JP2021116441A - Alloy member and method for producing the same - Google Patents

Abstract

To provide an alloy member whose thermal coefficient of expansion changes continuously or stepwise, and a method for producing the same.SOLUTION: An alloy member consists of an Fe-Ni-based alloy, at least a part of which continuously or stepwise changes in Ni content such that the thermal coefficient of expansion continuously or stepwise changes in an arbitrary range of 0-13 ppm/°C.SELECTED DRAWING: Figure 2

Description

The present invention relates to an alloy member having a distribution of coefficient of thermal expansion and a method for producing the same.

When a temperature difference occurs in the member, thermal stress is generated (according to the physical property value, size / shape, temperature distribution, etc. of the member), which causes deformation of the member. Of the deformations, elastic deformation causes accuracy error, especially in equipment that requires high accuracy, and high accuracy cannot be maintained. Further, in a device such as a combustion engine that causes a large temperature difference, plastic deformation may occur and the member may be destroyed. Therefore, there is a demand for a technique for alleviating or preventing deformation and fracture due to thermal stress, and functionally graded materials are available as a technique capable of dealing with this. A functionally graded material is one in which the composition and function change (tilt) continuously or stepwise within one material. Therefore, by using a functionally graded material in which the coefficient of thermal expansion in the member is continuously or stepwise changed, deformation and fracture due to thermal stress can be alleviated or prevented.

Centrifugal casting, powder metallurgy, composite plating, thermal spraying, directed energy deposition, and the like have been proposed as methods for producing functionally graded materials (Non-Patent Documents 1 to 4 and Patent Documents 1 to 2).

Of these, Non-Patent Document 3 describes that an aluminum-aluminum nitride (Al-AlN) composite ingot is melted at 1000 ° C. under ultravacuum and centrifugal force is applied by high-speed rotation to form a functionally graded structure at 250 ° C. It is described that an Al-AlN functionally graded material is produced by a centrifugal casting method for solidification.

Further, Non-Patent Document 4 describes that a functionally graded material is produced by using Directed Energy Deposition (DED), which is a three-dimensional laminated molding technique for metal-based materials. DED is a molding technology in which powder is supplied from an injection nozzle and at the same time heat is applied by a heat source such as a laser to melt and bond the powder. It is described that functionally graded materials can be produced by modeling while changing the mixing ratio of the powders because a plurality of types of powders can be mixed in the process. Further, in DED, the material needs to be supplied only to the necessary part, and the laminating thickness is larger than that of the PBF (Power Bed Fusion (powder bed melting bond)) laminating molding, so that the molding speed is high. , It is described that it is suitable for molding large members.

JP-A-2010-006054 Japanese Unexamined Patent Publication No. 01-312015

Development Trends of Functionally Graded Materials (Journal of Precision Engineering, Vol.83, No.5, 2017, P391) Illustrated Basics and Applications of Functionally Graded Materials (Corona Publishing Co., Ltd., Table of Contents Chapter 2) https://www.coronasha.co.jp/np/isbn/9784339046298/ Functionally graded material made of aluminum and aluminum nitride produced by centrifugal casting technology with high heat dissipation https://corec.meisei-u.ac.jp/archives/1028 Basics of 3D Laminated Modeling Technology for Metallic Materials (Materia, Vol. 56, No. 12 (2017))

However, the centrifugal casting method utilizes the difference in the specific densities of the materials, and can be applied only to the combination in which the difference in the specific densities between the constituent materials is large. The powder metallurgy method is a method of laminating by changing the compounding ratio of the constituent materials step by step, and in addition to the limitation of the continuity of the component composition, HIP treatment is required after sintering to make a high-density member, which makes manufacturing. It gets complicated. In the thermal spraying method, it is possible to continuously change the content of the constituent materials for laminating, but there is a problem that there is a large amount of porosity in the members. In the composite plating method, the content of constituent elements can be controlled by continuously changing the current density, but there are problems that the range of the component composition ratio that can be changed is narrow and the film formation rate is very slow. Further, all of these techniques have a problem that there are large restrictions on the size and shape of the member that can be manufactured.

On the other hand, in the DED method laminated modeling, as disclosed in Non-Patent Document 4, since a plurality of types of powder can be mixed in the powder transport process, the content rate of the constituent materials can be continuously changed. , There are few restrictions on the size and shape of the members that can be manufactured.

However, Non-Patent Document 4 does not describe any member whose thermal expansion coefficient is continuously or stepwise changed.

An object of the present invention is to provide an alloy member whose coefficient of thermal expansion changes continuously or stepwise and a method for producing the same.

The present inventors use a laminated molding machine using a laser beam, an electron beam, or plasma to produce Ni powder and Fe powder in an arbitrary ratio within a certain range (Fe: 0 to 65%, Ni: 35 to 100%). An arbitrary shape and any size Fe—Ni-based alloy member in which the coefficient of thermal expansion is continuously or stepwise changed in an arbitrary range between 0 and 13 ppm / ° C. We have found that it can be obtained and have completed the present invention.

That is, the present invention provides the following (1) to (8).

(1) It is composed of an Fe—Ni alloy, and at least a part of it has a continuous or stepwise Ni content such that the coefficient of thermal expansion changes continuously or stepwise in an arbitrary range between 0 and 13 ppm / ° C. An alloy member characterized by being gradually changed.

(2) The Ni content of the alloy member is continuously or stepwise changed so that the coefficient of thermal expansion at one end is the lowest and the coefficient of thermal expansion at the other end is the highest. The alloy member according to (1) above.

(3) The alloy member is characterized in that the Ni content is continuously or stepwise changed so that the coefficient of thermal expansion at both ends is the lowest and the coefficient of thermal expansion at the center is the highest. The alloy member according to (1) above.

(4) The alloy member is characterized in that the Ni content is continuously or stepwise changed so that the coefficient of thermal expansion at both ends is the highest and the coefficient of thermal expansion at the center is the lowest. The alloy member according to (1) above.

(5) In the alloy member, Ni is continuously or stepwise changed in the range of 35% or more in mass%, C: 0.03% or less, Si: 0.2% or less, Mn: 0.3. The alloy member according to any one of (1) to (4) above, which contains% or less, P: 0.02% or less, S: 0.01% or less, and the balance is composed of Fe and unavoidable impurities. ..

(6) The portion of the alloy member having the lowest coefficient of thermal expansion is in the range of Ni: 35.0 to 36.5%, and the portion of the alloy member having the highest coefficient of thermal expansion is Ni: 98.5 to. The alloy member according to (5) above, which is in the range of 100%.

(7) The alloy member according to any one of (1) to (6) above, which has a solidified structure having a dendrite secondary arm spacing of 30 μm or less.

(8) While supplying the alloy powder constituting any of the alloy members (1) to (7) above, the alloy powder is melted by a laser beam, an electron beam, or plasma to form a laminate, and the above (1) A method for manufacturing an alloy member for manufacturing any of the alloy members according to (7).

According to the present invention, there is provided an alloy member having a coefficient of thermal expansion that changes continuously or stepwise, and a method for producing the same.

It is a figure which shows the relationship between the Ni amount of Fe—Ni alloy produced by a normal casting process, and the coefficient of thermal expansion. It is a figure which shows the relationship between the Ni amount and the coefficient of thermal expansion of the Fe—Ni alloy manufactured by the laminated molding in comparison with the relationship between the Ni amount and the coefficient of thermal expansion of the Fe—Ni alloy manufactured by a normal casting process. It is a figure which shows the schematic structure of the laminated modeling apparatus used in an Example. It is a figure which shows the Ni concentration distribution of the sample (modeled object) produced in 1st Example. It is a figure which shows typically the Ni concentration structure set in 2nd Example.

Hereinafter, embodiments of the present invention will be described in detail.
In the following description, unless otherwise specified, the% representation of the components is mass%, and the coefficient of thermal expansion is the average coefficient of thermal expansion of 10 to 40 ° C.

FIG. 1 is a diagram showing the relationship between the Ni content and the coefficient of thermal expansion of an Fe—Ni alloy produced by a normal melting / casting process. As shown in this figure, when Fe is alloyed with Ni, the coefficient of thermal expansion decreases according to the amount of Fe added, continuously from 13 ppm / ° C in pure Ni to 1.2 ppm / ° C in 35.5% Ni. You can see that it changes. And it shows the lowest coefficient of thermal expansion at 35.5% Ni.

Therefore, by using a Fe—Ni alloy as the alloy member and changing the Ni content continuously or stepwise, the coefficient of thermal expansion can be changed continuously or stepwise. However, the Fe-Ni alloy produced by a normal melting / casting process has a limit of 1.2 ppm / ° C., and zero expansion cannot be realized.

On the other hand, for alloys in the above composition range, the coefficient of thermal expansion can be reduced by increasing the cooling rate during solidification to make the structure finer, and the alloy has a thermal expansion in the Fe-35% Ni composition, which is the minimum coefficient of thermal expansion. It has been found that the coefficient of expansion can be made substantially zero. It is considered that the main reason is that the microsegregation of Ni is reduced by the miniaturization of the structure. Such a large cooling rate can be realized by a laminated molding technique as described later. FIG. 2 is a diagram showing the relationship between the Ni amount of the Fe-Ni alloy manufactured by laminated molding and the coefficient of thermal expansion in comparison with the relationship between the amount of Ni of the Fe-Ni alloy manufactured by a normal casting process and the coefficient of thermal expansion. be. As shown in this figure, the coefficient of thermal expansion of the Fe-Ni alloy produced by laminated molding is smaller overall than the coefficient of thermal expansion of the Fe-Ni alloy produced by the normal casting process, and the minimum heat. It can be seen that in the Fe-35.5% Ni composition, which is the coefficient of expansion, 1.2 ppm / ° C. is substantially reduced to zero.

Therefore, by increasing the cooling rate during solidification, it is composed of Fe—Ni alloy, and at least a part of it changes continuously or stepwise in any range of thermal expansion coefficient between 0 and 13 ppm / ° C. As such, it is possible to realize an alloy member in which the Ni content is continuously or stepwise changed. When the coefficient of thermal expansion and the Ni content change stepwise, it is sufficient that there are two or more portions having different coefficients of thermal expansion.

At this time, it is preferable that the dendrite secondary arm spacing (DAS) of the alloy is 30 μm or less. By forming such a fine structure, martensite is not generated at the liquid helium temperature (-269 ° C.) in the Fe-35% Ni composition in which the amount of Ni is minimized and the stability of the austenite phase is lowered. be able to. Further, in order to obtain such a fine structure, it is preferable that the cooling rate at the time of solidification is 5000 ° C./sec or more.

For such an alloy member, the Ni content is continuously or stepwise changed so that the coefficient of thermal expansion at one end is the lowest and the coefficient of thermal expansion at the other end is the highest. Can be. Further, the Ni content is continuously or stepwise changed so that the coefficient of thermal expansion at both ends is the lowest and the coefficient of thermal expansion at the center is the highest, or the coefficient of thermal expansion at both ends is the highest. It is also possible that the Ni content is continuously or stepwise changed so as to be high and have the lowest coefficient of thermal expansion in the central part.

As the Fe-Ni alloy constituting the alloy member, in mass%, Ni changes continuously or stepwise in the range of 35% or more, C: 0.03% or less, Si: 0.2% or less, Mn: 0.3% or less, P: 0.02% or less, S: 0.01% or less, and the balance is composed of Fe and unavoidable impurities.

C: 0.03% or less, Si: 0.2% or less, Mn: 0.3% or less, P: 0.02% or less, S: 0.01% or less is the Fe-35% Ni composition. This is because it is necessary to limit the content of these elements in order to make the coefficient of thermal expansion substantially zero. Examples of unavoidable impurities include Cr and Mo, and the total amount thereof is preferably 0.2% or less.

In order to change the Ni content continuously or stepwise, the functionally graded material as described above is considered to be effective. Among the methods for producing the functionally graded material described above, the centrifugal casting method and the powder metallurgy method are used. In the composite plating method and the thermal spraying method, there are many restrictions on the size and shape of the members that can be manufactured.

On the other hand, using the DED method laminated molding technique described in Non-Patent Document 4, the alloy powder is melted by a laser beam, an electron beam, or plasma while supplying an alloy powder in which Fe and Ni are mixed in a predetermined ratio. By laminating the molding, it is possible to set the desired value of the coefficient of thermal expansion at an arbitrary position of the member. In addition, such a laminated molding technique makes it possible to manufacture a member having a size and shape that could not be manufactured by the conventional technique.

Further, in this laminated molding technique, the cooling rate at the time of solidification can be made extremely high as 5000 ° C./sec or more by using a laser beam, an electron beam or plasma as a heat source and appropriately selecting the parameters thereof. Therefore, the structure can be miniaturized and the coefficient of thermal expansion can be reduced, and the coefficient of thermal expansion can be made substantially zero in the Fe-35.5% Ni composition which is the minimum coefficient of thermal expansion.

As a result, the alloy member in which the ratio of Fe and Ni (Ni content) changes continuously or stepwise so that the coefficient of thermal expansion changes continuously or stepwise in an arbitrary range between 0 and 13 ppm / ° C. Can be manufactured.

Such laminated molding includes a stage, a powder supply mechanism that supplies alloy powder to the stage, an irradiation source that irradiates a laser beam, an electron beam, or plasma to a portion that supplies alloy powder, and a powder supply mechanism and an irradiation source. It can be carried out by a laminated molding apparatus having a scanning mechanism.

The portion of the alloy member having the lowest coefficient of thermal expansion is in the range of Ni: 35.0 to 36.5%, and the portion of the alloy member having the highest coefficient of thermal expansion is in the range of Ni: 98.5 to 100%. Is preferable. Thereby, the coefficient of thermal expansion of the alloy member can be changed between 0 and 13 ppm / ° C.

While supplying an alloy powder in which Fe and Ni are mixed in a predetermined ratio, the alloy powder is melted by a laser beam, an electron beam, or plasma to form a laminated structure, and one end is Ni: 35 having the lowest coefficient of thermal expansion. By setting the range from .0 to 36.5% and the other end in the range of Ni: 98.5 to 100%, which has the highest coefficient of thermal expansion, the coefficient of thermal expansion is extremely wide, 0 to 13 ppm / ° C. Functionally graded materials in the range of coefficient of thermal expansion can be realized.

Hereinafter, examples of the present invention will be described.
[First Example]
In the first embodiment, on a SS400 substrate having a thickness of 30 mm × 50 mm and a thickness of 20 mm, a layer thickness of 0.5 mm, a bead width of 2 mm, and a meat are formed by a DED type laminated molding apparatus having a laser output of 1 kW shown in FIG. A sample (modeled object) having a thickness of 10 mm × 30 mm and a thickness of 5 mm was formed using gas atomized Ni powder and Fe powder having a particle size of 45 to 90 μm at a filling speed of 10 cm ^{3 / h.} In FIG. 3, 1 is a powder supply device, 2 is a torch, 3 is a power supply, 4 is a cooling water device, 5 is a control device, 10 is a substrate, and 11 is a sample (modeled object). The powder supply device 1 has an Fe powder storage container 21 and a Ni powder storage container 22, and the powder supply is 2.5 g / min. The control device 5 was set so that the composition on the start side was 100% Ni and the composition on the end side was 28% -Fe 72% at the supply rate of. After separating the sample (modeled object) from the substrate by wire cutting, quantitative analysis of Ni was performed using EPMA at a pitch of 2 mm (partly 1 mm pitch) from the molding start surface. As shown in FIG. 4 and Table 1, it was confirmed that a single member having a Ni content changing almost continuously was obtained.

[Second Example]
In the second embodiment, on a SS400 substrate having a thickness of 30 mm × 170 mm and a thickness of 20 mm, a DED-type laminated molding apparatus having a laser output of 1 kW shown in FIG. A sample (modeled object) of 10 mm × 145 mm and a thickness of 10 mm was formed using gas atomized Ni powder and Fe powder having a particle size of 45 to 90 μm at a filling speed of 10 cm ^{3 / h.} The powder supply was 2.5 g / min. The control device 5 was set so that the composition on the start side was 100% Ni and the composition on the end side was Ni 30% -Fe 70% at the supply rate of. As shown in FIG. 5, the Ni concentration structure of the sample is such that a region having a length of 20 mm is a constant Ni concentration region, and the Ni concentration is gradually increased to 100% and 80% through an adjacent intermediate layer having a length of 5 mm. , 60%, 40%, 35.5%, and 30%. After separating the modeled object from the substrate by wire cutting, a thermal expansion measurement test piece of φ6 mm × 12 mm is processed from the center of each constant Ni concentration part, and averaged between 10 and 40 ° C. using a laser interference type thermal expansion meter. The coefficient of thermal expansion was investigated. After measuring the coefficient of thermal expansion, quantitative analysis of Ni was performed using EPMA. After Ni analysis, the structure and DAS of the sample were measured, and then the sample was immersed in liquid He and the presence or absence of structure change was observed. As shown in Table 2, it was confirmed that the Ni analysis value was almost the set concentration. The coefficient of thermal expansion is 13.01 ppm / ° C for the 100% Ni part and 0.02 ppm / ° C for the 35.5% Ni part. The coefficient of thermal expansion changes stepwise according to the Ni concentration, and the minimum Ni concentration is 35. It was confirmed that there was substantially zero expansion in the 5.5% Ni part. It was also confirmed that the structure did not change even when immersed in the liquid He temperature. The DAS before immersion in the liquid He was 24 μm.

1 Powder supply device 2 Torch 3 Power supply 4 Cooling water device 5 Control device 10 Substrate 11 Sample (modeled object)

Claims (8)

Consisting of Fe—Ni based alloys, the Ni content is continuous or gradual, at least in part, so that the coefficient of thermal expansion changes continuously or gradually in any range between 0 and 13 ppm / ° C. An alloy member characterized by being changing. The alloy member is characterized in that the Ni content is continuously or stepwise changed so that the coefficient of thermal expansion at one end is the lowest and the coefficient of thermal expansion at the other end is the highest. The alloy member according to claim 1. The alloy member is characterized in that the Ni content is continuously or stepwise changed so that the coefficient of thermal expansion at both ends is the lowest and the coefficient of thermal expansion at the center is the highest. The alloy member described in. The alloy member is characterized in that the Ni content is continuously or stepwise changed so that the coefficient of thermal expansion at both ends is the highest and the coefficient of thermal expansion at the center is the lowest. The alloy member described in. The alloy member changes continuously or stepwise in the range of Ni: 35% or more in mass%, C: 0.03% or less, Si: 0.2% or less, Mn: 0.3% or less, The alloy member according to any one of claims 1 to 4, wherein P: 0.02% or less, S: 0.01% or less, and the balance is composed of Fe and unavoidable impurities. The portion of the alloy member having the lowest coefficient of thermal expansion is in the range of Ni: 35.0 to 36.5%, and the portion of the alloy member having the highest coefficient of thermal expansion is Ni: 98.5 to 100%. The alloy member according to claim 5, wherein the alloy member is in a range. The alloy member according to any one of claims 1 to 6, wherein the dendrite has a solidified structure having a secondary arm spacing of 30 μm or less. While supplying the alloy powder constituting the alloy member according to any one of claims 1 to 7, the alloy powder is melted by a laser beam, an electron beam, or plasma to form a laminate, and the alloy powder is laminated. A method for manufacturing an alloy member, which comprises manufacturing the alloy member according to any one of 7.

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