In order to evaluate the effective diffusivity (De) for CO and CO₂ through coke at elevated temperatures, two sorts of experiments based on the following two methods were undertaken: (1) Determination of De from direct measurement of the diffusion flux by the Wicke-Kallenbach method at ambient temperature (2) Derivations of De by the use of a mathematical model from the overall oxidation reaction rate of coke with CO₂.
The values obtained by those two methods were compared with each other and it was found that they were in a fairly good accordance. It suggests that the overall reaction rate can be predicted by the use of De obtained by the independent measurement (1).

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Pulverized Chromite ore has been injected into 20kg of carbon containing iron melt from the bottom of crucible, so that the ore is reduced by the dissolved carbon. The effects of temperature, ore injection rate, flow rate of gas and particle size of the ore on the chromium yield and reduction rate have been examined.
The chromium yield increases linearly with temperature, decreases with an increase in ore injection rate and decreases linearly with increasing mean particle diameter. The gas flow rate has no effect on the yield. The highest yield of about 100% is obtained with the ore injection rate of less than 20g/min at 1680°C. From the behavior of silicon during the process, it is concluded that the oxygen transport in the melt is the rate determining step. The reduction process can be divided into transitory and permanent reactions. The fraction of transitory reaction is in the range of 60 to 75% at 1500 and 1600°C, and becomes more than 80% at 1680°C. The rate of transitory reaction increases proportionally to the 2/3 power of ore injection rate, and decreases proportionally to the inverse square root of the mean particle diameter. The gas flow rate has not so much effect on the rate. The apparent activation energy is 46.0kcal/mol.

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At Kakogawa Works, steels of low to high carbon contents are produced by the use of LD converter of top and bottom blowing type. Argon and nitrogen has been used for the bottom stirring gas. In response to the recent increase in argon consumption, carbon monoxide (CO) recovered from LD exhaust gas is now being used to replace argon for bottom stirring.
By the COSORB^® process using a large scale CO gas generating equipment introduced from Kinetics Technology International Corporation, highly purified CO can inexpensively be produced from LD exhaust gas. The COSORB^® process is a gas-liquid absorption method using the COSORB^® solution, which is a toluen solution of Cu-AlCl₄. By the COSORB^® method, the gas having the chemical composition suited for bottom blown gas in the BOF can be produced in large enough quantity.
The use CO as the bottom blown gas, particular attention should be paid to the CO concentration in the bulb station room where the possibility of CO leakage is present and to clean the pipe line during the non-blowing period.
The characteristics of metallurgical reactions in the converter, for examples [O]F and slag (T.Fe) at turn down, are almost the same as those of argon and nitrogen bottom stirring. However, the carbon content in the molten steel is increased by CO rinsing after the oxygen top blowing; in contrast the carbon content is reduced in the case of argon rinsing.
This is attributable to the fact that the decarburization reaction does not occur during CO rinsing due to the presence of CO bubble; otherwise the CO decomposition reaction (CO (gas) in CO bubble→C+O) occurs.
At Kakogawa Works, the erosion rate of refractory has been reduced by the development and installation of S.A. tuyere (Single Annular tuyere). By the use of CO as the bottom blown gas, mushroom is formed in a similar manner as in the case of argon blowing. The life of the tuyere can be prolonged 20% as compared with the case of argon blowing due to the cooling effect of CO.
By the installation of safety devices, it is possible to substitute CO for argon in order to reduce the gas cost.

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An experimental technique has been developed to investigate the effect of condensation of moisture on the permeability of beds of granulated sinter feeds. The technique involves injecting atomized water into the air stream of a laboratory permeameter at ambient temperature and measuring the resulting change in pressure drop across the bottom portion of the bed where the moisture accumulates. The technique provides a relatively simple means of assessing the behaviour of sinter mixes towards condensation during sintering without the need to perform a conventional sinter test.
The technique was applied to a granulated Australian iron ore sinter feed to investigate the change in permeability due to condensation prior to collapse of the bed, the region of most practical interest. The results were analysed using the Ergun equation for flow through packed beds on the assumption that the condensed water enters the granules, resulting in their swelling with a consequent decrease in voidage. These effects and changes in the granule shape factor, due to a combination of a rounding effect of the added water and sagging due to weakening of bonds within granules, can account for the observed decrease in the permeability of the bed. However, in the absence of experimental confirmation, the alternative hypothesis that the decreased permeability is due to a reduction in the bed void space due to accumulation of condensed water in interstices between granules must still be considered a possible explanation.

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Manganese in molten high manganese steel volatilized and penetrated mostly through the serpentine and the cracks in the olivine sand grains. The penetrated manganese lowered the melting point on the surface of the olivine sand grains, and a smooth shell (partly-fused layer) was formed at the metal-mold interface. After cooling, the shell easily peeled off from the casting without burning as a result of low affinity between the metal and shell. A similar reaction was observed both in green and calcined olivine sand, however, the shell was thinner on the green sand than the calcined olivine sand mold. The calcined sand caused neither blow holes nor pin holes, but the green sand may cause blow holes and pin holes from the dehydrated gas when the permeability is not sufficient in the mold.
A comparison was made between the olivine sand and silica sand, and the effect of manganese coating on the olivine sand grains against burning was investigated in the present work. No burning took place between the olivine sand mold and low carbon steel, but a small quantity of manganese in steel diffused into olivine sand grains at the metal-mold interface. The low carbon steel penetrated into silica sand mold to combine with silica sand forming fayalite with a small quantity of manganese at the metal-mold interface. Manganese in molten high manganese steel diffused into the mold to combine with silica sand grains as 2MnOSiO₂. High-manganese cast steel did not penetrate into silica sand mold because of the low pressure of molten metals. Manganese-coating on the olivine sand grains prevented the burning of low carbon steel.

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The use of olivine sand as a molding material is limited in comparison with silica sand, and its characteristics are not sufficiently known. The previous papers by the authors described that the olivine sand mold prevented burning not only in the case of high manganese cast steel but also of low carbon cast steel. Metal-mold reactions between a high chromium steel and an austenitic stainless cast steel, and olivine and silica sand mold were investigated in the present work. Olivine sand mold exhibited a similar or better resistance to burning than silica sand mold with high chromium steel or austenitic stainless steel. Chromium and manganese in molten steels reacted with the surface of olivine sand and formed a smooth shell on the mold surface. The smooth shell had a high packed density of solid sand particles and prevented metal penetration. After cooling, therefore, castings were removed easily and showed no burning. But in the silica sand mold a similar smooth shell was formed only in a 25% chromium steel and an austenitic stainless steel. The surface of quartz (silica sand) and olivine (dunite not serpentinized) reacted slightly with chromium and manganese in the molten high chromium steel. Neither chromium nor manganese was detected inside the quartz or the olivine which was confined in the smooth shell layer.

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The mechanism of toughness degradation by temper embrittlement is studied in 13Cr-4Ni martensitic stainless cast steel. The variation of toughness, brittle fracture mode and fraction of retained austenite are examined as a function of tempering temperature and the subsequent isothermal treatment in the range 550-450°C. Temper embrittlement is referred to as increases in FATT and fraction of intergranular fracture after tempering at lower temperatures and subsequent isothermal treatment at higher temperatures. The embrittlement is found to be related to the intergranular fracture and precipitation of carbide along prior austenite grain boundary. The degree of the embrittlement is found to be substantially independent of the segregation of phosphorous at prior austenite grain boundary. The precipitation of intergranular carbides is resulted from the decrease of carbon solubility in the reverted austenite during tempering. Susceptibility to temper embrittlement in this steel is suppressed as tempering temperatures are raised.

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The use of pressed notch drop weight tear test (PN-DWTT) for a highly ductile linepipe steel encounters an abnormal fracture appearance, and raises difficulty in evaluating its crack arrestability of the steel. The lateral compression DWTT (LC-DWTT) has been developed to solve this problem and comparative studies with other DWTTs were carried out.
The abnormal fracture appearance can be reduced in LC-DWTT. The 85% shear area transition temperature in LC-DWTT was a little higher than that in PN-DWTT but lower than that in precrack DWTT (PC-DWTT). The dynamic load-displacement characteristics of LC-DWTT revealed that the crack initiation energy was reduced and the total absorbed energy was almost equal to the propagation energy of PN-DWTT. On the other hand, PC-DWTT showed the lower absorbed energy because of the plastic deformation in a specimen ligament in introducing a precrack, as compared with other DWTTs.

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Effect of thermo-mechanical history during cooling from solution treatment temperature of 1300°C on the ductility at 800°C at a strain rate of -10-3s-1 of low carbon low alloy steels has been investigated by means of hot tensile test in relation to surface cracking of continuously cast (CC) slabs. The ductility of the specimens directly cooled to the deformation temperature is largely reduced by the slow strain rate deformation especially in Nb steels, since ductile intergranular fracture of austenite easily occurs because of the dynamic precipitation of carbonitrides such as NbC and/or AlN within the matrix as well as on the grain boundaries. By decreasing the cooling rate or by isothermal holding at around 1100°C, the ductility is significantly improved and the fracture mode changes into transgranular ductile, because the dynamic precipitation is much reduced by nucleation and coarsening of the precipitates in these processes. This, however, takes extremely long time to achieve the coarsening of the precipitates in conventional CC process, and is not practical. In order to accelerate this phenomenon, the effect of the prior deformation was examined, and the optimum conditions suitable for CC process were determined. In the case of continuous cooling, the predeformation larger than 5% should be applied at temperatures around 1050°C at strain rates larger than -10-2s-1. The ductility of the specimens predeformed at lower temperatures can also be improved by employing the subsequent reheating process. These results can be explained in terms of carbonitride precipitation behavior. It is quite difficult to recrystallize coarse austenite such as that in as-cast steels, though the ductility improvement can be obtained by grain refinement due to recrystallization.

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A carbon-carbon (C/C) composite was fabricated in laboratory by means of a simple hot press process using fine pulverized coke and carbonaceous bulk mesophase (BM) as matrix and resin-impregnated, unidirectional long carbon fibers (UD fibers) and cloths as reinforcement. Maximum temperature and pressure in hot press process were carried out at 600°C and 49MPa, respectively. When two types of UD fibers (of UD-1 and UD-2) are used, the maximum strength of primary products is obtained at the BM ratio in matrix 70% and with the V_f value 30% in case with UD-1 and at the BM ratio 80% and with the V_f value 46.4% in case with UD-2, the latter being a little higher. When two types of cloths (of CL-1 and CL-2) are used, the strength is maximum at the V_f value 20% in both cases, which is however much lower than the maximum strength when UD fibers are used. Primary products reinforced by UD-2 and CL-2 lose their strengths through heat treatment. As far as primary products using UD fibers are concerned, the maximum strength marks 119 and 130MPa for UD-1 and UD-2, respectively, which are higher than the strength of the commercial C/C composite.

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A new type thin-film goniometer method is capable of obtaining increased reflection intensities to measure quantitatively the reflection lines from Si thin films, Fe films on glass plates, and surface oxide-films on stainless steels, which can not be detected by the conventional θ-2θ method. Formation of FeCr₂O₄ film on 304 stainless steels is found to be dependent on the dew point temperatures of annealing atmosphere.

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The high blow rate tuyere practice together with top blowing has improved AOD process in terms of the shorter operation time, productivity and cost saving. For effective operation, the process computer system based on the optimum operational guidance has been established.

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