Method for manufacturing powder metal materials and non-magnetic steel for additive manufacturing

Abstract

To provide a powder metal material for additive manufacturing which can yield a shaped article with an excellent filling rate, and a method for producing a non-magnetic steel.SOLUTION: A powder metal material for additive manufacturing contains: (A) non-magnetic steel powder which is free of nitrogen; and (B) ferromanganese nitride powder, and the particle size of the component (B) is 15.0 μm≤D50≤25.0 μm in volume average particle size, and the content of the component (B) is 0.4-4.0 mass% relative to the total amount of the powder metal material.SELECTED DRAWING: None

Description

【Technical Field】 【0004】 , , , , , , , , , 【0005】 , , , , , 【0001】 The present invention relates to a powder metal material for additive manufacturing and a method for manufacturing non-magnetic steel. 【Background Art】 【0002】 In order to increase the strength of non-magnetic steel, solid solution strengthening or precipitation strengthening is the main means. It is known that solid solution strengthening by nitrogen has a large effect and a small resource risk. However, special equipment such as a pressure melting furnace and a large amount of energy are required to add nitrogen. On the other hand, in the powder bed fusion method, which is a type of additive manufacturing, alloying can be achieved by mixing multiple types of powders and laser melting them, and it is conceivable to add nitrogen by mixing powders containing nitrogen. 【0003】 A technique for additive manufacturing by mixing nitride powders has been developed. Patent Document 1 discloses a powder for additive manufacturing in which at least one type of ceramic particle composed of carbide, nitride, and carbonitride is mixed with a superhard alloy or cermet alloy powder. 【Prior Art Documents】 【Patent Documents】 【0004】 [[ID=​​​​​​​​​​​​​​Furthermore, nitrogen dissolved in iron tends to gasify during melting in additive manufacturing, creating void-like gas defects inside or erupting to the outside, which can degrade the surface properties. Therefore, there was room for further improvement in the infill density of the resulting molded objects. 【0006】 The present invention provides a powder metal material for additive manufacturing that can produce molded bodies with excellent filling efficiency, and a method for manufacturing non-magnetic steel. [Means for solving the problem] 【0007】 (1) The present invention is A powder metal material for additive manufacturing, The aforementioned powder metal material is (A) Non-magnetic steel powder that does not contain nitrogen, (B) Ferromangan nitride powder It contains, The particle size of component (B) is a volume-average particle size, with 15.0 μm ≤ D50 ≤ 25.0 μm. The powder metal material for additive manufacturing has a content of component (B) of 0.4 to 4.0 mass% relative to the total amount of the powder metal material. [Effects of the Invention] 【0008】 According to the present invention, it is possible to provide a powder metal material for additive manufacturing that can produce molded bodies with excellent filling efficiency, and a method for manufacturing non-magnetic steel. [Modes for carrying out the invention] 【0009】 The embodiments for carrying out the present invention will be described in detail below. 【0010】 [Powder metal materials for additive manufacturing] (1) The powder metal material for additive manufacturing of the present invention is (A) Non-magnetic steel powder that does not contain nitrogen, (B) Ferromangan nitride powder It contains, The particle size of component (B) is a volume-average particle size, with 15.0 μm ≤ D50 ≤ 25.0 μm. The powder metal material for additive manufacturing has a content of component (B) of 0.4 to 4.0 mass% relative to the total amount of the powder metal material. The powder metal material for additive manufacturing of the present invention makes it possible to obtain a fabricated body with excellent filling efficiency. 【0011】 <(A) Non-magnetic steel powder that does not contain nitrogen> The powder metal material of the present invention contains (A) nitrogen-free nonmagnetic steel powder (hereinafter also referred to as "component (A)" or "nonmagnetic steel powder"). Unless otherwise specified, the content of each alloying element is based on a mass basis, with the total non-magnetic steel powder being 100%. The non-magnetic steel powder preferably contains 0.2 to 1.0% carbon. Although carbon is an element that increases the strength of steel, a high carbon content tends to generate spatter during additive manufacturing, and the manufacturing time tends to increase in order to remelt and neutralize the resulting spatter. Therefore, there is an appropriate range for carbon content. The content of C is more preferably 0.20 to 0.50%, and even more preferably 0.20 to 0.40%. 【0012】 The non-magnetic steel powder preferably contains 8.0 to 15.0% Mn. The Mn content is more preferably 10.0-15.0%, and even more preferably 10.0-12.0%. 【0013】 The non-magnetic steel powder of the present invention may contain other elements in addition to the above elements. The other elements are not particularly limited as long as they do not hinder the effects of the present invention, but examples include Ni, Cr, Mo, etc. When the non-magnetic steel powder of the present invention contains Ni, the Ni content is preferably 10.0% by mass or less, and more preferably 3.0% by mass or less. When the non-magnetic steel powder of the present invention contains Cr, the Cr content is preferably 2.0 to 20.0% by mass, and more preferably 3.0 to 6.0% by mass. When the non-magnetic steel powder of the present invention contains Mo, the content of Mo is preferably 3.0% by mass or less, and more preferably 0.3 to 1.0% by mass. 【0014】 The non-magnetic steel powder of the present invention preferably has the above chemical composition, and the balance consists of Fe and inevitable impurities. 【0015】 Inevitable impurities are components that can inevitably be mixed in from raw materials and the environment when producing the non-magnetic steel powder in the present invention, and examples include Si, P, S, Cu, etc. The content of inevitable impurities is usually 1% by mass or less in the case of Si, 0.1% by mass or less in the case of P and S, and 0.5% by mass or less in the case of Cu. 【0016】 The non-magnetic steel powder does not contain nitrogen. Here, "not containing nitrogen" means that the non-magnetic steel powder contains nitrogen at 0.01% by mass or less with respect to the total amount of the non-magnetic steel powder. 【0017】 For the non-magnetic steel powder of the present invention, if it is the powder bed fusion method, the volume average particle diameter measured by a laser diffraction particle size distribution measuring device should satisfy D10 ≥ 20.0 μm and D90 ≤ 65.0 μm, and if it is the directed energy deposition method, D10 ≥ 50.0 μm and D90 ≤ 120.0 μm are preferred. 【0018】 The non-magnetic steel powder of the present invention is non-magnetic steel. Non-magnetic steel can be confirmed by measuring the relative magnetic permeability. The relative magnetic permeability shall be measured by a single-plate magnetic property test. Specifically, a measurement piece of 10 × 60 × 1 mm is made from the shaped body and measured by a micro single-plate magnetic property tester that can perform measurements according to JIS C 2556. If the obtained value of the relative magnetic permeability is in the range of 1.00 to 1.02, it is judged as non-magnetic. 【0019】 The method for producing the non-magnetic steel powder of the present invention is not particularly limited, and known methods (for example, gas atomization, water atomization, plasma atomization, plasma rotating electrode method, centrifugal atomization, etc.) can be employed. 【0020】 The content of component (A) is preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the total amount of powdered metal material. Component (A) may be used alone or in combination of two or more types. 【0021】 <(B) Ferromangan nitride powder> The powder metal material of the present invention contains (B) ferromanganese nitride powder (hereinafter also referred to as "component (B)"). Note that "ferromanganese nitride powder" is also simply referred to as "ferromanganese nitride". Since ferromanganite nitride has a lower melting point than iron, it can be easily melted and mixed during additive manufacturing. 【0022】 Ferromangan nitride is not particularly limited, but commercially available products can be suitably used. As ferromanganase nitride, for example, a C1% dry ferromanganase product from Nippon Heavy Chemical Industries Co., Ltd. can be used. 【0023】 The particle size of component (B) of the present invention is preferably 15.0 μm ≤ D50 ≤ 25.0 μm, measured by a laser diffraction particle size distribution analyzer. When D50 exceeds 25.0 μm, it tends to be difficult to achieve uniform mixing with component (A), which can worsen the resulting packing efficiency and is therefore undesirable. When D50 is less than 15.0 μm, it is also undesirable because, in addition to the tendency for uneven mixing, it worsens fluidity. Furthermore, the particle size of component (B) of the present invention is preferably such that the volume-average particle diameter measured by a laser diffraction particle size distribution analyzer is D10 ≥ 10.0 μm and D90 ≤ 30.0 μm. If D90 is 30.0 μm or less, it is preferable because it is easier to mix uniformly with component (A) and the variation in nitrogen concentration is less likely to become large when additive manufacturing is performed. On the other hand, if D10 is 10.0 μm or more, it is preferable because the fluidity of the powder metal material (mixed powder) becomes good. 【0024】 The content of component (B) is 0.4 to 4.0% by mass relative to the total amount of the powdered metal material. If the mixing ratio of ferromanganate nitride in the aforementioned powder metal material is high, nitrogen gas may be generated during laser melting in additive manufacturing, potentially forming gas defects inside the product or degrading the surface properties of the resulting product (molded object). Consequently, the infill rate of the resulting molded object may deteriorate. The inventors diligently studied how to improve the infill rate of the resulting molded bodies and focused on the nitrogen content in the molded bodies. They found that by keeping the nitrogen content in the molded bodies below 0.3% by mass, the infill rate was improved. Therefore, it is desirable to keep the nitrogen content of component (B) in the powder metal material for additive manufacturing to 0.3 mass% or less, assuming that all of the mixed powder in the above powder metal material becomes an alloy. In consideration of the above, the content of component (B) was set to 4.0 mass% or less of the total amount of powder metal material. Furthermore, from the perspective of the effect of nitrogen content in the molded object, the content of component (B) was set to 0.4% by mass or more. Furthermore, the inventors have found that the volume-average particle size (D50) of component (B) also contributes to the filling efficiency of the resulting molded body. Although the detailed reasons are unclear, if the volume-average particle size (D50) of component (B) exceeds 25.0 μm, the mixing of component (B) and component (A) tends to be less uniform, which can worsen the filling efficiency of the molded object and is therefore undesirable. Furthermore, if the D50 of component (B) is less than 15.0 μm, it is undesirable not only because the mixing with component (A) tends to be less uniform, but also because it worsens the fluidity. Considering the above points, the particle size of component (B) was set to a volume-average particle size of 15.0 μm ≤ D50 ≤ 25.0 μm. 【0025】 The content of component (B) is preferably 0.5 to 4.0% by mass, more preferably 0.5 to 2.0% by mass, and even more preferably 0.8 to 1.5% by mass, based on the total amount of powdered metal material. Component (B) may be used alone or in combination of two or more types. 【0026】 The powder metal material of the present invention can be manufactured by appropriately mixing component (A) and component (B). The powder metal material of the present invention may contain further components as long as the effects of the present invention are not impaired. In one preferred embodiment, the powder metal material of the present invention preferably consists only of component (A) and component (B). 【0027】 <Method for manufacturing non-magnetic steel> The present invention provides a method for producing non-magnetic steel, comprising the step of 3D printing additive manufacturing of the powder metal material to produce non-magnetic steel having a nitrogen content of 0.3% by mass or less, and including the step of 3D printing additive manufacturing of the powder metal material. The above process specifically involves using the aforementioned powder metal material to create a 3D object using a 3D printer. This makes it possible to manufacture the aforementioned non-magnetic steel. The above process is 3D printing, in which a powder metal material is melted by irradiation with a laser or electron beam and then cooled to create a 3D object. Publicly available 3D printers can be used. The additive manufacturing method is not particularly limited, but for example, powder bed fusion and directed energy deposition are preferred. Among these, powder bed fusion is particularly preferred. In one preferred embodiment, a non-magnetic steel having a nitrogen content of 0.3% by mass or less can be suitably produced by melting and bonding the powder metal material containing component (A) and component (B) in a powder bed fusion method, which is a type of additive manufacturing. 【0028】 The nitrogen content in the non-magnetic steel (formed body) obtained by the above manufacturing method is 0.3% by mass or less. If the nitrogen content exceeds 0.3% by mass, the filling efficiency of the resulting formed body tends to decrease. Furthermore, from the viewpoint of the effect of nitrogen content in the formed body, it is preferable that the nitrogen content in the above non-magnetic steel be 0.05% by mass. The nitrogen content (nitrogen concentration) was measured at five arbitrary locations on the fabricated object by local analysis using an electron probe microanalyzer (EPMA). 【0029】 Nitrogen is effective in improving the strength and corrosion resistance of non-magnetic steel, but conventional methods require special equipment such as pressurized melting furnaces and a great deal of energy. In contrast, this invention allows for nitrogen addition simply by mixing ferromanganese nitride into the raw material powder before manufacturing and performing additive manufacturing, thereby reducing manufacturing costs and conserving resources. 【0030】 As described above, the non-magnetic steel is non-magnetic. This is because component (A) is non-magnetic, and the nitrogen added by ferromanganese nitride (component (B)) further stabilizes the non-magnetic austenite phase. Non-magnetic steel can be identified by measuring its relative permeability. Relative permeability shall be measured by a single-sheet magnetic properties test. Specifically, a 10 × 60 × 1 mm measurement piece shall be prepared from the molded body and measured using a micro-single-sheet magnetic properties tester capable of performing measurements in accordance with JIS C 2556. If the obtained relative permeability value is in the range of 1.00 to 1.02, it is determined to be non-magnetic. [Examples] 【0031】 The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto. 【0032】 (Component (A)) Non-magnetic steel powder 1 (with volume-average particle size measured using a laser diffraction particle size distribution analyzer (Anton Paar, PSA1090), D10 = 20.5 μm, D90 = 64.0 μm) with the composition shown in Table 1 below was prepared by gas atomization. 【0033】 [Table 1] 【0034】 Furthermore, non-magnetic steel powder 1 was non-magnetic steel and did not contain nitrogen. 【0035】 (Example 1, Comparative Examples 1-2) A mixed powder (powdered metal material) of the above non-magnetic steel powder 1 and component (B) listed in Table 2 was used to create each non-magnetic steel (molded body) by additive manufacturing using a 3D printer. An EOS M290 3D printer was used, with the following printing conditions: output power 240W, layer thickness 40μm, scan speed 900mm / s, hatch distance 0.1mm, and preheating temperature at room temperature. The additive manufacturing method used was powder bed fusion. 【0036】 <Measurement of nitrogen content (nitrogen concentration)> The nitrogen content (nitrogen concentration) was measured at five arbitrary locations on the resulting molded object by local analysis using an electron probe microanalyzer (EPMA). 【0037】 <Measuring the filling rate> The filling efficiency was determined by using an optical microscope (Olympus GX51) to photograph the unpolished tissue at 15 arbitrary locations on the obtained molded object, binarizing the images, and averaging the area ratio of the sound areas. 【0038】 The results obtained are shown in Table 2. The content of component (B) in Table 2 is the content (mass%) relative to the total amount of powdered metal material. The average particle size of component (B) is the volume-average particle diameter D50 measured using a laser diffraction particle size distribution analyzer (Anton Paar, PSA1090). Furthermore, the molded bodies obtained in Example 1 and Comparative Examples 1-2 were made of non-magnetic steel. 【0039】 [Table 2] 【0040】 Ferromanganase nitrides 1-3 in Table 2 are as follows: Ferromanganese nitride 1, 2: Dry ferromanganese C 1% powder manufactured by Nippon Heavy Chemical Industries Co., Ltd., classified into D50=19.2μm, D10=15.1μm, and D90=29.8μm by pulverization. Ferromanganese Nitride 3: Dry ferromanganese C 1% powder manufactured by Nippon Heavy Chemical Industries Co., Ltd., classified by pulverization to D50=48.5μm, D10=35.4μm, and D90=63.8μm. 【0041】 For ferromanganase nitride 1-3, the volume-average particle size D10 and volume-average particle size D90 were measured using a laser diffraction particle size distribution analyzer (Anton Paar, PSA1090), respectively. 【0042】 Table 2 shows that the powder metal material of Example 1 can be used to manufacture molded objects with excellent filling efficiency. 【0043】 Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and modifications, improvements, etc., can be made as appropriate. 【0044】 Furthermore, this specification contains at least the following information: 【0045】 (1) Powder metal material for additive manufacturing, The aforementioned powder metal material is (A) Non-magnetic steel powder that does not contain nitrogen, (B) Ferromangan nitride powder It contains, The particle size of component (B) is a volume-average particle size, with 15.0 μm ≤ D50 ≤ 25.0 μm. The powder metal material for additive manufacturing has a content of component (B) of 0.4 to 4.0 mass% relative to the total amount of the powder metal material. According to (1), a molded body with excellent infill rate can be obtained. 【0046】 (2) A method for producing non-magnetic steel having a nitrogen content of 0.3% by mass or less, by 3D printing additive manufacturing of the powder metal material for additive manufacturing described in (1). According to (2), a molded body with excellent infill rate can be obtained.

Claims

[Claim 1] A powder metal material for additive manufacturing, The aforementioned powder metal material is (A) Non-magnetic steel powder that does not contain nitrogen, (B) Ferromanganese nitride powder It contains, The particle size of component (B) is a volume-average particle size of 15.0 μm ≤ D50 ≤ 25.0 μm. The powder metal material for additive manufacturing has a content of component (B) of 0.4 to 4.0 mass% relative to the total amount of the powder metal material. [Claim 2] A method for producing non-magnetic steel, comprising 3D printing and additive manufacturing of a powder metal material for additive manufacturing as described in claim 1, to produce non-magnetic steel with a nitrogen content of 0.3% by mass or less.

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