Mottled cast iron

The result is a hard, abrasion-resistant surface, important in many applications of cast iron. The depth of the chill may be controlled by regulating the amount of tellurium added. The casting shows a sharp demarcation line between the chilled and unchilled regions there is no intermediate or mottled zone. Yet, the chilled portion shows excellent resistance to spalling from thermal or mechanical shock. Tellurium-treated iron is more resistant to sulfuric and hydrochloric acids than is untreated, unchilled gray iron. The amount added ranges from 0.005 to 0.1% ca 60% is lost by volatilization. Excessive addition causes porosity in the castings. 

Founding.—A great quantity of the iron produced by the blast furnaces is used in tho state of cast-iron for a variety of purposes in the arts and manufactures. The qualities employed for this purpose are termed foundry-iron, and include the grey and mottled pig-iron, these kinds being more easily fused than the... 

When the oolor is a uniform dark-grey, tho iron is tough, provided there be also metallic lustre but if there be no metellio lustre, the iron, though Boffc, will be moro easily crumbled than in the former case. The weakest sort of soft cast-iron is where the fracture is of a dark hue, mottled, and does not shine.,... 

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