Mixed Compacts Research Articles

含りん鉄系焼結材料の機械的性質

The authors have previously investigated the sintering process and spheroidization of the pores of iron and ferrophosphorus mixed powder compacts. In this paper, the tensile and impact properties of Fe-P and Fe-P-C are investigated, and the correlation between the spherical pore and the properties is discussed.Addition of finer ferrophosphorus powder improves the tensile properties; particularly ductility increases with sintering above eutectic temperature (1050°C) as a result of appearance of small and spherical pores. On the other hand, the ductile-brittle transition curve appears more evidently with the ferrophosphorus additions, and the transition temperature increases with increase of phosphorus content. Though favourable combinations of strength and ductility can be attained with Fe-0.4 wt%P, the limiting concentration of phosphorus is 0.3 wt% in view of practical toughness. Addition of graphite to iron compacts containing low phosphorus content increases the strength, while it causes a drop of both ductility and toughness. However, the addition of graphite to that of high phosphorus content above 0.4 wt% improves somewhat the toughness as a result of grain refinement.

Ｃｕ‐Ｓｉ系混合圧粉体の焼結過程

The sintering process of Cu-Si mixed powder compacts was studied by dilatometric and microscopic examination, E. P. M.A. and X-ray diffraction. The sintering process depended on the particle size of added Si powder. The results obtained for Cu-5wt%Si compacts were summarized as follows:(1) An intermediate η phase (Cu3Si) was produced by solidus diffusion at about 675°C, where an expansion was observed in the Cu-5wt%Si compact with a small particle size Si powder (-250 mesh), and this is due to the pore formation in the vicinity of the interfaces between Si particles and Cu matrix. This rapid diffusion was the first stage leading to homogenization. In consequence, a uniform structure was formed in the Cu-Si compacts with small size Si particles after sintering even at 700°C.(2) The expansion due to Kirkendall effect was not observed in the Cu-5wt%Si compact with large size Si particles (-100+150 mesh). In this specimen, however, an abrupt expansion occurred at 835°C, and it was caused by the penetration of eutectic (Si+η) liquid into interface between Cu particles, leaving pores at the sites where Si particles were located. Afterwards, a homogenization process proceeded in the region filled with eutectic liquid.

チタン圧粉体のちゅう密化に及ぼすＣｏ添加の影響

The sintering characteristics of Ti-Co binary mixed powder compacts containing up to 10 wt%Co were studied by the dilatometric method, and the diffusional process between Ti and Co during sintering was investigated by EPMA.The results obtained are summarized as follows:(1) The addition of Co was quite effective to the densification of titanium powder compacts. For example, the density of Ti-Co binary mixed powder compacts containing only 2 wt%Co sintered at 1573 K for 3.6 ks reached more than 99% of the theoretical value.(2) The contracting phenomenon observed in the high temperature range above 1073 K during sintering of Ti-Co binary mixed powder compacts was confirmed to be related to the network formation of the Co-rich phase along the surfaces of Ti powders.(3) The above mentioned Co-rich phase formed along the surfaces of Ti powders was clarified to be the very fine eutectoid structure composed of α-Ti and Ti2Co.

焼結鋼におけるモリブデンの拡散合金化過程 ＩＩ 鉄‐モリブデン‐炭素混合圧粉体の焼結過程

Alloying processes of molybdenum in sintered steels were studied on the basis of iron-molybdenumcarbon phase diagram. Mixed powder compacts of iron-molybdenum-carbon system containing molybdenum carbide (Mo2C), metallic molybdenum, or ferro-molybdenum powder as a molybdenum additive were sintered in vacuum between 1273K and 1523K for 3.6ks, and the phases formed in these specimens were identified by means of X-ray diffractometory.The results suggest that molybdenum diffuses into iron through a liquid phase produced by (γ-Fe)-Fe3C-Fe2MOC eutectic reaction and/or the M6C carbide formation. In the compacts containing molybdenum carbide powder, the diffusion of molybdenum tended to occur through the liquid phase, whereas in the compacts containing metallic molybdenum and Ferro-molybdenum powders it arose due to the formation of the M6C carbide. The degree of the molybdenum diffusion in iron-molybdenum-carbon compacts changed dependeng on the diffusion path.

鉄‐銅‐炭素および鉄‐銅‐りん‐炭素系焼結合金の焼結時の寸法変化と二，三の機械的性質について

The influence of graphite addition on the dimensional change and the strength was studied in some sintered mixed elemental alloys, i.e. Fe-Cu-C alloys (Cu; 3%, C; 0-0.9%) and Fe-Cu-P-C alloys (Cu; 3%, P; 0.28%, C; 0-0.9%) and then the effect of phosphorus addition on the sintered Fe-Cu-C alloys was discussed. The phosphorus addition was done by using a Cu-8.4%P eutectic alloy powder.The results obtained are as follows;1) In the sintered Fe-Cu-C alloys, the growth of the compacts decreased with increasing graphite content, in contrast, in Fe-Cu-P-C sintered alloys, the dimensional change of the compacts was almost constant with graphite content.2) With the addition of graphite in the Fe-Cu mixed powder compacts, penetration of the liquid copper into the boundaries of the iron powder particles was reduced, so that copper segregation in the alloy structure was noted particularly for the sintered high carbon Fe-Cu-C alloys. This appears to be attributed the decreasing of the wettability of the liquid copper to the solid iron with increasing the graphite content. In comparison, the sintered Fe-Cu-P-C alloys exhibited the great copper segregation in the alloy structure especially at lower carbon level alloys and this may be attributable to the early stabilization of a-Fe phase with phosphorus and smaller copper solubility in the phase. But high addition of graphite enhances the stability of γ-Fe and allows a more rapid diffusion of copper into the γ-Fe, so that the copper homogeneity in the alloy structure was obtained.3) The tensile strength of sintered Fe-Cu-P-C alloys was superior to sintered Fe-Cu-C alloys in the range of 0-0.9% graphite content. Additionally the toughness of the Fe-Cu-P-C alloys was extremely high at graphite addition levels below about 0.4%.

Solid state reaction of mixed powder compacts of succinic anhydride and paranitraniline

The addition reaction between the compacted powders of succinic anhydride and p-nitraniline was studied. Both the reactants, of specific particle size, were mixed in 1:1 molar ratio and compacted. Three compaction pressures, 9.81 × 10 4 N/m 2, 2.82 × 10 7 N/m 2 and 5.64 × 10 7 N/m 2, were used for the study. Conversions were measured at 90, 100 and 110 °C for various reaction times. The mole percentage conversions decreased with the increase in compaction pressure corresponding to a decrease in the initial porosity of the compact. It was also observed that the final porosity of the compact decreased with increase in reaction temperature. The phase boundary controlled model for spheres reacting from inward was found to be suitable for the evaluation of reaction rate constant. The activation energy was calculated to be 20 to 53 kcal/g mol for the temperature range studied.

Ni-C系の擬液相焼結材ならびに溶解・凝固材の球状黒鉛

This paper describes, at first, graphite mophologies in Ni-0.5∼2.0 mass%C mixed powder compacts which are melted at 1723 K and solidified in hydrogen atmosphere. Short holding time at 1723 K provides nodular graphite because many micro-bubbles remain in the molten Ni. On the contrary, long holding time at 1723 K provides only lamellar and eutectic graphite because no bubble exists in the molten Ni.Ni-C compacts were also “semi-liquid-sintered”: the specimens which were pre-sintered at 1553 K for 7.2 ks (2 h) were heated at the rate of 2 Ks−1 up to 1623 K over the eutectic temperature without holding at 1623 K and cooled at the rate of 4 Ks−1. The microstructures consisting of nodular graphite and lamellar one are obtained. The former is solidified in the residual bubbles in the liquid or precipitated in the pores in the solid, and latter takes place in the bubble-free and pore-free portions.

Ｔｉ‐Ｍｏ２元系の焼結ならびに拡散過程

As a result of the diffusion experiment in the temperature range from 1200°C to 1400°C, it was recognized that the interdiffusion coefficients, D determined by Boltzman-Matano method, decreased monotonously with increasing Mo content, while the activation energies for interdiffusion increased monotonously with Mo content. On the other hand, from the intrinsic diffusion coefficients, DTi and DMo determined at 12.8±0.3at%Mo concentration by Darken's relation, it was shown that the diffusion velocity of Ti atoms was about four times as fast as that of Mo atoms, and this difference was confirmed to be one of the most important factors for the expanding phenomenon whose maximum was observed at 50 wt%Mo in the β region during sintering process for the Ti-Mo binary mixed powder compacts. (Received October 22, 1981)

ＴｉＮ基サーメットの研究 ＶＩ ＴｉＮ‐ＴｉＣ‐Ｎｉ系混合圧粉体の焼結特性について

Sintering characteristics of TiN-TiC-Ni mixed powder compacts were studied by heating them in a gas atmosphere of nitrogen, hydrogen and argon, or in vacuum.Shrinkage during sintering was disturbed by an abnormal expansion in a gas atmosphere of argon and hydrogen, or in vacuum, whereas in nitrogen the abnormal expansion was suppressed by the nitrogen pressure. So that the abnormal expansion is thought to be caused by the denitrification which took place during the formation of nitrocarbide, Ti(N, C).Since the solubility in the nickel-solid solution increased with rise of the sintering temperature up to 1340°C, it may be considered that a eutectic between nickel-solid solution and Ti(N, C) occurs at about 1340°C.

Ｔｉ基サーメットの研究 ＶＩＩ Ｔｉ（Ｎ，Ｃ）‐３０ｗｔ％Ｎｉ系及びＴｉＮ?Sｘ?T‐ＴｉＣ?Sｙ?T‐３０ｗｔ％Ｎｉ系混合圧粉体の焼結特性

As a shrinkage of Ti(N, C)-30wt%Ni mixed powder compacts during sintering was remarkably promoted not only in vacuum, but also in argon, hydrogen and nitrogen atmosphere without an abnormal expansion, we concluded that the abnormal expansion during sintering of TiN-TiC-Ni mixed powder compacts1) was caused by denitrification which took place during the formation of Ti(N, C) solid solution.Grain growth of sintered bodies was suppressed with an increase of nitrogen content of the nitrocarbide.In sintering of TiNx-TiCy-30wt%Ni mixed powder compacts, the expansion was arrested; the composition showing the maximum sintered density in the sintering condition at 1500°C for 1 hr. was TiN0.6-15wt%TiC-30wt%Ni.Use of TiCy powders also prevented the occurrence of the abnormal expansion during sintering.

The Phase Relationship and Denitrification during the Sintering Process of TiN–Ni Mixed Powder Compacts

The Phase Relationship and Denitrification during the Sintering Process of TiN–Ni Mixed Powder Compacts

On the Sintering of the TiNx-Ni Binary Mixed Powder Compacts

Sintering characteristics of TiNx-Ni mixed powder compacts were studied by heating them in gas atmospheres of nitrogen, hydrogen or argon, or in vacuum.The shrinkage during sintering was considerably disturbed by the liberated nitrogen gas from the compacts, whereas in lower value for x of TiNx, the gas diffused into TiN, grains up to TiN0.99 without denitrification. So that the shrinkage was remarkably promoted not only in vacuum, but also in hydrogen and argon. While, the nitrogen atmosphere hindered the shrinkage.The Ni concentration and x value in formula TiNx showing the maximum sintered density in the sintering condition at 1500°C for 60min. were approximately 15 wt% and 0.8, respectively.

TiN-Ni系混合圧粉体の焼結過程における相関係と脱窒

TiN-Ni系混合圧粉体の焼結過程における相関係と脱窒

On the Sintering Process of Iron and Aluminum Mixed Powder Compacts

Influence of Al powder addition on the sintering process of Fe powder compact was made by means of dilatometric and microscopic examinations, X-ray diffraction, E.P.M.A. and D.T.A. The results were summarized as follows.(1) An intermediate phase (Fe2Al5) was produced by the interaction of molten Al and solid Fe at the melting point of Al at 660°C, where an expansion and an exothermic phenomenon were observed in the Fe-Al mixed powder compacts.(2) This expansion was due to the penetration of molten Al into the interfaces between Fe particles, leaving pores at the place where the solid Al had been located.In this stage, the cracks were generated at these interfaces in the case of ore reduced Fe-Al mixed powder compacts. It was very difficult to eliminate the large pores and the cracks in more advanced stages of the sintering process. The exothermic phenomenon was thought to be caused by the formation of Fe2Al5.(3) It was proved that for the carbonyl Fe-Al mixed powder compacts of composition over y-loop, the sintering was remarkably accelerated by the process stabilizing the a-Fe phase with the diffusion of Al into the Fe matrix from Fe2Al5 at high temperature.On the other hand, the sintering of ore reduced Fe-Al mixed powder compacts was disturbed by the difficulties to uniformly diffuse Al into larger Fe particles and to repair the cracks.

On the Sintering of the Fe-Ni-C Ternary Mixed Powder Compacts

Using mixed powder compacts of Fe-Ni-1.0 wt%C system with different Ni contents and Fe-4.0wt%Ni-C system with different graphite contents, the influence of Ni addition on the carburization and the dimensional changes were investigated by means of the differential dilatometric method and carbon analysis.The results obtained are summarised as follows:(1) Carbon content combined during heating process up to 900°C, which is about 0.1 wt% in a Fe-1.0 wt%C binary compact, increases with increasing Ni content in Fe-Ni-1.0 wt%C ternary compacts.(2) In the case of the ternary compacts which content carbonyl Ni powder, the sintering rate is remarkably promoted. Also the sintering promotive effect is observed in Fe-carbonyl Ni-1.0 wt%C compacts. These results suggest that the shrinkage due to the sintering of fine powders plays an important role in the promotion of sintering.(3) The combined carbon concentration of the Fe-1.0 wt%C binary sintered compact is nearly the same as that of eutectoid composition. However in Fe-Ni-1.0 wt%C ternary sintered compacts, some hypereutectoid regions are observed, because the carbon concentration lowers with increasing Ni content along the Fe-Ni-C ternary eutectoid line. Therefore the retained shrinkage increase remarkably by the contraction due to the precipitation of primary cementite in the Ni content more than 6 wt%Ni.

On the Some Properties of Sintered Ni Steel

We examined some structural characters of Fe-Ni-C ternary sintered compacts on the basis of the diffusion-experimental results of (Fe-C)-Ni diffusion couple, and also investigated the mechanical properties of Fe-(0-10) wt%Ni-(0-1.0) wt%C ternary sintered compacts.The results obtained are as follows:(1) In Fe-Ni-C ternary mixed powder compacts, sintering is promoted with increasing Ni and grahite contents.(2) An unhomogeneous structure is observed in Fe-Ni-C compacts sintered at 1150°C for 60 min, and this structure may be mainly controlled by the distribution of Ni.(3) The Ni and graphite concentrations showing the maximum strength in the sintering condition at 1150°C for 60 min are approximately 10 wt% and 0.6 wt% respectively, and it is confirmed from the microstructure that a higher content of martensite is observed in the composition and austenite is scarcely observed.

TiN-Ni系混合圧粉体の焼結特性について

Sintering characteristics of TiN-Ni mixed powder compacts were studied by heating them in a gas atmosphere of nitrogen, hydrogen or argon, or in a vacuum.Shrinkage during sintering was disturbed in all of the gas atmospheres, whereas in a vacuum it was promoted remarkably accompanying the occurrence of the liquid phase and denitridation. The solubility of nitrogen in the nickel phase was very small and the composition of the titanium nitride phase equilibrated with the nickel phase was slightly lower than stoichiometric, ie., TiN0.99.The solid solubilities of TiN1−x in the nickel phase at various temperatures were determined by X-ray diffraction, and the maximum solubility of 5.2 wt% was found at 1350°C.

Fe-Ni 2元系混合圧粉体の焼結過程におよぼすNi粉末粒径と不均等拡散の関係

The sintering process of Fe-Ni mixed powder compacts with various particle sizes of the nickel powder and also the mutual diffusion process in the Fe-Ni multilayer specimens with various thicknesses of the nickel layer were analysed by means of the differential dilatometric method and EPMA.The two experimental results were compared and the effect of nickel particle size on the dimensional change of the compacts during sintering was explained by the unequal interdiffusion between iron and nickel.The results are summarized as follows:The compacts containing 10 wt%Ni powder of larger than 63 μm expanded in the sintering at 1150°C for 1 h as long as the maximum nickel concentration at the core of the nickel particle was maintained over 50∼55 wt%. In the compact of a given nickel content, the amount of expansion decreased with increasing nickel particle size due to reduction of the interfacial area for the unequal interdiffusion, and the maximum expansion was observed on the compacts comprising 63–74 micron nickel powders, which have a maximum interfacial area between the iron and nickel phases.

Mechanical Properties of Sintered Copper Steel

To conclude our studies for the sintering in mixed powder compacts of Fe-Cu-C ternary system, the authors investigated the mechanical properties of Fe-(0- 10)%Cu-(0-1.0)%C ternary sintered compacts in relation to the addition of copper and graphite.The results obtained were summarized as follows:(1) The dividing ridge connecting the maximum points of hardness makes a line between the point of 4.0%Cu without graphite which corresponds to Fe-Cu binary eutectoid, and the point of 6.0%Cu with 1.0%C corresponding to Fe-Cu-C ternary eutectoid. The dividing ridge of tensile strength, however, is nearly perpendicular to the axis of copper content and passes the point of 4.0%Cu independent of graphite addition. On the other hand, the elongation becomes lower with increasing copper and graphite contents; the elongation of Fe-Cu-1.0%C ternary sintered compacts containing more than 6.5% Cu is less than 1.0%.In order to produce a good quality of sintered copper steel, the proper compositions of copper and graphite are considered to be 0.51.0%C and 26.0%Cu, respectively.(2) For the specimen of Fe-4.0% Cu-C ternary sintered compacts containing up to 1.0% C, a similar improvement of mechanical properties to the wrought copper steel was made due to the precipitation of e phase which occurs during annealing between 400'-500'C after being waterquenched from 910°C ×15 min.

焼結銅鋼について

The sintering process of Fe-C binary mixed powder compacts and Fe-Cu-C ternary mixed powder compacts was studied mainly from the viewpoint of phase transformation and diffusion.The results obtained were as follows:(1) After the α→γ transformation during heating in vacuum of 10-5mmHg for the Fe-C binary mixed powder compacts, the expansion was observed, the amount of which was nearly in proportion to the amount of additional graphite, and the expansion curve in dilatation and the combined carbon concentration curve well agreed. This means that the carburization was done mainly by the carbon diffusion through the contacting surface of graphite and iron powder rather than through the medium CH4 or CO gas.(2) From the vacuum measurement, it was apparent that the amount of gas discharge from the specimen with the reduced iron powder was by far larger than that from the other specimens. On the contrary, its dilatational expansion was minimum, indicating that the specimen was not swelled by the gas pressure.(3) It was clarified from the thermal analysis that the elimination of the abnormal expansion observed during sintering process of Fe-Cu binary mixed powder compacts was carried out by the liquid phase sintering related to the ternary monotecto-eutectic reaction at 1095°C.(4) The extremely rapid critical cooling rate of 1100°C/sec. was obtained from the Fe-1.0%C binary sintered compacts, while it became 360°C/sec. for the Fe-2.0%Cu-C ternary sintered compacts, and 140°C/sec. for the Fe-6.5%Cu-1.0%C ternary sintered compacts.