Although Sweden possesses in its numerous lakes and canals extensive means of water communication, yet owing to the severity of the climate this mode of traflc is necessarily suspended during at least five months in the year. In spite, however, of the manifest advantages of a rapid and uninterrupted means of intercourse, it was not until about twenty years ago that railway communication was first introduced into Sweden. The construction and management of these railways, or at least of the main lines, were undertaken by the government; for it was believed that the amount of traffic in a country so thinly populated would be insufficient to render any private speculation of this kind remunerative. It might bs supposed that a country possessing such vast iron-making resources as Sweden would naturally manufacture its own railway plant. It was soon found, however, that English materials could be obtained for considerably less than the cost of similar articles manufactured at home, and hence Sweden wasf or many years dependent chiefly upon England for its supply of railway materials. Indeed, the Swedish charcoal iron always commanded so high a price in the English market, that it was advantageously exported for the use of the steel manufacturers of Sheflield, while English iron of a lower quality, but suitable for rails, tires, axles, etc., was imported into Sweden; this interchange being facilitated by the free trade enjoyed by that country. After the importation of foreign materials for the construction of railways had continued for about five years, the Swedish Diet called attention to the expediency of using products of home manufacture. As the question was one of great national interest the government was induced to appoint a scientific commission for the purpose of determining whether Swedish raw material was equally suitable for the manufacture of railway plant, and whether its superior quality would adequately compensate for its increased cost. The members of this committee were selected from among the most experienced men of the country, and consisted of Messrs. Ekmann, Styffe, and Grill. The execution of the experiments was confided to Mr. Styffe, who Secured the assistance not only of certain practical engi- The above Is the title of a work, by Knut Styffe, Director of the Koyal TecMilJ]o,i;ricai Inatitnte at Stockholm. Jt hit toeen ti'anlated from thQ SWM)lhi und ilpjiliea Willi in oi'tjjlnul ppeMdL, by OWmer V, dandUafs;, tiMPiKtef at Hutlffay. PJ to me miUU. OdVefntnoi* Md A80e!Rlio at. neers but also of several men of science connected with the University of Upsala. It is an account of these investigationE that forms the subject of the work before us. Experience has taught us the necessity of thoroughly examining the elasticity, extensibihty, and tensile strength of iron and steel intended for the construction of railway plant. In England important investigations on the strength of these metals have been undertaken by Messrs. Fairbairn, Hodgkinson, Kirkaldy, and other engineers. On the continent of Europe experiments on this subject have been ably conducted by several eminent physicists, among whom may be especially mentioned Lagerhjelm, Wertheim, and Kupffer. The Swedish committee in prosecuting their inquiries of course availed themselves of the results of these previous investigations, but extended the methods of experiment to the question immediately under their discussion. Their researches extended over a period of five years, and were prosecuted on account of the Swedish government without any regard to expense; the sole aim being to attain accurate results. Ia the present work the minute details of this important investigation are recorded with admirable fidelity and clearness; but while these details are of the greatest value to the man of science, it should be distinctly understood that it is by no means necessary to study them in order to arrive at the main results of the inquiry. Indeed these results are stated so plainly and succintly as to be understood by any iron-master or practical engineer, while the refinements of the experiments and the investigation of the formule may, if necessary, be omitted without much prejudice to the reader. The materials examined by the committee were obtained from the most renowned iron works of Sweden, and from the chief iron producing districts of England, As noticed in the title of the work, the researches were directed principally to an examination of the elasticity, extensibility, and tensile strength of iron and steel; these properties being regarded as of prime importance in determining the value of railway materials. It is, however, to be regretted that no experiments were made ou the relative capacities of different kinds of iron and steel to resist concussion; for railway materials are, by their nature, constantly exposed to shocks of this kind, and there seems to be a very uncertain relation between the strength of a material to resist tensile strains and to withstand the force of impact; the extensibility or power of extension under a tensile strain is, however, a character more worthy of reliance as a comparative measure between these two properties of the metal. Formerly but little attention was directed to the connection between the chemical composition of iron or steel and its mechanical properties. During the last ten years, however, the subject has recived considerable attention, especially with reference to Bessemer steel; and it is now usual to determine the carbon at most of the European steel works—thanks to the simple coloration test introduced by Prof. Eggertz. In most of the tables appended to this work the author has given the amount of carbon in the bars examined. Considerable attention has also been paid to the influence of phosphorus on iron and steel; and the author remarks that ho knows no instance of a good steel containing more than 0-04 per cent of this element. The effect which slag exerts on iron is also noted, and under certain conditions its preference is said to be beneficial. Not only does the author trace the connection between the chemical composition and the strength of the material, but he also examines the influence exerted by the manipulation to which the material has been subjected. In a valuable series of curves he shows graphically the manner in which the properties of iron and steel are affected by their chemical constitution and mode of manufacture. In examining the results of some of these investigations, the manufacturer will be struck by the results obtained from " Cleveland iron " as compared with Staffordshire iron. These results are certainly not confirmed by general experience, and their explanation is possibly to be found in the author's note (p. 35) in which he tells us that the bars representi ag the Cleveland iron were procured through an agent, and were therefore probably selected. On the other hand, the so-called Staffordshire specimens were purchased in Stockholm, and nothing known as to their manufacture. The author's experiments on hardening tend to corroborate a fact previously known; namely, that iron admits of being hardened, although to a far less extent than steel. When steel is hardened by being plunged into cold water, the scale of oxide formed upon its surface is thrown off, and it may be said that this behavior of the metal constitutes the only practical point of difference by which steel may be distinguished from iron. But perhaps the most important part of Mr. Styffe's work is that which relates to the effect exerted by differences of temperature on the strength o( iron and steel, as detailed m Chapter III. The subject had indeed been previously exam-ined-by Dr. Fairbairn, but in the Swedish experiments a lower limit of temperature was attained, the thermometer falling to the freezing point of mercury, or 40" Fah. In Sweden the difference between the extremes of temperature in summer and winter is twice as great as the corresponding difference in England; and hence materials well suited for use in that climate may be dangerous for a Swedish railway. As the same remark of course applies to other countries that suffer from severity of climate, the subject cannot be too attentively studied by engineers in Canada and certain part of the United States, Tlw gPiW point brcmght out hy Msr, tyfE'* lesoarchee iai the bars of Son and Bt:l tested hf Urn fo? Xenld 59 were actually stronger at low than at ordinary temperatures. Sti'ange as these results may appear, the number of experiments made by the author and the care with which they were conducted, utterly preclude the supposition that any source of error has affected the results. But as the author applies these results to the question of the strength of railway materials in winter, Mr. Sandberg has deemed it necessary to institute experiments on this subject, the results of which are apparently opposed to the conclusion drawn by the author, and are presented in the form of a valuable appendix to this work.; Although the translator, as he admits, adopted a rough and ready method of testing which strikingly contrasts with the refined experiments of the author, he nevertheless has the advantage of experimenting with entire rails such as are really subject to shocks in railway traffic, wliile it must be remembered that the author employed bars so thin as to be little else than stout wires, and which therefore would be : very considerably influenced by any slight irregularity of structure arising from the mode of manufacture. Another source of difference between the results obtained by the translator and those by the author is to be sought in the chemical composition of the bars examined; for while Mr. Sandberg used ordinary rails, which may be supposed to contain a considerable proportion of phosphorus (the Cwm Avon rail, according to the author, contains 0-30 per cent). Mr. Styfife experimented for the most part on comparatively pure materials. But the chief source of discrepancy, doubtless, arose from the different manner in which the strain was applied in the two sets of experiments. The author examined the tensile strength of his samples, and, for this method of testing, his results are doubtless accurate : but the translator subjected his bars to the impact of a falling weight, and thus dealt with forces which are of a more practical nature. It is, therefore, as the translator justly admits, only the conclusions which the author draws from his results that require modification and not the results themselves. To the scientific reader this work will prove an interesting and valuable work. It has received warm commendation from the scientific press of England, and will doubtless be equally well received in this country. The experiments will be of peculiar value to those interested in the manufacture of iron with charcoal and coke. We commend the work as one of much practical and scientific importance, and a valuable addition to the literature of metallurgy.
This article was originally published with the title "The Elasticity, Extensibility, and Tensile Strength of Iron and Steel" in Scientific American 21, 4, 58-59 (July 1869)