GMAW And FCAW Flashcards
A metal transfer mode in which molten metal from consumable welding wire is deposited during repeated short circuits. The number of these short circuits can occur up to 200 times per second.
Short circuit transfer (GMAW-S)
Occurs when the wire feed speed and voltage are increased above the upper range for GMAW-S. The transfer of the molten metal in large droplets from the welding wire across an arc to the workpiece. Occurs at the rate of a few droplets per second.
Globular Transfer.
Metal transfer mode in which welding wire is propelled axially across the arc. The arc is a steady, quiet column with a well-defined, narrow, cone-shaped core in which metal transfer takes place.
Spray transfer
Type of GMAW metal transfer that is limited to welding thicker materials in the 1G, 1F and 2F positions.
SPRAY TRANSFER
The modes of metal transfer for GMAW are:
Short-circuiting transfer
Globular transfer
Spray transfer
GMAW modes of transfer are determined by a number of factors:
Electrode diameter
Electrode extension
Shielding gas composition
Mode of GMAW metal transfer suited for the joining of thin sections, out of position welding and bridging root openings.
Short-circuit transfer
In short-circuit mode, the shielding gas that produces the highest spatter.
Pure CO2
Advantages of spray transfer compared to other modes of transfer:
Increased rates of deposition and minimum post weld clean-up
Although first introduced in the 1920s, GMAW did not become commercially available until 1948
T/F
TRUE
GMAW was primarily first used for welding:
Aluminum
GMAW is used to weld:
Pipe
Pressure vessels
Structural steel
Metals that can be welded with GMAW include:
Carbon steel
High-strength low-alloy steel
Stainless steel
Aluminum and Copper
Important advantages associated with GMAW are:
An efficient consumable-electrode process that can be used to weld all commercial and can also be performed in all positions.
Limitations associated with GMAW include:
Complex, costly equipment to operate the process and can be performed in windy conditions.
GMAW was 1st called MIG as a result of:
Metal inert gas, using an inert gas for arc shielding
Because of it versatility, GMAW has become more widely used and has replaced ________ for many applications.
SMAW
The manufacturer describes their aluminum electrode process of:
Continuous casting
Drawing and testing the wire
Controlling alloys
According to the article, most aluminum MIG welding problems are caused by:
Poor feeding
Aluminum did not become available in commercial quantities until the discovery of the _________ __________ for obtaining pure aluminum from aluminum oxide in 1886.
Electrolytic processes
The characteristics of aluminum alloys which make them attractive as structural materials are their:
Light weight
Relatively high strength
Aluminum can be alloyed with a number of different elements, both primary and secondary, to provide:
General weldability
Improved strength
Corrosion resistance
Some primary elements that alloy with aluminum are:
Copper and Zinc
A piece of 6061:
Contains magnesium and silicon
Is wrought alloy (4 digits)
Is heat treatable
The 6XXX series is prone to hot cracking, but this problem can be overcome by the. Correct choice of:
Joint and filler metal
In heat-treatable aluminum alloys:
The weld will generally be weaker than the parent material.
Most common aluminum filler alloys fall into the:
4XXX and 5XXX families
ER4043 filler wire has a silicone percentage of:
4.5-6.0
Oxides on aluminum plate can be removed by:
Power wire brushing
Sanding
Grinding or chemical etching
All of these
Common weld preparation techniques for aluminum include:
Sawing and shearing
Grinding and sanding
Machining
The recommended shielding gas for welding aluminum up to approximately 1/2” (12.7 mm) in thickness is:
100% Argon
Small changes in wire diameter, wire feed speed, and current produce ____________ changes in weld bead profile, arc length and can even cause equipment ____________ due to wire burn back and fusing tip.
Heat-Treatable
Non Heat treatable
With the no heat-treatable alloys it is possible to increase strength only through ___________ ____________ or ______________ _____________.
Cold working
Strain hardened
__________ __________ and _____________ ____________ are the two recommended GMAW modes of metal transfer for aluminum.
Axial spray
Pulsed spray
The formation of black soot on the surface, or the adjacent areas of a weld, is referred to as smut. It is made up of finely divided oxides of aluminum and magnesium. They usually indicate that _____________ in _____________ are necessary.
Adjustments
Technique
GMAW electrode specs
E R 7 0 S - 6
What does the following mean?
E... R... 70... S... 6...
Electrode Rod (may be omitted) Tensile strength Solid wire Indicates the filler metal composition
Definition of Electrode Extension…
Is the distance from the contact tip to the end of the welding wire.
modes of metal transfer…
Short circuiting transfer
Globular transfer
Spray transfer
- as well as a variation of spray transfer called pulsed spray transfer
Definition of metal transfer…
Is the manner in which molten metal transfers from the end of the electrode across the welding arc to the weld pool
Define GMAW…
Gas metal arc welding Is an arc welding process that uses an arc between a continuous ire electrode and the weld pool.
GMAW welds can be applied by the…
Semiautomatic - wfs, voltage setting and gas flow rate are preset but welding gun is manually operated.
Mechanized - operator sets welding parameters and monitors welding operation while a mechanical device controls the welding gun
Automatic - welding parameters and welding gun movements are programmed into a computer and all aspects of the process are controlled by equipment
GMAW produces…
On what metals?
Cost effective?
High quality welds on a variety of ferrous and nonferrous metals at low cost
GMAW welds are _________-___________. Therefore there is very minimal, if any, post weld clean up
Slag free
GMAW process allows…
Higher deposition rates
Faster travel speeds
Less electrode waste
Easier than manual welding processes like
- SMAW, OAW, GTAWGMAW disadvantages…
- won’t function in windy environment (outside)
- Required careful setting of electrical components
- not very portable
- cost is high due to many parts
- need clean base metal
- potential for cold lap and undercut
- skill
- high radiated heat
The most common current selected for GMAW Is…
Direct current electrode positive (DCEP)
DCEP is the most efficient current because…
It produces deeper penetration
Greater surface cleaning
In GMAW, current is a function of…
Wire feed speed
What current should NOT be used for GMAW? Why?
DCEN And AC
Because weld penetration is shallow and wide, there’s excessive spatter and no surface cleaning occurs.
GMAW uses __________ ____________ welding power source capable of producing ___________ ___________
Direct current
Constant voltage (CV)
CV welding power sources are also known as…
Constant potential (CP) machines
Generally, electrode classifications for GMAW are interchangeable with electrode number classifications for GTAW
T/F
False
In the electrode number ER70S-4, the 4 indicate the filler metal composition and welds mechanical properties.
T/f
True
In the GMAW electrode classification system, the R stands for “rod out to length” and may be omitted.
T/f
True
ER90S-2
The electrode tensile strength is
90k
