JP2004115905A - Low thermal expansion alloy, and low thermal expansion alloy sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low thermal expansion alloy in which the consistency of the thermal expansion coefficient with that of a ceramics material, for example, can be optimized, to provide a low thermal expansion alloy sheet consisting of the low thermal expansion alloy, and to provide an alloy sheet for joining with a ceramics material obtained by using the low thermal expansion alloy sheet. <P>SOLUTION: The low thermal expansion alloy has a composition comprising, by mass, <0.06% C, ≥20% Ni, ≥27% Co, and 50 to 70% (Ni+Co), and comprising other element of ≤2.0% in total, and the balance Fe, and has an austenite single phase structure. In the alloy, the ratio between the average thermal expansion coefficient α<SB>1</SB>in the range from 30°C to the displacement point (T<SB>A</SB>) of the inclination of a thermal expansion curve and the average thermal expansion coefficient α<SB>2</SB>in the range from T<SB>A</SB>to 1,000°C, α<SB>2</SB>/α<SB>1</SB>is ≤2.1, and T<SB>A</SB>is 500 to 750°C. <P>COPYRIGHT: (C)2004,JPO

Description

【００２１】
上記のＮｏ．１〜７の合金を熱間鍛造後、熱間圧延を行なって厚さ１２ｍｍの板材とした。その得られた板材に８００℃×３０分で焼鈍を行ない、空冷した。この板材料より、長さ２０ｍｍの熱膨張測定試験片を採取し、昇温速度１０℃／分で、ＳｉＯ_２の標準試料との比較測定を行う示差膨張測定方式により、３０℃から１０００℃までの昇温過程における熱膨張曲線を作成した。
それぞれの合金から得られた熱膨張曲線を図１と図２に示した。図中に示した点線は、それぞれ熱膨張係数９．０×１０^−６／℃及び１３．０×１０^−６／℃の熱膨張曲線である。表２に、これらの熱膨張曲線より求めたＴ_Ａとα_２／α_１の値も記す。
また、熱膨張測定試験片を採取した同一の板材から、エックス線回折用試験片も採取し、オーステナイト相が体積分率で９９％以上を占める単相組織となっていることを確認した。
【００２２】
【表２】

【００２３】
図１及び２、表２の結果から、Ｎｏ．１においては、合金組成、（Ｎｉ＋Ｃｏ）量、Ｔ_Ａ、α_２／α_１とも本発明範囲であり、更に３０℃から１０００℃までの平均熱膨張係数α_{３０ − １０００ ℃}も本発明範囲内にある。この結果、熱膨張曲線は点線内に収まり、この範囲に熱膨張曲線をもつセラミックス材料との熱膨張差を小さくすることが可能である。Ｎｏ．２、３も本発明合金であり、Ｎｏ．１と同様の結果が得られている。
一方、Ｎｏ．４、６は、Ｃｏ量と（Ｎｉ＋Ｃｏ）量がともに低く、またα_２／α_１も大きな値を示す。この時の熱膨張曲線は図２の如くであり、本発明指定のセラミックス材料とは熱膨張特性が大きく異なっている。
Ｎｏ．５は、（Ｎｉ＋Ｃｏ）量、Ｔ_Ａとも本発明範囲を大きくはずれている。これにより、熱膨張曲線の傾き（熱膨張係数）は図２のように大きくなり、本発明指定のセラミックス材料と接合部材を形成しようとした場合には、大きな熱応力が発生してしまうことになる。
Ｎｏ．７は、（Ｎｉ＋Ｃｏ）量がわずかに低いだけでなく、更に過剰のＴｉとＮｂが添加されている。このため、Ｔ_Ａは、Ｔｉ、Ｎｂを含有しない同組成のものより更に１００℃以上低くなっており、１０００℃までの広い温度領域において、セラミックス材料の熱膨張と整合性を持たせることが極めて困難となる。
以上の結果から、本発明の低熱膨張合金を用いた低熱膨張合金板は、セラミックス材料との熱膨張係数の整合性が図れているのが分かり、低熱膨張合金板を用いたセラミックス材料との接合用の低熱膨張合金板として好適である。
【００２４】
【発明の効果】
本発明の低熱膨張合金は、例えばセラミックス材料との熱膨張係数の整合性を最適化可能なものであり、その低熱膨張合金を低熱膨張合金板として、更に低熱膨張合金板を用いたセラミックス材料との接合用合金板とすると、例えば１０００℃までの高温領域で使用される用途や、あるいは常温と１０００℃までの高温領域を昇温／降温される熱サイクルを受けるような用途に好適となる。
【図面の簡単な説明】
【図１】本発明の熱膨張曲線を示す図である。
【図２】比較例の熱膨張曲線を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a low-thermal-expansion alloy, a low-thermal-expansion alloy plate made of the low-thermal-expansion alloy, and a low-thermal-expansion alloy plate for joining a ceramic material using the low-thermal-expansion alloy plate.
[0002]
[Prior art]
Low-thermal-expansion alloys are used for various purposes such as materials for joining with ceramic materials, shadow mask materials, lead frame materials, core wires of overhead power transmission lines, and various shapes such as plate materials and wire materials. It is used after being processed into a shape.
Among them, Fe-Ni-Co alloys are known to have excellent low thermal expansion characteristics, and are referred to as 31Ni-5Co-Fe super-invar alloys and 29Ni-17Co-Fe alloys. The present applicant has also made many proposals for an alloy called Kovar. (For example, refer to Patent Document 1.)
[0003]
[Patent Document 1]
JP-A-6-279945 (Chemical composition of claim 1)
[0004]
[Problems to be solved by the invention]
The alloy disclosed in Patent Document 1 described above proposes an alloy that is optimal for a core wire of an overhead power transmission line having both low thermal expansion characteristics and high strength characteristics.
By the way, the characteristics of an alloy are not determined only by the chemical composition, but the characteristics greatly change depending on the difference in the metal structure. This can be applied to Fe—Ni—Co alloys. For example, the alloy disclosed in Patent Document 1 sacrifice low thermal expansion characteristics to some extent by forming a mixed structure of austenite and martensite. On the other hand, high strength that can withstand application to overhead transmission lines is being achieved.
On the other hand, even with the same Fe-Ni-Co-based alloy, a demand for high strength is not required up to the above-mentioned overhead transmission line. For example, in Kovar or Super Invar, the metal structure is an austenitic single phase structure. This is because the austenite structure reduces the coefficient of thermal expansion in a low temperature range from room temperature to 100 ° C. or 200 ° C. at most.
That is, the Fe-Ni-Co alloy has an alloy having completely different properties such as a coefficient of thermal expansion and mechanical properties due to a change in the metal structure.
[0005]
By the way, in the Fe-Ni-Co-based alloy having a low coefficient of thermal expansion as the austenitic single phase structure, it is bonded to, for example, a ceramic material having a low coefficient of thermal expansion by utilizing its low coefficient of thermal expansion. Although there is a use in a high temperature environment of up to 800 ° C., if the low thermal expansion property is maintained up to a temperature range exceeding 800 ° C., further expansion of the use can be expected.
Many ceramic materials exhibit excellent heat resistance and abrasion resistance at high temperatures. However, properties such as toughness and electrical conductivity are generally inferior to metal materials.
Therefore, if there is a material (member) having both the advantages of a ceramic material and the advantage of a metal, the industrial value is extremely high as a functional member that can be used in a high-temperature environment. As such a member, a joining member of a metal / ceramic material can be considered.
[0006]
However, when a member in which a metal and a ceramic material are joined is used in a high-temperature environment, thermal stress is generated in the joint due to a difference in thermal expansion between the two, and the joint is destroyed in a process of undergoing a thermal cycle. . The greater the temperature difference in the environment in which it is used, the greater the difference in thermal expansion between the metal / ceramic material and the more likely it is for the joint to break.
For example, as a low thermal expansion alloy used for bonding with a ceramic material, Incoloy 903 (Fe-38Ni-15Co-3Nb-1.4Ti-0.7Al alloy) and Incoloy 904 (Fe-32.5Ni-14.5Co-2) are used. Commercially available alloys such as Fe- (20-32) Ni- (16-30) Co- (0.5-2.5) Ti disclosed in Japanese Patent Application Laid-Open No. 4-218642. Alloys containing-(3.0-6.0) Nb as a main component are known.
[0007]
However, these alloys are used at most at 800 ° C. or lower, and elements such as Al, Ti, and Nb are used to strengthen the precipitation of the γ ′ phase in order to obtain high strength in combination with low thermal expansion characteristics. Has been added. Since the slope of the thermal expansion curves of these alloys is the temperature at which displacement (T _A) is not necessarily high, the difference in thermal expansion between the ceramic material at high temperatures, for example up to 1000 ° C. has a problem that still greater.
An object of the present invention is to use a low-thermal-expansion alloy capable of optimizing the matching of a thermal expansion coefficient with a ceramic material up to, for example, 1000 ° C., a low-thermal-expansion alloy plate made of the low-thermal-expansion alloy, and further using the low-thermal-expansion alloy plate. To provide a low-thermal-expansion alloy plate for joining with a ceramic material.
[0008]
[Means for Solving the Problems]
The present inventors have studied the use of a low-thermal-expansion alloy that can optimize the matching of the thermal expansion coefficient with, for example, a ceramic material. As a result, in the case of an alloy containing Fe, Ni, and Co as basic constituent elements, the T _{A of} the alloy and the coefficient of thermal expansion α ₁ on the low temperature side from T _A and the coefficient of thermal expansion α _{2 of} 1000 ° C. from T _A are obtained. The inventors have found that the ratio α ₂ / α ₁ can be controlled independently, and that the difference in thermal expansion between the ceramic material and the ceramic material can be made extremely small over a wide temperature range, thereby leading to the present invention.
[0009]
That is, the present invention contains C: less than 0.06%, Ni: 20% or more, Co: 27% or more, and (Ni + Co): 50% to 70% by mass, and the total amount of other elements 2.0% or less, an alloy having an austenitic single phase structure consisting of the balance Fe, and the average thermal expansion coefficient alpha ₁ to the slope of the displacement point of the thermal expansion curve (T _a) from 30 ° C., from T _a the ratio of the average thermal expansion coefficient alpha ₂ to 1000 ℃ α ₂ / α ₁ is 2.1 or less, _{T a} is the low thermal expansion alloy which is a 500 to 750 ° C..
The present invention also provides a low thermal expansion alloy plate made by using a low thermal expansion alloy described above, the low thermal expansion alloy plate has an average thermal expansion coefficient of up to 30 ℃ ~1000 ℃ 9.0 × 10 - from ^{6 /} ° C. 13.0 × 10 ^- is ⁶ / ° C. a low thermal expansion alloy plate.
Further, the low thermal expansion alloy plate of the present invention described above is a low thermal expansion alloy plate for joining with a ceramic material used for joining with a ceramic material.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail. In the present invention, the amounts of elements are described as mass% unless otherwise specified.
C: less than 0.06% C is important as a deoxidizing element at the time of dissolution, and is also an element having an effect of stabilizing the austenite phase, and a small amount of addition is permissible. However, when the content is 0.06% or more, graphite and cementite are thermally stabilized, and thus there is a concern that these may be precipitated. If these precipitate during the thermal cycle, the thermal expansion characteristics change and cause thermal stress at the joint, or the austenite phase becomes unstable and easily transforms to martensite by deformation at room temperature or lower. I am worried that it will be lost. For this reason, C must not be contained at 0.06% or more. A preferred upper limit is 0.02%, and more preferably 0.01%. Note that a desirable lower limit of C is 0.002%.
[0011]
Ni: 20% or more Ni is a ferromagnetic element and is one of the most important elements for constituting the alloy of the present invention. The addition of Ni lowers the martensitic transformation temperature and stabilizes the austenite phase. In this regard, the Ni content needs to be 20% or more in order to obtain a sufficient effect when a joined body with a ceramic material is obtained. A preferred lower limit for more reliably obtaining the effect of Ni is 22%, and more preferably 23%.
[0012]
Co: 27% or more Co are ferromagnetic element similar to the Fe and Ni, which is a kind of the most important elements in constructing a large effect as the invention alloy to enhance T _A. In this regard, the Co content needs to be 27% or more in order to obtain a sufficient effect when a joined body with a ceramic material is obtained.
A preferable lower limit for more surely obtaining the effect of Co is 30%, and more preferably 33%.
The displacement point (T _A ) of the slope of the thermal expansion curve referred to in the present invention means that the thermal expansion curve drawn when the temperature is raised from room temperature is accompanied by the disappearance of ferromagnetism near the Curie temperature of the alloy. It is defined as the point where the slope begins to increase.
[0013]
(Ni + Co): 50% or more and 70% or less In the alloy of the present invention, it is important to appropriately control not only the above-mentioned contents of Ni and Co but also the amount of (Ni + Co).
Α ₂ / α ₁ of the alloy of the present invention mainly depends on the amount of (Ni + Co). In order for the alloy of the present invention to maintain good bondability with a ceramic material, particularly at a high temperature of 1000 ° C., it is necessary to keep the α ₂ / α ₁ value small.
If the value of α ₂ / α ₁ is too large, a region is generated which is significantly different from the thermal expansion curve of the ceramic material during the temperature cycle from 30 ° C. to 1000 ° C. In such a region, a large thermal stress is generated in the joint due to a difference in thermal expansion between the two, and a break occurs. Thus, in order to reduce the value of α ₂ / α ₁ , it is necessary to adjust the amount of (Ni + Co), and the lower limit must be 50% or more.
In the present invention, it is necessary to adjust the amount of Ni and Co so that the α ₂ / α ₁ value is 2.1 or less. For that purpose, in addition to the adjustment of the total amount of Ni and Co, adjustment of a metal structure described later is also important. If the value of α ₂ / α ₁ exceeds 2.1, for example, the bondability with a ceramic material cannot be maintained. Therefore, in the present invention, the value of α ₂ / α _{1 is} set to 2.1 or less. It is desirably 1.7 or less, and it is better to approach 1 as much as possible.
[0014]
Further, (Ni + Co) weight also affects the value of _{T A} of the alloy. That is, with increasing (Ni + Co) weight, _{T A} is a tendency to increase roughly.
However, alloys such as with T _A below 500 ° C., in order coefficient of thermal expansion of less T _A is small, the thermal expansion coefficient difference of the present invention alloy and ceramic material in the low-temperature region increases. On the other hand, in the _{alloy T A} exceeds 750 ° C., thermal expansion coefficient is greater below _{T A.}
Therefore, it will particularly become thermal expansion difference is very large in a high temperature range than T _A, alloy / thermal stress in the bonding portions of the ceramic material will happening disrupted stored. Therefore, the _{T A} is required to be 500 to 750 ° C..
To this _{T A} and a proper range of α ₂ / α ₁ values described above should be 50% to 70% range of (Ni + Co) weight. It is more preferably in the range of 54 to 64%, and still more preferably in the range of 58 to 62%.
Then, after adjusting to this range, the metal structure to be described later is adjusted.
[0015]
The low thermal expansion alloy specified in the present invention has the above-mentioned range as long as it does not generate a large thermal stress at the joint with the ceramic material when used in a high-temperature thermal cycle environment from 30 ° C. to, for example, 1000 ° C. In addition to C, Ni, Co and the balance of Fe, the following elements can be present.
Mn: <1.0%, Si: <0.5%, P: <0.1%, S: <0.1%, Mg: <0.08%, Al: <0.8%, N: <0.1%, Mo: <1.0%, (Ti + Nb + V + Ta + Hf + Zr): <0.1%
However, the above-mentioned elements exist in a range that does not generate a large thermal stress at the joint when a member obtained by joining the alloy of the present invention and the ceramic material is used in a high-temperature thermal cycle environment of, for example, 30 ° C. to 1000 ° C. That can be done.
If these other elements exceed 2.0%, the strength increases due to solid solution strengthening, making it difficult to deform, and the stress due to the difference in thermal expansion is applied more to the ceramic material side, and the bonding interface with the ceramic material is increased. It is necessary that the total amount of these other elements be 2.0% or less, since there is a risk of peeling or destruction of the ceramic material.
[0016]
Next, in the present invention, an austenitic single phase structure was defined. This is to obtain a stable low thermal expansion characteristic even under a temperature cycle environment. When a phase or carbide having another crystal structure is generated due to the influence of heat treatment or the like, the thermal expansion coefficient is increased, and not only a large thermal stress is generated at the joint between the alloy and the ceramic material, but also the above α ₂ / alpha ₁ value and T _A deviates from the range defined in the present invention. Therefore, in the present invention, adjustment of the metal structure is also important in addition to the above-described chemical composition.
The austenitic single phase structure referred to in the present invention refers to a structure in which the austenite phase accounts for 99% or more in volume fraction among the constituent phases of the material, and whether or not the austenitic single phase structure is determined by X-ray diffraction. It is possible to roughly grasp in the device.
[0017]
As described above, the alloy of the present invention can control the thermal expansion characteristics from 30 ° C. to 1000 ° C. However, when the alloy of the present invention is used by being joined to a ceramic material, Is important with the thermal expansion coefficient.
At that time, it is preferable to process the shape according to the shape of the ceramic material. Many ceramic materials to be joined with the low thermal expansion alloy have a plate-like shape, and the alloy of the present invention is preferably processed into a plate-like shape in order to enhance the joining property.
In the alloy of the present invention, as described above, it is possible to adjust the coefficient of thermal expansion up to a high temperature range of, for example, 1000 ° C. by an appropriate chemical composition. At this time, the range of the average coefficient of thermal expansion from 30 ° C. to 1000 ° C. of the alloy sheet of the present invention is 9.0 × 10 ⁻⁶ / ° C. to 13.0 × 10 ⁻⁶ / ° C. Good matching of the coefficient of thermal expansion with the ceramic material is obtained.
Zirconia is an example of a ceramic material that is optimal for the thermal expansion characteristics of the alloy plate of the present invention. The coefficient of thermal expansion for obtaining better bondability with zirconia is from 9.5 × 10 ⁻⁶ / ° C. to 12.5 × 10 ⁻⁶ / ° C., preferably 10.0 × 10 ⁻⁶ / ° C. / ° C to 12.0 × 10 ⁻⁶ / ° C.
[0018]
As described above, in the joined body of the combination of the low thermal expansion alloy and the ceramic material of the present invention, the use in the high temperature region up to 1000 ° C. or the temperature increase / decrease in the high temperature region up to room temperature and 1000 ° C. This is suitable for applications that undergo a thermal cycle.
In this case, the shape of the low-thermal-expansion alloy is not particularly limited, whether it is a wire or a plate. However, if the low-thermal-expansion alloy is a plate as described above, a ceramic material can be fixed to the surface of the plate. For example, it is possible to expand applications to substrate materials for semiconductor devices, engine members for automobiles and airplanes, and further to energy-related members such as power generation plants such as solid oxide fuel cells.
[0019]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples.
Alloys having the compositions shown in Table 1 were produced by vacuum melting. “Others total” shown in Table 1 is a total amount of all elements other than Fe, Ni, Co, and C, and is an amount including elements other than those shown in Table 1.
[0020]
[Table 1]

[0021]
The above No. After hot-forging the alloys Nos. 1 to 7, hot rolling was performed to obtain a sheet material having a thickness of 12 mm. The obtained sheet material was annealed at 800 ° C. for 30 minutes and air-cooled. From this plate material, a test piece for measuring thermal expansion having a length of 20 mm is taken, and from a temperature of 30 ° C. to 1000 ° C. by a differential expansion measuring method in which a comparative measurement with a standard sample of SiO ₂ is performed at a heating rate of 10 ° C./min. A thermal expansion curve in the process of raising the temperature was prepared.
The thermal expansion curves obtained from each alloy are shown in FIGS. The dotted lines shown in the figure are the thermal expansion curves of the thermal expansion coefficients of 9.0 × 10 ⁻⁶ / ° C. and 13.0 × 10 ⁻⁶ / ° C., respectively. Table 2, also referred T _A and alpha _{2 /} alpha ₁ of the values determined from these thermal expansion curve.
In addition, a test piece for X-ray diffraction was also collected from the same plate from which the test piece for measuring thermal expansion was collected, and it was confirmed that the austenite phase had a single phase structure occupying 99% or more by volume fraction.
[0022]
[Table 2]

[0023]
From the results of FIGS. In 1, the alloy composition, (Ni + Co) weight, _{T A,} alpha both ₂ / alpha ₁ is the range of the present invention, further the average thermal expansion coefficients from 30 ° C. to _{1000 ℃} α _{30 -} 1000 ℃ also within the scope the present invention is there. As a result, the thermal expansion curve falls within the dotted line, and it is possible to reduce the difference in thermal expansion from the ceramic material having a thermal expansion curve in this range. No. Nos. 2 and 3 are also alloys of the present invention. The result similar to 1 is obtained.
On the other hand, No. In Nos. 4 and 6, both the Co amount and the (Ni + Co) amount are low, and α ₂ / α ₁ also shows a large value. The thermal expansion curve at this time is as shown in FIG. 2, and is significantly different from the ceramic material specified in the present invention in thermal expansion characteristics.
No. 5 is deviated larger (Ni + Co) weight, _{T A} with the present invention range. As a result, the slope (coefficient of thermal expansion) of the thermal expansion curve becomes large as shown in FIG. 2, and a large thermal stress is generated when an attempt is made to form a joining member with the ceramic material specified in the present invention. Become.
No. No. 7 has not only a slightly lower (Ni + Co) content but also an excess of Ti and Nb. Thus, T _A is, Ti, Nb and lower further 100 ° C. or higher than that of the same composition not containing, in a wide temperature range up to 1000 ° C., very be provided with thermal expansion and integrity of the ceramic material It will be difficult.
From the above results, it can be seen that the low thermal expansion alloy plate using the low thermal expansion alloy of the present invention achieves the consistency of the coefficient of thermal expansion with the ceramic material, and joining with the ceramic material using the low thermal expansion alloy plate It is suitable as a low thermal expansion alloy plate for use.
[0024]
【The invention's effect】
The low-thermal-expansion alloy of the present invention can optimize the matching of the coefficient of thermal expansion with, for example, a ceramic material. Is suitable for use in, for example, a high-temperature region up to 1000 ° C., or a use in which a heat cycle of raising and lowering the temperature between room temperature and a high-temperature region up to 1000 ° C. is adopted.
[Brief description of the drawings]
FIG. 1 is a diagram showing a thermal expansion curve of the present invention.
FIG. 2 is a diagram showing a thermal expansion curve of a comparative example.

Claims (3)

By mass%, C: less than 0.06%, Ni: 20% or more, Co: 27% or more, and (Ni + Co): 50% or more and 70% or less, and the total amount of other elements is 2.0%. hereinafter, an alloy having an austenitic single phase structure consisting of the balance Fe, an average of from 30 ° C. and the average thermal expansion coefficient alpha ₁ to the slope of the displacement point of the thermal expansion curve (T _a), to 1000 ° C. from T _{a A} low thermal expansion alloy characterized by having a ratio α ₂ / α ₁ to a thermal expansion coefficient α ₂ of 2.1 or less and TA of 500 to 750 ° C. A low thermal expansion alloy plate made by using a low thermal expansion alloy of claim 1, the low thermal expansion alloy plate has an average thermal expansion coefficient of up to 30 ° C. to 1000 ° C. is 9.0 × 10 - ^{6 /} ℃ from 13 .0 × 10 - low thermal expansion alloy plate, characterized in that ^{6 /} a ° C.. The low thermal expansion alloy plate according to claim 2, wherein the low thermal expansion alloy plate is used for joining with a ceramic material.

Images