Mr. Chairman, officers of ISIJ, ladies and gentlemen. Let me open this lecture by expressing my sincere gratitude for the honorable Asada Prize you have awarded to me today. I am particularly pleased to consider it as a recognition on the part of the iron and steel industry of what little contribution I, a man of foundry, have been fortunate enough to make towards progress of the steel industry in their attainment of world's leading position.

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For developing an optimum free forging process to close and consolidate internal cavities in heavy ingots by direct forging alone, internal deformation and internal stress were investigated with Plasticine models. First, a method to simulate the material behavior with the existence of a large temperature gradient was established. The forging processes used were the followings;
1) the conventional process which uses symmetrical upper and lower anvils
2) a process called the FM process in which the upper anvil is of the usual type but the lower anvil is flat and larger than the dimension of the material to be forged
3) a process called the FML process-where the lower anvil is the same as that of the FM process and the upper anvil is smaller than the dimension of the material to be forged
4) the so-called JTS forging process which uses the same combination of anvils as that of the FML process and is carried out with a large temperature gradient in the material.
Among these processes, the conventional process can effectively cause a large deformation rate at the center and the use of wide anvils in any process is also effective for a large deformation even without a temperature gradient in the material. For attaining compressive stress, that is, a higher hydrostatic stress at the center, it is effective even without a temperature gradient to raise the value of the parameter w/h (w: width of anvil, h: height of, forging material) or to carry out unsymmetrical reductions such as that in the FM process and the FML process. A tri-axial compressive stress state is considered to be effective for closing and consolidating the central cavities.

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Rotor bowing is a problem encountered in high pressure (HP) and intermediate pressure (IP) turbine rotors during a long term service. The problem occurred in the solid block of HP and IP turbine rotors where the main steam temperature was 566°C.
In this paper, it is indicated that such rotor bowing is caused by the metallurgical heterogeneity of materials in rotor, and that the rotor materials should be manufactured under a precisely controlled heat treatment.
The experimental results are summarized as follows:
(1) Bowing of the rotor shaft during a long term service is caused by the scatter of creep strain rate in rotor material.
(2) Difference of creep strain rate in the rotor section is caused by the non uniform temperature distribution during heat treatment.
(3) The asymmetric distribution of sulphur segregation in a rotor section has no effect on the ratio of creep strain rate.
(4) Temperature difference during heat treatment should be controlled within 6°C. In this case, the ratio of the maximum to the minimum creep strain rate in rotor shafts may be less than 1.20, and this prevents the rotor shafts from bowing during a long term service.
(5) Rotating heat treatment is effective for the prevention of rotor bowing.

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As-hot-rolled, ferrite-martensite dual-phase steels of rather simple composition can be produced by the “Dual Phase Rolling (DPR) process” which involves a low finish rolling temperature and a very low coiling temperature. Laboratory DPR experiments have been carried out using C-Mn steels and those with Cr or Si additions, to examine the effects of alloying and processing factors on the structure and mechanical properties of the processed steels. Major results obtained are as follows:
(1) To attain a sufficiently low yield-to-tensile strength ratio, the final finish pass temperature should be at about A_r3 point which varies depending on the composition, so as to bring about early separation of the alpha phase from the gamma phase before cooling starts. The coiling after a rapid cooling should be done at a temperature lower than 200°C, almost regardless of the steel composition, to suppress auto-tempering of the transformed martensite and aging of the ferrite.
(2) Both Cr and Si additions enhance the hardenability of partitioned austenite, allowing a relaxed cooling rate to obtain the martensite phases. However, Cr addition is prone to hinder the early phase separation making the gamma-to-alpha transformation sluggish. Silicon addition accelerates the phase separation, so that a wide range of finishing temperature is available.

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The Al₂O₃-SiC-C brick (the AGS brick) is the most appropriate for the wear lining of a torpedo car for desiliconizing and dephosphorizing hot metal in the car with caustic lime and iron oxide.
When desulphurization with soda ash is further added, the Al₂O₃-SiC-C brick containing superfine silicon carbide (the AGS-UF brick) exhibits even better durability. The reason is that fine silicon carbide on the brick surface is oxidized by soda ash to silica, which very quickly reacts with materials such as alumina to form a fine-textured vitreous layer, preventing Na₂O from penetrating into the brick lining.
Of all types of refractory bricks except the AGS-UF brick, the unburnt basic brick performed best in laboratory test, but was later found unusable as it developed a deteriorated structure in field test.

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Forming limit diagrams (FLDs) in simple and complex deformation paths are determined using a theoretical model of localized necking due to an initial heterogeneity of the sheet. The influence of the strain path upon the formability of the sheet is investigated using different types of FLDs under complex strain paths.
The effect of material strain hardening and strain-rate hardening is examined for several strain paths. The influence of the imperfection level on the FLDs is presented. Computer simulation of the evolution of rheological parameters during deformation and their dependence on the strain path is carried out.
The model is compared with previous experimental works, and a good agreement is obtained between theoretical results and experimental forming limit diagrams.
The mathematical model developed in this work is shown to be a powerful tool to understand and predict the plastic behaviour of metal under simple and complex strain paths.

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The reduction of dense Wustite plate was investigated over the temperature range of 600 to 1200°C, using hydrogen containing hydrogen sulphide and water vapour of various contents in such proportions that metallic iron remains stable. Sulphur in the reducing gas affects remarkably the kinetics of the reduction of Wustite and the morphology of reduced iron. The following results were obtained.
(1) In the reduction at 800 and 1000°C, sulphur in the reducing gas of content just below that for the formation of iron sulphide extensively enhances the reduction of Wustite due to the formation of porous iron rather than dense iron, and, conversely, sulphur of extremely low content compared with that in equilibrium with iron sulphide retards the reduction due to the formation of dense iron.
(2) The addition of both water vapour and hydrogen sulphide to hydrogen stops the reduction at 600°C, in spite of their low concentrations.
(3) In the reduction at 1000 and 1200°C, the reduction rate becomes smaller by the addition of sulphur, in which case the coarsening of metallic iron is observed.

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This paper clarifies the buckling strength and the deformation capacity of high strength structural steel tubes by the stub and long column tests, and the limitation of the diameter-to-wall thickness ratios (D/t) is obtained. Three series of stub columns and two series of long columns with different yield stresses are tested under pure axial compression.
The experimental results indicate that the structural characteristics of stub columns are well described by the non-dimensional parameter α_c which is; α_c=(E/σ_cy)/(D/t) for ordinary mild structural steel tubes. The limitation of D/t ratio for ordinary mild structural steel tubes can also be applied for high strength structural steel tubes as, D/t≤2400/σ_y, (σ_y in kg/mm²) More strict limitation, if a large deformation capacity is required, will be, D/t≤800/σ_y
The maximum strength of the long columns can be estimated by the Johnson's parabolic equation.

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An experimental apparatus with a batch type Fluidized bed reactor of 60mm ID for iron ore reduction was developed. The maximum reduction temperature and H₂ pressure were 900°C and 40kgf/cm², respectively. Experiments revealed that there were many operational problems to be solved and successive improvements were made. Findings obtained during the development of the apparatus are as follows:
(1)In order to keep the gas flow and pressure constant at the reduction, the performance of inlet pressure regulators was the most important and it was better to install two independent regulators for high and low pressure ranges.
(2)In order to decrease the pressure change brought about by switching the gas flow from N₂ to H₂ at the start of the reduction, it was effective to install two independent outlet pressure regulators for N₂ and H₂.
(3) When pressurized Ar was introduced to the space in the electric furnace of external heating type to get the pressure balance with the reactor, heating efficiency of the furnace was found to decrease seriously because of enhanced heat leakage.
(4) Sufficient gas preheating was very effective for fine control of the reduction temperature in the fluidized bed and also for prevention of the sintering trouble of the reduced iron powder at higher reduction temperature.

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Direct reduced iron (DRI), with its sponge-like structure, is chemically reactive and easily oxidized. The author has developed an efficient process for the treatment of DRI, known as the Waxing Process, which makes the DRI resistant to both oxidation and corrosion. According to this process, DRI from the last stage of reduction is transferred into a bath of melted paraffin held at a temperature of 110-120°C and kept for 3-5 sec in it. To check the efficiency of the Waxing Process as inhibitor for reoxidation and corrosion of DRI, several tests are carried out and the results are shown.

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