Welding Flashcards
What is the definition of welding?
A joining process in which two or more parts are coalesced at their contacting surface
What is meant by weldment?
The collection of parts joined in the welding process
What is a fillet weld?
Used to fill in the edges of plates.
Filler metal approximate shape of a right triangle.
arc and oxyfuel welding
Requires minimum edge preparation
what is a groove weld?
Usually associated with butt joints
Requires edge preparation to facilitate weld preparation and therefore more expensive
What is fusion in welding?
a source of high density heat energy is supplied to the faying surfaces melting the metal and filler material if used.
Suitable for materials that melt at accessible temperatures
What is meant by power density?
The power transferred to work per unit surface area
P/A
What are some power density considerations?
Too low - melting never occurs heat is conducted
Too high - vaporisation
Describe the 4 zones of a typical fusion weld
Fusion zone
Weld interface (aka. fusion line)
Heat affected zone (HAZ)
Unaffected base metal zone
What are the causes of residual stress
Non-uniform heat flow
Can lead to warping and buckling
Minimised through heat treatments to improve dimensional properties which can be expensive
Describe the dynamics of tensive and compressive stresses
compressive and tensile stresses to create a net force of zero.
Tensile stresses typically exist at and near the weld. Compressive stresses are found in the surrounding base metal.
How can you minimise distortion?
Heat sinks to rapidly remove heat
Preheating base parts to reduce deltaT
Proper joint design
Stress relief heat treatment
What are the main types of fusion welding?
Arc welding
Resistance welding
Oxyfuel gas welding
What is meant by arc welding?
Uses an electrical arc to produce heat and melt the metal
Usually filler metal used to strengthen joint
What is an arc?
A discharge of electric current (flow of electrons) across a gap in a circuit.
Sustained by the presence of a thermally ionised column of gas
What are consumable electrodes?
Provide the source of the filler metal in arc welding. Available as rods( also called sticks) and wire.
