640 SUMMARY OF CURRENT RESEARCHES RELATING TO 



as sulphide of manganese, which usually is comparatively harmless. The 

 silicates have a decidedly injurious effect. Oxide occurs as minute 

 black specks, visible in the polished section with a magnification of 

 1000 diameters. These specks are invariably found in steels which give 

 blisters on pickling : this supports the view that the blisters are due to 

 the presence of oxide. Oxygen was determined by passing hydrogen 

 over heated drilhngs and weighing the water formed. The samples 

 examined by the author were found to contain • 02 to • 06 p.c. oxygen. 

 The presence of oxygen in steel appears to favour corrosion to a marked 

 degree. The pitting of boiler plates and tubes is ascribed to oxide. 



Relation between the Process of Manufacture and some of 

 the Physical Properties of Steel.* — F. W. Harbord gives the results 

 of a large number of tensile and other tests, bringing out the important 

 differences in strength of steels having the same carbon content but 

 differing in process of manufacture. For a given maximum stress a 

 basic open hearth steel requires the most, and an acid bessemer the least 

 •carbon. 



Ageing of Mild Steel.f — C. E. Stromeyer gives a large number 

 of instances in which lapse of time appeared to have an effect 

 on the physical properties of steel. Frequently this effect was a 

 development of brittleness. The author carried out bending tests on 

 strips sheared from plates, the time between shearing and testing being 

 varied. Some of the test pieces were submitted to treatments such as 

 annealing, maintaining at a low temperature, heating at 100° C. and at 

 .a blue heat. The results are conflicting, but appear to show that certain 

 steels deteriorate gradually after local straining caused by shearing, or 

 nicking with a chisel. In some cases the steels improve with the passage 

 of time. 



Carbon-tungsten Steels.| — T. Swinden has prepared nine steels 

 containing an approximately constant tungsten content (3 p.c), carbon 

 varying from 0*14 to 1*24 p.c, and has carried out mechanical tests, 

 microscopical examination, and determination of critical ranges. 

 Numerous curves were taken by the direct method to determine the 

 effect of initial temperature on critical ranges. Among the author's 

 conclusions are — 



1. A definite compound, Fe^ W, is formed by melting the two 

 elements together in certain proportions. 



2. Maximum tensile stress is higher, and elastic ratio much higher 

 .than for carbon steels of the same carbon content. 



?). Below a certain initial temperatm-e (the " lowering temperature ") 

 which is higher as the carbon content is greater, the critical points are 

 the same as for carbon steels. In steels below • 35 p.c. carbon heating 

 • beyond this temperature lowers Ar 1 to a definite " low point " (570° C. 

 for the 3 p.c. tungsten steels). With carbon 0-35 to 0-9 p.c. Ar 1 

 is first lowered. As the initial temperature is further raised, Ar 3, 2, is 



* Journ. Iron and Steel Inst., Ixxiii. (1907) pp. 181-99 (6 figs.). 

 t Tom. cit., pp. 200-260 (31 figs.). 

 X Tom. cit., pp. 291-327 (26 figs.). 



