Heat Treatment Flashcards
What is Heat affected zone (HAZ)
the area of metal that is not melted but has changed in properties due to exposure to high temperatures during welding
Factors of the Heat Affected Zone
Welding process, type/size of electrode, current settings, travel speed, number of passes, thickness/type of material are all factors of what?
Grain structures
Soild/liquid transition zone, grain growth zone, recrystalized zone and partially transformed zone are all factors of?
How to machine an acceptable heat affected zone
It must be controlled in order to maintain the required mechanical properties
Temperature
Refers to a degree or “intensity” and is expressed in °F or °C.
Heat
Expresses the volume or “quanity” and is measured in British thermal units (BTUs) or in joules.
Heat (joules/BTUs) for Acetylene
Chemical formula: C2H2
54.4 joules/m³
1470 BTUs/m³
Temperature (°C/°F) for Acetylene
Chemical formula: C2H2
°C: 3090
°F: 5600
3 ways for heat transfer
Radiation
Convection
Conduction
What is radiation
Transfer of hear on light waves such as ultraviolet/infrared rays
EX: Arc
What is convention
Transfer of heat from one body to another.
EX: touching a stone top with your hand
What is conduction
Transfer of heat within a body.
EX: touching a stove top with your hand
What is convection
The transfer of heat from one body to another by the movement of a gas or fluid.
EX: hot air rising above a fire.
What metal require more heat input than other steel?
Copper, brass and aluminum
What is expansion?
Metal increasing in size or swelling and is usually associated with a rise in temperature
What is solid expansion
When metal is in a solid condition and has not reached its transition temperature
What is transition expansion
Steel will transition or change from one crystalline form to another.
What is fluid expansion?
Occurs in molten metal
What is free expansion and contraction
Metal to heat up and cool without restraint
What is Restrained expansion and free contraction
Metal is restrained while being heated up and cooled, causing the metal to change in shape when cooled.
