Electron microscopy and X-ray diffreaction investigations indicate that heating rate variations have a marked influence on the path of carbonization and the nature of carbonized products. At conventional heating rates, the rate of decomposition passes through two maxima, corresponding to primary and secondary degasifications. Transformation of semicokes to low-temperature cokes is accompanied by severe intermolecular changes. The resulting cokes are not highly porous and attain a turbostratic structure, when heated to 1 500°C. At rapid heating conditions the rate of decomposition displays the primary peak only which is stronger and shifted to higher temperatures. The corresponding low-temperature coke is highly porous and exhibits a substantially high degree of molecular ordering. In heating to 1 500°C, the resulting carbon attain an average interlayer spacing of 0.442nm, a value consistent with the state of incipient graphitization.

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Samples of ternary 80%Fe₂O₃ CaO-SiO₂ systems and 77.6Fe₂O₃-CaO-SiO₂ 3%Al₂O₃ systems were sintered at 1300, 1 350 and 1400°C in air. Their disintegration, caused by the reduction at 550°C for 60min in 30% CO-N₂ gas stream, was studied and the following results were obtained.
(1) Samples studied contain only granular type hematite, reported as harmless, and yet cracks developed severely through minerals surrounding hematite crystals in some samples especially of the quarternary systems during the reduction, resulting in severe disintegration.
(2) The extent of crack development changes depending on the toughness of minerals surrounding hematite crystals and the intercrystal spacings of hematite as well.
(3) In the case of samples with low basicity, the toughness of glassy silicate decreases when Al₂O₃ is added into it or when it crystallizes during the cooling. The intercrystal spacing increases as a result of the increase in size and decrease in number of hematite crystals. In samples being satisfied with both conditions, cracks develop severely resulting in the large disintegration.
(4) In the case of samples with high basicity, the intercrystal spacing is so large that the extent of crack development depends mostly on the toughness of minerals surrounding hematite crystals. As the minerals in question increase in size, the toughness decreases resulting in the severe crack development. Al₂O₃ helps increase amounts of calcium ferrite which increases in size at 1 350°C and over.

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It is very difficult to investigate how recovery, dynamic or static recrystallization proceeds during hot rolling of steel. In the present study, a unique combination of high speed laboratory rolling mill and water cooling facility enables quenching the microstructure immediately after rooling. By using this method, process of recovery and recrystallization was studied in hot rolling of austenitic and ferritic stainless steels. Inhomogeneities of equivalent strain and recrystallization are observed through the thickness of rolled specimens. A layer of finely recrystallized grains is formed at the position of maximum equivalent strain just below the surface. The fine grains are thought to originate from dynamic recrystallization, which occurs during high reduction rolling at high temperature.

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Corrosion fatique crack growth rates as a function of the stress intensity factor range were investigated in the 3.5% NaCl aqueous solution of various temperatures between 278K and 333K under a constant applied electrochemical potential of -1050mV vs. Ag/AgCl reference electrode. Generally speaking, crack growth is enhanced as solution temperature rises. The corrosion fatique crack growth rate-stress intensity factor range curve can be divided into three distinct stages independent of testing temperature; at low ΔK levels or Range I, corrosion fatigue crack growth rate is strongly dependent on ΔK and slightly on testing temperature. In the range of moderate ΔK or Range II, the extent of which depends on testing temperature, the ΔK dependence of the crack growth rate curves disappears and crack growth rate reaches a limiting value. The apparent activation energy for the rate limit region of Range II was found to be approximately 40.0kJ/mole, which can be compared well with that for apparent hydrogen diffusion in steel. At higher ΔK levels or in Range III, corrosion fatigue crack growth rates coincide with those obtained in ambient laboratory air, indicating that the corrosion fatigue crack growth in this range is not affected essentially by the aqueous environment.

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An investigation was made on the creep fatigue life which is an important factor in the design of structural components for elevated temperature applications under severe load condition. The material used for investigation was a normalized and tempered 21/4Cr-1Mo Steel. Two kinds of prediction methods, the Life Fraction Rule (LFR) and the Strain-range Partitioning (SRP) method, were used.
After obtaining fundamental data necessary for the prediction of the creep fatigue life by the LFR and the SRP method, uniaxial creep-fatigue tests were performed under strain-controlled conditions in order to investigate the accuracy of the life prediction. Observed creep-fatigue lives were compared with those predicted by the LFR and the SRP method using stress-strain behavior obtained from both experiments and inelastic analysis.
The results were as follows:
(1) When the stress-strain values obtained from the experimental results were used, the creep fatigue life prediction agreed with the experimental values in both the LFR and the SRP method.
(2) When the analytical stress-strain behavior was used, the life prediction was very conservative in the LFR, but agreed with the experimental values in the SRP method. This is because the estimated stresses were higher than the experimental values and the calculation of creep demage in the LFR is stress-based and the damage is sensitive to the values of stress used.

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Major requirements to low temperature service steels are the resistance to fracture initiation and crack arrestability which, naturally, are required for LPG storage tanks. Low temperature service steels are classified into Al-killed steel, 2.5% Ni steel, 3.5% Ni steel and so on. A welded joint is generally not uniform but contains partially embrittled region, which often is unignorable and makes it difficult to evaluate the toughness of welded joint. In this paper, the welded joints containing embrittled regions were prepared artificially and its influence on the fracture behavior was studied. In the three point bending COD test, the small-sized specimen showed an indication of the fracture initiation when the crack tip is located in an embrittled region. However, since the probability of finding a crack tip in the embrittled region is small and the force of restraint is large when a whole welded joint is considered, fractures by a low stress seldom occur. Even under the most unfavorable condition, there is a tendency of a multi-step fracture rather than a single-step fracture.

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We have developed an automatic Charpy impact testing system and adopted it in Mechanical Test Center at Chiba Works, Kawasaki Steel Corporation.
The features of this system are as follows:
(1) Impact testing work can be performed automatically and continuously.
(2) A SCARA type robot rapidly transfers a specimen and places it in its correct position with high accuracy.
(3) Specimens are rapidly cooled to the desired temperature in a new type bath through the two kinds of process; i.e., a rapid cooling process and an accurate temperature control process by PID method,
(4) For process management the test results are promptly fed back by linking a data processing computer to a host one.
(5) One operator can control the plural systems at the same time.
(6) The manual operation to store the test result to a host computer is omitted.

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