Method for manufacturing high-hardness, high-corrosion-resistant additively manufactured products and high-hardness, high-corrosion-resistant additively manufactured products

Abstract

To provide a laminated shaped article which materializes high hardness and high corrosion resistance and furthermore enables prevention of cracking of the laminated shaped article after the laminated shaped article is solidified, and a manufacturing method for the laminated shaped article.SOLUTION: A three-dimensionally laminated shaped article is manufactured, by arc welding, using welding material composed of medium-carbon martensitic stainless steel which has prescribed components and in which a D value obtained by a formula (1) is in the range of 0-10. In the manufacturing of the above three-dimensionally laminated shaped article, a time (between-lamination interval) during which an arbitrary layer 6 of a laminated shaped article 1 is laminated and then a layer on the arbitrary layer is laminated, is set to be 60 seconds or less, and the arbitrary layer 6 is cooled down to 600°C or less at a cooling rate exceeding an average 20°C / s, within 600 seconds after the arbitrary layer is laminated: D=Cr+1.2Mo+0.5Si+2.5Al+10Ti+5 Nb+3 V-25C-18 N-Ni-0.1Mn-4 (1).SELECTED DRAWING: Figure 1

Description

Technical Field

[0005] ,

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[0003]

[0001] The present invention relates to a method for manufacturing a high-hardness and high-corrosion-resistant laminated molded product by three-dimensional laminated molding by arc welding using a welding material of a stainless steel wire, and a high-hardness and high-corrosion-resistant laminated molded product.

Background Art

[0002] In recent years, metal 3D printers have been expected as innovative production technologies, and various technologies have been proposed. As the main technical methods, using metal powder and using a metal wire have been proposed. When using a metal wire, for example, a method of laminating weld beads by a metal wire to form a three-dimensional part has been disclosed (Patent Document 1). Further, a manufacturing method of controlling arc or plasma to weld a stainless steel metal wire and laminating it three-dimensionally has been disclosed (Patent Document 2).

[0003] Patent Document 3 discloses a stainless steel-based metal wire that is adjusted in composition so that a low C, N martensite structure always appears by controlling the transformation temperature of the metal structure in a manufacturing method of a 3D printer that performs three-dimensional modeling by welding and laminating with a metal wire, and has excellent heat resistance (heat deformation resistance), material and metal structure uniformity, internal crack resistance, and internal void resistance.

[0004] Patent Document 4 discloses a three-dimensional modeling method for laminating weld beads on a substrate for the purpose of improving the shape accuracy of a three-dimensional object, in which the substrate is placed in a cooling tank and the water level of the coolant in the cooling tank is adjusted so that the water level of the coolant is below the welding surface.

[0005] Patent Document 5 discloses a high-strength martensitic stainless steel with excellent rust resistance, such as a high-strength spring. The DI value is defined by equation (2) regarding the influence of various elements on the amount of δ-ferrite in the base material. It states that if the DI value exceeds 0 (%), δ-ferrite is present, which not only reduces the hardness and toughness of the quenching process but also causes carbonitrides to precipitate at the δ-ferrite interface during quenching, significantly reducing rust resistance, so it is limited to less than 0 (%). To ensure rust resistance and prevent quench cracking during quenching, the cooling rate is disclosed to be 0.5 to 20°C / s. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2003-266174 [Patent Document 2] Japanese Patent Publication No. 2018-507317 [Patent Document 3] Japanese Patent Publication No. 2020-147785 [Patent Document 4] Japanese Patent Publication No. 2011-83778 [Patent Document 5] Japanese Patent Application Publication No. 6-264194 [Overview of the project] [Problems that the invention aims to solve]

[0007] There is a demand for additively manufactured products that are highly hard and corrosion-resistant, which are formed in three dimensions by welding and layering using metal wires. One possible method is to use martensitic stainless steel as the welding material for additive manufacturing.

[0008] This prevents cracks that occur from the surface to the interior during the cooling process after metal 3D additive manufacturing, and also ensures that Hv≧40 in the additively manufactured material. 0 The objective is to ensure high hardness and corrosion resistance at a level where rust does not form (no runoff rust) after surface preparation such as surface grinding, according to JIS standards for salt spray corrosion resistance over 3 days.

[0009] Here, the term "cracking" refers to both hot cracks that occur immediately after solidification and cold cracks that occur due to residual stress at low temperatures. Air oxidation and dendritic structures are observed on the fracture surface of hot cracks, while air oxidation is almost absent on the fracture surface of cold cracks, and prior γ grain boundaries and cleavage fracture surfaces are observed. The present invention aims to suppress not only cold cracks but also hot cracks that tend to occur near the surface.

[0010] When a martensitic stainless steel with a high hardness and corrosion resistance composition was used as a welding material for additive manufacturing, it was found that cracks occurred in the additively manufactured products after solidification.

[0011] The present invention aims to provide a method for manufacturing high-hardness, high-corrosion-resistant additively manufactured products, and to prevent cracking in additively manufactured products after solidification while achieving high hardness and high corrosion resistance. [Means for solving the problem]

[0012] In other words, the gist of this invention is as follows: [1] A method for manufacturing additively manufactured products by arc welding using stainless steel wire as a welding material to create a three-dimensional additive structure, The composition of the aforementioned solubilant is, in mass%, C: 0.10~0.35%, Si≦3.0%, Mn≦5.0%, S≦0.03%, P≦0.05%, Cr: 11.5~17%, N≦0.15%, O≦0.015%, with the remainder being Fe and impurities, and the D value defined by the following formula (1) is 0~10. A method for manufacturing a high-hardness, high-corrosion-resistant additively manufactured product, characterized by setting the time between stacking any layer of the additively manufactured product and stacking the layer above it (hereinafter referred to as the "inter-stack interval") to 60 seconds or less, and cooling the layer to 600°C or less at an average cooling rate of more than 20°C / s within 600 seconds after stacking the arbitrary layer. D=Cr+1.2Mo+0.5Si+2.5Al+10Ti+5Nb+3V-25C-18N-Ni-0.1Mn-4 (1) In equation (1), the element symbol represents the content (mass %) of that element in the solubilant. [2] The method for manufacturing a high-hardness, high-corrosion-resistant additively manufactured product according to [1], characterized in that the cooling described in the preceding paragraph is water-cooled. [3] A method for manufacturing a high-hardness, high-corrosion-resistant additively manufactured product as described in [1] or [2] above, A method for manufacturing high-hardness, high-corrosion-resistant additively manufactured products, characterized by completing additive manufacturing within 600 seconds after the start of additive manufacturing, and then water-cooling the entire layer within 600 seconds after the start of additive manufacturing. [4] A method for manufacturing a high-hardness, high-corrosion-resistant additively manufactured product according to any one of [1] to [3], characterized in that the composition of the solvent further contains, by mass%, one or more of the following in place of a portion of the Fe: Cu≦3.5%, Ni≦5%, Mo≦3.0%, Al≦2.0%, B≦0.01%, Ti≦0.5%, Nb≦1.0%, V≦1.0%, Co≦3.0%, W≦2.0%, Ta≦1.0%, Ca≦0.01%, Mg≦0.01%, REM≦0.1%, and Zr≦0.1%.

[0013] [5] The composition is in mass%, containing C: 0.10~0.35%, Si≦3.0%, Mn≦5.0%, S≦0.03%, P≦0.05%, Cr: 11.5~17%, N≦0.15%, O≦0.015%, with the remainder being Fe and impurities, and the D value defined by the following formula (1) is 0~10. It is made up of multiple layers that are layered together. A high-hardness, high-corrosion-resistant additively manufactured product characterized by a hardness of Hv≧400, no rust flow occurring after 3 days of JIS salt spray testing following surface polishing with #500 grit, and a layer spacing of 2.5 mm or less. D=Cr+1.2Mo+0.5Si+2.5Al+10Ti+5Nb+3V-25C-18N-Ni-0.1Mn-4 (1) In equation (1), the element symbol represents the content (mass %) of that element in the additively manufactured product. [6] The composition further contains, in mass %, one or more of Cu ≤ 3.5%, Ni ≤ 5%, Mo ≤ 3.0%, Al ≤ 2.0%, B ≤ 0.01%, Ti ≤ 0.5%, Nb ≤ 1.0%, V ≤ 1.0%, Co ≤ 3.0%, W ≤ 2.0%, Ta ≤ 1.0%, Ca ≤ 0.01%, Mg ≤ 0.01%, REM ≤ 0.1%, and Zr ≤ 0.1% in place of a part of the Fe, and is characterized as the high-hardness and high-corrosion-resistance laminated molded article described in [5].

Advantages of the Invention

[0014] By applying a predetermined component composition and a predetermined manufacturing method, the laminated molded article of the present invention can have high hardness and high corrosion resistance and be a laminated molded article without cracks.

Brief Description of the Drawings

[0015] [Figure 1] It is a diagram showing a laminated molded article formed by welding and laminating.

Embodiments for Carrying Out the Invention

[0016] [[ID=​​​​​​​​Here, we define the "layering direction 12" in additive manufacturing. In a coordinate system fixed to the manufactured product, the direction of movement of the welding machine is the welding direction 11, and the welded material 3 is arranged linearly in the welding direction 11, forming a layer 6. Further welding is repeated on the already welded linear layer 6 (welded material 3). In the case shown in Figure 1, a new welded material 3 is formed on top of the previously welded welded material 3. By repeating this sequentially, a layered structure in which layers 6 (welded material 3) are stacked is formed. Here, the direction in which layers 6 (welded material 3) are sequentially stacked is called the "layering direction 12". The additive manufactured product 1 is usually formed in the shape of a "surface", and this surface is called the "layering surface 4". In the example shown in Figure 1, the layering surface 4 forms a cylindrical surface. Both the welding direction 11 and the layering direction 12 are parallel to the layering surface 4, and the layering direction 12 is perpendicular to the welding direction 11.

[0019] When using martensitic stainless steel with a high hardness and corrosion resistance composition as a welding material for additive manufacturing, it was found that forming δ-ferrite in the post-solidification metal structure is effective in preventing cracking in the additively manufactured product after solidification. However, it was found that in the metal structure in which δ-ferrite is formed, carbides form around the δ-ferrite, thereby reducing the corrosion resistance of the steel. In contrast, it was found that rapid cooling after solidification suppresses the formation of carbides around the δ-ferrite, thereby achieving high corrosion resistance.

[0020] Furthermore, if the temperature history is uneven immediately after the melting and layering of the material and subsequent solidification, cracking after solidification is promoted. In contrast, it has been found that cracking after solidification can be prevented by setting the time between layering any given layer of the additively manufactured product and layering the layer above it (layer interval) to less than a predetermined time. The details are explained below.

[0021] 《Composition of steel》 The components of the welding material used in the manufacturing method of the high-hardness, high-corrosion-resistant additively manufactured product of the present invention, and the composition of the high-hardness, high-corrosion-resistant additively manufactured product are described below. % represents mass%. The steel having the following component composition is a medium-carbon martensitic stainless steel. First, let's discuss the essential components.

[0022] (C: 0.10~0.35%) C is added at a concentration of 0.10% or more to ensure uniform hardness with Hv ≥ 400. On the other hand, if it exceeds 0.35%, it becomes difficult to suppress cracking, so the upper limit is set at 0.35%. Preferably, it is between 0.15% and 0.30%.

[0023] (Si ≤ 3.0%) Si is effective in deoxidizing during welding, and is preferably added at a concentration of 0.1% or more. However, adding it in excess of 3.0% promotes the precipitation of intermetallic compounds during additive manufacturing, which can lead to crack formation, so the upper limit should be 3.0%. Preferably, it should be 1.0% or less. Si may not be included.

[0024] (Mn≦5.0%) Mn is effective against acid during welding and should be added at a concentration of 0.1% or more. However, if added in excess of 5.0%, the austenite structure becomes unstable, making it difficult to harden and preventing a stable Hv ≥ 400. Therefore, the upper limit should be 5.0%. Preferably, it should be 1.5% or less. Mn may not be included.

[0025] (S≦0.03 replacement S is present as an impurity. S ensures adequate flowability during welding, improving the accuracy of the laminated shape and enhancing subsequent machinability such as cutting. However, adding it in excess of more than 0.03% promotes cracking, so the upper limit is set at 0.03%. Preferably, it is 0.005% or less.

[0026] (P ≤ 0.05%) P is present as an impurity. The amount of P is limited to 0.05% or less to suppress internal cracking during molding. Preferably, it is 0.03% or less.

[0027] (Cr: 11.5~17%) Cr is added at a concentration of 11.5% or more to ensure corrosion resistance, but if it exceeds 17%, the amount of austenite formation increases, making it impossible to stably obtain Hv≧400, so the upper limit is set at 17%. Preferably, it is between 12% and 16%.

[0028] (N ≤ 0.15%) N is present as an impurity. N is preferably added in amounts of 0.01% or more, together with C, to ensure a uniform hardness of Hv ≥ 400. On the other hand, if it exceeds 0.15%, it becomes difficult to suppress defects such as bubbles and cracks, so the upper limit is set at 0.15%. Preferably, it is 0.11% or less.

[0029] (0 ≤ 0.015%) O is present as an impurity. O helps to ensure adequate molten metal flow during welding and improves the accuracy of additive manufacturing, but if it exceeds 0.015%, it becomes difficult to suppress cracks originating from large oxides, etc., so the upper limit is set at 0.015%. Preferably, it is 0.010% or less.

[0030] The components of the solvent used in the method for manufacturing high-hardness, high-corrosion-resistant additively manufactured products of the present invention, and the composition of the high-hardness, high-corrosion-resistant additively manufactured products, contain the above-mentioned essential components, with the remainder being Fe and impurities. In place of a portion of the Fe, one or more of the following components may be included.

[0031] (Cu ≤ 3.5%) Cu may be added as needed to improve the toughness and corrosion resistance of the matrix, but since exceeding 3.5% promotes cracking, the upper limit should be 3.5%. Preferably, it should be 1.5% or less. Levels below 0.1% are unavoidable impurities.

[0032] (Ni≦5%) Ni may be added as needed to improve the toughness and corrosion resistance of the matrix, but if it exceeds 5%, austenite will form and a stable Hv≧400 cannot be obtained, so the upper limit should be 5%. Preferably, it is between 0.06 and 1.5%. Levels below 0.1% are unavoidable impurity levels.

[0033] (Mo ≤ 3.0%) Mo may be added as needed to improve the corrosion resistance of the matrix, but since exceeding 3.0% promotes cracking, the upper limit should be 3.0%. Preferably, it should be 2.5% or less. Levels below 0.1% are unavoidable impurities.

[0034] (Al ≤ 2.0%) Al is effective in deoxidizing during additive manufacturing and may be added as needed, but since exceeding 2.0% promotes cracking, the upper limit should be 2.0%. Preferably, it should be 0.5% or less. Below 0.005% is an unavoidable impurity level.

[0035] (B ≤ 0.01%) B may be added as needed to improve the toughness of the matrix, but since it promotes cracking if it exceeds 0.01%, the upper limit should be 0.01%. Preferably, it should be 0.008% or less. Levels below 0.001% are unavoidable impurity levels.

[0036] (Ti ≤ 0.5%) Ti may be added as needed to improve the corrosion resistance of the matrix, but the upper limit should be 0.5% because exceeding 0.5% will cause the formation of coarse precipitates and promote cracking. Preferably, it should be 0.3% or less. Levels below 0.01% are unavoidable impurities.

[0037] (Nb ≤ 1.0%) Nb may be added as needed to improve the corrosion resistance of the matrix, but the upper limit should be 1.0% because exceeding 1.0% will cause the formation of coarse precipitates and promote cracking. Preferably, it should be 0.6% or less. Anything less than 0.01% is an unavoidable impurity.

[0038] (V ≤ 1.0%) V may be added as needed to improve the corrosion resistance of the matrix, but since exceeding 1.0% will cause the formation of coarse precipitates and promote cracking, the upper limit should be 1.0%. Preferably, it should be 0.6% or less. Anything less than 0.01% is an unavoidable impurity.

[0039] (Co ≤ 3.0%) Co may be added as needed to improve the toughness and corrosion resistance of the matrix, but if it exceeds 3%, austenite will form and a stable Hv≧400 cannot be obtained, so the upper limit should be 3.0%. Levels below 0.1% are unavoidable impurity levels.

[0040] (W≦2.0%) W may be added as needed to improve the corrosion resistance of the matrix, but since exceeding 2.0% promotes cracking, the upper limit should be 2.0%. Levels below 0.1% are unavoidable impurity levels.

[0041] (Ta ≤ 1.0%) Ta may be added as needed to improve the corrosion resistance of the matrix, but the upper limit should be 1.0% because exceeding 1.0% will cause the formation of coarse precipitates and promote cracking. Anything less than 0.01% is an unavoidable impurity.

[0042] (Ca ≤ 0.01%) Ca is effective in deoxidizing during additive manufacturing and may be added as needed, but since it promotes cracking above 0.01%, the upper limit should be 0.01%. Levels below 0.001% are unavoidable impurity levels.

[0043] (Mg ≤ 0.01%) Mg is effective in deoxidizing during additive manufacturing and may be added as needed, but since it promotes cracking above 0.01%, the upper limit should be 0.01%. Levels below 0.001% are unavoidable impurity levels.

[0044] (REM ≤ 0.1%) REM is effective in deoxidizing during additive manufacturing and may be added as needed, but since it promotes cracking above 0.1%, the upper limit should be 0.1%. Levels below 0.001% are unavoidable impurity levels.

[0045] (Zr≦0.1%) Zr is effective for corrosion resistance and deoxidation during additive manufacturing, so it may be added as needed. However, since it promotes cracking if it exceeds 0.1%, the upper limit should be 0.1%. Levels below 0.001% are unavoidable impurity levels.

[0046] In this invention, the D value defined by equation (1) below is set to 0 to 10. The D value in equation (1) is an equation that shows the relationship between the ease of formation of δ-ferrite in steel after solidification during additive manufacturing and the steel composition. This equation is a fitting based on the results of an investigation into the relationship after solidification during additive manufacturing, which is the target of this invention, based on known relational equations after thermal processing, such as the DI value in Patent Document 5. If the D value is positive, δ-ferrite is more easily formed in the steel during solidification. In this invention, by setting the D value in equation (1) to 0 or greater, i.e., a positive value, δ-ferrite is intentionally formed in the steel. The formation of δ-ferrite can prevent the occurrence of cracks in additively manufactured products after solidification. On the other hand, the value of D in equation (1) is set to 10 or less. This is because if the D value exceeds 10, the formation of carbides during cooling becomes significant, and the corrosion resistance deteriorates. However, in a metal structure in which δ-ferrite is formed, carbides tend to form around the δ-ferrite, which causes a decrease in the corrosion resistance of the steel. In contrast, as described in the manufacturing method below, the present invention suppresses the formation of carbides around the δ-ferrite by performing rapid cooling after solidification, thereby achieving high corrosion resistance. D=Cr+1.2Mo+0.5Si+2.5Al+10Ti+5Nb+3V-25C-18N-Ni-0.1Mn-4 (1) In equation (1), the element symbol represents the content (mass%) of that element in the welding material and the additively manufactured product.

[0047] Method for manufacturing additively fabricated products A metal 3D printer that uses metal wire as a welding material can be used to form additively manufactured parts by welding. For example, using a robotic MIG arc welder, stainless steel wire is used as the welding material, and the welder is moved at a head movement speed V (mm / s) in the welding direction 11, repeatedly welding in a spiral pattern, and stacking in the stacking direction 12 shown in Figure 1 to create a three-dimensional object, producing an additively manufactured part 1 consisting of a hollow cylinder (diameter D (mm)) as shown in Figure 1 on a substrate 2.

[0048] As mentioned above, the time T(s) between stacking any layer of an additively manufactured product and stacking the layer above it is called the "inter-layer interval." If the inter-layer interval T is too long, the time between the stacking of any layer and the welding of the layer above it is too long, causing the layer to cool excessively before being reheated. This increases the non-uniformity of the temperature history and makes the additively manufactured product more prone to cracking. On the other hand, if the inter-layer interval T is 60s or less, the temperature history is made uniform, and cracking in the additively manufactured product can be prevented. An inter-layer interval T of 30s or less is even more preferable.

[0049] The interval between layers T (s) is the distance between the circumference L (mm) of the layered object and the welding machine head movement speed V (mm / s). T=L / V This is related to the following: Therefore, by adjusting the welding machine head movement speed V (mm / s) according to the circumference L (mm) of the additively manufactured object, the interval T (s) between layers can be adjusted to a target time.

[0050] As described above, in order to prevent crack formation, the present invention generates δ-ferrite in the steel after solidification during additive manufacturing by setting the D value in equation (1) to a value of 0 or greater. However, in the metal structure in which δ-ferrite is formed, carbides tend to form around the δ-ferrite, which reduces the corrosion resistance of the steel. In contrast, in the present invention, any layer is cooled to 600°C or below within 600 seconds after stacking at an average cooling rate of more than 20°C / s. By such rapid cooling, the formation of carbides around the δ-ferrite is suppressed, and good corrosion resistance can be ensured. It is preferable to start rapid cooling within 250 seconds after stacking. Furthermore, it is more preferable to have an average cooling rate of more than 30°C / s during rapid cooling. As for the cooling method, forced air cooling using an air nozzle or water cooling using a water cooling nozzle can be used, and water cooling is preferred. For cooling, it is preferable to start cooling from the lower layer by nozzle injection no later than 600 seconds after the start of additive manufacturing, and then continuously move the nozzle upward to control the position of the cooling nozzle so that the solidified area is always cooled within 600 seconds after the start of the additive manufacturing process.

[0051] Regarding the start of rapid cooling as described above, it is preferable to start cooling continuously from the lower layer to the upper layer after two more layers have been laminated on top of the layer at the position where cooling is to begin. If cooling is started too early, the temperature of the additively manufactured part will become uneven, which will not only induce cracking, but the cooling period of the entire part will also be prolonged, and the amount of heat released to the lower part of the upper manufactured layer that has not been cooled will increase. As a result, the cooling start temperature of the upper part will decrease, making it easier for carbides to precipitate, thus degrading corrosion resistance. On the other hand, if rapid cooling is started after two layers have been laminated, these problems can be avoided. Preferably, cooling is started after five or more layers, and more preferably after ten or more layers have been laminated. Since the interval T between layers in this invention is 60s or less, if rapid cooling is started immediately after two layers have been laminated, rapid cooling can be started within 600s after lamination. It is preferable to rapidly cool the entire part, such as by water cooling, as soon as the additive manufacturing is completed. In other words, in this invention, by performing additive manufacturing at high speed and continuously initiating rapid cooling midway through, it is possible to maintain a large temperature gradient between the low-temperature region of the cooling section and the high-temperature region above the additive layer, making it possible to rapidly harden the material from a high temperature in the cooling section. Furthermore, it becomes possible to perform multi-layer additive manufacturing with an interlayer interval of 60 seconds or less, complete the additive manufacturing process with high-speed printing in less than 600 seconds after the start of additive manufacturing, and then quickly water-cool the entire layer within 600 seconds after the start of additive manufacturing. As a result, any layer of the additively manufactured product can be cooled within 600 seconds after it is built up.

[0052] Additive-formed products The additively manufactured product 1 of the present invention has the above composition as its component composition, the D value of formula (1) is 0 to 10, and as shown in Figure 1, it is made up of multiple layers 6 additively manufactured, has a hardness of Hv≧400, and after surface polishing with #500, no flow rust occurs in the JIS Z 2371 neutral salt spray test for 3 days, and the layer spacing is 2.5 mm or less. The above hardness and corrosion resistance can be achieved by having the above component composition and the D value of formula (1) and manufacturing it according to the above manufacturing method. By having a layer spacing of 2.5 mm or less, additive manufacturing can be performed at a uniform temperature and then cooled uniformly, resulting in a uniform hardness distribution and good corrosion resistance. Preferably, the layer spacing is 2.0 mm or less, and more preferably 1 mm or less. [Examples]

[0053] Steel with the chemical compositions shown in Tables 1 and 2 was melted in a 45 kg vacuum melting furnace and processed into 11 mm diameter steel bars by hot forging and hot extrusion. Subsequently, wire drawing and annealing were repeated to produce φ1.2 mm metal wire, which was used as a welding material for MIG arc welding. In Tables 1 to 4, values ​​outside the scope of the present invention are underlined.

[0054] [Table 1]

[0055] [Table 2]

[0056] [Table 3]

[0057] [Table 4]

[0058] Using a robotic CMT arc welding machine, a SUS420J1 series (13%Cr-0.2%C) steel plate (φ80mm-15mmt) was used as the substrate 2. Various prototype metal wires were used as the welding material and repeatedly welded onto it in a spiral pattern, continuously layering them. By layering in the layering direction 12 shown in Figure 1, a cylindrical shape (inner diameter 60mm, outer diameter 70mm) with a height of 30mm was 3D fabricated to form the additively fabricated product 1. At this time, the head movement speed V of the arc welding machine was changed to vary the layering interval T to the values ​​shown in Table 3 (5 to 200 s).

[0059] For arc welding, a shielding gas of Ar + 3% oxygen was used, with a welding current of 200A, an arc voltage of 20V, and a standard material supply rate of 800cc / h.

[0060] In Examples No. 1-17 and 19-27 of the present invention in Table 3, and Comparative Examples No. 1-25, 28, and 30-32 in Table 4, the welding material supply speed is set to the standard speed described above, and as a result, the lamination pitch is approximately proportional to the interval T between layers. In Example 18 of the present invention and Comparative Examples 26, 27, and 29, the welding material supply speed is slower than the standard speed described above and adjusted to achieve a predetermined lamination pitch.

[0061] In Examples No. 1-25 and Comparative Examples No. 1-30 of the present invention, the solidified portion of the layer was cooled after the time (50-335 s) indicated in the "Time from layering to start of cooling" column of Tables 3 and 4. Cooling was performed using a movable cooling nozzle, which was continuously moved from the lower layer to the upper layer so that the solidified portion was cooled after the "Time from layering to start of cooling" had elapsed. The cooling rate was varied up to 600°C or less by air cooling (average 5°C / s), forced air cooling using an air nozzle (average 5°C / s to 50°C / s), and water cooling using a water cooling nozzle (average 50°C / s to 100°C / s), as indicated in the "Average Cooling Rate" column of Table 3. Air cooling was not performed. In addition, during cooling, a cover was provided to prevent air or water from the air nozzle or water cooling nozzle from hitting the welded portion in the upper direction. The temperature progression of the laminated structure at the relevant location during cooling was measured using infrared thermography (thermal imaging camera) to determine the average cooling rate from the temperature history. In Invention Examples No. 26, 27 and Comparative Examples No. 31, 32, the entire model was rapidly cooled by water cooling (100°C / s) after the additive manufacturing was completed and the time specified in Tables 3 and 4, "Time from stacking to start of cooling," had elapsed since the start of additive manufacturing. Therefore, in Invention Examples No. 26, 27 and Comparative Examples No. 31, 32, the portion of the first layer manufactured by additive manufacturing was cooled after the time specified in the "Time from stacking to start of cooling" column of Table 3 (300-700 s).

[0062] After the additive manufacturing process was completed, the outer, inner, and top surfaces were machined to create a cylindrical shape with an outer diameter of 67 mm, an inner diameter of 63 mm, and a height of 30 mm. Penetrant testing was then performed to check for cracks. The results were evaluated as follows: ◎ for no cracks, ○ for two or fewer cracks, and × for more than two cracks, and recorded in the "Crack Evaluation" column. In this example, the cracks were either ◎ or ○.

[0063] Next, a portion of the cylindrical object was embedded in the longitudinal section and mirror-polished, and the hardness distribution in the height direction was measured. The Hv hardness (1 kgf) at the center of the cross-section was measured at 0.5 mm intervals from the bottom 0.1 mm to the top surface, and the lowest hardness was recorded in the "Lowest Hardness" column of Table 3. In this invention example, Hv ≥ at all locations in the measured cross-section. 400 That was the case.

[0064] The mirror-polished surface was etched with aqua regia to clearly indicate the lamination interface 5 by macroscopic etch contrast, and the number of layers and the average lamination pitch were calculated. In this example, the average lamination pitch, which is the spacing between layers, was 2 mm or less.

[0065] A plate measuring 30 mm in width and 25 mm in height was cut from the cylindrical object, and after polishing the entire surface with #500 grit sandpaper, a neutral salt spray test according to JIS Z 2371 was conducted for 3 days to evaluate the degree of rust formation. The degree of rust formation was classified into no rust, spot rust formation, and flow rust formation, and is recorded in the "Rust Formation Level" column of Table 3. In the present invention example, the level was no rust formation and spot rust formation.

[0066] Examples No. 1 to 27 of the present invention in Table 3 have component compositions and D values ​​in equation (1) within the range of the present invention. As a result of applying the manufacturing method of the additively fabricated product of the present invention, no cracks occurred, the hardness was Hv ≥ 400, and the rust resistance was also good.

[0067] Comparative Examples No. 1 to 32 in Table 4 are comparative examples. Comparative Example No. 1 had C outside the lower limit, while Nos. 5, 9, and 11 had Mn, Ni, and Cr outside the upper limit, and their hardness outside the lower limit.

[0068] Comparative Examples No. 2-4, 6, 8, 9, and 15-25 each had a D value outside the lower limit, or one of the elements Si, P, S, Cu, N, B, Ti, Ni, V, O, Ta, Ca, Mg, REM, or Zr outside the upper limit, resulting in cracking and poor rust resistance.

[0069] Comparative Example No. 10 had Cr outside the lower limit, No. 13 had Al outside the upper limit, and No. 14 had D outside the higher limit, all exhibiting poor rust resistance. No. 12 had Mo outside the upper limit, resulting in cracking.

[0070] In comparative examples No. 26 and 29, the interval between layers was too long, resulting in an excessively large layer pitch and causing cracking. In comparative examples No. 27 to 32, the cooling conditions after lamination were outside the scope of the present invention, resulting in poor rust resistance. In comparative examples No. 31 and 32, cracking also occurred. [Explanation of Symbols]

[0071] 1. Additive-formed product 2 circuit boards 3. Welded material 4 Laminated surface 5 Lamination interface 6 layers 11 Welding direction 12 Lamination direction

Claims

1. A method for manufacturing additively manufactured products by arc welding using stainless steel wire as a welding material, The composition of the aforementioned solubilant is, in mass%, C: 0.10-0.35%, Si ≤ 3.0%, Mn ≤ 5.0%, S ≤ 0.03%, P ≤ 0.05%, Cr: 11.5-17%, N ≤ 0.15%, O ≤ 0.015%, with the remainder being Fe and impurities, and the D value defined by the following formula (1) is 0-10. A method for manufacturing a high-hardness, high-corrosion-resistant additively manufactured product, characterized in that the time between stacking any layer of the additively manufactured product and stacking the layer above it (hereinafter referred to as the "inter-stack interval") is 60 seconds or less, and after two or more layers have been stacked on the arbitrary layer, the layer is cooled to 600°C or less at an average cooling rate of more than 20°C / s within 600 seconds after stacking the arbitrary layer, and the stack spacing is 2.5 mm or less. D=Cr+1.2Mo+0.5Si+2.5Al+10Ti+5Nb+3V-25C-18N-Ni-0.1Mn-4 (1) (1) In equation (1), the element symbol represents the content (mass %) of that element in the solubilant.

2. A method for manufacturing a high-hardness, high-corrosion-resistant additively manufactured product according to claim 1, characterized in that the cooling described in the preceding paragraph is water-cooled.

3. A method for manufacturing a high-hardness, high-corrosion-resistant additively manufactured product according to claim 1 or claim 2, A method for manufacturing high-hardness, high-corrosion-resistant additively manufactured products, characterized by completing additive manufacturing within 600 seconds after the start of additive manufacturing, and then water-cooling the entire layer within 600 seconds after the start of additive manufacturing.

4. The method for manufacturing a high-hardness, high-corrosion-resistant additively manufactured product according to any one of claims 1 to 3, characterized in that the composition of the solvent further contains, in addition by mass%, one or more of the following in place of a portion of the Fe: Cu ≤ 3.5%, Ni ≤ 5%, Mo ≤ 3.0%, Al ≤ 2.0%, B ≤ 0.01%, Ti ≤ 0.5%, Nb ≤ 1.0%, V ≤ 1.0%, Co ≤ 3.0%, W ≤ 2.0%, Ta ≤ 1.0%, Ca ≤ 0.01%, Mg ≤ 0.01%, REM ≤ 0.1%, and Zr ≤ 0.1%.

5. The composition, in mass%, contains C: 0.10-0.35%, Si ≤ 3.0%, Mn ≤ 5.0%, S ≤ 0.03%, P ≤ 0.05%, Cr: 11.5-17%, N ≤ 0.15%, O ≤ 0.015%, with the remainder being Fe and impurities, and the D value, as defined by the following formula (1), is between 0 and 10. It is made up of multiple layers that are layered together. A high-hardness, high-corrosion-resistant additively manufactured product characterized by a minimum hardness of Hv ≥ 400 at the center of the cross-section, no flow rust occurring after a 3-day JIS salt spray test following surface polishing with #500 grit, and a layer spacing of 2.5 mm or less. D=Cr+1.2Mo+0.5Si+2.5Al+10Ti+5Nb+3V-25C-18N-Ni-0.1Mn-4 (1) In equation (1), the element symbol represents the content (mass %) of that element in the additively manufactured product.

6. The high-hardness, high-corrosion-resistant additively manufactured product according to claim 5, characterized in that the composition further contains, in mass%, one or more of the following in place of a portion of the Fe: Cu ≤ 3.5%, Ni ≤ 5%, Mo ≤ 3.0%, Al ≤ 2.0%, B ≤ 0.01%, Ti ≤ 0.5%, Nb ≤ 1.0%, V ≤ 1.0%, Co ≤ 3.0%, W ≤ 2.0%, Ta ≤ 1.0%, Ca ≤ 0.01%, Mg ≤ 0.01%, REM ≤ 0.1%, and Zr ≤ 0.1%.

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