The following four measurements have been carried out by the oxygen concentration cells with the solid electrolyte, ZrO2·CaO at the temperature range of 1000°C-1550°C. (1) Oxygen pressure in the iron equilibrated with FexO by Ni+NiO|ZrO2·CaO|Iron+FexO. (2) Oxygen pressure in the liquid iron saturated with graphite by Ni-NiO|ZrO2·CaO|Liquid Iron+Graphite. (3) Oxygen pressure in the liquid iron of intermediate carbon range by Graphite |ZrO2·CaO|Liquid Fe-C-O System at 1550°C. (4) Change of Oxygen pressure in liquid iron during deoxidation by Al, Si, or Mn at 1550°C by Graphite |ZrO2·CaO| Liquid Fe-O System. From the results of these measurements, the following conclusions have been obtained; (a) The standard free energy for formation of FexO, calculated from the measured EMF agreed very well with the data in literatures. This agreement suggested a 100% ionic conduction at least up to 1550°C for the ZrO2·CaO electrolyte (PO2≈10-8 atm at 1550°C). (b) The measured EMF was smaller than the calculated EMF for the iron saturated with graphite, possibly due to some electronic conduction. (c) This cell can be used to determine the oxygen content dissolved in liquid iron of intermediate carbon range at steel-making temperature. (d) From the very rapid decrease of the EMF after the addition of dleoxidizers, it was known that the rate-determining step of deoxidation of steel was separation of the reaction products, such as Al2O3, SiO2 and FeO-MnO. In addition, the solid electrolyte MgO was used to compare the performance as an anion conductor.
The authors measured resistances to deformation, “Kf”, of low carbon steels, with contained 0.02-0.09% carbon, nickel and 0.0-1.5% chromium, and of an ultra low carbon 2% Al iron at various temperatures i. e. from room temperature to 1, 000°C. The order of strain rate was of 102/sec. Deformation was done by a “Counter-blowing” type forging tester. The results are as follows. (1) Below 500°C., the strain-rate and temperature dependence of the “Kf” are large. The value of log Kf/ log ε is about 0.2. The difference of “Kf” between at room temperature and at 500°C. reaches 25-30kg/mm2. It is concluded that this phenomenon has the same nature as that of yield and flow stress of iron below room temperature at low strain rate i. e. 10-4-10-3/sec. It is also found that thetemperature dependence of “Kf” of some 0.05% carbon steels containing nickel, 0.02% carbon steel and 2% Al iron decreases between 100°C and room temperature. However, the reason is yet unknown. (2) From 500°C to 600°C, “Kf”-temperature curves show a peak in the case of carbon steel. It is concluded that at this strain rate and temperature the velocity of moving dislocations is favourable for the dislocations to be dynamically locked by Cottrell atmosphere, the need of dislocation multiplication increases, and therefore, work hardening rate is much larger than at other temperature. It is also found that the strain-rate dependence becomes 1/3 smaller. (3) This phenomenon is disscussed from the point of view of the interaction between interstitials and dislocations, whereas the dragging mechanism does not seem to explain it well. (4) At γ-α coexisting temperature range, no peak of “Kf”-temperature curves is found at strain ratt -102/sec., but a peak is found at lower strain rate. It is concluded that as the strain-rate dependence of “Kr” of α-phase is 2-3 times larger than that of γ-phase, any peak is not found at the higher strain rate. (5) The strain-rate and temperature dependence of “Kf” of the 2% Al iron are very small between 500°C and 900°C. Above 900°C., they become larger, and it seems reasonable to think that self-diffusion or recovery becomes effective for deformation process.
Authors have reported in the preceding study, as part of a study on super alloys for springs, on the spring properties of Refractaloy 26 type alloy. This time, they investigated the spring properties at the room temperature and elevated temperature of Inconel X type alloy. This alloy was treated under various combinations of solution temperature, solution time, aging temperature, aging time and cold reduction before aging. Characteristics at the room temperature were determined by hardness, tensile, grain size or deflection tests to confirm the spring properties. Spring properties at the elevated temperature were investigated using coil springs subjected to an optimum solution treatment, aging treatment, and cold working. Compression coil springs were manufactured for this investigation and heated from room temperature, with the temperature and deflection registered, then the modulus of rigidity and proportional limit in twisting at high temperature determined. To confirm the stability of deflection under load and heating, coil springs were heated and cooled cyclically. Also the micro-structure and the process of precipitation were observed with the help of electron-microscope. Results obtained were as follows; 1) A combination of 982°C (solution treatment) and 704°C × 9-44 hr (aging treatment) develops better mechanical properties at room temperature than any other combination. 2) Maximum mechanical properties at room temperature, under a combination of cold working and aging treatment, can be obtained with lower aging temperature and shorter aging time. 3) The aging treatment and cold working do not affect the modulus of rigidity. 4) The proportional limit in twisting is influenced by the aging temperature, aging time and cold working. It hardly goes down up to about 600°C. 5) Permissible stress for this alloy is up to about 40kg/mm2 for one strengthened by cold working and aging treatment, when the upper temperature of reversed cyclic heating is about 400°C.
In relation to classical reserves of high grade iron are in India, the reserves of good metallurgical grade of coking coals are extremely limited and that too confined to in the Bengal-Bihar belt. The development of small and medium scale iron and steel plants depends on the exploitation of sub-standard raw materials particularly the fuel unsuitable for conventional smelting in big blast furnaces of a million tonnes integrated iron and steel complex. The Low Shaft Furnace Pilot Plant installed at the National Metallurgical Laboratory, Jamshedpur (India) is designed to operate on sub-standard raw materials and non-metallurgical fuels for iron smelting. In 5-6 years of extensive and painstaking trials, a great variety of raw materials have been investigated on a comprehensive scale. It has been established that technological, operational and economic considerations preclude the adoption of a single stage process based on the smelting of single component burden of ore-fuel-limestone briquettes. The operational complexities and non-recovery of potential by-products have rendered the direct utilization of non-coking coals for iron smelting as lumpy bedded charge also impractical. The use of low temperature carbonized coke made from noncoking coals has enabled effective furnace operational control and uniformity of pig iron output of consistent composition. Carbon saturation of pig iron in initial trials was found to be low which depended on the basicity and MgO content of the slag. The effects of changes in the basicity of slag on carbon, silicon of pig iron, sulphur partition and on technical aspects of smelting, flux rate and fuel rate were investigated. The effects of particle size of raw materials and the rate of blowing, on top gas temperature, CO/CO2 ratio, fuel rate and dust loss were also comprehensively studied. Dolomite additions were found to improve the slag fluidity but somewhat adversely affected sulphur partition. It has been established that iron smelting in a low shaft blast furnace with low temperature carbonized coke can be successfully adopted in areas where coking coals reserves were limited.