In order to theoretically evaluate and show the effect of REM and Casulfides on heterogeneous nucleation, investigations have been made to find how REM addition influences the solidification microstructure of ingots and continuously cast slabs.
Some characteristics of REM-added steel compared with ordinary steel are as follows; (1) Primary dendrite arm spacing is narrower. (2) Primary dendrite arm length is shorter. (3) The growth direction of dendrite arms is less oriented. (4) The micro-segregation of C, S, P, Si and Mn is less.
It is concluded that new primary dendrite arms are generated due to the heterogeneous nucleation by REM addition in the region of comparatively small supercooling near liquid-solid interface.

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Investigation has been made to evaluate the effect of REM addition on the solidification macrostructure of commercial ingots and continuously cast slabs. The results are as follows:
(1) REM addition brings about diminution of macro-segregation, enlargement of equiaxed zone, and reduction of loose structure.
(2) Also, the starting position of the formation of the inverse V-segregation moves toward the center of ingot and the segregated area expands. The length of segregation line and the segregation ratio are reduced.
(3) Autoradiographic observation does not show large differences in macrosolidification rate. However, mushy zone at the bottom of an ingot is formed earlier.
(4) REM-oxides, sulphides, and oxysulphides are mainly precipitated in dendrite arms. The constituents of inclusions are varied depending on the methods of REM addition.
Non-metallic inclusions formed by REM addition seem to act as nucleation catalyst and thus improve not only the microstructure but also the macrostructure of the casts.

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The present experiment has been made with two purposes.
One is to make a precise analysis of textures of cold rolled and recrystallized mild steel sheets by means of a three-dimensional orientation distribution function (ODF). The materials used, are aluminium killed steel sheets and rimmed steel sheets.
The other is to find a quantitative relationship between the anisotropy of mechanical properties of those sheets and the textures represented by the ODF. Young's modulus, Lankford value and propagation velocities of elastic waves are chosen as the mechanical properties and they are related to the ODF by the method proposed in this study.
For the texture analysis, the development of the recrystallized textures is reasoned systematically. The preferred orientations in the recrystallized texture are also made clear by the ODF. The calculated values of the mechanical properties are all in good agreement with the experimentally obtained ones, that is, of Young's modules, Lankford value and the propagation velocity. The square of the propagation velocity is also correlated with the averaged Lankford value as theoretically predicted.

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Systematical investigation has been conducted on the influence of impurities, alloying elements, and grain refining elements on the strength at elevated temperature and the temper embrittlement of 21/4Cr-1Mo steel.
Impurities such as P, Sb and Sn markedly increases the degree of the embrittlement. C content, cooling rate at quenching, and strength level also have a great effect on it.
The addition of grain refining elements and rare earth metals decreases the susceptibility to the temper embrittlement, while elements effective for strength at elevated temperature generally increases the susceptibility.
A combined addition of Ti, B and rare earth metals to 21/4Cr-1Mo steel induces both the high strength at elevated temperature and lesser degree of susceptibility to the temper embrittlement.

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The effect of pre-strain on intergranular stress corrosion cracking (IGSCC) susceptibility of Type 304 stainless steel has been studied using a constant load tensile specimen in 288°C water containing 26ppm dissolved oxygen. The results obtained are summarized as follows:
(1)The time to failure of the specimens pre-strained at room temperature or 288°C are longer than those of non pre-strained specimens.
(2) The stress-strain behaviour of materials changes by pre-straining. The effect of pre-strain on IGSCC initiation could be explained in terms of a relation between the rupture of surface oxide film and the stress-strain behaviour of materials.

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Considering the radial distribution of state variables in the blast furnace, a new mathematical model of the blast furnace was developed. This model consists of heat and mass balance equations under the existence of three phases (gas, solid, and liquid) and the equation of motion for gas. Assuming stream-lines of solid and liquid, the characteristic method was employed to solve these equations simultaneously.
By the use of the mathematical model, the following results were obtained.
(1) The calculated isothermal line (1400°C) is similar to that of quenched blast furnace.
(2) The distributions of temperature, composition, and mass velocity in the upper part of the shaft are strongly affected by the O/C distribution.
(3) In the lower part of the blast furnace, the dead zone which plays as a heat reservoir has the significant influence on the formation of the inverted V-shaped cohesive zone.

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Stress corrosion crack growth rates were measured on modified wedge-opening load (m-WOL) type specimens of three experimental Ni-Cr-Mo low-alloyed steels in room temperature synthetic sea water. The effects of the cathodic electro-chemical potential of about -980mV vs. Ag/AgCl reference electrode applied by coupling the specimen with Zn-anodes upon crack growth behaviors and upon the threshold stress intensity factor, K_Iscc, for stress corrosion cracking were investigated. The threshold stress intensity factor for cracking decreases slightly by the cathodic polarization in comparison with that under the freely corroding condition for all the steels tested, showing a tendency to converge with each other for a longer testing duration than over 9000h. The test using the cathodically polarized m-WOL specimen is, therefore, able to be applied as an accelerative method to estimate the threshold stress intensity factor, K_Iscc.

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Investigation of the delayed fracture characteristics was made with high strength bolts tightened on the fixture plate and exposed to rural and coastal industrial zones, fresh water, and seawater respectively for about nine years. At the same time, bolt materials subjected to the same heat treatment as the exposed bolts were submitted to four types of accelerated testing in laboratory. Both bolts and bolt materials are composed of seventeen grades of low alloy steels having tensile strengths ranging from 80 to 140kgf/mm².
The results of observations are:
(1) Neither failure nor cracking was found in bolts with tensile strength less than 120kgf/mm².
(2) Since the critical strength above which delayed fracture initiated in bolts exposed agrees with that obtained from accelerated laboratory tests, it is considered that the critical strength for crack initiation can be determined by accelerated laboratory tests and the critical strength for crack propagation can be examined by exposure test of tightened bolts.
(3) High atmospheric temperature, large amount of rainfall and excessive nut turning promote a delayed fracture in bolts.
(4) Cracking along prior austenite grain boundaries and the results of analysis of corrosion products on the bolt surfaces suggest that the occurrence of delayed fracture is attributable to hydrogen.
(5) There is a difference in the effects of Zn plating, Cd plating and Zn base phosphate coating on delayed fracture between exposure tests and accelerated laboratory tests.
(6) The applied axial load on bolts tightened exceeding their yield strength and then exposed for about nine years is decreased approximately by 10%, in addition to 3 to 8% initial decrease occurred immediately after tightening. Delayed failure of washers had no effect on residual
axial load in bolts.

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