A simplified dynamic model of blast furnace melting zone is developed and two approximate analyses on the dynamic characteristics are presented. From the approximate analysis (I), it has been found that the equation for the accumulation of heat in coke zone can be expressed as the same form as the lumped-parameter system. Applying a local linearization technique to the analysis (I), perturbation analysis (approximate analysis (II)) is developed. From this analysis (II) it has been shown theoretically that the dynamic characteristics of melting zone may be expressed as a combination of two first order lag systems, and that the time constant for the accumulation of heat in the coke zone 71 becomes considerably smaller than the time constant for the shift of melting zone level T.Also the effects of the volume of coke zone and the over-all heat transfer coefficient on the value of these time constants have been discussed in this paper.
In order to determine the effect of immediately injected calcium alloy on the oxygen and sulfur contents of liquid steel, the deoxidation of steel with different calcium complex deoxidizers was studied at 1 600° by means of the high frequency induction melting in a magnesia lined crucible, covering unslaked lime to a depth of 10mm. The results obtained are as follows: (1) Although 2% of SiMn addition which was done at once or dividingly decreased the oxygen content to 0.004%, the desulfurization was not significantly influenced. The addition of calcium complex deoxidizer containing aluminium, after lowering the oxygen content, decreased the sulfur content considerably below that obtained with CaSi, CaSiMn and CaSiBa additions. (2) With a constant oxygen content the amount of sulfur was a minimum in the case of steel deoxidized dividingly with the calcium complex deoxidizer containing aluminium; here the S/O ratio was about from 0.67 to 0.90, while when deoxidizing with CaSi or CaSiMn it was about 2.3. (3) Electron-probe microanalysis of the non-metallic inclusions in ingots, which were produced with the calcium complex deoxidizer containing aluminium, showed various concentrations of CaO (26 to 46%), Al203 (40 to 54%), and CaS (to 34%), possibly due to the presence of complex oxysulfide inclusions. (4) From some difference in the yield of silicon and aluminium in ingots and in the ratio of desulfurization to deoxidation, a favorable calcium complex alloy will have to possess the constituent ratio as Al: Ca: Si: Mn: Fe=1:1:1:1:1.
An attempt has been made to calculate the reacting interfacial area of fire point in basic oxygen steelmaking. An examination of the absorption of NH3 gas from a top blown jet by a liquid bath showed that the absorption efficiency was controlled by the Reynolds and Weber numbers. The influ-ence of We No.appeared to indicate that the surface disturbance created by the jet, waving and splashing, enlarged the gas-liquid contact area. An equivalent interfacial area for the reacting interfacial area was found to correlate with the maximum decarburization rate, in the available furnace data, assuming that the mass transfer rate per unit area of reacting interface was the same in operating furnaces. The equivalent interfacial area A* was given by A*=Ap (We) 0.2, where Ap=calculated surface area of crater by assuming the profile to be parabolic in form, and (We)=Weber No. The equivalent interfacial area and the oxygen flux (=oxygen flow rate/A*) can be regarded as the blowing parameters for single hole and multi hole lance operations.
As the present author reported previously, the surface hardness and toughness of carburized Ni-Cr-Mo steel which was heated rapidly to the optimum austenitizing temperature and quenched afte holding at that temperature for a short time were higher than those of steels which was slowly heated and quenched after holding for a longer time. To invcstigate the reason of the above result, static bending test, rolling-bending fatigue test, investigation of tempering characteristics as well as the metallographic examination in electron microscope were carried out. The results are summarized as follows:(1) The optimum austenitizing conditions for JIS SNCM21 steel carburized to content of 0.73%C are the quenching temperature of 800°, the holding time of 5 minutes, and the minimum heating rate of 30° per minutes.(2) From the results of static bending test and rolling-bending fatigue test, it was found that the beneficial effect of rapid heating and short time holding treatment was very small in steels containing less than 0.50%C.(3) The rapid heating and short time holding result in lower carbon content in martensite, higher Ms temperature and finer austenitic grain size compared with the case of the slow heating and long time holding.(4) Lower carbon martensite with undissolved carbide and fine grain size are attributed to rapid heating and short time holding. From these reasons and analysis of the thermal expansion curves of the specimens of different carbon content, it is clarified that the specimens treated by rapid heating and short time holding can be tempered at lower temperatures than those treated by slow heating and short time holding.
A method for composition analysis of microgram amounts of powder sample has been developed. The sample was ground to the size less than 2 or 3 microns, homogeneously dispersed an organic solvent and filtrated under reducing pressure. In the filtrating procedure Nuclepore Filter of pore size of 0.5 micron was used. Prepared cake was analyzed by powder method of X-ray diffraction. The diffraction pattern from the filter paper did not obstruct the identification of patterns from the examined samples. Then, X-ray microanalysis was applied to the cake which was coated with carbon film. For quantitative analysis the amount of the cake on filter paper had to be over 10 micrograms per square millimeters of the paper. The content of each compound in the sample was estimated by combining the both analytical results. Applicability of this method was checked in the analysis of a foreign substance of small quantity, formed on or contained in steel sheet.