Classifications

• • 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
  • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
  • B22F10/20—Direct sintering or melting
  • B22F10/25—Direct deposition of metal particles, e.g. direct metal deposition [DMD] or laser engineered net shaping [LENS]
• • 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
  • B22F3/24—After-treatment of workpieces or articles
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y10/00—Processes of additive manufacturing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y70/00—Materials specially adapted for additive manufacturing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y80/00—Products made by additive manufacturing
• • 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
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/36—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.7% by weight of carbon

Definitions

• the present invention relates to an Fe-based alloy, an alloy component and its manufacture, and a method for manufacturing the alloy component.
• hot work tool steels with high high-temperature strength such as SKD8 specified in JIS G 4404, and high-speed tool steels, such as SKH51 specified in JIS G 4403, have been used for tools such as punches and dies used in hot precision press processing.
• these steels have problems with being prone to settling, wear, breakage, cracking, and heat cracking.
• Patent Document 1 discloses a high-speed tool steel having, by mass%, 0.4 to 0.9% C, 1.0% or less Si, 1.0% or less Mn, 1.5 to 6% of one or both of W and Mo (1/2W+Mo) (however, W is 3% or less), and 0.5 to 3% of one or both of V and Nb (V+Nb), wherein the average grain size of precipitated carbides dispersed in the matrix is 0.5 ⁇ m or less and the distribution density thereof is 80 ⁇ 10 3 pieces/mm 2 or more.
• coarse primary carbides are formed in the ingot due to solidification segregation during cooling during ingot making, such as the casting or remelting process of the steel ingot.
• the presence of these coarse primary carbides promotes the generation and propagation of cracks, thereby reducing toughness and heat crack resistance.
• the precipitated carbides have a finely dispersed uniform structure. To obtain such a structure, soaking at 1200 to 1300°C for 10 to 20 hours is required. However, even if soaking is performed in this manner, quenching and tempering are performed in the subsequent process to obtain pressing tools such as dies and punches, and metal molds.
• coarse precipitated carbides may be precipitated, which may reduce toughness and heat crack resistance.
• the present invention aims to provide an Fe-based alloy, an alloy part, a product thereof, and a method for manufacturing an alloy part, which are unlikely to crack and are expected to have high toughness and heat crack resistance.
• the first invention is an Fe-based alloy comprising C, Cr, W, Mo, and V with the remainder being Fe and unavoidable impurity elements, having an alloy structure including an Fe-BCC phase, wherein, in mass%, the Fe-BCC phase contains C of 3% to 7%, Cr of 2% to 6%, W of 0.5% to 4%, Mo of 0.5% to 4%, V of 0.5% to 4%, and Fe of 75% to 90%, and precipitated carbides precipitated in the Fe-BCC phase, and the precipitated carbides have an average circle-equivalent grain size of 1.30 ⁇ m or less.
• the average circle-equivalent particle size of the precipitated carbides can be calculated by calculating the average area of the precipitated carbides within the observation field using electron backscattered diffraction (EBSD), and then calculating the circle-equivalent diameter from that area.
• EBSD electron backscattered diffraction
• the Fe-BCC phase occupies 96% or more of the alloy structure in terms of area ratio.
• the average circle-equivalent grain size of the precipitated carbides is 0.60 ⁇ m or more.
• the Fe-based alloy as a whole contains, by mass%, C of 0.1% to 2%, Cr of 2% to 6%, W of 0.5% to 4%, Mo of 0.5% to 4%, V of 0.5% to 4%, Si of 1.0% or less, Mn of 1.0% or less, Co of 4% or less, with the remainder being Fe and unavoidable impurity elements.
• the material further contains either Si or Mn, or both, and that, by mass%, Si is 1.0% or less, and Mn is 0.1% or more and 1.0% or less.
• the Fe-based alloy as a whole further contains 0.5% to 4% Co, and that the Fe-BCC phase further contains 0.5% to 4% Co.
• fine precipitated carbides are dispersed in the Fe-BCC phase, making it possible to obtain an Fe-based alloy that is less susceptible to cracking and is also expected to have high toughness and heat crack resistance.
• the second invention is an alloy member characterized in that it comprises at least a portion of the Fe-based alloy according to the first invention.
• the Fe-based alloy is formed on the surface of the base material of the alloy component, and it is desirable that the hardness of the surface layer is 350 HV or more.
• the second invention makes it possible to obtain an alloy component that is less susceptible to cracking and is also expected to have toughness and heat crack resistance.
• an alloy layer made of the Fe-based alloy according to the first invention on the surface of the base material, a member having excellent toughness and heat crack resistance on the surface can be obtained. Even if a part of the surface is damaged, for example, it can be easily repaired by forming an alloy layer again only on the damaged part by build-up, and an alloy member having excellent toughness and heat crack resistance can be obtained.
• the alloy member may have one or more of a nitride layer, a compound layer, or a ceramic coating layer on the surface of the Fe-based alloy.
• nitride layer a compound layer, or a ceramic coating layer on the surface, greater durability can be achieved.
• the third invention is a manufactured product characterized in that at least a part of it is made of the alloy member according to the second invention.
• the third invention makes it possible to obtain a product that is less susceptible to cracking and is also expected to have high toughness and heat crack resistance.
• Hot stamping dies, cold forging dies, and cold press dies that are repaired and used are particularly suitable as such products.
• the above Fe-based alloy parts and products can be obtained by additive manufacturing using metal powder of the desired composition.
• the fourth invention is a method for manufacturing an alloy member, which uses an alloy powder consisting of, by mass%, C 0.1% to 2%, Cr 2% to 6%, W 0.5% to 4%, Mo 0.5% to 4%, V 0.5% to 4%, Si 1.0% or less, Mn 1.0% or less, Co 4% or less, with the balance being Fe and unavoidable impurities, spraying the alloy powder while moving it onto a substrate, irradiating the sprayed alloy powder with an electron beam or laser beam to melt and solidify it to form a solidified layer, and repeating the melting and solidification process to obtain the alloy member.
• an alloy powder consisting of, by mass%, C 0.1% to 2%, Cr 2% to 6%, W 0.5% to 4%, Mo 0.5% to 4%, V 0.5% to 4%, Si 1.0% or less, Mn 1.0% or less, Co 4% or less, with the balance being Fe and unavoidable impurities
• the Si content is 0.1% or more and 1.0% or less
• the Mn content is 0.1% or more and 1.0% or less.
• the alloy powder further contains Co, and that the Co content is, by mass%, 0.5% to 4%.
• the obtained alloy part is subjected to at least one of a quenching treatment in which the part is held at 1000°C or more and 1400°C or less, and then cooled in oil or water, and a tempering treatment in which the part is held at 400°C or more and 700°C or less.
• the surface treatment step in which the obtained alloy component is subjected to a surface treatment, and the surface treatment step is a nitriding treatment or film formation by a PVD method.
• the fourth invention makes it possible to obtain a manufacturing method for alloy components that are less susceptible to cracking and are expected to have high toughness and heat crack resistance.
• the thickness of the solidified layer 0.1 mm or more and 5 mm or less.
• the present invention can provide an Fe-based alloy, an alloy member, and a method for manufacturing an alloy member that is unlikely to crack and is also expected to have high toughness and heat crack resistance.
• FIG. 1 illustrates a schematic configuration of an additive manufacturing method.
• 4 is a micrograph of a shaped body of an alloy member according to the present invention after quenching treatment.
• 2B is a structural photograph of the shaped body of FIG. 2A after tempering treatment.
• 4 is a microstructure photograph of a shaped body of an alloy member of the present invention before heat treatment.
• FIG. 2D is a structural photograph of the shaped body of FIG. 2C after tempering treatment. Photograph of the structure of conventional forged material after quenching and tempering.
• FIG. 11 is a diagram showing the Vickers hardness (HV) of each molded body.
• HV Vickers hardness
• % indicates mass %.
• a numerical range expressed using " ⁇ " means a range that includes the numerical values written before and after " ⁇ " as the lower limit and upper limit. Furthermore, the lower limit and upper limit of the numerical range can be appropriately combined.
• the Fe-based alloy of the present embodiment contains C, Cr, W, Mo, and V, with the balance being Fe and unavoidable impurity elements, in other words, it is a high-speed tool steel containing C, Cr, W, Mo, V, and Fe, and has an alloy structure including an Fe-BCC phase, the Fe-BCC phase containing, in mass %, 3% to 7% C, 2% to 6% Cr, 0.5% to 4% W, 0.5% to 4% Mo, 0.5% to 4% V, and 75% to 90% Fe, carbides precipitated in the Fe-BCC phase, and the carbides have an average circle-equivalent grain size of 1.3 ⁇ m or less.
• C 3-7%
• C combines with carbide-forming elements such as Cr, W, Mo, and V to form hard composite carbides, and has the effect of improving the wear resistance of alloy members and their products.
• C also has the effect of dissolving in a part of the matrix to strengthen the matrix.
• Cr Cr: 2 to 6%
• Cr combines with C to form carbides, improving wear resistance and contributing to improved hardenability.
• the Cr content in the Fe-BCC phase 2% or more the amount of carbides formed within the matrix grains can be optimized, and wear resistance and hardenability can be improved.
• the Cr content in the Fe-BCC phase 6% or less the amount of carbides formed within the matrix grains can be suppressed from becoming excessive, and toughness can be ensured.
• W 0.5-4%) W combines with C to form carbides, contributing to improved wear resistance. It also contributes to ensuring strength in high-temperature environments, and is therefore particularly effective in improving the wear resistance of dies used in high-temperature environments.
• W content in the Fe-BCC phase 0.5% or more, it dissolves in the matrix and increases the heat treatment hardness, improving the wear resistance.
• W content in the Fe-BCC phase 4% or less it is possible to suppress the formation of excessive carbides within the matrix grains, and ensure toughness.
• Mo 0.5 to 48%
• Mo combines with C to form carbides, improving wear resistance and contributing to improved hardenability.
• Mo content in the Fe-BCC phase 0.5% or more
• Mo dissolves in the matrix grains, increasing the heat treatment hardness, and thus improving wear resistance.
• the Mo content in the Fe-BCC phase 4% or less the amount of carbides formed in the matrix grains can be suppressed from becoming excessive, and toughness can be ensured.
• V 0.5 to 48%
• V combines with C to form carbides, contributing to improved wear resistance and seizure resistance.
• V content in the Fe-BCC phase 0.5% or more
• fine carbides that are difficult to aggregate are precipitated within the matrix grains by heat treatment, increasing softening resistance in high temperature ranges and improving high temperature yield strength.
• the matrix crystal grains are refined, improving toughness, and the A1 transformation point is raised, which, together with the excellent high temperature yield strength, improves heat crack resistance.
• V content in the Fe-BCC phase 4% or less it is possible to suppress the formation of excessive carbides within the matrix grains and ensure toughness.
• the Fe-BCC phase is generally a structure containing ⁇ -Fe and martensite formed when an Fe-based alloy is cooled from a high temperature.
• the Fe-BCC phase refers to a structure containing martensite of an Fe-based alloy in which C is supersaturated in solid solution, and is hard.
• the Fe-BCC phase contains 3% to 7% C, 2% to 6% Cr, 0.5% to 4% W, 0.5% to 4% Mo, 0.5% to 4% V, and 75% to 90% Fe.
• the Fe-BCC phase can be evaluated using electron backscattering diffraction (EBSD). The evaluation method using EBSD will be described later.
• carbides containing at least one of Cr, W, Mo, and V are precipitated.
• carbide-forming elements such as Cr, W, Mo, and V are combined with C (carbon) to form hard carbides, which is effective in improving wear resistance.
• C has the effect of strengthening the matrix by dissolving in a part of the matrix.
• a phase containing precipitated carbides can be called a carbide phase.
• Cr, V, Mo, and W are concentrated more than in the Fe-BCC phase, and it is a region with a large amount of C.
• the carbide phase contains, for example, 7% to 11% C, 3% to 7% Cr, 1% to 5% W, 1% to 5% Mo, 1% to 5% V, and 75% to 90% Fe.
• the size of the precipitated carbides is refined to an average circle-equivalent grain size of 1.30 ⁇ m or less. It is preferably 0.50 ⁇ m to 1.1 ⁇ m, and more preferably 0.60 ⁇ m to 1.1 ⁇ m.
• the average grain size can be determined from the carbides that are visible at a magnification of 400 times or more.
• the circle-equivalent average grain size of precipitated carbides in the Fe-BCC phase can be calculated as follows: First, the phase map obtained by EBSD (e.g., RGB image, field of view: 200 ⁇ 200 ⁇ m) is divided into each color (red, green, blue), and only the precipitated carbide portions are extracted.
• EBSD e.g., RGB image, field of view: 200 ⁇ 200 ⁇ m
• the phase map obtained by EBSD is divided into a red area (Fe-BCC phase), a blue area (mainly Fe-FCC phase), and a green area (area that is neither Fe-BCC phase nor Fe-FCC phase, hereafter referred to as the zero solution area).
• the phase map By dividing the phase map in this way, the proportion of the structure that is occupied by the Fe-BCC phase and precipitated carbides can be determined.
• the image of the divided red area (Fe-BCC phase) in black and white the Fe-BCC phase is displayed in white.
• the blue area (mainly Fe-FCC phase) and green area (zero solution area) are displayed in white. If the total area is the sum of the areas of the red area (Fe-BCC phase), blue area (mainly Fe-FCC phase), and zero solution area, the value obtained by dividing the red area (Fe-BCC phase) by the total area can be said to be the proportion (area ratio) of the Fe-BCC layer.
• the zero solution area can be displayed by subtracting the image of the divided blue area (mainly the Fe-FCC phase) from this black and white inverted image.
• This zero solution area is neither the Fe-BCC nor Fe-FCC phase, and corresponds to the precipitated carbide area.
• the average area of the precipitated carbide areas within the field of view is calculated, and the circle equivalent diameter of that area is calculated, making it possible to calculate the circle equivalent average grain size of the precipitated carbide within the Fe-BCC phase.
• Each structure can be evaluated using Energy-Dispersive X-ray Spectroscopy (EDS) and Electron Backscatter Diffraction (EBSD) in conjunction with a Scanning Electron Microscope (SEM).
• EDS Energy-Dispersive X-ray Spectroscopy
• EBSD Electron Backscatter Diffraction
• SEM Scanning Electron Microscope
• the analysis conditions may be, for example, a scanning electron microscope with an acceleration voltage of 15 kV, a working distance from the objective lens to the observation surface of 10 mm, and an observation magnification of 3000x.
• the element distribution evaluation method using EDS may obtain the element distribution by EDS surface analysis in the same field of view of the SEM as above.
• the target elements when analyzing precipitated carbides, the target elements may be, for example, C, Cr, W, Mo, V, Fe, Co, and O, and Si and Mn may also be added.
• the Fe-BCC phase can also be analyzed in the same manner as above.
• the proportion of the Fe-BCC phase the more uniform the metal structure becomes, and for example, localized distortion due to external stress is less likely to occur, which is expected to have the effect of suppressing cracks.
• the proportion of Fe-BCC is preferably 96% or more, more preferably 97% or more, even more preferably 98% or more, and even more preferably 99% or more.
• the structure of the Fe-based alloy of this embodiment is such that the Fe-BCC phase accounts for 96% or more of the alloy structure, and fine carbides are precipitated in the Fe-BCC phase, making it difficult for cracks to occur that originate from the carbides. Even if cracks do occur, they are uniformly dispersed and do not easily propagate. This makes it possible to improve toughness and heat crack resistance.
• the Fe-based alloy as a whole contains, in mass percent, 0.1%-2% C, 2%-6% Cr, 0.5%-4% W, 0.5%-4% Mo, 0.5%-4% V, 1.0% or less Si, 1.0% or less Mn, 4% or less Co, and the remainder is Fe and unavoidable impurity elements.
• C 0.1 to 2%)
• C combines with carbide-forming elements such as Cr, W, Mo, and V to form hard composite carbides, which improves the wear resistance of alloy members and their products.
• C also has the effect of dissolving in a part of the matrix to strengthen the matrix.
• Cr Cr: 2 to 6%
• Cr combines with C to form carbides, improving wear resistance and hardenability.
• the Cr content in the entire Fe-based alloy 2% or more, the amount of carbides formed in the entire Fe-based alloy can be optimized, and wear resistance and hardenability can be improved.
• the Cr content in the entire Fe-based alloy 6% or less the amount of carbides formed in the entire Fe-based alloy can be suppressed from becoming excessive, and toughness can be ensured.
• W 0.5-4%) W combines with C to form carbides, contributing to improved wear resistance. It also contributes to ensuring strength in high-temperature environments, so it is particularly effective in improving the wear resistance of dies used in high-temperature environments.
• W content in the entire Fe-based alloy 0.5% or more, it dissolves in the grains of the matrix, increasing the heat treatment hardness, and carbides are also formed at the grain boundaries of the matrix, improving wear resistance.
• W content in the entire Fe-based alloy 4% or less it is possible to suppress the formation of excessive carbides in the entire Fe-based alloy, and to ensure toughness.
• Mo 0.5 to 48%
• Mo combines with C to form carbides, improving wear resistance and contributing to improved hardenability.
• Mo 0.5% or more in the entire Fe-based alloy Mo dissolves in the matrix grains, increasing the heat treatment hardness, and carbides are also formed in the grain boundaries of the matrix, improving wear resistance.
• Mo 4% or less in the entire Fe-based alloy the amount of carbides formed in the entire Fe-based alloy can be suppressed from becoming excessive, and toughness can be ensured.
• V 0.5 to 48%
• V combines with C to form carbides, contributing to improved wear resistance and seizure resistance.
• V content in the entire Fe-based alloy 0.5% or more, fine carbides that are difficult to aggregate are precipitated in the grains of the matrix by heat treatment, and the softening resistance in the high temperature range increases, and high temperature yield strength increases.
• the crystal grains of the matrix are refined, the toughness improves, and the A1 transformation point increases, and together with the excellent high temperature yield strength, the heat crack resistance improves.
• the V content in the entire Fe-based alloy 4% or less the amount of carbides formed in the entire Fe-based alloy can be suppressed from becoming excessive, and toughness can be ensured.
• the alloy further contains either Si or Mn, or both, with Si being 0.1% to 1.0% by mass, and Mn being 0.1% to 1.0% by mass.
• Si is expected to improve oxidation resistance. It is preferable to set the above range in consideration of workability.
• Mn is expected to improve wear resistance and hardenability, and reduce embrittlement. It is preferable to set the above range in consideration of the effects of embrittlement due to quench cracking and residual ⁇ .
• Si 1.0% or less
• Si may be contained.
• the content of Si in the entire Fe-based alloy is preferably 0.1% or more and 1.0% or less in order to improve oxidation resistance and suppress deterioration of workability.
• Mn 1.0% or less
• Mn may be contained.
• the content of Mn in the entire Fe-based alloy is preferably 0.1% or more and 1.0% or less in order to improve wear resistance and hardenability, reduce embrittlement, and suppress embrittlement due to quench cracking and residual ⁇ .
• Co (Co: 4.0% or less)
• Co may be contained.
• the content of Co in the entire Fe-based alloy is preferably 4.0% or less, and more preferably 0.5% or more and 4% or less.
• the inevitable impurities are trace elements mixed into the raw materials, or impurities in trace amounts that are difficult to remove technically due to reactions with various components that come into contact during the manufacturing process.
• the inevitable impurities specifically refer to, for example, Al, Cu, N, Ni, O, P, S, and Ti.
• the impurities that should be particularly restricted are P, S, O, and N.
• P is preferably 0.03% or less
• S is preferably 0.003% or less
• O is preferably 0.02% or less
• N is preferably 0.05% or less.
• the content of these inevitable impurities is preferably low, and 0% is even better.
• the Fe-based alloy and alloy member of this embodiment can be obtained by spraying alloy powder onto a substrate while moving it, irradiating the sprayed alloy powder with an electron beam or laser beam to melt and solidify it to form a solidified layer, stacking another solidified layer on the solidified layer, and repeating this process. It is manufactured by a so-called additive manufacturing method. In this specification, it may be referred to as a layered manufacturing method.
• the alloy powder is an Fe-based alloy powder containing the above-mentioned predetermined composition of C, Cr, W, Mo, and V, with the balance being Fe and inevitable impurity elements.
• a predetermined amount of each element is weighed so as to obtain an alloy having a predetermined composition range, and these are mixed to prepare a raw material powder.
• This raw material powder is used to obtain an atomized powder.
• the raw material powder is loaded into a crucible, melted by high frequency, and the molten alloy is dropped from a nozzle below the crucible and sprayed with high pressure argon to prepare a gas atomized powder. This gas atomized powder can be classified to obtain an alloy powder.
• the Fe-based alloy powder of this embodiment may be alloyed to satisfy the above-mentioned composition of the Fe-based alloy.
• the powder contains, by mass, 0.1% to 2% C, 2% to 6% Cr, 0.5% to 4% W, 0.5% to 4% Mo, 0.5% to 4% V, 4.0% or less Co, 1.0% or less Si, and 1.0% or less Mn, with the remainder being Fe and unavoidable impurities.
• C in the alloy structure of the shaped body combines with carbide-forming elements such as Cr, W, Mo, and V to form hard composite carbides, which has the effect of improving the wear resistance of the alloy member and its manufactured products.
• C has the effect of dissolving in part of the matrix of the alloy structure of the shaped body, thereby strengthening the matrix.
• the hardness of the alloy structure can be ensured by the effects of strengthening the matrix of the alloy structure, fine carbides formed within the grains of the matrix, and carbides formed at the grain boundaries of the matrix.
• the C content in the Fe-based alloy powder 2% or less the formation of excessive carbides in the alloy structure can be suppressed, and the toughness of the Fe-based alloy as a whole can be ensured.
• Cr combines with C to form carbides, improving the wear resistance of the alloy structure of the molded body and also contributing to improved hardenability.
• the Cr content in the Fe-based alloy powder 2% or more, the amount of carbides formed in the alloy structure of the molded body can be optimized, improving the wear resistance and hardenability of the alloy structure.
• the Cr content in the entire Fe-based alloy 6% or less the amount of carbides formed in the alloy structure of the molded body can be prevented from becoming excessive, ensuring toughness.
• W combines with C to form carbides, which contributes to improving the wear resistance of the alloy structure of the molded body. It also contributes to ensuring strength in high-temperature environments, so it is particularly effective in improving the wear resistance of dies used in high-temperature environments.
• the W content in the Fe-based alloy powder 0.5% or more, it dissolves in the grains of the matrix in the alloy structure, increasing the heat treatment hardness, and carbides are also formed at the grain boundaries of the matrix, improving the wear resistance of the alloy structure.
• the W content in the Fe-based alloy powder 4% or less it is possible to prevent the formation of excessive carbides in the alloy structure and ensure toughness.
• Mo combines with C to form carbides, improving the wear resistance of the alloy structure of the molded body and also contributing to improved hardenability.
• Mo content in the Fe-based alloy powder 0.5% or more, it dissolves in the grains of the matrix in the alloy structure, increasing the heat treatment hardness, and carbides are also formed at the grain boundaries of the matrix, improving the wear resistance of the alloy structure.
• Mo content in the Fe-based alloy powder 4% or less it is possible to prevent the formation of excessive carbides in the alloy structure and ensure toughness.
• V combines with C to form carbides, which contributes to improving the wear resistance and seizure resistance of the alloy structure of the molded body.
• V content in the Fe-based alloy powder 0.5% or more, fine carbides that are difficult to aggregate are precipitated within the grains of the matrix in the alloy structure by heat treatment, increasing the softening resistance of the alloy structure in the high temperature range and increasing the high temperature strength.
• the crystal grains of the matrix in the alloy structure are refined, improving toughness, and the A1 transformation point is raised, which, combined with the excellent high temperature strength, improves heat crack resistance.
• the V content in the Fe-based alloy powder 4% or less it is possible to suppress the formation of excessive carbides in the alloy structure and ensure toughness.
• an Fe-based alloy powder can be used that contains, by mass%, 0.1% to 2% C, 0.1% to 1.0% Si, 0.1% to 1.0% Mn, 2% to 6% Cr, 0.5% to 4% W, 0.5% to 4% Mo, 0.5% to 4% V, and the remainder Fe and unavoidable impurity elements. It is also preferable that the powder contains either Si or Mn, or both.
• the content in the Fe-based alloy powder is preferably 0.1% to 1.0% in order to improve the oxidation resistance of the alloy structure of the molded body and suppress a decrease in workability. If the Fe-based alloy powder contains Mn, the content in the Fe-based alloy powder is preferably 0.1% to 1.0% in order to improve the wear resistance and hardenability of the alloy structure of the molded body, reduce embrittlement, and suppress embrittlement due to quench cracking and residual ⁇ .
• Co can be included.
• the content in the Fe-based alloy as a whole is preferably 4% or less.
• an Fe-based alloy powder containing 0.1% to 2% C, 0.1% to 1.0% Si, 0.1% to 1.0% Mn, 2% to 6% Cr, 0.5% to 4% W, 0.5% to 4% Mo, 0.5% to 4% V, 0.5% to 4% Co, with the remainder being Fe and unavoidable impurity elements.
• the composition of the alloy powder can be analyzed, for example, using inductively coupled plasma (ICP) optical emission spectrometry.
• ICP inductively coupled plasma
• the Fe-based alloy member of this embodiment can be manufactured by repeating the melting and solidifying process of irradiating the Fe-based alloy powder with a heat source such as an electron beam or laser beam to melt and solidify it and form a solidified layer, thereby stacking further solidified layers on the solidified layer.
• the directed energy deposition method can spray the alloy powder while moving it onto a substrate, irradiate the sprayed alloy powder with an electron beam or laser beam to melt and solidify it and form a solidified layer, and repeat the melting and solidifying process to stack further solidified layers on the solidified layer, thereby obtaining the alloy member (shaped body) of this embodiment.
• powder particle size may be adjusted by mesh sieving or airflow classification to match the modeling method of the additive manufacturing method.
• the modeling powder used in powder bed fusion methods using electron beams or laser beams is melted by the laser beam, which serves as the heat source, but coarse powder that is difficult to melt must be removed to minimize the range of thermal effects.
• highly adhesive fine powder must also be removed.
• the average particle size (D50) of the alloy powder when applying to the Powder Bed Fusion (PBF) method, it is preferable to adjust the average particle size (D50) of the alloy powder to the range of 10 to 53 ⁇ m.
• metal powders used in the directed energy deposition method need to have coarse powders that are difficult to melt removed in order to melt the powder using a laser beam as a heat source.
• fine powders need to be removed in order to prevent dust scattering when the powder is supplied to the heat source and to ensure fluidity that allows the powder to be easily transported.
• Figure 1 shows the schematic configuration of an additive manufacturing device 1 that uses a laser beam as a heat source for additive manufacturing using the directed energy deposition method.
• the additive manufacturing device 1 is mainly composed of a powder supply nozzle 3, a focusing lens 5, a protective lens 7, etc. Alloy powder 11 is supplied to the powder supply nozzle 3 and sprayed onto the tip of the powder supply nozzle 3 together with argon gas.
• a laser beam 9 emitted from a laser oscillator (not shown) is focused by the focusing lens 5 and irradiated near the tip of the powder supply nozzle 3.
• a protective lens 7 is provided below the focusing lens 5.
• alloy powder 11 is supplied onto the base plate 17 while the powder supply nozzle 3 is moved relative to the base plate 17 (direction A in the figure).
• the supplied alloy powder 11 is irradiated with a laser beam 9 focused by a focusing lens 5, forming a molten pool in which the alloy powder 11 melts and solidifies to form a shaped body 15 (Fe-based alloy).
• This process is repeated using a program file created using CAD-CAM software to stack the shaped bodies 15 on the base plate 17, thereby forming a three-dimensional alloy part that contains at least a portion of an Fe-based alloy.
• a three-dimensional additive manufacturing device is used to rapidly melt the surface of a base material such as a base plate, a molded body, or a die by irradiating it with a laser, and raw material powder is supplied into the molten pool that is formed by the melting, where it is rapidly cooled and solidified. A series of processes are repeated and layered to create a molded body.
• the molded body formed on the base plate is the Fe-based alloy component of this embodiment. In the case of repairing a die, a manufactured product can be obtained.
• the additive manufacturing conditions are appropriately determined taking into consideration the particle size and composition of the raw material powder, the size, shape, and characteristics of the molded body, production efficiency, etc., and for the alloy of this embodiment, they can be selected, for example, from the following ranges.
• the thickness of one layer during additive manufacturing is, for example, 0.1 mm to 1.0 mm, and preferably 0.4 to 0.8 mm.
• the thickness of the first layer of Fe-based alloy formed on the surface of the base plate is 0.1 mm to 1 mm.
• the thickness of the entire layer from the interface of the base material to the surface of the Fe-based alloy is preferably 0.1 mm to 5 mm to prevent peeling of the Fe-based alloy from the base material and cracking of the Fe-based alloy itself.
• the dilution layer refers to a layer that dissolves with the base material when the Fe-based alloy is shaped, and in which the compositions of both the base material and the first layer of Fe-based alloy are mixed.
• the laser beam diameter is preferably about 3 mm at the irradiation position.
• the laser output is preferably 1500 to 2500 W.
• the laser scanning speed is preferably 200 to 2000 mm/min, and more preferably 500 to 1000 mm/min.
• the powder supply amount is preferably 10 to 20 g/min.
• the density of the energy input by laser irradiation to melt the raw material powder is preferably 90 to 300 J/mm, and more preferably 180 to 240 J/mm. If the energy density is too small, the defect rate will increase, and the supplied powder will be difficult to melt, making it difficult to maintain the shape of the molded object. On the other hand, if the energy density is too large, the base plate or the molded object itself will melt over a wide area centered on the laser irradiation position, making it difficult to maintain the shape of the molded object.
• the Fe-based alloy of this embodiment may be subjected to quenching treatment to improve hardness after molding, and may be subjected to additional tempering treatment to remove quenching stress and improve toughness if the cost and the like are within an acceptable range.
• the holding temperature can be 1000 to 1400 ° C, more preferably 1100 to 1300 ° C, and even more preferably 1150 to 1280 ° C.
• the holding time can be 0.1 to 5 hours, more preferably 0.1 to 2 hours. Cooling can be performed in oil or water, but cooling in oil is more preferable to prevent distortion and quench cracking. Quenching and cooling using a salt bath may also be performed.
• the temperature should be held at 400°C to 700°C, preferably 560°C to 580°C.
• the holding time should be 1 to 10 hours, preferably 2 to 6 hours. Cooling is preferably done by air cooling.
• quenching promotes the decomposition of carbides present in the molded body, and carbon that bonds with carbide-forming elements such as Fe, W, Mo, and V is more likely to diffuse into the Fe-BCC phase, making it easier for precipitated carbides to form.
• carbide-forming elements such as Fe, W, Mo, and V
• alloys that have been quenched have a higher proportion of precipitated carbides than alloys that have not been quenched. It can also be assumed that the diffusion of carbon disperses the precipitated carbides, reducing the average circle-equivalent particle size of the precipitated carbides.
• the hardness of the surface layer of the Fe-based alloy or alloy member of this embodiment can be evaluated by Vickers hardness HV (hereinafter referred to as hardness), and is desirably 350 HV or more, and preferably 500 HV or more.
• the hardness can be measured by setting the pressing load of a Vickers indenter to 0.5 kg, the dwell time during pressing to 10 seconds, and determining the hardness from the diagonal length of the indentation formed on the measurement surface by pressing the indenter.
• the method may further include a surface treatment step in which the obtained alloy component is subjected to a surface treatment.
• the surface treatment step is, for example, a nitriding treatment or film formation by a PVD method on the surface layer of the Fe-based alloy, and is a nitride layer, a compound layer, or a ceramic coating layer.
• a coating that is harder than the Fe-based alloy formed by additive manufacturing can be formed on the surface layer of the Fe-based alloy, and therefore the wear resistance can be improved by further strengthening the surface of the alloy component obtained by additive manufacturing.
• the product having at least a part of the alloy member thus obtained is not particularly limited, but is particularly suitable for hot stamping dies, cold forging dies, and cold press dies.
• the damaged part can be easily repaired by forming the alloy layer of the present invention by build-up only.
• the die repaired with the Fe-based alloy according to this embodiment is less likely to crack and has excellent toughness and heat crack resistance.
• the raw materials of each element shown in Table 1 were weighed out in predetermined amounts, mixed, loaded into a crucible, and melted using high frequency in a vacuum.
• the molten alloy was dropped from a nozzle below the crucible and sprayed with high pressure argon to produce gas atomized powder.
• This gas atomized powder was classified to obtain Fe-based alloy powder with a particle size of 53 to 106 ⁇ m.
• the composition of the obtained Fe-based alloy powder is shown in Table 1, and its particle size distribution in Table 2.
• the raw material powder was fed into a molten pool formed by laser irradiation on the base plate, and was rapidly melted and rapidly solidified to create a shaped object with a width of 3 mm, length of 80 mm, and a layer height of approximately 10 mm.
• the additive manufacturing conditions were as follows: For the base plate, maraging steel (YAG300 manufactured by Proterial (YAG is a registered trademark of Proterial Co., Ltd.) was used.
• the molded bodies were evaluated by heat-treating and not heat-treating.
• the molded body that was only quenched was designated F1
• the molded body that was quenched and tempered was designated F2
• the molded body that was not heat-treated was designated F3
• the molded body that was only tempered was designated F4.
• the quenching process involved holding the molded body at 1200°C for 0.5 hours, followed by cooling in oil.
• the tempering process involved holding the molded body at 560°C for 4 hours, followed by air cooling.
• the molded bodies F1 and F2 were observed and evaluated using a SEM.
• the test pieces for evaluation were prepared by cutting a portion of the molded body into small pieces and embedding them in resin, and then polishing the cut surface of the embedded molded body to a mirror finish. The observation was performed at a magnification of 3000x. Eight elements were analyzed: C, Co, Cr, Fe, Mo, V, W, and O.
• Figures 2A to 2E show examples of acquired SEM images.
• Figure 2A is an SEM image of a shaped body F1 that was only subjected to quenching as a heat treatment
• Figure 2B is an SEM image of a shaped body F2 that was subjected to quenching and tempering treatments.
• Figure 2C is an SEM image of a shaped body F3 that was not subjected to heat treatment (no heat treatment)
• Figure 2D is an SEM image of a shaped body F4 that was only subjected to tempering treatment
• Figure 2E is an SEM image of a forged material F0 (powder sintered, forged, and heat treated (quenching and tempering)) made by a conventional powder metallurgy method, which is an alloy of the same composition.
• the structure shown in shades of gray can be confirmed.
• a phase map was obtained using the method described above, and elemental analysis was then carried out within the field of view.
• the area of the field of view (also called the field of view area) was 200 ⁇ m x 200 ⁇ m.
• Table 3 shows the compositions of the Fe-BCC phase and carbides of F2, which was quenched and tempered.
• the Fe-BCC phase was analyzed at the position A in FIG. 2B, and the precipitated carbides (sometimes simply referred to as carbides) were analyzed at the position B in FIG. 2B.
• Table 4 shows the results of analyzing the position C in FIG. 2C for the Fe-BCC phase of F3, which was not heat-treated (no heat treatment).
• the Fe-BCC phase was analyzed at the position D in FIG. 2E, and the carbides were analyzed at the position E in FIG. 2E. The results are shown in Table 5.
• both the Fe-BCC phase and the carbides contained mainly Fe.
• the C, Cr, W, Mo, V and Co in the Fe-BCC phase were 5.0% C, 4.2% Cr, 1.8% W, 2.1% Mo, 1.1% V, 1.3% Co and 84.5% Fe, with the C being in the range of 3%-7%, 2%-6% Cr, 0.5%-4%, 0.5%-4% Mo, 0.5%-4% V and 75%-90% Fe.
• the carbides were 8.9% C, 4.8% Cr, 2.5% W, 3.3% Mo, 2.5% V and 78.1% Fe.
• the electron diffraction pattern generated during electron beam irradiation was measured using EBSD, and it was determined that the Fe-BCC phase has a BCC structure.
• the C, Cr, W, Mo, V and Co in the Fe-BCC phase for F3 were 4.9% C, 4.2% Cr, 1.9% W, 2.2% Mo, 1.2% V, 1.3% Co and 84.5% Fe, with the ranges of 3%-7% C, 2%-6% Cr, 0.5%-4% W, 0.5%-4% Mo, 0.5%-4% V and 75%-90% Fe.
• Carbides could not be analyzed because the area they occupied was small and below the resolution of the analyzer.
• the proportion of the Fe-BCC phase was 96.0% or more for all of F1 to F4, 99.4% for F1, which was subjected to only quenching treatment, 99.5% for F2, which was subjected to both quenching and tempering treatment, 99.8% for F3, which was not subjected to quenching or tempering treatment (no heat treatment), and 99.9% for F4, which was subjected to only tempering treatment.
• the proportion of precipitated carbides in the formed bodies F1 to F4 was 0.27% for F1 and 0.38% for F2, confirming that the precipitated carbides were moderately precipitated within the Fe-BCC phase.
• the proportion of precipitated carbides in F3 and F4 was 0.012% and 0.009%, respectively, confirming that the proportion of precipitated carbides in the Fe-BCC phase was smaller than that of F1 and F2.
• the circle-equivalent average particle size of the precipitated carbides was 1.08 ⁇ m for F1 and F2, confirming that they were refined. In addition, it was 0.58 ⁇ m for F3 and 0.50 ⁇ m for F4, confirming that the precipitated carbides were also refined for F3 and F4.
• F1 and F2 which were produced using additive manufacturing methods as in this example, have a faster cooling rate than the precipitation rate of precipitated carbides, because the alloy powder melts and is immediately cooled and solidified.
• the holding time in the temperature range in which precipitated carbides can form is shorter due to the faster cooling rate, and the amount of carbides formed inside the alloy (shaped body) in the pre-heat treatment state is smaller to begin with, compared to F0.
• the circular equivalent average particle size of the precipitated carbides in the shaped bodies F1 to F4 is small, the precipitated carbides are finely divided, which makes the Fe-based alloy less susceptible to cracking and has excellent toughness and heat crack resistance.
• the circular equivalent average particle size of the precipitated carbides in the shaped bodies F1 and F2 is 1.08 ⁇ m, and the precipitated carbides are appropriately finely divided, which makes the Fe-based alloy more susceptible to wear.
• the proportion of the Fe-BCC phase in the forged material F0 is 95.7%
• the proportion of the Fe-BCC phase in the shaped bodies F1 to F4 is over 99%, making the structure more uniform. Therefore, for example, it can be expected that cracks will be less likely to occur because local distortion due to external stress will be less likely to occur.
• the proportion of the Fe-BCC phase is 99% or more, so the structure is uniform. Therefore, for example, it is expected that cracks will not easily occur because local distortion due to external stress is unlikely to occur.
• the shaped body F1 that was subjected to only quenching and the shaped body F2 that was subjected to quenching and tempering have a moderately fine circle-equivalent average particle size of 1.08 ⁇ m for the precipitated carbides, so that cracks are unlikely to occur, and it is expected that they will have excellent toughness, heat crack resistance, and wear resistance.

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