In the first paper ("Tetsu-to-Hagane" vol. 41. No. 1. 1955, p. 5-11) the authors reported of the inyestigations made on reduction process of iron ores by the reformed natural gas. It was found that the decomposition of hydrocarbon in natural gas was one of the most important factors of the reduction process of the ores. In the present paper are made the studieson the effects of reacting time and of some additions such as salts of alkali and alkaline earth metals on reduction velocity of iron ores by natural gas at low temperature. The results obtained were summarized as follows: As the reducing action of natural gas was weak, the time for sufficient reduction should be much longer, but when decomposition of hydrocarbon took place, reduction velocity was found to be rapidly increased. The additions of Na2CO3, CaCO3, and CaO were effective to increase the reduction velocity of the ores by natural gas. Through our experimental results, it was presumed that the decomposition of natural gas was accelerated in consequence of the effects of the additions on reducing power of the gas.
To clarify the differences in the reducing behavoirs according to the composition of pyrite cinders, the cinders were investigated as follows: (1) Reduction efficiency on the reaction of CO gas and pitch coke. (2) Measurement of the permeability (A. F. A) at various high temperatures. (3) Compared with the surface conditions of cinder grains by electron microscopic examlnation. (4) Measurement of the surface area by Bet process:
As the first step of the studies on the production of calcium silicide, the authors investigated the composition both of slags and inclusions in it and obtained the following results; (1) Slags produced by CaO as well as CaC2 method always gave a higher value over 100% as the sum of analytical fractions and their properties were very different from those to be considered from the values. But we found that the properties did not depend upon the metallic particles. (2) SiC in the slags of CaO-SiO2-SiC-CaC2-C system was easily determinable by our method in which the sample was heated in air at 800±20°C for several hours before analysis of SiC. (3) From the results obtained by this method, the slags of the above two kinds contained 10-20% SiC and the sum obtained by the usual method could be deduced approximately to 100%. (4) In conclusions we found that a fact had been overlooked that a considerable quantity of SiC was dispersing and followed when the slag was tapping out from the furnace on the normal operations. Moreover the behaviour of SiC was discussed metallurgically.
Behavior of hydrogen liquid steel molten in a high-frequency induction furnace was studied by means of the new vacuum sampling technique and vacuum-fusion method with an improved thermoconductivity method for analysing the specimens. The following discoveries were made: 1) Hydrogen in the liquid steel tended to escape from the surface of the steel bath to atmosphere, and the tendency was intensified when the steel had high hydrogen value. When the liquid steel was covered with slag layer, hydrogen in the steel enriched by H2 or H2O seemed to decrease to some extent, while it decreased rapidly when the slag was taken off and molten steel surface was exposed to air.2) As to the relation between [H] in liquid steel and PH2O in the atmosphere, the equation stated by D.J. Carney, J. Chipman and N.J. Grant could not be applied when the bare molten steel was exposed to atmosphere containing PH2O, because PH2O on the surface layer of the steel was considered to be not the same as PH2O in the atmosphere. Author suggested that the relation should be considered as under steady condition when there was an equivalent flow of diffusion of H2O and H2 in counter directions through the intermediate gas phase which was found between the surface of the liquid steel and the atmosphere. 3) Basic slag seemed to let H2O pass more easily than glass slag .4) Small addition of titanium in liquid steel prevented hydrogen from escaping from the steel specimens on and after solidification
There are two kinds in the steel-making process of the ball bearing steels, namely, small acid open-hearth and basic electric-arc process. The former is adopted mostly in SKF Hofors Bruks, and the latter is the process which is used mostly in Japan and U.S.A. Therefore, the austenitizing behaviour of the above kind ball-bearing steels, made in Japanese steel maker and tubings of SKF bali bearing steel is studied and reported in this paper. The steels, made by the acid open hearth and the basic electric arc process, have the different quenching-sensibility. According to this sensibility, the difference of change in the hardness and the mechanical property is barely, but the ease, with which the cementite goes in solution in the austenitizing state, is very different by the above two kind of process. Namely, the cemente in the electric arc furnace steel goes in solution easily, but it does not go in solution easily under 850°C temperature and goes in solution easily and rapidly above 850°C temperature in the open hearth furnace steel. Secondly, although there are many non-metallic inclusions in SKF tubings of ball-bearing steels, these steels are stable in the austenitizing state, and the quenching sensibility of this steels is dull. This relates to the solution speed in the cementite, and the solution of it is stable comparatively from 800°C to 880°C temperature.
Fumace-cooling is a standard practice for annealing high-speed steels. It constitutes, however, abottle-neck to production because of a long time required for the operation. To expedite and simplify the operation, the authors conducted many experiments. Earlier, stepped annealing or isothermal annealing had been found effective. This time, effectiveness of water annealing was confirmed. The experimental results testify that: 1. Water annealing with the heating temperature 800°C held for 120mn. will effectively soften. quenched high-speed steels with more rapidity and simplicity. The softened degree falls certainly short of complete annealing but comes up well to the hardness obtainable through machihing. 2. Five to six times of water annealiag operations will ensure softening if the following cycle is repeated: water cooling after rapid heating is applied and the heat is held for a brief time. Oil annealing should be recommended for the works of large dimensions or complicated contours.
Studies on carbides in steel, generally, have been carried out as they were in steel matrix. While, recently, some direct investigations of them isolated from steels were reported. The present paper deals with a direct investigation of carbide. extracted electrolytically from a ball bearing steel by chemical analysis, X-ray diffraction method and electron-micro-scopic examination. The electrolysis for extraction of carbide in the present study was carried out under the following conditions: 0·5N hydrochloric acid solution, current density 10mA/cm2, hydrogen atmosphere. The results obtained were as follows: 1) Carbide in the ball bearing steel (1.13% C, 1.42% Cr) annealed at 750°C for 5 hrs contained 7.21% Cr. 2) Cr content of ferrite in the annealed steel was about 0.24%, and that of austenite at 840°C (usual quenching temperature of this steel) was about 0.9%. 3) Cr content of undissolved carbide contained in austenite at quenching temperature increased with the heating time at the temperature. 4) In tempering process of the hardened steel, the carbide precipitated from the matrix (martensite and retained austenite) at low temperature, such as 300°C or 400°C, had nearly the same content of Cr as that of the matrix (1.42% Cr). But the carbide precipitated by tempering at above 450°C had large amount of Cr which increased with the rise of tempera-ture and holding time. 5) Electron micrographs of carbide isolated from the steel variously heat treated such as that from lamellar pearlite, troostite, sorbite, and spheroidized structures, were shown.