Properties and Selection of Engineering Materials Lecture 33 33.1 Fe-C system Steels: with less than 2% C. <a href="/keyword/cast-iron/" >cast iron</a> : with 2-4% C. MatSE 346, Y Q Sun, UIUC, Fall 1999 1 Properties and Selection of Engineering Materials Lecture 33 Types of steel Plain carbon steels: Low (&lt;0.2), medium, high C (&gt;1%) steels. Alloy steels low alloy (&lt;8%) and high alloy steels (&gt;8%). MatSE 346, Y Q Sun, UIUC, Fall 1999 2 Properties and Selection of Engineering Materials Lecture 33 Types of <a href="/keyword/cast-iron/" >cast iron</a> : Gray iron. Gray iron Nodular/ductile iron. White iron. White iron Malleable iron. MatSE 346, Y Q Sun, UIUC, Fall 1999 3 Properties and Selection of Engineering Materials Lecture 33 33.2. Phases in Fe-C system MatSE 346, Y Q Sun, UIUC, Fall 1999 4 Properties and Selection of Engineering Materials Lecture 33 Austenite ( ): high T, ductile, nonmagnetic. Ferrite (): low T, less ductile, magnetic. Carbon rich phase Cementite (Fe3C): aka carbide, brittle, hard, strengthener. Graphite (C): soft, self-lubricant, acoustic damping. MatSE 346, Y Q Sun, UIUC, Fall 1999 5 Properties and Selection of Engineering Materials Lecture 33 33.3 <a href="/keyword/cast-iron/" >cast iron</a> : Fe -2.3-4.3% C MatSE 346, Y Q Sun, UIUC, Fall 1999 6 Properties and Selection of Engineering Materials Lecture 33 Characteristics of <a href="/keyword/cast-iron/" >cast iron</a> Composition near eutectic Low Tm (~1150 C), vs 1500 C for steels At a given T, lower Tm greater fluidity better replication Lower Tm lower processing T lower shrinkage MatSE 346, Y Q Sun, UIUC, Fall 1999 7 Properties and Selection of Engineering Materials Lecture 33 Characteristics of <a href="/keyword/cast-iron/" >cast iron</a> Near eutectic: no mushy state Lower Tm lower processing T less demanding on mold material Lower Tm lower processing T less damage to material, e.g. by oxidation MatSE 346, Y Q Sun, UIUC, Fall 1999 8 Properties and Selection of Engineering Materials Lecture 33 Two carbon-riches phases in <a href="/keyword/cast-iron/" >cast iron</a> : Cementite (Fe3C): hard and brittle compound. An effective strengthener. Forms readily during cooling. Graphite (C): soft, a lubricant, enhances machinability. Slow to form. Formation requires slow cooling rate and addition of graphite-boosters, e.g. Si. MatSE 346, Y Q Sun, UIUC, Fall 1999 9 Properties and Selection of Engineering Materials Lecture 33 Types of <a href="/keyword/cast-iron/" >cast iron</a> : carbide vs graphite Property control/manipulation: controlling the relative fraction of carbide and graphite. MatSE 346, Y Q Sun, UIUC, Fall 1999 10 Properties and Selection of Engineering Materials Lecture 33 33.4 Casting vs machining Large structures MatSE 346, Y Q Sun, UIUC, Fall 1999 11 Properties and Selection of Engineering Materials Lecture 33 Intricate shape MatSE 346, Y Q Sun, UIUC, Fall 1999 12 Properties and Selection of Engineering Materials Lecture 33 Cost effectiveness MatSE 346, Y Q Sun, UIUC, Fall 1999 13 Properties and Selection of Engineering Materials Lecture 33 Competing near net-shape formi...