Seismic vibration analysis was made on two- and three-dimensional models of the No. 4 blast furnace at the Kimitsu Works of Nippon Steel Corporation, using the seismic waves that had been recorded when a big earthquake occurred off the East Coast of the Izu peninsula. The study led to the establishment of appropriate seismic vibration analysis models to reproduce the observed seismic waves and the disclosure of the following facts. While combination of two-dimensional models is sufficient for the earthquake-resistant design of the furnace-supporting structure, three-dimensional models are necessary for the furnace-top piping. While the connection of the furnace body and supporting structure at the furnace top induces the whiplash phenomenon, the connection of the top of the supporting structure and furnace-top piping serves as a means to reduce it. By elastoplastic analysis, it was also ascertained that the furnace-supporting structure had the ultimate lateral shear strength required by the Building Standards Law of Japan.

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A basic study was conducted on the decarburization of high chromium molten iron in a small high-frequency induction furnace under top-and-bottom combined blowing conditions. As a result, the following facts became obvious.
(1) Decarburization is classified into stages I and II. The critical carbon concentration, transfer from stage I to stage II, decreases when the oxygen supply rate is restrained or when the bath stirring intensity is increased.
(2) At stage I, when the oxygen supply rate is decreased, although the decarburization rate decreases, the Cr loss also decreases. And when the bath stirring intensity is increased, the Cr loss decreases, and the decarburization rate increases. The Cr loss is determined by the balance of the bath stirring intensity and the oxygen supply rate from the top lance.
(3) At stage II, the decarburization rate and the Cr loss are also determined in the relation to the oxygen supply rate and the bath stirring intensity, but as the rate of decarburization is controlled by the transfer rate of carbon to the reaction zone in the bath, the Cr loss increases with progress in the decarburization.
(4) The total oxygen content in the bath during blowing becomes gradually larger than the dissolved oxygen content as [%C] decreases, and the suspended oxides, the composition of which is similar to FeO•Cr₂O₃, appear in the bath correspondingly.
(5) Coarse oxide particles exist on the bath surface in the low carbon period. Fine oxide particles of FeO•Cr₂O₃ are observed to form from the coarse particles and to be dispersed into the bath.

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Thermal recovery processes in the STB (Sumitomo Top and Bottom blowing) process have been developed and the refining characteristics have been investigated. Postcombustion process in a STB converter has been developed, applying the results of fundamental tests by a 15t STB converter to a commercial scale 160t STB converter. And then coal injection process through a top lance was combined with postcombustion. The results are as follows:
(1) A lance of the two-independent-flow type is essential to postcombustion.
(2) The jet angle θ₂ for postcombustion should be wide as 30-35 deg.
(3) The oxygen flow rate through PC nozzles should be about 20% of the total oxygen flow rate.
(4) The thermal recovery efficiency of postcombustion is very high, nearly 100% in a 15t STB converter and 70% in a 160t STB converter.
(5) Although postcombustion causes no change in % (T.Fe) in the slag at the end point, it increases (Fe³⁺) in the slag and improves dephosphorization of the hot metal.
(6) The large amounts of heat can be effectively used to improve the heat balance in a converter by using the TAPS (Triple Action Process of STB; coal injection from a top lance with postcombustion).
(7) In the case of the TAPS, as the coal injection interferes with postcombustion, it is necessary to inject coal effectively within a short time.

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A liquid helium temperature fatigue testing system was developed at the National Research Institate for Metals, Tsukuba Laboratories. The system is equipped with a recondenser intalled in the test machine cryostat, whereby the helium mist is transferred to the recondenser from the refrigerator and the evaporated helium gas is recondensed in the cryostat. Thus, the liquid helium level in the cryostat is kept constant without an additions supply of liquid helium during testing. A continuous operation of more than 460h has been achieved with this fatigue testing system.

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An engineering interest to develop an electroplating cell which assures uniform alloy plated coastings at high current density has initiated this study. Due consideration should be given to a number of design factors, such as anode length, electrode separation gap, fluid injection and its control. Emphasis is focussed on the effect of oblique fluid impingement in terms of streamwise uniformity of alloy deposits along the cathodic strip.
Zn-Fe alloy electroplating from sulphate bath was performed in a rectangular flow channel cell with interchangeable fluid injection angle under galvanostatic conditions. Streamwise variation of Fe content and crystal phase/structure of Zn-Fe alloy deposits revealed non-uniform distribution for wall jet flow system compared with that of parallel flow system, which would be an indication of difference in local mass-transfer rate along the cathode. In case of inclined fluid injection, Fe content in alloy film increased with increasing distance from the incident point, eventually coasting to a plateau corresponding to the value of parallel flow system, which may reflect the downstream transition of turbulent velocity profiles from wall jet flow to Poiseuille pipe flow.
Codeposition of trace indicator ion during anomalous alloy deposition in a parallel plate rectangular cell was found to be a first-order rate process, which exceedingly showed promotion of mass transfer at the cathode presumably owing to simultaneous evolution of hydrogen gas. Such enhanced mass transfer implies a key role for the bubble stirring effect in the concentration boundary layer in the vicinity of cathode surface, which seems to give rise to dense and adhesive electrodeposits ensuring successful operation of alloy electrodeposition at high current densities.

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An electromagnetic acoustic transducer gauge has been developed for the measurement of hot seamless steel tube wall thickness. The system consists of a tunnel type electromagnet which generates the strong axial magnetic field around the pipe, and 6 sensors including transmitting and receiving coils which are arranged between poles encircling the pipe. The gauge can measure the wall thickness of pipe at 6 circumferential points with the rate of 250Hz.
The ultrasonic characteristics in hot steel such as velocity and sensitivity have been investigated. The measuring accuracy of the gauge has also been investigated in the laboratory and at the No. 1 tube making plant in the Kainan Steel Tube Works of Sumitomo Metal Industries, Ltd. The basic experiments showed that the ultrasonic velocity can be calculated by measuring the surface temperature, and that the sensitivity changes due to the change of air-gap and surface temperature can be compensated by AGC (automatic gain control) circuit.
The system was positioned at the exit of finishing stand of stretch reducing mill, and pipes of various sizes (42.7mm-177.8mm dia.×3.2-25mm thickness) were rolled to measure the wall thickness. The results showed that the measuring accuracy was less than ±0.1mm.

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Fatigue, creep and cyclic creep tests have been carried out at 800°C for the variously heat-treated nickel-base superalloy Inconel 751. The heattreatments given are simple aging (SA), two-stages solution treatment (TS) and direct aging (DA), with and without coating of synthetic ash mixture composed of 90% Na₂SO₄ and 10% NaCl. Effect of grain boundary topography, particularly of the serrated grain boundary produced by the direct aging, on the strength properties is, then, investigated.
It is clarified that hot corrosion can alter the fracture mechanism completely. In hot corrosive environment, a stress-enhanced aggressive intergranular penetration of sulfides, oxides and/or chlorides can cause a grain boundary weakening to induce a premature intergranular fracture in a brittle manner regardless of the grain boundary topography. In particular, the cyclic creep is shown to result in minimization of failure life in hot corrosive environment because the combined creep and fatigue loadings promote the aggressive intergranular attack, in contrast to the case in air in which the failure life is mainly determined by the creep damage.
In general, the effect of grain boundary topography on the strength properties is significant in hot corrosive environment rather than in air. In hot corrosive environment, both the chromium-depleted zone and the straight grain boundary appear to enhance the aggressive intergranular attack, because the former can induce the low melting nickel sulfides formation and the latter is easily subjected to the locally increased strain concentration so as to provide a stress-activated path. The development of the chromiumdepleted zone tends to give a detrimental effect on the strength properties under all the loading conditions, while the detrimental effect of the straight boundary is more pronounced under the creep-dominant loading conditions. Consequently, in order to improve the strength properties in hot corrosive environment, it is important to eliminate such undesirable microstructures associated with the grain boundary, depending on the loading conditions.
It is also confirmed that even in hot corrosive environment, the serrated grain boundary contributes notably to improve the strength under creepdominant loading conditions by virtue of the suppression of such an aggressive intergranular attack.

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A statistical method for quantitativeevaluation of segregation is introduced. The method is used to evaluate the dendrite arm spacing, objectively. Two indices which are quantitative measures of the spacing and intensity of segregation are newly proposed and are employed in the quantitative evaluation of center segregation and intergranular segregation. The effects of electromagnetic stirring (EMS) and calcium treatment on segregation are studied. The equiaxed structures formed by the application of EMS and by low casting speed in continuous casting steel slabs are quantitatively compared with each other.
From the examination of the specimens the following results have been obtained.
(1) Intergranular segregation is intensified by the application of EMS, even though the center segregation is suppressed.
(2) The equiaxed structure brought about by EMS is finer than the one caused by low casting speed.
(3) Calcium treatment is very effective in suppressing both the center segregation and the intergranular segregation of sulfur.

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