Limonite, prodnced in Hokkaido, contains arsenic. As arsenic cannot be removed during the refining process in both blast furnaces and open hearth furnaces, it must be removed during the ore benefication process. Therefore this investigation is conducted to find out the effect of atmosphere on the removal of arsenic in limonite during the ore roasting process, one of the ore benefication processes and the following results are obtained. (1) Arsenic in limonite exists as Scorodite (FeAsO4·2H2O) (2) The effects of atmosphere on the removal of arsenic in limonite during ore benefication Process are as follows: (a) CO gas is very effective to the removal of arsenic and only about 5% of CO cohtent in the atmosphere accelerates the arsenic removal reaction. (b) N2, a neutral gas, has no effect on the arsenic removal reaction. (c) CO2 gas has a weak hindering action on the arsenic rewoval reaction. (d) O2 gas has a strong hindering action on the arsenic removal reaction. (3) Under the conditions of ore size of -100 mesh (As 1.91%, 5.12%), heating temperature 900°C, heating time of about 20mn and in the atmosphere of waste gas from incomplete combustion (CO 5%, CO2 15%, N2 80%), high arsenic removal ratio, about 97%, is obtained. And under the conditions of sample ore size of 17mm, heating temperature of 900°C, heating time of about 1h and in the atmosphere of weak reduction, containing about 10% CO, 95% arsenic removal ratio is obtained. (4) In the case of removal of arsenic in limonite by a weak reduction atmosphere, good arsenic removal ratio is obtained when it is reduced to the artificial magnetite.
The rate of decarbonization in open hearth furnaces has been discussed mainly with carbon and excess oxygen contents, and ΔO in molten steel. But it is also necessary to consider the rate of movement of oxygen from slag to molten steel and the rate of running away of CO-bubbles. The author restricted this problem within the rate of movement of oxygen from slag to metal. Oxygen content, O'equ in iron, which was in equilibrium with slag, was newly used for oxygen potential of slag, and oxygen content, O in molten steel was used for oxygen potential of metal as before. Then it was assumed that the difference of them, ΔO'=O'equ -O gave not only the oxidation power of slag to metal quantitatively, but also the measure of moving speed of oxygen from slag to metal. In the open hearth furnace, the value of oxygen potential of metal, O was between O'equ and Oequ (equilibrium value of O by the curve of Vacher & Hamilton), because carbon boil continuously occurred in molten steel. In this state, the potentiality of decarbonization was controlled by ΔO, and ΔO' made up for decrease of ΔO by the speed equal to the speed of decrease of ΔO. Then the speed of decarbonization was controlled by the speed of formation and growth of CO-bubble nucleus. Under this assumption, the change of O'equ and ΔO' were examined in our 100t basic open hearth furnace (C; 0.08-0.80%), and moreover the change of O and ΔO in low carbon range were examined. The following results were obtained. (1) In the refining period in which carbon contents dropped from 0.80 to 0.08%, O and O'equ was increased and moreover ΔO' was increased as the carbon was eliminated. (2) Accordingly excess oxygen, ΔO in steel was increased as the carbon was eliminated.
The authors studied the vacuum ingot-casting from June, 1955. The first degassing unit was put in operation in September 1957, and, in addition, 3 units were developed. At the present time, they can make 4 ingots with 6t to 20t continuously. Special features of vacuum ingot casting process are as follows: (1) The oxidation of the pouring stream and surface of the steel are prevented as there is no oxygen in the vacuum chamber. (2) When the steel enters the vacuum, the steel stream is divided up into little drops with diameter of 1μ to 10mm. (3) The sources of hydrogen from bricks and patching are eliminated. (4) There is a greater latitude with regard to the pouring speed. (5) The scum and non-metallic inclusions are floated by the violent boiling and bubbling. (6) Under the vacuum 2mmHg to 5mmHg, 60% of hydrogen and 30% of oxygen are removed.
With the aid of a lot of materials picked up at the production plant as samples for microphotography, an investigation was made to try to study statistically the relation between the microstructure and the mechanical properties (ductility and toughness) to clarify the effect of acicular pearlitic structure recognized in normalized medium carbon steel on its mechanical properties. The results were summarized that the mechanical property varied according to the microstructure and the microstructure, in the course of becoming coarse, made both its ductility and toughness decreased and the standard deviation of the impact value increased. At the same time the ultrasonic transmissibility was investigated on various microstructures made by the laboratory treatment by which the relation between the microstructure and the apparent ultrasonic attenuation coefficient became ascertained.
The materials for permanent magnets exhibit high coercive force and residual induction. The coercive force is called magnetic hardness and materials with high coercive force are in general mechanically hard. The study on the relation between magnetic and mechanical properties of materials for permanent magnets is important of commercial fabrication. The materials now in use are classified metallographically into some groups and these workability is studied. In this paper, quench-hardening magnet steels, γ-α transformation magnet alloys and order-disorder transformation magnet alloys are studied. In quench-hardening magnet steels, coercive force is proportional to square root of the volume of retained austenite and the best valne of magnet is obtained, when fine particles of martensite needles are distributed in the retained austenite and the ratio of martensite to austenite is 2 to 1. The magnet steels are mechanically hard in the quenched state, but are machinable in the annealed state withont martensite structure. In the γ-α transformation magnet alloys, γ phase transforms to α phase during cold-working and some α phase is converted to γ during aging. When γ is dispersed highly in α, the coercive force of materials increases. In the simple γ-α transformation alloys, mechanical hardness decreases lineally with the precipitation of γ. In the γ-α transformation alloys with meta-stable order structure, the mechanical hardness increases rapidly with transformation of disorder α to meta-stable order α', but depends hardly upon the precipitation of γ. These alloys are necessary to machine after cold working and ageing. In order-disorder transformation magnet alloys, coercive force increases remarkably during aging, bnt mechanical hardness slightly. The workability of the disordered state is easier than ordered state. The workable state of transformation type magnet alloys is a disordered γ phase- and when this disordered γ phase exists in room temperature, the coldworking is possible.
This investigation was undertaken to find rapid and accurate chemical methods for the analysis of basic slag. In the report (II), a simple spectrophotometric or volumetric methods is described for determination of FeO, Fe2O3 and TiO2 which are contained in basic slag. Determination of Fe2O3: Dissolve the sample with HCl, and dilute to about 100ml. with water. Adjust to pH 2.0 with ammonium acetate, and titrate with EDTA using salicylic acid as an indicator. Determination of FeO: In the same solution, add NH4S2O8. Mix and titrate with EDTA. Determination of TiO2: A simple and selective procedure has been developed for the spectro photometric determination of TiO2 in the presence of other metals by using EDTA and salicylic acid. The reaction between Ti and salicylic acid at pH 4-5 to produce the yellow colored-complex was chosen for application. At pH 4-5 Mo, Nb, Th, Mn, Al, Pb, Ca and Mg do not interfere. Fe, Cu, Cr and V may be masked by the addition of EDTA.