Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/298

282 IRON guishing between malleable iron when hard and steel when soft, there is no difficulty in tabulating the essential differences between good malleable iron, well-marked steel, and cast iron. Thus the following table may be drawn up: Chemical Malleable Iron. Steel. Cast Iron. Composition. Carbon traces to 0-3 or 4 04 to 1-8 2-0 and upwards Silicon to 0-2 to 0-4 O l to 3-0 Sulphur to 0-1 to O l traces to 5 Oxygen ? ? 9 Phosphorus to 0-5 to 0-3 traces to 2 i to 0-2 in cementation | Manganese . traces -c steel. 0-2 to 2-0 and upwards in >- traces to 2-0 ( Bessemer s metal, &c. I Iron 90 to 99-5 97-0 to 99-5 90-0 to 97-0 ( Almost pure More or less pure iron, Usually consid iron, containing containing from 0-4 to erably impure very little if any 1 8 per cent, of carbon. iron, containing impurity other and as a rule not more upwards of 2-0 per than carbon, this than traces of other sub cent, of carbon, not exceeding a stances (manganese ex- and varying but Essential few tenths per cent. Sometimes cepted, and in certain special qualities phos usually notable amounts of sul composi- contains percep phorus and silicon), phur, silicon, tiou tible amounts of manganese being pre phosphorus, &c. imperfectly re sent only in minute moved slag, vary quantity in cementation ing from 01 to 3-0 steel, in larger amounts per cent. in the products of Bes semer s process and cer tain other methods. 1 Welds readily ; Can be welded with Will not weld; is comparatively more or less difficulty, is comparatively soft and very diffi according to the amount readily fusible cultly fusible; will of carbon present ; less and easily cast ; not harden ; of infusible than malleable will not harden fibrous texture; iron, the melting point like steel ; far when well made being lower the more more brittle than Physical very tough and tenacious. The carbon is present; can be hardened snd anneal tempered steel or malleable iron, character- limit at which the ed and will bear a cut but still possessed istics capability of har ting edge ; is very tough of considerable dening is first and elastic when of good strength, espe noticeable as re quality, much more so cially as regards gards carbon per than malleable iron. crushing strain ; centage is near to Texture granular, fine crystalline or 0-3-5 per cent. granular, or slightly fib granular texture. rous, according to quality I and mode of preparation. The following tables express the results of Karsten, Eggertz, and Siemens as regards the limiting amounts of carbon present in soft iron, steel, and cast iron respectively : Karsten. Carbon percentage. Character of Metal. Physical properties. A.OS: j Malleable Mot capable of being perceptibly hardened by U 2d ( iron. sudden cooling. 35 Steely iron. Just capable of being slightly hardened. 0-50 Stc.l. | Will harden, and give sparks with a flint when hardened. to 1-5 Dr>. Best proportion for tenacity and hardness. 1 75 Do. Limit of power of welding properly. 1-8 Do. Very hard cast steel ; cannot be forged easily. 1-9 Do. Not malleable at all when hot. 2 and up wards. cast iron. Brittle ; will not bear hammering. 5-0 to 6-0 Do. -j Highest percentage of carbon obtainable in white irons and spiegeleisens, <fee. C. trbon percentage. Nature of Metal. 0-08 Softest Swedish Bessemer iron. 0-75 Soft steel. 1-4 to 1-5 Best kinds of cast steel. 0-99 to 2-44 Forge steel. 0-5 to 1-9 Cement steel. 0-86 to 1-94 Cast steel. 1 80 Hardest cast steel that can be welded. 0-SS to 1-52 Malleable cast iron. 3-30 Draw plat steel. Carbon percentage. Character of Metal. Up to 0-3 -j Above 1-4 When cast is homogeneous melted iron rather than true steel, being no longer capable of being hardened. Xo longer capable of taking a temper, and consequently rather approaching to cast iron in character than to steel. Akermann classifies commercial iron and steel as follows : Not Malleable. Cast or pig iron. Malleable. Malleable cast iron, made by decarbonizing pig iron by cementation with oxide of iron. Cementation steel (blister steel), made by carbonizing piled bloom or ingot iron by cementation with carbon. ( Designated as " Bessemer," "Martin," "crucible," &c., ac cording as it is made. Martin and crucible steel can also be made from malleable cast iron, blister steel, ingot, bloom, or j piled iron or steel, or a mixture [ with or without pig iron. f Called by the extra name Bloom iron. Ingot metal (Got mctall). Made thoroughly fluid by heat, or molten. Ingot iron. Ingot steel. Bloom metal (Smalt metall). Piled metal (Garf metall). Made in open hearths from iron ore or pig iron. Made by the welding together of unmelted particles. Bloom stoel. Piled iron. Piled steel. of " Catalan," " Lancashire," " Franche Comte"," &c., accord ing to the description of hearth in which it is made. Can be made by welding the spongy iron reduced from iron ore, or, as is more often the case, by puddling pig iron, when it has the extra name of " puddled iron " or " puddled steel." The following recommendations as to tlie nomenclature of iron and steel were made by an international committee appointed at Philadelphia in the year 1876 by the American Institute of Mining Engineers, consisting of I. L. Bel!, Dr H. Wedding, Professors Tinnier and Akermann, L. Griiner, A. L. Holley, and T. Egleston : 1. That all malleable compounds of iron, with its ordinary ingredients, which are aggregated from pasty masses or from piles or from any form of iron not in a. fluid state, and which will not sensibly harden and temper, and which generally resemble what is called wrought iron, shall be called weld iron (Ger man, Schtceisseisen ; French, fer soude). 2. That such compounds, when they will from any cause harden and temper, and which resemble what is now called "puddled steel," shall be called weld steel (German, Schictissftahl ; French, acier soude). 3. That all compounds of iron, with its ordinary ingredients, which have been cast from a fluid state into malleable masses, and which will not sensibly harden by being quenched with water while at a red heat, shall be called ingot iron (German, Flusseisen; French, fer fond u). 4. That all such compounds, when they shall from any cause so harden, shall be called ingot steel (German, Flvssstahl ; French, acier fondu). Siemens (Lecture to Chemical Society, Journal Chem. Soc., 1868, p. 284) lays down the aphorism that "no method of producing steel can be considered admissible at the present day which does not pass the metal through the condition of entire liquefaction, for it is only by fusion that foreign admixtures can be thoroughly separated, and that flaws and fissures can be avoided ; " which appears to imply that no substance that has not been completely fused should be termed a true steel even though it be susceptible of hardening. Nine years later (Presidential Address to the Iron and Steel Institute, 1877), in discussing the above proposed de finitions of the international committee, he remarks that practical difficulties would be introduced by these definitions ; for instance, railway bars, which ordinarily contain from 2 to - 6 per cet. of carbon, would sometimes be stamped as ingot iron and sometimes as ingot steel ; and he further objects that, unless the precise tem perature to which the metal is to be heated in order to harden it is specified, and also the cooling medium into which it is plunged, discrepancies will be introduced between the results of tests of the same metal by different experimenters, certain conditions of tempera ture and cooling material enabling particular classes of metal to take a slight temper, the which substances would not be hardened by the use of lower temperatures or different cooling materials, e.g., oil in lieu of water or msrcury. In view of the difficulty experienced in defining precisely what is meant at the present day by the terms iron and steel, and the practical inconveniences and litigation thereby brought about, it has been proposed by Sir Joseph Whitworth and others to disuse the terms "iron" and "steel" as distinctive marks of quality, and instead to define the metal in terms of its tensile strength and ductility (percentage elongation before rupture). The following table illustrates such a "scale" of qualities, being one employed at Seraing 1 for " steels " prepared by fusion processes : i Recently a slightly different classification of the Seraing steels (Societe John docket-ill) has been adopted (Annales Industrie/let, August, 1870), viz. :- Class. Character. Content of Carbon per cent. Tensile -trength in tons. Ex cnsion in 8 inches per cent. Welding and Tempering Properties. 1 3 4 Extra mild.. Mild 0-05 to 0-20 0-20 ,, 0-3.-. 0-35 0-50 OT.O ,, 0-C5 25 to 32 32 ,, 38 38 ,, 4G 46 51 20 to 27 15 ,, 20-| 15 ,, 20 < ...| Welds, but does not temper. Welds but badly, but may be very slightly tempered. Does not weld, but will temper. Unweldable, but may be strongly tempered. Hard Extra hard