EP0354666A1 - Stahllegierungspulver für Spritzgussverfahren, seine Verbindungen und ein Verfahren zur Herstellung von Sinterteilen daraus - Google Patents

Stahllegierungspulver für Spritzgussverfahren, seine Verbindungen und ein Verfahren zur Herstellung von Sinterteilen daraus Download PDF

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EP0354666A1
EP0354666A1 EP89307117A EP89307117A EP0354666A1 EP 0354666 A1 EP0354666 A1 EP 0354666A1 EP 89307117 A EP89307117 A EP 89307117A EP 89307117 A EP89307117 A EP 89307117A EP 0354666 A1 EP0354666 A1 EP 0354666A1
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Prior art keywords
weight
injection molding
sintered
powder
stainless steel
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EP89307117A
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English (en)
French (fr)
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EP0354666B1 (de
Inventor
Minoru Nitta
Yoshisato Kiyota
Yukio Makiishi
Hiroshi Ohtsubo
Toshio Watanabe
Yasuhiro Habu
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JFE Steel Corp
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Kawasaki Steel Corp
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Priority claimed from JP63172532A external-priority patent/JPH0225501A/ja
Priority claimed from JP63206719A external-priority patent/JPH0257606A/ja
Priority claimed from JP63206720A external-priority patent/JPH0715121B2/ja
Application filed by Kawasaki Steel Corp filed Critical Kawasaki Steel Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
    • B22F3/225—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by injection molding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
    • C22C33/0285—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5% with Cr, Co, or Ni having a minimum content higher than 5%
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2201/00—Treatment under specific atmosphere
    • B22F2201/05—Water or water vapour
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

  • the present invention relates to metal powders for injection molding use, their compounds and the method for producing sintered parts from the same.
  • Sintered steel which is a kind of sintered metal bodies, is partially replacing ingot stainless steel, since the former offers advantages over the latter with respect to improvement of the yield and reduction of machining cost.
  • the raw material powder for injection molding of a 20 microns or less average particle diameter that it is in the spherical shape and in the form of fine particles.
  • An advantage of the spherical powder is that it imparts good slip among the particles, that is to say, it has excellent injection moldability.
  • the former offers a lower viscosity and demonstrates better injection moldability.
  • an equivalent level of injection moldability can be achieved with a less quantity of the binder. For the said reasons, it becomes possible to shorten the debinding cycle, and also to achieve a high density by dint of a finer particle size of the powder.
  • Iron-Cobalt-type alloy is known as a soft magnetic material having the highest saturated magnetic flux density among all magnetic materials.
  • Iron-Cobalt-­type alloy can be said to exhibit a higher magnetic energy with a given volume among all magnetic materials.
  • Powder metallurgy is considered to be a valid means by which to overcome such inferior workability, and variety of methods have been proposed.
  • Japanese Patent Laid Open No. 291934/86 the Japanese Patent Laid Open No. 54041/87, and the Japanese Patent Laid Open No. 142750/87 concerning Iron-Cobalt-type sintered materials
  • Japanese Patent Publication No. 38663/82 The Japanese Patent Laid Open No. 85649/80
  • Iron-Cobalt-type sintered materials containing phosphorus and the Japanese Patent Laid Open No. 85650/80 concerning Iron-Cobalt-type sintered materials containing boron.
  • Japanese Patent Laid Open No. 75410/79 concerning Iron-­Cobalt-Vanadium-type sintered materials.
  • mixed powder namely, a powder prepared by admixing iron-cobalt alloy powder, cobalt-vanadium alloy powder, iron-phosphorus alloy powder, and/or iron-boron alloy powder with iron powder and cobalt powder, so that the raw material powder will enable molding in a mold for the compression molding press, while the admixing or blending ratio had to be limited to an extent that does not deteriorate the compressibility.
  • the method proposed in the Japanese Patent Laid Open No. 291934/86 is intended for improvement in the compressibility by utilizing rapidly quenched iron-cobalt alloy, in which no regular lattice structure is formed, as well sinterability by dint of the blend of such rapidly quenched iron-cobalt alloy powder with cobalt powder
  • the method proposed by the Japanese Patent Laid Open No. 54041/87 is for improvement in the sintered density by HIP (hot isostatic press) Method
  • the method proposed by the Japanese Patent Laid Open No. 142750/87 aims at improvement in the magnetic characteristics by means of improved green density (compressed powder density) and sintered density by combination of coarse Iron-Cobalt-type alloy powder with cobalt fines.
  • the Japanese Patent Publication No. 38663/82 (The Japanese Patent Laid Open No. 85649/80) and the Japanese patent Laid Open No. 85650/80, both of which are intended for improving magnetic characteristics by means of achieving high sintered density that unblended powders.
  • the former method comprises sintering a pulverized iron-phosphorus alloy (26.5% by weight of P) so that the phosphorus content will be 0.05 to 0.7%.
  • the latter method comprises sintering of pulverized iron-boron alloy (19.9% by weight of B) so that the boron content will be 0.1 to 0.4%.
  • the sintered material disclosed in the Japanese Patent Laid Open No. 75410/79 is intended to improve magnetic characteristics by increasing the sintered density of Iron-Cobalt-Vanadium-type alloy as sintering material through liquid phase sintering of a composition prepared by blending pulverized vanadium-cobalt alloy ground powder consisting of 35 to 45% by weight of vanadium, comprising 38% vanadium eutectic composition, with iron powder and cobalt powder.
  • the conventional methods as proposed hereinabove are, however, .intended for compression molding using a mold, and are not applicable to injection molding, since the raw material powder is essentially a mixture of various single-element metal coarse powders having inferior sintering characteristics and two-element alloy powders, and said powders differ from one another in the particle size and the particle shape due to difference in the manufacturing methods employed.
  • Iron-Cobalt-type sintered material is replacing a part of the ingot iron-cobalt alloy material on account of the former's advantage with respect to the yield and the machining cost.
  • expectation is entertained of future development of the injection molding method which is capable of readily giving three dimensional profile parts, substituting the compression molding method which is merely capable of producing two dimensional parts.
  • the raw material powder intended for injection molding are required to be fines in the spherical particle shape, and has oxides on the surface of the particle which can be reduced, in the case of Iron-Cobalt-type sintered material as was described in relation to the Stainless Steel-type sintered material.
  • the present inventors by way of carrying out elaborate experiments relating to the manufacture of stainless steel powder as a raw material for sintered steel and the manufacture of sintered steel by injection molding, have engaged in search for such chemical compositions that will not at all impair the corrosion resistance of the sintered body and also will give the spherical particle shape as powder which is suitable for injection molding. The present inventors thereby have completed the present invention.
  • the object of the present invention is to provide a stainless steel powder of the spherical particle shape having excellent injection moldability in the manufacture of sintered stainless steel parts which depend on injection molding, and a method for producing sintered stainless steel having excellent corrosion resistance, utilizing the said raw material powder.
  • Another object of the present invention is to provide a stainless steel fine powder which is in the spherical particle shape, namely, a suitable particle shape to achieve good injection moldability for metal powders, and comprised reducible oxides on the surface of the particle, thus imparting excellent sintering characteristics.
  • Another object of the present invention is to provide sintered stainless steel material having excellent corrosion resistance by means of injection molding, sintering and, depending on the need, by making HIP (hot isostatic press) treatment of the said stainless steel powder.
  • Still another object of the present invention is to provide Iron-Cobalt-type alloy fine powder and Iron-Cobalt-­type fine powder having the spherical particle shape which imparts suitable injection moldability for metal powder and having excellent sintering characteristics by virtue of the reducible oxides on the surface of the particle, and, furthermore, to provide a sintered iron-cobalt material having useful magnetic characteristics, in particular, high saturation magnetic flux density by injection molding the said alloy fines, sintering the injection molded part thereby obtained, and depending on the need, making HIP treatment of the sintered part.
  • sintered stainless steel parts for which the injection molding method is utilized, different from the melt process to obtain molded stainless steel parts, sintered parts having high density can be obtained by increasing the carbon content of stainless steel fine powder, rather than decreasing the same, and employing a certain sintering method.
  • the "average particle diameter” means a particle diameter of the particle size group (powder fraction) with whose addition the cumulative volume measured from the finer particle group reaches the 50% level of the total volume) which have particle shapes suitable for injection molding and such surface construction (the surface comprising a certain oxide composition) as gives excellent sintering characteristics are producible by atomizing the melt consisting of a chromium-containing stainless steel having the composition of 0.20% or more by weight of silicon and a Manganese/Silicon ratio of 1.00 or higher, and a Chromium-type stainless steel having the composition of 1.20% or less by weight of carbon, 0.20% or less by weight of silicon, a Manganese/Silicon ratio of 1.00 or higher, and 8.0 to 30.0% by weight of chromium, or Chromium-Nickel-type stainless steel having the composition of 8.0 to 30.0% by weight of chromium and 8.0 to 22.0%
  • an improvement is achieved in the corrosion resistance of the sintered stainless steel material at carbon content levels of 0.05% or lower by weight by means of alloying with Chromium-type stainless steel or Chromium-­Nickel-type stainless steel one or more of 1.0 to 4.0% by weight of nickel, 0.3 to 4.0% by weight of molybdenum, and 0.5 to 5.0% by weight of copper.
  • an improvement is achieved in the cutting efficiency of the sintered stainless steel at carbon content levels of 0.05% or lower by weight by means of alloying with Chromium-type stainless steel or Chromium-Nickel-type stainless steel with one or more of 0.05 to 2.00% by weight of tin, 0.02 to 0.05% by weight of sulfur, 0.05 to 0.20% by weight of selenium, and 0.05 to 0.20% by weight of tellurium.
  • iron-cobalt fine powder of an average particle diameter of 20 microns or less having a particle shape suitable for injection molding and comprising the surface (the surface containing a certain oxide composition) which imparts excellent sintering characteristics by means of producing metal fines by the atomizing method from an iron-cobalt melt, the composition of which being 2.00% or less by weight of manganese, and 15 to 60% by weight of cobalt, the balance being substantially iron except impurities. Accordingly, it is possible to obtain by sintering the above-mentioned alloy fine powder sintered material containing closed pores and superior in magnetic characteristics which has a relative density ratio (the ratio to true density) of 92% or higher and has a carbon content of 0.02% or less by weight.
  • Iron-Cobalt-type or Iron-Cobalt-Vanadium-type powder of an average particle diameter of 20 microns or less having a particle shape suitable for injection molding and comprising the surface of the particle (the surface containing a certain oxide composition) which imparts excellent sintering characteristics by means of producing metal fines by the atomizing method from Iron-Cobalt-type or Iron-Cobalt-Vanadium-type melt, the composition of which being 1.00% or less by weight of carbon, 1.00% or less by weight of silicon, 2.00% or less by weight of manganese, and 1.00 or higher Manganese/Silicon ratio.
  • an improvement can be achieved in the apparent density and the tap density of the allow powder of an average particle diameter of 20 microns or less and in magnetic characteristics at carbon content levels of 0.02% or lower by weight in accordance with increase in the sintered density by means of alloying with the above-mentioned melt one or both of 0.02 to 1.00% by weight of boron, 0.05 to 1.00% by weight of phosphorus and atomizing the alloy into fine powder.
  • composition of the stainless steel powder offered to uses in the manufacture of sintered stainless steel by injection molding is in the present invention based on a carbon content of 0.1 to 1.0% by weight, the other elements as constituents being the same as those of the known stainless steel.
  • raw material powders which are offered to the manufacture of sintered stainless steel by compression molding are required to have carbon content reduced to an extent lower than that of ingot steel, from the view point of ensuring corrosion resistance as well as compressibility in compression molding.
  • the carbon resulting from raw material powder as well as the carbon resulting from the organic binder can be removed by performing sintering in a reduced pressure atmosphere.
  • the chemical composition of the steel powder of this invention offers not only excellent powder properties, but also good economics in the manufacture, since the declines of viscosity and melting point of the molten meal by addition of carbon makes it possible to lower the molten metal treating temperature and to shorten the atomizing cycle.
  • composition of the stainless steel powder of the present invention can be generally applicable to compositions of Chromium-containing stainless steel, including Austeinite-­type or Ferrite-type stainless steel like, for example, SUS316, SUS304 and SUS410 of JIS, and can be used with carbon added to the composition of the known sheet form material or conventional powders for powder metallurgy.
  • the above-­mentioned effect is attributed to the fact that physical properties of the molten metal such as the viscosity can be uniformly altered by adding carbon to the molten metal having the composition of stainless steel, and achieve uniform spherical particle formation in the atomized powder, since the form of particles in the powder manufactured by the atomizing process is strongly influenced by physical properties of the molten metal such as the viscosity.
  • the particle size of the powder in terms of the average particle diameter for injection molding is 20 microns or less, and it is preferable that powders having an average particle diameter of 10 microns or less is used for the purpose of achieving high levels of density for the finally obtained sintered parts.
  • the above-mentioned stainless steel powder is added with an organic binder to prepare a compound for injection molding.
  • composition of silicon-containing alloy powder offered to uses in the manufacture of sintered silicon-­containing allow material by injection molding is preferably based on 1.20% or less by weight of carbon, 0.20% or more by weight silicon, 1.00 or higher Manganese/Silicon ratio, and 20 microns or less average particle diameter.
  • it is 1.2% or less by weight of carbon, 0.20% or more by weight of silicon, 1.00 or higher Manganese/Silicon ratio, and 8.0 to 3.00% by weight of chromium, the balance being substantially iron except impurities, with an average particle diameter of 20 microns or less.
  • raw material powders which are offered to the manufacture of sintered stainless steel by compression molding are required to have its carbon content reduced to an extent lower than that of ingot steel, from the view point of ensuring corrosion resistance as well as compressibility in the compression molding.
  • the carbon resulting from raw material powder as well as the carbon resulting from the organic binder can be removed by performing sintering in vacuum.
  • the atomized particle is shaped into the spherical shape by dint of the decline in the oxygen content of the melt which is caused by the carbon's getting alloyed with constituents of stainless steel in the melt form and also the decline in the viscosity and melting point of the melt.
  • stainless steel fine powder obtained by atomizing the melt with circular water jet injected at a 1,000 Kgf/cm2 water pressure having an average particle diameter of 8.0 to 9.0 microns as shown in Table 1 through Table 3 its apparent density and tap density are recognized to increase in accordance with the increase in the amount of carbon alloy, hence the spherical particle formation is known to have taken place in the powder.
  • the viscosity temperature of the compound increases remarkably, if the alloyed carbon content of the stainless steel powder exceeds the level of 1.20% by weight, since the limit of deoxidation owing to the carbon-wit-oxygen reaction is lowered to below the limit of deoxidation corresponding to amounts of silicon and manganese alloyed in the melt in consequence of the decline in the melt temperature at the time of introduction of the melt for the atomizing stage, thus causing the apparent density and the tap density to drop on the contrary due to production of bubble-like particles in which carbon monoxide gas is encapsulated.
  • the alloyed carbon content of the stainless steel powder is limited to 1.20% or less by weight, since in case the said compound undergoes vacuum sintering and maximum sintering time which are ordinarily adopted industrially, namely, at 1,350°C and for 4 hours, the carbon content of the sintered material cannot be reduced to 0.05% or less by weight, and, consequently, the corrosion resistance is deteriorated.
  • the melt alloyed with chromium causes clogging of the tundish nozzle with chromium oxide (Cr2O3) which precipitates on the tundish nozzle due to drop of the melt temperature, with addition of C, Si and Mn to the melt, it is possible to adjust the oxygen content of the melt to below the Cr-O deoxidation limit, which reaches the equilibrium at the melt temperature when melt passes through the tundish nozzle, and thus the nozzle clogging can be prevented.
  • Cr2O3 chromium oxide
  • the oxygen contents of Cr-O and Si-O in the melt reach approximity of the equilibrium at 0.20% by weight of Si content and the melt passes through the tundish nozzle without clogging it, thus making atomization possible.
  • the silicon content is limited to 0.20% or more by weight.
  • the spherical particle formation is known to have occurred at a Manganese/Silicon ratio of 1.00 or higher in the case of the alloy powder obtained by atomizing the melt with water jet as shown in Table 1 through Table 3, since both apparent and tap densities increase and the viscosity temperature of the compound is lowered. Moreover, it is also learned that the sintered density increases and the surface has been made into a condition which imparts fair sinterability when the Manganese/Silicon ratio is 1.00 or higher.
  • the MnO is considered to be reduced into carbon monoxide by the carbon content of the compound or the alloyed carbon content of the melt, thus not obstructing sintering, so long as the said compound undergoes vacuum sintering at about 1,350°C, which is the sintering temperature generally adopted industrially.
  • silicon produces viscous silicon dioxide (SiO2) on the surface of the particle in the atomizing stage to make the particle shape irregular, and the silicon dioxide can hardly undergoes reduction into carbon monoxide with carbon in vacuum at a temperature of about 1,400°C, hence sintering is obstructed. Therefore, the Manganese/Silicon ratio of the melt is limited to 1.00 or higher for the purpose of achieving spherical particle formation and a surface of the particle which imparts a fair sinterability in the atomizing stage.
  • Chromium is a basic alloy element of stainless steel, which forms the passive state film and imparts corrosion resistance.
  • the chromium content is limited to 8.0 to 30.0% by weight, since addition of chromium in an amount exceeding 30% by weight does not bring about any improvement in the corrosion resistance, while the corrosion velocity remarkably decreases at the chromium content level of 8.0% or higher by weight, in the case of sintering a material constructed with closed pores having a specific density ratio of 95% which iis obtained by injection molding Chromium-containing powder of an average particle diameter of 8.0 ti 9.0 microns (5.0 to 33.0% by weight of chromium, 0.02% by weight of carbon, 0.70% by weight of silicon, 1.00% by weight of manganese, 0.02% by weight of phosphorus, and 0.01% by weight of sulfur, the balance being substantially iron) and vacuum sintering the said injection molded material in vacuum at 1,350°C for 4 hours at 10 ⁇ 4 torr, according to the corrosion resistance test carried out on samples immer
  • the reason for limiting the nickel content of Ferrite-­type sintered steel to 1.0 to 4.0% by weight are set forth below.
  • the process of achieving the passive state in Chromium-containing sintered ferrite steel is enhanced by nickel, and the corrosion resistance is thereby improved.
  • the nickel content for improving corrosion resistance of sintered Ferrite-type stainless steel of the present invention is limited to 1.0 to 4.0% by weight, since addition of nickel in an amount exceeding 4.0% by weight does not bring about any improvement in the corrosion resistance, while the corrosion velocity remarkably decreases at the nickel content level of 1.0% by weight or higher, in the case of sintering material constructed with closed pores having the relative density ratio of 95% which is obtained by injection molding stainless steel fine powder of an average particle diameter of 8.0 to 9.0 microns (whose composition being 18% by weight of chromium, 0.02% by weight of carbon, 0.70% by weight of silicon, 1.00% by weight of manganese, 0.02% by weight of phosphorus, and 0.01% by weight of sulfur, the balance being substantially iron) and vacuum sintering the said injection molded material in vacuum at 1,350°C for 4 hours at 10 ⁇ 4 torr, according to the corrosion resistance test carried out on samples immersed in a 1% sulfuric solution maintained at 25°C as shown in Fig. 5, which represents results of elaborate studies made
  • Nickel is a basic alloy element of Austenite-type stainless steel, which expands the gamma-phase area, thus stabilizing Austenite.
  • Nickel is electrochemically noble, compared with iron and chromium, imparts corrosion resistance against chlorides or nonoxidative acids, and intensified the tendency of the passive state of oxides of chromium.
  • the nickel content is limited to 8.0 to 22.0% by weight, since the sintered steel containing 8.0% by weight of chromium of the present invention is made into Austenite to have sufficient corrosion resistance against chlorides or nonoxidative acids with the nickel content of 8.0% by weight and for a 30.0% by weight chromium-containing steel, the required nickel content is 22.0% by weight and addition of nickel in an amount exceeding 22.0% by weight does not bring about any improvement in the corrosion resistance of Austenite-type sintered stainless steel of the present invention.
  • Molybdenum and copper stabilize the passive state of Ferrite-type sintered stainless steel and Austenite-type sintered stainless steel and improve their corrosion resistance.
  • the molybdenum content and the copper content are limited to 0.3 to 4.0% by weight and 0.5 to 5.0% by weight, respectively, since addition of molybdenum in an amount exceeding 4.0% by weight or addition of copper in an amount exceeding 5.0% by weight does not bring about any improvement in the corrosion resistance, while the corrosion velocity decreases at the molybdenum content of 0.3% or more by weight or the copper content of 0.5% or more by weight either singularly or in combination, in the case of sintering a material constructed with close pores and having a relative density ratio of 95% which is obtained by injection molding Austenite-type stainless steel fine powder of an average particle diameter of 8.0 to 9.0 microns (18% by weight of chromium, 14% by weight of nickel, 2.5% by weight of molybdenum, 0.70% by weight of silicon, 1.00% by weight of manganese, 0.02% by weight of phosphorus, and 0.01% by weight of sulfur, the balance being substantially iron) and vacuum sintering the said injection molded material in vacuum at 1,350°
  • Tin, sulfur, selenium, and tellurium improve the cutting efficiency of Ferrite-type sintered steel or Austenite-type sintered steel, when one or more of them are added to it.
  • the tin content, the sulfur content, the selenium content and tellurium content are limited to 0.05 to 2.00% by weight, 0.02 to 0.50% by weight, 0.05 to 0.20% by weight, and 0.05 to 0.20% by weight, respectively, since addition of tin in an amount exceeding 2.00% by weight, addition of sulfur in an amount exceeding 0.50% by weight, addition of selenium in an amount exceeding 0.20% by weight or addition of tellurium in an amount exceeding 0.20% by weight does not bring about any improvement in the cutting efficiency, while the cutting load (torque) decreases at the tin content of 0.05% or more by weight, the sulfur content of 0.02% or more by weight, the selenium content of 0.05% or more by weight, or the tellurium content of 0.05% or more by weight either singularly or in any combination, in the case of sintering a material constructed with closed pores having a relative density ratio of 95% which is obtained by injection molding Ferrite-type stainless steel powder (comprising 0.70% by weight of silicon,
  • the average particle diameter is limited to 20 microns or less, since if the average particle diameter exceeds 20 microns, it becomes impossible to manufacture the sintered material constructed with closed pores which has a relative sintered density ratio of 92% or higher as shown in Fig. 3 and the relative sintered density ratio falls short of 92%, thus causing remarkable deterioration of the corrosion resistance as shown in Fig. 5 and Fig. 6.
  • Iron-Cobalt alloy powder utilized in the manufacture of sintered iron-cobalt alloy material by injection molding of the present invention comprises 2.0% or less by weight of manganese and 15 to 60% by weight of cobalt, the balance being substantially iron except impurities and has an average particle diameter of 20 microns or less.
  • composition may include either one of 0.02 to 1.00% by weight of boron and 0.05 to 1.00% by weight of phosphorus.
  • the composition may be 1.0% or less by weight of carbon, 1.0% or less by weight of silicon, 2.0% or less by weight of manganese, 1.0 or higher Manganese/Silicon ratio, and 15 to 60% by weight of cobalt, the balance being substantially iron except impurities, and has an average particle diameter of 20 microns or less.
  • the reasons for limiting the manganese content to 2.00% or less by weight are set forth below.
  • the manganese content is limited to 2.00% or less by weight, since the saturated magnetic flux density of the sintered material declines to a level lower than that of Fe-single constituent sintered material at a manganese content level higher than 2.00% by weight, although Iron-Cobalt-type melt or Iron-Cobalt-­Vanadium-type melt with an increased manganese content produces low melting point MnO-FeO on the surface of the particle at the atomizing stage, which lowers the melting point in the surface layer of the particle before it solidifies and enhances the spherical particle formation of the atomized particle as a result of increase in the surface tension and drop in the viscosity.
  • raw material powders which are offered to the manufacture of Iron-Cobalt or Iron-Cobalt-Vanadium sintered material by compression molding are required to have its carbon content reduced to an extent lower than that of ingot steel, from the view point of ensuring compressibility in the compression molding as well as of magnetic characteristics.
  • the atomized particle is shaped into the spherical shape by dint of the decline in the oxygen content of the melt which is caused by the carbon's getting alloyed with constituents of stainless steel in the melt form and also the decline in the viscosity and melting point of the melt.
  • stainless steel powder obtained by atomizing the melt with circular water jet injected at a 1,000 Kgf/cm2 water pressure having an average particle diameter of 9.0 to 10.0 microns as shown in Table 8 its apparent density and tap density are recognized to increase in accordance with the increase in the alloyed carbon content, hence the spherical particle formation has taken place in the powder.
  • the viscosity temperature of the compound increases remarkably, if the alloyed carbon content of 50% iron-containing cobalt powder exceeds the level of 1.00% by weight, since the limit of deoxidation owing to the carbon-­with-oxygen reaction is lowered to below the limit of deoxidation corresponding to amounts of silicon and manganese alloyed in the melt whose amounts are limited in the melt, thus causing the apparent density and tap density to drop on the contrary, due to production of bubble-like particles in which carbon monoxide gas is encapsulated.
  • the alloyed carbon content of Iron-Cobalt-type alloy powder or Iron-Cobalt-Vanadium-type alloy powder is limited to 1.00% or less by weight, since in case the said compound undergoes vacuum sintering and the maximum sintering time which are ordinarily adopted industrially, namely, for 4 hours, the carbon content of the sintered material cannot be reduced to 0.02% or less by weight, and, consequently, the magnetic characteristics are deteriorated.
  • the reasons for limiting the silicon content, the manganese content, the Manganese/Silicon ratio to 1.0% or less by weight, 2.00% or less by weight, and 1.00 or higher, respectively, are set forth below.
  • the silicon content and the manganese are limited to 1.00% or less by weight and 2.00% or less by weight, respectively, which correspond to the limits within which the saturated magnetic flux density of Iron-Cobalt-type or Iron-Cobalt-Vanadium-type sintered material is higher than that of sintered single constituent-­iron material.
  • the Manganese/Silicon ratio is 1.00 or higher, it is recognized that the singered density has increased and the surface condition of the particle has become fair. Therefore, the Manganese/Silicon ratio is limited to 1.00 or higher.
  • the MnO is considered to be reduced into carbon monoxide by the carbon content of the compound or the alloyed carbon content of the melt, thus not obstructing sintering, so long as the said compound undergoes vacuum sintering at about 1,400°C.
  • silicon produces viscous silicon dioxide (SiO2) on the surface of the particle in the atomizing stage to make the particle shape irregular, and the silicon dioxide can hardly undergoes reduction into carbon monoxide with carbon in vacuum at a temperature of about 1,400°C, hence sintering is obstructed. Therefore, the Manganese/Silicon ratio is limited to 1.00 or higher for the purpose of achieving spherical particle formation and a surface of the particle which imparts a fair sinterability in the atomizing stage.
  • cobalt imparts an effect of increasing the saturated magnetic flux density (B s ) by means of replacing iron.
  • B s saturated magnetic flux density
  • the cobalt content is limited to 15 to 60% by weight, since the said effect is meager if the cobalt content is less than 15% by weight or in excess of 60% by weight.
  • Iron-Cobalt-type alloy powder consists of the above-mentioned specified composition
  • the effect can be further enhanced by means of adding the following constituents.
  • vanadium imparts an effect of increasing the specific resistance of the sintered material.
  • the vanadium content is limited to 1.0 to 4.0% by weight, since the said effect is small if the vanadium content is less than 1.0% by weight and the coercive force (H c ) sharply increases, deteriorating the soft magnetism of the material if the vanadium content exceed 4.0% by weight.
  • the melt alloyed with vanadium causes clogging of the tundish nozzle with vanadium oxide (V2O3) which precipitates on the tundish nozzle due to drop of the melt temperature
  • V2O3 vanadium oxide
  • More excellent Iron-Cobalt-type alloy powder can be obtained by adding the following constituents.
  • boron and phosphorus impart an effect of producing atomized particles having the spherical particle shape when they are added to the melt to get alloyed with constituents therein either singularly or in combination
  • the said effect is small if the boron content is less than 0.02% by weight and if the phosphorus content is less than 0.05% by weight and magnetic characteristics, in particular, the maximum magnetic permeability ( ⁇ max ) and the coercive force (H c ) of the sintered material are deteriorated. Therefore, the boron content and the phosphorus content are limited to 0.02 to 1.00% by weight and 0.05 to 1.00% by weight, respectively.
  • the spherical particle formation effect which is imparted by the alloying of boron and phosphorus with the melt at the atomizing stage is attributed, as was the case with manganese, to the drop in the melting point and the decrease in the surface viscosity caused by boron oxide and phosphorus oxide produced in the surface of the particle, the increase in the sintered density is attributed to the diffusion promoting effect due to alloying of boron and phosphorus with the melt, and the presence of excessive amounts of boron oxide and phosphorus oxide on the surface of the particle obstruct sintering.
  • the average particle diameter is limited to 20 microns or less, since the sintered material constructed with closed pores which has a relative sintered density ratio of 92% or higher cannot be produced and remarkable deterioration in magnetic characteristics (the maxim saturation magnetic flux density, maximum magnetic permeability, and the coercive force) result if the average particle diameter exceeds 20 microns.
  • the compounds of the present invention comprises stainless steel powders which have the carbon content of 0.1 to 1.0% by weight and an average particle diameter of 20 microns or less and binder, and have excellent injection moldability.
  • organic binders whose principal constituents are thermoplastics, or waxes, or mixtures thereof, and may be added with plasticizer, lubricant, debinding promoting agents, and/or inorganic binders, as the case may require.
  • thermoplastics one or more kinds may be chosen from among acrylic, polyethylene, polypropylene, and polystyrene.
  • waxes one or more kinds may be chosen from among natural waxes, which are typically beewax, Japan wax, and montan wax, and synthetic waxes, which are typically low-­molecular weight polyethylene, microcrystalline wax, and paraffin wax.
  • the plasticizer may be selected on the basis of combination with such waxes or waxes which constitute the substantial part, and di-2-ethylhexyl phthalate (DOP), diethyl phthalate (DEP), di-n-butyl phthalate (DHP), and the like may be used.
  • DOP di-2-ethylhexyl phthalate
  • DEP diethyl phthalate
  • DHP di-n-butyl phthalate
  • lubricants higher fatty acids, fatty acid amide, fatty acid esters, and the like may be used, and, depending on the need, waxes may be used as substitute lubricants.
  • subliming substances such as camphor may be added.
  • the binder content of 40 to 50% by volume to the total volume of the compound is preferable.
  • a batch-type kneader or a continuous-type kneader may be used to mix and knead the metallic powder and the binder.
  • a pressurized kneader, a Banbury mixer, and the like favorably suit for the batch kneader.
  • a twin-screw extruder, and the like favorably suit for the continuous kneader.
  • the compound for injection molding of the present invention is obtained by pelletizing the kneaded material by a pelletizer or a crusher (grinder).
  • the compounds of the present invention comprises alloy steel powder and a binder which have been described hereinabove in detail, and have excellent injection moldability.
  • the compounds of the present invention comprises iron-­cobalt alloy steel powder and a binder which have been described hereinabove in detail, and have excellent injection moldability.
  • the high-density sintered stainless steel of the present invention obtained by sintering the stainless steel powder as set forth in (A)-(1) and (A)-(2) hereinabove has the carbon content of 0.05% or less by weight and the bulk density ratio to true density (the relative sintered density ratio) of 92% or higher.
  • Influences of trace carbon, which is impurity, upon the corrosion resistance can be clarified by a corrosion test using organic acids.
  • the relative sintered density ratio is an important property value which has an immense influence upon the corrosion resistance of the sintered material.
  • the relative sintered density ratio of the sintered stainless steel of the present invention is limited to 92% or higher.
  • the stainless steel material of the present invention can be manufactured in the following manner.
  • the stainless steel powder of the present invention and an adequate organic binder are kneaded by a pressurized kneader or the like, and a compound is thus prepared, and such compound is injection molded by an injection molding apparatus so that the injection molded part of a desired configuration may be obtained.
  • the obtained injection molded part is subjected to a debinding treatment at a temperature between 200°C and 600°C to obtain a debound part.
  • the debinding treatment may be carried out in any atmosphere, so long as the atmosphere does not alter the shape of the injection molded part, or causes the shape of the injection molded part uninformly, even if it is altered, it is preferable that, for instance, the debinding treatment is carried out in a nonoxidating atmosphere or a reduced pressure atmosphere.
  • the sintered stainless steel material of the present invention can be manufactured by means of sintering the above-­mentioned debound part.
  • the high magnetic flux density sintered Iron-Cobalt alloy material of the present invention which is obtained by sintering the Iron-Cobalt alloy powder described in (A)-(3) hereinabove, has the carbon content of 0.02% or less by weight and the bulk density ratio to true density of 92% or higher.
  • the reasons for limiting the carbon content of the sintered material to 0.02% or less by weight are set forth below.
  • the carbon content is limited to 0.02% or less by weight, since the maximum magnetic permeability and the coercive force are remarkably deteriorated when the carbon content exceeds 0.02% by weight.
  • the relative sintered density ratio is an important property value which influences the saturated magnetic flux density (B s ), the maximum magnetic permeability ( ⁇ max ), and the coercive force (H c ) of the sintered material.
  • the saturated magnetic flux density, the maximum magnetic permeability and the coercive force altogether are remarkably deteriorated when the relative sintered density ratio is less than 92%.
  • the relative sintered density ratio is limited to 92% or higher, since the sintered material is constructed with closed pores.
  • the above-mentioned sintered material of the present invention is obtained preferably by the method as set forth below.
  • a compound is obtained by mixing alloy steel powder, stainless steel powder, or Iron-Cobalt alloy steel powder with a binder, the obtained compound is injection molded, and then the obtained injection molded part is sintered after it is dewaxed.
  • At least the first-stage of the sintering step is carried out in a reduced pressure atmosphere.
  • the injection molding is carried out ordinarily by an injection molding apparatus designed to handle plastics.
  • provisions against contamination or for extension of the machine life can be made, depending on the need, by carrying out an anti-abrasion treatment of the internal surface of the machine with which the raw material comes in contact.
  • the obtained injection molded part is subjected to a debinding treatment in open atmosphere or neutral or reducing gas atmosphere.
  • the first-stage of the sintering step means the process prior to which the density ratio of the sintered material reaches about 90%.
  • the atmosphere in which the sintering is carried out is to be capable to enabling reduction of oxides of chromium, etc., which obstruct diffusion of atoms during the sintering step, and also capable of removing carbon contained in a large quantity in the debound parts after the debinding treatment.
  • Hydrogen and a reduced pressure atmosphere are cited as those meeting the above-mentioned requisite conditions, as is the case with the manufacture of the ordinary sintered stainless steel material.
  • the pressure of reduced pressure atmosphere is preferably 0.01 torr or lower, and the temperature range is preferably between 1,100°C and 1,350°C.
  • the atmosphere under reduced pressure be replaced by an nonoxidating atmosphere, such as inert gas (e.g. nitrogen, argon) atmosphere and a low dew point hydrogen atmosphere as a protective atmosphere.
  • an nonoxidating atmosphere such as inert gas (e.g. nitrogen, argon) atmosphere and a low dew point hydrogen atmosphere as a protective atmosphere.
  • Stainless steel powders added with carbon and comprising the composition as shown in Table 1 was prepared by an atomizing method using water. Results of studies made on powder characteristics of those steel powders are shown in Table 2.
  • the said evaluation shows a temperature levels at which a certain prescribed viscosity is learned to have been reached by measuring the viscosity of compounds prepared by adding to each samples of steel powder an equal amount of wax-type binder and kneading them together. The lower is the temperature, the lower becomes the viscosity.
  • the compound used as the sample for viscosity measurement was injection molded into specimens of 40 mm width, 20 mm length and 2 mm thickness at 145°C injection nozzle temperature and 30°C mold temperature.
  • the injection molded part was subjected to a debinding treatment in which it was left to stand for 1 hour after having been heated to 600°C from room temperature at a rate of 10°C rise per hour.
  • the debound part was sintered at 1,300°C for 4 hours under 0.0001 torr reduced pressure.
  • the carbon content of the sintered part is additionally shown in Table 2.
  • the carbon content could be reduced to its bare minimum.
  • the reference steel powder No. 5 containing 1.2% carbon could not have its carbon content reduced sufficiently in its sintered form.
  • the stainless steel powders having the composition as shown in Table 3 were prepared by the water atomizing method.
  • Results of studies on powder characteristics of those steel powders are summed up in Table 4.
  • results of studies on sintered parts which were prepared under the same conditions, except for the sintering condition, in Example 1 are shown in Table 4.
  • the sintering was performed in two steps, firstly for 2 hours at 1,135°C under reduced pressure of 0.0001 torr, and secondly immediately following the first step, for another 2 hours at 1,350°C in argon gas atmosphere maintained at 1.02 atm, with argon gas introduced into the same space.
  • stainless steel powders having the spherical particle shape which are suitable for injection molding are provided, production of sintered stainless steel parts of complex configurations are readily realized, whereby the scope of application of sintered stainless steel can be enlarged.
  • Table 5 through Table 7 are examples of the present invention, along with a Comparative Example, for the sintered material prepared by sintering Ferrite-type stainless steel powder, Austenite-type stainless steel powder, and the stainless steel powder of the present invention for high-­density sintering use obtained by the water atomizing method.
  • Ferrite-type stainless steel alloy powder and Austenite-­type stainless steel powder having their respective chemical compositions were prepared by perpendicularly dripping through an orifice nozzle constructed of a refractory material provided on the bottom of a tundish the melt of ingot Ferrite-­type stainless steel alloy and Austenite-type stainless steel alloy manufactured by a high frequency induction furnace, and atomizing the dripped melt by applying a conical water jet of 1,000 Kgf/cm2 pressure encircling the axis of the drip and narrowing in the downward direction.
  • the obtained stainless steel alloy powder was analyzed on a Microtrack grading analyzer for the average particle diameter (the particle diameter of the particle size group with whose addition the cumulative volume measured from the finer particle size group reaches the 50% level of the total volume), the apparent density and the tap density.
  • the viscosity temperature (the temperature at which the viscosity reaches 100 poise) was measured by extruding through a die of 1 mm diameter and 1 mm length under a 10 kg load provided on a flow tester a compound prepared by kneading by a pressurized kneader each one of those alloy powders with wax-type organic binders, the blending ratio of the latter being 46% by volume.
  • the same compound as used as the sample for viscosity measurement was injection molded into specimens of 40 mm width, 20 mm length and 2 mm thickness at 145°C injection nozzle temperature and 30°C mold temperature.
  • the injection molded part was subjected to a dewaxing treatment in which it was left to stand for 1 hour after having been heated to 600°C from room temperature at a rate of 10°C rise per hour.
  • the dewaxed part was sintered at 1,300°C for 4 hours under 0.0001 torr pressure.
  • the obtained sintered part was measured for the specific gravity by means of weighing samples submerged in water, and the relative sintered density ratios were calculated.
  • the stainless steel powders of the present invention which contain nickel, molybdenum, copper, tin, sulfur, selenium and tellurium singularly or in any combination are atomized powders which are in the spherical particle form and exhibit excellent injection moldability and gave sintered material whose carbon content as sintered is 0.01% by weight and relative sintered density ratio of 92% or higher.
  • Fig. 3 shows a relationship between the relative density ratio of sintered material, which has undergone an HIP treatment carried out at 1,350 °C for 1 hour in argon atmosphere maintained at 100 Kgf/cm2, and the relative density ratio after the said HIP treatment, which was measured on samples prepared by injection molding compound made from Ferrite-type and Austenite-type stainless steel powders shown in No. 8 through No. 61 of Example 3, which are examples of the present invention, in Table 5 and Table 7, and then sintering the injection molded part at a temperature between 1,250 and 1,350 °C for 4 hours.
  • Fig. 4 shows results of a corrosion resistance test performed in a boiling 60% nitric acid solution on sintered materials constructed with closed pores and having a relative density ratio of 95%, which was obtained by injection molding compound prepared from Ferrite-type chromium-containing steel powder which has an average particle diameter of 8.0 to 9.0 microns and has the composition of 5.0 to 33.0% by weight of chromium, 0.02 to 0.70% by weight of silicon, 1.00% by weight of manganese, and 0.01% by weight of sulfur, the balance being substantially iron, and vacuum sintered at 10 ⁇ 4 torr at 1350°C.
  • the corrosion velocity remarkably decreases at a chromium content level of 8.0% or more, and there is provided no effect of improving the corrosion resistance even if the chromium content exceeds 30.0% by weight.
  • Fig. 5 shows results of a corrosion resistance test performed in a 1% sulfuric acid solution maintained at 25 °C on sintered material having a relative density ratio of 90% or higher, which was obtained by injection molding compound prepared from Ferrite-type stainless steel powder which has an average particle diameter of 8.0 to 9.0 microns and has the basic alloy composition of 18.23% by weight of chromium, 0.02% by weight of carbon, 0.70% by weight of silicon, 1.00% by weight of manganese, 0.02% by weigh of phosphorus, and 0.01% by weight of sulfur, the balance being substantially iron, added with 0.8 to 5.0% by weight of nickel, 0.2 to 5.0% by weight of molybdenum, and 0.2 to 6.0% by weight of copper either singularly or in any combination, and vacuum sintering the injection molded part at a temperature between 1,250 °C and 1,350 °C for 4 hours at 10 ⁇ 4 torr.
  • the corrosion velocity remarkable deceases at the nickel content of 1.0% or more by weight, the molybdenum content of 0.3% or more by weight, the copper content of 0.5% or more by weight singularly or in any combination, although there is provided no effect of improving the corrosion resistance, even if the nickel content exceeds 4.0% by weight, the molybdenum content exceeds 4.0% by weight, or the copper content exceeds 5.0% by weight.
  • Fig. 6 shows results of a corrosion resistance test performed with a boiling 60% nitric acid solution on sintered material having a relative density ratio of 90% or higher, which was obtained by injection molding compound made from Austenite-type stainless steel powder listed as No. 61 of Example 3, which is an example of the present invention, in Table 7, and vacuum sintering the injection molded part at a temperature between 1,250 °C and 1,350 °C for 4 hours at 10 ⁇ 4 torr
  • Austenite-type stainless steel has its corrosion velocity remarkably decreased at a relative density ratio of 92% or higher, and the material is constructed with closed pores.
  • Fig. 7 shows results of a corrosion resistance test performed with a boiling mixture of 40% acetic acid and 1% formic acid on sintered materials have a relative density ratio of 95% which was obtained by injection molding compound made from Austenite-type stainless steel powder which has an average particle diameter of 8.0 to 9.0 microns and has the basic alloy composition of 18% by weight of chromium, 14% by weight of nickel, 2.5% by weight of molybdenum, 0.70% by weight of silicon, 1.00% by weight of manganese, 0.02% by weight of phosphorus, and 0.01% by weight of sulfur, the balance being substantially iron (the carbon content as sintered being 0.03% by weight) added with 4.0 to 25.0% by weight of nickel, 0.3 to 5.0% by weight of molybdenum, 0.4 to 6.0% by weight of copper, and 0.01 to 0.08% by weight of carbon, either singularly or in any combination, and vacuum sintering the injection molded part at 1,350 °C for 4 hours at 10 ⁇ 4 torr.
  • the corrosion velocity remarkably decreases at a nickel content level of 8.0% or more, the molybdenum content of 0.3% or more by weight, the copper content of 0.5% or more by weight, the carbon content of 0.05% or less by weight either singularly or in any combination, and there is provided no effect of improving the corrosion resistance even if the nickel content exceeds 22.0% by weight, the molybdenum content exceeds 4.0% by weight and the copper content exceeds 5.0% by weight.
  • Fig. 8 shows results of a dry drilling /cutting test performed with a 1 mm diameter drill constructed of SKH-9 revolving at a revolving velocity of 410 m/s on sintered material, which was obtained by injection molding compound made from Ferrite-type stainless steel powder having an average particle diameter of 8.0 to 9.0 microns and the composition of 0.70% by weight of silicon, 1.00% by weight of manganese, 18% by weight of chromium, and Austenite-type stainless steel powder having an average particle diameter of 8.0 to 9.0 microns and the composition of 0.70% by weight of silicon, 1.00% by weight of manganese, 18% by weight of chromium, and 14% by weight of nickel, both of which constitution the basic alloy composition, added with 0.03 to 2.5% by weight of tin, 0.01 to 0.60% by weight of sulfur, 0.025 to 0.25% by weight selenium, and 0.025 to 0.25% by weight of tellurium, either singularly or in any combination, and vacuum
  • the cutting torque remarkably decreases at the tin content of 0.05% or more by weight, the sulfur content of 0.02% or more by weight, the selenium content of 0.05% or more by weight, the tellurium content of 0.05% or more by weight, either singularly or in any combination, although there is provided no effect of improving the cutting torque even if the tin content exceeds 2.00% by weight, the sulfur content exceeds 0.50% by weight, the selenium content exceeds 0.20% by weight and the tellurium content exceeds 0.20% by weight.
  • stainless steel powders whose injection moldability and sinterability are improved by achieving spherical particle formation and modifying surface conditions of the particle by means of atomizing the melt whose composition is so adjusted that the carbon content, the silicon content and the Manganese/Silicon ratio will become 1.20% or less by weight, 0.20% or more by weight, and 1.00 or higher, respectively, from its basic melt composition of 8.0 to 30% by weight of chromium and 8.0 to 22.0% by weight of nickel, to obtain fine powder of an average particle diameter of 20 microns or less. Furthermore, there is provided through use of the said stainless steel powder a high-density, high corrosion resistance sintered stainless steel material having a relative density ratio of 92% or higher and the carbon content of 0.05% or less by weight.
  • a stainless steel powder from which a superior sintered material with remarkable improved corrosion resistance which has a relative density ratio of 92% or higher and a carbon content of 0.05% or less by weight is obtained, and also stainless steel powders for obtaining the said sintered material by atomizing into fine powder of an average particle diameter of 20 microns or less the above-mentioned melt, with which 1.0 to 4.0% by weight of nickel is alloyed in the case of Ferrite-type, and one or both of 0.3 to 4.0% by weight of molybdenum and 0.5 to 5.0% by weight of copper in the case of Ferrite-type or Austenite-type.
  • a stainless steel powder from which a superior sintered material with remarkable improved cutting characteristics which has a relative density ratio of 92% or higher and a carbon content of 0.05% or less by weight is obtained, and also stainless steel powders for obtaining the said sintered material by atomizing into fine powder of an average particle diameter of 20 microns or less the above-­mentioned melt, with which one or more of 0.05 to 2.00% by weight of sulfur, 0.05 to 0.20% by weight of selenium, 0.05 to 0.20% by weight of tellurium is or are alloyed with the said melt in case of Ferrite-type or Austenite-type.
  • Table 8 is an example of the present invention, along with a Comparative Example, for high saturation magnetic flux density sintered material prepared by sintering Iron-Cobalt-type alloy powder and Iron-Cobalt-­Vanadium-type alloy powder, both of which are for high saturation magnetic flux density sintering use, obtained by the water atomizing method.
  • Iron-Cobalt-type and Iron-Cobalt-Vanadium-type alloy powder having their respective chemical compositions shown in Table 8 were prepared by perpendicularly dripping through an orifice nozzle constructed of a refractory material provided on the bottom of a tundish the melt of ingot Iron-Cobalt-type and Iron-Cobalt-Vanadium-type steel manufactured by a high frequency induction furnace, and atomizing the dripped melt by applying a conical water jet of 1,000 Kgf/cm2 pressure encircling the axis of the drip and narrowing in the downward direction.
  • the obtained alloy powder was analyzed on a Microtrack grading analyzer for the average particle diameter (the particle diameter of the particle size group with whose addition the cumulative volume measured from the finer particle size group reaches the 50% level of the total volume), the apparent density and the tap density.
  • the viscosity temperature (the temperature at which the viscosity reaches 100 poise) was measured by extruding through a die of 1 mm diameter and 1 mm length under a 10 kg load provided on a flow tester a compound prepared by kneading by a pressurized kneader each one of those alloy powders with wax-type organic binders, the blending ratio of the latter being 46% by volume.
  • the compound was injection molded into rings of 53 mm outer diameter, 41mm inner diameter, and 4.7 mm height by an injection molding apparatus at an injection molding temperature of 150 °C.
  • the injection molded part was subjected to a dewaxing treatment in nitrogen atmosphere in which it was heated up to 600 °C at a rate of 7.5 °C rise per hour and left to stand for 30 minutes.
  • the dewaxed material was sintered in hydrogen atmosphere in which it was heated up to 700 °C at a rate of 5 °C rise per minute and left to stand for 1 hour at 700 °C, for another hour at 950 °C and the following 2 hours at 1,350 °C. Up to the end of the 950 °C stage, the dew point was controlled to +30 °C, and beyond the said end point, the dew point was controlled to -20°C or lower.
  • the obtained sintered material was measure for the specific gravity by means of weighing samples submerged in water, and the relative sintered density ratios were calculated.
  • samples prepared under the same conditions had wires wound around them and were measured by a self-­registering magnetic flux recorder for magnetic characteristics. Results of the said measurement are shown in Table 8.
  • the compound prepared from the above-mentioned powders exhibit low viscosity values (the viscosity decreases with temperature drops), whereby it is learned that spherical particle formation has been achieved in the powders, hence they have excellent injection moldability.
  • Sintered material which has the carbon content of 0.02% or less by weight and the relative sintered density ratio of 95% was obtained. Hence, sintered material having excellent magnetic characteristics (the saturation magnetic flux density, the maximum magnetic permeability, and the coercive force) can be prepared.
  • a sintered material having the carbon content of 0.01% by weight and a relative sintered density ratio of 95% which exhibits excellent magnetic characteristics (Bs, ⁇ max, Hc) can be obtained.
  • Sintered material having excellent magnetic characteristics can be obtained at the average particle diameter level of 20 microns or lower.
  • Fig. 9 shows a relationship between the relative density ratio of sintered material, which has undergone an HIP treatment carried out at 1,350°C for 1 hour in argon atmosphere maintained at 100 kgf/cm2, and the relative density ratio after the said HIP treatment, which was measured on samples prepared by injection molding compound made from Iron-­Cobalt-type alloy powder shown in No. 3 of Example 4, which is an example of the present invention, in Table 8.
  • a relative density ratio of 92% or higher pores in the sintered material become closed pores and the relative density ratio after the HIP treatment is further improved.
  • D + ⁇ The particle diameter in the particle size group with whose addition made in order of the particle size group (powder fraction) standard from the finest one the cumulative volume registers 84.13%.
  • D50 The particle diameter in the particle size group with whose addition made in order of the particle size group standard from the finest one the cumulative volume registers 50% (50% particle diameter).
  • D - ⁇ The particle diameter in the particle size group with whose addition made in order of the particle size group standard from the finest one the cumulative volume registers 16.87%.
  • D + ⁇ /D50 The geometric standard deviation for all particle size group coarser than the 50% particle diameter.
  • D50/D - ⁇ The geometric standard deviation of all particle size groups finer than the 50% particle diameter.
  • MV The average particle size by volume (the average particle diameter).
  • *2 The density after tapping for 6 min. and 10 min., respectively.
  • *3 Measured by the BET Method.
  • *4 Apparent viscosity was measured by a flow tester (10 kg load, 1 mm diameter x 1 mm length die). "100P", "1,000P", and "10,000P" are defined to indicate respective temperature levels at which each of these viscosity levels is registered. Table 3 No.
  • a sintered material having relative density ratio of 92% or higher whose injection moldability and sinterability are improved by achieving spherical particle formation by means of atomizing the melt whose composition is so adjusted that the carbon content, the silicon content, the manganese content and the Manganese/Silicon ratio will become 1.00% or less by weight, 1.00% or less by weight, 2.00% or less by weight and 1.00 or higher, respectively from Iron-Cobalt-type and Iron-­Cobalt-Vanadium-type alloy melts, to obtain fine powder of an average particle diameter of 20 microns or less.
  • Iron-Cobalt-type and Iron-Cobalt-Vanadium-type alloy powders with remarkably improved injection moldability and sinterability by dint of improved spherical particle formation by atomizing into powders of the average particle diameter of 20 microns or less the melt with which one or both of 0.02 to 1.00% by weight of boron and 0.05 to 1.00% by weight of phosphorus is or are alloyed.

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EP89307117A 1988-07-13 1989-07-13 Stahllegierungspulver für Spritzgussverfahren, seine Verbindungen und ein Verfahren zur Herstellung von Sinterteilen daraus Expired - Lifetime EP0354666B1 (de)

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JP63172532A JPH0225501A (ja) 1988-07-13 1988-07-13 射出成形用ステンレス鋼粉および射出成形用コンパウンドとステンレス鋼焼結体の製造方法
JP172532/88 1988-07-13
JP206720/88 1988-08-20
JP63206719A JPH0257606A (ja) 1988-08-20 1988-08-20 ステンレス鋼微粉および焼結材料
JP206719/88 1988-08-20
JP63206720A JPH0715121B2 (ja) 1988-08-20 1988-08-20 射出成形用Ｆｅ―Ｃｏ系合金微粉およびＦｅ―Ｃｏ系焼結磁性材料

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EP0354666A1 true EP0354666A1 (de) 1990-02-14
EP0354666B1 EP0354666B1 (de) 1995-11-02

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WO1991014526A1 (en) * 1990-03-20 1991-10-03 Höganäs Ab Machinability improving supplementary powder and iron or steel powder containing such supplementary powder
DE10019042A1 (de) * 2000-04-18 2001-11-08 Edelstahl Witten Krefeld Gmbh Stickstofflegierter, sprühkompaktierter Stahl, Verfahren zu seiner Herstellung und Verbundwerkstoff hergestellt aus dem Stahl
WO2016008780A1 (de) * 2014-07-16 2016-01-21 Robert Bosch Gmbh Weichmagnetische legierungszusammensetzung und verfahren zum herstellen einer solchen
EP3546094A1 (de) * 2018-03-29 2019-10-02 Seiko Epson Corporation Weichmagnetisches pulver und verfahren zur herstellung eines sinterkörpers
EP3546095A1 (de) * 2018-03-29 2019-10-02 Seiko Epson Corporation Weichmagnetisches pulver und verfahren zur herstellung eines sinterkörpers
CN111408727A (zh) * 2020-04-10 2020-07-14 泉州天智合金材料科技有限公司 一种适用于mim注射成型不锈钢粉末、制备方法及高抛光件
CN114749667A (zh) * 2022-03-14 2022-07-15 上海喆航航空科技有限公司 一种直升机旋翼桨叶平衡配重合金制造方法

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CN113399668B (zh) * 2021-06-16 2022-10-21 东莞华晶粉末冶金有限公司 热脱脂型粘结剂及喂料、马氏体时效不锈钢及其制备方法

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991014526A1 (en) * 1990-03-20 1991-10-03 Höganäs Ab Machinability improving supplementary powder and iron or steel powder containing such supplementary powder
DE10019042A1 (de) * 2000-04-18 2001-11-08 Edelstahl Witten Krefeld Gmbh Stickstofflegierter, sprühkompaktierter Stahl, Verfahren zu seiner Herstellung und Verbundwerkstoff hergestellt aus dem Stahl
WO2016008780A1 (de) * 2014-07-16 2016-01-21 Robert Bosch Gmbh Weichmagnetische legierungszusammensetzung und verfahren zum herstellen einer solchen
EP3546094A1 (de) * 2018-03-29 2019-10-02 Seiko Epson Corporation Weichmagnetisches pulver und verfahren zur herstellung eines sinterkörpers
EP3546095A1 (de) * 2018-03-29 2019-10-02 Seiko Epson Corporation Weichmagnetisches pulver und verfahren zur herstellung eines sinterkörpers
US11450459B2 (en) 2018-03-29 2022-09-20 Seiko Epson Corporation Soft magnetic powder and method for producing sintered body
CN111408727A (zh) * 2020-04-10 2020-07-14 泉州天智合金材料科技有限公司 一种适用于mim注射成型不锈钢粉末、制备方法及高抛光件
CN114749667A (zh) * 2022-03-14 2022-07-15 上海喆航航空科技有限公司 一种直升机旋翼桨叶平衡配重合金制造方法
CN114749667B (zh) * 2022-03-14 2023-07-21 上海喆航航空科技有限公司 一种直升机旋翼桨叶平衡配重合金制造方法

Also Published As

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DE68924678T2 (de) 1996-06-27
EP0354666B1 (de) 1995-11-02
AU637538B2 (en) 1993-05-27
DE68924678D1 (de) 1995-12-07
AU3802489A (en) 1990-05-03
KR900001447A (ko) 1990-02-27
CA1335759C (en) 1995-06-06
KR930002523B1 (ko) 1993-04-03
AU8892391A (en) 1992-02-06

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