STEEL 



5542 



STEEL 



aided in the preparation of an eleven-volume 

 Library of American Literature and edited, 

 with George E. Woodberry, the Works of Ed- 

 gar Allan Poe. 



STEEL, a variety of iron that contains less 

 carbon than cast or pig iron, and more than 

 wrought iron. Steel is superior to other forms 

 of iron for many purposes, since it is more elas- 

 tic, stronger and capable of being tempered 

 to various degrees of hardness. Steel is made 

 by burning the carbon out of pig or cast iron, 

 or by burning carbon into wrought iron. Three 

 varieties of steel are recognized, according to 

 the percentage of carbon in the metal, namely, 

 soft or mild steel, medium steel and hard steel. 

 But steel is generally named after the process 

 of its manufacture. 



Crucible Steel. The finest of steel, such as 

 that used in razor blades and watch springs, is 

 a product of the crucible process. Bars of 

 wrought iron are placed in retorts of clay or 

 graphite with layers of charcoal, and are melted 

 in furnaces. Other ingredients, the chief of 

 which is manganese, are often added. The 

 molten iron takes up a certain portion of car- 

 bon, and when it is allowed to harden in ingots, 

 cast steel is produced. Crucible steel is the 

 highest grade of steel made, and it is used for 

 making tools and in other fine mechanisms. 

 For this reason it is sometimes called tool steel. 



Bessemer Steel. About the middle of the 

 last century Sir Henry Bessemer, an English- 

 man, invented the process which bears his 

 name. Its effect on the production of steel was 

 revolutionary, since it reduced thj cost of 

 manufacture to a figure so low as to extend 

 the use of steel from the production of such 

 small articles as knives, springs, etc., to that of 

 rails and the framework of bridges and build- 

 ings. Bessemer reversed the process described 

 above; instead of adding carbon to wrought 

 iron, Jie burned it out of cast iron. The 

 smelted iron is either used directly from the 

 blast furnaces or is run into converters, which 

 are vessels shaped somewhat like an eggshell 

 and swung on trunnions, so that they may be 

 tipped to a horizontal position for emptying 

 the liquid. Each converter has a capacity of 

 from ten to twenty tons. The lining is of fire 

 brick, about a foot thick. The bottom is 

 pierced by. a number of small holes, through 

 which air is forced from a blast under pressure 

 of 'from ten to thirty pounds to the square inch. 

 The blast burns out the carbon and silicon. 

 When only the desired proportion of carbon 

 remains, a small quantity of an alloy of car- 



bonized iron and manganese is stirred into the 

 fluid, which is then poured into ladles and run 

 into casting molds. The time consumed in the 

 blowing process is from nine to twelve minutes. 



Open-Hearth Steel. This steel takes its 

 name from the fact that the iron is melted in 

 an open-hearth furnace. This furnace resem- 

 bles the puddling furnace used for wrought 

 iron. The material used was originally a charge 

 of pig iron treated with iron ore ; later, pig iron 

 and steel or fragments of wrought iron were 

 melted together. One of the advantages of the 

 open-hearth process is that it provides for the 

 utilization of steel scraps, old rails and frag- 

 ments of wrought iron. 



Most of the steel of commerce is produced 

 either by the Bessemer or by the open-hearth 

 process. Such steel is used for railroad rails, 

 structural material, nails and wire. Steel has 

 taken the place of iron for nearly all structural 

 purposes. 



Alloys. There are nearly as many varieties 

 of steel as there are uses for the valuable ma- 

 terial, and these varieties are formed by mixing 

 a small quantity of some other metal with the 

 steel when it is in a molten state. The metals 

 most used are nickel, manganese, tungsten, 

 uranium and vanadium, each imparting a pe- 

 culiar quality to the steel. Vanadium steel, 

 for instance, has a wonderful power to resist 

 shocks, and it is extensively employed in the 

 manufacture of automobiles. Nickel steel is 

 used in the manufacture of armor plate (see 

 WARSHIP). Tungsten steel is valuable in the 

 manufacture of tools. 



Tempering. When steel is heated and 

 plunged into cold water, it becomes hard 

 enough to cut glass. But the hardest steel is 

 not suitable for tools, and tool steel is put 

 through a process of tempering. This is ac- 

 complished by heating hard steel to a certain 

 temperature and allowing it to cool slowly. 

 The amount of heat determines the temper of 

 the steel. Thus, razor blades are shaped from 

 steel that has been heated to 430 F., whereas 

 sword blades, which require greater elasticity, 

 are produced at a temperature of about 550 F. 



Production. Of the three processes described 

 above, the first produces the finest quality of 

 steel, but the production is relatively small be- 

 cause the demand is light. Bessemer steel for- 

 merly led in the tonnage produced, but the 

 production of open-hearth steel has steadily 

 gained of late and now takes first place. The 

 United States leads the world in steel produc- 

 tion, and in this country the gain of the open- 



