The viscosity of five synthetic silicate melts and one industrial cupola furnace slag were measured by Brookfield (inner cylinder rotation) type viscometer in the temperature range from 1300 to 1500°C. Chemical composition of the samples was: SiO2 (about 36-51 wt.%), Al2O3 (10-13), CaO (35-48), 8-15 wt.% of MgO, TiO2, FeO and other impurities. These samples were melted in Pt-Rh alloy crucible by electric furnace. On the other hand, published viscosity data in the literatures were analyzed to obtain SiO2-equivalence of alumina, NA, related to the viscosity of the melts. Hence, NA was formulated as follows: NA=1.68(NAl2O3)0.88(NMO)0.74:nol.fractuin N′A=0.0966(NAl2O3)0.88(NMO)0.74:mol.fraction Using above equation, the viscosity data in SiO2-CaO, SiO2-Al2O3-CaO and SiO2-Al2O3-CaO-MgO systems could be correlated in a relationship between chemical component index, X=NSiO2+NA, of the melts at the same temperature. In this paper, a diagram (or Table) of X-temperature-log. viscosity was presented. The availability of this diagram to rough estimation of viscosity in the silicate melts, which were of nearly neutral, ordinary composition was discussed. The viscosity coeff. obtained in this work and the data from the literature in several multicomponent systems containing small amounts of FeO, BaO, MnO, etc. were in agreement with the diagram, but the viscosity data measured in the graphite crucible and the data in FeO or MnO rich (above 15wt.%) systems indicated poor correspondence to the diagram.
A new method has been developed to determine directly the dissolved oxygen content in molten iron which has oxide inclusions in it. By using this method, the change of the dissolved oxygen content in molten iron in the process of silicon deoxidation has been clarified. The method is based on such an idea that the primary deoxidation products and the oxides formed during cooling and freezing can be differentiated when radioactive silicon (silicon-31) is added to molten ironjust before the cooling begins. In such a case, the oxides formed during cooling and freezing are radioactive, while the primary deoxidation products are not since it has been clarified that the exchange of silicon between the metal phase and the oxide phase does not occur. That is, one can estimate the dissolved oxygen content by measuring the radioactivity of SiO2 extracted from iron samples, since almost all of the dissolved oxygen has combined with silicon due to its large affinity for the latter. In each heat, 1.2kg electrolytic iron was charged into a magnesia crucible and melted in the indution furnace. The temperature of the molten iron was kept at 1600°C. Radioactive silicon was added to the molten iron at certain time after the addition of 0.5% silicon for deoxidation. SiO2 was extraccted from iron samples by the nitric acid solution technique and its radioactivity was measured with GM counter. As the half life of silicon-31 is very short (2.62hr), all the measurements were compleed within 8 hours after the radioactive silicon was produced in a nuclear reactor. The change of the dissolved oxygen content with time was determined from six runs in which the radioactive elementt was added at varions times after the primary deoxidation. The results are as follows: 1) The amount of the dissolved oxygen decreases very rapidly within one minute after the deoxidation and then continues to decrease very slowly. It is confirmed that the time required for the chemical reaction Si+20=SiO2 (Si=Si4++4e-) is negligible since the observed oyxgen content at each stage of deoxidation was found in agreement with the value predicted by equilibrium relation with silicon. This fact also indicates that the rate of decrease of the dissolved oxygen can be estimated from the rate of increase of the metallic silicon in molten iron. 2) Comparison of changes of the dissolved and the total oxygen shows that the rate of decrease of the total oxygen is determined by the rate of removal of the deoxidation products. 3) The analyses of primary deoxidation products show that these consist only of SiO2 and do not include any FeO. Thus a small amount of FeO found in final products must have been formed in the processes of cooling and freezing. This technique is supposed to be applicable to other cases in which elements other than silicon are used for deoxidation.
Isothermal transformation and continuous cooling transformation diagrams were plotted for a 0·2% C-Cr-Mo steel and the steels carburized to 0·5, 0·7 and 1·0%C respectively. In order to investigate the effect of carbon content on the transformation behaviour, hardenability, hardness, etc., a carburizing method was employed to increase the carbon content without any change of other alloying elements. Acicular ferrite forms in the upper range of bainite transformation for steels containing carbide forming elements, such as chromium and molybdenum, and it accelerates pearlite transformation. Thus, the mechanism of these transformations was discussed from the viewpoint of kinetical theory. Steels having the same carbon content were prepared by both carburizing and melting methods. Differences between both steels were studied on the transformation behaviour and mechanical properties. The results are summarized as follows: (1) In general, pearlite transformation is accelerated by an increasing carbon content. It is markedly affected by the formation of proeutectoid products. Proeutectoid cementite has a much greater effect on the acceleration of pearlite transformation than proeutectoid ferrite. (2) In the upper bainite range, initiation of pearlite reaction is markedly accelerated. It is considered that the main factor of acceleration is the increasing carbon content, caused by the formation of bainitic ferrite, and kinetic data of pearlite reaction conform to the equation of nucleation and growth. (3) Hardness of the structures formed isothermally is increased with an increasing carbon content in pearlite range. But it is less affected by the carbon content in the bainite range. On the other hand, hardness of steels which were transformed under continuous cooling conditions is much more affected by the cooling velocity and carbon content in the range of bainite formation than in that of pearlite formation. (4) Effect of carburization treatment on the transformation behaviour is primarily the annealing effect, with exception of increasing carbon content. Homogenizing effect of carburizing process narrows an interval between beginning and end of transformation. No difference could be found between mechanical properties of carburized steels and melted steels under isothermal transformation.