METALLURGY. 



429 



thinner; but aluminum has still to be employed; 

 while in casting a steam cylinder jacket of about 

 4 tons' weight improvement was visible. The 

 charge in the cupola contained 75 per cent, of ma- 

 chine scrap and 25 per cent, of pig iron. The ferro- 

 sodium was thrown into the ladle, and gave, when 

 the cast iron was poured into it, dense fumes. 



" Semi-steel " is the name given to a material 

 formed by mixing steel scrap with pig metal to 

 strengthen the resulting castings. It was first, used 

 in 1870 for car wheels, and subsequently for brake 

 shoes. It has since been used in hammer dies, etc. 

 It is claimed that greater strengtli and a closer 

 grain are imparted when it is used in proper pro- 

 portion with good charcoal irons. 



The characteristic features of the Tropenas pro- 

 cess for steel are defined as being : (1) Low pressure 

 blast, always above the surface of the metal and 

 through the lower or firing tuyeres ; (2) disposition 

 of the tuyeres in the horizontal plane, so that the 

 jets of air, arriving above the bath, can not impart 

 to the latter any gyratory motion ; (3) great depth 

 of the metallic bath, so as to avoid the churning 

 and stirring of the latter during the operation ; 

 and (4) arrangements above the " firing tuyeres," 

 and independent of the latter, of a supplementary 

 row of combustion tuyeres, so as to burn the com- 

 bustible gases escaping from the metallic bath and 

 thus increase the final heat of the metal. Iron is 

 produced by this process in so great purity and at 

 such a high temperature that it is possible to make 

 the most varied final additions with the view of 

 producing different qualities of steel, from the soft- 

 est to the hardest, and all the intermediate grades. 

 This is done by modifying the final addition accord- 

 ing to the product required. 



In a newly described American process for tem- 

 pering steel the article to be tempered is heated in 

 a charcoal fire, and after being thoroughly rubbed 

 with ordinary washing soap is heated to a cherry 

 red. In this state it is quickly plunged into pe- 

 troleum. It is said that the parts hardened by this 

 method show no cracks, and do not warp ; and that 

 after hardening they remain nearly white, so that 

 they can be finished without cleaning or grinding. 



A direct process for tempering steel under pres- 

 sure has been brought forward in Germany by Herr 

 Ilaedicke. Of the two methods in which this may 

 be performed one is by hardening the steel first by 

 plunging it red hot into cold water and then draw- 

 ing the temper, and the other is by plunging it into 

 certain chemical baths. The process has been so 

 far applied in the manufacture of saws and steel 

 ribbons. 



In experiments made at the Washington Navy 

 fard on the porosity of thin steel plates under 

 heavy hydraulic pressure, pieces of sheet steel of -J-, 

 i, iV- and sV inch in thickness were subjected to a 

 water pressure of 6,000 pounds per square inch. Per- 

 colation was not found in any case. A f-inch rivet 

 joining two -inch plates also proved tight under 

 the same pressure. A test made to determine the 

 friction of water under high pressure, while incon- 

 clusive, gave no evidence that it was any greater 

 than the friction of water not under pressure. 



Experiments of MM. C. Chistoni and G. de Vecchi 

 on the magnetic qualities of Valtrompia tungsten 

 steel gave satisfactory results, even superior to 

 those obtained by Barus and Stronhal. The de- 

 magnetizing influence of time is represented not to 

 have been felt, except after magnetization in the 

 strongest fields ; and the experimenters assert that 

 after exposure to a comparatively weak field the 

 magnetization went on increasing independently for 

 some time. After saturation the time required to 

 each a stationary condition differed in various spoci- 

 iciis. being longer in thick rods than in thin ones. 



Concerning the relative value of iron and steel 

 plates and forgings for use in shipbuilding, M. 

 M. W. Aisbett said at the meeting of the South 

 Staffordshire Iron and Steel Institute that steel 

 was preferred to iron in consequence of the reduced 

 scantling that was allowed, and even where the 

 scantling was the same, on account of its ductility 

 ami the consequent possibility of bending it cold to 

 any desired shape. Iron, being of larger scantling 

 anil not so ductile, was more rigid and less liable to 

 throw off scale. It also corroded at a slower ratio 

 than steel. In the case of strandings and ground- 

 ings the author had generally found that of two 

 given vessels which struck rocks, one iron and one 

 steel, the repair of the iron one would cost consider- 

 ably less than that of the steel one. His own im- 

 pression was that a combination of steel and iron 

 would be most advantageous for shipbuilding pur- 

 poses. 



Iron and steel are found to be much more brittle 

 at their critical temperature, or what is called the 

 blue heat, from 460 to 600 F., than when cold or at 

 redness. This heat however, does not seem to leave 

 any bad effect, though, if the piece be worked in 

 such a range of temperature, it will retain the 

 brittleness after cooling, and show a great loss of 

 ductility. The poorer the iron the more susceptible 

 it is to the blue heat. The danger to steel at this 

 fatal blue point is more pronounced than in iro)i ; 

 but it exists to a greater or less extent in all iron of 

 whatever grade, and is more noticeable in a descend- 

 ing than an ascending heat. 



The danger of using too hard steel rails is con- 

 sidered by G. P. Sandberg in the light of several 

 years' experience as consulting engineer and rail 

 inspector for railways in Sweden. A medium 

 hardness has always been aimed at in that country. 

 as well as a minimum of phosphorus for the cold 

 climate. Lately the higher wheel loads and speed 

 have made it desirable to use a harder quality of 

 steel in order to avoid crushing of the rails. The 

 hardness has been obtained by using more carbon, 

 or from 0.35 to 0.45 per cent., and more manganese 

 up to 1 per cent., with silicon up to 0.1 per cent., 

 and the phosphorus not more than 0.075- per cent. 

 Experiments made with a few casts of this exces- 

 sive hardness of carbon, or 0.60 per cent, in 80- 

 pound rails, resulted in their flying into many 

 pieces with less than half the specified trip test for 

 safety, while casts with 0.45 per cent, carbon stood 

 one ton falling 20 feet. The authors conclusion is 

 that in a severe climate, such as that of Sweden, 

 constructors should not try to remedy the deficiency 

 in weight of rails used at the original building of 

 the railways by now resorting to a dangerous hard- 

 ness of rail steel retaining the same section, but 

 should rather adopt a heavier weight of rail of 

 moderate hardness, and consider safety before all. 



Many persons who use forgings of iron and steel, 

 Mr. H. F. J. Porter observes, say that they prefer 

 wrought iron to steel for the connecting rods and 

 crank pins of their engines, because steel, having 

 no fiber, is brittle and snaps suddenly; while 

 wrought iron, being fibrous, does not ; that while 

 wrought iron and steel both crystallize from shock, 

 iron, being tougher, will outlast steel in such serv- 

 ice as is performed by pistons of steam hammers ; 

 and that low carbon steel is softer than high carbon 

 steel, and is therefore less brittle and not so apt to 

 break in the forged parts of their machines. These 

 views are declared by Mr. Porter to be mistaken. 

 Such defects as have been revealed in forged steel 

 are not due to the nature of the material, but to 

 faults in the working of it. Steel does" not possess 

 to the same degree as wrought iron the property of 

 welding. Instead, therefore, of building up a forg- 

 ing of small pieces, it is necessary to work down the 



