[ 107 1 



XII. 



NOTE ON A REMARKABLE INCREASE OF MAGNETIC 

 SUSCEPTIBILITY PRODUCED BY HEATING MANGA- 

 NESE STEEL FILINGS. By Professok W. F. BARRETT. 



[Read March 21, 1888.] 



The remarkable physical properties of manganese steel formed the 

 subject of a Paper I read before the Royal Dublin Societ} T , in 

 December, 1886. 1 In that Paper it was shown that a steel con- 

 taining from 12 to 15 per cent, of manganese, manufactured by 

 Messrs. Hadfield & Co., of Sheffield, is almost devoid of magnetic 

 properties, its magnetic susceptibility being almost insensible even 

 in the most powerful magnetic fields. Unlike ordinary steel, manga- 

 nese steel is annealed by heating to redness and plunging in cold 

 water, and made hard and brittle by slow cooling. By careful 

 annealing, I obtained wire of this steel, and found it had an 

 enormous tenacity, the hard manganese steel wire exceeding the 

 tenacity of steel wire, and being only surpassed by the best piano- 

 forte steel wire. It had a low modulus of elasticity, and a very 

 high elastic resistance, three and a-half times that of iron wire. 



I have now to bring before the Society another curious property 

 possessed by this alloy. "When visiting Messrs. Hadfield's steel 

 works, at Sheffield, last Christmas, Mr. Hadfield drew my attention 

 to the fact, that filings of manganese steel were feebly attracted to 

 a magnet, though the casting from which they were bored was 

 non-magnetic ; and, further, that heating the filings to redness 

 caused them to be strongly attracted to a magnet, after cooling 

 down again. My explanation of the phenomenon, at first sight, 

 was, that particles of the steel-boring tool had become abraded, 

 and, mingling with the non-magnetic filings, caused the quasi- 

 magnetic character of the filings of the alloy. Mr. Hadfield, 

 however, supplied me with some of the filings for further investi- 

 gation. Experiment showed that the filings of any given alloy 



Vide these Proceedings, vol. v., p. 360. 



