62 



NATURE 



[November 9, 191 1 



THE PRESENT POSITION OF ELECTRIC ] 

 STEEL-MELTING.^ | 



'T'HE melting of steel by means of electricity has passed I 

 -*■ the merely experimental stage and become one of the | 

 commercial processes by means of which steel is manu- 

 factured for the market. It is not correct to say that it 

 has emerged from the experimental stage, however, as 

 not only this process of steel-making, but most other pro- 

 cesses, are being continually experimented with and the 

 results compared with one another by up-to-date and 

 vigorous firms, not only for the new conditions that are 

 always arising, but also for old and well-tried conditions. 



A new demand arises or repeat orders come in, and the 

 manufacturer must ask himself what kind of steel will 

 best suit the purpose at the present time. Will Bessemer 

 or open-hearth steel be most suitable to satisfy the demand, 

 price, quality, and all other matters considered, and must 

 it be acid steel or will basic do, or is it necessary or 

 desirable to use crucible steel, or perhaps this new electric 

 steel, to maintain or increase his profit or his reputation 

 for certain goods? These are problems of daily occur- 

 rence ; and although the difficulties of the manufacture of 

 electric steel by various processes have been fairly well 

 overcome, so far as making it to specification of chemical 

 composition and mechanical tests is concerned, it is in 

 connection with such questions as are indicated in the 

 previous sentence that it is still in the earlier experimental 

 stage. All other processes, however, are more or less 

 under such trials until they become extinct. The point 

 need not be laboured, for many examples will come to the 

 mind at once, such as the comparative merits for various 

 purposes of Swedish-Lancashire and Walloon iron, of mild 

 steel and wrought iron, of acid and basic steel, and so on. 

 The general impression gathered from much conversation 

 with users is that the arc-furnace product from slightly 

 impure materials, purified to Swedish standard, just about 

 takes its place by Swedish open-hearth and Bessemer steels, 

 and that the induction-furnace product skilfully made from 

 pure materials equals anything but the very highest quali- 

 ties of crucible steels. These are very general statements, 

 but they represent the writer's present more or less 

 intuitive opinions, and only time can determine whether 

 thoy are correct ; for the fact that steels are of certain 

 chemical compositions and give certain mechanical tests 

 is not a final judgment, but the quality and length of 

 service given in actual use. The special feature of the 

 H6roult and Rochling-Rodenhauser types is that with an 

 oxidising purification phosphorus can be eliminated to 

 almost any extent that will pay, and after removing the 

 slag, and forming another, by a reducing purification 

 sulphur can similarly be removed. 



The Kjellin induction furnace acts as a melter of 

 materials much after the manner of the crucible, and has 

 one advantage over the crucible in that there is no absorp- 

 tion of sulphur during melting. Recent experiments with 

 covering slags specially calculated by the writer to give a 

 minimum of change in composition during melting show, 

 according to a student's preliminary analysis, compositions 

 in the ingots practically equal to those by calculation from 

 the constituents, a result better than expected, but still 

 requiring thorough checking. The results at least serve 

 as a text for one fact that must never be forgotten. The 

 electric furnace, of whatever design, will not make good 

 steel automatically. The same metallurgical skill required 

 by the older processes must be expended on the proper 

 killing and finishing of the steel bv whatever type of 

 electric furnace it is being melted, and the fact that in 

 electric as in other furnaces bad steel mav be made from 

 good materials increases the diflRculties of finding the exact 

 place of any steel in the world's work. Several cases 

 where the electric steel has been found unsuitable, especi- 

 ally in the earlier days, have been investigated, and it has 

 been found that the steel has been wronglv made. In 

 other cases no such explanation could be given. Recentlv 

 1 had a long talk with a man using large quantities of 

 electric steel ; he could get great purity, but no better 

 mechanical tests; yet he found the electric steel gave a 

 better life than his former steel, and so he used it. Here 



1 Report pre<:ented at the P-rt«-«outh meeting of the British .\»';ociation 

 (Section B) by Prof. Andrew McWilliam. 



NO. 2193, VOL. 88"! 



again another difficulty comes in as represented by tli' 

 fact that I did not think his ordinary steel was sperial' 

 well made. 



One point of importance is that this product!' 

 electric steel has introduced a new competitor into tli' 

 by giving great impf;tus to the use of what is sonf 

 called white coal, namely, the great waterfalls, mosih ;. 

 removed from coal ; and much energy is now being us< 

 that formerly ran to waste, whilst tifie successful applic:i 

 tion of electric power to the production of charcoal pig-j 

 iron allows of a much reduced consumption of charcoal.. 

 The rapidly increasing price of charcoal in Sweden, owin( 

 among other causes, to so much of the wood being us 

 for making wood pulp for paper-making, is quite a seric 

 situation, which this application of electric power may help] 

 to relieve. 



The whole subject of electric iron-smelting and electri 

 steel-melting is attracting much attention. Several bool 

 have been published on electric furnaces ; and during if 

 and 1910 many interesting articles on the subject ha« 

 appeared in the technical journals, and many papers hav4 

 been read before the Iron and Steel Institute. At th€ 

 autumn mofting of 1909 Mr. C. A. Ljungberg gave 

 paper on production of iron and steel by electric-smel^ 

 ing processes. He mentioned the Kjellin electric inductic 

 furnace at (iysinge, with which the writer had the pleasi 

 of making with Mr. E. C. Ibbotson a full week's trial, 

 being still in work, making tool steel, special steels, selP 

 hardening and high-speed steels, and others such as nickel 

 and chromium steels. The paper dealt more in detail, 

 however, with the successful experiments on smelting pig- 

 iron at Domnarfvet by electrical means, and the resultinff 

 saving in the proportion of charcoal used. 



It will be only necessary merely to touch upon the 

 various principles used in the construction of electric! 

 furnaces, as these are found in text-books and in the Pro- 

 ceedings of the Iron and Steel Institute. Having obtained 

 an electric current, its energy may be converted into heat' 

 by putting a suitable resistance in its path, and the heat< 

 may be concentrated at any part of the circuit by making- 

 the resistance of other parts small in comparison. If the 

 resistance be a solid or a liquid, then it is called resistance- 

 heating ; if a gas, arc-heating. If the liquid through which 

 the current passes is decomposed by the current so that one 

 kind of matter goes to one pole and another kind to the: 

 other pole, the liquid is called an electrolyte. 



Varieties of Electric Furnaces. 



The Stassano furnace is an independent arc furnace- 

 Three carbon electrodes are used, between which arcs play, 

 and the heat from the arc is merely used for heating the 

 charge, partly by direct radiation and partly by reflection 

 from the dome of the furnace. 



The H^roult steel-melting furnace is a direct-arc t>p 

 in which the charge forms one pole of the arc. Tw. 

 vertical carbon electrodes come through the roof of th< 

 furnace and two arcs play, one between each electrode and 

 the molten metal or slag beneath it, the current passin^ 

 from one electrode through the metal or slag and i: 

 through the other electrode. 



The Girod furnace, like the H<5roult, is a direct-ar 

 furnace, but one or more electrodes of like polarity ar 

 maintained above the bath, and soft steel pieces embedd< 

 in the hearth of the furnace are in direct contact with th 

 molten metal for the negative electrode. These low. 

 pole-pieces are water-cooled. Large quantities of ferrr 

 silicon, ferro-chrome, &c., as well as of ordinary carbon 

 and special steels, are made in this furnace. 



The Keller steel furnace is a direct-arc furnace, vpr\ 

 much like the H^roult, only instead of two electrod 

 coming down into one cavity they come into separ.T 

 cavities, which are joined by the molten material of tlv 

 bath. 



The Gronwall is of the arc type, and the current enter 

 by two electrodes through the roof; and when once tl 

 bath is heated, so that the lining becomes a conductor, tli 

 current from both electrodes passes through the lining to a 

 graphite block underneath, and hence to a common wire. 



The Naihusius, like the Gronwall, is a combined arc and 

 resistance furnace. It contains three vertical carbon elec- 

 trodes, arranged at the apices of an equilateral triangle. 



