NA TURE 



[November io, 1904 



ON THE OCCURRENCE OF WIDMANN- 

 STATTEN'S FIGURES IN STEEL CASTINGS. 



SOME little time ago, during his inspection of the 

 metallurgical lalboratories at the University 

 College of Sheffield, Sir Norman Lockyer exhibited 

 considerable interest in the fact then communicated 

 to him that almost invariably small steel castings ex- 

 hibited in the first stage of their manufacture the 

 ^^'idmannstatten figures, provided that the carbon was 

 near the semi-saturation point of steel, namely, 0-45 per 

 cent. The authors communicated the following brief 

 note in the hope that it would be interesting to 

 mineralogists and astronomers. 



For many years an exhaustive research into the 

 properties of steel castings has been proceeding at the 

 Sheffield College. This research necessarily involves 

 a close investigation of the influence of mass; hence 

 the weight of the experimental castings varies from 

 about 28 lb. to 2 tons. In such heavv castings as those 

 last named the Widmannstiitten figures are seldom 

 found, the slow cooling of the mass exerting an in- 

 fluence similar to that of annealing, an operation 

 which, as will presently be seen, causes a change in 

 structure so profound as almost always to destroy the 

 figures. The authors therefore selected for purjjoses 

 of demonstration research casting No. 541, weighing 

 about 30 lb. The mean analysis of drillings from this 

 rnetal, taken from a portion of the casting i| inches in 

 diameter, registered the following figures : — 



Per cent. 

 C-irli"n ... ... ... 039 



Silicun ... ... ... ... o'oS 



Manganese .. ... ooj 



Sulphur 0-03 



Phosphorus ... ... ... ... o'02 



Aluminium ... ... ... ... 003 



Iron by difference ... ... ... 99'42 



The structure of the metal as cast is shown in the 

 upper half-section of Fig. i. .As u'.ual, it exhibits two 



constituents, the magnification being too low to reve.il 

 its third and fourth constituents, nanielv, the sulphides 

 of manganese and iron also present in minute quanti- 

 ties.^ The dark etching constituent is pearlile 

 (2iFe+Fe,C), its colour being due to the liberation 

 during etching of an automatic stain composed of that 

 dark, carbonaceous colouring matter upon which the 

 well-known carbon colour tes't depends. The pale con- 

 NO. 1828, VOL. 71] 



stituent is, of course, ferrite, in this case nearly pure 

 iron, and has obviously assumed that cr^'stalline struc- 

 ture characteristic of the Widmannstatten figures. 



The lower half-section of Fig. i delineates the struc- 

 ture of the metal after the operation of annealing. 

 The two stages of annealing were carried out as 

 follows : — first, the steel, protected so far as possible 



AFTER ANNEALING. 180° UNBROKEN. 



of test-pieces : — io''x^" diam. ; bending radii 



from the air, was maintained for about seventy hours 

 at a temperature of about 950° C. ; secondly, it was 

 allowed to cool very slowly, occupying, perhaps, 

 another seventy hours in falling to a temperature at 

 which it could be comfortably handled. The result 

 was a total re-arrangement of the pattern presented by 

 the ferrite and pearlite, and a consequent elimination 

 of the figures. This change in structure was accom- 

 panied by a profound change also in the mechanical 

 properties of the steel. 



Fig. 2 reproduces, before and after annealing, bend- 

 ing tests made on bars 10 inches long and 5 inch in 

 diameter. The metal as cast snapped sharply after 

 bending through an angle of 43° over a radius of 

 i inch. The annealed steel bent through an angle of 

 iSo° without exhibiting any signs of fracture. At the 

 request of Prof. Lewis, of Cambridge University, the 

 authors have submitted to him duplicate sections of 

 the steels figured in this paper. Prof. Lewis considers 

 that an interesting point raised is as to whether the 

 occurrence of the Widmannstatten figures in pieces of 

 metallic iron dug out of the earth necessarily proves 

 them to be of meteoric origin. 



The authors have to thank their colleague Mr. J. H. 

 Wreaks, demonstrator of metallography at the Sheffield 

 College, for his patient and precise reproduction of the 

 structures figured in this note. J. O. .Arnold. 



A. McWlLLIAM. 



FORESTRY IN THE UNITED STATES. 



AMONG the professional papers of the United 

 States Geological Survey we have already noticed 

 the first six reports dealing with the various forest 

 reserves in the States of Oregon, Washington, and 

 California. The two latest reports, Nos. 7 and 8, now 

 to hand, deal with the forest conditions in the San 

 Francisco Mountains Forest Reserve and the Black 

 Mesa Forest Reserve in the State of .Arizona. The 

 former report is by .John B. Leiberg, Theodore F. 

 Rickson, and Arthur Dodwell, with an introduction 

 by F. G. Pluminer ; while the latter report w.ts pre- 

 pared by F. G. Plummer from notes by Theodore F. 

 Rickson and .Arthur Dodwell. Both forest reserves 

 were first created by proclamation of President 

 M'Kinley, dated .August 17, i8g8. The region in 

 which the San Francisco Mountains Forest Reserve 



