JP2001011580A - LOW TEMPERATURE STABLE TYPE Ni-Co-Fe BASE LOW THERMAL EXPANSION ALLOY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an Ni-Co-Fe base alloy suitable for low temp. region corresponding type precision apparatus in which γ to martensitic transformation at low temp. is suppressed. SOLUTION: This alloy contains, by weight, 30.0 to 34.0% Ni and 4.5 to 6.5% Co, and the balance Fe with inevitable impurities, in which XT:(%Co)+2.8(%Ni) is found from the contents of Ni and Co so as to control the range free from martensitic transformation in a prescribed temp. region, the components are controlled in such a manner that the XT satisfies the inequality of 93 <= XT=(%Co)+2.8(%Ni)}<=99, and its thermal expansion coefficient is <=1.0×10-6/ deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-temperature stable Ni-Co-Fe-based low thermal expansion alloy which prevents transformation when used or exposed to a low temperature and is applied to precision equipment.

[0002]

2. Description of the Related Art In recent years, the development of ultra-precision processing machines that enable the advancement of high-precision processing techniques in the field of semiconductors and the like has been active. In such an ultra-precision processing machine, the demand for improvement in accuracy is becoming severer year by year, and it is important to maintain and further improve the accuracy of the processing machine. Since the processing machine has many heat sources, it is unavoidable that the processing accuracy will decrease due to thermal deformation. For this reason, low thermal expansion materials with a small coefficient of thermal expansion are used in fields such as optical equipment, precision measurement equipment, and control equipment. It is frequently used in A so-called super-invar alloy having a nominal composition of 32% Ni-5% Co-Fe alloy is used. As shown in Table 1, the average thermal expansion coefficient of this 32% Ni-5% Co-Fe alloy is as extremely small as 1 × 10 ⁻⁶ / ° C. or less.

[0003]

[Table 1]

[0004]

Further, diversification of the use environment and transportation routes makes it possible to improve accuracy in a low-temperature region, such as in a cold region where the device is temporarily exposed to a low temperature during use or transportation. Stable use is strongly desired. 3 above
When a 2% Ni-5% Co-Fe alloy (super Invar alloy) is placed in a low temperature range of zero degree or less, a so-called γ → martensitic transformation occurs. For this reason, martensite transformation, which is a non-diffusion transformation, causes remarkable expansion, deteriorating dimensional accuracy and low thermal expansion characteristics, and there is a problem in use in a low temperature range.

In view of the above situation, the present invention relates to a Ni--Co--Fe alloy material used for a control device material,
It is an object of the present invention to provide a Ni-Co-Fe-based alloy which has a low expansion coefficient without causing γ-> martensite transformation in a low temperature range below zero degree and which can be stably handled at a temperature equal to or higher than zero degree.

[0006]

The gist of the present invention for solving the above-mentioned problems is as follows. (1) By weight%, Ni: 30.0 to 34.0%, Co:
4.5 to 6.5%, with the balance being Fe and unavoidable impurities, and from the Ni and Co contents to X in such a range that martensitic transformation does not occur within a predetermined temperature range.
_T: (% Co) +2.8 sought (% Ni), that the X _T is component adjustment so as to satisfy the following relationships, the thermal expansion coefficient of 1.0 × 10 ^-6 / ℃ or less A low-temperature stable Ni-Co-Fe-based low thermal expansion alloy characterized by the following.

93 ≦ ΔX _T = (% Co) +2.8 (% N
i)｝ ≦ 99 (2) In (1), the Ni and Co contents are adjusted so as to be within the region I surrounded by the points A, E, F, and J in the relationship shown in FIG. Low temperature stable Ni— characterized by not causing martensitic transformation in the temperature range above
Co-Fe low thermal expansion alloy.

(3) In (1), the contents of Ni and Co are adjusted so as to fall within a region II surrounded by points B, E, F and I in the relationship shown in FIG. A low-temperature stable Ni-Co-Fe-based low-thermal-expansion alloy characterized by not causing martensitic transformation in the above temperature range. (4) In (1), the contents of Ni and Co are adjusted so as to fall within a region III surrounded by points C, E, F, and H in the relationship shown in FIG. Low temperature stable Ni characterized by not causing martensitic transformation
-Co-Fe based low thermal expansion alloy.

(5) In (1), the contents of Ni and Co are adjusted so as to fall within a region IV surrounded by points D, E, F, and G in the relationship shown in FIG. A low-temperature stable Ni-Co-Fe-based low-thermal-expansion alloy characterized by not causing martensitic transformation in the above temperature range.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, when a low thermal expansion alloy is exposed to a low temperature, the temperature range is 0 ° C., -20 ° C.
C., -30.degree. C., and even a lower temperature range, such as -80.degree. When the present inventors are exposed to such a low temperature range, the present inventors have found that a so-called Super Invar alloy (usually 32
(Ni-5Co-Fe alloy) undergoes γ (austenite) → martensite transformation, whose transformation temperature is Ni, C
It was found that it depends on the amount of the o component. As shown in FIG.
In the i-Co-Fe alloy system, the γ → martensite transformation temperature depends on the amount of (% Co) +2.8 (% Ni).

From this figure, it can be seen that at -20 ° C., (% Co)
It can be seen that the range satisfying +2.8 (% Ni) ≧ 93 is a stable range in which γ → martensitic transformation does not occur. Similarly, in the case of −40 ° C., (% Co) +2.8 (%
Ni) ≧ 95.3 is a stable region where γ → martensitic transformation does not occur, and in the case of −60 ° C., (% C
o) The range of +2.8 (% Ni) ≧ 95.7 is a stable range in which γ → martensitic transformation does not occur.

In the case of a lower temperature of -80 ° C.,% Co +
It can be seen that the component region of 2.8 (% Ni) ≧ 96 is a stable region where γ → martensitic transformation does not occur. In accordance with the low temperature range used in this manner, Ni-
The present inventors have found that a Co component system can be selected and achieved the present invention.
Note that X _T is Co and Ni for martensitic transformation.
Can be treated as a parameter representing the degree of contribution. In other words, it is also a parameter of austenite stability in the present 32Ni-5Co-Fe alloy.

The reasons for limiting the chemical components in the present invention will be described. First, as for Ni and Co of the Ni-Co-Fe low thermal expansion alloy, martensitic transformation is prevented, expansion due to transformation is avoided, and temperature stability is imparted, depending on the operating temperature range as described above. Is what you do. Other components are not particularly limited, but preferred ranges are as follows. As for C, if it exceeds 0.05%, the coefficient of thermal expansion becomes high from the viewpoint of securing the strength and workability as a precision mechanical device.
This is preferred. For Si, 0.50%
If it exceeds, the coefficient of thermal expansion becomes high, so that it is preferably less than this.

Further, when Mn exceeds 0.5%, the coefficient of thermal expansion becomes high.
Hereinafter, the reasons for limitation corresponding to the claims of the present invention will be specifically described. As described above, in order to use a Ni-Co-Fe alloy stably in a low temperature range, a range of Ni and Co components corresponding to the operating temperature range is selected and γ is used without causing martensite transformation. Maintaining the organization in a stable manner is the first characteristic.

Therefore, this N
Low thermal expansion coefficient (<
1.0 × 10 ⁻⁶ / ° C.), as shown in FIG. 1, the upper limit range of Ni—Co (% Co) + 2.8 × (% N
i) ≤ 99, 4.5% ≤ Co ≤ 6.5% and 30.0%
It is important to control the range of ≦ Ni ≦ 34.0%.

That is, as a more severe condition, the low temperature region -8
In the case of 0 ° C, the region IV (D (89.5,
6.5), E (92.5, 6.5), F (94.5,
4.5), G (91.5, 4.5)) corresponds to Ni-Co
Component range. In the case of a low temperature range of −60 ° C., regions III (C (89.2, 6.5) and E (92.
5,6.5), F (94.5, 4.5), H (91.
2,4.5)) is the corresponding Ni-Co component range.

In the case of a low temperature range corresponding to -40 ° C., the region shown in FIG.
II (B (89.2, 6.5), E (92.5, 6.
5), F (94.5, 4.5), I (90.8, 4.
5)) is the corresponding Ni-Co component range. Low temperature range-2
In the case of 0 ° C., the region I (A (86.5,6.
5), E (92.5, 6.5), F (94.5, 4.
5) and J (88.5, 4.5)) are the corresponding Ni-Co component ranges. Note that all the lines on the boundary line are included.

[0018]

Embodiments of the present invention will be described below. In this example, in each of the above-described low-temperature regions, after performing sub-zero treatment (holding at each temperature for 2 hours), the structure was observed, and the alloy of the present invention was compared with a comparative example. FIGS. 3A and 3B show a typical metal structure of this example. In this figure, FIG. No. 1 -80 ° C. sub-zero treated material, FIG. 4 is a micrograph showing the structure of the -80 ° C. sub-zero treated material No. 4 observed. In FIG. (A), all austenite is present, and in FIG. (B), martensite is generated. Thus, in FIG. 5B, it is determined that there is a martensite transformation.

Low temperature stable type Ni-Co-Fe according to the present invention
The low thermal expansion alloys according to the present invention correspond to the respective claims as shown in Tables 2 and 3. From this table, it can be seen that by controlling the amounts of Ni and Co along with Co + 2.8Ni, γ → martensite transformation does not occur even when exposed to a predetermined low temperature range, and the coefficient of thermal expansion from room temperature to 100 ° C. is also 1. 0 × 10 ^-6
/ ° C or less, a value equivalent to that of the conventional Super Invar alloy is obtained.

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

According to the present invention, even when a low thermal expansion Ni-Co-Fe alloy is transported in a cold region or used,
→ It can be used stably without causing martensitic transformation, it can obtain a low thermal expansion coefficient equivalent to that of conventional Super Invar alloy, and it can maintain processing accuracy in ultra-precision machines .

[Brief description of the drawings]

FIG. 1 is a diagram showing a component adjustment region of Ni and Co according to the present invention.

FIG. 2 is a view showing a martensitic transformation behavior by a component according to the present invention.

FIG. 3 shows a metal structure according to an example of the present invention, and (a)
No. No. 1 -80 ° C. sub-zero treated material, (b) No. 4-8
It is a figure which shows a 0 degreeC sub-zero processing material.

Claims (5)

[Claims] 1. Ni: 30.0 to 34.0% by weight.
%, Co: 4.5-6.5%, the balance being Fe and unavoidable impurities, and Ni and Co such that the martensitic transformation does not occur within a predetermined temperature range.
From the content X _T: (% Co) +2.8 sought (% Ni), the X _T is component adjustment so as to satisfy the following relationships, the thermal expansion coefficient of 1.0 × 10 ^-6 / ℃ A low-temperature stable Ni-Co-Fe-based low thermal expansion alloy characterized by the following. 93 ≦ {X _T = (% Co) +2.8 (% Ni)} ≦ 99 2. The method according to claim 1, wherein the contents of Ni and Co are adjusted so as to fall within a region I surrounded by points A, E, F, and J in the relationship shown in FIG. A low-temperature stable Ni-Co-Fe-based low thermal expansion alloy characterized by not causing martensitic transformation in a temperature range. 3. The method according to claim 1, wherein the Ni and Co contents are adjusted so as to fall within a region II surrounded by points B, E, F, and I in the relationship shown in FIG. A low-temperature stable Ni-Co-Fe-based low thermal expansion alloy characterized by not causing martensitic transformation in a temperature range. 4. The method according to claim 1, wherein the Ni and Co contents are adjusted so as to fall within a region III surrounded by points C, E, F, and H in the relationship shown in FIG. A low-temperature stable Ni-Co-Fe-based low thermal expansion alloy characterized by not causing martensitic transformation in a temperature range. 5. The method according to claim 1, wherein the Ni and Co contents are adjusted so as to fall within a region IV surrounded by points D, E, F, and G in the relationship shown in FIG. A low-temperature stable Ni-Co-Fe-based low thermal expansion alloy characterized by not causing martensitic transformation in a temperature range.