118 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Heat-treatment of Hypereutectoid Steel.* — A. Juug has made 

 tensile tests and hardness determinations of six pure Swedish carbon 

 steels, containing 0-99 to 1"56 p.c. carbon, after different heat-treat- 

 ments. The specimens were in the form of wire, and the treatments 

 included quenching from different temperatures in various liquids, fol- 

 lowed or not by re-heating to lower temperatures. The microscopical 

 work was carried out chiefly on the steel containing 1 • 33 p.c. carbon. 

 Hydrochloric acid in alcohol was the etching reagent used ; the structure 

 of the variously treated specimens is described in detail, and numerous 

 photomicrographs are given. The conclusions relate chiefly to the 

 methods by which the most desirable mechanical properties may be 

 obtained. 



Heat-treatment of Steel. — H. Hanemann has carried out a long 

 series of heat-treatment experiments upon six steels in the form of wire, 

 containing 0"99 to 1*5G p.c. carbon. The specimens were heated in a 

 salt bath to various temperatures between 750° and 1100^0., and were 

 quenched in water, oil, or a lead-tin bath. They were re-heated in oil or 

 in a lead-tin bath, to temperatures up to 650° C. The treated speci- 

 mens were submitted to mechanical tests and microscopical examination. 

 The influence of length of time of re-heatinsc was studied for a stee 

 containing 0"87 p.c. carbon. Water-quenched specimens, re-heated for 

 various lengths of time at temperatures ranging from 100° to 650° C, 

 were tested for hardness, solubility in dilute sulphuric acid, and content 

 of carbide, and were microscopically examined. The author concludes 

 that hardened steel tends to change into a-iron and cementite at all tem- 

 peratures below 695° C. The change proceeds almost infinitely slowly 

 at ordinary temperatures ; at 650° C. it is complete in a few hours. At 

 any given temperature of re-heating the rate of change diminishes as the 

 time of re-heating is prolonged. 



Non-metallic Impurities iu Steel.:]: — H. D. Hibbard proposes the 

 name " sonims " for the solid non-metallic impurities in steel, such as 

 the oxides, sulphides, and silicates of iron and manganese. Such bodies 

 tend to accumulate, as microscopic particles, along the contact surfaces 

 of the grains formed when the steel solidifies. 



Iron-carbon System. § — 0. Paiff and 0. Goecke have determined the 

 limit of solubility of carbon in molten iron in the temperature range 

 1135^-2620° C. The iron was heated in a graphite crucible in an 

 electric vacuum furnace, and maintained at the desired temperature 

 suificiently long to secure saturation. The crucible was then allowed to 

 fall into a vessel of water. The combined carljon and graphite were 

 determined in the specimen thus quenched from the known temperature. 

 The temperature-solubility curve shows a maximum of solubility at 

 2220° C, corresponding to the formula Fe^C, and a change in direction 

 at 1837° C, corresponding to Ye^C. The specimens were microscopic- 

 ally examined. 



* Int. Zeitschr. Metallographie, i. (1911) pp. 209-55 (68 figs.). 

 t Stahl und Eisen, xxxi. (1911) pp. 1365-73 (11 figs.). 



X Trans. Amer. Inst. Min. Eng., xli. (1910) pp. 803-22 ; through Journ. Soc. 

 Chem. Ind., xxx. (1911) p. 898. 



§ Metallurgie, viii. (1911) pp. 417-21 (8 figs.). 



