Studies relating to origins of oxide growth stresses, principles of stress measurement, stress systems established in the oxidizing specimen, and methods of stress-measuring are critically reviewed. The results of stress measurement conducted to date have been compiled into a table for ready reference.

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Local and bulk bath motions in injection refining processes have been studied in water-model experiments involving gas injection through a single axial tuyere located at the bottom of a cylindrical vessel. The ratio of gas kinetic energy to buoyancy energy was changed, under constant gas flow rates (Q), by using nitrogen or helium and also by changing the tuyere diameter. During the gas injection, the flow velocity in the plume zone was measured at three different locations and the shear stress on the bottom surface of the vessel was determined at nine radial positions from the tuyere, by an electrochemical technique. It has been found that the shear stress near the tuyere is proportional to Q^0.87 irrespective of the magnitude of the kinetic energy of the gas. The latter variable does have a significant effect, however, on the occurrence of channelling and the liquid velocity in the plume zone. The shear force was calculated by numerically integrating the measured shear stresses over the entire bottom surface of the injection vessel, and was used to interpret the bulk bath motion. The shear force has been found to be proportional to the gas buoyancy energy to the power of 0.63 in accord with the theoretical prediction of 0.67 for the exponent.

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A new apparatus f or the determination of dif fusible hydrogen in steel has been developed by using a gaschromatograph, a thermal conductivity detector, and a sequencer.
The characteristics of the apparatus are as follows:
(1) The lower limit of detection is 10^-5ml (N.T.J.), that is 5× 10^-4ppm for 2g specimen.
(2) The minimum cycle time of measurement is 3min.
(3) Fifteen samples can be measured in parallel when the measurement is carried out every one hour.
(4) The measurement shown above is automatically carried out by a programed sequencer.
(5) The coefficient of variance of results (approximately 4ml/100g) is about 1%.
The apparatus is useful not only for determination of dif fusible hydrogen in weld metal but also for determination of diffusivity of hydrogen in iron, alloyed-steel and thin foil of amorphous iron and for measurement of permeability of hydrogen through steel.
It was also revealed that for low hydrogen content specimens the glycerin volumetric method gave much lower results than those obtained by the present method.

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Three solution methods for thermo-elastic plastic finite element analysis were studied with special emphases paid to the treatment of elastic-plastic transition. These are the iterative convergent method using “effective stiffness matrix” and two modified r_min methods I and II. The computational results obtained were compared with each other in terms of the “followability” of the equivalent stress and the flow stress of the material.
A simple and efficient algorithm to automatically determine time increment was also presented. It was shown that when this algorithm is combined with the modified r_min method II highly accurate solution can be obtained with less thermal load increments.
Computations were performed on the basis of the modified r_min method II on centrifugal casting molds to analyze the influences of casting parameters on the stress-strain state of the molds.
The results revealed the importance of the adiabatic effect of refractory coating to enhance the thermal fatigue resistance of the bore surface of mold. The influences of the pouring temperature, the mold wall-thickness and the preheating temperature of mold were also clarified.
Mold warping or bowing was also discussed in conjunction with the “plastic work over a mold”, which was found to be decreased considerably by increasing the thermal resistance of coating, by lowering the pouring temperature and by thickening the mold wall.

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The effects of the addition of trio impurity elements (sulfur and titanium) and of the solidification rate on the graphite structure of iron-graphite eutectic were investigated by the unidirectional solidification method. The effect of sulfur and titanium on the transition of lamellar-colony-eutectic cell is discussed.
The rosette graphite was formed by the fine/coarse transition in a eutectic cell. The f ormation mechanism of rosette graphite was studied.
The effect of sulfur or titanium on the intergraphite spacing was also studied.
A diagram of the unidirectional solidification structure was drawn from the observation of graphite structure which was changed with the solidification conditions and additions. This diagram will be useful in obtaining some f undamental knowledge of graphite structure formation.
New material layer graphite cast iron plate-was made by using the unidirectional solidification technique and hot rolling. The physical anisotropic characteristics are described.

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A new method for measuring the thickness of molten powder on the molten steel in the continuous casting (C.C.) mold was studied.
The authors found that the molten powder thickness could be determined by using an eddy current sensor with two frequencies.
This method is based on the difference in electric resistivity between the molten powder and the molten steel. The resistivity of the molten powder, though varying slightly with viscosity, is almost stable above the temperature of 1 300°C. As a result of the experiment, the measurement accuracy was found to be within ±1-2mm.
The authors are now studying the relation between the molten powder behavior and the CC. operational conditions by using this method.

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The effect of the Thermo-Mechanical Control Process (TMCP) on the properties o f high-strength low alloy steel has been examined and the following results have been obtained.
The addition of niobium or titanium, especially the combination of niobium and boron is effective for TMCP. Low-temperature toughness of TMCP plate is not significantly influenced by the cooling conditions, but is mainly determined by the controlled-rolling (CR) conditions. TMCP alters the microstructure from ferrite-pearlite to fine-grained ferrite-bainite and consequently increases the strength without a loss in low-temperature toughness, compared with CR process.
The advantages of TMCP plate are a decrease in the carbon equivalent, improvement of HIC resistance and an increase in the impact energy.

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Fe-P alloys containing up to 0.67wt% phosphorus show intergranular fracture (IGF) by an impact test after quenching from 1073K. Additions of up to about 0.01wt% of carbon to the alloys prevents the intergranular fracture caused by the grain boundary segregation of phosphorus, and lowers the ductile-brittle transition temperature (DBTT). This effect is due to the segregation of carbon at grain boundaries. Aging at 873K of the quenched specimen with 0.52% P and 0.0008% C lowers DBTT and increases the degree of grain boundary segregation of carbon while it does not affect the degree of grain boundary segregation of phosphorus. The grain boundary segregation of carbon strengthens the grain boundary cohesion and prevents intergranular fracture without removing phosphorus from grain boundaries.
DBTT of the Fe-P-C alloys are analyzed in terms of the degree of grain boundary segregation of carbon and phosphorus and the solution hardening by phosphorus (the bulk concentration of phosphorus). The site-competition between carbon and phosphorus is taken into account in the calculation of the degree of segregation. It is found that the increase in the boundary cohesion by the carbon segregation is an important factor in preventing IGF.

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Superplastic behavior of δ-ferrite/austenite duplex stainless steels has been studied by means of isothermal hot tensile test at temperatures (T)from 700 to 1100°C at initial strain rates (ε) from 10^-4 to 10^-1 s^-1 in relation to microstructural aspects prior to and during deformation. Superpiastic elongations were observed in wide ranges of T and ε. The maximum elongation greater than 2500% was obtained under the condition where c phase precipitation occurred during deformation. The elongation depended on the precipitation rate of c phase especially in the lower temperature deformation as well as on the prior microstructure. The most suitable microstructure obtained for superplasticity was fine grained δ-ferrite matrix with fine dispersion of γ particles. In the deformation of the specimens with such optimun microstructure, elongations greater than 200% were obtained at T≅1000°C even at ε_??_10^-1s^-1. During superplastic flow, the large microstructural changes were observed. At above 1000°C γ phase was separated and was refined into spherical particles within the δ-ferrite matrix and at temperature below 1000°C, a γ/σ mixed structure was formed by the eutectoid decomposition of δ-
ferrite, resulting finally in the stable equiaxed micro-duplex structures with δ/γ and γ/σ, respectively. Such microstructural changes can play an important role for the superplastic behavior in addition to the effect of m-value.

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For the quality control of butt welding pipe mill, the skelp temperature, the squeezing upset and the flow rate of oxygen from the welding form are the most important factors for welded seam strength.
The mill has already equipped with a skelp widthwise pyrometer between the edge induction heater and the 1st stand. The edge heater is controlled to adjust the skelp edge temperature. However, this pyrometer is not adequate enough to control the welding condition.
In order to improve the product quality, an observation and temperature monitor system of the welding part has been developed.
This system is available to the quality control of butt welding pipe mill, the edge heat unbalance of skelp and seam weld strength is able to estimate and be controlled correctly.

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