JPH0672290B2 - High strength low thermal expansion alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a high strength and low thermal expansion iron-based alloy,
It is suitable for applications requiring low thermal expansion characteristics and strength at room temperature and high temperature, such as materials for joining with ceramics, materials for precision equipment parts, and materials for aircraft parts.

[Prior Art] Conventional low thermal expansion alloys include Fe-Ni alloy Invar alloy (36% Ni-Fe) or Fe-Ni-Co alloy Kovar alloy (29% Ni-17% Co-Fe), super alloy. Invar alloy (30% Ni
-5% Co-Fe) is well known, but although these alloys have low thermal expansion coefficients, they have low strength as structural materials and room temperature strength can only be secured by cold working.
At high temperatures, the effect of cold working disappeared and it was difficult to secure strength.

Further, as a low thermal expansion alloy having high strength, a Ni-Span C alloy (42% Ni-5% Cr-2.4% Ti-0.5% Al-Fe) containing a precipitation strengthening element such as Al, Ti or Nb, or Incolo
y 903 alloy (38% Ni-16% Co-1.5% Ti-1% Al-3% Nb-F
e) and the like are known, and these alloys have high strength at room temperature or high temperature, but the coefficient of thermal expansion from room temperature to 400 ° C is higher than that of silicon nitride or silicon carbide, which is a typical structural ceramic. large.

[Problems to be Solved by the Invention] When ceramics are to be used as a structural material, they are bonded to a metal material or used as a composite material with a metal material in order to compensate for defects such as brittleness of the ceramics. It is often done.

When metals and ceramics are used in a bonded or compounded state, if the coefficients of thermal expansion of the metals and ceramics differ greatly, cracks or peeling will occur at the joints between the metals and ceramics, and they will be used as structural materials. There's a problem. or,
In the structural material in which ceramics and metal are bonded or combined, the metal material is required to have strength at room temperature and high temperature in order to take advantage of the heat resistance and lightness of ceramics. However, when the metal material is used by being bonded or compounded with ceramics and the strength is higher than necessary, problems such as workability occur.

Therefore, it has been desired to develop a metal material having a thermal expansion coefficient relatively close to that of silicon nitride or silicon carbide, which is a typical structural ceramic, and having strength at room temperature and high temperature.

Further, it is desirable that the materials for precision equipment parts, aircraft parts materials, etc. are lightweight and have high room temperature and high temperature strength in view of operating temperature conditions, and the dimensional change due to thermal expansion is as small as possible. It has been desired to develop a material having strength at high temperature.

In view of the above points, the present invention has characteristics that cannot be obtained with conventional alloys, that is, the coefficient of thermal expansion from room temperature to 400 ° C. is 6.5 × 10 ^−6.
/ ℃ below in which tensile strength at room temperature tensile strength of 60~130kgf / mm ² 400 ℃ to provide a high strength low thermal expansion alloy exhibiting 40~100kgf / mm ^2.

[Means for Solving the Problems] The first invention of the present invention is as follows.

% By weight Ni: 29% or more and less than 34% Co: More than 16% and 21% or less (however, Ni + Co: 50% or less) Mo: 0.5% or more and 3.0% or less Ti: 0.8% or more and 3.0% or less Al: 0.2 % Or more and 1.5% or less C: 0.1% or less Si: 1.0% or less Mn: 1.0% or less, and the balance Fe and impurities, and the tensile strength at room temperature is 60 kgf / mm ² due to solid solution treatment and aging treatment.
Tensile strength of ~130kgf / mm ^2, 400 ℃ is 40kgf / mm ² ~100kgf / m
m ^2, the average thermal expansion coefficient of 6.5 × 10 ^-6 at 400 ° C. from room temperature
High-strength, low thermal expansion alloy having a temperature of / ° C or less.

Further, the second invention contains W instead of the above Mo, and the third invention contains both Mo and W.

That is, by containing a predetermined amount of Mo and W in the Ni-Co-Fe alloy individually or in combination, the increase in the thermal expansion coefficient is suppressed to the minimum and the solid solution strengthening in the austenite matrix is achieved. It was found by experiments that the yield strength is increased and the high temperature strength is improved. By further adding Ti and Al and performing aging treatment, it was found that the increase in the coefficient of thermal expansion is minimized, an intermetallic compound called a gamma prime phase is generated, and it has the effect of precipitation strengthening the alloy. It was This alloy is characterized by solid solution strengthening of Mo and W and aging strengthening of Ti and Al. By adjusting the contents of the alloys, it is possible to obtain alloys having characteristics that cannot be obtained by conventional alloys. I found it.

That is, the tensile strength at room temperature is 60 kgf / mm ^{2 to} 130 kgf / mm ² , 4
Tensile strength at 00 ℃ is 40kgf / mm ² ~ 100kgf / mm ² , room temperature to 400
An average thermal expansion coefficient at 6.5 ° C. of 6.5 × 10 ⁻⁶ / ° C. or less is obtained.

Next, the reasons for limiting each chemical component will be described.

Ni: Ni forms an austenite phase together with Co and contributes to the reduction of the thermal expansion coefficient. Further, by performing an aging treatment, an intermetallic compound called a gamma prime phase represented by Ni ₃ (Al, Ti) is formed and precipitation strengthened. If the Ni content is less than 29% or more than 34%, the coefficient of thermal expansion increases, so the content is limited to 29% or more and less than 34%.

Co: Co forms an austenite phase together with Ni, and has the effect of shifting the Curie point where the thermal expansion curve shows a break point to the high temperature side, and contributes to the reduction of the thermal expansion coefficient up to the high temperature region. In the temperature range from room temperature to 400 ° C, the low coefficient of thermal expansion is obtained in the range of more than 16% and 21% or less, so Co is limited to this range.

Ni + Co: Ni and Co are effective in forming the austenite phase and lowering the coefficient of thermal expansion up to a high temperature region as described above.
When the amount of + Co exceeds 50%, the Curie point temperature shifts to the high temperature side, but the coefficient of thermal expansion increases up to the Curie point, and the coefficient of thermal expansion from room temperature to 400 ° C also exceeds 6.5 × 10 ^-6 / ° C. Therefore, the amount of Ni + Co is limited to 50% or less.

Mo: Mo has a solid solution strengthening action by forming a solid solution in the austenite matrix, is effective in increasing the yield strength, and contributes to the improvement of high temperature strength, but 0.5% or more is necessary to obtain a sufficient effect. Is required, and the thermal expansion coefficient increases if the addition amount is large, so the content is limited to 0.5% or more and 3% or less.

W: W also has a solid solution strengthening action by forming a solid solution in an austenite matrix like Mo, and it is also effective in increasing proof stress and contributing to improvement in high temperature strength, but in order to obtain a sufficient effect. is 0.
It is necessary to add 5% or more, and if the addition amount is large, the coefficient of thermal expansion increases, so it is limited to 0.5% or more and 3% or less.

Mo + W: The combined addition of Mo and W also has the effect of strengthening the solid solution of the austenite base, has the effect of increasing the yield strength, and contributes to the improvement of the high temperature strength, but in order to obtain a sufficient effect , Mo
It is necessary to add + W of 0.5% or more. Also, if the amount of addition of Mo + W is large, the coefficient of thermal expansion increases.
It is limited to 0.5% or more and 3% or less.

Ti: Ti, together with Al, forms a gamma prime phase Ni ₃ (Al, Ti) by aging treatment, precipitation strengthens the alloy and improves high temperature strength. However, if the addition amount is less than 0.8%, the addition effect is small, and if it exceeds 3.0%, the coefficient of thermal expansion increases, so the content is limited to 0.8% or more and 3.0% or less.

Al: Al coexists with Ti to form a gamma prime phase Ni ₃ (Al, Ti) by aging treatment, precipitation strengthening the alloy and improving high temperature strength. However, if the addition amount is less than 0.2%, the effect is small, and if it exceeds 1.5%, the coefficient of thermal expansion increases, so the content is limited to 0.2% or more and 1.5% or less.

C: C forms a carbide and contributes to the improvement of high temperature strength, but excessive addition increases the coefficient of thermal expansion, so 0.1%
Limited to:

Si: Si is necessary for deoxidation and improvement of hot workability, but excessive addition increases the coefficient of thermal expansion, so it is limited to 1% or less.

Mn: Mn, like Si, is necessary for deoxidation and improvement of hot workability, but excessive addition increases the coefficient of thermal expansion, so it is limited to 1% or less.

The present invention is a solid solution treatment and aging treatment of the alloy material having such a composition, the conditions are solution treatment temperature 950 ~ 1150 ℃, aging temperature 580 ~ 750 ℃, aging time is About 5 to 48 hours is preferable. If the solution treatment temperature is lower than 950 ° C, solution treatment is insufficient, and if it exceeds 1150 ° C, coarsening of crystal grains occurs, so the temperature is set to 950 ° C to 1150 ° C. The aging treatment temperature is preferably 580 to 750 ° C, and this temperature range is preferred because excellent room temperature and high temperature strength can be obtained.

[Examples] In order to compare the characteristics, the table shows the chemical compositions of the conventional alloy, the alloy of the present invention and the comparative alloy, and the tensile strength at room temperature and 400 ° C.
0.2% proof stress and coefficient of thermal expansion from room temperature to 400 ° C are shown.

Each of the samples shown in the table is obtained by melting a 10 kg ingot in a vacuum induction melting furnace and then forging it to a diameter of 15 m / m.

The heat treatment of each sample is as follows.

Sample No. 1 (Invar alloy), Sample No. 2 (Super Invar alloy) and Sample No. 3 (Kovar alloy) were subjected to solution treatment by heating at 850 ° C. for 1 hour.

Sample No. 4 (Ni-SpanC alloy) was heated at 950 ° C. for 1 hour, cooled with water, and then subjected to an aging treatment at 730 ° C. for 5 hours.

Sample No. 5 (Incoloy 903 alloy) was heated at 950 ° C for 1 hour, water-cooled, further heated at 718 ° C for 8 hours, and then heated to 621 ° C.
The furnace was cooled at a cooling rate of 55 ° C./hour, further heated at 621 ° C. for 8 hours and then air-cooled.

Samples other than Sample Nos. 7 and 13 of the present invention alloy and Samples Nos. 18 to 27 of comparative alloys were each heated at 980 ° C. for 1 hour and then subjected to a solution treatment of water cooling, and further subjected to an aging treatment at 620 ° C. for 24 hours. Was carried out.

Further, the sample No. 7 of the alloy of the present invention is the same dissolved sample as the sample No. 6, and after the solution treatment under the same conditions as the sample No. 6, the aging treatment was carried out at 580 ° C. for 24 hours.

Sample No. 13 was the same dissolution sample as Sample No. 12, and after performing the solution treatment under the same conditions as Sample No. 12, aging treatment was performed at 650 ° C for 24 hours.

From each sample obtained in this way, a sample with a diameter of 5 mm and a length of 50 mm was taken as a sample for measuring the thermal expansion coefficient, and the thermal expansion coefficient from room temperature to 400 ° C was measured.
Take a 6 mm x 24 mm (between gauge marks) tensile test piece and store it at room temperature and 400
A tensile test at ° C was performed.

In the table, among conventional alloy Nos. 1-5, room temperature and 400
Samples No. 4 and No. 5 have high strength at ℃, and Sample No. 3 with low thermal expansion coefficient has low strength.

Sample No. 9, No. 6 and Sample No. 11 of the present invention have a Mo content of 0.6%, 0.9% and 2.8%, respectively, and the tensile strength at room temperature and 400 ° C and the 0.2% proof stress are improved as the Mo content increases. However, the coefficient of thermal expansion also increases. Sample No. 18 is an example in which the Mo content is 3% or more, and the strength at room temperature and 400 ° C. is good, but the coefficient of thermal expansion shows a large value of 7.4 × 10 ⁻⁶ / ° C.

Similarly, in the alloy samples No. 8 and No. 14 of the present invention, the W contents are 1.1% and 2.7%, respectively, and the tensile strength at room temperature and 400 ° C and the 0.2% proof stress improve as the W content increases, but The expansion coefficient also increases. Sample No. 19 is an example in which the W content is 3% or more, and the strength at room temperature and 400 ° C. is good, but the coefficient of thermal expansion shows a large value of 7.6 × 10 ⁻⁶ / ° C.

Sample No. 17 is an example in which Mo + W is the upper limit of 2.9%, and sample No. 20 is an example in which Mo + W is 3% or more. As the amount of Mo + W increases, the tensile strength and 0.2% proof stress at room temperature and 400 ° C improve, but sample No. 20 with 4.1% Mo + W has a thermal expansion coefficient of 7.7 × 10 ^-6 / ° C. It shows a large value.

Samples No. 6, No. 12, No. 16 and No. 21 are examples of Ti addition amounts of 1.0%, 1.8%, 2.8% and 3.4%, respectively. As the Ti content increases, the strength at room temperature and 400 ° C improves, but T
Sample No. 21 with an i content of 3.4% has a large coefficient of thermal expansion of 7.6 × 10 ^-6 / ° C.

Sample No. 15 is a sample in which Al, Si and Mn are close to the upper limit. Al
The thermal expansion coefficient of Sample No. 22 with an amount of 2.1% is 6.9 × 10 ^-6 / ° C.
However, due to the large amount of Ti, at room temperature and 400
The strength at ℃ is high.

Sample No. 7 and Sample No. 13 are obtained by changing the aging conditions of Sample 6 and Sample 12, respectively, but the coefficient of thermal expansion hardly changes and the strength at room temperature and 400 ° C can be adjusted. Therefore, even with the same component, the required strength can be secured by changing the aging treatment conditions.

Sample No. 9 and Sample No. 10 are Ni lower limit (Co upper limit) respectively
And the upper limit of Ni (lower limit of Co), the content of Ni + Co is 50% or less. On the other hand, Samples No.23 to No.27 have Ni content and Co
The amount or Ni + Co amount is out of the scope of claims of the patent. The strength at room temperature and 400 ° C was good, but the coefficient of thermal expansion showed a large value of 7.5 to 9.7 × 10 ^-6 / ° C.

[Effects of the Invention] The alloy of the present invention has a tensile strength of 60 kgf / mm ^{2 to} 130 kgf / m ^{2 at} room temperature.
High strength of 40kgf / mm ^{2 to} 100kgf / mm ² at m ² and 400 ° C.
Moreover, the average coefficient of thermal expansion from room temperature to 400 ° C is 6.5 × 10
^-6 or less and small. Therefore, it is optimal for applications such as bonding materials for structural ceramics, materials for precision equipment parts, materials for aircraft parts, etc., which require low thermal expansion characteristics and strength at room temperature and high temperature.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuyuki Uchibori 1-9-31 Shinonome, Koto-ku, Tokyo Mitsubishi Steel Mfg. Co., Ltd. Technology Development Center (56) Reference JP-A-62-182165 (JP, A) Kosho 31-10507 (JP, B1)

Claims (3)

[Claims] [Claim 1] Ni: 29% or more and less than 34% by weight Co: 16% or more and 21% or less (however, Ni + Co: 50% or less) Mo: 0.5 or more and 3.0% or less Ti: 0.8% or more and 3.0% Below Al: 0.2% to 1.5% C: 0.1% or less Si: 1.0% or less Mn: 1.0% or less and balance Fe and impurities, and the tensile strength at room temperature is 60 kgf / mm ²
Tensile strength of ~130kgf / mm ^2, 400 ℃ is 40kgf / mm ² ~100kgf / m
m ^2, the average thermal expansion coefficient of 6.5 × 10 ^-6 at 400 ° C. from room temperature
High-strength, low thermal expansion alloy having a temperature of / ° C or less. [Claim 2] Ni: 29% or more and less than 34% by weight Co: 16% or more and 21% or less (however, Ni + Co: 50% or less) W: 0.5 or more and 3.0% or less Ti: 0.8% or more and 3.0% Below Al: 0.2% to 1.5% C: 0.1% or less Si: 1.0% or less Mn: 1.0% or less and balance Fe and impurities, and the tensile strength at room temperature is 60 kgf / mm ²
Tensile strength of ~130kgf / mm ^2, 400 ℃ is 40kgf / mm ² ~100kgf / m
m ^2, the average thermal expansion coefficient of 6.5 × 10 ^-6 at 400 ° C. from room temperature
High-strength, low thermal expansion alloy having a temperature of / ° C or less. 3. By weight%, Ni: 29% or more and less than 34% Co: Over 16% and 21% or less (however, Ni + Co: 50% or less) Mo: 3.0% or less W: 3.0% or less (however, Mo + W: 0.5% to 3.0%) Ti: 0.8% to 3.0% Al: 0.2% to 1.5% C: 0.1% or less Si: 1.0% or less Mn: 1.0% or less and the balance Fe and impurities to form a solid solution. The tensile strength at room temperature is 60kgf / mm ² by applying heat treatment and aging treatment.
Tensile strength of ~130kgf / mm ^2, 400 ℃ is 40kgf / mm ² ~100kgf / m
m ^2, the average thermal expansion coefficient of 6.5 × 10 ^-6 at 400 ° C. from room temperature
High-strength, low thermal expansion alloy having a temperature of / ° C or less.