Fe-based alloy powder for additive manufacturing with excellent resistance to cracking during manufacturing and high thermal conductivity, and additive manufacturing body using the same

Abstract

To provide a powder for additive manufacturing and an additive-manufactured object using it that exhibits high thermal conductivity and is resistant to cracking in both the manufactured object and the interface between the manufactured object and the substrate material, even in large-scale additive manufacturing.SOLUTION: A powder for additive manufacturing that satisfies the followings: in mass %, C: 0.11 - 0.29%, Si:≤0.9%, Mn:≤0.9%, P:≤0.024%, S:≤0.024%, Cr: 6.1 - 9.9%, Ni: 3.1 to 6.9%, remainder Fe and unavoidable impurities, and Formula A: [Ni] - 0.2[Cr]≥1.8, Formula B: [Ni] - 2.0[Cr]≤-8.0, Formula C: [Ni] + 0.6[Cr]≤11.0.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to shaped bodies and raw material powders that can be used to make various tools, including molds, using additive manufacturing (also known as 3D printers, three-dimensional modeling, additive manufacturing, etc.), and in particular to powders for additive manufacturing that exhibit high resistance to molding cracking, preventing cracking even in large shaped bodies, high thermal conductivity, and also have high mechanical properties.

[0002] Here, high resistance to cracking during molding refers to the fact that cracks are less likely to occur in the molded body itself (especially in areas where notches will form) or at the interface between the molded body and the molding base material due to thermal stresses associated with rapid melting and solidification during additive manufacturing. [Background technology]

[0003] Unlike conventional manufacturing methods, additive manufacturing is capable of manufacturing components with complex shapes and three-dimensional structures, and in recent years has seen remarkable technological development and an expansion of its range of applications. In this context, the technology is also being studied and applied to various tools, and in particular, practical application is progressing in die-casting molds that have complex three-dimensional cooling water pipes inside.

[0004] These tools are used to process a variety of parts, and their shapes and sizes vary depending on the processing method and part shape. Generally, additive manufacturing involves rapidly melting and solidifying raw material powder or wire by heating it for a short period of time with a narrowly focused heat source such as a laser or electron beam. Repeating this process builds up solidified layers, enabling the production of parts with complex three-dimensional shapes. During this process, only a portion of the part is heated, melted, and solidified, generating thermal stress due to localized solidification shrinkage and thermal expansion and contraction. If the material being molded or the base material is hard and brittle, it will not be able to withstand the thermal stress, resulting in cracks in the molded object itself or at the interface with the base material.

[0005] Such thermal stress becomes even greater when large objects are additively manufactured, resulting in increased likelihood of cracks during manufacturing. Generally, high-hardness alloys such as JIS standard SKD61 are used for tools, which make them prone to cracks during manufacturing. Therefore, the application of additive manufacturing to tools has traditionally been limited to small tools with relatively small thermal stresses.

[0006] In recent years, M S Using an alloy with a low point, S A method has been proposed to suppress cracking during manufacturing by preheating the material to near the melting point and maintaining the soft, ductile austenite phase rather than the hard, brittle martensite phase during manufacturing. S Lowering the score can be an indicator of improved molding crack resistance.

[0007] The surfaces of tools used in hot working, such as die-casting dies, rise in temperature when they come into contact with the high-temperature parts (workpieces) being processed, causing damage such as heat checking. Furthermore, areas that experience particularly rapid temperature increases can become seized. To avoid these problems, it is important to efficiently cool the die surface. By using alloys with high thermal conductivity as the die material, the cooling effect of water-cooled pipes installed inside the tool can be maximized, even to the die surface.

[0008] Furthermore, when machining parts using hot tools, the tools must cool down after machining one part before machining the next part. If the tools can be cooled efficiently (in a short time) to the specified temperature, the part machining cycle can be shortened, which has the advantage of increasing part production efficiency.

[0009] Patent Documents 1 and 2 are examples of additively manufactured bodies made from Fe-based alloys with high resistance to cracking during manufacturing and high thermal conductivity. The major difference between the main components of the inventions in Patent Documents 1 and 2 is the amount of Cr, with Patent Document 1 generally having a higher Cr content than Patent Document 2. Furthermore, both Conventional Examples 1 and 2 restrict the variable A (= 15C + Mn + 0.5Cr + Ni) to a certain range.

[0010] Patent Document 1 regulates the contents of various elements and sets the variable A at more than 10 and less than 20. As described above, Conventional Example 1 is in the high Cr range, and therefore the balance between Cr and Ni is on the low Ni side due to the control of variable A, and the properties in the opposite range of low Cr (12% or less) and high Ni (4% or more) have not been fully studied.

[0011] Patent Document 2 regulates the contents of various elements and sets the variable A at more than 11.5 and less than 20. As described above, Conventional Example 2 is in the low Cr range, and therefore the balance between Cr and Ni is on the high Ni side due to the control of variable A, and the properties in the opposite range of high Cr (6% or more) and low Ni (7% or less) have not been fully studied. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2023-71145 [Patent Document 2] Japanese Patent Publication No. 2023-71110 Summary of the Invention [Problem to be solved by the invention]

[0013] The problem that the present invention aims to solve is to provide a powder for additive manufacturing, which has high thermal conductivity and is less likely to cause cracks at the interface between the molded body and the additive base material, even in large-scale additive manufacturing, and an additive manufacturing body made using the powder. [Means for solving the problem]

[0014] The inventors conducted detailed studies focusing on the range of 6-12% Cr and 4-7% Ni, and surrounding areas. As a result, they discovered that a powder for additive manufacturing with excellent properties can be obtained by specifying the balance between Cr and Ni within the range surrounded by formulas A, B, and C near this range, and by specifying the components other than Cr and Ni within desired ranges.

[0015] That is, the first means for solving the problems of the present invention is: In mass%, C: 0.11 to 0.29%, Si: 0.9% or less, Mn: 0.9% or less, P: 0.024% or less, S: 0.024% or less, Cr: 6.1~9.9%, Ni: 3.1-6.9% The balance is Fe and unavoidable impurities, Formula A: [Ni]-0.2[Cr]≧1.8, Formula B: [Ni]-2.0 [Cr]≦-8.0, This powder for additive manufacturing satisfies the formula C: [Ni] + 0.6 [Cr] ≦ 11.0. However, the mass% values ​​of each component are substituted for [Ni] and [Cr] in the formula.

[0016] The second method is O: 0.10% or less, The powder for layered manufacturing according to the first aspect of the present invention has N of 0.15% or less.

[0017] The third method is In addition to the ingredients described in either the first or second means, As an optional additional component, one or more of Mo, W, V, Al, and Cu may be added. Mo+W / 2: 1.4% or less, V: 0.7% or less, Al: 0.045% or less, Cu: contained in the range of 4.5% or less, The balance is Fe and unavoidable impurities, Formula A: [Ni]-0.2[Cr]≧1.8, Formula B: [Ni]-2.0 [Cr]≦-8.0, This powder for additive manufacturing satisfies the formula C: [Ni] + 0.6 [Cr] ≦ 11.0. However, the mass percentage values ​​of each component are substituted for [Mo], [W], [Ni], and [Cr] in the formula.

[0018] The fourth aspect of the present invention is a shaped body produced by layered manufacturing using the powder according to any one of the first to third aspects. [Effects of the Invention]

[0019] It is possible to provide a powder for additive manufacturing and an additive manufacturing object using the same that is less likely to crack at the interface between the molded object and the additive base material, even in large-scale additive manufacturing, and has high thermal conductivity. DETAILED DESCRIPTION OF THE INVENTION

[0020] Before describing the embodiments of the present invention, the reasons for defining each component of the present invention will be explained. Note that % in the components refers to % by mass. In addition, the reasons for defining Formula A, Formula B, and Formula C will be explained.

[0021] C: 0.11 to 0.29% C is an essential element for obtaining high quench-and-temper hardness by dissolving in the martensite phase, which is the matrix, and precipitating fine carbides. However, if the C content is less than 0.11%, high quench-and-temper hardness cannot be obtained. C content is preferably 0.12% or more, more preferably 0.13% or more. On the other hand, if the C content exceeds 0.29%, the as-formed hardness becomes excessively high, deteriorating the forming crack resistance. C content is preferably 0.24% or less, more preferably 0.19% or less.

[0022] Si: 0.9% or less (optional component) Since Si has the effect of improving the flowability of the molten alloy, adding it appropriately can reduce the likelihood of nozzle clogging during powder production by atomization. When Si is added, it is preferable to add 0.1% or more. On the other hand, adding more than 0.9% Si reduces thermal conductivity. The Si content is preferably 0.7% or less, more preferably 0.4% or less.

[0023] Mn: 0.9% or less (optional component) Mn has the effect of improving the flowability of molten alloy, so adding it appropriately can make nozzle clogging less likely during powder production by atomization. When Mn is added, it is preferably added in an amount of 0.1% or more. On the other hand, adding more than 0.9% of Mn reduces thermal conductivity. The Mn content is preferably 0.4% or less, more preferably 0.3% or less.

[0024] P:0.024% or less P is a typical impurity, but adding trace amounts has the effect of improving the flow of molten alloy, so adding an appropriate amount can make nozzle clogging less likely during powder production by atomization. The P content is preferably 0.001% or more. On the other hand, if the P content exceeds 0.024%, solidification cracking is more likely to occur during additive manufacturing. The P content is preferably 0.014% or less, more preferably 0.004% or less. The same effect can be achieved whether P is contained as an impurity or intentionally added.

[0025] S: 0.024% or less S is a typical impurity, but adding a small amount has the effect of improving the flowability of the molten alloy, so adding an appropriate amount can make nozzle clogging less likely during powder production by atomization. The S content is preferably 0.001% or more. On the other hand, if the S content exceeds 0.024%, solidification cracking is more likely to occur during additive manufacturing. The S content is preferably 0.014% or less, more preferably 0.004% or less. The same effect can be obtained whether S is included as an impurity or intentionally added.

[0026] Cr: 6.1 to 9.9% Cr has the effect of improving hardenability and corrosion resistance, and also has the effect of improving M S It is an important essential element in the present invention because it has the effect of reducing the number of defects. Furthermore, tool steels are often used while being cooled with industrial water or the like, and therefore corrosion resistance is also required to prevent rusting, so the addition of Cr is also essential in this respect. However, if the Cr content is less than 6.1%, the low M S The point cannot be obtained. Cr is preferably 7.1% or more, more preferably 8.1% or more. On the other hand, if Cr exceeds 9.9%, the thermal conductivity will be significantly reduced. Therefore, Cr is preferably 9.4% or less, more preferably 9.3% or less.

[0027] Ni: 3.1 to 6.9% Ni has the effect of improving hardenability and corrosion resistance, as well as M S Ni is an important essential component in the present invention because it has the effect of reducing the number of defects. Furthermore, tool steels are often used while being cooled with industrial water or the like, and therefore, corrosion resistance to prevent rusting is also required, so the addition of Ni is also essential in this respect. However, if Ni is less than 3.1%, the low M S The Ni content is preferably 3.5% or more, more preferably 3.7% or more. On the other hand, if the Ni content exceeds 6.9%, the thermal conductivity will decrease significantly. Therefore, the Ni content is preferably 5.4% or less, more preferably 4.9% or less.

[0028] O: preferably 0.100% or less O is an impurity that inevitably gets mixed in during powder production, mainly by gas atomization. If the O content exceeds 0.100%, gas is generated during additive manufacturing, leaving pores inside the molded object. Therefore, the O content is preferably 0.050% or less, and more preferably 0.030% or less. However, it is difficult to keep the O content in powder below 0.003%, so it is acceptable for O to be unavoidably contained.

[0029] N: preferably 0.150% or less N is an impurity that inevitably gets mixed in during powder production, mainly by gas atomization. If it exceeds 0.150%, gas is generated during additive manufacturing, leaving pores inside the molded object. Therefore, the N content is preferably 0.120% or less, and more preferably 0.090% or less. However, it is difficult to keep the N content in powder below 0.003%, so it is acceptable for N to be unavoidably contained.

[0030] Next, we will explain the reason why Mo, W, V, Al, and Cu are optional additional components. When adding these components, one or more of them can be added optionally.

[0031] Mo+W / 2: 1.4% or less Mo and W are components that promote secondary hardening during tempering and increase quench-temper hardness, and can be added as needed. When Mo and W are added, the total amount of Mo+W / 2 is preferably 0.1% or more. On the other hand, if the total amount of Mo+W / 2 exceeds 1.4%, the thermal conductivity decreases. From this perspective, when Mo and W are added, the preferred amount is a total amount of Mo+W / 2 of 0.2% or less.

[0032] V: 0.7% or less V is a component that promotes secondary hardening during tempering and increases quench-temper hardness, and can be added as needed, but excessive addition reduces thermal conductivity. V content is preferably 0.2% or less, and more preferably no addition.

[0033] Al: 0.045% or less Al is a component that forms nitrides and suppresses grain coarsening during quenching, and can be added as needed. The Al content is preferably 0.001% or more, more preferably 0.002% or more. However, if 0.045% or more of Al is added, excessive Al nitrides are formed, reducing toughness. It also reduces thermal conductivity. The Al content is preferably 0.025% or less, more preferably 0.009% or less. Note that Al is not only added intentionally, but can also be mixed in from refractories used in the melting process for gas atomization. In either case, the effect of containing Al is similar.

[0034] Cu:4.5% or less Cu has a relatively low thermal conductivity. S It is a component that can lower the M S Cu may be added as needed to lower the temperature. It may also be added from the viewpoint of improving corrosion resistance. Cu is preferably 0.1% or more, more preferably 0.2% or more. On the other hand, excessive addition of Cu reduces thermal conductivity. Therefore, Cu is preferably 2.9% or less, more preferably 0.4% or less.

[0035] Formula A: [Ni]-0.2[Cr]≧1.8, Formula B: [Ni]-2.0 [Cr]≦-8.0, Formula C: [Ni] + 0.6 [Cr] ≦ 11.0 In the formula, the mass % values ​​of the components are substituted for [Ni] and [Cr]. The reasons for specifying the values ​​of these formulas A, B, and C will be explained in turn. By satisfying the values ​​of these formulas A, B, and C, it is possible to identify the balanced region of Cr and Ni surrounded by formulas A, B, and C, and it becomes possible to selectively capture the powder. Furthermore, the amounts of Cr and Ni added are greater than those of other elements, and they have a greater impact on these formulas.

[0036] Formula A: 1.8 or more Formula A([Ni]-0.2[Cr]) is M due to the balance of Cr and Ni. S Cr is a carbide-forming element, and Ni is a non-carbide-forming element. The balance between these elements affects the carbide formation behavior, including secondary hardening, and the resulting martensite phase composition of the matrix, which in turn affects hardness as well as M. S It also affects the temperature and thermal conductivity. If the value of [Ni]-0.2[Cr] in formula A is less than 1.8, the amount of Cr relative to Ni is excessively high, and a large amount of Cr carbide is formed, resulting in a deficiency of C in the matrix, resulting in M. S The score will be higher. Here, C is M SThe value of formula A is preferably 1.9 or more, more preferably 2.0 or more.

[0037] Formula B: -8.0 or less Formula B([Ni]-2.0[Cr]) is an important parameter for controlling high thermal conductivity by the balance of Cr and Ni. Cr is a carbide-forming component, while Ni is a non-carbide-forming component. The balance of these two components affects the carbide formation behavior, including secondary hardening, and the resulting composition of the martensite phase in the matrix, resulting in hardness as well as M. S It also affects the temperature and thermal conductivity. If the value of [Ni]-2.0[Cr] in formula B exceeds -8.0, the amount of Cr relative to Ni is too low, the amount of Cr carbide formed is too small, and the amount of C in the matrix becomes excessive, resulting in low thermal conductivity. Here, C is a component that reduces thermal conductivity. The value of formula B is preferably -9.0 or less, more preferably -11.0 or less.

[0038] Formula C: 11.0 or less Formula C ([Ni] + 0.6[Cr]) is an important parameter for controlling the quenching and tempering hardness by the balance between Cr and Ni. If the amounts of both Cr and Ni added are excessively high, austenite becomes overly stabilized, and this soft austenite tends to remain without sufficient decomposition, resulting in insufficient hardness. If the value of [Ni] + 0.6[Cr] in formula C exceeds 11.0, the retained austenite becomes stable and insufficient hardness cannot be obtained. The value of formula C is preferably 10.5 or less, more preferably 10.0 or less.

[0039] Specific embodiments of the present invention will be described below using examples and comparative examples of the present invention shown in Table 1. It should be noted that these examples are merely examples of embodiments of the present invention, and the scope of the claims is not limited to these examples alone.

[0040] [Production of raw powder] Powders with the components listed in Examples 1 to 24 in Table 1 and Comparative Examples 1 to 16 in Table 2 were obtained by gas atomization. First, the raw materials placed in an alumina crucible were melted by high-frequency heating in a vacuum and argon atmosphere. Next, the molten alloy was poured from a 5 mm diameter nozzle at the bottom of the crucible and immediately sprayed with high-pressure argon gas. This spraying breaks the molten alloy into fine droplets, which cool and solidify as they fall through the tower of the atomization device, becoming alloy powder. This alloy powder was shaken through a sieve with a mesh opening of 63 μm, and the powder that fell through the sieve was used as the raw material powder for the subsequent additive manufacturing process.

[0041] [Additive Manufacturing] The additive manufacturing was performed using a laser-heated powder bed type device (product name: EOS-M290) with the preheating temperature set to 180°C under the standard manufacturing conditions (MS1 conditions) for maraging steel set on the device. The base plate used for the manufacturing was annealed S45C, and a 20mm x 20mm x 20mm block was manufactured on top of this.

[0042] [evaluation] The molded blocks were cut using a wire cutter and used for evaluation. The hardness was measured using a Rockwell hardness tester. The thermal conductivity was measured by the laser flash method (test piece size: diameter 5 mm × thickness 1 mm). M S The thermal expansion characteristics were measured using a Formaster tester with a test piece of 3 mm diameter x 10 mm length. S The maximum heating temperature was 1050°C. The results are shown in Tables 1 and 2.

[0043] Hardness, M S In terms of the evaluation of hardness and thermal conductivity, those with a hardness of 45 to 55HRC, an Ms point of 230°C or less, and a thermal conductivity of 18.0W / m·K or more were judged to be good.

[0044] In some examples, the blocks cut by wire cutting were tempered at the following temperatures: 525°C for example 3, 600°C for example 9, 575°C for example 14, and 625°C for example 22. The tempering was performed by holding the blocks at these tempering temperatures for one hour, followed by air cooling, and this procedure was repeated twice.

[0045] [Table 1]

[0046] [Table 2]

[0047] All test pieces additively manufactured using the powders of Examples 1 to 24 satisfied the components and values ​​of formulas A, B, and C defined by the present invention. These manufactured test pieces had hardnesses of 45.6 to 54.5 HRC, which was the hardness required for machine tools and parts such as molds, but was not too hard and did not cause cracking during manufacturing. Appropriate quenched and tempered hardness was also obtained. Furthermore, in the examples, the Ms point was kept low at 132 to 222°C, making it easier to suppress cracking during manufacturing. Furthermore, in the examples, the thermal conductivity was 18.1 W / m·k or higher, demonstrating good thermal conductivity.

[0048] In Comparative Example 1, the amount of C was too small, and hardness was not obtained. In Comparative Example 2, the value of formula B is on the high side, and the amount of Cr relative to Ni is low, so the amount of Cr carbide produced is excessively small and C in the matrix is ​​excessive, resulting in low and inferior thermal conductivity. In Comparative Example 3, the value of formula A is out of range, and M S The points are too high, resulting in poor resistance to cracking during molding. In Comparative Example 4, the value of formula C is not obtained, and the hardness is not obtained. In addition, the thermal conductivity is low and poor. In Comparative Example 5, the value of formula A is out of range, and M S The points are too high, resulting in poor resistance to cracking during molding. In Comparative Example 6, the value of formula C is out of range, and the hardness is not obtained. In addition, the thermal conductivity is low and poor. In Comparative Example 7, the value of formula B is on the high side, and the thermal conductivity is low and inferior. In Comparative Example 8, the value of formula A is out of range, and M S The points are too high, resulting in poor resistance to cracking during molding. In Comparative Example 9, the value of formula C was out of range, and the hardness was not obtained. In addition, the thermal conductivity was low and poor. In Comparative Example 10, the value of formula A is out of range, and M S The points are too high, resulting in poor resistance to cracking during molding. In Comparative Example 11, the value of formula C was out of range, and the hardness was not obtained. In addition, the thermal conductivity was low and poor. Comparative Example 12 contained too much C, which resulted in an excessively high hardness in the as-formed state, and therefore had poor resistance to cracking during forming. Comparative Example 13 had an insufficient amount of Cr, and M S The score is not lower. Comparative Example 14 contains an excessive amount of Cr, and has a low thermal conductivity. In Comparative Example 15, the amount of Ni was too small, and the value of formula A was not obtained. S The points are too high, resulting in poor resistance to cracking during molding. In Comparative Example 16, the value of formula C is not obtained, and the hardness is not obtained. In addition, the thermal conductivity is low and poor. [Industrial Applicability]

[0049] The powder for additive manufacturing of the present invention is M S Since the spot temperature is suppressed and the molding is less likely to crack, it is suitable for additive manufacturing.The additive manufactured body has excellent thermal conductivity and sufficient hardness, making it suitable for mold applications and can be suitably used for industrial machinery applications such as hot work tool parts.

Claims

1. In mass%, C: 0.11-0.29%, Si: 0.9% or less, Mn: 0.9% or less, P: 0.024% or less, S: 0.024% or less, Cr: 6.1-9.9%, Ni: 3.1 to 6.9%, The balance consists of Fe and unavoidable impurities, Formula A: [Ni]-0.2[Cr]≧1.8, Formula B: [Ni]-2.0[Cr]≦-8.0, Powder for additive manufacturing that satisfies formula C: [Ni] + 0.6 [Cr] ≦ 11.

0. In the formula, the mass % values ​​of each component are substituted for [Ni] and [Cr].

2. O: 0.10% or less, The powder for additive manufacturing according to claim 1, wherein N is 0.15% or less.

3. In addition to the components according to claim 1 or 2, As an optional additional component, one or more of Mo, W, V, Al, and Cu may be added. Mo+W / 2: 1.4% or less, V: 0.7% or less, Al: 0.045% or less, Cu: contained in a range of 4.5% or less, The balance consists of Fe and unavoidable impurities, Formula A: [Ni]-0.2[Cr]≧1.8, Formula B: [Ni]-2.0[Cr]≦-8.0, Powder for additive manufacturing that satisfies formula C: [Ni] + 0.6 [Cr] ≦ 11.

0. In the formula, the mass % values ​​of each component are substituted for [Mo], [W], [Ni], and [Cr].

4. In mass %, C: 0.11-0.29%, Si: 0.9% or less, Mn: 0.9% or less, P: 0.024% or less, S: 0.024% or less, Cr: 6.1-9.9%, Ni: 3.1 to 6.9%, The balance consists of Fe and unavoidable impurities, Formula A: [Ni]-0.2[Cr]≧1.8, Formula B: [Ni]-2.0[Cr]≦-8.0, An additive manufacturing object formed from a powder for additive manufacturing that satisfies formula C: [Ni] + 0.6 [Cr] ≦ 11.

0. In the formula, the mass % values ​​of each component are substituted for [Ni] and [Cr].

5. In mass %, C: 0.11-0.29%, Si: 0.9% or less, Mn: 0.9% or less, P: 0.024% or less, S: 0.024% or less, Cr: 6.1-9.9%, Ni: 3.1 to 6.9%, As an optional additional component, one or more of Mo, W, V, Al, and Cu may be added. Mo+W / 2: 1.4% or less, V: 0.7% or less, Al: 0.045% or less, Cu: contained in a range of 4.5% or less, The balance consists of Fe and unavoidable impurities, Formula A: [Ni]-0.2[Cr]≧1.8, Formula B: [Ni]-2.0[Cr]≦-8.0, An additive manufacturing object formed from a powder for additive manufacturing that satisfies formula C: [Ni] + 0.6 [Cr] ≦ 11.

0. In the formula, the mass % values ​​of each component are substituted for [Ni] and [Cr].

Images