MATERIALS 39 



MALLEABLE IRON CASTINGS 



AVERAGE MECHANICAL PROPERTIES 



Tensile strength, lb. per sq. in 54 ,000 



Yield point in tension, lb. per sq. in 36 ,000 



Elongation in 2 in 18 per cent 



Reduction in area (see note 1) 19 per cent 



Modulus of elasticity in tension, lb. per sq. in 25,000,000 



Compressive strength (see note 2) 



Ultimate shearing strength, lb. per sq. in. (see note 3) 48,000 



Yield point in shear, lb. per sq. in 23 ,000 



Modulus of elasticity in shear, lb. per sq. in 12,500,000 



Yield point in torsion, lb. per sq. in 24 ,000 



Modulus of rupture in torsion, lb. per sq. in. 58,000 



Brinell hardness number 100-140 



Charpy impact value, ft. -lb. (see note 4) 16.5 



Wedge test for impact (see note 4) 



Fatigue endurance limit (no definite data, probably about 25,000 to 26,000 



lb. per sq. in.) 

 Effect of temperature (see note 5) 



PHYSICAL CONSTANTS 



Specific gravity 7 . 15-7 . 45 



Shrinkage allowance, in. per ft M~^l6 



Coefficient of thermal expansion per deg. F . 0000066 



Specific heat, c.g.s. units 0. 122 



ELECTRICAL AND MAGNETIC PROPERTIES 



Resistivity, microhms per cc 28-37 



Magnetization properties (see note 6) 

 Magnetic hysteresis (see note 6) 



Notes on Malleable Iron Castings 



1. Reduction of Area.^The elongation usually is spread quite evenly over the entire gage length, instead of being 

 restricted locally. This may be construed to mean that cohesion is more uniform in malleable iron than in other 

 ferrous metals. 



2. Compressive Strength. — In ductile ferrous metals, the yield point in compression so closely approximates that in 

 tension that testing for the latter, being much more easily determined, avoids the necessity of testing for the former. 

 Also, it is impractical to determine the compressive strength of such products, because once the yield point has been 

 passed the specimen flattens out, yielding no well-marked fracture. 



3. Shear and Torsion Tests. — In determining shear by the "direct method," approximate results only can be 

 secured because a certain amount of distortion caused by the combined effect of compression and bending during the 

 test can not be avoided. Consequently, shearing properties are better studied from torsion tests. The number of 

 twists per foot of length will furnish an estimate of the toughness of the material, and their distribution yields some 

 indication of the variation in hardness which tends to cause an uneven localization of the twists, there being less 

 distortion at planes of greater hardness. 



4. The wedge test will furnish a more accurate idea of what can be expected of castings that are to be subjected to 

 shock and occasional overload in service than will a notched bar test, wherein the stresses are concentrated at the root 

 of the notch. 



5. Effect of Temperature. — If malleable iron is heated to a temperature in excess of its critical range, the temper 

 carbon will start to revert back to the combined form, and if heated to around 1600°F. practically all of it wOl be 

 reverted. Malleable iron can be heated to around 800°F. without loss in tensile properties. 



6. Magnetization Properties. — When high permeability is required in iron, the carbctn should be in the form of 

 temper carbon, whereas combined carbon or free cemenite should be absent. Malleable iron possesses high induction 

 and permeability and low hysteresis loss. 



