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EP-3702063-B1 - FE-BASED METAL POWDER FOR MOLDING

EP3702063B1EP 3702063 B1EP3702063 B1EP 3702063B1EP-3702063-B1

Inventors

  • KUSE, TETSUJI
  • FUKUMOTO, SHINGO

Dates

Publication Date
20260506
Application Date
20181009

Claims (8)

  1. An Fe-based metal powder for a rapid melt-quenching solidification process, wherein the rapid melt-quenching solidification process includes at least one selected from: a three-dimensional additive manufacturing method; a thermal spraying method; and a laser coating method, and wherein the Fe-based metal powder is made of an Fe-based alloy, comprising: Ni in an amount of 15.0% to 21.0% by mass; Co in an amount of 0% to 0.5% by mass; Mo in an amount of 0% to 7.0% by mass; Ti in an amount of 0.1% to 6.0% by mass; Al in an amount of 0.1% to 3.0% by mass; and the balance being Fe and incidental impurities, further wherein: the metal powder has a mean particle diameter D50 of 15 µm to 50 µm and the ratio D50/TD is 0.2 to 20, the D50/TD being a ratio of the mean particle diameter D50, in µm, of the metal powder to a tap density TD, in Mg/m 3 , of the metal powder, wherein the mean particle diameter D50 is measured as indicated in the description, and the tap density TD is measured in accordance with JIS Z 2512 under the conditions of a drop height of 10 mm and a number of taps of 200, using a cylinder having a volume of 100 cm 3 filled with 50 g of the metal powder.
  2. A method of producing a shaped article using a raw Fe-based metal powder according to Claim 1, comprising the steps of: (1) providing Fe-based metal powder made of Fe-based alloy containing: Ni in an amount of 15.0% to 21.0% by mass; Co in an amount of 0% to 0.5% by mass; Mo in an amount of 0% to 7.0% by mass; Ti in an amount of 0.1% to 6.0% by mass; Al in an amount of 0.1% to 3.0% by mass; and the balance being Fe and incidental impurities, and (2) melting and then solidifying the Fe-based metal powder to produce a non-heated shaped article, wherein the step of melting and then solidifying the Fe-based metal powder comprises a rapid melt-quenching solidification process, wherein the rapid melt-quenching solidification process includes at least one selected from: a three-dimensional additive manufacturing method; a thermal spraying method; and a laser coating method.
  3. The method according to claim 2, wherein the non-heated shaped article has a Rockwell hardness of 30 to 40.
  4. The method according to claim 2 or 3, further comprising, subsequent to step (2), the step of: (3) heating the non-heated shaped article to produce a shaped article.
  5. The method according to claim 4, wherein step (3) comprises the substeps of: (3-1) solutionizing the non-heated shaped article; and (3-2) aging the solutionized shaped article.
  6. The method according to claim 5, wherein substep (3-1) is performed at a temperature of 700 to 900°C for a period of 1.0 to 3.0 hours, and substep (3-2) is performed at a temperature of 450 to 550°C for a period of 3.0 to 6.0 hours.
  7. The method according to any one of claims 4 to 6, wherein the shaped article after step (3) has a Rockwell hardness of 50 to 60.
  8. The method according to any one of claims 4 to 7, wherein the shaped article after step (3) satisfies the following expressions (I) and (II): 1.5 ≤ A TH / A TR × C TH / C TR ≤ 3.5 and 1.5 ≤ B TH / B TR × C TH / C TR ≤ 3.5 where, A TH represents tensile strength at 400°C, A TR represents tensile strength at 25°C, B TH represents 0.2% proof stress at 400°C, B TR represents 0.2% proof stress at 25°C, C TH represents elongation at break at 400°C, and C TR represents elongation at break at 25°C.

Description

TECHNICAL FIELD The present invention relates to metal powder to be used in a rapid melt-quenching solidification process, such as a three-dimensional additive manufacturing method, a thermal spraying method, a laser coating method. The present invention more specifically relates to Fe-based alloy powder. BACKGROUND ART Three dimensional (3D) printers are used in manufacturing shaped metal articles. In these 3D printers, the shaped articles are manufactured by an additive manufacturing method. In the additive manufacturing method, spread metal powder is irradiated with a laser beam or an electron beam. This irradiation melts particles of the metal powder and the particles then solidify. Such particles are bonded to each other through the melting and the subsequent solidification. Irradiation is selectively applied to some portions of the metal powder. Unirradiated portions in the powder do not melt. Bonded layers can be formed only in the irradiated portions. Additional metal powder is spread over the bonded layers. This metal powder is irradiated with a laser beam or an electron beam. This irradiation melts particles of the additional metal powder, and the particles then solidify. Such particles are bonded to each other through the melting and the subsequent solidification, and fresh bonded layers can be formed. The fresh bonded layers are also connected to the bonded layers formerly formed. Repetition of the bonding by irradiation causes an aggregate of the bonding layers to gradually grow. Such stepwise growth produces a three-dimensional shaped article. A complicatedly shaped article can be readily produced by the additive manufacturing method. PTL 1 (JP4661842B) discloses an example additive manufacturing method. Requirements for alloys used in structures for, for example, aircraft and space fields are high strength and high fatigue resistance. Maraging steel is suitable for such applications. PTL 2 (JP2013-253277A) discloses maraging steel containing Fe, which is a main element, Ni, Co and Mo. The content of Co in the maraging steel is 7% by mass or more. The maraging steel also contains W. The maraging steel does not contain Ti. PTL 3 (JP2008-185183A) discloses maraging steel containing Ni, Cr, Mo and Co. The maraging steel has undergone a nitriding treatment. PTL 4 (WO 2007/027724 A2) discloses maraging steel compositions, methods of forming the same, and articles formed therefrom comprising, by weight, 15.0 to 20.0% Ni, 2.0 to 6.0% Mo, 3.0 to 8.0% Ti, up to 0.5% Al, the balance Fe and residual impurities CITATION LIST PATENT LITERATURES PTL 1: JP4661842BPTL 2: JP2013-253277APTL 3: JP2008-185183APTL: WO2007/207724 A2 SUMMARY OF INVENTION In an additive manufacturing method, a metal material is rapidly melted and then quenched to solidify. Conventional maraging steel is not suitable for metal powder used in processes involving such rapid melt-quenching solidification. An Fe-based alloy has been demanded that is suitable for the additive manufacturing method and that can provide a shaped article having superior mechanical properties. Such an alloy is also useful in, for example, a thermal spraying method, and a laser coating method. An object of the present invention is to provide an Fe-based metal powder that is suitable for a process involving rapid melt-quenching solidification, and that can provide a shaped article having superior properties. The present invention is defined by the appended claims. A shaped article having superior properties can be produced from an Fe-based metal powder according to the present invention through a process involving rapid melt-quenching solidification. DESCRIPTION OF EMBODIMENTS General maraging steel contains substantially no C but contains alloying elements, such as Ni, Mo, Ti, and Co. In this maraging steel, intermetallic compounds, such as a Ni3Mo phase and a Ni3Ti phase are precipitated in a martensitic matrix. Such intermetallic compounds contribute to high hardness and high strength in the maraging steel. Co lowers the solid solubility limit of Mo. Accordingly, martensite having a larger amount of Co contains a larger amount of supersaturated Mo. The addition of Co facilitates precipitation of a Ni3Mo phase in the martensite. In contrast, a large amount of Co, which is an austenitizing element, inhibits martensitic transformation. The addition of a large amount of Co promotes the formation of a µ phase or a σ phase, and thereby causes embrittlement of the alloy. Furthermore, Co is subject to "Ordinance on Prevention of Hazards Due to Specified Chemical Substances", and the addition of a large amount of Co into Fe is not preferred from the viewpoint of compliance with the Ordinance. Under such circumstances, the amount of the Co additive should be preferably reduced. However, a steel having the reduced amount of Co barely leads to precipitation of the Ni3Mo phase, resulting in insufficient mechanical properties, such as hardness and strength. The present inve