The authors tried to prepare the pellet of high strength with using pyrrohtite as binders (several percentage of them being added), and compared them with those pellets that contained limonite as binders. Testing of pellets comprised a compression test, a drop test, specific gravity, porosity and chemical analysis. With this experiment the next conclusions were obtsined: (1) Mixing 5-10% pyrrohtite powder to iron ore fines, high strength pellets were prepared. (2) Heating temperature was lowered by 150-200°C, as compared with the case of the ordinary manufacturing of pellets. (3) Sulphur in pellets did not exceed 0.1%. (4) Pyrrhotite was found to be a very powerful binder as compared with limonite, and the cost of agglomerationwas lowered with these binders.
By constructing the following electrode concentration cell and by a potentiometer, authors measured the electromotive force corresponding to the change in the manganese content in iron: +, Fe-Mn|SiO2-MnO-CaO-MgO|Mn- The temperature of the experiment was about 1, 590±5°C and for the measurement of temperature, a Pt-Pt/Rh thermocouple was used. The theoretical relation between the electromotive force E (V) and the activity of manganese, aMn was as follows: (1) where aiMn=the activity of manganese ion in the molten slag a'Mn=the activity of pure manganese when pure manganese was selected so as to be in a standard state, the following equation was obtained from eq. (1): (2) n was approximately determined as n=2 by a calculation from the authors' data. From eq. (2) the activities of manganese were determined for all over the range. From the authors' result, Fe-Mn binary solution was recongnized to be approximately an ideal solution in all over the range. Judging from considerations made from several points of view, Fe-Ni and Fe-Co binary solution were also considered to follow the Raoults' law as in the case of Fe-Mn binary solution.
The authors stndied on the distribution of sand and the causes of it concerning silicon or silicon-aluminum killed low-carbon Cr-Mo steel ingots which were melted with an Héroult electric furnace. The results obtained were as follows: (1) Ingot No. 1 (which was deoxidized with manganese and silicon in the furnace.) Content of sand was at minimum at the outside and it increased as the inspection went inside, but MnO/SiO2 and (FeO+MnO)/SiO2 in it showed a reverse change against the above results, while FeO and MnO decreased and SiO2 increased as the inspection went inside. But the sand content was low at the center of ingot top. The sand at the outside of ingot where the total amount of the sand small, had no-constant forms and were very large, but as the inspection went further inside they became spherical and very fine in size. It was concluded that the large sand at the outside of ingot were not deoxidation products produced in the mold but most of it had been included in the molten steel just before casting. These large sands were not found at the inside, and as the inside portion was cooled slowly in comparison with the outside portion, it could be supposed that these large sand floated up in the mold during solidification. On the other hand, the total content of sand showed the maximum value at the inside and their form was finely spherical and as SiO2 increased but FeO and MnO decreased in their composition in comparison with the inside. It was concluded that this fine and spherical sand at the inside were deoxidation products produced in the mold during solidification. (2) Ingot No. 2 (which was deoxidized with manganese and silicon in the furnace and added to aluminum in the ladle.) Content of sand was at maximum at the outside and it decreased as the inspection went inside but at the neighbourhood of the bottom it did not show a low content. This sand was composed of Al2O3, and then SiO2, FeO and MnO in sand were very few and had fine and no constant forms. It was concluded that this sand was deoxidation products by aluminum and most of it was not produced in the mold but in the ladle.
The present report supplys some data on the recrystallization softening of cold-rolled alloyed iron and steels, with'a point of view to survey the effect of the alloying elements on the rigidity of steel at high temperature. The samples were prepared by induction melting in magnesia-lining crucibles, using 0.08% C Swedish steel and the best grade of metals or ferro-alloys as the alloying materials. After complete annealing, these alloyed iron bars were subjected to cold rolling of 20% and 50% reduction in thickness. And Brinell hardness tests were carried out upon the sections of these rolled bars, which were reannealed at various temperatures (300 to 1000°C) for a constant period of time (2hr), and also at a constant temperature (550, 600, 650 or 700°C) for vafious periods of time (2min to 100hr). The results obtained were shown in Figs. 1, 2, 4 and 5, from which the following conclusions were drawn. (1) Nb, Ti, Mo, W, V, Cr and Co raised the recrystallization temperature, and retarded the softening of steel accompanied by annealing. (2) Ni, Mn, Si, Al, Sn and P hardly changed the range of softening temperature of ferritic steel. (3) Cu, added more than the solubility limit for iron, raised the softening temperature of steel. (4) Cold rolled 0.65%C steel having spheroidal structure was easily softened than the lamellar one by annealing. (5) High Ni-or high Mn-steel having austenitic structures showed higher softening temperatures than the ferritic ones.
(1) The author made clear the influences of N & Cb on the properties of LCN-155, S-816 and the similar samples, studying their microstructures as cast and forged, the changes of hardness and structure by solution-treatment, ageing and hot-cold working, their mechanical properties at room and high temperatures, argon arc welding results with the similar electrodes, and researching the micro-hardness of their structure constituents and the electron microscopic structures, when necessary, at last he gave the equibrium-diagramatic aspects on these results. (2) At the melting of these samples, the mean of the yielding of Cb was 75%. (3) The influences of Cb on the micro-structures as cast are as follows; in LCN-155, the eutectics appear considerably when Cb was added over 1.0%, and in S-816, they increase remarkably as Cb increases and occupy the area of 1/4-1/3 of the observed field when 6% Cb was added. (4) In the samples as cast and forged, the micro-hardness of the deep etched primary austenite is equal to or a little lower than that of the light-etched austenite around the eutectic, and that of the eutectic, equal to or a little higher than that of the austenite around it. When N and Cb increase, the micro-hardness of each structure constituent increases. (5) When solution treatments at 1, 000-1, 200°C are carried for 10hr, a little decrease or no decrease of hardness at every temperature is observed in the samples with Cb compared with the ones without Cb, that is to say, the formers are better in stabilization. When aged respectively at 600-900°C for 30hr, the hardness decreases rather at 900°C frequently. The suppression of age-hardening by Cb are observed considerably, but there are some examples not so clearly observed. (6) The hot-cold work tests was made as follows; after tensile-loading appropriately at high temperatures on the test-pieces which are tapered at the place of parallel gauge parts, the loads per unit area, the contraction of area, the hardness and the grain size, at every cross-section of the tapered part, are measured. No monistic change between them is acknowledged, but the difficulties in working are felt a little by addition of N and almost always by increase of Cb. In the former the degree of hardening increases, and in the latter no notable differences or a little decrease are acknowledged as the degree of working. The grain sizes become not always finer as the working amount or N content increases, due to the influences of stress-relief-annealing. (7) According to the high temperature mechanical tests of LCN-155, the tensile strength at room temperature-800°C decreases about 5-2kg/mm2 by addition of 1% Cb, but recovers generally by addition of about 0.12% N, and no remarkable change is seen when Cb was added moreover. Also, in S-816 and the similar samples, the strength at room temperature-900°C decreases by addition of Cb over about 4%. (8) The author illustrated the above results in considering that, to C, Cb has the most affenity and, to Cb, N has more affenity than C, and that, (Cr, Fe, W, Mo)23 C6 phase becomes more difficult to harden by ageing, when Cb solid-solves in. The results that the eutectics increase remarkably by Cb in the structures as cast was illustrated, too, by assuming the equibrium diagram. (9) By welding tests, the surfaces of the deposits as welded become more bright as Cb increases and have an appearance as like being polished electrolytically when Cb was added over 6%. To the hardness distribution of the sections of the deposits, Cb has no distinct influence. In the micro-structures, so much influences are not observed except that the eutectics in the deposits increase by Cb. The tensile strengths of the welded samples are considerably lower than that of the forged samples at room temperature, but the difference between them becomes smaller at higher temperature.
Side-blown baby-bessemer converters are employed in foundries for the production of steel castings, in U.S.S.R. recently, however, a large number of this type of converters are also used for the production of steel ingots under a new name of "Soviet Union's Process." And also, they assert that steel made by the side-blown converters have lower gas content and higher resistance to the low-temperature shortness than the others made by the open hearth furnace. The distinctive point of this new process is to use the over-heated low-Si molten pig iron (0.3-0.5% Si, 1400-1450°C) in the converter. Therefore, it seems to be nearly identical with the old Swedish process, but they maintain that it is their own process. Normally, in the baby-bessemer process, or in the high-or medium-Si process, they refine hematite pig iron, which is usually melted in usual cupolas. In works producing steel ingots by this new process, however, the cupolas are of a special design and the charge employed contains high percentages of steel scrap (90-95%), which is partially recarburized before blowing in the converter. From the results of several practical studies on the high Si Process (>1.6% Si), the medium Si process (1.1-1.6% Si), the low-Si process (<1.0% Si) and this new process by a 1.5t converter in each, merits of this new process were pointed out as follows; a) The shortening of the blowing time. b) The lessening of the blowing-loss of molten metal. c) The increasing of the steel scrap in the raw material of cupola. In the Chinese communist region, lately, in some works this type of converters are also used for the production of steel ingots, and they are blowing the comparatively lower Si molten pig iron (0.8-1.2% Si, 1300-1350°C) in the converter. It may be said that, from the great demand of steels in that region, this simple process will be developed more and more in future.