265 



YIII. — On the Microdruchire of Hypo-eutectoid Steel as contrasted 

 icith that of Normal Steel, tvith a Note on the Micro- 

 scopical Methods adopted in the Examination of Steel 

 Specimens. 



By E. Atkinson, A.M.Inst.L.E., F.C.S., F.E.M.S, etc., 

 Engineer and Metallurgist. 



{Read April 17, 1918.) 

 Plates I-III, and One Text-Fig. 



Although for many years the microscope has proved absolutely 

 indispensable in many fields of research, it is only during compara- 

 tively recent years that it has found a place in metallurg}-. Previous 

 to the introduction of the microscope, " science " was often looked 

 on either with suspicion or contempt by the practical man engaged 

 in the manufacture of iron and steel. Even the analytical chemist 

 was merely tolerated rather than recognized as being of value or 

 assistance in the production of steel on a commercial scale. 



Analyses made by several chemists on the same steel were 

 occasionally found contradictory in results, so, perhaps after all, it 

 is not very surprising that any further introductions of " scientific " 

 nature were liable to be held suspect. However, thanks to the 

 metallurgical microscope, we are enabled to clear up much whicli 

 was mysterious. It can be seen that, given a satisfactory chemical 

 composition, incorrect after-treatment may render the finished steel 

 either wholly or partly unsuitable for use. Again, as the micro- 

 structure may not be uniform, in such cases uniformity in analysis 

 is not to be expected, despite the utmost skill of the analysts to 

 give consistent results. I think this will be fairly well illustrated 

 in the case of E. 288, which forms the subject of this paper. 



By the development of photomicrography, the metallurgist has 

 a means of providing permanent records, from which much good 

 may accrue, particularly if he have also a practical knowledge of 

 the methods used in the manufacture of iron and steel, in which 

 case precautions can be taken to eliminate the recurrence of similar 

 difficulties. 



The largest percentage of steel in use to-day is of the " hypo- 

 eutectoid " class, or " mild steel " as it is termed in the trade, and 

 consists of steels containing various percentages of carbon not 

 exceeding 0*85 p.c. In such steels examination under the 



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