Steel and Iron 451 



Iron ores are mined chiefly in the Lake Superior region, as in 

 Minnesota, and in the Southern region, as in Alabama. 



Methods of mining depend upon the character and position of the 

 deposits. 



Iron ores with few exceptions are sedimentary in origin. 

 Iron manufacturing centers are located where iron ore, coal, and 

 limerock can be most cheaply brought together and the output con- 

 veniently shipped to market. 



Iron ores are reduced in blast furnaces. The oxygen combines 

 with carbon and goes off as gas ; other impurities melt with lime- 

 rock, forming a slag. The product is pig iron. 



A small part of pig iron is made into wrought iron, about one sixth 

 is used for castings, and the rest for steel. 



Steel is produced from pig iron in several ways. 



The Bessemer process makes rapidly and cheaply a low-grade steel. 



The open-hearth process, slower and better controlled, makes a 

 high-grade steel, from which sulfur and phosphorus are eliminated. 



The duplex process combines the Bessemer and the open-hearth 

 processes. 



The cementation, or crucible, process produces a fine tool steel. 



The electric process produces the highest grades of steel. 



Steel may be tempered, or made to have various degrees of hard- 

 ness, by different rates of cooling. 



Wrought iron, made in puddling furnaces, contains little impurity 

 other than slag. It is made fibrous by rolling. It can be welded but 

 not tempered. 



REVIEW QUESTIONS 



1. Compare the value of the annual production of steel and iron 

 in the United States with the value of all other mineral products. 

 With the value of the metal products. 2. What is the approximate 

 tonnage of iron produced annually in the United States? 3. For what 

 uses is iron indispensable? 4. Mention some of the uses to- which iron 

 is adapted because of each of the following properties : strength, hard- 

 ness, comparative lightness, rigidity, high melting point, magnetism. 

 5. Mention facts to show the wide distribution of iron. 6. Of what 

 are meteorites often composed? 



7. With what three different elements is iron generally combined? 

 8. Mention the chief ores of iron. Which has the highest percentage 

 of oxygen? Which group contains water in its composition? Which 

 is commercially most important? 9. Mention three states in order 

 of their importance in the production of iron ore. 10. Which ore- 



