The large perfect crystals of typical calcium ferrites were successfully synthesized by “solid-liquid reaction method” from mixtures correspond to CaO·Fe203, 2CaO·Fe203, Ca0·2Fe203, 4CaO·Fe0·4Fe2O3, 3CaO·Fe0·7Fe203 and 4CaO·Fe0·8Fe203, respectively. The mineralogical properties of synthesized calcium ferrites, i. e., optical characteristics, reflectivity, etching effect, microhardness and Xray diffraction pattern, were examined. Besides Ca0·2Fe203 compound, a ternary calcium ferrite compound proved to exist, whose chemical composition is approximately similar to Ca0·2Fe203 and is estimated to be one of the followings 3CaO·Fe0·7Fe203, 4CaO·Fe0·9Fe203, or 4Ca0·2Fe0·9Fe203. X-ray diffraction patterns of CaO·Fe203, 2CaO·Fe203 and 4CaO·Fe0·4Fe203 were in agreement with the data of previous workers. For determining metallurgical properties of binary calcium ferrites, about 2kg samples are synthesized by solid state reaction. The conventional testing methods for iron ores were applied, i. e., the JIS methods for testing reducibility, the rotation strength after reducibility test, the degradation strength after reduction at lower temperatures, and the temperature of shrinkage, softening and melting. The degradation strength after low temperature reduction of binary calcium ferrites is much higher than that of actual self-fluxed sinter.
In the analysis of the solidification process of continuous casting operation, the estimation of modifiedFourier number, H2=αL/uW2, which determines the quantitative relations between the length of thecooling zone and thermal diffusivity, thickness and withdrawal rate of the ingot, has been facilitatedby the adoption of the integral-profile method. The calculus for continuous casting presented in previous paper by considering the completion offreezing of metals at the end point of the spray cooling zone has been improved and developed tothe new calculus, in which the complete solidification at the position of pinch rolls was taken intoaccount and another dimensionless factor, H3=αLp/uW2 was introduced. The values of H2, m in and H3, min derived theoretically in this work may be used as the standard onesin decision of the length of cooling zone and the operating conditions. The values of residence time in cooling zone calculated for three kinds of steels under various coolingconditions have been in good agreement with the estimated values which were presented in other papers, hitherto.
The dissolution of silicon into the solid iron was studied at PH2=1 atm, 1150-1300°C by the aid of silicon monoxide gas. The results obtained are as follows: 1) Unlike siliconization with silicon halide atmospheres, the weight of specimen after the present siliconizing treatment increased and the siliconized layer obtained was free from holes. 2) In this siliconizing method, the rate of dissolution of silicon was mainly controlled by the transportation of SiO (g) in gas diffusion layer. 3) An apparent activation energy obtained from the temperature dependence of the mass transfer coefficient, kG was 16kcal/mol.
The serrated flow, the Lüders bands and flow stress observed in Fe-23%Ni-0.24%C martensite during tensile test were studied at various temperatures between-196 and 220°C. The results obtained were as follows: (1) Temperature dependence of flow stress of the Fe-Ni-C martensite was explained in terms of the rearrangement of carbon atoms due to Snoek type or Cottrell type pinning, or of the clustering of carbon atoms or the precipitation of fine carbide particles on dislocations. The strain hardening at the early stage of deformation was remarkable in the martensite. (2) Serrated flow was found at a certain range of the test temperature. The temperature range varied with the strain rate. For example, the serration appeared between 1 and 170°C for the strain rate of 5.6×10-4/sec. At this temperature range, the increment in 0.2%-flow-stress was observed, but the strain hardening during serrated region was not so much. (3) The distinct Luders bands were observed during serrated flow. One Lüders band corresponded to one stress drop of the serration. The characteristic of Lüders bands in the martensite differed from that of annealed mild steel. The finer Liiders bands were uniformly distributed in the martensite, the larger total elongation was observed. (4) From the analysis of the critical condition for the serration, it was found that (a) a certain degree of plastic strain was necessary for the serrated flow to occur and (b) each step of yielding during serrated flow was an independent process of dynamic strain aging and was associated with the occurrence of one Lüders band.