A mathematical model is presented for describing the multi-stage reaction of a porous hematite pellet with a reducing gas on the basis of the ISHIDA and WEN'S intermediate model. This model represents non-topochemical behavior; cross section of a pellet is devided into four layers-iron layer and the three reaction zones of hematite-magnetite, magnetite-wüstite, and wüstite-iron layers, in which chemical reaction and gaseous diffusion proceed simultaneously. Semi-analytical solutions to reducing gas and oxygen concentrations in a pellet are derived and fractional reduction and boundary radii are calculated numerically. Acid and basic hematite pellets (porosity_??_0.23) were reduced with hydrogen of 5 Nl/min over a temperature range 700° to 1000°C. Calculated reduction curves and boundary radii agreed well with experimental data except in the final stage of reduction of the basic pellet at 1000°C.

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Because of the replacement of open hearth furnace with convertor, an increase in pig iron output was aimed at No. 2 Blast furnace of Nakayama Steel Works.
For the purpose of attaining high productivity, following ways were adopted under the condition of having no facility for high top pressure operation;
(1) increasing the oxygen enrichment in the blast. (2) maintaining the are agglomeration ratio of 85 per cent, and increasing the strength of sinter. (3) decreasing the fuel ratio by low Si content operation and optimum burden distribution aiming at the improvement of CO gas utilization, (4) in addition, the estimation diagram of stable operation range, which is restricted by theoretical flame temp, heat flow ratio, and shaft gas speed was used in actual operation. As a result of the above measures an excellent productivity of 2.84 t/d/m³ as monthly average was attained in July 1980.

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Improvement was obtained for the reaction efficiency of hot metal desulfurization by lime powder injection with N₂ gas by prior addition of aluminum. That is, the desulfurization rate was markedly faster for Fe-C_sat-Si-Al-S melt than for Fe-C_sat-Si-S melt. Reaction layers on a lime lump immersed in the melts were examined by use of electron probe microanalysis and X-ray diffraction. The improvement of reaction efficiency of lime by aluminum addition was interpreted by the following results of the investigation.
In Fe-C_sat-Si-S melt, solid 2CaO·SiO₂ and 3CaO·SiO₂ layer were formed on the lime surface, which retarded sulfur transfer to its interior. On the contrary, for Fe-C_sat-Si-Al-S melt, molten CaO-Al₂O₃-FeO layer was formed on the lime surface, which enhanced sulfur transfer, and moreover the layer disolved sulfur up to appoximately 50%.
Aluminum concentration to get the improvement of reaction efficiency of lime for plant scale operation in 250^t torpedo ladle was determined to be 0.005+ΔAl%, where ΔAl is the amount of aluminum loss during the desulfurization.

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Molten 18%Cr-4%C-Fe alloy whose composition is close to the ternary eutectic one (m.p.=1150°C) was subjected to the treatment by alkali metal carbonate-halide fluxes at a temperature of 1300°C. Thermodynamically phosphates of potassium and sodium are very stable and their halides are expected to increase activity coefficient of chromium in the fluxes. From those considerations, various mixtures of carbonates and halides of sodium, potassium and calcium were examined for dephosphorization of molten high chromium alloy containing 0.1% phosphorus of 300 g in weight. Higher dephosphorization was obtained with potassium carbonate than with sodium carbonate, and the best dephosphorization degree was 60% without appreciable chromium oxidation when 15 g of potassium carbonatepotassium chloride or-potassium fluoride mixture was used.

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The fluidity of the liquid in the solid-liquid coexisting zone of carbon steel was measured by the seepage of interdendritic liquid into a cylindrical hole formed in that zone. The effective permeability K has been determined in relation to the fraction of solid f_S and cooling rate R, and the speciffc permeability k which depends on the dendrite morphology has been deduced from the effective permeability to give, log K=log 0.10 R^0.81+19.6 R^0.33 log (1-f_S)……(2)
log k=log 1.5×10^-6 R+20.3 R^0.35 log (1-f_S)……(11)
The fraction of solid at which dendrites begin to form networks is 0.290.30 depending on the cooling rate. The effective permeability is 6.3×10^-4 cm/s and the specific permeability is 6.0×10^-9cm². On the other hand, the fraction of solid above which the liquid cannot flow through the dendrites decreases from 0.73 to 0.60 as the cooling rate increases from 0.033 to 0.15°C/s. The values of effective and specific permeability become constant, 1.6×10^-6 cm/s and 2.1×10^-11 cm², respectively, although the fraction of solid is changed by the cooling rate. It has been shown that the effective permeability is mainly controlled by the specific permeability. The fluidity of silicen-free steel which contains 1% molybdenum is smaller than that of carbon steel.

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Heats of mixing of liquid iron with a few metals, having higher melting point than iron (i.e., chromium, molybdenum, tungsten, vanadium, niobium or tantalum), were measured at 1600°C by the developed isoperibol calorimeter. The method for measuring the heat of mixing of a liquid metal and another solid metal was checked by comparing the heat of mixing of liquid nickel and solid iron with that of liquid nickel and liquid iron.
The experimental errors were estimated to be less than ±15% for the cases that a liquid metal was mixed with another solid metal.
Heats of mixing of binary iron alloys, for which the both reference states were liquid, were calculated by combining the present experimental results with the previously reported thermochemical properties. Mixing of liquid iron with liquid chromium, molybdenum, vanadium, niobium or tantalum was an exothermic reaction, while mixing of liquid iron-tungsten was endothermic.

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The effect of aging treatment on lime-falling of steel slag was studied by examining the microstructure and measuring the expansion in CBR mold soaked in water. The stability of crushed stone was decreased with the addition of small amounts of industrial fresh slag. After the slag was remolten in order to assimilate the calcined lime stone completely, the expansion coefficient of the slag didn't exceed 0.2%, even in the case of 5.3% of free lime content. Then, the new method was applied for the evaluation of the free lime in aged slag. The analytical values corrected as water-reactive form were below about 2% in the six-month aged slags. Those slags scarcely included unassimilated lime and indicated high stability in the CBR test. It was found that the free lime of unassimilated form changeed into stable compounds by the aging treatment. Most of the remaining lime was of the crystallized phase from molten slag and didn't bring the lime-falling to the aged slag.

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The effects of the conditions of deep drawing and subsequent aging treatment upon a delayed cracking of meta-stable austenitic stainless steel sheets are studied. The incubation time for the initiation of cracking is measured at various aging temperatures and in the various atmospheres. The results are summarized as follows:
(1) A relation between aging temperature and incubation aging time is represented by a "C-curve" with an asymmetrical form. Consequently, the "nose" where the delayed cracking takes place most quickly is found on each C-curve.
(2) With either lowering of deep drawing temperature or increasing of deep drawing ratio, the C-curve moves toward the region of higher aging temperature and shorter incubation time, showing the expansion of the area where the delayed cracking is induced.
(3) The C-curve is markedly affected by the kind of lubricant used for drawing and the method of removing it after drawing as well as aging atmosphere. This suggests the significance of a certain chemical reaction on the surface of the drawn cup to the delayed cracking phenomena.
(4) The temperature dependence of the incubation time has been studied on assumption that the delayed cracking is initiated when the concentration of diffusing atoms of a certain element at some special microstructure site reaches a critical value. As a result, the apparent activation energy for delayed cracking is estimated to be about 13 kcal/mol, which is approximate to that of the activation energy for the volume diffusion of hydrogen in γ phase of type 304 stainless steel. Then it is suggested that the diffusion of hydrogen also makes a significant contribution toward the delayed cracking phenomena of meta-stable austenitic stainless steel.

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A low carbon rimmed steel heated for a short time in an H₂-N₂ gas was dipped into a molten zinc. The effects of the steel sheet factors, reduction heating conditions and the reducing gas conditions on the wetting characteristics were studied by use of a measuring instrument of gas reduction type meniscograph. A study was also made on the relation between the wettability of steel and the structure of the surface layer of it which was changed depending on these conditions.
The main results obtained are as follows:
1) If the surface layer is made hard by plastic deformation, an increased rate of wetting is caused.
2) The rougher the surface, the higher the equilibrium extent of the wetting force. The surface roughness being the same, the wetting force is lowered when the dew point of the atmospheric gas is raised.
3) The wetting rate sharply increases with the steel temperature just before dipping if it lies between 400°C and 640°C.
4) If the dew point of the gas is increased to the temperature higher than -30°C, the wettability, especially the wetting rate of the steel is deteriorated, which might be caused by Fe-oxide film formation.

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After being heated for a short time in a H₂-N₂ reducing gas, Si-containing steel sheets were dipped into a molten zinc. The effects of Si content in the steel, the preparatory treatment conditions before heating and the reductions in the gas on the dynamic wetting characteristics were studied by use of a measuring instrument of gas reduction type meniscograph. At the same time, a study was made on the relation between the wettability of steel and the structure of the surface layer which was changed depending on these conditions.
The following results were obtained:
1) The wettability of the steel changes depending on the preparatory treatment conditions before the reduction heating.
2) When the Si content in the steel is constant, the equilibrium wetting force is lowered by increasing the heating temperature in the gas or lengthening the heating time therein.
3) A Si-enriched oxide layer which is formed by a reduction heating is mainly composed of (FeO)₂SiO₂ and SiO_X, depending on the Si content in the steel. The wetting characteristic is deteriorated as related to the change of the structure of this Si-enriched oxide layer.

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Fe-25Cr-7Ni-3Mo(A)およびFe-23Cr-6Ni(B)の2種類の二相ステンレス鋼を用いてσ相析出挙動におよぼす種々の因子の影響を調べ,以下の結果を得た.
(1)B鋼はA鋼に比し,σ相の析出に2桁以上長い時間を要した.σ相の析出が非常に速いA鋼との差は,化学組成,特にσ相とγ相に相分離することが知られているσ相の化学組成の差に起因すると思われる.
(2)冷間加工のみならず熱聞加工あるいは焼入歪みもσ相の析出を促進することがわかつた.中でも冷間加工による促進効果は顕著であり,α粒内での析出に加えてγ粒内でもσ相の析出が認められ,従来知られているα→σ+γの反応に加えてγ→σの反応も存在することが認められた.このような内部歪みによる促進効果は,σ相析出の核形成サイトとしての格子欠陥の存在と,これによる相分離の際の各元素の移動のしやすさに起因するものと考えられる.
(3)σ相析出温度域に至るまでの熱履歴により析出速度は大きく異なり,前処理としての加熱温度を高くすることにより析出が遅れることがわかつた.これはαとγとで化学組成が異なるミクロ偏析がα単相としたことによつて軽減され,各元素の濃度が均一化し,σの析出域で再びγの生成過程を必要とするためと考えられる.再溶解では化学組成はほぼ完全に均一化するのでσ相の析出が最も遅れる条件となるのである.このことは鋳塊にはσ相が析出しにくいことを示しており,σ相が析出しやすい二相ステンレス鋼の連鋳化に際し,重要な知見となる.

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Ductility loss of neutron-irradiated Hastelloy-X at elevated temperatures has been examined by post irradiation tensile test. The results were analysed as a function of test temperature, strain rate, thermal neutron fluence and the associated helium content. The contribution of helium production due to the ⁵⁸Ni (n, γ) ⁵⁹Ni (n, α) ⁵⁶Fe reaction in addition to the ¹⁰B (n, α) ⁷Li reaction was considered.
The results obtained are summarized as follows:
(1) The post irradiation ductility decreased with strain rate decrease and test temperature increase up to 1000°C.
(2) As for the helium embrittlement attributed to (n, α)-reaction, the, ¹⁰B (n, α) ⁷Li reaction was dominant at lower fluences, and Ni-two step reaction became predominant with fluence increase.
(3) Extrapolations of the results of irradition at low temperature gave the ductility values of about 3.5% at 900°C and about 1.5% at 1000°C for the thermal neutron fluence of 10²²n/cm².
(4) The threshold thermal neutron fluences for embrittlement were estimated as 6×10¹⁶n/cm² at 900°C and 2×10¹⁶n/cm² at 1000°C, corresponding to the calculated atomic helium fractions of 9.4×10^-10 and 3.2×10^-10, respectively.

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Steady state creep rates and friction stresses were measured at 900°C with a series of carbon free 25Cr-35Ni steels, and the extent of the solid solution strengthening with the addition of the groups IVb, Vb and VIb elements to the steel was discussed in terms of effective stress (-applied stress minus friction stress). In comparison of these results with those obtained in previous data at 1000°C, temperature dependences of solid solution strengthening and friction stress were analyzed.
The steady state creep rate of the steel decreased remarkably with the increase in Mo, W, Nb, Ta, Zr and Hf contents, but slightly decreased with the addition of Cr, V and Ti. A linear relation was found to exist at 900°C between both logarithms of the steady state creep rates and the effective stresses of all the steels independent of the kinds and the amounts of solute elements, and to be parallel with that at 1000°C. These results conclusively demonstrated that the increase in the extent of the solid solution strengthening at 900°C due to the addition of solute elements was mainly attributed to the increase in the friction stress as well as in the case at 1000°C.
The more effective the solid solution strengthening was obtained, the larger the activation energy for creep at the constant applied stress became. However, the activation energies estimated at the constant effective stress were 60±5 kcal/mol in all the steels studied, being independent of the kinds and the amounts of solute elements. Moreover, temperature dependence of the friction stress was observed, and then, it was pointed out that temperature dependence of the solution strengthening was due to that of the friction stress.

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