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1、 steel cast iron Fe C In iron-carbon alloys,solid solutions and metallic compounds can be formed due to the different interactions between iron and carbon in solid state Basic phases:ferrite,austenite and cementite Because the iron carbon Because the iron carbon alloy in which the mass alloy in whic
2、h the mass fraction of carbon is more fraction of carbon is more than 5%is brittle and has than 5%is brittle and has no practical value,only feno practical value,only fe-FeFe3 3C is studied in the phase C is studied in the phase diagram of iron carbon alloy,diagram of iron carbon alloy,so the phase
3、diagram of iron so the phase diagram of iron carbon alloy is the phase carbon alloy is the phase diagram of Fediagram of Fe-FeFe3 3C.C.Phase diagram of iron carbon alloy Phase diagram of iron carbon alloy The state diagram is The state diagram is divided into several divided into several regions by
4、some regions by some characteristic points and characteristic points and lines,indicating the lines,indicating the phase composition of phase composition of FeFe-C C alloys with different alloys with different compositions at different compositions at different temperaturestemperatures The meaning o
5、f characteristic points in phase diagram of Fe-C alloy Point A 1538 wc%=0 The melting point of pure iron The meaning of characteristic points in phase diagram of Fe-C alloy Point C 1148 wc%=4.3%eutectic point The meaning of characteristic points in phase diagram of Fe-C alloy Point D 1227 wc%=6.69%T
6、he melting point of cementite The meaning of characteristic points in phase diagram of Fe-C alloy Point E 1148 wc%=2.11%Maximum solubility of carbon in austenite The meaning of characteristic points in phase diagram of Fe-C alloy Point G 912 wc%=0 Isomerization transition point of pure iron The mean
7、ing of characteristic points in phase diagram of Fe-C alloy Point P 727 wc%=0.0218%Maximum solubility of carbon in ferrite The meaning of characteristic points in phase diagram of Fe-C alloy Point S 727 wc%=0.77 eutectoid point The characteristic line of The characteristic line of phase diagram of p
8、hase diagram of FeFe-C C alloy alloy is the connection line of is the connection line of phase transition point of phase transition point of different composition alloy different composition alloy with the same meaningwith the same meaning The meaning of characteristic line in phase diagram of iron-
9、carbon alloy ACD-liquidus AnAn ironiron -carboncarbon alloyalloy ofof anyany compositioncomposition isis inin liquidliquid statestate aboveabove thisthis lineline.TheThe liquidliquid alloyalloy isis slowlyslowly cooledcooled untiluntil ACAC lineline beginsbegins toto precipitateprecipitate austenite
10、austenite andand CDCD lineline beginsbegins toto precipitateprecipitate cementitecementite.AECF-solidus curve It means that the It means that the liquid alloy is slowly liquid alloy is slowly cooled until the line cooled until the line crystallizes into crystallizes into solid phase,and solid phase,
11、and heated until the line heated until the line begins to meltbegins to melt ECF-Eutectic transition line Eutectic reaction Eutectic reaction occurs in all occurs in all fefe-C C alloys with WC%alloys with WC%greater than 2.11%greater than 2.11%when cooled slowly when cooled slowly to the line.to th
12、e line.PSK-Eutectoid transition line It is also known as It is also known as A1 line,indicating A1 line,indicating that all iron carbon that all iron carbon alloy with WC%alloy with WC%greater than 0.0218%greater than 0.0218%will undergo will undergo eutectoid reaction eutectoid reaction and produce
13、 pearlite and produce pearlite when slowly cooled when slowly cooled to this line.to this line.ES线：Acm TheThe solidsolid solutionsolution lineline ofof carboncarbon inin austeniteaustenite isis thethe criticalcritical temperaturetemperature lineline ofof FeFe3 3C C precipitationprecipitation fromfro
14、m austeniteaustenite.PQ SolidSolid solutionsolution lineline ofof carboncarbon inin ferriteferrite GS线：A3 For the For the fefe-c alloy c alloy with WC%less than with WC%less than 0.77%,the beginning 0.77%,the beginning line of ferrite line of ferrite precipitation from precipitation from austenite d
15、uring austenite during slow cooling,or the slow cooling,or the ferrite ferrite transformation from transformation from austenite to end austenite to end line during slow line during slow heating.heating.Phase region of iron carbon alloy Four single-phase regions liquidliquid phasephase regionregion（
16、L L）AusteniticAustenitic phasephase regionregion（A A）FerriteFerrite phasephase regionregion（F F）CementiteCementite faciesfacies areaarea（FeFe3 3C C）Phase region of iron carbon alloy Five biphase regions L+A L+Fe3C A+F A+Fe3C F+Fe3C Phase region of iron carbon alloy A special Zone with three phases The eutectic transition The eutectic transition line ECF and eutectic line ECF and eutectic transition line PSK can be transition line PSK can be regarded as special zones regarded as special zones of threeof three-phase coexistence phase coexistence respectively.respectively.Thanks for watching