We had investigated the cold impact backward extrusion of metals such as lead, tin, aluminium, and zinc. The extrusion forces and the force-time curves were oscillographically measured by means of wire strain gauge method. The observed results were minutely compared with the one already obtained in static extrusion. The experimental results were as follows: (1) The shape of the impact extrusion force curves changed depending on the materials, but was almost analogous to the static one. (2) The limit of the extruding reduction was about 95% on zinc but 95% or more on lead, tin and aluminium. (3) The impact extrusion forces might become equal or less than the static one, if both the reduction and the rate of extrusion were increased. (4) The influence of the annealing temperature on the extrusion forces of aluminium was proved so remarkable that for blanks fully annealed the force was reduced to less than half of the values for unannealed samples. (5) In the case of zinc, the extrusion force was only slightly increased by annealing.
A study on cold impact backward extrusion of 65/35 brass was carried out. The influence of various lubricants on extrusion forces, the extrusion force curves, and the corresponding physical properties of extruded shells were in detail examined. The experimental results were summarized as follows: (1) The effect of lubrication was almost similar both in static and impact extrusion. Lubrication with lanolin and zinc phosphate/wax or lanolin systems, etc. were proved suitable for the process. (2) Under these lubricating conditions, a specific force of about 200 kg/mm2 was required for processing 20 mmφ shells with reduction of 53∼64%, and the limit of reduction was about 60% of these shells. (3) The impact extrusion force curves were almost analogous to the one in static extrusion. (4) The hardness distribution and the microstructure of the shells were studied. The extruding texture developed in the wall was in good agreement with the texture obtained by rolling. The residual stresses along the wall surface were determined. (5) In season cracking tests, the impact extruded shells might have too high resistance to form any crack on the wall.
This paper states the results of transformation of the retained austenite to martensite in sub-zero temperature range as affected by quenching temperature and room temperature aging on ball-bearing steel containing 1.02% carbon and 1.35% of chromium. The results obtained are as follows: (1) A higher quenching temperature causes a lower stabilization of retained austenite, that is the higher the quenching temperature, the Ms′ point is the higher. (2) The Mf point of retained austenite is not changed by the quenching temperature and room temperature aging (3) Bmax and Br are increased, but Hc is markedly decreased by sub-zero treatment. (4) The higher the quenching temperature rises, the more the hardness increases by sub-zero treatment, but the final hardness is lower than when the qunching temperature is low. (5) The temperature at which the hardness is increased markedly by sub-zero treatment, is higher than the Ms′ point measured by dilatometric method.
Punching die steel is now most widely used in mechanical and electrical industries, chiefly to punch thin Si-plates, mild steel plates, etc. Many kinds of punching die steel are commonly used today, and their compositions are mainly of high carbon, low Mn-Cr-W and high carbon Cr system. The authors carried out a series of experiments on the effects of C 0.8∼1.3%Mn 0.7∼1.2% and Cr 3.0∼7.0% on the properties of die steels of standard composition, C 1.1 and Cr 5.0%, of which the transformation points were measured and changes in their hardness and microstructures brought out by different heat treatments were studied. We also measured the rate of deformation due to various heat treatment. The results of these experiments are summarized as follows: (1) The A1 and Ar″ transformation point drop with the increase of the C and Mn contents, but Cr shows the inverse results. (2) The quenching temperature necessary for the maximum hardness is lowered with the increase of the C and Mn contents, but Cr shows the inverse results. (3) The rate of deformation due to heat treatment decreases when the C, Mn and Cr contents increase.
In the preceding report, the authors described the effects of carbon, maganese and chromum on 5%Cr punching die steel. In the present investigation the authors studied the effects of W 1.0∼3.0%, Mo 0.5∼2.0% and V 0.25∼0.5% on the properties of die steels of standard composition C 1.1% and Cr 5.0%. The methods of experiment were the same as in the previous investigation. The results of the experiment are summarised as follows: (1) The A1 transformation point is not varied with the increase of W and Mo but the A1 point rises when the V content increases. (2) The quenching temperature necessary for the maximum hardness is lowered with the increase of the Mo content, but V shows the inverse result, while the temperature is not varied with a change in W content. (3) The tempering hardness increases with the increase of W, Mo and V. (4) The rate of deformation due to heat treatment decreases with the increase of the Mo and V contents but W shows the inverse result.
The heat resistance of several electrical heat resisting wires was measured after Al diffusion, and the following results were obtained: By Al diffusion the heat resistance of nichrom and Fe-Cr-Al alloy wire was improved remarkably. Also these Al diffused wires have a considerable heat resistance in H2S gas and can be used up to 700∼800° in this gas.
My study on the sintering process of Cu-Sn bearing alloy is now still going on and this is the first report covering the mechanism of the pore-formation during the sintering process. The results obtained are as follows: (1) Inherent voids are formed in a compact as a result of compacting. (2) During the 1st heat-treatment (at 400° for 60 minutes) over the melting point of tin, tin powders melt away, spreading into the inherent voids, resulting in new pores appearing at the position of the tin powder (hereafter the new pores are called “Tin-off Cavities”). The form of these pores are similar to the and their size is a little larger than those of tin powder. (3) During the heating stage of the 2nd heat-treatment (heated from 400° to 750° and kept at 750°), around the above “tin-off cavities” made at the 1st heat-treatment, other new pores which have a crack-like appearance are produced by melting of Sn-Cu alloy into the inherent voids by the same mechanism as that in the 1st heat-treatment. (4) In this heating stage, at the temperature over the sintering temperature of α, the inherent voids and the cracklike pores grow a little in consequence of partial shrinkage following the densification of α. The pore formation is finished at the beginning of temperature-keeping stage of the 2nd heattreatment and the sintered Cu-Sn alloy is equipped with a lot of pores necessary for complete self-lubrication of the bearing. (5) By keeping the sintered samples at the final temperature for a long time during this 2nd stage, the inherent voids and the pores formed begin to shrink as the result of whole shrinkage of the sintered Cu-Sn alloy.
This is a report on the effects of tin powder upon the pore-control during the sintering process of Cu-Sn bearing alloy. The results obtained are as follows: (1) For getting uniform distribution of the pores, good result are obtained by adding 0.2% light-oil as wetagent in the mixed powders. (2) Controlling the size and the number of the pores is possible by means of using such tin-powder as have various particle sizes.
The thermodynamic activity of Mg in α Ag-Mg alloys has been determined by the electrochemical method at 350° to 550°. The activity exhibits large negative deviation from Raoult’s law, and the existence of Ag3Mg supperlattice is expected from this tendency. By the integration of experimental data concerning α and β phases, the free energy, the entropy of this alloy system have been evaluated. The enthalpy has its marked maximum value of 4.7 kcal/atom at the composition of 1:1, and shows a high stability of the AgMg compound. The range of soild solution formation in α phase is diminished by the stable ordered β phase. This may be attributed to the marked electrochemical differences of these components. The enthalpy and the activity of α phase alloys can not be represented by ordinary statistical formulae.
In spite of the narrow range of α solid solution of this alloy system, the strong chemical binding between the components which was shown in a previous paper, suggests the formation of Ag3Mg supperlattice at a lower temperature. The existence of Ag3Mg supperlattice was confirmed from the measurement of E.M.F., electrical resistance, specific heat and X-ray diffraction. The critical temperature of this alloy is 391°, and its heat of transformation is 360 cal/mol. The structure of this alloy is not like that of Cu3Au type, but is considered to be a layered order structure of large unit cell.
The chemical analysis of alloying elements in carbides and ferrite in special steels were carried out by electrolytic isolation method, and the adaptability of Nernst’s partition law to the distribution of alloying elements between ferrite and carbides in annealed steel was proved experimentally. From the balance of the alloying element in steel (M%), in cementite (〈M〉%) and in ferrite ([M]%), the following partition equations may be deduced: (This article is not displayable. Please see full text pdf.) where Cm represents the percentage of cementite in steel, and the partition coefficient 〈M〉⁄[M] is determined experimentally as follows: Cr; 28, Mn; 10.5, V; 9.0, Mo; 7.5, W; 2.0, Ni; 0.34, Co; 0.23, Si; 0.03. It is evident from the above values that the carbide-forming elements have 〈M〉⁄M>1, that is they concentrate in cementite, particularly in the case of low carbon steel, and on the contrary, the non carbide-forming elements have 〈M〉⁄M<1, or are pooly distributed in cementite, especially in low carbon steel.
In a previous report, the present author observed the growing behaviour of austenite grains, and clarified thereby the relation between the grain growth and the dissolving state of fine aluminium nitride particles into the matrix, and that the fineness of grain size is obtained when aluminium nitride is contained in a more than a certain critical quantity at the soaking temperature. In this report, the author observed the grain growth whithin γ-range of variously heated Al-Killed fine grained steel by using high temperature oxidation coloring method and an emission type electron-microscope, and explained its characteristics and the effect of maintenance temperature, maintenance time, heat treatment and chemical composition upon the incubation period up to coarsening and the progress of coarsening and got the following results:-(1) The more of aluminium nitride is contained in the specimen, the more strongly is impeded the grain growth at higher temperature. (2) This obstruction tendency changes according to the change of heat treatment, and when the aluminium nitride particles are reduced in size and they are equally distributed by means of heat treatment, the obstruction effect is more conspicuous. (3) The influence of heat treatment is the more conspicuous if the specimen contains the more aluminium nitride.
In the previous reports, the authors studied the various characteristics of the behaviour of grain growth of Al-killed steel within γ-range by using high temperature oxidation colouring method and an emission type electron-microscope. In this report a further investigation was made about the resultant characteristics and the following results have been obtained: (1) The inhibitor of grain growth of fine-grained Al-killed steel is the very small particles of aluminum nitride, and the growth of Al-killed steel is very much affected by the size and distribution of the inhibitor particles. (2) To maintain fine grain, it is necessary for the specimen to contain 10∼25×10−4% of aluminum nitride in the terms of N2 quantity at the maintenance temperature, and if this nitrogen is reduced to 1∼5×10−4% by dissolving into the matrix, the steel changes into a uniform coarse grain structre. (3) The above-mentioned necessary quantity of N2 changes more or less according to the variation of soaking temperature and is only slightly affected by the size and distribution of nitride particles. (4) Grain coarsening occurs in the process while the inhibitor particles are dissolved and consumed into the matrix, and arises from the local inequality of the particle size and distribution.