METALLURGY. (IRON AND STEEL.) 



353 



the shops of the Bethlehem Steel Company, while 

 the details of it have not yet been published, is 

 understood to be a special heat treatment of a 

 peculiar brand of self-hardening tool steel. It is 

 said to be exceedingly simple and inexpensive, and 

 is automatic in action. The process is applied after 

 the tool has been dressed to shape, and the effects 

 of the treatment penetrate through the steel. It 

 has been applied to a number of standard tool 

 steels with increase of their efficiency, but the 

 best results are obtained from a- special com- 

 position. Steel treated by this process has the 

 quality of retaining a degree of hardness at 

 a red heat, and it is possible for tools made 

 of it to cui at a speed great enough to heat 

 the point of the tool to redness. Cutting steel 

 with a tool thus treated leaves an unusually 

 smooth finish on the work, thus greatly decreasing 

 the labor of finishing. This special steel forges so 

 readily that tools of difficult and irregular shape 

 can be made from it. A simple rapid method of 

 annealing the steel has been found by which tools 

 may be easily machined to shape, making it appli- 

 cable to twist drills, chasers, inserted cuttings, etc. 



The investigations of Mr. A. L. Colby, as de- 

 scribed by him in a paper read before the Amer- 

 ican Section of the International Association, go 

 to show that small percentages of copper have no 

 deleterious effect upon the physical properties of 

 steel. Experiments made with steel containing 

 0.565 per cent, of copper upon strength and elonga- 

 tion resulted satisfactorily, as also did those with 

 high carbon steel having a similar copper content. 

 Bars containing this proportion of copper re- 

 sponded well to bending and quenching tests, but 

 some bars bent transversely to the direction of 

 rolling developed cracks. The material was suc- 

 cessfully welded. Experiments were referred to 

 which showed that copper has little tendency to 

 segregate from a steel ingot. The author thinks 

 that good steel may contain as much as 1 per 

 cent, of copper without suffering, provided only 

 that the sulphur content is not too high, in which 

 case the metal is liable to crack in rolling. But 

 even if the proportion of sulphur is as large as 

 0.05 per cent, in steel in which as much as 0.75 

 per cent, of copper is present, there is not much 

 clanger of its cracking while being rolled. 



The progress in the use of mild steel for ship- 

 building purposes, said Mr. B. Martell before the 

 Institution for Naval Architects, may be judged 

 from the fact that while in 1876 7 steel vessels, 

 of 4,470 tons, were classed in Lloyd's Register, 

 and 435 iron vessels, of 517,692 tons, the record 

 for 1885 showed 118 steel vessels, of 165,437 tons, 

 as compared with 260 iron vessels, of 290,429 tons. 

 As wood was superseded by iron as a material for 

 shipbuilding, so in its turn iron has given place 

 to steel. Of the total output of the United King- 

 dom during the past year (1899), 98.8 per cent, of 

 the tonnage was built of steel and 1.1 per cent, 

 of iron. The iron tonnage was principally made 

 up of trawlers, and comprised no vessels of more 

 than 303 tons. Experience has shown that where 

 proper care is taken to cleanse and paint the sur- 

 face thoroughly, the deterioration of steel is not 

 appreciably greater than that of iron. In some 

 parts, however, such as the deck plating and plat- 

 ing of inner bottoms and floors under boilers, 

 steel appears to be more liable to deteriorate, and 

 in consequence of this iron is often used in those 

 parts of vessels otherwise constructed of steel. 



In respect to microscopical analysis in steel in- 

 dustries, Mr. C. H. Ridesdale has expressed the 

 "pinion that the stage has been reached when 

 from the time of receiving a sample it can be sec- 

 tioned, ground, etched, examined, photographed, 

 VOL. XL. 23 A 



and worked into a finished print in about two 

 hours. This is less time than that in which the 

 analysis for carbon, silicon, phosphorus, and man- 

 ganese is performed, to say nothing of sulphur, 

 microscopic examination, and other evidences. 

 Mr. Alfred Harvey remarked in a discussion of 

 Mr. Ridesdale's paper that the special point on 

 which microscopical examination gives information 

 was the particular heat treatment to which steel 

 had been subjected, and it was in this branch 

 that more assistance might be expected than in 

 any other. 



The breaking of a rail- at St. Neots station on 

 the Great Northern Railroad of England into 17 

 pieces, in 1895, led to the appointment of a com- 

 mittee of experts to investigate the question of 

 the loss of strength in steel rails caused by pro- 

 longed use. Each member of the committee took 

 a special feature of the steel, with particular refer- 

 ence to this rail, as the subject for his investiga- 

 tion. The St. Neots rail was found to be of 

 ordinary composition, and under the mechanical 

 tests of variable, but on the whole good, quality. 

 Its defects were brought out by microscopical 

 examination. Good rail steel, according to 

 Roberts-Austen, consists of ferrite, or iron free 

 from carbon, and pearlite, a combination of alter- 

 nate bands of ferrite and cementite. Well-devel- 

 oped pearlite with a conspicuous banded struc- 

 ture is characteristic of a good rail steel. When, 

 however, steel is hardened by quenching the pearl- 

 ite disappears, and the whole mass consists of 

 interlacing crystalline fibers devoid of banded 

 structure, and is called martensite. Sir W. C. Rob- 

 erts-Austen says concerning this, that " the de- 

 tection of martensite in a rail should at once 

 cause it to be viewed with extreme suspicion, 

 as showing that the rail is too hard locally to 

 be safe to use." In the St. Neots rail a surface 

 layer about TO^TJ of an inch thick existed, in which 

 the carbide was in the form of martensite. Mar- 

 tensite was also found in small patches in some 

 other worn and broken rails, but to a far less 

 extent. In the inquiry as to how far this struc- 

 ture could account for the brittleness of the rail, 

 it appeared that the rolling surface of the St. Neots 

 rail was traversed by a number of transverse 

 cracks of various depths. The upper surfaces of 

 rails are subject to tension over chairs by the 

 weight of passing trains applied between the 

 chairs, and cracks are formed in this way. It 

 was found that a heavy steel rail nicked with 

 a chisel to the depth of ^ of an inch broke 

 under the impact of 600 weight let fall from a 

 height of 12 feet, while the same rail, if not 

 previously nicked, resisted successfully the fall of 

 a ton from the height of 20 feet. The loss of 

 strength due to these minute cracks is therefore 

 amazing, and is accounted for by supposing that 

 shallow nicks are readily induced by shock to 

 spread through the mass. Yet as minute trans- 

 verse fissures are, according to Prof. Unwin, com- 

 mon on the surface of old rails, while few of them 

 break on the road, it must be rare for them to 

 spread into the substance of the rail. All old 

 rails become " hammer hardened " on the surface 

 by long use, and their strength and percentage 

 of elongation may be increased by annealing, but 

 no clear case of any production of martensite in 

 this way could be obtained, and what induced its 

 formation in rails was not clearly determined. 

 Roberts-Austen quotes an experiment which 

 points to the probability that local heating of 

 a rail by skidding, followed as it would be by 

 rapid abstraction of the heat by the mass of the 

 cold rail, can produce patches of martensite. 

 Though the investigation is not definitely satis- 



