PHYSICS — HOWE. 215 



Howe, Henry M., Columbia University, New York, N. Y. Grant No. 427. 

 To determine the inftuence of ingot-size on the degree of enrichment of 

 the segregate in steel ingots, and the homogeneousness of the ingots out- 

 side the region of maximum enrichment. $1,000. 



The solidification of every liquid or molten body is a process of differentia- 

 tion by selection, perfectly pure, simple substances, like distilled water, being 

 excepted. Each layer of the mass in solidifying splits up into two unlike sub- 

 layers, one which freezes and thus joins the already frozen part, and one 

 which, remaining liquid, is rejected by the freezing part. In general, the 

 sublayer which remains molten is more fusible than that which freezes and 

 therefore contains an undue proportion of one or more substances which 

 increase the fusibility, i. e., lower the melting-point; and the consequence 

 of this successive differentiation, as layer after layer freezes, is that these 

 fusibility-giving substances are gradually concentrated into the last-freezing 

 part, which may thereby be materially enriched in them. This enrichment 

 of the last-freezing parts and impoverishment of the earlier-freezing ones 

 is known as segregation. In the case of ingots of steel, the substances which 

 segregate most are carbon, phosphorus, and sulphur. The segregation of 

 carbon is extremely important, because carbon influences the properties of 

 the metal very greatly, strengthening it at the expense of its ductility. The 

 enriched part or "segregate" of a given steel ingot may be wholly unsuited 

 for the use to which the ingot as a whole is intended, because its high carbon 

 content may make it too brittle. Further, the heterogeneousness of strength 

 and of ductility which the irregularity of carbon content gives may in itself 

 be very harmful. 



The segregation of the harmful elements, phosphorus and sulphur, may be 

 very important, because it may make the last-freezing parts prohibitorily 

 rich in these elements. 



This investigation is essentially an attempt to digest and analyze the great 

 mass of scattered results, which many investigators of segregation have 

 reached, to see what laws can be based on them and to fill the gaps which 

 they leave. Such an attempt Professor Howe made some 17 years ago,* but 

 there has been none since. 



Professor Howe first analyzed the recorded observations of others and 

 then had ingots specially cast, and examined them by analyzing drillings taken 

 systematically. The total number of previous cases, published and unpub- 

 lished, which were analyzed, was 168, representing about 2,600 chemical 

 analyses, most of which consisted of determinations of several different 

 elements. The ingots made specially for this investigation were 8 cast-iron 

 ones, 2.25 inches square, and 17 steel ones, from 2.25 inches square to 17 

 inches square. Their total weight was about 22,000 pounds, or 1 1 short tons. 



* The Metallurgy of Steel, 1890, p. 202, 



