Using Zungun ore as raw material, the specific effect of additives on the sintering processes and sinter properties were studied with a small Greenawalt-type sintering machine. Additives to the sinter mixture were lime, limestone, calcium hydrate and open hearth slag. The results obtained were as follows. (1) The beneficial effect of lime, limestone and calcium hydrate increased to a limit of 4% and finer additives were more effective. (2) For using these additives, it was understood that the moderate moisture was given the sufficient strength. (3) By using the open hearth slag, the strength of the sinter were very increased. (4) By using these additives except the open hearth slag, the reducibility of the sinter were increased. (5) From observation of mineral constituents by a microscope, it was found that composition and nature of matrix in the sinter had influenced the strength and reducibility of the sinter.
The equilibrium of reaction 2CuO(s)+Cl2(g)=2CuCl(l)+O2(g) was measured by flow method. The equilibrium was approached from the two directions of the forward and the reverse. The results obtained for the temperature ranges 488°C and 529°C was as follows: It was observed that in the above reaction, the reaction rate of the forward direction was very large. It was found that the mechanism of the chlorination of CuO followed the undermentioned stages: (1) (2) (3) and the reason for large reaction rate was due to the fact that the second and the third stages occurred simultaneously.
In order not to increase the oxygen content of the steel bath, extra-low carbon rimmed steel must be melted by slag of the basicity as low as possible, and moreover the sulphur must be removed effectively and opportunely by that slag in the basic open hearth process. Consequently the rate and the period of desulphurization in the process were so important that test melts A (charged 6T lime in 113T), B (charged 4T lime in 113T) and C (charged 5T lime in 113T and poured sand before pouring Mn) were melted in a 100T basic open hearth, and change of -ds/dt, (s)/s, excess base, fluidity of slag and slag composition for time in the process were investigated and best method of melt was discussed. 1) In melt A, charged lime floated all at once about 10mn. before melt down and the rate of desulphurization was the greatest, and max. rate was attained to within 20mn. after melt-down. But in melt B and C the max. rate was attained to about 40mn. after melt-down and the rate of desulphurization was low. 2) In melt A, excess base increased rapidly from 10mn. before melt-down and its value was 0.2-0.3 at melt-down and did not increase remarkably in the refining period. On the other hand, in melt B, the value of excess base was <0.1 at melt-down and increased remarkably in the refining period, In melt C, it was half-way between A and B. So it was recognized that in the basic process when charged lime was increased to 6T, the rate of desulphurization was the greatest and the max. rate was attained to within 20mn. after melt down. But when more lime was used in the refining period, the basicity of slag at before pouring Mn increased. So it is necessary to control the basicity as follows: 1. In refining period, lime must be used as little as possible. 2. Slag before melt down in which FeO content is much must be used effectively. 3. Basicity must be risen at the beginning of refining period. 4. C-O boil must be used effectively in desulphurization.
As stated in the Ist Report (Tetsu-to-Hagané 1958 No. 1, p. 9-14), bars used for bar-test of measuring axial solidification rate of large steel ingots became thick due to the adhesionof solidified metal. Cutting the adhered metal layer-by-layer from their surface, it was found that certain layer of this metal, that was 1.5-2.5mm deeep after removing surface oxidized zone, nearly coincided with the melt of the depth at which the bar had been stopped for marking for a few seconds. By taking samples from this specific layer at every 400-600mm, the vertical segregation proceeding in the melt of the ingot core was qualitatively caught (Fig. 5, 6 & 7).
In the third report, the authors studied the relation between the sand marks of steel rods corresponding to the shrinkage head of an ingot and that of the ingot itself, and also the relation between the sand mark and non-metallic inclusions, which was extracted by chemically. The sand mark was examined microscopically. The results were briefly summarized as follows: (1) The number of sand marks, large and small, of steel rod, which was prepared from the shrinkage head of the ingot, is numerous, but the number of sand marks of a normal steel rod, which was rolled from the ingot itself, was small. (2) Weight of chemically extracted non-metallic inclusions at where sand marks are gathered into a certain position of steel rods was larger than that of another position of the steel rod. (3) Generally, the weight of the chemically extracted non-metallic inclusions at the center of steel rods was larger than that at the periphery of the same steel rod. (4) By microscopic examination, mostly, the non-metallic inclusions existed in the sand marks. (5) Segregation sand marks, which were caused by phosphorus and sulphur, were rarely found in the high-carbon low-chromium steel rod.
To investigate the influence of the carbon on the properties of 18-4-2 type high speed steel which were used for forming or finishing cutting tool, the authors measured the critical temperature, Ms point, quenched and tempered hardness, retained austenite, dimensional change, toughness and mechanical properties at high temperature. The results obtaned were as follows: (1) The critical temperature and Ms point were lowered with the carbon addition and the beginninig curve of the isothermal transformation was moved to long time side with the carbon addition. (2) The quenched hardness was raised with the austenitizing temperature in the lower carbon content and was lowered as the carbon increased to more than 0.76%. For obtaining the fully quenched hardness, the austenitizing time needed about 1 or 2 minutes for 16 φ×10mm specimen. The tempering hardness as the secondary hardening was raised with the carbon addition and with the quenching temperature elevated. (3) The quantity of retained austenite measured by the magnetic method increased with the carbon addition. During the tempering, decomposition of the retained austenite was occurred at about 500°C rapidly and all amount of them was entirely decomposed between 575°C to 600°C (4) The toughness measured by the static bending test decreased with the carbon addition and the impact strength at elevated temperature also decreased with the carbon addition. The tensile strength, elongation and reduction of area at elevated temperature were hardly affected by the carbon addition, but were affected by the tempering and testing temperature.