High silicon duplex (γ plus 30-70% δ) stainless steels were studied on the changes in mechanical and corrosive properties and microstructure with heat treatment. The roles of silicon as an alloying element in the steels were analyzed in terms o f the chromium equivalent and the partition in each phase.
Precipitation of M₂₃C₆ and σ phase proceeds at a temperature in the range of 550 and 1 000°C. Formation of M₂₃C₆ is responsible for grain boundary corrosion after tempering at 450°C and heat treatment at above 1 150°C. Hardening progresses in two stages during tempering at 450°C; the first stage has the characteristics similar to the strain aging in that the process is suppressed by alloying of vanadium and tungsten and the second similar to the 475°C embrittlement.
Resistance to corrosion in non-oxidizing type acid is weakened after tempering at the temperature range of 550-1 000°C by decomposition of δ phase. Silicon enriched in δ phase with a ratio of 1.1 to γ and the value is lower than chromium and molybdenum.
A good combination of mechanical and corrosive properties can be obtained in the high silicon duplex stainless steels by tempering at 450°C for less than 4hr after solution treatment at 1 050°C.

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For the purpose of investigating the formation mechanism of the texture which is developed by ferrite (α)→austenite (γ)→ferrite (α) transformation, the effects of heating and cooling rates during phase transformation and specimen thickness on the transformation texture have been studied by using an extra low carbon sheet steel with the initial texture of {111}.
The results obtained are summarized in the following:
(1) A weak {100} and {111} texture was formed in the surface layer of the specimen transformed by rapid heating and rapid cooling.
(2) By rapid heating and subsequent slow cooling, a texture with {110} orientations and orientations 20-30 deg shifted away from {100} was obtained in the surface layer.
(3) Slow heating and slow cooling produced a distinct {100} texture in the surface layer.
(4) There was a marked difference in texture between surface and midsection of thick specimen: In the midsection, the texture similar to that described in (1) was formed, independent of the heating and cooling rates. While, the specimen surface exhibited the texture as mentioned in (1) to (3) on each condition.
(5) Those results were consistently explained on the assumptions that the orientation relationship between bcc and fcc follows the Kurdjumov-Sachs relation, and that during a slow progress of α→γ→α transformation the orientation change proceeds preferentially by operation of such variants that generate a larger elastic work in the normal direction of a sheet surface.

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Experimental data are presented for the solubility of sulfur in liquid Fe-C alloys coexistent with solid calcium oxide, calcium sulfide and carbon monoxide of known pressures at 1 600°C. The equilibrium constant is determined for the sulfur reaction in terms of the activities of sulfur and carbon in iron for composition ranges 0.005 to 0.4% S and up to 3% C. The extrapolation of the data to hot metal compositions predicts for unit activities of calcium oxide, calcium sulfide and carbon monoxide, the equilibrium sulfur content of 4ppm for 1 600°C and 8ppm for 1 400°C. In relation to ladle desulfurization of hot metal, selected data are presented on some slag-metal reaction equilibria.

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A simulation model for the burden distribution at a blast furnace top was developed. In addition to the static deposit angle, the following factors which have strong effect on the burden distribution were considered in the model.
1) Mixed layer formation in the furnace center during ore dumping
2) Decrease of burden deposit angle by gas flow
3) Change of burden deposit angle by the velocity distribution of burden descent in the radial direction
For the quantitative evaluation of these effects the mixed layer measurement by the use of a magnetometer during furnace fillings and the measurement of the change in deposit angle with gas flow by the use of a 1/2 scale cold model were performed. As a result, the increase in coke layer thickness in the furnace center (ΔL_c) is expressed by the following experimental equation through the use of “formation energy of mixed layer” (E_M). ΔL_c=3.49×10^-4×E_M-136
Among factors mentioned above, the mixed layer formation was confirmed by the model to have the most significant effect on the burden distribution.

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A four electrodes method with alternative current has been developed for measurement on the electrical conductivity of ionic melts at high temperatures, especially for that of CaF₂-based slags for electro-slag remelting (ESR). The electrical conductivity was measured systematically for CaF₂-based slags containing MgF₂, BaF₂, CaO, BaO, Al₂O₃, TiO₂, ZrO₂, and CaS. From the results, the conduction mechanism of those slags was discussed in terms of molar conductivity.
The molar conductivity of CaF₂ melt was changed with the addition of alkaline-earth oxides and fluorides, such as MgO, CaO, BaO, MgF₂, and BaF₂ in accordance with the intensity of cation-anion attraction. It suggests that those additives have a tendency to behave as ionic pairs in the melt. The remarkable decrease on the electrical conductivity of the melts was observed by the addition of some oxides, such as Al₂O₃, TiO₂, SiO₂, and ZrO₂ into the melts. It suggests that those additives have a tendency to form oxyfluoride complex ions. An empirical equation was proposed for the calculation of the conductivity of multi-component slags for the ESR process.

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A 0.1%C-1.35%Mn-0.03%Nb steel was hot rolled in a single pass up to 83% reduction in thickness at a temperature between 790°C and 1 050°C and the deformation state of austenite was examined metallographically in detail. It was found that annealing twins were formed abundantly in the austenite during heating before rolling, or during recrystallization in a high temperature. Rolling at a temperature below the recrystallization temperature of austenite resulted in a severe deformation of these annealing twins. At the same time, a heavy local deformation was introduced into the regions near boundaries of these annealing twins, and also near austenite grain boundaries. Such a local concentration of deformation was found to enhance the formation of ferrite nuclei in these regions during the subsequent ferrite-pearlite transformation. It was suggested that this effect was most essential in the grain refinement of control-rolled steel.

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As one of the candidates for single specimen method to determine J_IC value, a Double Clip-on Gauge Compliance (DCGC) method was developed, by which J_IC value could be determined using only two clip-on gauges on a compact specimen. To examine the usefulness of the DCGC method, J_IC values of several kinds of steel which were determined by the DCGC method were compared with JIC values determined by the multiple specimen method specified in the JSME standard. The relationship between J_IC values determined by the DCGC method and those by the JSME method was discussed. The correlation of JIC value with the Charpy upper shelf impact energy was studied.

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Unstable ductile fracture under constant load was empirically investigated.It was confirmed that this behavior was caused by initiation and growth of the ductile crack under the load holding condition.
When this fracture process was examined by means of J-integral resistance (J-R) curve, the ductile crack growth under constant load seemed to obey the J-R curve which was determined by conventional multiple-specimen method.
If J_g is defined as minimum J value which causes the unstable ductile fracture under constant load, J_g exists between J_i (corresponding to the ductile crack initiation) and J_m (corresponding to maximum load point in displacement control test). The J_g might be one of the parameters to describe the unstable ductile fracture under the constant load condition.

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This paper describes the process for simultaneous removal of nitrogen oxides and sulfur oxides from waste gas of a sintering plant in iron and steel works. A carbonaceous catalyst is used to facilitate simultaneous removal of NO_x and SO_x.
In order to resolve technical problems accompanied by the practical application of this process, two tests were made in a pilot unit, initially with a capacity of treating 2 000Nm³/h, subsequently converted to a capacity of treating 10 000Nm³/h of flue gas from the sintering plant. Since the flue gas contained significant amounts of dust, special considerations should be given to prevent the pluggage of reactor by the dust, for which a moving bed reactor was employed. Even after the pilot unit was continuously operated for 2 000h and 1 560h respectively, at the foregoing flue gas flow rates, notable pluggage of the reactor was not observed. Tests were also made on the life-span of the catalyst. By these tests it was confirmed that the activity of the catalyst was not effected by SO_x, nor by dust components of the flue gas. Furthermore, removal efficiencies of NO_x and SO_x could be maintained at a high and constant rate of 80 to 90% and 95%, respectively.

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Penetration phenomena of nuggets in resistance spot welding of high strength stainless steels for railway passenger cars has been investigated. The results obtained were as follows:
(1) Welding current (I_4.0) required to produce a nugget of 4mm in diameter decreased with increasing cold-rolling reduction of plates.
(2) For materials which had different cold-rolling reductions, welding currents (I_4.0) required to produce the same size of nugget were different, but the electrical resistance heats required were equal.
(3) For material which had a high cold-rolling reduction and a low welding current (I_4.0), the increase of electrical resistance during welding time compensated electrical resistance heat.
(4) The sheet to sheet contact resistance did not contribute to electrical resistance heat and the electrode to sheet contact resistance did not depend on cold-rolling reduction.
(5) The conductor resistance and the spreading resistance depended on the specific resistance of material. The specific resistance increased with increasing the cold-rolling reduction. The decrease of welding current (I_4.0) with increasing the cold-rolling reduction was due to the increase of the conductor resistance and the spreading resistance. The increase of the conductor resistance and the spreading resistance with increasing the specific resistance compensated the electrical resistance heat.
(6) The increase of specific resistance with increasing the cold-rolling reduction depended on the amount of deformation-induced martensite.

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