Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/05—Mixtures of metal powder with non-metallic powder
• • 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
  • B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
• • 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
  • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
• • 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
  • B22F1/12—Metallic powder containing non-metallic particles
• • 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
  • B22F3/12—Both compacting and sintering
• • 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
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
• • 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
• • 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
  • C22C33/0264—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 5%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
• • 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
  • B22F2998/10—Processes characterised by the sequence of their steps

Definitions

• the present invention relates to a method for producing a powder mixture for powder metallurgy, and more particularly, to a method for producing a powder mixture for powder metallurgy having characteristics suitable for the production of high-strength sintered parts for automobiles, etc., despite not containing Ni. . Moreover, this invention relates to the sintered compact obtained by the manufacturing method of the sintered compact, and the said manufacturing method.
• Powder metallurgy technology allows parts with complex shapes to be manufactured in a shape very close to the product shape (so-called near net shape) and with high dimensional accuracy. Therefore, if a part is produced using powder metallurgy technology, the cutting cost can be greatly reduced. For this reason, powder metallurgy products to which powder metallurgy technology is applied are used in various fields as various machine parts.
• iron-based powder is mainly used. Iron-based powders are classified into iron powder (for example, pure iron powder), alloy steel powder, and the like depending on the components. Iron-based powders are classified into atomized iron powder, reduced iron powder, and the like based on the production method. And when using the classification
• a sintered compact is manufactured by producing a compact using the iron-based powder as described above and sintering the compact.
• the molded body is generally mixed with iron-based powder, alloy powder such as Cu powder and graphite powder, and a lubricant such as stearic acid and lithium stearate, and then filled into a mold. Then, it is manufactured by pressure molding.
• the density of the molded body obtained by a normal powder metallurgy process is about 6.6 to 7.1 Mg / m 3 .
• These molded bodies are converted into sintered bodies by a subsequent sintering process, and further subjected to sizing and cutting as necessary to form powder metallurgy parts (parts).
• carburizing heat treatment or bright heat treatment may be performed after sintering.
• the iron-based powder mainly the following powders obtained by adding alloy elements to raw powder (pure iron powder) are known; (1) Mixed powder in which each alloy element powder is mixed with pure iron powder, (2) Pre-alloyed steel powder in which each alloy element and pure iron powder are completely alloyed, (3) Partial diffusion alloy steel powder (also referred to as composite alloy steel powder) in which each alloy element powder is partially adhered and diffused on the surface of pure iron powder or pre-alloy steel powder.
• the mixed powder (1) has the advantage of having high compressibility comparable to that of pure iron powder.
• each alloy element does not sufficiently diffuse into Fe to form a heterogeneous structure, and as a result, the strength of the finally obtained sintered body may be inferior.
• Mn, Cr, V, Si, etc. are used as alloy elements, these elements are oxidized more easily than Fe, so that the sintered body finally obtained by oxidation during sintering There was a problem that the strength of the steel was lowered.
• prealloyed steel powder (2) above If the prealloyed steel powder (2) above is used, segregation of the alloy elements can be completely prevented, and the structure of the sintered body can be made uniform. Therefore, in addition to stabilizing the mechanical properties of the sintered body, even when Mn, Cr, V, Si, etc. are used as alloy elements, by limiting the type and amount of alloy elements, It is possible to achieve a low oxygen content in the body.
• prealloyed steel powder is manufactured by atomizing molten steel, it tends to cause solid solution hardening of the steel powder due to oxidation and complete alloying in the atomizing process of the molten steel. There was a problem that the density of the body was difficult to increase.
• the partially diffused alloy steel powder of (3) above is a mixture of pure iron powder or pre-alloyed steel powder with metal powder of each alloy element, heated in a non-oxidizing or reducing atmosphere, In addition, the metal powder is partially diffusion bonded to the surface of the prealloyed steel powder. Therefore, by using the partial diffusion alloy steel powder, while avoiding the problem of the iron-based mixed powder of (1) and the pre-alloyed steel powder of (2), the iron-based mixed powder of (1) and the above ( The advantage of the prealloyed steel powder of 2) can be obtained.
• the partial diffusion alloy steel powder by using the partial diffusion alloy steel powder, it is possible to achieve both low oxygen content and high compressibility comparable to pure iron powder. Furthermore, since the structure of the sintered body can be a composite structure composed of a complete alloy phase and a partially concentrated phase, the strength of the sintered body is further improved. Therefore, the partially diffused alloy steel powder can meet the recent demand for higher strength of parts, and its development is widely performed.
• Ni and Mo are mentioned as basic alloy components generally used for the production of the above partially diffused alloy steel powder.
• Ni has the effect of improving the toughness of the sintered body. This is because austenite is stabilized by the addition of Ni, and as a result, more austenite remains as retained austenite without being transformed into martensite after quenching. Moreover, Ni has the effect
• Mo has the effect of improving hardenability. Therefore, Mo suppresses the formation of ferrite during the quenching process and facilitates the formation of bainite or martensite, thereby strengthening the matrix of the sintered body by transformation. Mo has both an effect of solid-solution strengthening by solid solution in the matrix and an effect of precipitation strengthening the matrix by forming fine carbides. Furthermore, since Mo has good gas carburizing properties and is a non-grain boundary oxidizing element, it also has an effect of carburizing and strengthening the sintered body.
• Patent Document 2 discloses that an iron-based powder having an average particle diameter of 1 to 18 ⁇ m and Cu powder having an average particle diameter of 1 to 18 ⁇ m are 100: A method for producing an iron-based sintered body that is mixed and molded and sintered at a weight ratio of (0.2 to 5) is disclosed.
• the sintered body density is 7.42 g / cm 3 or more, which is not normally high. This makes it possible to obtain a sintered body having a high density.
• mixed powder for high-strength sintered parts using partially diffused alloy steel powder for example, in Patent Document 3, metal Cu powder and graphite powder are mixed with alloy steel powder to which Ni and Mo are diffused and adhered. A mixed powder for high strength sintered parts is disclosed.
• the sintered material using the mixed powder described in Patent Document 1 and Patent Document 3 described above and the sintered material obtained by the method described in Patent Document 2 include the following: It turns out that there is a problem like this.
• the sintered material described in Patent Document 1 requires at least 1.5 mass% of Ni, and, as can be seen from the examples, substantially contains 3 mass% or more of Ni. Therefore, in order to obtain a high strength of 800 MPa or more with the sintered material described in Patent Document 1, a large amount of Ni such as 3 mass% or more is required. Furthermore, in order to obtain a sintered body having a strength of 1000 MPa or more after carburizing, quenching, and tempering treatment, a larger amount of Ni is considered necessary.
• Ni is an element that is disadvantageous from the viewpoint of dealing with environmental problems in recent years and from the viewpoint of recycling, and is an element that should be avoided as much as possible. Further, the addition of several mass% of Ni is extremely disadvantageous in terms of cost. Furthermore, when Ni is used as an alloy element, there is also a problem that long-time sintering is required in order to sufficiently diffuse Ni into iron powder or alloy steel powder.
• the average particle size of the iron-based powder used is 1 to 18 ⁇ m, which is smaller than usual.
• the particle size is small, the fluidity of the mixed powder is deteriorated, and there is a problem that the working efficiency when filling the powder with a die is reduced when performing press molding.
• the mixed powder contains metallic Cu powder.
• This metal Cu powder melts during the sintering process and penetrates between the iron powder grains, thereby expanding the inter-particle distance of the iron powder and increasing the size of the sintered body compared to the size of the compact. . Therefore, the density of the sintered body is lower than that of the molded body. This phenomenon is generally known as Cu expansion. When the density reduction due to the Cu expansion is large, there is a disadvantage that the strength and toughness of the sintered body are reduced.
• the present invention has excellent characteristics equivalent to or better than those in the case of containing Ni (for example, tensile strength and toughness after carburizing, quenching, and tempering in spite of not containing Ni (Ni-free)). It is an object of the present invention to provide a method for producing a powder mixture for powder metallurgy, which can obtain a sintered body having a). Moreover, this invention aims at providing the sintered compact obtained by the manufacturing method of the sintered compact using the said mixed powder for powder metallurgy, and the said manufacturing method.
• Mo and Cu are partially diffused into an iron-based powder to obtain a partially-diffused alloy steel powder, and Ni is obtained by using a mixed powder for powder metallurgy obtained by mixing the partially-diffused alloy steel powder with graphite powder.
• a sintered body having characteristics equal to or higher than that in the case of including Ni may be obtained although it is not included.
• the composition of the mixed powder for powder metallurgy is controlled to be within a specific range, and the iron group It is necessary to use a powder of cuprous oxide (Cu 2 O) instead of metal Cu powder as the Cu source used when producing the partial diffusion alloy steel powder with an average particle size of the powder of 30 to 120 ⁇ m.
• a powder of cuprous oxide (Cu 2 O) instead of metal Cu powder as the Cu source used when producing the partial diffusion alloy steel powder with an average particle size of the powder of 30 to 120 ⁇ m.
• cuprous oxide powder By using cuprous oxide powder, it is possible to avoid Cu expansion that occurs when metal Cu powder is used, and to suppress density reduction of the sintered body.
• the present invention has been made on the basis of the above knowledge, and the gist configuration thereof is as follows.
• a method of producing a mixed powder for powder metallurgy comprising a second mixing step of mixing the partially diffused alloy steel powder with graphite powder to obtain a mixed powder for powder metallurgy,
• the iron-based powder has an average particle size of 30 to 120 ⁇ m, Using cuprous oxide powder as the Cu-containing powder,
• the composition of the mixed powder for powder metallurgy includes Mo: 0.2 to 1.5 mass%, Cu: 0.5 to 4.0 mass%, C: 0.1 to 1.0 mass%, and the balance of Fe and inevitable
• a method for producing a sintered body comprising molding and sintering a powder mixture for powder metallurgy obtained by the method for producing a powder mixture for powder metallurgy described in 1 or 2 above.
• the present invention it is possible to obtain a mixed powder for powder metallurgy capable of producing a sintered body having excellent characteristics equivalent to or better than those containing Ni, although it does not contain Ni. Moreover, since the mixed powder for powder metallurgy according to the present invention has high fluidity, it is excellent in work efficiency when filling the mold with the mixed powder for powder metallurgy for press molding. Furthermore, according to the present invention, a sintered body having both excellent strength and toughness can be produced at low cost even by a normal sintering method.
• the method for producing a powder mixture for powder metallurgy includes the following steps (1) to (3): (1) A first mixing step in which an iron-based powder is mixed with a Mo-containing powder and a Cu-containing powder to obtain a raw material mixed powder; (2) A diffusion adhesion step in which Mo and Cu are diffused and adhered to the surface of the iron-based powder to form a partially diffused alloy steel powder by heat-treating the raw material mixed powder, and (3) the partially diffused alloy steel powder, A second mixing step in which graphite powder is mixed to obtain a mixed powder for powder metallurgy.
• the iron-based powder an iron-based powder having an average particle size of 30 to 120 ⁇ m is used. Moreover, cuprous oxide powder is used as the Cu-containing powder. Further, the composition of the mixed powder for powder metallurgy includes Mo: 0.2 to 1.5 mass%, Cu: 0.5 to 4.0 mass%, C: 0.1 to 1.0 mass%, and the remaining Fe. And consisting of inevitable impurities.
• a mixed powder for powder metallurgy is manufactured by mixing metal Cu powder and graphite powder with partially diffused alloy steel powder to which Mo is diffused and adhered.
• cuprous oxide powder is used as a Cu source for diffusing and adhering Cu in addition to diffusing and adhering Cu to the iron-based powder together with Mo.
• % means mass% unless otherwise specified.
• amount of Mo, the amount of Cu, and the amount of graphite powder shall mean each content with respect to the whole mixed powder for powder metallurgy.
• First mixing step In the first mixing step, an iron-based powder is mixed with a Mo-containing powder and a Cu-containing powder to obtain a raw material mixed powder.
• the mixing method used at the said 1st mixing process For example, it can carry out in accordance with a conventional method using a Henschel mixer, a cone type mixer, etc.
• what is necessary is just to adjust the compounding ratio of the iron-based powder mixed, the Mo containing powder, and the Cu containing powder so that the component composition of the powder mixture for powder metallurgy finally obtained may become the range mentioned later. That is, the mixture is mixed with the powder for powder metallurgy so that the Mo amount is 0.2 to 1.5% and the Cu amount is 0.5 to 4.0%.
• the iron-based powder used has an average particle size of 30 to 120 ⁇ m.
• the average particle size of the iron-based powder is set to 30 ⁇ m or more.
• the average particle diameter is preferably 40 ⁇ m or more, and more preferably 50 ⁇ m or more.
• the average particle size of the iron-based powder is set to 120 ⁇ m or less.
• the average particle diameter is preferably 100 ⁇ m or less, and more preferably 80 ⁇ m or less.
• the average particle diameter in the present invention is intended to mean a median diameter (d 50) in volume.
• iron-based powder means a powder having an Fe content of 50% by mass or more.
• examples of the iron-based powder include pure iron powder and alloy steel powder. It is preferable to use iron powder (pure iron powder) as the iron-based powder.
• the iron-based powder is not particularly limited, and any iron-based powder produced by any method can be used. From the viewpoint of availability, an iron-based powder produced by the atomization method or the reduction method. Is preferably used.
• an iron-based powder produced by the atomization method any of so-called atomized powder (as-atomized powder) and atomized powder (atomized powder) can be used.
• the atomized raw powder means a powder obtained by atomizing molten steel, arbitrarily dried and classified, and not subjected to heat treatment for deoxidation (reduction) or decarburization.
• the atomized powder means a powder reduced by treating the atomized raw powder in a reducing atmosphere.
• As the iron-based powder produced by the reduction method it is preferable to use reduced iron powder obtained by reducing mill scale or iron ore produced during the production of steel.
• the apparent density of the iron-based powder is not particularly limited, but is preferably 1.7 to 3.5 Mg / m 3 .
• the apparent density of the iron-based powder is preferably about 2.0 to 3.5 Mg / m 3 , More preferably, it is set to ⁇ 3.2 Mg / m 3 .
• the apparent density of the iron-based powder is preferably about 1.7 to 3.0 Mg / m 3. More preferably, it is set to 2 to 2.8 Mg / m 3 .
• the apparent density is measured by the test method of JIS Z 2504.
• the specific surface area of the iron-based powder is not particularly limited, but is preferably 0.002 to 0.5 m 2 / g.
• the specific surface area of the iron-based powder is preferably about 0.005 m 2 / g or more, 0.01 m 2 / g or more More preferably.
• the upper limit of the specific surface area is preferably 0.1 m 2 / g.
• the specific surface area of this iron-base powder shall be about 0.01 m ⁇ 2 > / g or more, 0.02 m ⁇ 2 > / g g or more is more preferable.
• the upper limit of the specific surface area is preferably 0.3 m 2 / g.
• Mo-containing powder The Mo-containing powder is a powder that functions as a Mo source in the diffusion adhesion step described later. Any powder can be used as the Mo-containing powder as long as it contains Mo as an element. Therefore, any one of metal Mo powder (pure Mo powder), Mo alloy powder, and Mo compound powder can be used. Can also be used. As the Mo alloy powder, for example, Fe—Mo (ferromolybdenum) powder can be used. Examples of the Mo compound powder include powders of Mo compounds such as Mo oxide, Mo carbide, Mo sulfide, and Mo nitride. These Mo-containing powders may be used alone or in combination.
• the Cu-containing powder is a powder that functions as a Cu source in the diffusion adhesion step described later.
• cuprous oxide powder as the Cu-containing powder, Cu expansion that occurs when metal Cu powder is used can be avoided, and density reduction of the sintered body can be suppressed. Further, cuprous oxide is chemically stable and does not oxidize (rust) like metal Cu, so that it is easy to handle. Furthermore, since cuprous oxide (Cu 2 O) has a smaller oxidation number than copper oxide (CuO), it can be easily reduced to metal Cu in the diffusion adhesion step described later. For example, in the diffusion adhesion process, when the raw material mixed powder is heat-treated in a hydrogen atmosphere, by using cuprous oxide, in addition to reducing the amount of hydrogen required for reduction, the heating temperature can be lowered, Processing time can also be shortened.
• the average particle diameter of the Cu-containing powder is not particularly limited, but is preferably 5 ⁇ m or less. By making the average particle size 5 ⁇ m or less, the effect of improving the strength and toughness by Cu can be further improved.
• the average particle size is more preferably 4.5 ⁇ m or less.
• the lower limit of the average particle diameter of the Cu-containing powder is not particularly limited, but if the average particle diameter is excessively lowered, the production cost of the Cu-containing powder increases. Therefore, the average particle size of the Cu-containing powder is preferably 0.2 ⁇ m or more, and more preferably 1.0 ⁇ m or more.
• the average particle diameter of a general commercially available metal Cu powder is about 20 to 40 ⁇ m.
• the heat treatment can be performed in any atmosphere, but is preferably performed in a reducing atmosphere, and more preferably in a hydrogen-containing atmosphere.
• a hydrogen gas atmosphere can also be used as the hydrogen-containing atmosphere.
• the heat treatment may be performed at atmospheric pressure or under reduced pressure, and may be performed under vacuum.
• the temperature of the heat treatment is not particularly limited, but is preferably 800 to 1000 ° C.
• the partial diffusion alloy steel powder obtained as described above is usually in a state in which iron-based powder particles contained in the partial diffusion alloy steel powder are sintered and solidified. Therefore, it is preferable to provide a pulverization / classification step of pulverizing and classifying the partially diffused alloy steel powder after the diffusion adhesion step and prior to the next second mixing step. For example, after pulverizing to a desired particle size, the coarse powder can be removed by classification with a sieve having a predetermined opening.
• the maximum particle size of the partially diffused alloy steel powder is preferably 180 ⁇ m or less.
• the partially diffusion alloy steel powder can be optionally annealed.
• the partial diffusion alloy steel powder preferably contains Mo and Cu, and has a component composition consisting of the remaining Fe and inevitable impurities.
• inevitable impurities contained in the partially diffused alloy steel powder include C, O, N, and S. These contents are each an internal number of the partially alloyed steel powder, and C: 0.02%
• the O content is more preferably 0.25% or less.
• the graphite powder may be mixed according to a conventional method, for example, by a method used for general powder mixing. Moreover, what is necessary is just to adjust the compounding ratio of the partial diffusion alloy steel powder and graphite powder to mix so that the component composition of the mixed powder for powder metallurgy finally obtained may become the range mentioned later. In other words, the mixed powder for powder metallurgy is mixed so that the C content is 0.1 to 1.0% with respect to the whole.
• the graphite powder is not particularly limited, and an arbitrary one can be used.
• the average particle size of the graphite powder is not particularly limited, but is preferably about 1 to 50 ⁇ m.
• the final composition of the mixed powder for powder metallurgy includes Mo: 0.2 to 1.5%, Cu: 0.5 to 4.0%, and C: 0.1 to 1.
• the component composition consists of 0% and the balance Fe and inevitable impurities.
• an additive such as a lubricant can be added to the powder metallurgy alloy steel powder.
• the “component composition of the mixed powder for powder metallurgy” refers to the mixed powder, The component composition of the part except the said additive material, ie, the part which consists of a partial diffusion alloy steel powder and graphite powder shall be pointed out.
• Mo 0.2 to 1.5%
• the Mo content is preferably 0.3% or more, and more preferably 0.4% or more.
• the Mo content is 1.5% or less.
• the Mo content is preferably 1.0% or less, and more preferably 0.8% or less.
• the Cu content is 0.5% or more.
• the Cu content is preferably 1.0% or more, and more preferably 1.5% or more.
• the Cu content is 4.0% or less.
• the Cu content is preferably 3.0% or less, and more preferably 2.5% or less.
• C 0.1 to 1.0%
• C is an element having an effect of improving the strength and fatigue strength of the sintered body.
• C content shall be 0.1% or more.
• the C content exceeds 1.0%, it becomes hypereutectoid, so that a lot of cementite is precipitated, and the strength of the sintered body is lowered. Therefore, the C content is 1.0% or less.
• a sintered body in one embodiment of the present invention, can be obtained by molding and sintering the powder mixture for powder metallurgy.
• the molding is not particularly limited and can be performed by any method as long as it is a method capable of molding a powder mixture for powder metallurgy.
• a mixed powder for powder metallurgy is filled in a mold and pressure-molded.
• the pressing force in the pressure molding is preferably 400 to 1000 MPa.
• the temperature during the pressure molding is preferably from room temperature (about 20 ° C.) to about 160 ° C.
• the powder for metallurgy powder is used to improve machinability.
• the machinability improving powder for example, MnS or the like can be used.
• the addition of the machinability improving powder can be performed according to a conventional method.
• a lubricant can be further added to the powder mixture for powder metallurgy.
• a powdery lubricant is preferably used.
• the molding can be performed by applying or attaching a lubricant to the mold.
• any lubricant such as a metal soap such as zinc stearate or lithium stearate, or an amide wax such as ethylenebisstearic acid amide can be used.
• the amount of the lubricant is preferably about 0.1 to 1.2 parts by mass with respect to 100 parts by mass of the powder mixture for powder metallurgy.
• the molded body obtained as described above is sintered.
• the sintering is preferably performed in a temperature range of 1100 to 1300 ° C. If the sintering temperature is less than 1100 ° C., the sintering does not proceed sufficiently, so it is difficult to obtain a sintered body having excellent tensile strength (1000 MPa or more). On the other hand, if the sintering temperature exceeds 1300 ° C., the life of the sintering furnace is shortened, which is economically disadvantageous.
• the sintering time is preferably 10 to 180 minutes.
• the sintered body obtained by using the mixed powder for powder metallurgy according to the present invention has an excellent tensile strength compared to a sintered body obtained by molding and sintering a conventional powder under the same conditions. It has toughness.
• the obtained sintered body can be further optionally strengthened.
• the strengthening treatment include carburizing quenching, bright quenching, induction quenching, and carbonitriding.
• the sintered body using the powder metallurgy mixed powder according to the present invention has improved strength and toughness compared to the conventional sintered body without the strengthening treatment. Yes.
• strengthening process should just be performed according to a conventional method.
• the mixed powder for powder metallurgy was manufactured according to the following procedure.
• the iron-based powder was mixed with a Mo-containing powder and a Cu-containing powder to obtain a raw material mixed powder.
• a Mo-containing powder atomized raw powder having an apparent density shown in Table 1 was used. The specific surface area of the iron-based powder was 0.39 m 2 / g.
• Mo-containing powder oxidized Mo powder having an average particle size of 10 ⁇ m was used.
• Cu-containing powder cuprous oxide powder having an average particle size shown in Table 1 was used.
• the mixing was performed for 15 minutes using a V-type mixer.
• the compounding quantity of each powder was adjusted so that content of Mo and Cu in the mixed powder for powder metallurgy finally obtained might become the value shown in Table 1.
• the metal Cu powder is added in the second mixing step, and the first In the mixing step, only the Mo-containing powder was added, and then the diffusion adhesion step was performed.
• no. 29, in the first mixing step to the iron-based powder, a metal Ni powder having an average particle size of 8 ⁇ m, a metal Cu powder having an average particle size of 28 ⁇ m (the same metal Cu powder as in Comparative Examples No. 1 and 3), And the oxidation Mo powder (the same oxidation Mo powder as the example of this invention) with an average particle diameter of 10 micrometers was mixed, and the said diffusion adhesion process was implemented.
• the composition of the partially diffused alloy steel powder in No. 29 was 4% Ni-1.5% Cu-0.5% Mo-Fe.
• the obtained partial diffusion alloy steel powder was pulverized and classified by the following procedure.
• pulverization with a hammer mill was performed three times in order to pulverize the powder.
• the opening of the hammer mill rostral was reduced in order of 3 mm (first time), 2 mm (second time), and 1 mm (third time).
• the pulverized powder is passed through a vibrating sieve having an opening of 180 ⁇ m, and the coarse powder remaining on the sieve is removed and discarded, and only the portion of the particle size of 180 ⁇ m or less under the sieve is collected, and the next second mixing step It was used for.
• the balance of the alloy steel powder in the table is iron and inevitable impurities, but the amount of inevitable impurities in the alloy steel powder used in the present invention is 0.2% or less with respect to the amount of partial alloy steel powder. . No. In 1 and 3, the metal Cu powder was mixed with the graphite powder so that the Cu content in the mixed powder for powder metallurgy would be the value shown in Table 1.
• the mixed powder for powder metallurgy was pressure-molded to produce a rod-shaped compact having a length: 55 mm, a width: 10 mm, and a thickness: 10 mm.
• Ten compacts were prepared from each powder metallurgy mixed powder.
• the density of the molded body was 7.0 Mg / m 3 .
• the rod-shaped molded body was sintered to obtain a rod-shaped sintered body.
• the sintering was performed in a propane modified gas atmosphere, which is a reducing atmosphere, under conditions of temperature: 1130 ° C. and time: 20 minutes.
• a tensile test was performed by the method prescribed in JIS Z 2241 to measure the tensile strength.
• the value of the tensile strength was the average value of the measured values of the five test pieces. Furthermore, the case where the measured tensile strength was 1000 MPa or more was determined to be acceptable ( ⁇ ), and the case where it was less than 1000 MPa was determined to be unacceptable (x).

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• 2016
  • 2016-09-12 KR KR1020187002723A patent/KR102058836B1/ko active IP Right Grant
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