Manufacturing method of additively manufactured product and additively manufactured product

Abstract

To provide a manufacturing method for a laminated shaped article constituted of two kinds of material, in which martensitic stainless steel material is three dimensionally shaped by being deposited and laminated using a metal wire, the method enabling hardness and hardness variation of a laminated shaped martensitic stainless steel to be satisfactorily held.SOLUTION: In three-dimensionally lamination-forming of an article by arc-welding, using a melting material made of a martensitic stainless steel wire, an inter-lamination interval during which an arbitrary layer of a laminated shaped layer 21 is laminated and then a layer on the arbitrary layer is laminated is set to be 60 seconds or less, and the arbitrary layer is cooled down to 900-300°C at a cooling speed of an average 1°C / s or higher, and then a laminated shaped layer 22 is three-dimensionally formed at head speeds of 5 mm / s-100 mm / s by arc welding using a melting material made of second materials so that the layer is adjacent to the already formed laminated shaped layer 21 and is cooled down to 500°C or lower at a cooling rate of over 20°C / s within 100 seconds after a site of the layer is molded.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an additively manufactured product, which is produced three-dimensionally by arc welding using a stainless steel wire melting material, and to an additively manufactured product, and in particular to an additively manufactured product made of two types of material. [Background technology]

[0002] In recent years, metal 3D printers have been expected to be a revolutionary production technology, and various techniques have been proposed. The main technical methods proposed are those using metal powder and those using metal wire. When using metal wire, for example, a method has been disclosed in which metal wire welding beads are layered to form three-dimensional parts (Patent Document 1). Also, a manufacturing method has been disclosed in which stainless steel metal wire is welded by controlling arc or plasma and layered in three dimensions (Patent Document 2).

[0003] Patent Document 3 discloses a manufacturing method for a 3D printer that uses metal wire welding and lamination to create three-dimensional shapes. The transformation temperature of the metal structure is controlled to adjust the composition so that a low C and N martensite structure always appears, and the stainless steel metal wire has excellent heat resistance (thermal deformation resistance), material quality, metal structure uniformity, internal crack resistance, and internal void resistance.

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

[0005] Patent Document 5 proposes a parallel multi-wire welding system for improving the productivity of metal 3D manufacturing as a method and system for near-net-shape additive manufacturing with a hybrid deposition rate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-266174 [Patent Document 2] Japanese Patent Application Publication No. 2018-507317 [Patent Document 3] Japanese Patent Publication No. 2020-147785 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-83778 [Patent Document 5] Japanese Patent Application Publication No. 2018-187679 Summary of the Invention [Problem to be solved by the invention]

[0007] The material properties required for one surface and the other surface of a metal component may differ. For example, the inner surface of a cylindrical component in an automobile high-pressure pump is the surface that contacts and slides with other components and is required to have high hardness, while the outer surface is required to have high corrosion resistance. It may be difficult to achieve both high hardness and high corrosion resistance with a single material, or the material may be expensive. In such cases, it would be effective to construct the inner and outer surfaces of the component from different materials, using a material with high hardness for the inner surface and a material with high corrosion resistance for the outer surface, while using inexpensive materials for each.

[0008] When manufacturing a component whose inner and outer surfaces are made of different materials, it is preferable if at least one of the materials, which has high hardness, can be 3D shaped by welding and laminating with a metal wire.

[0009] The present invention aims to provide an additively manufactured product that is composed of two types of materials, in which at least one of the materials, martensitic steel, is 3D-manufactured by welding and laminating with a metal wire, and a manufacturing method for the additively manufactured product that can effectively maintain the hardness and hardness variation of the martensitic steel additively manufactured layer. [Means for solving the problem]

[0010] That is, the gist of the present invention is as follows. [1] A martensitic stainless steel containing, by mass%, C: 0.10 to 0.35%, Si≦3.0%, Mn≦5.0%, S≦0.03%, P≦0.05%, Cr: 10 to 17.5%, N≦0.15%, O≦0.015%, with the balance being Fe and impurities is used as a first material; When performing three-dimensional additive manufacturing by arc welding using a stainless steel wire melting material made of the first material, the time from stacking any layer of the additive manufacturing layer to stacking the layer above it (hereinafter referred to as the "inter-layer interval") is 60 seconds or less, and after arc welding, the material is cooled to 700 to 300 ° C. at an average cooling rate of 1 ° C. / s or more, Then, a welding material made of a second material with a different chemical composition from the first material is used to perform three-dimensional additive manufacturing adjacent to the already-formed additive manufacturing layer of the first material by arc welding at a head speed of 5 mm / s to 100 mm / s, and cooling of the area is started within 100 seconds after welding, and after the start of cooling, the material is cooled to 500°C or below at an average cooling rate of more than 20°C / s. [2] The method for manufacturing an additive manufactured product according to [1], wherein an object made of the first material is formed, and then three-dimensional additive manufacturing is performed by arc welding using a welding material made of the second material at a head speed of 5 mm / s to 100 mm / s, wherein the three-dimensional additive manufacturing is performed while rotating the layered structure so as to achieve a head speed of 5 mm / s to 100 mm / s and tilting it at an angle of 20° or more from the horizontal or vertical direction, and wherein during the arc welding of the second material, part of the layered structure is immersed in cooling water in a water tank to be intermittently cooled during the additive manufacturing.

[0011] [3] A martensitic stainless steel containing, by mass%, C: 0.10 to 0.35%, Si≦3.0%, Mn≦5.0%, S≦0.03%, P≦0.05%, Cr: 10 to 17.5%, N≦0.15%, O≦0.015%, with the balance being Fe and impurities is used as a first material; forming a shaped object using a second material having a component composition different from that of the first material; Then, when three-dimensional additive manufacturing is performed by arc welding using a stainless steel wire melting material made of the first material adjacent to the object, the time between stacking any layer of the additive manufacturing layers and stacking the layer above it (hereinafter referred to as the "inter-layer interval") is set to 60 seconds or less, and after arc welding, the temperature is cooled to 700 to 300°C at an average cooling rate of 1°C / s or more. [4] A method for manufacturing an additively manufactured product according to [3], characterized in that when forming an object using the second material, three-dimensional additive manufacturing is performed by arc welding using a welding material made of the second material.

[0012] [5] A method for producing an additive manufacturing product according to any one of [1] to [4], characterized in that the first material 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 portion of the Fe. [6] A method for manufacturing an additive manufacturing product described in any one of [1] to [5], characterized in that the second material is made of ferritic stainless steel or austenitic stainless steel.

[0013] [7] A martensitic stainless steel containing, by mass%, C: 0.10 to 0.35%, Si≦3.0%, Mn≦5.0%, S≦0.03%, P≦0.05%, Cr: 10 to 17.5%, N≦0.15%, O≦0.015%, with the balance being Fe and impurities is used as a first material; an additive manufacturing layer is formed that is made up of a plurality of layers made of the first material, and a molded object made of a second material having a component composition different from that of the first material is formed adjacent to the additive manufacturing layer; An additive manufacturing product characterized in that the hardness of the additive manufacturing layer made of the first material from the surface layer to a depth of 3 mm is Hv≧400, the hardness variation ΔHv≦100, and the stacking spacing of the additive manufacturing layer is 2.5 mm or less. [8] The additive manufacturing product described in [7], characterized in that the product manufactured using the second material is made up of multiple additive manufacturing layers. [9] The additive manufacturing product according to [7] or [8], characterized in that the first material 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 portion of the Fe.

[10] An additive manufacturing product described in any one of [7] to [9], characterized in that the second material is made of ferritic stainless steel or austenitic stainless steel. [Effects of the Invention]

[0014] The present invention relates to a method for manufacturing an additively manufactured product made of two types of materials, in which at least one of the materials has a high hardness and is three-dimensionally manufactured by welding and layering using a metal wire.By optimizing the layering method in the additively manufactured product and the manufacturing method, it is possible to achieve quality with sufficient hardness and little hardness variation in the high-hardness additively manufactured layer. [Brief explanation of the drawings]

[0015] [Figure 1] 1A and 1B are diagrams showing an additive manufacturing product, in which (A) shows the stage where an inner additive manufacturing layer has been formed, and (B) shows the stage where both the inner and outer layers have been additively manufactured. [Figure 2] 1A and 1B are diagrams showing an additively manufactured product, in which (A) shows the stage where an inner layer of the product has been formed, and (B) shows the stage where an outer layer has been further formed by additive manufacturing. [Figure 3]1A and 1B are diagrams showing an additive manufacturing product, in which (A) shows the stage where an inner additive manufacturing layer has been formed, and (B) shows the stage where both the inner and outer layers have been additively manufactured. [Figure 4] FIG. 10 is a perspective view showing an example of a method for additively manufacturing an outer layer after forming an inner additively manufactured layer of an additively manufactured product. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention relates to a method for manufacturing an additively manufactured product and an additively manufactured product in which a component is composed of two materials in the thickness direction, one of which is additively manufactured using a high-hardness martensitic stainless steel material (hereinafter referred to as the "first material"), and the other of which is composed of another material (hereinafter referred to as the "second material"), as shown in each of Figures 1 to 3 (B). In the method for manufacturing an additively manufactured product of the present invention, in the "high-hardness material prior manufacturing" shown in Figure 1, additive manufacturing is first performed using the first material to form additively manufactured layer 21 (Figure 1 (A)), and then additive manufacturing is performed using the second material adjacent to additively manufactured layer 21 to form additively manufactured layer 22 (Figure 1 (B)). In addition, in the "high-hardness material-first manufacturing" shown in Figures 2 and 3, a method can be used in which a model 32 made of a second material is first formed (Figures 2(A) and 3(A)), and then a model layer 31 is formed adjacent to the model 32 by additive manufacturing using a first material (see Figures 2(B) and 3(B)). In high-hardness material-first manufacturing, additive manufacturing is performed first to manufacture the first material (see Figure 1(A)), and then additive manufacturing is also used to manufacture the second material (see Figure 1(B)). On the other hand, in high-hardness material-first manufacturing, a model formed by a separate method such as rolling or pipe-making can be used for the preceding manufacturing method of the second material (see Figure 2(A)), or an additive manufacturing layer 32A can be produced by additive manufacturing using the second material (see Figure 3(A)).

[0017] The present invention is particularly suitable for use when the additively manufactured product 1 is a cylindrical member whose inner and outer surfaces are made of different materials, one of which has high hardness. Hereinafter, the additively manufactured product 1 will be exemplified as a cylindrical member, with the one whose inner surface has high hardness being referred to as an "inner surface high-hardness additively manufactured product 1A" and the one whose outer surface has high hardness being referred to as an "outer surface high-hardness additively manufactured product 1B."

[0018] For the high-hardness inner-surface additively manufactured product 1A, the aforementioned high-hardness material pre-manufacturing is used, and both the inner and outer surfaces are formed by additive manufacturing. First, the high-hardness portion on the inner surface is additively manufactured to form additively manufactured layer 21 (see FIG. 1(A)), and then a different material on the outer surface is additively manufactured to form additively manufactured layer 22 (see FIG. 1(B)).

[0019] On the other hand, for the outer surface high-hardness additively manufactured product 1B, high-hardness material-assisted manufacturing is adopted, where the inner surface-side molded object 32 is made of a material other than the high-hardness material, and then the outer surface-side high-hardness portion is additively manufactured. In this case, the inner surface-side molded object 32 may be manufactured by additive manufacturing as described above (see FIG. 3(A)), or a material formed by a method other than additive manufacturing may be used (see FIG. 2(A)).

[0020] Here, an example in which a first material is first subjected to additive manufacturing will be described with reference to FIG. 1(A). In additive manufacturing, as described in Patent Documents 3 and 4, an additive manufacturing layer 21 can be formed by deposition additive manufacturing using a metal 3D printer that uses a metal wire as a welding material. For example, a robotic MIG arc welder is used to repeatedly weld a stainless steel wire as a welding material while continuously stacking it in a spiral shape, and the layers are stacked in the stacking direction 12 shown in FIG. 1(A), thereby performing three-dimensional manufacturing and producing an additive manufacturing layer 21 consisting of a hollow cylinder as shown in FIG. 1(A).

[0021] Here, we define the "layering direction 12" in additive manufacturing. In a coordinate system fixed to the molded product, the movement direction of the welding machine is the welding direction 11, and the welded material 3 is arranged linearly in the welding direction 11 to form layer 6. The linear layer 6 (welded material 3) that has already been welded is further welded repeatedly. In the case shown in Figure 1(A), a new welded material 3 is formed on top of the previously welded welded material 3. By sequentially repeating this process, 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 manufacturing layer 21 is usually formed in a "plane" shape, and this plane is called the "layering plane 4" here. In the example shown in Figure 1(A), the layering plane 4 forms a cylindrical surface. Both the welding direction 11 and the layering direction 12 are parallel to the layering plane 4, and the layering direction 12 is perpendicular to the welding direction 11.

[0022] Qualities that an AM layer made of the first material should have The AM layers made of the first material are characterized by a hardness of Hv≧400, a hardness variation ΔHv≦100, and a stacking interval of 2 mm or less. Here, the hardness variation ΔHv refers to the variation in Hv hardness from the surface of the first material to a depth of 3 mm. It refers to the difference in Hv hardness ΔHv obtained by subtracting the minimum Hv hardness from the maximum Hv hardness measured at 10 or more arbitrary positions 3 mm deep from the surface. Note that positions deeper than 3 mm from the surface were excluded from hardness measurement because they are significantly affected by heat during AM of the second material.

[0023] <Composition of the first material> The composition of the first material will be explained. % means mass %. The steel having the following composition is a medium-carbon martensitic stainless steel. First, the essential components will be described.

[0024] (C: 0.10 to 0.35%) C is added in an amount of 0.10% or more to ensure a uniform hardness of Hv≧400. On the other hand, if the content exceeds 0.35%, it becomes difficult to suppress cracking, so the upper limit is set to 0.35%, and the preferred range is 0.15 to 0.30%.

[0025] (Si≦3.0%) Silicon is effective for deoxidation during welding, and is preferably added in an amount of 0.1% or more. However, excessive addition of more than 3.0% promotes the precipitation of intermetallic compounds during additive manufacturing, which can lead to cracking, so the upper limit is set at 3.0%. Preferably, it is 1.0% or less. Silicon need not be present.

[0026] (Mn≦5.0%) Mn is effective for deoxidation during welding, and is preferably added in an amount of 0.1% or more. However, if added in excess of 5.0%, the austenite structure becomes stable, making it difficult to harden, and a stable Hv≧400 cannot be obtained, so the upper limit is set to 5.0%, and preferably 1.5% or less. Mn does not necessarily need to be added.

[0027] (S≦0.03%) S is contained as an impurity. S ensures a suitable flow of molten metal during welding, improving the accuracy of the laminated shape and improving subsequent machining such as cutting. However, excessive addition of more than 0.03% promotes cracking, so the upper limit is set to 0.03%. Preferably, it is 0.005% or less.

[0028] (P≦0.05%) P is contained as an impurity. To suppress internal cracking during molding, the P content is limited to 0.05% or less, preferably 0.03% or less.

[0029] (Cr: 10-17.5%) Cr is added in an amount of 10% or more to ensure corrosion resistance, but if it exceeds 17.5%, the amount of austenite formed increases and it becomes difficult to stably obtain Hv≧400, so the upper limit is set to 17.5%, and preferably 11 to 16%.

[0030] (N≦0.15%) N is contained as an impurity. In order to ensure a uniform hardness of Hv≧400, N is preferably added in an amount of 0.01% or more together with C. On the other hand, if the N content exceeds 0.15%, it becomes difficult to suppress defects such as bubbles and cracks, so the upper limit is set to 0.15%. Preferably, it is 0.11% or less.

[0031] (O≦0.015%) O is contained as an impurity. O ensures a moderate fluidity during welding and improves the accuracy of additive manufacturing. However, if the O content exceeds 0.015%, it becomes difficult to prevent cracks originating from large oxides, etc., so the upper limit is set to 0.015%. Preferably, O is 0.010% or less.

[0032] The components of the welding material used in the method for producing a high-hardness, high-corrosion-resistant additive manufacturing product of the present invention, and the composition of the high-hardness, high-corrosion-resistant additive manufacturing product, contain the above-mentioned essential components, with the remainder being Fe and impurities. One or more of the following components may be further contained in place of a portion of the Fe.

[0033] (Cu≦3.5%) Cu may be added as needed to improve the toughness and corrosion resistance of the matrix, but if it exceeds 3.5%, it promotes cracking, so the upper limit is set to 3.5%. It is preferably 1.5% or less. If it is less than 0.1%, it is at the level of an unavoidable impurity.

[0034] (Ni≦5%) Ni may be added as needed to improve the toughness and corrosion resistance of the matrix, but if it exceeds 5%, austenite is formed and a stable Hv≧400 cannot be obtained, so the upper limit is set to 5%. It is preferably 0.06 to 1.5%. Less than 0.1% is at the level of an unavoidable impurity.

[0035] (Mo≦3.0%) Mo may be added as needed to improve the corrosion resistance of the matrix, but if it exceeds 3.0%, cracking will be promoted, so the upper limit is set to 3.0%, preferably 2.5% or less. If it is less than 0.1%, it is at the level of an unavoidable impurity.

[0036] (Al≦2.0%) Al is effective for deoxidation during additive manufacturing, so it may be added as needed, but if it exceeds 2.0%, it promotes cracking, so the upper limit is set to 2.0%. It is preferably 0.5% or less. If it is less than 0.005%, it is at the level of an unavoidable impurity.

[0037] (B≦0.01%) B may be added as needed to improve the toughness of the matrix, but if it exceeds 0.01%, it promotes cracking, so the upper limit is set to 0.01%. It is preferably 0.008% or less. If it is less than 0.001%, it is at the level of an unavoidable impurity.

[0038] (Ti≦0.5%) Ti may be added as needed to improve the corrosion resistance of the matrix, but if it exceeds 0.5%, coarse precipitates are formed, promoting cracking, so the upper limit is set to 0.5%. It is preferably 0.3% or less. If it is less than 0.01%, it is at the level of an unavoidable impurity.

[0039] (Nb≦1.0%) Nb may be added as needed to improve the corrosion resistance of the matrix, but if it exceeds 1.0%, coarse precipitates are formed, promoting cracking, so the upper limit is set to 1.0%. It is preferably 0.6% or less. If it is less than 0.01%, it is an unavoidable impurity.

[0040] (V≦1.0%) V may be added as needed to improve the corrosion resistance of the matrix, but if it exceeds 1.0%, coarse precipitates are formed, promoting cracking, so the upper limit is set to 1.0%. It is preferably 0.6% or less. If it is less than 0.01%, it is an unavoidable impurity.

[0041] (Co≦3.0%) Co may be added as needed to improve the toughness and corrosion resistance of the matrix, but if it exceeds 3.0%, austenite is formed and a stable Hv of 400 or more cannot be obtained, so the upper limit is set at 3.0%. If it is less than 0.1%, it is at the level of an unavoidable impurity.

[0042] (W≦2.0%) W may be added as needed to improve the corrosion resistance of the matrix, but if it exceeds 2.0%, cracking will be promoted, so the upper limit is set at 2.0%. If it is less than 0.1%, it is at the level of an unavoidable impurity.

[0043] (Ta≦1.0%) Ta may be added as needed to improve the corrosion resistance of the matrix, but if it exceeds 1.0%, coarse precipitates are formed, promoting cracking, so the upper limit is set at 1.0%. If it is less than 0.01%, it is an unavoidable impurity.

[0044] (Ca≦0.01%) Ca is effective for deoxidation during additive manufacturing, so it may be added as needed, but if it exceeds 0.01%, it promotes cracking, so the upper limit is set at 0.01%. If it is less than 0.001%, it is at the level of an unavoidable impurity.

[0045] (Mg≦0.01%) Mg is effective for deoxidation during additive manufacturing, so it may be added as needed, but if it exceeds 0.01%, it promotes cracking, so the upper limit is set at 0.01%. Less than 0.001% is at the level of an unavoidable impurity.

[0046] (REM≦0.1%) REM is effective for deoxidation during additive manufacturing, so it may be added as needed, but if it exceeds 0.1%, it promotes cracking, so the upper limit is set at 0.1%. Less than 0.001% is at the level of an unavoidable impurity.

[0047] (Zr≦0.1%) Zr is effective for corrosion resistance and deoxidation during additive manufacturing, so it may be added as needed, but if it exceeds 0.1%, it promotes cracking, so the upper limit is set at 0.1%. Less than 0.001% is at the level of an unavoidable impurity.

[0048] The second ingredient The second material can be selected depending on the properties required of the second material. The second material is preferably a ferritic stainless steel, austenitic stainless steel, precipitation hardened stainless steel, or austenitic-ferritic stainless steel with a composition specified in JIS G 4303, 4304, or 4308. The second material is preferably a stainless steel with corrosion resistance and heat resistance similar to that of the first material, but carbon steel or high-alloy steel may also be used. Ferritic stainless steel and precipitation hardened stainless steel are suitable as the second material because of their low thermal expansion coefficients.

[0049] <<Manufacturing method for additive manufacturing products>> A metal 3D printer using a metal wire as a welding material can be used to form an additive manufacturing layer by deposition. For example, a robotic MIG arc welder is used, and a stainless steel wire is used as the welding material. The welding machine is moved in the welding direction 11 at a head speed V (mm / s), and the layers are repeatedly welded while continuously stacking in a spiral shape. By stacking in the stacking direction 12 shown in Figure 1(A), 3D modeling can be performed to produce an additive manufacturing layer 21 consisting of a hollow cylinder (diameter D (mm)) as shown in Figure 1(A) on a substrate 2.

[0050] In any of the cases shown in Figures 1 to 3, the cooling rate of any layered portion of the additive manufacturing layers (21, 22, 31) can be measured by measuring the surface temperature non-contact using a measuring device such as a thermoviewer.

[0051] <<Manufacturing method for high-hardness material pre-molding>> In the method for manufacturing an additively manufactured product of the present invention, additive manufacturing using a first material is first performed, followed by molding using a second material (high-hardness material-first manufacturing). When the additively manufactured product is a cylindrical member, this method is suitable for use in an "internal high-hardness additively manufactured product 1A" in which the inner surface has high hardness. Note that the first manufactured product using the first material may be formed not by additive manufacturing, but by a separate method such as rolling or pipe-making, and may be a high-hardness (Hv≧430) manufactured product that has been quenched (900-1200°C) and tempered (500°C or less).

[0052] Three-dimensional additive manufacturing (AM) is performed by arc welding using a stainless steel wire melt made of the first material to form the AM layer 21 shown in FIG. 1(A). The time T (s) between the deposition of a given layer of the AM layer 21 and the deposition of the layer above it is referred to as the "inter-layer interval T." If the inter-layer interval T is too long, the time between the deposition of a given layer and the deposition of the layer above it will be too long, resulting in excessive cooling of the layer before reheating, leading to increased non-uniformity in the temperature history and a tendency for the hardness variation to deviate from ΔHv≦100. In contrast, setting the inter-layer interval T to 60 s or less will result in a uniform temperature history, enabling the AM layer to achieve a hardness variation of ΔHv≦100. It is more preferable for the inter-layer interval T to be 30 s or less.

[0053] When the additive manufacturing layer is cylindrical, the interlayer interval T (s) is determined between the circumference L (mm) of the additive manufacturing layer and the head speed V (mm / s) of the welding machine. T=L / V Therefore, by adjusting the head speed V (mm / s) of the welding machine according to the circumference L (mm) of the additive manufacturing layer, the inter-layer interval T (s) can be adjusted to within the target time.

[0054] As described below, it is preferable that the lamination interval of the additive manufacturing layers 21 be 2.5 mm or less. The lamination interval is determined by the ratio of the welding material supply speed to the head speed. If the lamination interval T is long due to a slow head speed V, and the welding material supply speed is not sufficiently reduced to correspond to the slow head speed V, the lamination interval of the additive manufacturing layers may fall outside the preferable range of 2 mm or less, which may result in quality defects. Details will be described later.

[0055] When stacking any layer of the additive manufacturing layer, the stacking location is cooled after arc welding to 700 to 300°C at an average cooling rate of 1°C / s or more. By cooling at such a cooling rate, the additive manufacturing layer 21 made of the first material can have a hardness of Hv≧400 and a hardness variation of ΔHv≦100.

[0056] After forming an additive manufacturing layer 21 made of a first material and cooling it as described above, additive manufacturing is performed by arc welding using a welding material made of a second material with a different chemical composition from the first material, so that the additive manufacturing layer 22 is formed adjacent to the already-formed additive manufacturing layer 21 made of the first material.

[0057] When additive manufacturing the second material, three-dimensional additive manufacturing is performed at a head speed of 5 mm / s to 100 mm / s. Head speed refers to the relative speed between the welding head and the workpiece during arc welding. By performing welding at a head speed of 5 mm / s or more, it is possible to prevent the first material from excessively heating up during the welding of the second material in the additive manufacturing layer 21 made of the first material, which has already been welded, and to achieve a hardness of Hv≧400 and a hardness variation of ΔHv≦100. A head speed exceeding 100 mm / s can cause defective manufacturing.

[0058] Cooling is started within 100 seconds after welding of the portion where the second material is welded, and after cooling starts, cooling is performed at an average cooling rate of more than 20°C / s until the temperature reaches 500°C or below. By cooling for such a time until cooling starts and at such a cooling rate, it is possible to prevent the first material from excessively increasing in temperature when the second material is welded in the additive manufacturing layer 21 made of the first material, which has already been welded, and to achieve a hardness of Hv≧400 and a hardness variation of ΔHv≦100.

[0059] Here, we will describe a suitable method for additive manufacturing of a second material in the above-mentioned method for manufacturing an internally high-hardness additive manufactured product 1A by the high-hardness material prior manufacturing method. First, for the additive manufacturing of the first material, a stainless steel wire melting material made of the first material is used, and additive manufacturing is performed in three dimensions by arc welding using the method described above to form an additive manufacturing layer 21 as shown in Figure 1(A). Next, as shown in FIGS. 4(A) and 4(B), the manufactured additive manufacturing layer 21 is immersed in cooling water 9 in a water tank 8. In the example shown in FIG. 4(A), the central axis of the additive manufacturing layer 21 is horizontal, while in the example shown in FIG. 4(B), the central axis of the additive manufacturing layer 21 is tilted at an angle θ with respect to the vertical direction. Then, using a welding material of the second material, the additive manufacturing layer 21 is three-dimensionally manufactured by rotating the layered structure in a rotation direction 13 as shown in FIG. 4 so as to achieve a head speed of 5 mm / s to 100 mm / s by arc welding 7, while tilting the layered structure in the horizontal direction (FIG. 4(A)) or at an angle θ of 20° or more with respect to the vertical direction (FIG. 4(B)). Furthermore, a portion of the structure is immersed in the cooling water 9 in the water tank 8 and intermittently cooled while being additively manufactured to form the additive manufacturing layer 22, thereby enabling efficient cooling.

[0060] When the additive manufacturing product 1 is a cylindrical member, in the case of a "high-internal-hardness additive manufacturing product" (see Figure 1) in which the inner surface has high hardness, the above-mentioned manufacturing method can be preferably used to perform three-dimensional additive manufacturing by arc welding using a welding material made of stainless steel wire made of a first material to form additive manufacturing layer 21, and then perform three-dimensional additive manufacturing by arc welding using a welding material made of a second material on the outside of the already-formed additive manufacturing layer of the first material, adjacent to additive manufacturing layer 21.

[0061] <<Manufacturing method for high-hardness material post-molding>> In the method for manufacturing an additively manufactured product of the present invention, a method (high-hardness material subsequent manufacturing) is described in which an additively manufactured object 32 is first formed using a second material, and then an additively manufactured layer 31 is formed using a first material. When the additively manufactured product 1 is a cylindrical member, this method can be suitably used for a "high-hardness outer surface additively manufactured product 1B" whose outer surface has high hardness (see FIGS. 2 and 3).

[0062] First, a shaped object 32 is formed using a second material with a different chemical composition from the first material. As described above, the shaping method for the second material prior to the additive manufacturing of the first material may use a shaped object 32 formed by a separate method such as rolling or pipe making (see FIG. 2), or may produce an additive manufacturing layer 32A by additive manufacturing using the second material (see FIG. 3). Below, an explanation will be given based on FIG. 2, taking as an example a case where a steel pipe made by manufacturing a stainless steel thin plate is used as the shaped object 32 using the second material.

[0063] After forming a molded object 32 using the second material (Figure 2(A)), three-dimensional additive manufacturing is performed by arc welding using a stainless steel wire melting material made of the first material adjacent to the molded object 32, forming an additive manufacturing layer 31 (Figure 2(B)).

[0064] During additive manufacturing of the first material, the time between the deposition of any layer of the additive manufacturing layer 31 and the deposition of the layer above it (inter-layer interval T) is set to 60 seconds or less. Setting the inter-layer interval T to 60 seconds or less ensures uniform temperature history and achieves a hardness variation ΔHv≦100 for the additive manufacturing layer 31 made of the first material. It is more preferable for the inter-layer interval T to be 30 seconds or less. Note that if the inter-layer interval T is long due to a slow head speed V, or if the welding material supply rate is not sufficiently reduced in response to the slow head speed V, the layer spacing of the additive manufacturing layer 31 may fall outside the preferred range of 2.5 mm or less, resulting in quality defects. Details will be described later.

[0065] After arc welding, the material is cooled to 700-300°C at an average cooling rate of 1°C / s or more. By cooling at such a cooling rate, the additive manufacturing layer 31 made of the first material can have a hardness of Hv≧400 and a hardness variation of ΔHv≦100.

[0066] If the inter-layer interval and cooling rate of the additive manufacturing layer 31 of the first material are both outside the above-mentioned preferred ranges, the hardness variation ΔHv of the additive manufacturing layer made of the first material will fall outside the preferred range, and at the same time, the hardness Hv of the additive manufacturing layer made of the first material will fall outside the preferred range.

[0067] Additive manufacturing products The additively manufactured product 1 of the present invention uses a first material, which is martensitic stainless steel, and a second material having a different chemical composition from the first material. The additively manufactured layers (21, 31) are formed from multiple layers of the first material, and a molded object made of the second material having a different chemical composition from the first material is formed adjacent to the additively manufactured layers. The molded object is molded as additively manufactured layer 22 in the example shown in FIG. 1, object 32 in the example shown in FIG. 2, and additively manufactured layer 32A in the example shown in FIG. 3. The additively manufactured layers (21, 31) made of the first material have a hardness of Hv≧400, a hardness variation ΔHv≦100, and a layer spacing of 2.5 mm or less between the additively manufactured layers (21, 31). The above-described quality can be achieved by using a first material with the above-described chemical composition and manufacturing it according to the above-described manufacturing method. A layer spacing of 2.5 mm or less allows additive manufacturing at a uniform temperature, followed by uniform cooling, resulting in a uniform hardness distribution. The lamination interval is preferably 2.0 mm or less, and more preferably 1 mm or less.

[0068] The cooling rate of any laminated portion was measured by measuring the surface temperature without contact using a thermoviewer. [Example]

[0069] Steels with the chemical compositions shown in Tables 1 to 3 were melted in a 45 kg vacuum melting furnace and processed into steel bars with a diameter of 11 mm by hot forging and hot extrusion. These were then repeatedly drawn and annealed to form metal wires with a diameter of 1.2 mm, which were used as welding materials for MIG arc welding. The compositions shown in Tables 1 and 2 are martensitic stainless steels used as the first material, and the compositions shown in Table 3 are ferritic stainless steels used as the second material.

[0070] The arc welding conditions were as follows: shielding gas of Ar+3% oxygen, welding current 300A, arc voltage 20V, and wire feed rate 800cc / h.

[0071] [Table 1]

[0072] [Table 2]

[0073] [Table 3]

[0074] <<Pre-forming of high-hardness materials for inner surface high-hardness additive manufacturing products>> For an example of pre-fabrication of an internally high-hardness additive manufactured product using high-hardness material, the conditions shown in Tables 4 and 5 were used. First, using a robotic CMT arc welding machine, a metal wire prototyped from martensitic stainless steel with the chemical composition shown in Tables 1 and 2 was repeatedly welded while continuously stacking it in a spiral shape onto substrate 2 made of SUS420J1 series (13% Cr-0.2% C) steel plate (φ80 mm, 15 mm thick). By stacking in stacking direction 12 shown in Figure 1(A), a 20 mm high cylindrical shape (inner diameter 60 mm, outer diameter 70 mm) was 3D-fabricated to form additive manufacturing layer 21. The head speed of the arc welding machine was changed to vary the inter-layer interval from 5 to 80 seconds. The wire feed speed for arc welding was constant under the above basic conditions for Invention Examples 1 to 17 and 19 to 25 in Table 4 and Comparative Examples 1 to 23, 25, and 28 to 30 in Table 5, but was slower than the constant speed for Invention Example 18 in Table 4 and Comparative Examples 24, 26, and 27 in Table 5, thereby adjusting the layer pitch. After additive manufacturing, the parts were cooled to room temperature from 700°C to 300°C by natural cooling, forced air using an air nozzle, or water cooling using a water-cooled nozzle, with the average cooling rate varying from 0.5 to 100°C / s.

[0075] Next, a metal wire made from a prototype ferritic stainless steel material with the chemical composition shown in Table 3 was used to form the additive manufacturing layer 22 adjacent to the outer periphery of the martensitic stainless steel additive manufacturing layer 21 described above by 3D additive manufacturing, as shown in Figure 1(B). The head speed of the arc welder was varied from 3 to 70 mm / s. Cooling began 11 to 122 seconds after the buildup, and the area below that point was continuously cooled. The average cooling rate from the start of cooling to 500°C was varied by forced air cooling using an air nozzle (average 5 to 50°C / s, with flow rate adjustment) and water cooling using a water-cooled nozzle (average over 50 to 100°C / s) until the temperature reached 500°C or below. During cooling, a cover was provided to prevent the air and water from the air and water-cooled nozzles from hitting the welded area above. In this way, an additively manufactured product according to the present invention was formed. After that, in order to evaluate the additively manufactured product, the surface layer of the laminated portion of the martensitic stainless steel on the inner surface was machined entirely with a cutting depth of 1 mm.

[0076] [Table 4]

[0077] [Table 5]

[0078] <<Later manufacturing of high-hardness materials for externally high-hardness additive manufactured products>> For an example of an externally high-hardness additive manufacturing process using a high-hardness material, the conditions shown in Table 6 were used. As shown in Figure 2(A), a cylindrical object 32 (inner diameter 60 mm, outer diameter 70 mm, height 30 mm) made of ferritic stainless steel (chemical composition shown in Table 3) was placed on a substrate 2 made of SUS420J1 steel plate (φ80 mm, thickness 15 mm). Adjacent to the outer periphery, a metal wire made of a steel material with the chemical composition shown in Steel B in Table 1 was used for 3D additive manufacturing to form an additive manufacturing layer 31, as shown in Figure 2(B). The head speed of the arc welding machine was varied to adjust the interval between layers to 10 to 80 seconds. The wire feed speed for the arc welding process was adjusted according to the basic conditions described above for Example 26 and Comparative Example 32 in Table 6, but was adjusted for each level for the others, thereby adjusting the layer pitch accordingly. After lamination, the sheets were cooled by standing, forced air using an air nozzle, or water using a water-cooling nozzle, with the average cooling rate varying from 0.5 to 100°C / s from 700 to 300°C. In this way, an additively manufactured product according to the present invention was formed. After that, in order to evaluate the additively manufactured product, the surface layer of the outer martensitic stainless steel laminate was entirely machined with a cutting depth of 1 mm.

[0079] [Table 6]

[0080] <Evaluation of additively manufactured products> Next, a portion of the cylindrical object was embedded in a longitudinal section and mirror-polished, and the hardness was measured at five arbitrary locations on the surface of the additive manufacturing layer (21, 31) formed with the first material at depths of 1, 2, 3, and 4 mm from the cutting surface. Using the hardness at depths of 1 and 2 mm from the cutting surface, the minimum hardness is listed in the "Minimum Hv" column in Tables 4 to 6, and the ΔHv evaluated using the above method is listed in the "ΔHv" column. In the present invention example, the hardness of all measurement points up to a depth of 2 mm from the surface (3 mm from the surface of the molded product) was Hv≧400 and ΔHv≦100. On the other hand, the hardness of areas more than 2 mm from the cut surface (3 mm from the surface of the additive manufacturing product) was not stable.

[0081] The mirror-polished surface was etched with aqua regia to reveal the layer interface 5 by macroscopic etch contrast, and the number of layers and the average layer pitch were calculated. In the examples of the present invention, the average layer pitch, which is the distance between layers, was 2 mm or less.

[0082] In addition, the appearance was inspected to check for major defects such as cracks and bubbles, and the feasibility of industrial production was also investigated.

[0083] The results are shown in Tables 4 to 6. Tables 4 and 5 show the results of an example in which a high-hardness material was first used to fabricate an inner-surface high-hardness additively manufactured product.

[0084] Inventive Examples No. 1 to 25 in Table 4, the component compositions were within the range of the present invention, and as a result of applying the manufacturing method of the additive manufacturing product of the present invention, no cracks occurred, the hardness was Hv≧400, and the hardness variation ΔHv≦100.

[0085] Comparative Examples Nos. 1 to 30 in Table 5 are comparative examples. Comparative Example No. 1 had a C content outside the lower limit and a hardness outside the lower limit. Nos. 4, 8, and 10 had Mn, Ni, and Cr contents outside the upper limit, respectively, a hardness outside the lower limit, and ΔHv outside the lower limit. Comparative Examples 2, 3, 5 to 7, 11, 12, and 14 to 23 were outside the upper limits for any of C, Si, S, P, Cu, Mo, Al, B, Ti, Nb, V, O, Ta, Ca, Mg, REM, and Zr, resulting in cracking. Comparative Example No. 9 had a Cr content outside the lower limit and exhibited poor corrosion resistance, while Comparative Example No. 13 had an N content outside the upper limit and exhibited gas bubbles and cracks.

[0086] Among the additive manufacturing conditions for the inner layer, Nos. 24 and 27 had too long an interval between layers, resulting in a too large layer pitch and poor hardness and ΔHv. Comparative Example No. 26 had cooling conditions after layering that were outside the range of the present invention, resulting in poor hardness and ΔHv. Regarding the lamination conditions for the outer layer, No. 25 had a head speed that was too slow, No. 28 had a time until the start of cooling that was too long, and No. 29 had an average cooling rate that was too low, resulting in poor hardness and ΔHv. No. 30 had a head speed that was too fast and an average cooling rate that was too slow, resulting in poor molding and poor hardness and ΔHv.

[0087] Table 6 shows the results of an example in which a high-hardness outer surface additively manufactured product was manufactured using a high-hardness material. Inventive Examples Nos. 26 to 27 in Table 6, the component compositions were within the range of the present invention, and as a result of applying the manufacturing method of the additive manufacturing product of the present invention, no cracks occurred, the hardness was Hv≧400, and the hardness variation ΔHv≦100.

[0088] Comparative Examples Nos. 31 to 33 in Table 6 are comparative examples. Among the additive manufacturing conditions for the outer layer, No. 31 had an interval between layers that was too long, resulting in a layer pitch that was too large and poor ΔHv. Comparative Example No. 32 had a cooling rate after lamination that was outside the range of the present invention, resulting in poor hardness and ΔHv. Comparative Example No. 32 had an interval between layers that was too long, resulting in a large layer pitch, and a cooling rate after lamination that was outside the range of the present invention, resulting in poor hardness and ΔHv. [Explanation of symbols]

[0089] 1 Additive manufacturing products 1A High-hardness inner surface additive manufacturing product 1B External high hardness additive manufacturing product 2 boards 3 Welding material 4 Laminated surface 5 Lamination interface 6 layers 7. Arc welding 8. Aquarium 9 Cooling water 11 Welding direction 12 Lamination direction 13 Rotation direction 21 Additive Manufacturing Layers 22 Additive Manufacturing Layers 31 Additive Manufacturing Layers 32 Sculptures 32A Additive Manufacturing Layer

Claims

1. A martensitic stainless steel containing, by mass%, C: 0.10 to 0.35%, Si≦3.0%, Mn≦5.0%, S≦0.03%, P≦0.05%, Cr: 10 to 17.5%, N≦0.15%, O≦0.015%, with the balance being Fe and impurities is used as a first material; When three-dimensional additive manufacturing is performed by arc welding using a stainless steel wire melting material made of the first material, the time from stacking any layer of the additive manufacturing layer to stacking the layer above it (hereinafter referred to as the "inter-layer interval") is 60 seconds or less, and after arc welding, the material is cooled to 700 to 300 ° C. at an average cooling rate of 1 ° C. / s or more, Then, a welding material made of a second material having a different chemical composition from the first material is used to perform three-dimensional additive manufacturing adjacent to the already-formed additive manufacturing layer of the first material by arc welding at a head speed of 5 mm / s to 100 mm / s, and cooling of the area is started within 100 seconds after welding, and after the start of cooling, the area is cooled to 500°C or less at an average cooling rate of more than 20°C / s.

2. 2. The method for manufacturing an additively manufactured product according to claim 1, wherein, when forming an object made of the first material, and then performing three-dimensional additive manufacturing by arc welding using a welding material made of the second material at a head speed of 5 mm / s to 100 mm / s, the three-dimensional additive manufacturing is performed while tilting the layered structure by 20° or more from the horizontal or vertical direction while rotating so as to achieve a head speed of 5 mm / s to 100 mm / s, and when arc welding the second material, the layered structure is subjected to additive manufacturing while being intermittently cooled by immersing a part of the layered structure in cooling water in a water tank.

3. A martensitic stainless steel containing, by mass%, C: 0.10 to 0.35%, Si≦3.0%, Mn≦5.0%, S≦0.03%, P≦0.05%, Cr: 10 to 17.5%, N≦0.15%, O≦0.015%, with the balance being Fe and impurities is used as a first material; forming a shaped object using a second material having a component composition different from that of the first material; Thereafter, when three-dimensional additive manufacturing is performed by arc welding using a stainless steel wire melting material made of the first material so as to be adjacent to the object, the time from laminating any layer of the additive manufacturing layers to laminating the layer above it (hereinafter referred to as the "inter-lamination interval") is set to 60 seconds or less, and after arc welding, the temperature is cooled to 700 to 300°C at an average cooling rate of 1°C / s or more; A method for manufacturing an additive manufacturing product, characterized in that the hardness variation of the additive manufacturing layer made of the first material is ΔHv≦100.

4. 4. The method for manufacturing an additively manufactured product according to claim 3, wherein when forming the object using the second material, three-dimensional additive manufacturing is performed by arc welding using a welding material made of the second material.

5. 5. The method for producing an additive manufactured product according to any one of claims 1 to 4, characterized in that the first material 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 portion of the Fe.

6. 6. The method for manufacturing an additive manufactured product according to claim 1, wherein the second material is made of ferritic stainless steel or austenitic stainless steel.

7. A martensitic stainless steel containing, by mass%, C: 0.10 to 0.35%, Si≦3.0%, Mn≦5.0%, S≦0.03%, P≦0.05%, Cr: 10 to 17.5%, N≦0.15%, O≦0.015%, with the balance being Fe and impurities is used as a first material; an additive manufacturing layer including a plurality of layers made of the first material is formed, and a molded object made of a second material having a component composition different from that of the first material is formed adjacent to the additive manufacturing layer; The hardness of the additive manufacturing layer made of the first material from the surface layer to a depth of 3 mm is Hv≧400, the hardness variation ΔHv≦100, and the layer spacing of the additive manufacturing layer is 2.5 mm or less. An additive manufacturing product.

8. The additively manufactured product according to claim 7 , wherein the product made using the second material is made up of a plurality of additively manufactured layers.

9. 9. The additive manufactured product according to claim 7 or 8, characterized in that the first material 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 portion of the Fe.

10. The additively manufactured product according to any one of claims 7 to 9, wherein the second material is made of ferritic stainless steel or austenitic stainless steel.

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