Stainless steel + wrought alloys BDS3
No description yet. This curated deck is ready for daily study.
Card preview (24)
What are wrought alloys
Manipulated/shaped by cold working -used for ortho/RPD clasps
What is steel made of
Iron > 98% Carbon < 2%
What is iron with more than 2% carbon
Cast iron/pig iron
What does allotropic mean
Undergoes 2 solid state phase changes with temperature
What are the 2 structures iron goes through
FCC - lattice (higher C solubility) BCC - lattice structure (low C solubility)
What are the phases of Iron - Carbon
Austenite - interstitial solid solution (FCC) exists at high temp (>720) Ferrite - very dilute solid solution, exists at low temp Cementite - Fe3C, exists at low temp Pearlite - eutectoid mixture of ferrite and cemintite
At what phaseddoes Fe3C exist
Cementite
What is an alloy
Two metals that form a common lattice structure, are soluble in one another and form a solid solution
What does quenching austenite create
Martensite
What are the features of martensite
No time for diffusion of carbon Distorted lattice Hard, brittle
What is the difference between the slow and fast cooling our austenite
Slow - Pearlite (ferrite, cementite) Fast - Martensite (distorted lattice, hard, brittle)
How can martensite be converted to pearlite
Tempering
What is stainless steel made of
Fe C Cr Ni
What determines whether it is stainless steel
> 12 % Cr -lowers % carbon at which eutectoid formed
What makes stainless stell corrosion resistant
Chromium oxide layer
What does the addition of nickel do
Improves fracture strength Improves corrosion resistance Lowers austenite to martensite transition temp
What are the types of stainless steel
Martensitic Austenitic
What is martensitic stainless steel
12-13% chromium + little carbon Heat hardenable Dental instruments
What are dental instruments made of
Martensitic stainless steel
What is austenitic stainless steel used for
Dental equipement and instrument to be sterilised NOT cutting edge Corrosion resistant Orthodontics/sheet forms for denture bases
What is 18-8 stainless steel and its properties
18%Cr 8%Ni 0.1%C 74%Fe Does not heat harden Soft when cast Work hardens rapidly
What is 18-8 stainless steel used for
Ortho RPD
What is springiness (YM)
Ability of a material to undergo large deflections (to form arc) without permanent deformation (ie it returns to its original shape)
What are the required properties of wires
High springiness Stiffness High ductility Easily joined Corrosion resistant