254 SUMMARY OF CURRENT RESEARCHES RELATING TO 



presence of which is almost inevitable in practice, although their cause 

 is purely accidental. 



Influence of Sulphur and Manganese on Steel.* — J. 0. Arnold 

 and G. P. Waterhouse conclude : — 



(1) That sulphide of iron is deadly in its effect upon steel, whilst 

 sulphide of manganese is comparatively harmless. 



(2) That the above facts are due to the fusibility, the high contrac- 

 tion coefficient, and the tendency of sulphide of iron to form cell-walls 

 or enveloping membranes surrounding cells of ferrite, whilst sulphide of 

 manganese is much less fusible, segregates whilst the iron is at a high 

 temperature, and so collects into rough globules and very seldom into 

 meshes. 



(3) That manganese retards the segregation of iron and hardenite,. 

 and that what is called pearlite in a normally cooled manganese steel is 

 really a mixture of granular pearlite and unsegregated ferrite. 



(4) That the complete segregation of the ferrite in a manganiferous- 

 steel can be brought about by very slow cooling, but that such annealing 

 injures the mechanical properties of the steel by lowering the maximum 

 stress, and the reduction of area per cent, registered by the unannealed 

 steel. 



Segregatory and Migratory Habit of Solids in Alloys and in Steel 

 below the critical points. f — J. -E. Stead concludes : — 



1. That at certain temperatures near to, but below the eutectic point 

 of the iron-phosphorus eutectic, the two constituents when quite solid 

 are capable of migrating from one part to another. 



2. That there is evidence that the large crystalline masses in solids; 

 have an attractive force for the smaller particles of the same kind, and 

 under suitable conditions draw them to themselves (" crystallic attrac- 

 tion "). 



3. That in the ordinary or primary eutectic referred to, if the whole 

 mass is of eutectic composition — the constituents being equally distri- 

 buted and in juxtaposition — the attractions are balanced, and as long as 

 the condition of equilibrium is maintained there is no segregation, at 

 least not during heating for 48 hours to a point just below the eutectic 

 melting point. 



4. That active secondary segregation occurs when the eutectic exists 

 in isolated areas, and is surrounded by masses of substance of the same 

 kind as one of its constituents. As there is no equilibrium or balance of 

 the crystallic attractions between the particles of a like kind, both con- 

 stituents draw together or segregate, and cease to be eutectic in character. 



5. That in the secondary eutectic pearlite, at temperatures below the 

 eutectic point, there is the same tendency for the constituents to migrate 

 and segregate. 



6. That in annealing steel the main softening effect takes place in the 

 zone G90° C. to 670° C. It is, however, in this zone that the elastic 

 limit of the steel is most rapidly reduced. 



* 



Journ. Iron and Steel Inst., ii. (1901) p. 234 et seq. ; Metallographist, vi. (Oct. 

 1903) pp. 302-13(9 figs.). 



t Iron and Steel Metallurgist, vii. (Feb. 1904) pp. 139-59 (10 figs.). 



