CHEMICAL AND PHYSICAL PROPERTIES, ETC. 221
ite. It is a physical element desirable to exist in_ order to best resist friction surface wear, and is chiefly employed in such castings as rolls, car wheels and crushers, A special article on the "chill" will be found in Chapter LVL
We might say there is chiefly but one carbon in iron, and whether it is combined so as to create a chill,'' or graphitic to make soft or open-grained iron, largely depends upon the time taken for the metal to cool down to solidification, or atmospheric temperature. We can take our softest irons, highest in graphitic carbon, and by pouring when liquid into water cause their carbon to be largely combined in the iron; and then, again, we can take our hardest or *' white '' irons, that are not high in manganese or chromium (qualities seldom to be found in general castings), and by pouring them into massive castings, like heavy anvil blocks, cause their carbon to appear largely of graphite, thus proving that it is chiefly a mechanical or physical condition, and not chemical, that ofttimes can cause iron to be soft or hard, or present peculiarities in its physical qualities.
The above illustration of pouring liquid iron into water and cooling off massive blocks or castings presents the radical extremes of any physical effects. In the rational, common practice of founding, conditions permit the chemical properties to have a control which compels us to recognize them as the chief factor in diminishing or increasing the combined carbon or the hardening qualities of an iron. Nevertheless, a study of what physical effects can produce will prove to many how two castings can often be poured from the same ladle of iron so as to have the same percentages of sili-893, Vol. i, p. 168.ion of manga j: which was added being found in the form of oxide in the so-The philosophical explanation of this extraordinary effect i my opinion, to be found in the fact that the f erro-manganesu .ğR. C. Hindiey, M. Hoskins, Harvard College, Havemeyer University, Henry Hiels Chemical Co., Isabella Furnace, Iron Gate Furnace, Iroquois Iron Co., Illinois Steel Co., Jefferson Iron Co., Kittan-ning Iron & Steel Co., C. A. Kelly Plow Co., Lebanon Furnace, Longdale Iron Co., Lackawanna Iron & Steel Co., Logan Iron........................ 16,720 " t-