October 5, 1905] 



NATURE 



573 



Alpha range. The change to hardenite is somewhat 

 advanced when Ac i merges into Ac 2 at about 720° C. 

 owing to these points alwa3's overlapping in the heating 

 curve. The hardenite areas probably remain unchanged on 

 the sites previously occupied by the pearlite until the Gamma 

 range Ac 3 is reached (at about 810° C), when the hardenite 

 and ferrite dissolve into each other, forming a homogeneous 

 molecular nii.xture. In a saturated steel there is, on 

 heating, a single absorption of heat at the change point 

 Ac I, 2, 3, the amplitude of which ranges from about 

 710° C. to 730° C. This change marks the transformation 

 of the whole mass from pearlite into hardenite. On cool- 

 ing, there is a very considerable evolution of heat at the 

 single point Ar i, 2, 3, the amplitude of whicli ranges from 

 about 690° C. to bbo° C. This recalescence marks the 

 transformation of hardenite into pearlite. The particular 

 phase of pearlite obtained depends upon the rate of cool- 

 ing from 660° C. to atmospheric temperature. The 

 emulsified phase is produced by very rapid cooling, normal 

 pearlite by ordinary cooling, and laminated pearlite by 

 very slow cooling. Pearlite, in which the carbide is 

 emulsified or " sorbitic," may also be produced by temper- 

 ing hardenite. The micrographic and thermal transform- 

 ations of a supersaturated steel are as follows : — At 

 Ac I, 2, 3 the sectional ground mass of pearlite changes to 

 hardenite. the cementite slowly segregates into larger 

 masses until a temperature of about 900° C. is reached, 

 then the cementite and hardenite dissolve one into the 

 other, and a homogeneous mass of hardenite and cementite 

 is obtained. On cooling, at about 900° C. the cementite falls 

 out with a faint evolution of heat, and is completely segre- 

 gated long before the point Ari,2,3 is reached, hence 

 the micrographic transformations of cementite and 

 hardenite are quite unconnected with the three thermal 

 critical points or any of them, and are due entirely to the 

 influence of temperature. 



Mr. A. W. Richards and Mr. J. E. Stead, F.R.S., read 

 a paper on overheated steel, describing experiments supple- 

 menting their previous work on the subject, and showing 

 that re-heating overheated good steel can be relied upon 

 to restore good properties to brittle material. Steel 

 initially bad, brittle, and dangerous owing to irregularity 

 in the distribution of the elements cannot, however, be 

 made good by any kind of heat treatment. 



iVIr. L. Guillet (Paris) contributed a paper on the special 

 steels used for motor-car construction in France. Steels 

 with low percentages of carbon and nickel are used for 

 parts which require case hardening and quenching. Steels 

 with medium percentages of carbon and low percentages 

 of nickel are used after quenching and re-heating for a 

 large number of parts. Steels low in carbon and high in 

 nickel are used for valves. Chromium steels with high 

 carbon and low chromium are used for bearings. Silicon 

 steels are used for springs and for gearing. Nickel 

 chromium steels are used for numerous parts requiring 

 resistance to shock. 



Mr. Guillet also submitted an exhaustive paper on the 

 use of vanadium in metallurgy. Vanadium improves the 

 properties of alloys. In normal steel it increases the 

 tensile strength and elastic limit, and in quenched steel 

 it acts in the same way without increasing the brittleness. 

 Vanadium is certainly the element which, together with 

 carbon, acts with the greatest intensity in improving alloys 

 of iron. 



The paper read by Mr. B. Talbot (Middlesbrough) on 

 segregation in steel ingots was one of great interest, as, 

 although attention has been directed to the effects of 

 segregation, little has been published as to means of 

 lessening the amount of such segregation. The author's 

 investigations, in which parallel tests have been made on 

 ingots from the same heat with and without the addition 

 of a small amount of aluminium, are of special value. 

 The ingots were obtained from both acid and basic open- 

 hearth furnaces, and were 5 feet 6 inches in height, the 

 drillings for analysis being 'taken over the whole surface 

 of the divided ingot. When no aluminium was added 

 excessive segregation down the central line of the ingot 

 occurred from 6 inches from the top to about half way down 

 the ingot. Sulphur is the element that tends to segregate 

 most, phosphorus next, then carbon, and finally manganese. 

 NO. 1875, VOL. 72] 



With the use of aluminium, a billet of much more regular 

 composition is obtained. 



Mr. Douglas Upton (Jarrow) described an ingenious 

 mechanical device for handling steel bars during the 

 process of manufacture. 



Mr. L. Dumas (Paris) read a lengthy paper on the 

 reversible and irreversible transformations of nickel steel. 

 The starting point of the investigation was Prof. John 

 Hopkinson's well known experiment in 1889. Nickel, 

 manganese and carbon, introduced into a steel, the author 

 finds, determine alike the appearance of the same pheno- 

 menon, irreversible transformation, which is the more 

 intense the higher the proportions in which they are 

 present. They must also be in solution, a state which is 

 often, as regards carbon, impossible of attainment without 

 the aid of chromium. The nickel steels which have not 

 undergone transformation, although too costly to be of 

 industrial use, are of great interest as showing the result 

 of adding nickel to steel. The homogeneity is increased, 

 and the proportion of ;3-iron intensified. 



-Mr. G. B. Waterhouse (New York) submitted a paper 

 giving the results of the investigation of a series of steels 

 of constant nickel with varying carbon percentages. The 

 results showed that nickel raises the tenacity without 

 materially lowering the ductility. Annealing lowers the 

 tenacity without greatly raising the ductility. Nickel 

 lowers the transformation points Ar3,2 and Ar i about 

 20° for every i per cent, of nickel. 



Captain H. G. Howorth, R.A., contributed a paper on 

 the presence of greenish coloured markings in the fractured 

 surfaces of test-pieces. The attention of the Ordnance 

 Committee was directed to defects of this kind in test- 

 pieces from tubes for guns, and the object of the paper 

 was to ascertain to what extent the presence of such 

 defects should weigh in accepting or rejecting the forgings 

 for this purpose. The flaws appear to be due to slag, and 

 in any forging subject to violent alternating stresses these 

 flaws in prolongation may easily develop into craclis. 

 Interesting contributions to the discussion were made by 

 General O'Callaghan, president of the Ordnance Com- 

 mittee, and by General Sir J. Wolfe Murray, Master-general 

 of the Ordnance. 



Mr. Thomas Andrews, F.R.S., contributed a paper on 

 the wear of steel rails on bridges. He received from a 

 railway company the fractured portions of an acid Bessemer 

 steel rail which had broken in main line service after 

 eleven years and five months' service on a bridge. It had 

 borne 148,000,000 tons of passing traffic, and had lost 

 0.69 lb. per yard per annum in weight. One of the chief 

 causes of the fractuie has been the defective segregated 

 chemical composition of the rail. The percentages of 

 combined carbon and manganese, found in the top of the 

 rail head and in the bottom flange, were in excess of what 

 should obtain in good rail steel. The chemical composition 

 was an undesirable one, and such as is liable to lead to 

 brittleness and sudden fracture in rail service. The high- 

 power microscopic examinations confirmed the results 

 arrived at by the chemical analyses and physical tests, and 

 they demonstrated the non-uniformity of the physical and 

 crystalline structure of the rail. The microscopic examin- 

 ations have also shown the undesirability of employing 

 rails having too high a percentage of combined carbon 

 and manganese, and they have indicated that great care 

 should be exercised in the thermal treatment of rails, from 

 the ingot to the finished rail, in order to obtain a suitable 

 microcrystalline structure resulting in a good durable rail. 



The existence of troostite can no longer be questioned, 

 but opinions as to its nature are divided. Dr. C. 

 Benedicks fUpsala), in a paper on the subject, expressed 

 the view that troostite is a pearlite with ultra-micro- 

 scopically small particles of cementite. In all probabilitv 

 troostite is formed by a transformation in situ of 

 martensite. 



Prof. E. D. Campbell (Michigan University) contributed 

 a paper on the occurrence of copper, cobalt, and nickel in 

 American pig-irons. The percentages varied in the speci- 

 mens analysed from o.oii to 0.039 of copper, from a 

 trace to 0.048 of cobalt, and from a trace to 0.072 of 

 nickel. The only two irons containing any considerable 

 amount of cobalt and nickel possess valuable properties 

 for car-wheel castings. 



