A new blast furnace process has been developed which blows normal temperature oxygen in place of the hot blast through the tuyeres and injects preheating gas into the upper shaft.
For the development of this process, mathematical model simulations and operation tests with an experimental blast furnace were done. The test operation was so stable that this process was technically verified to be consistent as an ironmaking process. The pulverized coal was injected up to the ratio of 0.94 kg-coal/Nm³-oxygen. The high productivity of 5.1t/dm³ was realized. According to the analysis of measurements during the operation and dissection results, this process has been verified to have the following characteristics; (1) The preheating gas injection lowers the heat flow ratio and raises the temperature in a whole section of the furnace. (2) The gaseous reduction takes place fast at relatively low temperature region and the content of the boudouard reaction is low. (3) The silicon content in metal is lower than that in the hot blast.
The lower limit of the fuel rate was estimated 530 kg/t for a commercial blast furnace.

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The mechanism of silicon transfer in the blast furnace was examined through fundamental experiments, chemical analyses of metal and slag drips taken from the end of raceway during operation and measurements of PO₂ at the same place.
The (FeO) content in slag averages about 15wt% and oxygen partial pressure PO₂ averages 10^-12 atm at the end of raceway.
These data imply that siliconization reaction via SiO gas from coke ash and slag occurs chiefly in the zone above and below tuyere level, respectively.
Slag-metal reaction occurs chiefly in the zone below tuyere level and desiliconization reaction proceeds until (FeO) content in slag is reduced to about 0.2wt %.
In the hearth, the slag-metal reaction, i.e. Si+2(FeO)=SiO₂+2Fe, changes from desiliconization to siliconization reaction and [Si] content in metal approaches [Si]_eq, at (FeO)=0.2wt %.
If the [Si] content of dripping metal is more than [Si]_eq at (FeO)=0.2wt% or (FeO) content in slag is more than 0.2wt%, siliconization reaction does not occur any more.
The measured [Si] content agrees with the above equilibrium one in many blast furnaces. In some blast furnaces, however, the measured values are lower than the equilibrium ones. It is indicated that hot metal is tapped before the above equilibrium one is reached in these cases.

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A new atomization process is proposed in which molten metal is atomized by electromagnetic energy instead of kinetic one produced by fluid impingement or disk rotation in the conventional atomization processes. This electromagnetic atomization process was tested to clarify characteristics of atomizing molten metal. It was found that a crucial operation factor is a contacting condition of molten metal with an electrode. In order to control the condition, a delay time controller unit was developed and incorporated in the electromagnetic atomization process. It is noticed that this controller works well to produce the better uniform size particles than those of conventional atomization processes.
A linear relation between the impulse which is defined as the product of the imposed electromagnetic force and the period of current passing, and the momentum which is defined as the product of the mass and the velocity of splashed particle, is found by use of experimental data and this fact is explained from a theoretical view point.

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Experiments were carried out in 5 t converter using five kinds of gases as a bottom blown gas in order to quantitatively evaluate the contributions of stirring force and dilution of P_CO by bottom blown gas to characteristics of metallurgical reactions in a converter. On the basis of the experimental results, a new reaction model was proposed, which enables us to reasonablly explain the metallurgical reactions in a converter with bottom blown gases.
The results obtained are summarized as follows;
1) Independently of sort of bottom blown gas, oxygen concentration dissolved in steel decreases as increasing the gas flow rate of bottom blown gas.
2) Taking into consideration oxygen transfer from metal to slag, the model can reasonablly explain the phenomena that concentrations of carbon and oxygen reduce to those in equilibrium with less than 1.0 atm of CO.
3) The amount of oxygen transfer from metal to slag increases with increasing the stirring force by bottom blown gas and decreasing carbon concentration in molten steel.
4) The effect of dilution of P_CO on behavior of oxygen concentration in steel and (%T. Fe) in slag is considered to be small. Hence, the decreases of. oxygen and (%T. Fe) in IOD(Inert and Oxygen Gases Decarburization) mode result from the increase of stirring intensity by inert gas blown from bottom.

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18-8 stainless steel ingots which are added with surface active elements, Bi, Sn, Te are cast with the water cooled copper mold at the pouring speed of 10 mm/s. Transverse and longitudinal microstructures in the vicinity of the surface of ingots are observed. The solidification microstructures become fine and the effect of rapid quenching increases with increasing the amount of the surface active element. Primary dendrite arm spacing is about 50μm at the 50μm from the surface of ingot which is not added with the surface, active element, but arm spacing is about 10μm in the case of 0.0055 mass %Bi addition. Corresponding cooling rate are 1×10² and 3×10³K/s, respectively.From temperature distribution in the water cooled copper mold, heat flux are calculated. The maximum value of heat flux in the mold increases and appears soon, when the surface active element is added.It is seemed that by the addition of the surface active element wettability increases, therefore heat transfer coefficient between molten steel and mold increases. Furthermore, the surface active element seems to have the effect of increase of nucleation rate.

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Camber or in-plane warping of plates after longitudinal cutting occasionally becomes a problem, because it is very difficult to correct the deflection. In particular, the slit camber is large for steel plates by controlled rolling or cooling. As the slit camber is related to the residual stress, we carried out thermal stress analysis on the cooling process of steel plates. Then we considered a one-dimensional longitudinal stress state, thermoelastic-plastic material and stress relaxation. We examined the effect of controlled rolling (CR) and controlled cooling (On-Line Accelerated Cooling, abbreviated to OLAC) on the camber.
The outline of result obtained is as follows.
(1) Stress just after non-uniform deformation in ordinarily controlled rolling with the finishing temperature of 680-780°C causes the residual stress of maximum 100 MPa at room temperature. Therefore, the influence of rolling condition on the slit camber cannot be ignored.
(2) The type of controlled rolling which generates tensile residual stress in the edge of width, reduces the slit camber caused by non-uniform cooling during OLAC.
(3) Optimum value of masked edge for reducing the slit camber is 50-100 mm for 30 mm thickness.
(4) Lower initial temperature or higher end temperature in controlled cooling reduces residual stress and its slope, which results in smaller slit camber.

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In order to improve the characteristics of an insulating coating, addition of PAN and AE as resin components was investigated.
The results were as follows.
In the insulating coating with PAN and AE film defects such as fine crater were not found. On the contrary the coating without PAN easily formed film defects.
It is supposed that PAN remains as particles even at drying temperature because of its high melting point and as a result, water which causes film defects vaporizes and escapes easily from the interior of the coating.
A proper composition of PAN was found to be 25-75wt% of resin in the coating. Addition of PAN in this composition range, improves the corrosion resistance, TIG weldability, the interlaminar resistance, etc. of the coating.
Poor punchability was perceived by single application of PAN, however excellent punchability was obtained by PAN/AE mixture.

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Critical conditions to repassivate growing crevice corrosion in terms of electrode potential, E_R, temperature, T_R, and NaCl concentration, C_Nacl, _R, were determined for metal/metal-crevice of ASTM Grade 12 (G 12 Ti) and Ti-x (=0?2%)Ni-y(=0?0.4%) Mo alloys.
G 12 Ti with 0.8%Ni and 0.3% Mo has more noble E_R values than commercially pure Titanium (C.P. Ti)and this tendency is more enhanced in lower concentrations of NaCl solutions. G 12 Ti is predicted to be resistant to crevice corrosion in solutions containing as high as 9% NaCl at 100°C, which is markedly high-er than 1% NaCl or less as the highest concentration for C. P. Ti to be resistant at the temperature.
E_R value for Ti-x Ni-y Mo alloy depends almost on Ni content. Sufficiently noble value of E_R is attained for the alloys with Ni contents over 0.2%. The beneficial effect of Ni could be explained from formation of Ti₂Ni which works as Pd does in Ti-0.15 Pd alloy.
C_NaCl, _R depends not only on Ni content but also on Mo content. It decreases with increasing Mo content in the range from 0 to 0.1?0.2%, above which C_NaCl, _R increases with increasing Mo content. This shows beneficial effect of Mo combined with Ni. Based on the results of Ti-x Ni-y Mo alloy, characteristics of G 12 Ti are found to be accounted for approximately through its contents of Ni and Mo.

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Stress corrosion cracking behavior of martensitic stainless steels is evaluated as a function of tempering temperature by means of three points bending SCC tests in high purity water at 70-288°C. Stress corrosion cracking initiates at small corrosion pits or crevice corrosion and SCC susceptibility increases with increasing hardness of the steel. Threshold SCC stress is about 300 MPa for the steel with hardness of HV 430 and equal to yield strength for that of HV 300. No susceptibility is detected for the steels of which HV are less than 270 with an exception of the steel of high Ni content. SCC susceptibility increases with increasing water temperature and increasing hardness of steels. Chromium plated steel and high Ni steel show higher SCC susceptibility than the unplated steel and lower Ni steel, respectively. Low C and low Ni steel in fully annealed conditions exhibits no SCC susceptibility even in long term exposure test for 5 000h in high purity water at 288°C.

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クリープ疲労特性の優れた改良型SUS 316の開発を最終目的に,クリープ破断特性に対する炭素,窒素,Moの影響を調査した.炭素による強化は破断延性を大きく損なうが,窒素は破断延性を劣化させることなく強化できる元素である。したがって,破断延性が重視される高速炉の構造用鋼としては,炭素より窒素で強化することが望ましい.またMoは強化にともなう延性低下が小さく,有効な元素と言える.
クリープ疲労特性はクリープ破断延性と相関することから,クリープ疲労特性のすぐれた鋼種として低C-中N系(0.01%C-0.07%N)316MNを開発した.本鋼は従来のSUS 316に比べ長時間側でのクリープ破断強度の低下が小さく10000hで約1.2倍の破断強度とすぐれた破断延性を有し,さらにクリープ疲労試験においてもすぐれた特性を示す.

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The growth behaviour of γ' (L1₂) -phase precipitates in Inconel X-750 type Ni-base alloy has been investigated mainly by micro-Vickers hardness test and transmission electron microscopy. The precipitating phase was observed to be spherical especially at the early stage of aging time and to be ordered fcc γ' phase, likely pointed out previously.
The hardness of specimens aged in various conditions closely related to the size of γ' precipitates.
The growth kinetics of γ' precipitates followed the predictions of Lifshitz-Slyozov-Wagner (LSW) theory of diffusion controlled growth at all aging temperatures. The activation energy for the growth of γ' precipitates was estimated to be 281 kJ/mol which was nearly similar to those of diffusion of solute atoms in Ni and Ni-base alloys. This would also suggest that the growth of γ' in Inconel X-750 type alloy follows the Ostwald ripening of diffusion-controlled growth. The actual particle size distribution of γ' was somewhat different from the distribution predicted by the LSW theory.

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The effect of residual stress on fatigue strength of a medium carbon steel was investigated. Specimens were induction hardened and subsequently reheated in three conditions to give them various distributions of residual stress. Fatige limit was improved by reheating in a condition compared with as induction hardened. Residual stress after the heat-treatments was compressive around the surface of the specimens, and varied to tensile stress in the inner unhardened region. A method to estimate fatigue limit from the total stress which is the sum of the residual stress and applied stress was proposed.

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Breaking accidents which started at the center bore face of the journal of large sized backup rolls were experienced. To settle these problems, the working stresses inflicted on the center bore face of the backup roll was analysed by the three-dimensional photoelastic method. The fatigue strength of the test pieces taken from the core part of the journal and the residual stresses were also investigated. The main results obtained are as follows:
1) Though the repeated tensile stresses were inflicted on the center bore face of the journal, they were not so large. It is thought that the main cause of the fracture in question was the residual tensile stresses there.
2) The fatigue strength in the core part of the journal was equivalent or less than the fatigue strength of the sharp notched test pieces.
3) It was concluded that the breaking accidents from the center bore face could be prevented by giving the residual compressive stresses on the bore face.

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The article has proved the possibility of replacement of lead patenting in wire production from two respects of theory and practice, and pointed out that lead patenting in wire production should be not considered isothermal quenching operation, while ought to be visualized as continuous cooling heat treatment. The development of hot water quenching for wires and the relevent deta were evaluated, and so the reason was discussed that the hot water quenching of wires could not be expaned. A new procedure of hot water quenching was invented by theoretical analyse and a great of experiments, in which wires heated to 1 1931 223 K are first immersed in hot water for a certain time ( > 2/3 total boiling time), and then taken from the hot water, transferred to a brittleproof furnace at 773873 K and cooled in air after austenite has decomposed. The results obtained in laboratory and wire production have confirmed enough that the new operation can ensure the quality of hot water quenched wires to keep up with or to exceed the average levels attainable with lead patented wires.

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本論文によって明らかにされた点を要約すると下記のようである.
(1) これまで鋼線のパテンチング処理に高温オーステナイト化(1193～1223K)が採用されていたのは溶融鉛の冷却能が低いためである.冷却速度を高めることにより,オーステナイト化温度を熱処理の一般的加熱温度(A_C3+20～30 K)に低下できる.
(2) 鋼線の熱水焼入れは,鉛パテンチングより冷却速度を増すことができ,その結果,低温オーステナイト化を採用できる.
(3) 純沸騰水中で単段熱水焼入れを行う時,オーステナイト化温度が上がるにつれて強度,延性は増すがオーステナイト化温度がTmを超すと,鋼線は部分的にマルテンサイトが生成して脆性破断を生ずる.しかしながら,双段熱水焼入れの場合には,熱水焼入れ鋼線の機械的性質が鉛パテンチング材の上限レベルに達する.
(4) 鋼線の線径にかかわらず,冷却速度を増すことにより,オーステナイト化温度を1073～1123Kの温度範囲とすることができる.
(5) 低温加熱複合水浴処理は鋼線の生産における最もよい熱処理方法で,中間熱処理(焼ならし)の加熱温度を1073～1093Kに降下し,最終熱処理(パテンチング処理)の加熱温度を1093～1113Kに下げることができ,得られた機械的性質は鉛パテンチング材のレベルに達する.この新しい熱処理方法により,太径の鋼線(>5mmφ)の機械的性質は鉛パテンチング材に比べて高くなる.

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