

METALLURGY. 



527 



metallurgical art by the Compagnie Anonyme 

 des Forges de Chatillon et Commentry as illus- 

 trated by their exhibit in the Paris Exhibition 

 of 1889, is the process of tempering steel in 

 molten lead. In the tests of armor plates pre- 

 pared by this method resistance to penetration 

 and stiffness were increased without any result- 

 ing brittleness in the metal. With pieces in 

 soft metal merely cast it was possible to obtain 

 a resistance equal to that of forged pieces. 

 Other tests were made to determine the influ- 

 ence of the process of immersion on metal, inde- 

 pendent of the ultimate use ; they were made on 

 five kinds of steel carbon, silicon, manganese, 

 chrome, and cement steel. The results are thus 

 summarized by M. Evrard : By the lead-temper- 

 ing process, a mean increase of 20 per cent, in 

 the limit of Elasticity may be counted upon ; also 

 an increase of 18 per cent, in the tensile strength. 

 These increases are more pronounced in carbon 

 steels than in any other. The minimum in- 

 crease was found in the silicon-steel series. The 

 diminution of elongation was greatest in steel 

 high in manganese; it was least perceptible in 

 chrome steel. In shock tests, the stiffness was in- 

 creased without rendering the metal more brittle. 



The force required to rupture a steel bar by 

 longitudinal stress computed by comparing the 

 load on the specimen at the moment of break- 

 ing with the contracted area at the fracture is 

 called by Mr. C. A. Cams-Wilson the " true tensile 

 strength " of the material. It is lowered by any 

 disturbance in the uniformity of distribution of 

 the stress. The tensile strength of a cylindrical 

 bar is lowered by grooving the bar in proportion 

 to the acuteness of the angle of the groove. But 

 a plain, ungrooved bar is not always the strong- 

 est, except as compared with a bar in which the 

 groove is cut with a sharp angle ; and the grooved 

 bar is considerably the stronger, notwithstanding 

 the interruption to the uniformity of the stress, 

 if the groove is semicircular. The addition of 

 material to effect a gradual change of section 

 above and below a given section, while it can not 

 increase its resistance to direct tensile stress, 

 may increase the resistance to a shearing. The 

 resistance of a bar does not then depend on its 

 section at right angles to its axis, but on its sec- 

 tion at 45 to the axis, for in that direction the 

 shearing stress is at a maximum. Hence, appar- 

 ently, the resistance overcome at rupture is the 

 resistance to shear; and this seems to be con- 

 firmed by experiment. With a uniform distribu- 

 tion of stress near the ruptured section the fract- 

 ure is at 45 to the axis, the bar having sheared 

 along that plane which is a plane of least resist- 

 ance to shear. The tendency to rupture along a 

 plane of shear may be marked by a non-uniform 

 distribution of stress. 



Nickel. The experiments of Mr. James Riley 

 and other persons with nickel iron and nickel 

 steel and their results, showing that the addition 

 of nickel to iron and steel had the effects of 

 diminishing their oxidation and improving the 

 limit of elasticity and the tensile strength, were 

 mentioned in the " Annual Cyclopaedia " for 1889. 

 Manufacturers have begun to take advantage of 

 these qualities, and the development of a nickel- 

 steel industry is promised. The valuable quali- 

 ties of natural meteoric iron have long been 

 known, and many persons have in the past ex- 



pressed the opinion that those properties were due 

 to the nickel contained in it. As early as 1853, 

 according to a paper by Mr. J. T. Donald, nickel- 

 iferous iron ores from Marqtiette, Mich., were 

 found to produce iron possessing unusual tough- 

 ness, a very white color, and a diminished liabil- 

 ity to oxidation. In 1888 patents were taken 

 out in England and France by different persons 

 for the preparation of nickel steel. Tests of this 

 alloy have been made by competent experi- 

 menters with results establishing its excellence, 

 among which may be mentioned the following : 

 A steel containing 4-7 per cent, nickel showed an 

 ultimate strength of 80 per cent, and an elastic 

 limit of from 60 to 70 per cent, higher than those 

 of mild steel of nearly equal ductility ; and to 

 this the valuable quality was added of less liabil- 

 ity to corrosion. Sir Frederick Abel said in his 

 presidential address before the British Associa- 

 tion : " It has been shown by Riley that a particu- 

 , lar variety of nickel steel presents to the engineer 

 the means of nearly doubling boiler pressure 

 without increasing weight or dimensions." Some 

 persons have expressed doubts whether faith in 

 the excellence of nickel steel will be maintained ; 

 but they are answered for the present by the 

 greatly increased demand which has sprung up 

 among steel makers for ferro-nickel to be used 

 in making the alloy. The results of the tests 

 made at Annapolis, Md., in September, 1890, of 

 the resisting power of armor plates go far toward 

 establishing the superiority of the nickel-steel 

 alloy for such defensive work, The strength of 

 the nickel-steel plate was such that, though it was 

 penetrated by the shots, no cracks were developed 

 in it; while" the all-steel plate was split into 

 quarters. The Cammell compound plate, made 

 of an alloy containing less than 4 per cent, of 

 nickel, was very much broken. 



The results of experiments by Herr T. Fleit- 

 mann on the nature of the welding of iron and 

 nickel mark as the conditions necessary to obtain 

 perfect welding perfect metallic contact of the 

 two surfaces and a considerable difference of tem- 

 perature between the point of fusion and that of 

 plastic softness. The prejudicial effect of com- 

 bined and alloyed foreign substances is due to 

 their action in either diminishing the softness 

 or sensibly lowering the welding point of the 

 metal. The welding capability of nickel is large- 

 ly increased by an addition of magnesium, which 

 removes combined oxygen and carbonic oxide, 

 and raises the melting point about 100 C. The 

 so-called welding mediums serve either to clean 

 the surfaces or prevent, their oxidation when 

 heated, and are of no further utility. They may 

 be dispensed with when the surfaces are clean, 

 and other methods are adopted to exclude air. 



The studies of J. A. Ewing and G. C. Cowan 

 of the magnetic qualities of nickel tend to con- 

 firm and extend Sir William Thomson's observa- 

 tion that longitudinal pull diminishes magnetism 

 in the metal. The effects of stress are much less 

 complex than in iron, and cyclic variations of 

 stress are attended by much less hysteresis. 



Mr. F. J. Hall, referring to his applications of 

 nickel steel to gun barrels, propeller blades, and 

 other purposes, observes that in a certain experi- 

 ment he obtained with nickel steel a tensile 

 strength of 97 tons per square inch, with an elon- 

 gation of 7 per cent. 



