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THE IEON DEPOSITS OF TASMANIA 

 By Mr. W. C. Dauncey, C.E., M.E. 



As the initial effort to establish the iron industry in Tasmania 

 failed owing to the presence of the element chromium in the product, 

 it will, perhaps, be wise for us to examine the influence of this element 

 on iron and steel. It may be considered by some as unnecessary for 

 this matter to be dealt with, but as it caused failure before, and 

 certainly exists in a large proportion in some of the Tasmanian ores, we 

 will note a few of its chief characteristics, and see in what way its 

 influence ia likely to bs felt in future ventures connected with iron 

 manufacture. Before proceeding, however, let me point out one 

 peculiarity in connection with chromium, and its presence in iron ores. 

 It is seldom found in the iron at or near the surface, but generally at 

 some considerable depth down. This is important, because a surface or 

 high level sample might lead to the belief that chromium was not 

 present, while samples taken towards lower levels might be very 

 strongly impregnated with the element, and consequently useless for 

 any but special purposes, and this only after special treatment. 



Nearly 80 years ago Berthier publicly described and recognised 

 the value of chrome-steel, and the method used by him for its pre- 

 paration was practically the same as that of to-day. When chromium 

 combines with iron, which it will do in almost all proportions, 

 certainly up to 80 per cent., it appears to oxidise very readily ; to raise 

 the saturation point for carbon ; to increase the hardness of the alloy, 

 especially of that of hardened steel ; and probably also the tensile 

 strength and elastic limit, while it has a very marked influence in 

 lessening the welding power. It does not, as soma have stated, take 

 the place of carbon in giving to steel the power of being hardened 

 upon sudden cooling, but, when present tvith carbon, it tends to 

 increase the degree of hardness taken by the steel. The influence 

 of chromium upon the hot malleableness and ductility of steel may, 

 in my opinion, be ignored, as also its influence upon the material 

 when under impact or quiescent load. 



The well-known ease with which chromium oxidises has suggested the 

 use of chrome (ferrochrome) instead of spiegeleisen as a re-carburizer 

 for the Bessemer process. But there is no reason to suppose that 

 success would be achieved by such a method. The oxides of manganese 

 arising from the reaction between the oxygen of the blown steel and 

 the manganese of the spiegeleisen are fusible and scorifiable, they 

 coalesce and rise to the surface of the molten metal. Chromium oxide, 

 infusible and practically unscorifiable, would remain mixed with the 

 steel, and thus break up its continuity and impair its forgeableness. To 

 prove this contention one has but to refer to the crucible method, in 

 which the chromium has but little chancs to oxidise ; the presence 

 of any Cr3 04, formed while the steel is molten, is liable to cause 

 deep, ineradicable veins in chromium steel, particularly if the percen- 

 tage of carbon be low, or that of chromium high. Even in working 

 chromium steels, a very strong and adherent scale forms, which renders 

 welding very difficult, if not quite impossible. The suggestion 

 to substitute chromium iron ore and calcined limestone for ferro- 

 manganese does not appeal to me in any way, and if not condemned 

 untried, should at all events be looked upon as a very doubtful 

 experiment. Sufficient has been said to indicate the chemical influence 

 of chromium upon iron and steel, and we may now turn our attention 

 to its influence upon the physical properties. It is usually supposed 



