1.3-Metal enhancement Flashcards
What is work hardening and how is it used to enhance metals
-metal is cold worked by bending, rolling or hammering
-crystals within metal are distorted- leading to improved tensile strength/hardness
-less ductility, cracking or damage
-effects can be removed by annealing
What is annealing and how is it used to enhance metals
-heating work hardened metal and slowly cooling it, making it easier to work as less brittle, more ductile
-metal crystals grow and slowly move into place
What is hardening and how is it used to enhance metals
-medium/high carbon steels heated to alter crystalline structure and quenching (rapid cooling) them
-increase hardness/brittleness
What is tempering and how is it used to enhance metals
-reduces some of the excess hardness and brittleness of a hardened metal
-increases toughness/ductility
-metal heated below critical point then air cooled
-exact temperature=hardness removed
What is the tempering colour
The colour seen on metal that indicates the temperature at which brittleness is removed
What is case hardening and how is it used to enhance metals
-used for hardening the surface of steels with less than 0.4% carbon content
-produces outer casting- greater hardness, improved wear resistance and resistance to surface indentation
What is the process of case hardening
1) caburising- in industry, steel placed in ceramic box so carbon atoms diffuse. Depth ofcarbon layer determined by length of time material exposed to carbon. Longer time=thicker carbon layer
2) quenching
What is carburising in case hardening
This changes the chemical composition of the surface of low carbon steel so that it can absorb more carbon to increase surface hardness
What is quenching in case hardening
This is where the hot metal is quenched in water to fast cool it and seal the hard surface case. Does not affecr inner core propoerties
