438 



NATURE 



[September 4, 1890 



results of a rapidly and dexterously executed series of chemical 

 and mechanical operations. 



The reduction which has been effected in the cost of produc- 

 tion of aluminium through this and other processes, and which 

 has certainly not yet reached its limit, can scarcely fail to lead 

 to applications of the valuable chemical and physical properties 

 of this metal so widespread as to render it as indispensable in 

 industries and the purposes of daily life as those well-known 

 metals which may be termed domestic, even although, and, 

 indeed, for the very reason that, its association with many of 

 these, in small proportion only, may suffice to enhance their 

 valuable properties or to impart to them novel characteristics. 



The Swedish metallurgist, Wittenstrom, appears to have been 

 the first to observe that the addition of small quantities of alu- 

 minium to fused steel and malleable iron had the effect of 

 rendering them more fluid, and, by thus facilitating the escape 

 of entangled gases, of ensuring the production of sound castings 

 without any prejudicial effect upon the quality of the metal. 

 The excellence of the so-called Mitis castings, produced in this 

 way, appears thoroughly established, and the results of recent 

 important experiments seem to be opening up a field for the 

 extensive employment of aluminium in this direction, provided 

 its cost becomes sufficiently reduced. The valuable scientific 

 and practical experiments of W. J. Keep, James Riley, R. 

 Hadfield, Stead, and other talented workers in this country and 

 the United States, are rapidly extending our knowledge in 

 regard to the real effects of aluminium upon steel, and their 

 causes. Thus it appears to be already established that the 

 modifications in some of the physical properties of steel result- 

 ing from the addition of that metal, are not merely ascribable to 

 its actual entrance into the composition of the steel, but are due, 

 in part, to the de-oxidation by aluminium of some proportion of 

 iron-oxide which exists distributed through the metal, and pre- 

 judicially affects its fluidity when melted. In the latter respect, 

 therefore, the influence exerted by aluminium, when introduced 

 in small proportions into malleable iron and steel, appears to be 

 quite analogous to that of phosphorus, silicium, or lead when 

 these are added in small proportions to copper and certain of its 

 alloys, the de-oxidation of which, through the agency of those 

 substances, results in the production of sound castings of in- 

 creased strength and uniformity. It is only when present in 

 small proportion in the finished steel that aluminium increases 

 the breaking strain and elastic limit of the product. 



The influence of aluminium, when used in small proportion, 

 upon the properties of grey and white cast-iron, is also of con- 

 siderable interest, especially its effect in promoting the produc- 

 tion of sound castings, and of modifying the character of white 

 iron in a similar manner to silicium, causing the carbon to be 

 separated in the graphitic form ; with this difference — that the 

 carbon appears to be held in solution until the moment of 

 setting of the liquid metal, when it is instantaneously liberated, 

 with the result that the structure of the cast metal and distribu- 

 tion of the graphite are perfectly uniform throughout. 



The probable beneficial connection of aluminium with the 

 industries of iron and steel naturally directs attention to the 

 great practical importance, in the same direction, which has 

 already been acquired, and promises to be in increasing measure 

 attained, by certain other metals which, for long periods suc- 

 ceeding their discovery, have either been only of purely scien- 

 tific interest and importance, or have acquired practical value in 

 regard to their positions in a few directions quite unconnected 

 with metallurgy. Thus great interest attaches to the influence 

 of the metals manganese, chromium, and tungsten upon the 

 physical properties of steel and iron. 



The name of Mushet is most prominently associated with the 

 history of manganese in its relations to iron and steel. Half a 

 century ago David Mushet carried out very instructive experi- 

 ments on the influence exerted upon the properties of steel by 

 the presence of manganese ; and to Robert Mushet we owe the 

 invaluable experiments leading to his suggestion to use man- 

 ganese in the production of steel by the Bessemer process, which 

 at once smoothed the path to the marvellously rapid and exten- 

 sive development of the applications of steel produced by that 

 classic method, and subsequently by the open-hearth or Siemens- 

 Martin process — a development which has recently received its 

 crowning illustration in the completion of one of the grandest 

 of existing triumphs of engineering science and constructive 

 skill — the Forth Bridge. 



Robert Hadfield has recently contributed importantly to our 

 knowledge of the relations of manganese to iron. His systematic 



NO. IOS8, VOL. 42] 



study of the subject has revealed some very remarkable varia- 

 tions in the physical properties of so-called manganese-steel, 

 according to the proportions of manganese which it contains. 

 Thus, while the existence in steel of proportions ranging from 

 o-i up to about 275 percent, improves its strength and malle- 

 ability, it becomes brittle if that limit is exceeded, the extreme 

 of brittleness being obtained with between 4 and 5 per cent, of 

 manganese ; if, however, the percentage is increased to not less 

 than 7, and up to 20, alloys of remarkable strength and tough- 

 ness are obtained. Castings of high manganese steel, such as 

 wheel-tyres, combine remarkable hardness with toughness. Even 

 if the proportion of manganese is as high as 20 per cent, in a 

 steel containing 2 per cent, of carbon, it can be forged ; whereas 

 it is very difficult to forge a steel of ordinary composition con- 

 taining as much as 275 per cent, of carbon. Another remark- 

 able peculiarity of the high manganese-steel is its behaviour when 

 quenched in water. Instead of the heated metal being hardened 

 and rendered brittle by the sudden cooling, like carbon-steel, its 

 tensile strength and its toughness are increased ; so that water- 

 quenching is really a toughening process, as applied to the 

 manganese-alloy ; and an interesting feature connected with this 

 is that, the colder the bath into which the highly-heated metal 

 is plunged, the tougher is the product. The curious effect of 

 manganese in reducing, and even destroying, the magnetic pro- 

 perties of iron was already noticed by Rinmann nearly 120 years 

 ago ; one result of Hadfield's important labours has been to 

 place in the hands of such eminent physicists as Thomson, John 

 Hopkinson, and Reinold, materials for the attainment of most 

 interesting information respecting the electrical and other physical 

 characteristics of manganese-steel. Hopkinson, from experi- 

 ments with a sample of steel containing 12 per cent, of man- 

 ganese, estimated that not more than 9 out of the 86 per cent, 

 of the iron composing the mass was magnetic, and he considered 

 that the manganese enters into that which must, for magnetic 

 purposes, be regarded as the molecule of iron, completely 

 changing its properties, a fact which must have great signifi- 

 cance in any theory regarding the nature of magnetization. The 

 great hardness of manganese-steel, and the consequent difficulty 

 of dealing with it by means of cutting-tools, constitute at pre- 

 sent the chief impediments to its technical applications in many 

 directions ; but where great accuracy of dimensions is not 

 required, and where great strength is an essential, it is already 

 put to valuable uses. 



The importance of manganese in connection with the metal- 

 lurgy of iron and steel is in a fair way of finding its rival in that 

 of the metal chromium, the employment of which, as an alloy 

 with steel, was first made the subject of experiment in 1821, by 

 Berthier, who was led by the important experiments of Faraday 

 and Stoddart, then just published, to endeavour to alloy 

 chromium with steel, and obtained good results by fusing steel 

 together with a rich alloy of chromium and iron, so as to introduce 

 about 15 per cent, of the former into the metal. Further small 

 experiments were made the year following, by Faraday and 

 Stoddart, in the same direction ; but chrome-steel appears to 

 have been first produced commercially at Brooklyn, N.Y,, 

 sixteen years ago. Ten years later its manufacture had become 

 developed in France, and the varieties of chrome-steel produced 

 in the Loire district now receive important and continually- 

 extending applications, on account of their combining compara- 

 tive hardness with high tenacity, and only little loss in ductility, 

 and of their acquiring great closeness of structure when 

 tempered. 



The influence of chromium upon the character of steel differs 

 in several marked respects from that exercised by manganese ; 

 thus, chrome-steels weld badly, or not at all, whereas manganese- 

 steels weld very readily, and work under the hammer better than 

 ordinary carbon-steel. Again, the remarkable influence of 

 manganese upon the magnetic properties of steel and iron is not 

 shared by chromium. Chrome-steel has for some time been a 

 formidable rival of the very highest qualities of carbon-steel 

 produced for cutting-tools, and of the valuable tungsten-steel 

 which we owe to Robert Mushet. The great hardness, high 

 tenacity, and exceeding closeness of structure possessed by suit- 

 ably-tempered steel containing not more than from i to i 'S per 

 cent, of chromium, and from O'S to i per cent, of carbon, 

 renders this material invaluable for war purposes : cast pro- 

 jectiles, when suitably tempered, have penetrated compound 

 steel and iron plates over nine inches in thickness, such as are 

 used upon armoured ships of war, without even sustaining any 

 important change of form. The proper tempering of these 



