The kinetics of the reaction of porous pellets of carbon containing varying amounts of iron, 1 to 15% by weight, with carbon dioxide in the temperature range 850 to 1 000°C is investigated. It is observed that for both the uncatalysed and catalysed pellets the overall rate follows the Langmuir-Hinshelwood equation:
Rate=K₁P_CO2/1+K₂P_CO+K₃P_CO2
where K1, K2, and K3 are the rate parameters. Both the pore diffusion and chemical reaction affect the overall rate. The effect of pore diffusion has been quantitatively estimated using Thiele's concept of “effectiveness factor”. Activation energy for the pore diffusion free intrinsic rate is estimated to be 80.57kcal/g•mol which decreases more or less linearly with increasing iron content. Analysis of the kinetic data indicates that iron addition enhances the rate of desorption of CO from the carbon surface and supports the electron transfer theory of catalysis.

抄録全体を表示

Ridging phenomenon is a surface defect undesirable for deep drawing applications of ferritic stainless steels. Stripe pattern is frequently observed parallel to the rolling direction and appears as narrow banded areas when the strip or sheet of these steels is severely etched. In the present paper, correlation of the ridging and the stripe pattern was discussed, and the origin of the stripe pattern was examined in 18% Cr stainless steel sheet.
It is shown that there is a close resemblance between the stripe pattern and the ridging in terms of the periodicity, the directional characteristics, and the nature of the macro- and microscopic structural compound. The stripe pattern has its origin in the hot rolling stage when partition of Cr and C in α and γ phase proceeds. Debris of γ particles is retained with depletion of Cr in the elongated form in the final product. Local variation of Cr content results in the development of the stripe pattern.

抄録全体を表示

In order to clarify the various phenomena in a blast furnace and its operational problems at the extremely low fuel rate, Nippon Kokan K.K. decided to execute a trial operation in No. 3 blast furnace (inner volume: 3 223m³, blow in; January 1975) at Fukuyama Works.
As a result, a monthly mean fuel rate of 396kg/T was recorded in November 1981. Comparing with the result of the previous test operation in the same furnace (428kg/T, January 1979), heat requirements at the lower part of the furnace could be much reduced.
Both the high reducibility of sinter and adequate burden distribution control enabled to produce and keep the high shaft gas efficiency of 97.5%.
As the heat flux ratio increased, temperature level at the shaft lowered and the three stages of thermal reserve zones were observed. The level of cohesive zone also lowered and its shape changed from “inverse V” to “V” via “W” shape, furthermore some of the measured results indicated that the melting line would be very close to the raceway. In its transitional period, the burden descent became somewhat unstable, but got well again when the fuel rate reduced to around 400kg/T.

抄録全体を表示

Knowledge on the chemical state of phosphorus (P) segregated at grain boundaries in iron is important in discussing the mechanism of grain boundary decohesion by P. In order to determine the chemical state of P at grain boundaries, X-ray photo-electron spectroscopy (XPS) and Auger electron spectroscopy (AES) were used.
Fe-P alloy specimens with the P concentration between 0.05mass% and 15.6mass% was fractured in the analyzer chamber of which vacuum was better than 5×10^-9Pa(4×10^-11torr). Since the amount of P segregated at grain boundaries is small, XPS had to be measured for a long time to accumulate the signal from P. The prolonged measurement was possible without contamination by the residual gas because of the high vacuum. XPS of the segregated P was found to be identical to XPS of P in Fe₃P. This result supports the Losch model for the grain boundary decohesion by P, in which a segregated P atom forms a strong bond with surrounding Fe atoms and reduces the strength of bond between Fe atoms neighboring to the P atom.
The shape of Auger electron spectrum of P in solid solution varies with the P concentration, but that of the segregated P is independent of the P concentration and identical to that of P in Fe₃P. The importance of the variation of the shape of Auger electron spectrum with the P concentration in the quantitative analysis of the segregated P is discussed.

抄録全体を表示

The dephosphorization of molten pig iron containing 18% chromium by the addition of Li₂CO₃ has been studied using a laboratory scale high frequency induction furnace. The degrees of dephosphorization, desulfurization, and denitrification obtained by adding 60-125g/kg-metal of Li₂CO₃ to molten pig iron (0.03% P, 0.03% S, 0.02% N) containing chromium in a graphite crucible were more than 80%. The oxidation loss of chromium was less than 0.5%. The degree of dephosphorization by the addition of Li₂CO₃ was 2.1 times as large as that by the addition of Na₂CO₃ when the same weight of flux was added to the melt. The slag basicity after treatment by Li₂CO₃ was higher than that by Na₂CO₃. The degree of dephosphorization decreased remarkably with increasing temperature. It is preferable to treat the pig iron at a temperature below 1 480°C. The carbon content of pig iron had a remarkable effect on the dephosphorization reaction. When the carbon content was low (3.5%), the oxidation loss of chromium was very large and the degree of dephosphorization was lowered to about 20%. By X-ray diffraction analysis, Li₄SiO₄ and LiCrO₂ were identified in the slag after treatment, and Li₃PO₄ in the phosphorus-enriched slag.

抄録全体を表示

A study has been made of the behavior of gas jet injected into a two-dimensional mercury bath. The vessel was made of acrylate resins. The sheet of mercury was 0.5cm thick. Nitrogen gas (580-3 300cm³/s) was injected into the mercury bath through an orifice of 0.2cm in diameter. The gas jet behavior was observed by using a high speed camera.
It was observed that, when jetting occurs, many tiny droplets are formed in the gas jet at the orifice exit. The present result for bubbling-jetting transition agrees well with the previous data obtained by three-dimensional bath. The injected gas does not form a continuous gas channel even in the sonic velocity region. The injected jet breaks up at some distance from the orifice exit, leaving a gas jet residual. The minimum length of the gas jet residual is fixed for each gas flow velocity. Thus, it has been found that the gas phase forms a small continuous jet extending from the orifice exit to the top of the jet residual.

抄録全体を表示

The present study is concerned with jetting behavior of gas jets injected into water bath. Nitrogen gas (200-10000cm³/s) was injected into the water bath through an orifice of 0.1-0.3cm in diameter located at the bottom. The gas jet behavior was observed directly by using a high speed cinecamera. The frequency of the bubble knocking at the bottom was measured with a microphone.
It is found that the bubbling jetting transition of gas jets injected into water begins to occur when the gas flow velocity at the exit of an orifice exceeds the sonic velocity. This phenomenon is similar to the behavior of gas jets in mercury bath. In the sonic region the frequency of bubble knocking decreases with increasing gas flow velocity. Perfect jetting is found to occur at the highest gas flow velocity explored in the present study. The injection pressure in this case is 30kgf/cm². The initial expansion angle of jet increases with increasing gas flow velocity and agrees well with theoretical calculation. It is presumed that the speed of a gas jet which is equal to the sonic velocity at the exit of the orifice exceeds the sonic velocity just beyond the exit.

抄録全体を表示

The present study has been made to obtain fundamental knowledge on the mechanism of contact of particles with liquid metal during powder injection. A spherical body was dropped onto a stagnant mercury bath and the behavior of the penetration of the sphere was recorded by a high speed cinecamera. The sphere impinging the liquid surface makes a cavity. Then the sphere jumps up from the surface of the cavity when the kinetic energy of the sphere is low. However, the sphere with high kinetic energy dips into the liquid while the cavity disappears; shortly afterward the sphere rises back to the surface with a mercury film. Based on the measurement of the jumping height of the sphere and the time during which the sphere is immersed in the liquid, the critical condition for the particle penetration into the liquid has been determined. Taking into account the inertia of the liquid surrounding the sphere and the cavity formation, one has given a new model describing the penetrating behavior of the sphere into the liquid. The experimental results are well explained by the theoretical calculation.

抄録全体を表示

The effects of austenite deformation conducted below the recrystallization temperature on the subsequent isothermal transformation to pearlite in an eutectoid steel (SKD 6, H11) were quantitatively studied. The plastic deformation in the austenite condition was observed to lead to marked acceleration of austenite→pearlite transformation. This acceleration was found to be mostly caused by the increase in the nucleation rate but not by the increase in the growth rate.
The increase in the nucleation rate per unit volume of specimen was attributed (1) to the increase in the austenite grain surface by the elongation of grains, (2) to the increase in the nucleation rate per se per unit area of grain surface, and (3) to the formation of additional nucleation sites such as annealing twin boundaries, deformation bands, etc. Among these the increase in the nucleation rate per se per unit area of grain surface was found to have the largest effect on the acceleration of transformation by deformation in the steel studied.
The effects of rolling reduction and austenite grain size on the acceleration mechanism of transformation were discussed based on the derived kinetic equation.

抄録全体を表示

Birth and death stochastic processes are confirmed to operate in pitting corrosion of ferritic stainless steels containing Cr, Mo, Ti and Nb. Birth process corresponds to pit generation and death process to pit repassivation, each rate being determined as a function of potential by the analysis of survival probability vs. time curves based on the stochastic theory. Pitting potential is found to shift to the noble value with the addition of all the alloying elements examined. The cause of the shift, however, differs for each element. The shift by alloying Cr, Ti and Nb is caused by a decrease in the pit generation rate, while the pit repassivation rate remains constant. In contrast, the addition of Mo enhances the rate of repassivation and decreases the pit generation rate. These changes of both rates are contributing to the observed shift in pitting potential to the noble value.

抄録全体を表示

The emission intensity of background spectrum occupies a large part of measured intensity, in determining micro amounts of elements in iron and steel by inductively coupled plasma emission spectrometry. Therefore, it is necessary to eliminate the background part in order to obtain the correct intensity of analytical spectrum. Two methods have been proposed to eliminate the background:
(1) The sample is analyzed with calibration solution containing same amounts of matrix elements as in the sample solution.
(2) The intensity of background spectrum is measured with the neighboring line and subtracted from that of analytical line.
The former is valid for the analysis of samples with known chemical composition, the latter is applicable to all unknown samples. The difficulty, however, still remains for it to find the neighboring line with which emission spectra of iron and other elements do not overlap. Both methods have been applied to the determination of trace amounts of cobalt and zinc in a steel. The background has been fully corrected by both methods, and the results obtained are well agreed with those obtained by conventional method of chemical analysis.

抄録全体を表示

Activation analysis of oxygen through bombardment by ³He ion beam was applied to iron and chromium. ¹⁸F produced from ¹⁶O through the reactions of ¹⁶O(³He, p)¹⁸F and ¹⁶O(³He, n)¹⁸Ne (¹⁸Ne→<1.6s>¹⁸F) was separated chemically in the form of PbFCl. The oxygen content was reliably determined in the level of 100ppb. This method can be applied easily to other metals and compounds which can be dissolved in nitric or sulfuric acid.

抄録全体を表示