The electric conductivity of liquid PbO-SiO2, PbO-GeO2, PbO-P2O5, PbO-B2O3 and PbO-SiO2-GeO2 systems have been measured at the frequency of 1000c/sec. The conductivity of each system increases as the temperature increases. The Arrhenius type plots show a linear relationship and the activation energies for the binary systems range from 7.7 to 9.8kcal/mol at the composition of 90 mol% PbO. The activation energies for electric conduction increase and the conductivities decrease with increasing acid oxide concentration. The variations of the conductivity by acid oxide concentration is suggested to be due to change of the fraction of anionic species in the melts. Ionic distribution for the system PbO-SiO2 was calculated by the equations proposed by C. R.. MASSON and the relations with the conductivity have been discussed. On the assumption that Pb2+ is the sole carrier of electric conduction, the contribution of the mobility of Pb2+ to the conduction is supposed to be larger than that of the number of Pb2+ ions.
The mechanism on the deoxidation of liquid iron with Si was studied on the basis of the various facts obtained by the experiments A, B, and C. Experiment A; An investigation was made on the change of the oxygen content in liquid iron and the shape and the size distribution of the inclusion, after addition of metallic Si. Experiment B; The process of growth and the composition of the deoxidation products were studied, after the prompt and homogeneous dissolution of deoxidizer Si or Si-Al. Experiment C; The mechanism of dissolution of oxygen from the SiO2 crucible into liquid iron was studied. The results obtained were summarized as follows. 1) The formation of SiO2 is not completed immediately after addition of Si and consequently the supersaturation in liquid iron occurs until the equilibrium is reached. 2) It was concluded that the growth of the oxide particle or the deoxidation reaction was not controlled by the diffusion of the solute atom, but the reaction rate at the particle surface, and in general the local equilibrium was not maintained there even at steelmaking temperature. 3) The ratio of the rate constant for the reaction Si+2O→SiO2, 2Al+3O→2Al2O3 was estimated by means of the composition of the products obtained by the Si-Al deoxidation in the experiment B. The ratio was constant in a wide range of the concentration of aluminium, silicon and oxygen in liquid iron. 4) In the experiment A, the greater part of the primary inclusion floats out rapidly and the total oxygen agrees nearly with the dissolved oxygen 5 minutes after addition of silicon. 5) The mechanism on the formation of the inclusion during solidification was discussed from the point of view of nucleation and growth of the oxide particle.
In order to investigate the behaviors of hydrogen embrittlement and stress corrosion cracking in austenitic stainless steel, the change in ductility of 18Cr-8Ni steel under various environments was studied chiefly by means of 180°repetition bending test. The main results obtained are as follows: (1) The hydrogen embrittlement in austenitic stainless steel was determined sensitively by the bending test after pickling and electrolysis. (2) It was found that the steel also embrittled during stress corrosion test in boiling 42 percent magnesium chloride solution and took a process analogous to that of hydrogen embrittlement by pickling and electrolysis. (3) The hydrogen occlusion owing to various environments occured only near the surface layer, and the recovery of ductility was limited at the initiation period of the embrittlement and the longer exposure time made the more embrittlement. (4) It was concluded that the hydrogen embrittlement plays an important role in the formation of the susceptible paths for the stress corrosion cracking of austenitic stainless steel.