Steel and Iron 443 



phosphorus which remain in steel are especially undesirable. 

 Sulfur makes it very brittle when hot, and phosphorus makes it 

 very brittle when cold. The character of the steel rails produced 

 by the Bessemer process became a very serious matter when, 

 under increasingly heavy traffic, the rails broke with startling 

 frequency. Breakages have been greatly reduced in number by 

 improvements in the manufacture of steel rails, but they still 

 occur frequently enough to be a serious problem. In 1915 

 more than 3300 railroad accidents were attributed to broken rails, 

 involving a property loss of nearly $4,000,000, with more than 

 7000 persons injured and over 200 lives lost. It is one of the 

 urgent problems of to-day to produce steel rails that are flawless 

 and free from the impurities that render them unsafe. 



The Bessemer converter effectively handles pig iron from ores 

 which contain a very limited percentage of sulfur and phos- 

 phorus. As such ores have been rapidly mined and are be- 

 coming scarce, the output of Bessemer steel has decreased and 

 may eventually cease. Improvements in the converter have 

 been made, such as lining it with magnesia to suit ores contain- 

 ing a larger percentage of phosphorus, but the cost is almost 

 prohibitive. The slag which is* produced from this lining and 

 the substances introduced with the molten iron is a valuable 

 fertilizer, because of its lime and phosphorus content. But 

 the greatest advance has been in the development of the open- 

 hearth process. 



The open-hearth process converts into steel, satisfactorily and 

 profitably, ores or pig iron having a wide range of impurities, 

 and is especially successful in eliminating sulfur and phosphorus. 

 These impurities enter into the slag which, floating on top, is 

 drawn off at the right moment. The process is under control at 

 every stage, which is not the case with the Bessemer process. 

 Samples are tested frequently, thus insuring a uniform and 

 dependable product of the desired character. In making the 

 various kinds of steel demanded in modern construction, precise 

 quantities of the necessary substance, such as carbon, silicon, 



