As a fundamental of continuous rolling of iron powders the effects of various rolling factors, such as the rolling gap dimensions, powder feed rate, rolling speed and kind of powder on the rolling load and the thickness and apparent density of green strip were investigated with Höganäs iron powders. The control of powder feed rate is found to be most favorable to adjust the thickness and apparent density of green strip, compared with other factors. In the case of powders having less flowability the rolling speed must be low and powder feed must be increased to produce the fine strip. The rolling load is an appropriate measure to determine an optimum rolling condition.
First, the sintering and cold rolling conditions were determined with rolled strip from Höganäs iron powders. Second, the effect of various powder rolling factors on the physical and mechanical properties of sintered and cold rolled strips were investigated. The similar tendency in effect of powder rolling factors on the properties of sintered strip was observed. That is, with decrease of roll gap and rolling speed and with increase of powder feed, the apparent density, tensile properties were increased and electrical resistivity was decreased. In the case of cold rolled strips, the effect of powder rolloing factors was observed on the elongation alone. With increase of powder roll load the elongation was increased. The various properties of cold rolled strips produced by powder rolling method are compared favorably with those of conventionally produced strips.
Magnetic properties of specimens with columnar crystals which are cooled in magnetic field applied parallel to those columnar axis and subsequently aged, amount to 13,500 gauss in residual induction Br, 775 Oe in coercive force Hc and 8.5 m.g.o. in maximum energy product (BH)max. In case that the specimens are cooled in magnetic field making an angle of θ(0°≤θ≤90°) with columnar axis and subsequently aged, Br measured parallel to columnar axis tends to fall off less in proportion to 4π Iscosθ. Also in case of specimens with columnar crystals field-cooled in the direction perpendicular to columnar axis and with equiaxial crystals, observations similar to those mensioned above were carried out and dependence of magnetic properties on angle θ are presented. In case that specimens with columnar crystals cooled with no magnetic field and subsequently aged, Br, Hc and (BH)max measured perpendicular to columnar axis of crystals are higher than those measured parallel to columnar axis. In case of specimens with equiaxial crystals cooled in no magnetic field, Br and (BH)max are rather higher, and Hc is lower than those of specimens with columnar crystals cooled in no magnetic field. Magnetic domain patterns were also observed in some typical states. Above-mentioned variation of magnetic properties may be made correspondence to these patterns.
Various compositions of TiC-Ni cermets were extruded at high temperature through graphite dies, by viscous flow of liquid phase. The distributions of transverse rupture strength, hardness, and density along extrusion direction, and the distributions of hardness on the cross sections were investigated. Extrusion-pressure/punch-travel diagrams were recorded, and the flow of the materials and the surface defects were discussed. The most competent composition of TiC-Ni for the present method is about 50%-Ni and balancing TiC. The 50%-Ni rod has uniform property over the whole length except the top of the rod, and the density is good agreement with the theoretical value. The 40%-Ni and lower nickel composite rods have some concentration gradients along extrusion direction, and the surface defects like so-called “fir-tree” were occurred in end-part of the rod.
The polarizing characteristics of synthesized nitrides were investigated by means of a potentiostat in order to examine the electrolytic condition for isolating nitrides from iron and steels. Synthesized nitrides employed in the present investigation were Fe3N,Mn3N2,MO2N,MoN,Cr2N,CrN,VN,Si3N4,AlN,TiN,ZrN and NbN. From the measurements of polarization curve and natural electrode potential of iron and these nitrides, useful informations were obtained on the electrolyte and the anode potential for isolating electrolytically the nitrides included in iron and steels. That is, if a suitable anode potential is applied, both acid and neutral solutions can be used as an electrolyte for the isolation of the nitrides except those of Al,Fe and Mn. While, for the iron nitride, only neutral electrolyte is adequate. As to the nitrides of Al and Mn, however, there seems to be no favorable electrolyte for the isolation within the extent of the experiment.
Transmission electron microscopic studies on precipitation in thin foils of an Al-3.8%wt%Cu alloy have been carried out using a specimen heating attachment and a special 16 mm movie camera. The results obtained are as follows: (1) θ precipitates nucleate at the edge of some θ′ precipitates. θ′ precipitates with θ nucleus gradually grow, but the others having no nucleus gradually disappear. (2) Nucleation of θ phase is never observed in the matrix, except at grain boundaries or the edge of the foil. (3) Newly formed θ precipitates are not perfectly stable; i.e., some of them grow larger but the others shrink to disappear as ageing proceeds. (4) When the foil specimen is very thin, the movement of diffraction contours and their irregularities around precipitates are observed during the change from θ′ to θ phase. They may be due to strain produced by the volume change of precipitates. (5) Rough estimation of diffusion coefficient of copper in aluminium from the measurement of growth rate of θ precipitates gives the value of the same order, but to some degree larger than that obtained from the ordinary diffusion experiment in the bulk materials. (6) Although precipitation in thin foils of supersaturated solid solution at about 300°C appreciably differs from that in the bulk material in some cases, the sequence of precipitation from θ′ to θ phase in thin foils is nearly the same as that occurring in the bulk material.
A fluorescent X-ray analysis by non-dispersion method was applied for the determination of some elements in brass. The absorption filter was principally used to select the characteristic X-ray in the element. The apparatus of this type was simple and small comparing with other dispersion type. In order to determine the element with small probable error, it must be considered that (A) an appliing voltage of X-ray source is about 2∼3 times the voltage of minimum excitation voltage of the element, (B) a profitable material and a suitable thickness is chosen for the filter. The probable error for the determination could be calculated from the ratio of characteristic X-ray to background counting rate and the total number of counts. The characteristic X-ray from the brass, which had a similar composition to the sample but did not contain the element to be analysed, was thought as the background. The probable error obtained by the X-ray analysis agreed well with the error calculated. The X-ray analysis was done by the calibration curve method and each calibration curve showed linear relation between the weight percentage of element in brass and its X-ray intensity, and was influenced little by other elements. The probable error of the experiment were 0.30% for Cu, 0.025% for Fe, 0.08% for Sn and 0.05% for Pb in 60/40 brass with the counting time 30∼100 sec.
In order to obtain guiding principles for development of the roller dies for practical use, researches for drawing of rectangular bar through flat rollers were carried out. The drawing force, the roller separating force and the spread of square wire were measured under various drawing conditions, namely, various roller diameters, wire sizes, reduction in one pass and backward tensions. Calculations of the drawing force, the roller separating force and the roller pressure during drawing of wide strip through flat rollers were done by using the elementary two-dimentional theory of plasticity. Based on above results, guiding principles for development of the practical roller dies are mentioned.
The mechanical properties of 0.2∼0.8%C steel castings treated with the iron-calcium base alloy were compared with those of the untreated castings. 24 kg or 3 kg of these steels were melted in a basic high frequency induction furnace, and different amounts of the iron-calcium base alloy were added to them. All heats tested were deoxidized by the same method as described in a previous report(1). The mechanical properties of the cast steels as-cast or annealed and those of the cast steels as-normalized or annealed after forging were investigated. Results were obtained that the steels treated with the iron-calcium base alloy are characterized by an excellent ductility and a high yield ratio, as a result of cleaner fine grained structures which are caused by the calcium as an effective deoxidizer or degasifier.
Steels containing 0.3 to 0.5%C were melted in alumina-lined graphite crucibles 3 kg in capacity by a high frequency induction furnace. These steels were prepared from electrolytic iron and pig iron. The melt was deoxidized with electrolytic manganese, metallic silicon and different amounts of aluminum ranging from 0 to 0.16%, and cast into metal molds, but a part of the melt was added with the iron-calcium base alloy before casting. After forging, non-metallic inclusions in the steels and the grain coarsening temperature were investigated. The results are summarized as follows: While addition of the iron-calcium base alloy to the molten steel deoxidized only with manganese and silicon is effective in reducing the amount of inclusions belonging to type A and at the same time in increasing the grain coarsening temperature, its addition to the molten steel deoxidized with manganese, silicon and aluminum considerably decreases the amount of oxides, especially, of alumina, and increases the amount of aluminum nitride as compared with the case without addition of the iron-calcium alloy. Addition of this alloy contributes also to the reduce of the grain size which improves the steel property. It is assumed that this reduce of the grain size may be attributed partly to the increase of the amount of aluminum nitride caused by addition of aluminum and the alloy in question. The grain size of aluminum- or calcium-killed steels is rapidly coarsened above a certain temperature, while that of rimmed steels is progressively coarsened with increasing temperature above the transformation range.