MATERIALS 35 



CAST IRONS 



GRAY IRON 



Per Cent 



Chemical Composition by Weight 



Graphitic carbon 2 -3 



Combined carbon 0.8 max. 



Iron 93.7 -94.3 



Silicon 0.25-0.3 



Manganese. : 0.5 - 1 



Sulphur 0.07- 0.12 



Phosphorus 0. 10- 1.05 



Average Physical Properties Lb. per Sq. In. 



Tensile strength 21,000- 42,000 



Shear strength 36,000- 60,000 



Compressive strength 70,000-200,000 



Modulus of elasticity 15,000,000 



Gray iron ordinarily is easily machinable. 



WHITE IRON 



Per Cent 

 Chemical Composition by Weight 



Graphitic carbon Trace 



Combined carbon 3 . 30 



Iron...... 94.93 



Silicon 0.60 



Manganese . 52 



Sulphur 0.15 



Phosphorus 0. 50 



Average Physical Properties Lb. per Sq. In. 



Tensile strength 20,000-70,000 



Modulus of elasticity 20 ,000 ,000 



White iron is difficult to machine. When not heat-treated, white iron has great 

 resistance to wear bj^ abrasion. 



MOTTLED IRON 



Per Cent 

 Chemical Composition by Weight 



Graphitic carbon 1 . 50 



Combined carbon 1 . 80 



Iron 95.07 



Silicon 0.92 



Manganese . 36 



Sulphur 0. 13 



Phosphorus 0. 22 



Mottled iron is a mixture of gray iron and white iron. 



ChUled cast iron are those parts of castings which after pouring are cooled 

 quickly by chills in order to retain the carbon in the iron carbide form found in white 

 iron, whereas other parts of the casting cool slowly to form gray iron. 



