METALLURGY 39 i 



In steel-making, the general progress of the open-hearth processes as compared with 

 the Bessemer is the most prominent feature, especially as regards the basic open-hearth 

 process. In America even for rail-manufacture the open-hearth has largely supplanted 

 the converter. The open-hearth furnaces themselves are steadily increasing in size, 

 the 50 and 75 ton furnaces of previous years being replaced by loo-ton units. This 

 increase in size is accompanied by devices for prolonging the life of the furnace, principal- 

 ly by the more extensive use of water-cooling and the introduction of removable furnace 

 ports. The importance of maintaining the shape and position of the ports having been 

 recognised, water-cooling has been employed; on the other hand the use of removable 

 ports makes the life of the furnace independent of the life of the ports. Thus a basic 

 open-hearth furnace which formerly had a life of 350 to 500 heats now runs up to 1,000 

 heats with three changes of ports. 



Rolling-mill practice (E. B. xxiii, 468) has developed concurrently with the develop- 

 ment of the furnaces; in America particularly, the tendency for obtaining very large 

 outputs by installing plant of great power and speed has been strongly marked. The 

 rolling-mill installed at Gary, Indiana, may be taken as an example. This mill is 

 driven by a 6500 horse power electric motor working on a circuit at 6000 volts three- 

 phase current at 25 cycles; a 1 2-inch ingot can be broken down in this mill and rolled 

 into a -inch plate in 22 parses in approximately two minutes. It is however doubtful 

 whether the market can dispose of the enormous full-power output of these very large 

 mills, and the question of the quality of the resulting products is also a serious one. It 

 is claimed, however, that there is now a strong tendency for American steel-makers to 

 pay greater attention to the quality of their products than has Hitherto been the case. 

 The serious troublesvexperienced with steel rail fractures in recent years have no doubt 

 produced some such effect. The mill just referred to is typical also of the tendency 

 towards the increased use of electric motors for driving rolling mills. 



An important feature in recent development in siderurgical practice is the steady progress 

 of the electric furnace. At Trollhattan in Sweden electric iron ore smelting has been in 

 continuous use and it is claimed that under the favourable conditions as to water-power 

 which prevail there the process is profitable. More frequently the electric furnace is em- 

 ployed simply for refining or rather "super-refining" steel which has been roughly freed 

 from its impurities either in the converter or the open hearth. For this purpose one or two 

 American steel works have installed combined open-hearth and electric furnaces, in which 

 the steel is first "roughed down" under gas heating and electric heating is employed only for 

 the final stages. The use of electrically melted steel for the production of steel castings 

 has developed considerably and a steel foundry working entirely with Stassano electric 

 furnaces has recently been put down in England. The advantages of "electric" steel in 

 regard to freedom from gases, oxides, etc. are now widely admitted, but excessive and ludi- 

 crous claims on behalf of this material are still put forward at times. An interesting special 

 use for the electric furnace has recently been found in melting the ferro-manganese or ferro- 

 silicon prior to its addition to the molten steel in the ladle or the furnace; considerable ad- 

 vantages are claimed for the practice of making these additions in the molten state. 



The difficulties experienced with steel rails in America and elsewhere have drawn atten- 

 tion to the question of soundness of ingots and the effect of blow-holes. In regard to the 

 latter Stead has shown that deep-seated blow-holes certainly, and even superficial ones 

 probably, weld up completely when the ingot is rolled, provided that the holes are not 

 associated with sulphide enclosures. Hadfield, on the other hand, regards complete freedom 

 from blow-holes as essential and prefers a steel which settles well and " pipes," but he counter- 

 acts the piping tendency by supplying the ingot during cooling with hot liquid steel from a 

 "feeding head" placed on top of the ingot-mould, in which the steel is kept molten by a layer 

 of charcoal kept in active combustion by the aid of an air-blast. Talbot, again, consolidates 

 his ingots by giving them a few passes through the cogging-mill while their interior is still 

 liquid, thus claiming to produce in a simple and inexpensive manner the same results as 

 the Harmet compression process. Goldschmidt claims that soundness may be insured by the 

 introduction of a cartridge of thermit into the bottom of the solidifying ingot, and quotes 

 examples from an extensive practical trial in support of his claim. 



The use of alloy and "special" steels has extended very considerably, notably in the case 

 of steels to which vanadium and titanium have been added during manufacture. In the case 

 of vanadium this has become possible by the fact that the price of vanadium alloys at one 

 point dropped to one half of the former figure, and the use of vanadium steels has increased 

 considerably. The use of "titanium steels" has however increased particularly in Amer- 

 ica more widely than that of any other special steel. American metallurgists regard 



