Joining Flashcards
Reasons for joining
Uneconomical/impossible to manufacture in one piece
Less cost to join together, including transportation of parts
Product may need to be taken apart for maintenance etc
Oxyfuel gas welding
Flame produced using fuel gas and oxygen
Filler used to provide extra material at weld zone
Flux generates gas shield around weld zone to prevent oxidation
Thermite welding
Metal melted by an oxidation reaction (usually iron power reacting with aluminum oxide)
Friction welding
Workpieces joined through inertial, linear, or stir friction
Arc welding
Heat generated by electrode arcing to workpiece
Shielded metal arc welding (SMAW/stick welding)
Oldest and simplest welding method
Flux-coated electrode hand-fed towards piece
Good for remote work and thicker materials
Gas metal arc welding (GMAW/MIG)
External source of gas shields weld to prevent oxidation (no flux)
Can be automated, electrode fed via “glue gun”
Flux-core arc welding
Similar to MIG but electrode is flux rod coated in filler metal
Gas tungsten arc welding (GTAW/TIG)
Gas is fed around reusable tungsten electrode
Filler metal is hand-fed towards weld area
Good for precise welds on thin materials
What is the weakest point of a weld?
The area right next to the weld zone, also called the heat-affected area
Plasma arc welding (PAW)
Plasma is concentrated at weld area
Filler is hand-fed like TIG
Good for precise welds
Electron beam welding (EBW)
Fast, concentrated beam of electrons used as heat source
Must be done in near vacuum
Laser beam welding (LBW)
Laser is used as heat source
What kinds of welding are used in space?
Induction and laser welding
Induction welding
Heat generated through resistance created on conductive, magnetic workpiece
Resistance welding
Heat is supplied by electrical resistance between two members
No electrodes, shielding gas, or flux
Zones of a fusion welded joint
Base metal
Heat-affected zone
Fusion zone
Weld defects
Porosity
Slag inclusions
Incomplete fusion
Incomplete penetration
Weld profile
Underfilling
Undercutting
Overlap
Cracks
Distortion
Cold welding
Dies/rolls apply pressure to mating interfaces
Uses plastic deformation to join surfaces
Ultrasonic welding
Static force and oscillating shears applied to mating surfaces
Diffusion bonding welding
Creates strong joints that maintain the properties of the base material
Explosion welding
Layered explosives create high-pressure
Causes mechanical interlocking of the surfaces
Useful for large plates of dissimilar metals
Brazing
Filler metal is melted between mating surfaces but the surfaces themselves remain solid
Soldering
Similar to brazing but at lower temperatures
Results in weaker joints
Filler/flux can be in paste form
Adhesive advantages
Load distribution is even, no localized stresses
Thin/fragile components and porous materials w/ different sizes/properties can be bonded
Does not reach very high temps
Adhesive disadvantages
Can be time-consuming
Surface preparation is critical
Hard to test nondestructively, reliability can be a concern
Riveting
Permanent/semipermanent joint created by deforming rivet into hole
Stapling/Clinching/Stitching
Very fast
Good for thin materials
Seaming
Two thin pieces folded together
Crimping
Done with tubular/flat parts
Squishes things into place
Snap-in fasteners
Cheap
Easy
Good for rapid assembly and disassembly
Advantages of mechanical fastening
Easy disassembly
Can allow for movable/adjustable joints
Cheaper
To create a brazed joint of the same strength as a similar welded joint a larger ____ is required.
weld area
Welding techniques for dissimilar materials
TIG
MIG
Filler rod characteristics for dissimilar materials
Strength of weaker metal
Melting point between materials
Don’t weld these material combinations
Titanium and steel
Aluminum and copper
Aluminum and stainless steel
Aluminum welding processes
TIG
MIG
Cast iron welding processes
Stick
Note: must pretreat before welding
Copper, brass, and alloys welding processes
TIG
Stainless steel welding processes
TIG
MIG
Stick
Steel welding processes
Any
Nickel welding processes
TIG
Titanium welding processes
TIG
Laser
Magnesium welding processes
Laser
Friction stir
Resistance spot
Thermoplastic welding processes
Hot gas
Ultrasonic
