Experiments were carried out at 1650°C to investigate the smelting reduction mechanism of chromium ore sinter by graphite. Chromium ore sinter was made from chromium ore and Tuxes such as lime stone, silica sand and serpentine.
The following results were obtained:
(1) Chromium ore particles are dispersed in molten slag until they are entirely dissolved at the terminal stage of the reduction.
(2) The reduction rate is controlled by the step (ii) of the following steps:
(i) the dissolution of chromium ore particles into molten slag
(ii) the reduction of chromium and iron oxide in the slag at the slag- graphite interface
(3) The contents of Al₂O₃ and MgO in molten slag increase as the reduction proceeds with the dissolution of chromium ore particles.
(4) The reduction rate seems to be decreased by the increase of Al₂O₃ and MgO.

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A new ironmaking process named SC process has been developed. This process is characterized by the separation of such functions as reducing and smelting which are undertaken in two furnaces, a reduction furnace of a shaft type and a melting furnace of a coke bed type, and by the use of pulverized coal in a large quantity.
Through the operation tests by a pilot plant of 8 t per day in production capacity, SC process has been confirmed to be useful one as an ironmaking process.
On the basis of the results obtained by the pilot plant operation, a commercial plant of 2 400t per day in productivity having the following features has been designed.
1) High productivity, being 2.5 times as large as that of blast furnace.
2) High heat efficiency, competing with blast furnace.
3) A wide use of non coking coal, being 70% of total coal.

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A study was made on the rate of nitrogen desorption from molten iron by Ar injection. Argon was injected into the melt through a submerged alumina nozzle of 0.1cm in ID. and 0.3cm in O.D. The immersion depth of the nozzle was 4.6-5.2cm. The gas flow rate was in the range of 74-96Ncm3/min. The oxygen content in the melt was varied as 0.004-0.066%. During the experiment, the bubble formation time was measured by a pressure pulse technique.
The measured desorption rates are compared with those calculated by a mixed control model derived by considering that the mass transfers in both liquid and gas phases and the chemical reaction at the bubble-metal interface are the rate controlling steps. Nitrogen desorption during the bubble formation is taken into account in the model. From comparison between calculation and experiment, the chemical reaction rate constant is determined. It is shown that the chemical reaction rate constant decreases with increasing [%O]+[%S]/2. The rate constant obtained in the present study agrees with that obtained in the previous study on nitrogen absorption in molten iron. It is confirmed that both nitrogen absorption and desorption in molten iron could be explained by the mixed control model.

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A study was made on the rate of nitrogen desorption from molten iron by Ar injection together with blowing onto the melt. The immersion depth of the nozzle was 4.6-5.2cm. The flow rates of gas injected into and blown onto the melt were 53-94Ncm3/min and 1 100Ncm3/min, respectively. The oxygen content in the melt was varied as 0.007-0.040%.
It is found that Ar gas blowing onto the melt surface largely enhances the rate of nitrogen desorption by Ar injection. The observed rates are compared with those calculated from a mixed control model. By the comparison between calculation and experiment, the effective free surface area of the melt is obtained. Under the present experimental conditions the effective area is almost independent of the gas flow rate through the nozzle and of the oxygen content, and is about 2.1 times as large as the cross sectional area of the crucible. Since the ratio of the gas-metal interfacial area to the volume of the melt was very large in the present experiment, the nitrogen concentration in the melt decreases rapidly to less than 0.001%. Nitrogen desorption from molten iron can be explained by the mixed control model over a very wide range of nitrogen concentration.

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When a biaxially oriented polyethylene terephthalate (PET-BO) film is laminated on tin free steel (TFS) at 260°C (melting point of PET) or slightly higher temperatures, the interfacial layer fuses and transforms into an amorphous, non-oriented film. The amorphous PET layer contributes to adhesion to TFS, while the remaining PET-BO layer affects formability and corrosion resistance; a higher fraction of PET-BO leads to better resistance to water permeation and mechanical properties of the overall PET film. On the other hand, adhesion to TFS improves with decreasing fraction of PET-BO in particular for the deep drawn articles of TFS laminated with PET film. Therefore, adhesion and corrosion resistance must be optimized. Optimization is found to be achieved if the fraction of PET-BO in PET film is controlled within 30 to 70%, . Furthermore rapid quenching after lamination of PET-BO film to TFS prevents recrystallization of the amorphous PET and ensures good adhesion to TFS.

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Two high carbon steels, 1.27% C and 1.24%C-12%OMn, have been rolled isothermally at 930K. The tensile and the fatigue strengths were investigated. The tensile strength and the ductility for 1.27% C steel were improved by the warm rolling. On the other hand, for 1.24%C-12%Mn steel the tensile strength was raised at the expense of ductility. The fatigue strength of warm rolled steel was superior to that of forged steel. The fatigue ratio was improved by warm rolling, although the notch sensitivity was almost similar for both steels.

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Computer image processing technology has been applied to fracture surface analysis, and the generalized software for 3-dimensional fractography image analysis has been developed. By this software, it became possible to obtain 3-dimensional fracture surface topography from a stereo pair of SEM fractographs with sufficient precision. As for the identical position search algorithm to calculate the fracture surface height, the SSDA method was fitted to fatigue fracture surfaces in air and in vacuum. Whilst the correlation method must be applied to the corrosion fatigue fracture surface being adhered corrosion products or calcareous deposits on it, as well as to the inter- and transgranular mixed one. The crack closing simulation by means of the 3-dimensional fracture surface topography accounted for the wedge effects induced by the corrosion products or deposits as a first approximation. The results were well correspondent to the shape of load-strain hysteresis loops. On the contrary, fracture surface roughness deduced from the 3-dimensional topography was not necessarily corresponded to the crack closing behavior.

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The influence of B content on the hot cracking sensitivity of the heat affected zone (HAZ) in Incoloy 800 was examined by Varestraint test and by hot ductility test using the thermal cycle simulator. The results indicated that the HAZ cracking sensitivity increased with the increase of B content until the B content exceeded about 0.01%, which is estimated to be the solubility limit, but the cracking sensitivity was decreased above 0.01% B. Similar relationship has been observed in the case of weld metal. However, the mechanism of the HAZ cracking seems to be somewhat different from that of weld metal cracking which depends on the extent of healing phenomenon, as the change of liquid film composition during the weld thermal cycle was observed. On the heating of weld thermal cycle, the composition of the liquid film in the HAZ was assumed to have been mainly that of Cr₂B eutectic. However, the diffusion of B atom from grain into the grain boundary, in the weld thermal cycle after the initiation of grain boundary liquation, was so little at low B content below the solubility limit that (Fe, Ni)₂B eutectic with a lower melting point than Cr₂B eutectic became to dominate the composition of the liquid film, resulting in the extension of the brittle temperature range and the higher cracking sensitivity. On the contrary, at the B content higher than the solubility limit, the diffusion of B atom into the grain boundary was so sufficient that the liquid film preserved the composition of Cr₂B eutectic which reduced such the brittle temperature range as described at low B content.
The relation between hot cracking sensitivity of HAZ and B content of Incoloy 800 as mentioned above seems to be derived from the change of brittle temperature range due to such a difference of the liquid film composition.

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The effects of hydrogen introduced into a welded joint particularly from moisture of filler material used during welding of heavy gage steels are followed. The results are compared with the effects of hydrogen introduced by controlled electrolytic hydrogenization as a simulation of the hydrogen diffusion from cooling water into welded joints during the reactor operation. The quality of welded joints is shown to be unfavourably influenced by combined effects of hydrogen embrittlement and phosphorus segregation along grain boundaries. The optimum annealing for regeneration can be effectively performed at temperatures about 500°C, when the intergranular concentration of phosphorus and sulphur is minimum and the hydrogen content decreases depending on the temperature and activity of surrounding environment.

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