1904.] Liquid Air Temperatures on Iron and its Alloys. 329 



the preceding specimens, e.g., Test Nos. 110 (C 0'19, Mn 0'52 per 

 cent.), 1 (C 0-20, Mn 0'50 per cent.), 2 (C 0'50, Mn 1-00 per cent.), 

 3 (C 0-58, Mn 0'58 per cent.), 5 (C 075, Mn 1-00 per cent.), 11 

 (C 1-05, Mn 0-58 per cent.), 12 (C 1-20, Mn 0-62 per cent.), 31 

 (C 1*68, Mn I'll per cent.). All these specimens showed the usual 

 rise in tenacity and fall in ductility, and although Specimen No. 31 

 is of abnormally high carbon, yet this does not appear to have 

 interfered with the ordinary effect of the liquid air treatment. In the 

 case of Test No. 1, after quenching specimens of the same material in 

 liquid air from 700 C. and 750 C., the same peculiar behaviour was 

 noticed as previously described, i.e., considerable increase in ductility. 



Having now dealt with the iron-carbon alloys, the various other 

 alloys may be dealt with : 



Iron and Silicon j Specimens were tested representing all these 

 Iron and Aluminium j alloys, but the results do not call for any special 

 Iron and Tungsteii J- comment, the usual increase in tenacity and fall 

 Iron and Chromium | in ductility being noticeable at low tempera- 

 Iron and Copper ] ture. 



Iron and Nickel Specimen No. 45 (C 0*26, Ni 0'58 per cent.). 

 Although the liquid air doubles the tenacity, probably owing to the 

 lower carbon and the presence of nickel, the elongation is not reduced 

 to the extent noticed in previous specimens. This is important, and 

 gives material proof that the brittleness of iron at low temperatures 

 can be modified by another element, provided the carbon is not 

 present in any considerable percentage. In another specimen, No. 46 

 (C 0-14, Ni 1-92 per cent.), the nickel appears to vigorously assert 

 itself, as the ductility at - 182 C. only decreases from 20 12 per 

 cent., the tenacity increasing from 34 59 tons. In Specimens 

 Nos. 49 (C 0-19, Ni 3'82 per cent.) and 50 (C 0'18, Ni 11-39 per 

 cent.), the remarkable effect of nickel is noticeable, as, whilst the 

 tenacity rises considerably in both cases, the ductility remains practi- 

 cally unaltered. The tenacity rose in a further specimen, No. 54 

 (C 0-16, Ni 24-51 per cent.), in which the nickel is very high, 

 from 90118 tons at -182 C., the ductility being only reduced 

 from 12 10 per cent. The specimens were non-magnetic both at 

 normal and at liquid air temperature. The same material showed 

 an increase of from 306 524 in hardness under the liquid air treatment. 



Iron and Manganese. These form an important class. The peculiar 

 alloy of iron and manganese, known as "Manganese Steel," is non- 

 magnetic, and it is possible to produce similar alloys of iron and 

 manganese even when the former element is present in as high a pro- 

 portion as 8788 per cent. Excellent results as regards physical 

 properties can be obtained upon exceeding 1J and up to 2J per cent., 

 provided the carbon is low. From about 37 per cent, the material 



