272 Transactions of the Societij. 



enclosures present in the ferrite. On the right are crystals out- 

 side that area. Dividing the two is an irregular network-like struc- 

 ture such as we have not found in the previous photomicrographs, 

 to account for which I must revert to the manufacturing conditions. 



When the steel has been poured into the comparatively cold 

 ingot-moulds the reduction in temperature promotes solidification, 

 and it is during this period of solidification and contraction that the 

 ingot defects of " blow-holes," " contraction -cavities," and " piping " 

 are produced. The surfaces of the "piping" are oxydized, and so 

 cannot be remedied in the later stages ; but " blow-holes " (which 

 are probably produced by the evolution of CO due to chemical 

 action) generally exhibit bright metallic surfaces free from oxide 

 films, so that under favourable circumstances they may be 

 welded up. An enormous amount of experimental work and 

 research has been conducted to eliminate these defects, and although 

 considerable improvement has been effected we are still far from 

 having solved the problem. 



Under the conditions obtaining when E. 288 was manufactured 

 little had been accomplished in this direction beyond cutting a 

 sufficient portion from the finished steel to warrant the assumption 

 that the part removed contained the defects. Eeally it rather 

 introduced the sporting element in which one had to hope for the 

 best ! Despite this, however, that rather maligned individual the 

 " practical man " had his own methods of detecting doubtful 

 material, and a considerable measure of success was achieved when 

 such a man supervised the manufacture. 



In No. 13 I am of the opinion that this fine "network" is 

 evidence that a small " blow-hole " originally existed in this part 

 of the steel, the walls of which have been pressed up and welded 

 together during the rolling. Such welding is by no means im- 

 possible, and probably occurs with greater frequency than we are 

 aware of, but as these are conditions pertaining to the interior 

 anatomy of the steel it is only rarely that the opportunity is 

 accorded to study them. 



In reviewing the foregoing data we have evidence of a marked 

 segregation of sulphur ; the tensile tests gave its quota towards 

 proving the continuity of the segregation, and the analysis con- 

 firmed it. Under such conditions it can generally be taken for 

 granted that phosphorus is segregated also, and this we found to be 

 the case in the web, as shown in the " banded " structure there. 



The microscope proves that although a little FeS is present the 

 greater proportion of sulphur exists as MnS, and so is in its most 

 innoxious form ; in addition there is that welded up " blow-hole " — 

 all of which points to that portion of the ingot from which E. 288 

 was rolled. 



There is also the marked difference in the crystal structures : 

 sorbitic pearlite in the foot ; the " banded " structure in the web ; 



