Societies and Academies

Abstract

LONDON. Royal Society, Mar. 31.—Sir Robert Hadfield: Alloys of iron and manganese of low carbon content. The range of alloys covers 0-06 per cent. to 38-90 per cent. manganese, also one additional alloy containing 83 50 per cent. manganese. With 4-00 per cent. to 10 00 per cent. manganese the alloys have a comparatively high Brinell hardness, in the region of 400, and are brittle; from 1500 per cent. to 39.00 per cent. manganese, characteristics are observed similar to those of manganese steel, though only to a limited extent—that is, a comparatively low Brinell hardness, in the neighbourhood of 200, with considerable tenacity and ductility and fair capacity for workhardening. The alloy containing 83 50 per cent. manganese is hard, brittle, and unforgeable. With 16-00 per cent. or more of manganese the alloys are non-magnetic, whereas in the presence of 1 per cent. of carbon not more than about 7 per cent. manganese is required to take away or suppress the magnetic qualities of the iron. The electrical resistance, while increasing with manganese percentage up to 87-2 microbms per cubic centimetre for the 38-90 per cent. alloy, does so in a fairly continuous manner and without any changes of a critical character such as those observed for the specific magnetism. In their corrodibility the alloys show under some conditions a somewhat improved resistance as compared with ordinary steel, but not such as to make them of any practical value in this connexion. In their microstructure the alloys with increasing manganese percentage pass at 4 per cent. from a pearlitic structure to a martensitic, which at about 16 per cent., that is, the point where almost completely non-magnetic qualities appear, changes into the austenitic type.