Welding Flashcards
What is joining vs assembly?
Joining creates a permanant bond, assembly uses some mechanical fastener
What are the faying surfaces?
The two surfaces to be joined.
What needs to be considered when welding different metals?
Differing thermal expansion
Define fusion welding
When the base metals are melted.
Often uses filler material.
Ex. Arc welding, resistance welding, and oxyfuel gas welding
Define solid state welding
Base metals don’t melt: uses temp and pressure, no filler materials
What is diffusion welding?
DFW: Solid state fusion between two surfaces held under pressure
What is friction welding?
FRW: coalescence by heat of friction between surfaces
What is ultrasonic welding?
USW: coalescence by ultrasonic oscillatory motion parallel to contact surfaces held under pressure.
What are the three levels of automation in welding?
Machine - controlled by human
Automatic - equipment performs welding without human
Robotic - Welding implemented by robot
What are the 5 types of weld joints?
Butt Corner Lap Tee Edge
What is a fillet weld?
Fills in the edges of a corner, lap or tee joint. Filler metal provides a triangular cross section. Requires minimum edge preparation, common in arc and oxyfuel welding.
What is a groove weld?
Used when part edges are shaped into some form of groove. Most commonly butt joints. could be V, U, J, square or double-V grooves.
What is a spot weld? Seam weld?
Used for lab joints, to hold two pieces together.
What is power density? What process have high power densities? Low ones?
PD = P/A
Power transmitted to work per unit surface area
High power density allows localized melting.
OFW has low PD because the heat is spread over large area.
AW has high PD.
What are the zones of a typical fusion weld?
The fusion zone is the columnar zone of melted filler, the weld interphase is the seam of coarse grained melted metal, the heat affected zone (HAZ) is the finer grained zone of heated metal, the unaffected zone has original grain structure.
Describe arc welding.
Heat comes from an electric arc between an electrode and the work. Usually adds filler.
The electric arc is sustained by a column of plasma.
What is arc time?
(time arc is on)/(time worked)
Manual welding has a 20% arc time
Machine welding has a 50% arc time
What are the two forms of consumable electrodes?
Rods (must be changed frequently)
Wire (fed in continuously)
What are nonconsumable electrodes made of?
Tungsten
What is arc shielding? How is it done
Protection of the weld from O2, H2, and N2. Uses gasses or flux.
What is flux?
Substance that shields the weld from gasses, and prevents other contaminants from getting into the weld.
It stabilizes the arc and reduces spattering.
What are the different methods of flux application?
Pouring granular flux onto weld
Stick electrode coated with flux that melts
Flux contained in electrode core and released as electrode is consumed
What type of power is better for AW?
DC has better control, but is more expensive.
Describe Shielded Metal Arc Welding.
SMAW: Uses a consumable electrode with a filler rod that provides flux and shielding.
Sometimes called stick welding.
Produces slag.
Used for steels, cast irons, but not for aluminum, copper, or titanium
