Experimental and theoretical studies were made to confirm the usefulness of the oxygen blast furnace presented in the preceding reporti which is characterized by the combined injection of pulverized coal in a large amount to prevent the excessive increase of the flame temperature and following results were obtained. 1) In the operation of the blast furnace test plant with the production capacity of 15 t/d, such a large amount of pulverized coal as 1.2 kg per 1 m3 of blast oxygen was injected without any problem and the coal rate of 407 kg/t, the coke rate of 258 kg/t and the productivity of 7.35 t/d/m3 was achieved as an operation result. 2)By one dimensional blast furnace mathematical simulation model, it was predicted that the coal rate of 375 kg/t, the coke rate of 180 kg/t and the productivity of 3.3 t/d/m3 can be achieved in a commercial scale blast furnace.
The influence of the inner wall profile on the descending and melting behaviors of burden were analyzed by using a three-dimensional semicircular warm model of the blast furnace under conditions set as similar as possible to the physical phenomena in the furnace. In the case of a profile with blocks installed on the belly where the horizontal stress acting to the wall is at its maximum, a sluggishly descending zone of a thickness 25 times of the projecting length of the blocks is formed near the wall just above the blocks. The thickness of the sluggishly descending zone near the wall increases with increasing projecting length of the blocks on the wall and with decreasing installation interval of distance between the blocks and it decreases with increasing ore/coke near the wall. The height of the dead man decreases with the formation of the wall sluggishly descending zone due to the blocks on the wall and dead man temperature decreases. For decreasing the thickness of the sluggishly descending zone near the wall, the ore/coke near the wall should be preferably increased as far as the heat-flow ratio is permitted. Such a burden distribution is effective for high-rate pulverized coal injection operation in which the melting capacity near the wall is large.
The interior of a blast furnace is excessively cooled down if wall bricks fall off from the front of staves by damage or deterioration. We built an experimental apparatus that can heat a wall from one side and cool it from the other side so that the reduction and disintegration of sinter by this cooling effect can be simulated. The temperature distribution in a lumpy zone was analyzed based on a proposed model. It was found that the disintegration of sinter was accelerated by a delay in reduction caused by a strong cooling with an overall coefficient of heat transfer greater than 20 kcal/m2·h·°C. This implies that the disintegration of sinter in blast furnaces proceeds remarkably near the wall, resulting in a periphery gas flow distribution.
Transport rate of gaseous phosphorus into solid iron under a reducing atmosphere was observed by a weighing method, to obtain fundamental data to discuss transport mechanism of phosphorus into reduced iron in a blast furnace. A kind of killed and rolled steel sheet and non worked electrolytic iron sheet were used. Partial pressures of phosphorus vapor were controlled by using equilibrium relation between Ca3 (PO4)2, SiO2, C, CaSiO3 and CO. Phosphorus partial pressure and temperature were every one order between 4×10-6 and 4×10-2 atm, and every 50°C between 900 and 1050°C, respectively. Experimental results are as follows: 1. The transport rate obeyed a parabolic rate law. 2. Relations between the rate constant of the parabolic rate law, κ, phosphorus partial pressure, PP2, and temperature, T, are as follows: In the case of killed steel, logk=0.14 logPP2+5.68-15.6×103/T In the case of electrolytic iron, logk= 0.14 logPP2+4.94-15.6×103/T 3. Reaction product on the surface of the solid iron was Fe2P.
A variety of α-β titanium alloys were produced by the microstructure-controllable new Blended Elemental (BE) P/M method, in which as-sintered material is water-quenched from the β-phase region prior to HIP 'ing, with emphasis on relating composition/processing/microstructure to mechanical properties. Alloy composition was found to have a strong effect on the microstructure. In near α type α-β alloys such as Ti-6Al-2Sn-4Zr-2Mo, the new BE method created a fine two phase structure in a relatively small β grain with lower aspect ratio α-platelets. This microstructure resulted in improved high cycle fatigue strength compared to those for conventional BE alloy. In contrast, in β-rich α-β alloys such as Ti-5Al-2Cr-1Fe, a massive α phase was formed on prior β grain boundaries. In this case poor improvement in fatigue strength was obtained because of the presence of this massive α. High temperature mechanical tests done on near α type alloys revealed that both creep resistance and low cycle fatigue strength were superior in new BE material than in conventional BE material. These findings demonstrated that the new BE method applied to near α type α-β alloys can give rise to better balance of mechanical properties compared with that of ingot metallurgy.
Effect of cooling rates after β treatment on microstructures in an α titanium alloy, Ti-5Al-2.5Sn, is examined. At the cooling rate of 300°C/s, no grain boundary α phase is observed and lath type of plate structure is formed throughout the specimen. In the lath plates, highly dense dislocations are included, and Fe-enriched β phase is retained between lath plates, which indicates that both shear and diffusional components of transformation operate during cooling. At the lower cooling rate (≤4°C/s), structural dislocations other than β phase are observed between α plates. It is considered to be due to the coalescence of two adjacent α plates which have slightly different crystallographical orientations each other. At the cooling rate of 0.1°C/s, ring-like diffuse streaks and extra spots which are related to ω phase are detected in the diffraction pattern of Fe-enriched β phase. Furthermore, aging treatment at 550°C for 24 h after cooled from β region at the cooling rate of 300°C/s produces the refined equiaxed structure containing sub-grains, recrystallized grains and β phase at the triple points of α (sub-) grain boundaries.
Hot rolled steels with different C contents ranging from 0.14% to 0.72% were subjected to hot band annealing, where two annealing conditions were applied in order to regulate the distribution and size of cementite. These steels were cold rolled and box annealed for recrystallization. The recovery and recrystallization process during annealing was investigated. When cementite was coarsened prior to cold rolling, the recrystallization temperature was lowered by the increase of C contents. This was attributed to the acceleration of random nucleation of recrystallized grains in the vicinity of coarse cementite which increased with the C content. In each steel, the texture tended to become random during recrystallization in the final annealing. On the other hand, when cementite is fine, the recrystallization temperature became high. In this case, the increase of C content causes a rise in recrystallization temperature, and the components in the cold-rolling texture were retained even after primary recrystallization. Large amount of fine cementite would have depressed the growth of recrystallized grain.
Effects of phosphorus content and boron addition on impact toughness of medium carbon steels with an ultra-high strength level over 150 kgf/mm2 have been investigated. The toughness is deteriorated by two independent fracture modes, that is, intergranular fracture and Tempered Martensite Embrittlement (TME). Intergranular fracture is greatly enhanced with the increase in phosphorus content of steel, whereas the boron addition is effective in reducing it and increases toughness over the whole range of tempering temperatures below 400°C. However, phosphorus content and boron addition have no significant effect on TME. Auger Electron Spectroscopic (AES) observation reveals that boron addition reduces the intergranular fracture by reducing the phosphorus segregation at the grain boundaries. The estimation by diffusion calculation and McLean's grain boundary equilibrium segregation model shows that boron segregates to grain boundaries much faster than phosphorus does at austenitizing temperatures and reduces the boundary energy for phosphorus segregation.
A technique for particle size distribution measurement of Al2O3 inclusion in ultra low oxygen steel by combination of ultrasonic classification method and centrifugal sedimentation photo-extinction method has been established. The procedure is as follows. (1) The Al2O3 inclusion extracted from steel by acid decomposition is classified at over and under 5μm with ultrasonic filtration. (2)The Al2O3 inclusion over 5μm is weighed. (3) The particle size distribution of Al2O3 inclusion under 5μm is measured automatically with centrifugal sedimentation photo-extinction method. (4)The particle size distribution of Al2O3 in steel can be obtained by using from (1) to (3). This technique makes it possible to measure particle size distribution of Al2O3 to sub-micron order, and gives instructive information about coalescence and/or floating behavior of Al203 inclusion during refining prosess.
This article reports the results obtained in the second phase of the joint research for ion sputtering, conducted by the Surface Analysis Subcommittee of the Iron and Steel Analysis Committee, the Joint Research Society of ISIJ. Various effects on sputtering yields were studied in detail and the sputtering yields for Ni and Zn were determined by analyzing the results of an in-depth profiling of electrodepsited steels with Auger electron spectrometers. Ar+ ions were used as the bombarding ion species and a Faraday cup, which had a small hole for the ions to pass through in the center of an upper plate over a cup, was used to measure the electric current of incident ions. To calculate the ion current density, a correction for the effective transmittance efficiency of the hole was carried out in consideration of the cross-sectional shape of the hole. The sputtering yields determind in each laboratry by using this correction agree well with each other and show smaller scatter compared with those obtained in the previous phase. The anguler dependence and energy dependence of the sputtering yields for Ni and Zn were also clarified. We, therefor, propose the standard procedure of ion sputtering for in-depth profiling analysis, including methods to measure the ion current, to calculate the ion current density, to optimize the sample position and to tune the lenses of the ion gun.
Analytical methods have been developed for determination and characterization of the compounds containing nitrogen functional groups, found in small quantities in coal tar and pitch, without separation procedures. 1) Identification of chemical forms : The nitrogen functional groups were transformed into N-methyl (or ethyl) derivatives by the reaction with methyl or ethyl iodide, and were detected by 1H-NMR (Nuclear Magnetic Resonance) spectroscopy. The hydrogen chemical shifts of the N-methyl and the N-methylene groups enabled to identify the nitrogen functional groups (amines, pyrroles, and pyridines). 2) Characterization of the pyridine-type compounds : N-methyl quarternary salts of the pyridines, formed by the N-methylation, were detected selectively by FABMS (Fast Atom Bombardment Mass Spectrometry) using glycerine as matrix. The pyridine-type compounds could also be detected as N-protonated pyridinium ions by FABMS using glycerine matrix containing an acid. These methods have been applied to characterize coal tar and pitch. Pyridine-type compounds of one- to four-ring structure were found in coal tar, and those of three- to six-ring structure were found in hexane-soluble fraction of pitch.
The Rf and Rm values of polycyclic aromatic hydrocarbons (PAH) have been measured in reversed phase high performance thin layer chromatography (RPHPTLC) using an octadecyl-bonded silica gel precoated plate and ten different solvents. The Rf and Rm values are correlated with the van der waals volumes (Vv) of PAH and the polarity of solvents. The linear relationships between the Rm values and Vv of PAH were observed. These relationships were well explained by introducing a partition concept with the solubility parameter theory. Same linear relationship was also observed for the Rm values of PAH in coal tar pitch and their molecular weight (MW). The RPHPTLC method is useful for analysing coal tar pitch, because it provides MW and Vv by a simple and rapid procedure.
Gas Chromatograph Mass Spectrometry (GC/MS) is generally used for the analysis of the mixture of aromatic compounds such as a tar and a coal-derived liquid. But GC/MS is not enough to analyze those samples, because many aromatic isomers are contained in those samples. Then the analysis of the mixture of aromatic compounds and the deacidified carbolic oil by means of Gas Chromatograph Fourier Transform Spectrometry ( GC/FT-IR) were reported in this paper. As a result, the advantages of GC/FT-IR were showed on analyzing the mixture of aromatic compounds.
Using field desorption MS, we studied the molecular structures of both pure epoxy resin and epoxy resin with thermal stabilizer, which is used as pre-coated steel. These experiments show that these epoxy resins are bis-phenol A type, which has usually two glycidyl radicals at both end of molecule, but this resin has only one glycidyl radical at the end of molecule, and hydroxyl radical at the other end. Furthermore, it is also shown that this resin shifts to large part of distribution of molecular weight by being baked both at 270 and 285°C, and that glycidyl radical is taken off and re-coupled molecule is formed. These changes occur sharply at 285°C than at 270°C, without thermal stabilizer. However, with thermal stabilizer, there is less change between these temperatures. Therefore, we conclude that thermal stabilizer is effective.