Flashcards
Most arc efficient welding process?
SAW
Main limitation of SAW?
Limited to welding in flat and horizontal positions only.
Greatest advantage of SAW?
High productivity rate.
What is twin wire SAW aka Parallel electrode welding?
Two electrode wires are connected parallel to same power source. Fed through single wire feeder and same welding head. Creates deep penetrating weld pool.
What is multiple arc welding aka tandem welding?
Two or more electrodes connected to individual or same power supplies and fed by separate drive rolls through different tips. Lead electrode is DC power, trailing electrode is AC power to reduce interaction of magnetic fields.
Series arc welding is?
Two electrodes through different guide tubes. Separate everything. Current is one electrode to another. Shallow penetration.
Common defect that occurs when using high current DCEP for SAW process?
Solidification cracking.
What current polarity produces highest deposition rate for the SAW process?
DCEN
What current polarity provides better control over bead shape and deeper penetration?
DCEP
Why must fluxes for SAW be handled with care?
When molten, flux is highly conductive (1300C). Provides current path to sustain arc.
What applies to the classification system for SAW consumables?
The wire and flux are designated as a combination.
For SAW, FCAW, and GMAW what does the increase in arc length do?
Increase arc voltage drop across the arc.
What is an effect of switching from straight to reverse polarity with the SAW process?
Penetration is increased.
SMAW process using DCEP will result in maximum heat generated where?
At the cathode.
Melting rate of SMAW electrode is dependent on?
Current, zise of electrode and type of coating.
Components of SMAW:
Constant current supply, electrode holder, and electrical leads.
What happens when a welder using SMAW holds the electrode with the leading angle?
Molten metal and slag will be pushed ahead of the weld.
What is necessary when welding steels contain more than 0.40%C with SMAW?
Preheating and subsequent heat treatment.
What SMAW electrodes may be used for flat and vertical down positions and has powder iron in the coating?
E4948
Third digit is positions: 4= flat and vertical down.
Fourth digit: Electrode covering - 8=basic iron powder.
Hydrogen content of SMAW electrode is measured by?
Measuring gas evolved from welded specimen.
Worm tracks produced by FCAW can be avoided by what with the current and voltage?
Decreasing current and voltage.
FCAW consists of?
Continuous wire and hollow core. Flux is in the core.
FCAW equipment?
Constant voltage power source, constant speed fed wire, control system, welding gun, supply of shielding gas.
FCAW wire that provides best notch toughness?
Indicator that has a G. J for improved notch toughness.
