute
d) surface metres per minute
c) litres per minute
Flowmeters are calibrated to indicate the:
a) volume of shielding gas supplied
b) capacity of the shielding gas cylinder
c) pressure of shielding gas supplied
d) density of shielding gas supplied
a) volume of shielding gas supplied
What can be done to avoid regular freeze-up when using Co2 gas?
a) lower the gas flow rate
b) increase the working pressure of the regulator
c) cover the regulator body with insulating material
d) install a line heater or manifold system
d) install a line heater or manifold system
What must be considered before using a mini-bulk system?
a) cylinder rental costs
b) frequency of use
c) cannot be used with argon gas
d) availability of an external evaporator unit.
b) frequency of use
