It is very difficult to examine the behaviour of gas in blast furnaces not with a model but with an actually operating blast furnace. However, a German-type gas-sampling equipment was installed on the shaft of No. 1 blast furnace in Kokura Steel Works, Sumitomo Metal Industries, Ltd., so it was possible to examine the behaviour of gas in the shaft with the equipment. While there was no such equipment on No. 2 blast furnace, so that a simplified-type gas-sampling equipment was installed and the behaviour of gas in the blast furnace was examined. Results obtained were as follows: 1. The distributions of CO2, gas temperature and ascending gas velocity etc. were different for each furnace. 2. The behaviour of gas changed in company with combination of burden. 3. The reducibility of each part in the blast furnace changed in company with combination of burden. The reducibility of the lower part with 100% self-fluxing sinter burden was higher than that with 100% raw iron ore burden. 4. About 25% of CO in the gas-passing through the part where the gas-sampling equipment had been installed was consumed for carbon deposition and about 5% was consumed for reduction of ore between the part and the top. 5. The behaviour of shaft-gas in abnormal state was roughly known, e.g. the CO2 content in the ascending gas increased during the hanging.
The equilibrium of silicon and oxygen dissolved in liquid iron was studied at temperatures of 1570°C, 1625°C and 1680°C respectively. Fe-Si alloys were melted in pure silica crucibles in the H2-H2O gas mixtures for 10-20h. Silicon in liquid iron increased its activity coefficient even with a low-silicon concentration, while it reduced the activity coefficient of oxygen. The products of silicon and oxygen were nearly constant in the range of 0-3.0% silicon. These data obtained were summarized as follows: 3. The interaction parameter of silicon in liquid iron, e'Si: 4. The effect of silicon on the activity coefficient of oxygen in liquid iron, e(Si)0: 5. The activity coefficient of silicon in liquid iron with a very low silicon concentration (in mole-fraction), γ°Si:
The present investigation was performed for the purpose of obtaining the fundamental knowledge of the vacuum-melting practice on crucibles, stamping refractories, erosion of crucibles, ingotism etc. Furthermore, the change of the contents of gases and metallic constituents in pure iron during vacuum-melting, and the recovery of added elements in stainless steels were also investigated. The results obtained were as follows: 1) Pure iron was melted and held in vacuum in the four kinds of electro-magnesia crucibles, and the changes of content of various elements were plotted against the holding time. It was proved that within 1h. all of the crucibles tested were comfortable. Crucible B'-1 was most excellent and the oxygen contamination was not observed within 2h. at 1600°C, but the content bf oxygen was increased when the melt was kept at 1700°C for 30mn. 2) The results of the refining method of pure iron melts by hydrogen gas showed the higher content of hydrogen. 3) The content of oxygen was sufficiently decreased by immersion of the graphite rod into the melt, but the content of carbon was increased rapidly. It was thought, therefore, that the control of the content of dissolved carbon was very difficult. 4) By the appropriate modification of the mold design, the ingotism could be improved. 5) Stainless steels were satisfactorily vacuum-melted by the method in which the addition of silicon and manganese were carried out under the pressure of 20mmHg of argon to prevent from their vaporization loss.
A series of experiments on the primary cooling of continuous casting of steel was carried out. In this report it is defined that the solidification in mold is "the primary solidification" and the cooling of this stage is "the primary cooling" and that the solidification in spray zone is "the secondary solidification" and the cooling of this stage is "the secondary cooling". Based on the principle of normal ingot casting, it was presumed that main factors affecting the primary solidification of continuous casting should be as follows: Shape of mold Evenness of cooling in mold Casting temperature Casting speed Experiments on the effects of these factors on continuous cast billets mainly of square type reveal the following facts. (1) Corner radius of mold affects longitudinal surface cracks of square billets. There is a suitable corner radius for each size of billets to get rid of surface cracks. (Fig. 1) (2) Unevenness of the primary cooling induces longitudinal cracks on the surface of billets. (Table 2) (3) Too high casting temperature induces longitudinal cracks on the surface of billets. (Fig. 2) These relationships in continuous casting are just same as those in normal ingot casting. (4) Commonly, casting speed does not affect continuously cast billets. But exceptionally in round billet, too high casting speed induces longitudinal cracks on the surface of billets. (Table 5)
The nature of carbides in Mo high speed steels (0-9-4-2, 6-5-4-2) and in Co high speed steel (18-4-1-20) were studied by electrolytic isolation method, with a view to clarify the role of Mo and Co in high speed steels. Carbides present in Mo high speed steels were M6C, M23C6 and MC, likewise in the case of W high speed steels. The density of the carbides in Mo high speed steels was smaller than that of the carbides in W high speed steels, and so the percentage of carbides by weight in the former was smaller than that in the latter. By austenitizing treatment, the carbides in Mo high speed steel were dissolved into matrix readily than the carbides in W high speed steel. Co high speed steel contained only a kind of carbide, M6C. This carbide was usually hard to be dissolved into austenite. But the addition of Co in high speed steel had the effect of enlarging the solubility limits of W, Cr, V and other carbide forming elements in austenite, and served to promote the dissolving of M6C during austenitizing.
Interest has existed among high-temperature alloy producers in utilizing leaner alloys than are currently used. Nitrogen-bearing austenitic alloys offer possibilities in this respect. An investigation has been made of the hot-strength potentialities of 316L type alloys melted in vacuum, in air or in nitrogen of two atmospheric pressure using an induction furnace. It was presumed that the relation between the partial pressure of nitrogen in the melting atmosphere and the nitrogen content of these ingots deviates markedly from Sieverts' law. Comparing with air-melted and vacuum-melted steels, the nitrogen-melted steel showed higher hardness and strength at room temperature in any states such as solution-quenched, solution-quenched followed by cold-working, or solution-quenched followed by hot-cold working. For the nitrogen-melted steel, significant resistance to recrystallization-softening and excellent properties in both the high-temperature bending creep and tensile creep-rupture tests were also found. On the other hand, vacuum-melted steel showed in a tensile creep-rupture test longer life and larger elongation than those melted in air, although it had less hardness and resistance to recrystallization-softening than air-melted one. It was also investigated how the sort of raw chromium used in melting influenced on the steel properties, and the bending creep property was found to be improved in the case of the steel prepared from Thermit-process chromium than in the case of that from electrolytic chromium.
Heat treatment of type 321 stainless steel tubes for high-temperature service must be carried out based on the different standpoints from those for use in chemical industry. The effects of heat treatment on its creep rupture strength of the 321 type stainless steel were studied for such a use as given in this report. The excellent creep-rupture strength was ascertained to be obtained by the complete solution-treatment of titanium carbide into austenite at a high temperature, thereby the quenching-temperature of more than 1100°C was concluded duly recommendeble for industrial heat treatment. Moreover, the specimens containing a lot of ferrite in austenite were confirmed to show the creep-rupture strength lower than those having only a single austenite phase.