A report was previously made by us on the results obtained from our successful operation of the continuous gas carburizing furnace This time, a study was made on the effects of continuous gas carburizing on the toughness and the structure. The results were as follows: The effects on the structural and the mechanical properties were studied by observing the impact value, the hardness, and the structure of Cr-Mo steel, Ni-Cr steel and high carbon steel. The results revealed that (1) the impact value obtained from direct quenching by continuous gas carburizing was somewhat lower as compared with that of pack carburizing, but it coulde be recovered to a considerable degree by using a Ni-Cr steel or a fine grain steel in case Cr-Mo steel is employed, (2) the greatest influence on the ductility was shown by the heating temperature, (3) the ideal temperature for tempering is in the range of 180∼200° by which the ductility of martensite is highly increased, and (4) it is possible to judge the approximate ductility by fractions on the case part.
Determination of oxygen in zirconium metal were studied by the vacuum fusion method and the bromination-carbon reduction method. In the vacuum fusion method, the iron-tin bath technique usually applied for the analysis of gases in titanium metal was used. In this case the molten iron bath in a graphite crucible is the reaction medium. The sample reacts with the molten iron bath containing tin to form a stable carbide of zirconium. At a furnace temp. of 1850°, complete reduction of the oxides is effected within 30 minutes. The evolved gases are extracted and analyzed. In the bromination-carbon reduction method, the sample is mixed with carbon and treated with bromine at 925°, using argon as carrier gas. The oxygen in the sample is converted into carbon monoxide, which is then oxidized to carbon dioxide with hot copper oxide. The carbon dioxide is absorbed into a weighing bulb containing sodium hydroxide.The results with various samples of materials with these methods show a good agreement. In the vacuum fusion method, oxygen in zirconium metal could be determined with accuracy of ±0.01%.
Continued from 1st report,the corrosion rate of lead and lead antimony alloys in several alkaline solutions and the acid resistivity of lead-tin alloys have been studied. (1) Pb and Pb-Sb alloys have corrosion resistance in ammonia water,NaOH solutions, toilet soap aqueous solution and MgCl2-NaCl mixed solution. (2) Pb-Sn alloys showed corrosion resistance in H2SO4 and H2SO4+(NH4)2SO4 solutions, but in nitrous vitriol they were less resistant than Pb and Pb-Sn alloys.
A number of experimental results have been published already about aging of lead alloys. Since the author systematically studied on the lead and lead-antimony alloys with added silicon for explanation of their in aging as cast, as-rolled and as-extruded in room temperature, and some characteristics of aging of these alloys were found to be shown by addition of silicon to lead and lead-antimony alloys. In general, the hardness of lead alloys were increased by addition of silicon both as-cast and as-worked. The experimental results were as follows: (1) Age hardening was observed in as-cast lead-silicon and lead-antimony-silicon alloys, and the more the contents of antimony and silicon were increased, the more effective the age hardening. The increasing rate of hardness on stabilized state was observed remarkably in the range of 0.008∼0.017% silicon on lead-silicon alloys, and in the raage of 0.3∼1.0% antimony in lead alloys containing silicon. (2) Age hardening was observed in as-rolled lead-silicon alloys in the range of 10∼20% draft, and the more the silicon contents were increased, the more the hardening. Age softening was observed on lead-silicon alloys in over 30% drtaft, and no distinct change of hardness was of served in over 30% draft in spite of silicon contents. Age softening was observed in as-rolled lead-antimony silicon alloys, and decreasing rate of hardness was observed remarkably in under 20% draft, and the more the draft, the more the decrease in hardness. Age softening was observed in as 90% extruded lead-silicon and leadsilicon-antimony alloys in spite of antimony and silicon contents.
The T.T.T. curves, the thermal expansion curves and the tempered hardness were measured of sand-cast Ni-Cr white iron with 3%C, 4.5%Ni, and 0∼2.5%Cr. The results obtained can be summarized as follows: (1) With increasing of Cr content, 2 noses appear in the T.T.T. curves, and both the noses, especially the upper nose, move to the prolonged-time side, and the lower nose moves to the lower-temperature side. (2) By annealing at 800°×5 hr, the T.T.T. curves, especially the upper nose, moves to the shorter time-side and the lower nose moves to the higher temperature. As the result, the T.T.T. curves of a relatively low Cr alloy come to have 1 nose. (3) The hardness of the specimen annealed at a given temperature is as follows: (a) By heating at the temperature above Ac1 pt, for example at 700°, the hardness of all alloys becomes HRc 67 (Hs 88), and the higher the temperature, the lower the hardness, (b) The tempered hardness is about HRc 62, if bainite transformation occurs. In the relatively low Cr alloy, the higher the temperature the lower the hardness, but, in the relatively high Cr alloy, it becomes about HRc 67 by “temper hardening”. (4) “Temper hardening” seems to be caused by the precipitation of proeutectoid cementite.
Samples of Cu-0.54%Cr alloys containing silicon and iron up to 0.12% respectively were prepared by vacuum melting and casting. With these samples the author studied the effects of silicon and iron additions upon the softening,the age-hardening and the high temperature strength. Silicon and iron contents slightly raised increased softening temperature and high temperature strength. According to M. G. Corson, the precipitation in Cu-Cr alloys containing silicon was much easier to control than in Cu-Cr alloys, but the author found that the aging rate and the maximum tensile strength decreases and the precipitation became less easier to control with rise in silicon content. Therefore the author thinks that a silicon content of above 0.08% is highly objectionable in Cu-0.54%Cr alloy. On the otherhand, addition of iron had little effect upon the aging of Cu-Cr alloys. The activation energy of precipitation of these alloys were all constant and its value was 65,300 cal/mol.
A simple and rapid procedure for the volumetric determination of zirconium in feno-zirconium alloys has been investigated. Zirconium can be titrated directly with standard cupferron solution using iron (III) as indicator. The titration is carried out in a 25% sulfuric acid solution containing iron (III) and ethyl ether, and after the reaction between zirconium and cupferron is complete, iron (III) is precipitated with cupferron as ferric cupferrate. The end point of titration can be detected by color change of ethyl ether layer with ferric cupferrate in the presence of precipitate of zirconium cupferrate. This simple procedure has only few interferences, and can usually be applied with a minimum preliminary treatment after dissolving the sample in sulfuric acid and ammonium flouride, which are efficient solvents for ferro-zirconium alloys. Flouride interferes in this method but can be removed easily by fuming with sulfuric acid and boric acid.
A combination of high strength,corrosion resistance and simple heat treatment has made Armco 17-4 PH a valuable material for aircraft and other specialized application. This paper deals with the effect of Cu, C and N on phase changes, agin gand mechanical properties and corrosion resistance of 17Cr-4Ni-4Cu cast steel. The results are as follows: (1) Each of the elements Cu, C and N, lowers Ms temperature and increases the amount of retained austenite after solution quenching. C is most potent in this respect, and N is also effective, while Cu is only slightly so. (2) To obtain maximum hardness, the optimum aging is heating 440° for 3 hrs or 480° for 1 hr after solution quenching. This aging proceeds mainly in martensite and is retarded in austenite. The effect of Cu on the hardness is maximum at 4%Cu and N promotes the hardness increase, while C retards the age-hardening. (3) N-containing retained austenite is so stable that by subzero treatment it tends not so much to transform to martensite as C-containing austenite does. −72° subzero treatment is most effective on account of considerable isothermal component for martensite transformation. (4) Cu increases tensile strength, but the elongation becomes the largest by addition of about 2% of Cu, C and N have scarcely any effect on them. (5) Cu improves the anti-sulfuric acid property strikingly. The anti-nitric acid property of the alloy is excellent and Cu, C and N little affect it. The best corrosion resistance is obtained after solution quenching from 1000° 15 min heating followed by 440°-3 hrs aging. This fact suggests that the above aging causes strain hardening rather than precipitation hardening in the steel.
In order to improve the strength of zirconium at elevated temperature, the binary alloys of zirconium with aluminium, tin and molybdenum were melted in non-consumable argon arc furnace and their hot-hardness has been investigated. The results obtained are summerized as follows: (1) About 3% of tin or 4% of molybdenum, at least, has to be added to zirconium in order to improve the strength of zirconium at elevated temperature. On the other hand, addition of 2% of aluminium hardness zirconium more than any of the above elements. Generally, below 400°, molybdenum is the most effective among the three in hardening zirconium, but above 600°, aluminium is the most effective. (2) By quenching from α range, alloys are hardened less than by slow-cooling them from the same temperature. On the contrary, by quenching from β range, they are more hardened. (3) The hot-hardness of alloys which are slow-cooled decreases with increasing temperature, but there is an abnormal hardening range between 300° and 400° in the Zr-Mo alloys when quenched from 900°. A similar phenomenon is also found in the case of tempered Zr-Mo alloys after quenching at the same condition, that is, the hardness rises to the maximum at about 400°. It seems that these phenomena are related with the precipitation of ω in β phase reported by H. A. Robinson et al.
We have determined the magnetostriction constants, λ100 and λ111, of Ni-Cu and face-centered cubic Ni-Co alloys at room temperature, using single-crystal discs and the strain gauge technique. In Ni-Cu alloys, both the constants are negative irrespective of the composition and their absolute values decrease monotonously with increasing copper content. In face-centered cubic Ni-Co alloys,the concentration dependence is quite different for λ100 and λ111; λ111 is negative irrespective of the composition, showing a flat minimum centered at about 30%Co, while λ100 increases almost linearly with increasing cobalt content, passing through zero at about 20%Co, and eventually reaches a large value of 116×10−6 at 55%Co.
The effect of temperature on the anodic passivation of lead is studied by measuring the changes of anodic potential with the lapse of time under the condition of constant anodic current in dilute sodium sulfate solution. The experimental results show that lead dioxide forming the passive film on lead anode is reduced rapidly by local action before the surface is covered completely with the passive film and then the anode potential falls down to the low value which corresponds to active state of lead. As the lead sulfate film which is formed before the formation of passive lead dioxide film is considered to have a considerable effect on the formation of lead dioxide, the state of this film is studied by caluculating the ionic conductivity σ from the potential-time curve, X-ray diffraction and electron microscope. The logσ−1⁄T plot is divided into two linear parts corresponding to different activation energy. Comparing this results with electron microphotograph, we can conclude that the lead sulfate film becomes very porous due to recrystallization at higher temperature range. Due to this porosity of the lead sulfate film, the electrode potential of lead anode cannot reach high potential value at which passivation is accomplished.
The authors determined the oxydation rates of titanium metal and Ti-1∼8%Al alloys by a quartz-spring balance between 907∼1041°, and examined the oxydation products by a microscope. The results obtained are as follows: (1) The oxydation rates of titanium are controlled by reactions on phase boundaries at early periods of oxydation, and are controlled by diffusion rates through scale at thick scale layers. Between the two types of reaction there are interactions. But after 100 minutes the rates of oxydation coincide approximately with the parabolic rate law. (2) In the parabolic rate law reaction the rates are controlled by the diffusion through TiO2 scale layers. In pure titanium the activation energy of this diffusion is about 30000 cal/mol, and this energy for reaction increases with addition of aluminium to titanium. (3) In general, in the alloys containing Al 2∼8% the oxydation rates decrease with increasing aluminium addition, but in the alloy containing Al 1% the rate is more rapid than in pure titanium. (4) Addition of aluminium increases both the activation energy and the lattice defects, and the rapid oxydation of Al 1% alloy may be the result of a small increase of the activation energy and a large increase of lattice defects. (5) The diffusion reaction seems to take place by diffusion of interestitial T ion in TiO2 from the inside to the outside.
Residual strain in cold-rolled and annealed α brass were measured by the etching method and from the breadths at half maximum intensity of X-ray diffracted lines. For cold reduction heavier than 20%, the residual stress decreased with degree of rolling and at 60∼80% reduction approached a certain value about one-half of that 20∼30% reduction. Anneal-hardening phenomenon occurred in a certain stage of recovery in which the difference between the macroscopic residual strain and the microscopic residual strain (lattice strain) becomes large.When specimens were annealed under bending stress,the anneal-hardening phenomenon was promoted. Namely, the temperature of maximum anneal-hardening has been lowered and the degree of anneal-hardening increased with increase of applied load.
The present lecture is intended to give a general idea of the technical and scientific progress made in recent years in the field of aluminium and its alloys. In the first section, the progress in the methods of production of aluminium, namely, the Hall-Hèroult process and the electrolytical refining process, has been reviewed, and the new methods of direct reduction process, the chloride process, the organic compound process and the other refining process are introduced. In the second section, the progress in the ingot making of light alloys has been reviewed and, following a description on the continuous or semi-continuous casting generally used in practice, the newly devised horizontal continuous casting processes of Tessman-Rossi, Gautsch-Ugin and Hunter-Douglas are introduced. The special casting methods of Properzi, Hazelett and the subaquatic casting devised by the present author have also been discussed. In the third section, the progress in the foundry processes of light alloys, including sand casting, die casting, centrifugal casting and precision casting, has been reviewed. In the fourth section, the author speaks on the progress in the methods of rolling, extrusion and forging in general, and touches upon some special rolled products, such as figured plates, shade screens and streckmetall. The Roll-Bond process, the tube-in-strip process, the method of production of sandwich plates and tapered plates have been also described in summary. Besides, the progress in heat-treatment inspection, methods of welding and joining are introduced. In the fifth section, high purity aluminium and the aluminium as an electric conductor have been discussed and new heat-resisting, corrosion-resisting casting alloys are introduced. The sixth section is concerned with the progress in the scientific research on aluminium and its alloys, including studies on their plastic deformation, age-hardening, metallography, method of analysis and utilization of radio-isotopes in the research works.