The reduction of individual iron ore pellets immersed in coal char was measured at 900°-1200°C for times up to 3h. The results were compared with published data for other iron oxide/carbon systems to evaluate the kinetics of reduction in static beds, rotary and shaft kilns, and in composite pellets. Reaction rates and activation energies measured in these studies were similar to published values obtained with intimate mixtures of iron oxides and comparable types of carbon at temperatures up to 1000°C, where carbon gasification was rate controlling. However, reduction rates for pellets surrounded by char fell significantly at higher temperatures due to the influence of gas diffusion. Reduction rates, for pellets were similar, for both static bed and rotary kiln conditions at 1000°-1150°C, and were decreased by internal slag forma&ion above 1075°C. Reduction was further inhibited above 1150°C by the formation of dense shells of metallic iron around partly-reduced, slag-rich regions, especially towards the centres of the pellets.

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The effect of temperature, silicon and manganese in carbon-saturated iron (0.1%P, 0.05%S) on the dephosphorization and desulfurization was studied by the use of 2Na₂CO₃•Na₂SO₄ flux. The degree of dephosphorization and desulfurization considerably decreased and the evaporation of sodium increased with increasing temperature. As the flux was consumed for the oxidation of silicon, the degree was found to markedly decrease, whereas manganese in metal was found to gradually decrease. The reversion of phosphorus and sulfur was observed after the end of the flux addition.
The behavior of dephosphorization and desulfurization obtained with 2Na₂CO₃•Na₂SO₄ flux was compared with that with Na₂CO₃ flux or 2Na₂CO₃•Fe₂O₃ flux. The degree of dephospliorization for the three fluxes was almost the same, but remarkable evaporation of phosphorus was observed for 2Na₂CO₃•Fe₂O₃ flux according to the acceleration of CO formation by the reduction of iron oxide with carbon in metal. The phosphorus evaporation was also observed for 2Na₂CO₃•Fe₂O₄ flux, but its extent decreased with increasing content of P₂O₅ and SiO₂ in the flux.

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The effect of temperature (1250°-1450°C), and silicon and manganese in carbon-saturated iron (0.1%P, 0.05%S) on the dephosphorization was studied by using the flux of the CaSO₄-CaCO₃ system. It was found that CaSO₄, although it is in solid state, has strong dephosphorization power. The following dephosphorization reaction was derived from the results of EPMA of the products of dephosphorization reaction: 7/2CaSO₄(s)+2P=3CaO•P₂O₅(s)+1/2CaS(s)+3SO₂
The above reaction was found to proceed with increasing temperature. No effect of the oxidation of silicon on the degree of dephosphorization and no reversion of phosphorus and sulfur were observed, but marked sulfur pick-up in metal took place as a result of the reactions of CaSO₄ with carbon, phosphorus and silicon. To use this flux for the dephosphorization of hot metal, all efforts were made to prevent such a sulfur pick-up by the additions of CaF₂, Na₂CO₃ and CaG₂ to the flux.

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Sulfur exists in blast furnace slags in such states as sulfide sulfur S^2-, elemental sulfur S⁰, thiosulfate sulfur SO^2-₃, and sulfate sulfur SO^2-₃. Chemical analysis of these states is hindered by the following problems:
(1) There is no fully established method of chemical analysis for the purpose, and the existing method is time-consuming;
(2) Sampling comes into question as the states of sulfur vary with time; and
(3) Because the sample is pulverized for analysis, the analytical results indicate an average state and the method can not be applied for local analysis of the sample surface, etc.
In order to solve these problems, we carried out chemical state analysis utilizing chemical shift (X-ray exitation), and obtained the intended results. Chemical shift measurement employs, 1) the SK_α process, and 2) the SK_β process. The former process enables the degree of sulfur oxidation to be readily determined from the ratio of S⁶⁺ to S^2- in the slag. The latter permits analyzing the ratios of S^2-, S₂O^2-₃, and SO^2-₄ that may be present. The above methods of analysis have made it possible to identify secular changes in the form of sulfur in the slag or to carry out local analysis of the surface and interior of bulk samples.

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Simulation by plasticine is carried out to estimate the stress distribution and deformation o f steel in hot rolling and to prevent the generation of internal or surface crack of slab in continuous casting.
In this report, first of all, the following dynamic properties of plasticine is treated to establish the foundation of simulation:
i) Static properties (the stress-strain relation, its dependence on temperature and a criterion of yielding, etc.)
ii) Kinetic properties (the dependence of stress on the strain-rate etc.)
iii) Friction with metal surface.
From the above investigation, it became clear that, there exists the following relation between the stress σ(kgf/cm²), logarithmic strain ε, strain-rate ε(1/s) and temperature T(°K), in the region of T=253°-323°K, ε=0.02-0.3 and ε=10^-2-10⁰l/s; σ=1.15×10^-5ε^0.085ε^0.12 exp(3530/T)
Then the above result is compared with the deformation resistance of steel at high temperatures (about 1000°C). And it is confirmed that plasticine has well satisfied properties to simulate not only the deformation of steel at high temperatures but also the stress distribution.

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The electrical resistance of Fe-C-Si alloy containing flaky graphite was studied in relation to the graphite structure. When unidirectionally solidified at a rate less than 1cm/hr, a lamellar graphite structure was given rise to in the alloy, but the electrical resistance measured in directions either parallel or vertical to the solidification direction was always 50-80μΩ-cm regardless of the direction: there was unexpectedly no anisotropy. This was because the graphite was arranged at random in the plane vertical to the solidification direction.
On the other hand, when the unidirectionally solidified alloy was further rolled or forged, the graphite flakes of the alloy were evenly layered in the vertical plane. The electrical resistance in the direction vertical to the flow direction was then about 10-20 times as much as the one in the parallel direction: there was a large anisotropy of electrical resistance in this layer graphite Fe-C-Si alloy.

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A bell-less top has been installed for the fourth campaign of Chiba No. 2 blast furnace, Kawasaki Steel Corp., in consideration of its high flexibility in controlling burden distribution in the furnace. Before blowing-in, tests were conducted to obtain comprehensive information about the burden distribution by using the full-scale top for No. 2 blast furnace.
ITV-system and mechanical profile meter for observing the motion and piling behavior of burden materials have been developed and installed to full utilize the flexibility of the bell-less top. Various charging patterns were tried in the actual operation. As a results, the control method of the burden distribution has been established to meet any operational requirement, either for full-capacity or reduced for the production of steel making pig iron as well as for the production of foundary pig iron. Furthermore, the charging method for small size sinter has been newly developed to reduce the overall cost of pig iron.

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An automatic surface defect detection system for hot ingot-casting-slabs has been developed to support hot-direct-rolling operations. Among several possibilities considered, the thermal image of a hot slab provided by an infrared scanning camera was evaluated as being the best. Having shown that the majority of surface defects could be recognized visually on the thermal image, an image processing system to replace visual recognition was developed. The image processing system as designed consists o f a signal processing unit and a mini-computer. Several different data processing stages are involved in the extraction of defect signals. Many parameters in the processing system were given a range of freedom and the final values adjusted to provide optimum detectability for actual defects. It was concluded that this detection system would enable on-line defect detection if some minor improvements were made. Two topics now under consideration are the coupling o f the detection system to an automated spot scarfer and the application of the system to defect detection in continuous-castingslabs.

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