Coke degradation has a great influence on the blast furnace operation. Coke gasification behavior with CO2 gas was investigated by coke gasification experiments and the mathematical model calculation. Cylindrically shaped coke was exposed to the CO/CO2/N2 atmosphere, at the temperature of 1473K or 1773K, then it was filed layer by layer to measure the gasification behavior. Coke gasification occurred preferentially at the surface of the coke with higher temperature or higher coke reactivity. Mathematical model of coke gasification clarified that the specific surface area of fine pores and the temperature had a great influence on the coke gasification behavior, which was expressed as α, the gasification ratio gradient inside the coke lump.
The lubrication by various cereal flours, such as wheat flour, rice flour, and so on, was studied to develop a nonpolluting lubricant for sheet metal forming. The lubricants were prepared in the following way. (1) Each cereal flour was dissolved in water at several concentrations. (2) Each suspension was coated on a titanium sheet. (3) The specimens were dried and cereal particles, thus, remained on the both surfaces of a specimen. The performance of these lubricants were evaluated by the Erichsen cupping test. Most of the flours show higher Erichsen values than grease. Furthermore, the cereal particles on the deformed specimens were observed by scanning electron microscopy, and analyzed by electron probe microanalyzer. The observations suggest that the starch particles covered with protein and lipid can reduce the friction between dies and a specimen.
Metal powders produced by mechanical milling show the specific microstructures and properties. With these merits preserved, the powders should be combined into a large size compact. Saito et al. and Kimura et al. have succeeded in consolidating the iron powders into 12.5 mm thick sheets by sheath rolling at a relatively low temperature of 973K. Based upon their success, we have attempted to apply caliber rolling for consolidating the powders into a large bar (φ11 × 1 000 mm). The sheath can was filled with pure iron powders, sealed in vacuum, and then rolled. When the rolling temperature was 973K, rolling reduction of more than 80 % was enough to make sound compacts of >10 mm diameter with fine microstructure and relative density larger than 99.6 %. When the rolling reduction was 90 %, the consolidation was accomplished in a wide range of rolling temperature between 1 273K and 823K. At 823K and 873K, the sound consolidation could be realized without recrystallization. The tensile properties were better than those of the HIP treated compact. Hence, the solid-state joining is confirmed to occur much easier in the present method than in the HIP method.
This study was performed to determine the influence of nitrogen addition on HAZ cracking susceptibility in fully austenitic stainless steel SUS310. The nitrogen content varied from 0.023 to 0.325%. The HAZ cracking behavior of nitrogen-containing stainless steels were investigated using the bead-on plate welding, the Gleeble test, and the isothermal liquation test. According to the cracking test, it was found that the HAZ cracking susceptibility in the SUS310 alloy decreased with increasing the nitrogen addition. The Gleeble and the isothermal liquation test revealed that the HAZ cracking was closely related to the intergranular liquation caused by Si and P segregated at the grain boundaries, which has the much lower melting point than that of the γ-matrix. The degree of intergranular liquation in the high nitrogen containing specimen was less than that of the low nitrogen containing specimen due to the decrease of Si and P segregation at the grain boundaries, which seems to be responsible for less liquation cracking susceptibility in the high nitrogen containing specimen.
Various characteristics of biaxially oriented polyester film that is laminated on to steel for can use are controlled by the degree of biaxial orientation and the thickness of amorphous layer of the laminated film. The adhesive property and the corrosion resistance of the steel deteriorate with increasing laminating speed because of decreasing thickness of amorphous layer even at the same degree of orientation. We found that it is effective to maintain the enough contact cooling time of laminated film in order to prevent the amorphous thickness reduction. Because high speed laminating is indispensable for the better productivity, it is important to find the method of keeping the contact cooling time constant. Therefore, this report deals with the result of numerical analysis applied to characterize heat transfer in new laminating process, which was considered and accepted to maintain the contact cooling time by winding the steel along the laminating roll for prevention of decreasing thickness of amorphous layer with increasing laminating speed. Based on the result of numerical analysis, we obtained the transient crosssectional temperature distribution of polyester film in the laminating process compared with the ordinary laminating process. The thickness of amorphous layer with the numerical analysis obtained by the cross-sectional variation of maximum temperature of film in the roll nip agrees well with the one observed by polarizing microscope. The estimation of the thickness of amorphous layer was found possible by this method with a good accuracy. The variations of biaxial orientation of the laminated film on non-contact side after leaving roll nip in this laminating process is also discussed.
The necessity to substitute functionally disordered hard tissues like bone and teeth with the orthopedic implant instrumentations like artificial hip joints and dental implants is growing because the population of old persons is rapidly increasing. New β-type titanium alloys composed of non-toxic elements with high strength and low modulus of elasticity were, therefore, designed. In general, it is known that the wear resistance of conventional biomedical titanium alloys are lower than that of conventional biomedical alloys like Co-Cr alloy and SUS 316L stainless steel. Friction wear of orthopedic implant materials is a significant clinical problem. The loosen orthopedic implants cause pain and restricted action. Friction wear characteristics of the newly designed β-type titanium alloys and typical conventional biomedical alloys like Ti-6A1-4V ELI, Ti-6A1-7Nb and SUS 316L stainless steel were, therefore, evaluated in air and Ringer's solution using a ball-on-disc type friction wear testing system in this study. As compared to the conventional biomedical titanium alloys like Ti-6A1-4V ELI and Ti-6A1-7Nb, the newly designed β-type titanium alloys show excellent wear resistance when zirconia ball is used as a mating material, while opposite trends are observed when alumina ball is used as a mating material in air and Ringer's solution. The adhesion and exfoliation of wear particles on the wear grooves and plastic defor-mation of substrate under the wear grooves were observed in the newly designed β-type titanium alloys. It is considered that the different wear mechanisms will be main cause for different wear characteristics between the newly designed β-type titanium alloys and conventional biomedical titanium alloys like Ti-6A1-4V ELI and Ti-6A1-7Nb.
Ferritic heat-resisting steels are planned to be applied to ultra supercritical power plants. In this study, creep-fatigue properties for base metals such as Mod.9Cr-1Mo, 9Cr-2W, 12Cr-2W, newly produced Pd-added ferritic steel and oxide dispersion strengthened ferritic steels and for welded joints of two kinds of the ferritic steels were investigated. The creep-fatigue lives of the base metals, tested by trapezoidal strain wave shape with 3 hr-hold at tension side, were dependent on the kind of the materials and had a good correlation with the reduction of area for each material in the creep rupture tests. The creep-fatigue lives for welded joint of 12Cr-2W and 9Cr-2W steel plates were about 70%, compared with the base metals. The welded joints were fractured at fine-grained HAZ (heat affected zone).
Tatara was a Japanese traditional process for producing mainly pig iron, with so called "Zuku" and bloom, so called "Kera", from iron sand and charcoal using box type furnace with 1.2 m height and intermittent blowing air. The modified tatara furnace has been examined for investigating on the production mechanisms of "Kera". A bloom of "Kera" was produced in the bottom of furnace. Carbon in Kera was analyzed to be 0.432.41 mass%, and the oxygen content was 0.0120.026 mass%. Iron sand was reduced above tuyere, followed by absorbing carbon on fired charcoals in front of the tuyere at about 1550K. The characteristics of tatara process are low temperature of about 1550K for absorbing carbon into steel. The reactions were carried out under nonequilibrium of C+ O = CO reaction.