Page:The New International Encyclopædia 1st ed. v. 10.djvu/889

IRON AND STEEL. the silicon element of iron and steel is to increase the strength and soundness of steel and the fluidity of cast iron, and to reduce the ductility of steel. Manganese has the effect of counteracting the injurious effects of sulphur, phosphorus, and some other impurities, and increases hardness, fluidity, elasticity, and strength. Sulphur and phosphorus are nearly unmixed evils in iron and steel, and every effort is made to remove them from these metals.

The effect of none of these elements upon the metal is independent, but is influenced by the presence of one or more of the others. These interactions are too complicated to be discussed outside of special technical treatises. The effect of treatment during working upon the physical properties of iron and steel are numerous, and are referred to in the articles on ; .

Turning now to the physical properties of the several classes of iron and steel mentioned above, it may be noted, first, that strength may be subdivided into strength against rupture by direct pull, or tensile strength; strength against rupture by compression, or compressive strength; strength against rupture by bending, or flexural strength; and strength against shear, or shearing strength. (For the methods of measuring these various forms of strength, see .) Hardness is the capacity to resist indentation; weldability is the property which permits two or more separate fragments to be welded together; ductility is the property which renders the metal capable of being drawn out into rods or wire; malleability is the property which permits the metal to be hammered or pressed into different shapes; elasticity is the property which gives the metal power to return to its original form after distortion; and homogeneity is the property which secures uniformity of structure and mass.

Cast iron cannot be welded like wrought iron, and its malleability and ductility are practically nil; its tensile strength is from 15,000 pounds to 35,000 pounds per square inch; its compressive strength is from 60,000 pounds to 200,000 pounds per square inch; its flexural strength is from one-half to two-thirds its tensile strength; its elasticity is small. Wrought iron is malleable, can be forged and welded, and has a high capacity to withstand the action of shocks; it cannot be tempered, and melts only at the highest temperatures. Its tensile and compressive strengths are closely equal, and range from 50,000 pounds to 60,000 pounds per square inch; it is tough and ductile. The physical properties of steel depend upon the chemical composition and method of manufacture, and they vary so greatly, both relatively and absolutely, that no effort will be made to define them here. The mild and soft structural steels for bridges and buildings have

tensile strengths of from 60,000 pounds to 70,000 pounds per square inch, with a limit of elasticity of from 30,000 pounds to 40,000 pounds per square inch. The hard steels have a much greater strength. The compressive strength of steel is always greater than the tensile strength.

The uses to which iron and steel are put are so familiar that only brief mention need be made of them. Cast iron is used chiefly in founding or iron-casting, the varieties and purposes of such castings being almost innumerable. Cast steel is used for many of the same purposes as cast iron, but more particularly for those purposes where castings of great strength are required. Wrought iron is forged into various shapes for special purposes, and is rolled into bars, plates, beams, rails, and structural shapes. Extra hard steels are used for tools, hard steel for piston-rods and other parts of machines, medium steel for rails and guns, and the mild and soft steels for beams and structural purposes.

The following table, rearranged from statistics published in The Mineral Industry (New York) for 1901, shows the production of iron and steel in the principal countries of the world for the twelve months of 1900: As will be noted, the three great iron and steel producing countries of the world are Germany, the United Kingdom, and the United States.

Taking up the figures for the United States in somewhat more detail, we have the following, showing the relative output of the different classes of steel and iron:

The principal pig-iron producing States of the United States in 1901 were: Alabama, 1,225,212 tons; Illinois, 1,596,850 tons; Ohio, 3,926,425 tons; and Pennsylvania, 7,343,257 tons.

For a comprehensive discussion of the metallurgy of iron and steel, consult: Howe, Metallurgy of Steel (New York, 1890); Campbell, The Manufacture and Properties of Structural Steel (New York, 1896); and Turner, The Metallurgy of Iron (London, 1895). For details of the manufacture of iron and steel into