Fe-C phase diagram

Question 1

for which % of C the diagram has practical interest

Answer 1

up to 6.70%

Question 2

write these phases corrisponding corstituent

-Fe-alpha
-Fe-gamma
-Fe-delta
-liquid
-Fe3C
-Fe-gamma + Fe3C
-Fe-alpha+ Fe3C

Answer 2

-alpha-ferrite
-gamma-austenite
-delta-ferrite
-liquid
-cementite (I,II,III)
-ledeburite
-transformed ledeburite / pearlite

Question 3

what’s the name of the left and right part of the diagram wrt 4.3%c

Answer 3

left=hypo-eutectic
right=hyper-eutectic

Question 4

what are on the diagram A1, A3, A4, Acm

Answer 4

critical transformation temperatures

Question 5

3 main stages of an heat treatment

Answer 5

heating
holding
cooling

Question 6

3 types of thermal treatements seen at lesson

Answer 6

annealing
normalizing
quenching

Question 7

describe annealing

Answer 7

-Heating and holding at TAUST = A3 + 40°C
-very slow cooling down
-achieve conditions very close to equilibrium
-Very long treatment time (cost !!)

Question 8

describe normalizing

Answer 8

-Heating and holding at TAUST = A3 + 70°C
-air cooling
-properties close to annealing in shorter times

Question 9

describe quenching

Answer 9

-Heating and holding at TAUST = A3 + 50-70°C
-rapid cooling
-promote transformation into martensite

Question 10

describe tempering

Answer 10

-fresh martensite is too hard and brittle
-by tempering it becomes more ductile (still hard)
-done by heating and holding at T< A1
cooling conditions not important