Fe-based alloy powder for additive manufacturing and additive manufactured object

Abstract

To provide an Fe-based alloy powder for laminate molding which has excellent crack resistance and mold performance by further improving thermal conductivity of a maraging steel.SOLUTION: An Fe-based alloy powder for laminate molding is formed of an Fe-based alloy that includes, by mass% and as essential components, 10.0 to 16.0% of Ni, 6.0% or less of Mo, 0.5 to 2.5% of Ti, 0.01 to 1.0% of Al, 0.8% or less of Si, and 0.8% or less of Mn, and further includes, as optional additional components, 6.0% or less of Cr and other elements, with the balance being Fe and unavoidable impurities, wherein a value of M1 in formula (1): M1=Ni+0.8Cr+0.6Mo-0.3Ti is 13.0 or more, and a value of M2 in formula (2): M2=41.9-0.9Ni-2.0Mo-2.1Cr is 17.0 or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to Fe-based alloy powders suitable for processes for generating shaped bodies such as three-dimensional additive manufacturing methods, thermal spraying methods, laser coating methods, build-up welding methods, and hot isostatic pressing methods.

Background Art

[0002] 3D printers have begun to be used for manufacturing shaped objects made of metal. This 3D printer manufactures shaped objects by an additive manufacturing method. Representative methods of the metal additive manufacturing method include a powder bed method (powder bed fusion method) and a metal deposition method (directed energy deposition method). In the powder bed method, the irradiated part of the spread powder melts and solidifies by irradiation with a laser beam or an electron beam. By this melting and solidification, the powder particles are bonded to each other. The irradiation is selectively performed on a part of the metal powder, and the part where the irradiation is not performed does not melt, and a bonding layer is formed only in the part where the irradiation is performed.

[0003] On the formed bonding layer, new metal powder is further spread, and the metal powder is irradiated with a laser beam or an electron beam. Then, by the irradiation, the metal particles melt and solidify, and a new bonding layer is formed. Also, the new bonding layer is bonded to the existing bonding layer.

[0004] By sequentially repeating the melting and solidification by irradiation, the aggregate of the bonding layers gradually grows. By this growth, a shaped body having a three-dimensional shape is obtained. When such an additive manufacturing method is used, a shaped object having a complex shape can be easily obtained.

[0005] For example, as a powder bed type additive manufacturing method, a mixture of "iron-based powder" and "one or more powders selected from the group consisting of nickel, nickel-based alloys, copper, copper-based alloys, and graphite" is used as a metal powder for metal stereolithography. A powder layer forming step of laying these metal powders, a sintered layer forming step of irradiating the powder layer with a beam to form a sintered layer, and a removal step of cutting the surface of the shaped object are repeated to form a sintered layer, and a procedure for manufacturing a three-dimensional shaped object is disclosed (see Patent Document 1).

[0006] When using metal additive manufacturing to create an aluminum die-casting mold, generally maraging steel and SKD61 series die steels are used. And general maraging steel does not substantially contain C and contains alloying elements such as Ni, Mo, Ti, Co, etc. (see Patent Documents 2 to 4).

[0007] The applicant of the present application has proposed an Fe-based metal powder for shaping composed of Ni: 15.0 to 21.0%, Co: 0.5% or less, Mo: 7.0% or less, Ti: 0.1 to 6.0%, Al: 0.1 to 3.0%, and the balance Fe and unavoidable impurities (see Patent Document 2).

[0008] Also, an alloy powder for additive manufacturing with a median diameter D50 of 200 μm or less and composed of maraging steel with Fe as the main component, Ni: 14 to 22%, Co: 0 to 5%, Mo: 0.1 to 15%, Ti: 0.1 to 5%, Al: 3% or less, and the balance Fe and unavoidable impurities has been proposed (see Patent Document 3).

[0009] Also, a metal powder material for metal additive manufacturing of a steel material equivalent to maraging steel formed by mixing powders of a plurality of alloys having components of Fe: 76% or more, C: 0.03% or less, Si: 0.12% or less, Mn: 0.12% or less, Ni: 17 to 19%, Mo: 1.5 to 2.5%, Ti: 0.5 to 2.0, and Al: 1.08 to 1.5% has been proposed (see Patent Document 4).

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0011] When creating an aluminum die-cast mold using metal additive manufacturing, conventionally, maraging steel and SKD61 series die steels have been used as the materials. In such metal additive manufacturing materials for aluminum die-cast molds, excellent thermal conductivity is required to improve the mold cooling efficiency, and crack resistance during additive manufacturing is required.

[0012] However, SKD61 series die steels are excellent in thermal conductivity but are prone to forming cracks due to the influence of thermal stress. On the other hand, maraging steel is soft during forming and thus less prone to forming cracks. However, on the other hand, because it contains many alloying elements, its thermal conductivity is low, and the performance when used as a mold is likely to be lower than that of conventional die steels.

[0013] Therefore, the problem to be solved by the present invention is to provide an Fe-based alloy powder for additive manufacturing that is excellent in crack resistance (high toughness) and mold performance by further improving the thermal conductivity of maraging steel.

Means for Solving the Problems

[0014] As a result of intensive studies, the inventors have found that it is useful to define the composition of maraging steel and satisfy the value of M1 in the hardenability index formula (1) and the value of M2 in the thermal conductivity index formula (2). That is, by satisfying M1 = Ni + 0.8Cr + 0.6Mo - 0.3Ti ≧ 13.0, a martensite structure can be obtained during shaping, and by satisfying M2 = 41.9 - 0.9Ni - 2.0Mo - 2.1Cr ≧ 17.0, it has been found that the thermal conductivity can be increased.

[0015] For the general-purpose maraging steel of the melted material (representative composition: Fe-18.5%Ni-9%Co-5%Mo-0.6%Ti-0.1%Al), a large amount of alloying elements are added to ensure hardenability so that it transforms into martensite by air cooling after solution treatment. The values of the indexes in the present invention for the general-purpose maraging steel are M1: 21.3 and M2: 15.3. That is, in the general-purpose maraging steel, while the value of M1 is significantly higher than that of the examples of the present invention, the value of M2, which is the thermal conductivity index, is less than 17.0. The general-purpose maraging steel has a different component system from the examples of the present invention, and the general-purpose maraging steel has insufficient thermal conductivity.

[0016] Therefore, the inventors have noted that the cooling rate during rapid solidification in metal additive manufacturing is faster than quenching in the conventional process, and have found that a martensite structure can be obtained in additive manufacturing even with the addition of a smaller amount of alloying elements (M1 ≧ 13.0) compared to general-purpose maraging steel. And since the amount of alloying elements can be reduced compared to general-purpose maraging steel, it was conceived that a higher thermal conductivity than that of general-purpose maraging steel could be obtained. Also, it has been found that those with a larger full width at half maximum (FWHM) of the X-ray diffraction peak and a higher dislocation density are more excellent in toughness.

[0017] That is, the first means for solving the problems of the present invention is an Fe-based alloy composed of, by mass%, as essential components, Ni: 10.0 to 16.0%, Mo: 0.1 to 5.0%, Ti: 0.5 to 2.5%, Al: 0.01 to 1.0%, Si: 0.8% or less, Mn: 0.8% or less, with the balance being Fe and unavoidable impurities, and the value of M1 in formula (1) is 13.0 or more, and the value of M2 in formula (2) is 17.0 or more, which is an Fe-based alloy powder for laminated manufacturing. M1 = Ni + 0.8Cr + 0.6Mo - 0.3Ti ··· Formula (1) M2 = 41.9 - 0.9Ni - 2.0Mo - 2.1Cr ··· Formula (2) However, for the element symbols in formula (1) and formula (2), substitute the mass% values of the corresponding components.

[0018] The second means is an Fe-based alloy composed of, in addition to the components described in the first means, one or more selected from the group consisting of Cr: 6.00% or less, C: 0.01 to 0.10%, Co: 0.01 to 0.90%, Nb: 0.01 to 2.00% as optional additional components, with the balance being Fe and unavoidable impurities, and the value of M1 in formula (1) is 13.0 or more, and the value of M2 in formula (2) is 17.0 or more, which is an Fe-based alloy powder for laminated manufacturing. Formulas (1) and (2) are the same as those in the first means.

[0019] The third means is a laminated manufactured object laminated and manufactured using the Fe-based alloy powder described in either the first or second means.

[0020] The fourth means is the laminated manufactured object described in the third means, in which the full width at half maximum of the peak of the (110) plane of bcc iron in the X-ray diffraction pattern using CuKα rays is 0.140 degrees or more in terms of 2θ.

Advantages of the Invention

[0021] When performing metal laminated manufacturing using the Fe-based alloy powder of the means described in the present invention, a laminated manufactured object can be appropriately obtained, with a thermal conductivity of 17.0 W / m / K or more and 20.0 J / cm 2It is possible to obtain a laminated object made of mold steel having the above Charpy impact value and having high thermal conductivity and high toughness.

[0022] Further, if the value of FWHM of the present invention is 0.140 degrees or more, 20.0 J / cm 2 or more of the Charpy impact value can be obtained and the toughness can be improved. If it is 0.145 degrees or more, 25.0 J / cm 2 or more. If it is 0.150 degrees or more, 30.0 J / cm 2 or more. If it is 0.153 degrees or more, 35.0 J / cm 2 It is possible to obtain a laminated object made of mold steel having higher toughness and high thermal conductivity, such as having a Charpy impact value of 35.0 J / cm or more.

Brief Description of Drawings

[0023]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0024] Prior to the description of the embodiments of the present invention, first, the reasons for defining the components and characteristics of the Fe-based alloy powder of the present invention will be described below. In addition, % in each component is mass%. The balance is Fe and inevitable impurities. The indexes defined in formula (1) and formula (2) will also be described.

[0025] Ni: 10.0 to 16.0% Ni forms intermetallic compounds with Mo, Ti, and Al and is a component for obtaining a shaped article having excellent strength. Also, Ni is an element necessary for forming martensite in order to improve hardenability. From this perspective, Ni is preferably 10.0% or more, more preferably 12.0% or more, and particularly preferably 13.0% or more. However, since Ni is an element that forms an austenite phase, if Ni is added in excess, the martensite transformation is suppressed and it becomes difficult to form the martensite phase. Also, as the amount of the alloying element Ni increases, the thermal conductivity decreases. Therefore, from these perspectives, the content of Ni is set to 16.0% or less. Further, Ni is preferably 15.5% or less, and particularly preferably 14.9% or less.

[0026] Mo: 0.1 - 5.0% Mo forms an intermetallic compound with Fe and is a component for ensuring strength. Also, Mo is a component for forming martensite in order to improve hardenability. Mo is preferably 1.0% or more, more preferably 1.5% or more, and particularly preferably 1.9% or more. However, if Mo is added in excess, the thermal conductivity decreases. From this perspective, Mo is set to 5.0% or less, preferably 4.5% or less, and more preferably 4.0% or less.

[0027] Al: 0.01 - 1.0% Al forms an intermetallic compound with Ni and is a component for obtaining a shaped article having excellent strength and oxidation resistance. From this perspective, the content of Al is preferably 0.01% or more, more preferably 0.1% or more, and particularly preferably 0.5% or more. However, if Al is added in excess, hot cracking is likely to occur in the rapid melting and rapid solidification process. From this perspective, the content of Al is set to 1.0% or less, and preferably 0.8% or less.

[0028] Ti: 0.5 - 2.5% Ti forms an intermetallic compound with Ni and is a component for obtaining a shaped article with excellent strength. From this perspective, the Ti content is preferably 1.0% or more, more preferably 1.3% or more. However, when a large amount of Ti is added, the formation of martensite is suppressed and the formation of bainite is promoted. From this perspective, the Ti content is preferably 2.0% or less.

[0029] Si: 0.8% or less Si is a component that improves hardness by dissolving in the matrix. Also, Si has the effect of improving the softening resistance. However, if the Si content becomes too high, it causes a decrease in thermal conductivity. Therefore, Si is set to 0.8% or less. Si is preferably 0.4% or less, more preferably 0.1% or less, and particularly preferably 0.03% or less.

[0030] Mn: 0.8% or less Mn is a component that improves hardenability and suppresses the decrease in toughness due to the formation of bainite. Also, Mn has the effect of improving the softening resistance. If the Mn content becomes too high, Mn dissolves in the matrix and decreases the thermal conductivity of the shaped article. Therefore, Mn is set to 0.80% or less. The Mn content is preferably 0.4% or less, more preferably 0.1% or less, and particularly preferably 0.03% or less.

[0031] In addition to these constituent elements, the Fe-based alloy powder according to the present invention may contain any one or more of Cr, C, Co, and Nb as additional components.

[0032] Cr: 0 to 6.00% In addition, Cr is a component useful for forming martensite in order to improve hardenability. In the present invention, Cr may be 0% as an optional component, but from this viewpoint, Cr is preferably 0.10% or more, and more preferably 0.30% or more. However, since Cr is an element that forms an austenite phase, if a large amount of Cr is added, the martensite transformation is suppressed and it becomes difficult to form a martensite phase. In addition, when the amount of alloying elements increases, the thermal conductivity decreases. From this viewpoint, the Cr content is set to 6.00% or less, preferably 4.00% or less, more preferably 3.00% or less, and even more preferably 2.00% or less.

[0033] Co: 0.01 - 0.90% Co is a component that forms an austenite phase. Therefore, when the Co content is high, it becomes difficult to form a martensite phase. Thus, from this viewpoint, when Co is added, it is set to 0.90% or less, and the content is preferably less than 0.50%, and more preferably less than 0.1%.

[0034] C: 0.01 - 0.10% When C is added at 0.10% or less, the hardenability can be improved without increasing the hardness as - formed. However, when C is added in an amount more than 0.10%, the hardness as - formed increases and shape cracking is likely to occur. Thus, from this viewpoint, C is set to 0.1% or less, preferably less than 0.05%, and more preferably less than 0.03%.

[0035] Nb: 0.01 - 2.00% Nb has the effect of refining crystal grains and is a component useful for ensuring strength. Therefore, when Nb is added, it is preferably added in an amount of 0.50% or more, and more preferably 1.00% or more. However, when a large amount of Nb is added, the toughness decreases. From this viewpoint, the Nb content is set to 2.00% or less, and preferably 1.50% or less.

[0036] The Fe-based alloy powder of the present invention must also satisfy the values of M1 and M2 of the indicators shown in Formula (1) and Formula (2). The reasons for setting these indicators are as follows.

[0037] (Hardening property index: The value of M1 is 13.0 or more) M1 = Ni + 0.8Cr + 0.6Mo - 0.3Ti ··· Formula (1) However, substitute the value of the mass % of the corresponding component into the element symbol in Formula (1). Formula (1) is an index related to hardening property. For the Fe-based alloy of the components defined in the present invention, when the value of M1 in Formula 1 is 13.0 or more, a martensite structure can be obtained. The higher the hardening property, the easier it is to obtain a martensite structure. When the value of M1 is less than 13.0, a bainite structure will result, and the toughness will deteriorate. Therefore, M1 = Ni + 0.8Cr + 0.6Mo - 0.3Ti ≧ 13.0. From these viewpoints, the value of M1 is 13.0 or more, preferably 15.0 or more, more preferably 15.3 or more, and particularly preferably 15.6 or more.

[0038] (Thermal conductivity index: The value of M2 is 17.0 or more) M2 = 41.9 - 0.9Ni - 2.0Mo - 2.1Cr ··· Formula (2) However, substitute the value of the mass % of the corresponding component into the element symbol in Formula (2). Formula (2) is an index related to thermal conductivity. When the value of M2 in Formula (2) is 17.0 or more, a thermal conductivity of 17.0 W / K / m or more can be obtained. When the value of M2 is less than 17.0%, the thermal conductivity deteriorates. Therefore, M2 = 41.9 - 0.9Ni - 2.0Mo - 2.1Cr ≧ 17.0. From these viewpoints, the value of M2 in Formula (2) is 17.0 or more, preferably 20.0 or more, more preferably 22.0 or more, and particularly preferably 23.5 or more.

[0039] (Index of transition density: The value of the full width at half maximum (FWHM) is 0.140 degrees or more) The full width at half maximum (FWHM) of the X-ray diffraction (XRD) peak refers to the width of the diffraction line at a height of 1 / 2 of the peak value of the diffraction line intensity. Generally, it is known that the higher the dislocation density (the total length of dislocation lines present in the unit volume of the crystal), the larger the value of the full width at half maximum. Therefore, as an index of dislocation density, the full width at half maximum of the XRD peak of the BCC (110) plane of iron (near 44 - 45° in 2θ) was fitted with a Lorentz function to quantify the FWHM. Note that since the diffraction peak of XRD using CuKα rays used for measurement may also broaden due to the instrument resolution, in order to remove the influence of the instrument resolution, LaB6 powder is used as a standard sample for correction.

[0040] Specifically, the full width at half maximum of the BCC (110) plane of iron is evaluated using the FWHM corrected by the following formula. (Corrected FWHM) = (FWHM of the measurement sample) - (FWHM of LaB6 powder)

[0041] By increasing the dislocation density, a martensite structure rather than a bainite structure can be obtained, so the toughness can be improved. From these viewpoints, the FWHM of the XRD peak of the (110) plane of bcc iron in the laminated structure in the present invention is set to 0.140 degrees or more at 2θ. Further, the value of the FWHM is preferably 0.145 degrees or more at 2θ, more preferably 0.150 degrees or more, and particularly preferably 0.153 degrees or more.

[0042] [Method for manufacturing Fe-based alloy powder] Examples of the method for manufacturing the powder include water atomization method, single-roll quenching method, twin-roll quenching method, gas atomization method, disk atomization method, and centrifugal atomization method. Preferred manufacturing methods are the single-roll cooling method, gas atomization method, and disk atomization method. Mechanical milling or the like may be applied to the powder. Examples of the milling method include ball milling method, bead milling method, planetary ball milling method, attritor method, and vibration ball milling method.

[0043] From the perspective of spheroidization, the gas atomization method is preferred for the powder used in additive manufacturing. Therefore, in the present invention, in the following examples, gas atomization will be described as an example.

[0044] [Manufacture of Powder] Steels with the chemical compositions of Examples 1 to 11 listed in Table 1 were each gas atomized to obtain Fe-based alloy powders. Also, steels with the chemical compositions of Comparative Examples 1 to 4 listed in Table 1 were similarly gas atomized to obtain Fe-based alloy powders.

[0045] Specifically, in a vacuum, using an alumina crucible, a raw material having a predetermined composition in Table 1 was heated by high-frequency induction heating and melted. Then, the molten metal was dropped from a nozzle with a diameter of 5 mm under the crucible. Next, argon gas was sprayed toward this molten metal to obtain a large number of particles. These particles were classified to remove particles with a diameter exceeding 63 μm, and an Fe-based alloy powder was obtained.

[0046]

Table 1

[0047] [Modeling] As a method for producing a shaped object, there is a rapid melting and rapid solidification process, which is a process of melting and solidifying metal powder. Specific examples of this process include three-dimensional additive manufacturing, thermal spraying, laser coating, and build-up welding. In particular, the Fe-based alloy powder of the present invention is suitable for the three-dimensional additive manufacturing method of the powder bed fusion bonding type, and a shaped object with a large size can be formed at a high density.

[0048] As a three-dimensional lamination forming method, for example, a 3D printer can be used. In the powder bed fusion bonding method (powder bed method) among the lamination forming methods, a laser beam or an electron beam is irradiated onto the laid Fe-based alloy powder of the present invention. By the irradiation, the particles are rapidly heated and rapidly melted. The melted particles then rapidly solidify. Due to this melting and solidification, the particles bond to each other. The irradiation is selectively performed on a part of the laid Fe-based alloy powder. Among the laid powder, the part where the irradiation is not performed does not melt. A bonding layer is formed only in the part where the irradiation is performed.

[0049] On top of the bonding layer, Fe-based alloy powder is further thinly laid. A part of this Fe-based alloy powder is irradiated with a laser beam or an electron beam. By the irradiation, the particles are rapidly melted. The melted particles then rapidly solidify. Due to this melting and solidification, the particles in the powder bond to each other, and a new bonding layer is formed. The new bonding layer is also bonded to the existing bonding layer.

[0050] By repeating the bonding by irradiation, an aggregate of bonding layers gradually grows. By this growth, a shaped object having a three-dimensional shape is obtained. By this lamination forming method, a shaped object with a complex shape can be easily obtained.

[0051] [Creation of laminated shaped body] Using the powder produced by gas atomization of the components described in Table 1 as a raw material, a lamination forming method using a three-dimensional lamination forming apparatus (EOS-M280) was carried out, and an attempt was made to form a rectangular parallelepiped of a large size (220×220×10 mm). For Examples 1 to 11, an as-formed object of this large size without heat treatment was obtained. In Examples 1 to 11 of the present invention, no defects were observed during the forming and in the formed object, and a desired laminated shaped object could be obtained.

[0052] [Age hardening heat treatment] Instead of using the as-formed non-heat-treated fabricated object directly, the fabricated object formed using Fe-based alloy powder undergoes an aging heat treatment process to obtain a fabricated object with the desired characteristics of the present invention. Note that since the Fe-based alloy powder of the present invention does not particularly require a solution treatment, the energy cost is suppressed accordingly.

[0053] Therefore, the following heat treatments were performed on the laminated fabricated objects of Examples 1 to 11. As the aging heat treatment, it was held at 480 to 580 °C for 5 hours and then air-cooled. By performing the heat treatment within an appropriate temperature range, a structure in which intermetallic compounds such as Ni3Mo and Ni3Al are sufficiently precipitated can be obtained. Also, the solid solution of alloying elements into the matrix phase is suppressed. Furthermore, the coarsening of crystal grains is suppressed. In the examples, the aging hardness was adjusted to 46 HRC (±0.5 HRC) by setting the aging temperature to 480 to 580 °C.

[0054] [Measurement of Thermal Conductivity] For the measurement of thermal conductivity, the laser flash method was used. The sample in the hardened and tempered state was finished into a disk shape with a diameter of 10 mm and a thickness of 1 mm and subjected to the test. The results are shown in Table 2. Also, Figure 2 shows a graph with the thermal conductivity on the vertical axis and the value of M2 in Equation (2) on the horizontal axis.

[0055] [X-ray Diffraction Measurement] A sample was taken from the fabricated object after laminated fabrication, and a diffraction pattern was obtained by measuring with an X-ray diffractometer before the heat treatment. Note that a diffraction pattern using CuKα rays with a Cu tube target as the X-ray source was measured. Also, by measuring the diffraction pattern of LaB6 powder as a standard sample, it was possible to correct the influence of the apparatus resolution.

[0056] Regarding the obtained diffraction pattern, the full width at half maximum of the peak of the (110) plane of bcc iron was obtained and evaluated whether it was 0.140 degrees or more at 2θ, and it was shown in the FWHM column of Table 2.

[0057] [Charpy Impact Test] In order to confirm the toughness of the shaped article, a Charpy impact test was carried out on a 2 mm V-notch test piece (10×10×55 mm), which is a JIS No. 4 test piece, in accordance with JIS Z 2242, and the average value of three tests was taken as the Charpy impact value. The results are shown in Table 2. In addition, Fig. 1 shows a graph with the Charpy impact value on the vertical axis and the value of M1 in formula (1) on the horizontal axis.

[0058]

Table 2

[0059] In addition, when each component in Table 1 is less than 0.01%, it is shown as 0. The underlines in Table 1 and Table 2 are outside the scope of the present invention.

[0060] From Table 1 and Table 2, the laminated formed bodies using the Fe-based alloy powders of Examples 1 to 11 have excellent thermal conductivity of 17.5 W / (m·K) or more, and at the same time, the Charpy impact value is 23.5 J / cm 2 or more and excellent crack resistance (toughness). Therefore, it can be seen that the laminated formed body made of the Fe-based alloy powder of the present invention has excellent characteristics with a good balance suitable for hot dies.

[0061] The Fe-based alloy powders of Examples 1 to 11 of the present invention, compared with general-purpose maraging steels with a large amount of alloying elements added, although the amount of alloying elements added is small, a martensite structure can be obtained after aging treatment after laminated forming without particularly requiring solution treatment. Since the amount of alloying components added can be suppressed, the laminated formed bodies of Examples 1 to 11 of the present invention have a large FWHM value and a high dislocation density. In addition to toughness, they are excellent in thermal conductivity. Among the examples, those with a large FWHM value and a high dislocation density are excellent in the Charpy impact value in Table 2 and have higher toughness.

[0062] In Comparative Example 1, Ni is excessive, the value of M2 is low, and the thermal conductivity is poor. In Comparative Examples 2 and 3, since the value of M1 is low and the value of FWHM on the (110) plane of bcc iron is small and the dislocation density is also low, the toughness is poor. In Comparative Example 4, Cr is excessive, the value of M2 is low, and the thermal conductivity is poor. As shown in Table 2, FIGS. 1 and 2, in the comparative examples, the characteristics are biased towards either the thermal conductivity or the toughness, and the required characteristics of both for the mold cannot be satisfied with sufficient balance.

Industrial Applicability

[0063] The Fe-based alloy powder of the present invention is suitable for metal additive manufacturing, and is particularly suitable for manufacturing a formed body for a hot mold for die casting by additive manufacturing.

Claims

1. In mass %, as essential components, it consists of an Fe-based alloy containing Ni: 10.0 to 16.0%, Mo: 0.1 to 5.0%, Ti: 0.5 to 2.5%, Al: 0.01 to 1.0%, Si: 0.8% or less, Mn: 0.8% or less, and the balance being Fe and unavoidable impurities. Moreover, it is an Fe-based alloy powder for additive manufacturing in which the value of M1 in formula (1) is 13.7 or more and the value of M2 in formula (2) is 17.0 or more. M1 = Ni + 0.8Cr + 0.6Mo - 0.3Ti... Formula (1) M2 = 41.9 - 0.9Ni - 2.0Mo - 2.1Cr... Formula (2) However, for the element symbols in formula (1) and formula (2), substitute the mass % values of the corresponding components.

2. The components according to Claim 1 further contain, as optional additional components, one or more selected from the group consisting of Cr: 6.00% or less, C: 0.01 to 0.10%, Co: 0.01 to 0.90%, Nb: 0.01 to 2.00%, and the balance being Fe and unavoidable impurities, and it consists of an Fe-based alloy. Moreover, it is an Fe-based alloy powder for additive manufacturing in which the value of M1 in formula (1) is 13.0 or more and the value of M2 in formula (2) is 17.0 or more. M1 = Ni + 0.8Cr + 0.6Mo - 0.3Ti... Formula (1) M2 = 41.9 - 0.9Ni - 2.0Mo - 2.1Cr... Formula (2) However, for the element symbols in formula (1) and formula (2), substitute the mass % values of the corresponding components.

3. An additive manufactured object formed by additive manufacturing using only the Fe-based alloy powder according to Claim 1 or 2.

4. The additive manufactured object according to Claim 3, wherein the full width at half maximum of the peak of the (110) plane of bcc iron in the X-ray diffraction pattern using CuKα radiation is 0.140 degrees or more in terms of 2θ.

Images