JPH11293413A - Member of ultraprecision equipment using alloy steel excellent in thermal shape stability and rigidity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the member for an ultraprecision equipment excellent in thermal shape stability and rigidity. SOLUTION: Alloy steel having a componental compsn. contg., by weight, <=0.1% C, 0.1 to 0.4% Si, 0.15 to 0.4% Mn, >2 to 4% Ti, <=1% Al, 30.7 to 43.0% Ni and <=14% Co, in which Ni and Co also satisfy the inequality of 37.7<=Ni+0.8×Co<=43, and the balance Fe with inevitable impurities, in which the thermal expansion coefficient in the temp. range of -40 to 100 deg.C is regulated to <=4×10<-6> / deg.C, and the Young's modulus is regulated to >=16,100 kgf/mm<2> is used to produce a member. The alloy steel is moreover incorporated with one or >= two kinds of components selected from the group of V, W, Nb and Mo by <=1% in total and/or is incorporated with one or >= two kinds of components selected from the group of S, Pb, Ca and Se by <=0.5% in total.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electronic equipment, semiconductor-related equipment, precision measuring equipment, precision machine equipment, and optical equipment, and uses a material having excellent rigidity as well as thermal shape stability. The present invention relates to jigs and bases used for ultra-precision processing and ultra-precision polishing, arms of exposure equipment, frames of precision equipment, and parts and surface plates of other ultra-precision equipment.

[0002]

2. Description of the Related Art In recent years, thermally stable Invar alloy has been used as a component material for electronics, semiconductor-related equipment, laser processing machines, and even ultra-precision processing equipment.
Its demand tends to increase significantly. In these ultra-precision devices, in addition to thermal deformation, minute elastic deformation
This is a problem in maintaining high precision of the equipment. However, the Young's modulus of the conventional material is as small as about two-thirds of that of general steel. Therefore, for example, in a long product such as a sensor support, there is a problem that a vibration amplitude generated with the operation of the device is large.

[0003] In order to solve the above-mentioned problem, conventionally, high rigidity design has been performed in which the dimensions are increased, for example, by increasing the thickness of a target part or the like. Therefore, the weight of the target component and the like increases with the conventional material as compared with the general material, and the weight of the device cannot be avoided.

Further, in recent years, these ultra-precision devices tend to be further enlarged, and the invar alloy parts and super invar alloy parts used for the respective parts have to be increased in size to increase the unit weight. The weight of the device manufactured in such a manner has reached a design limit such as a floor strength of a building that accommodates the device or ascends and descends, and a capability of the elevating equipment.

On the other hand, as a high Young's modulus low thermal expansion alloy based on high Ni containing about 30 to 40 wt.
Alloy steel material to which V and any of Cr, Mo and W are added (Japanese Patent Publication No. 6-76646, hereinafter referred to as “prior art 1”)
Alloy cast iron material to which martensitic transformation by cryogenic treatment is applied (for example, JP-A-6-179938, hereinafter referred to as "prior art 2"), and Al;
Alloy cast iron material obtained by adding at least one of Ti, Nb and Ta and precipitating a Ni-Al-based intermetallic compound by aging treatment (Japanese Patent Application Laid-Open No. Hei 7-179984, hereinafter referred to as "prior art 3") and the like It has been known.

On the other hand, as high-strength materials, iron-based martensitic alloys and nickel-based aging-precipitated alloys (hereinafter, referred to as “alloys”)
Many of them exist, but the coefficient of thermal expansion is about 14 to 23 × 10 ⁻⁶ / ° C., which is not sufficiently small. Therefore, it cannot be used as a component material for semiconductor-related equipment, laser processing machines, and even ultra-precision processing equipment that require high precision.

[0007]

SUMMARY OF THE INVENTION By using an alloy material having both a low coefficient of thermal expansion and a high Young's modulus in the production of jigs and tools for ultra-precision instruments and parts and surface plates, the use of ultra-precision instruments The weight can be reduced, and the weight of the devices can be stably kept within the design strength range of the building corresponding to the installation. Then, the present inventors set the following targets in order to achieve this object.

First, the coefficient of thermal expansion is stably maintained at 4 × 10 ⁻⁶ / ° C. or less, which is regarded as the conventional level, and the Young's modulus is regarded as the conventional level, 130.
The 00kgf / mm ² just under an alloy material capable of ensuring this is increased to 16100kgf / mm ^2, and was produced in an easy process of manufacturing, tooling and parts and constant ultraprecision equipment and used to I decided to manufacture boards.

Looking at the prior art from the above viewpoint, prior art 1 is limited to a shadow mask for a cathode ray tube and cannot be used as a structural body. There is an operational problem in the production of heavy materials, and the prior art 3 is not sufficient from the viewpoint of securing a high Young's modulus, and according to experiments by the inventors, when C is contained in a large amount, as described later, Ti It is linked to C and has the knowledge that the expected improvement cannot be obtained. Further, prior art 4 is not sufficient in terms of securing a low coefficient of thermal expansion.

[0010] Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide jigs and tools for ultra-precision equipment, which are manufactured using materials having both contradictory characteristics of low thermal expansion and high rigidity. Another object of the present invention is to provide parts and surface plates.

[0011]

SUMMARY OF THE INVENTION From the above-mentioned viewpoints, the present inventors have conducted studies to develop a member of an ultraprecision device using an alloy steel having excellent thermal shape stability and rigidity. As a target alloy steel material manufacturing process, use a combination of solution heat treatment and precipitation aging heat treatment instead of cryogenic treatment process, which is inferior in production operability when using large single weight materials. I made it. Then, a precipitation strengthening method for strengthening the material by precipitating fine Ni ₃ (Ti, Al) inside and outside the crystal grains by this process was studied.

However, when Ti or Al is added to a superinvar alloy having a Ni content of about 30 wt.% And a Co content of about 5 wt. It was found that the coefficient of thermal expansion sharply increased, which was disadvantageous. Thus, the present inventors have conducted further studies to solve this problem, and as a result, Ni
It has been found that the intended purpose can be advantageously achieved by adjusting the amount of addition of Ni and finding an appropriate range of Ni + 0.8Co.

The present invention has been made based on the above findings. The member of the ultra-precision device according to claim 1 is C:
0.1 wt.% Or less, Si: 0.1 to 0.4 wt.%, Mn:
0.15 to 0.4 wt.%, Ti: more than 2 to 4 wt.%, Al: 1
wt.% or less, Ni: 30.7 to 43.0 wt.%, and C
o: 14 wt.% or less, and the content of Ni and Co is less than the following formula (1): 37.7 ≦ Ni + 0.8 × Co ≦ 43 --------- Satisfies (1), has a component composition consisting of the balance of Fe and inevitable impurities, and has a thermal expansion coefficient of 4 × 10 ⁻⁶ in a temperature range of −40 ° C. to 100 ° C. / ° C. or less and a Young's modulus of 16100 kgf / mm ² or more, which is characterized by using an alloy steel excellent in thermal shape stability and rigidity.

According to a second aspect of the present invention, there is provided a member for an ultra-precision device, wherein the alloy steel having excellent thermal shape stability and rigidity according to the first aspect is further selected from the group consisting of V, W, Nb and Mo. It is characterized in that one or more of the above-mentioned components are contained in a total of 1 wt.% Or less.

According to a third aspect of the present invention, there is provided a member of an ultra-precision device, wherein the alloy steel having excellent thermal shape stability and rigidity according to the first aspect of the invention is further selected from the group consisting of S, Pb, Ca and Se. One or more of the components
It is characterized by containing less than wt.%.

According to a fourth aspect of the present invention, there is provided a member for an ultra-precision device, wherein the alloy steel having excellent thermal shape stability and rigidity according to the first aspect of the invention is further selected from the group consisting of V, W, Nb and Mo. 1 wt.% Or less of a total of 1 wt.% Or less of one or more components selected from the group consisting of S, Pb, Ca and Se. It is characterized by containing the following.

[0017]

Next, the present invention will be specifically described. The present invention is a member of an ultra-precision device manufactured using an alloy steel specified by the following chemical composition. Here, the members of the ultra-precision equipment include, specifically, surface plates and frames for a polishing machine and an exposure apparatus, frames for a non-contact thickness measuring machine, bases, columns and spindles for a precision grinding machine. , Laser oscillator base,
These are a CFRP mold, a telescope / microscope frame, and a lens support.

Next, the reason why the composition of the alloy steel is limited as described above will be described. (1) C: 0.1 wt.% Or less C has the effect of dissolving in austenite, contributing to the strengthening of the matrix, and improving the strength by combining with Ti to form carbide TiC. However, when C is contained in a large amount, the thermal expansion coefficient increases. Furthermore, when C is contained in a large amount, Ni is not significantly reduced in the precipitation aging heat treatment, which is extremely important in the present invention.
₃ Ti required for the precipitation of (Ti, Al) is consumed in a large amount for bonding with C, and this precipitate is not sufficiently generated. As a result, the Young's modulus, which is an important property of the material of the present invention, is reduced. If the upper limit of C exceeds 0.1 wt.%, T
The formation of iC reduces the improvement in Young's modulus, and
The ductility decreases significantly. From the above point of view, the content is limited to 0.1 wt.% Or less as a range in which C exerts its effect sufficiently and does not cause the above-mentioned adverse effects.

(2) Si: 0.1-0.4 wt.% Si is effective as a deoxidizing agent at the time of melting, and in order to exhibit its effect, the content of 0.1% by weight or more is required. I need. However, when the Si content exceeds 0.4 wt.%, The Curie point shifts to a lower temperature side, and the thermal expansion coefficient increases.

Therefore, the Si content is 0.1 to 0.4 w
Limited to the range of t.%. (3) Mn: 0.15 to 0.4 wt.% Mn effectively acts as a deoxidizing agent similarly to Si, and in order to exert its effect, the content of 0.15 wt.% Or more is required. . However, when the Mn content exceeds 0.4 wt.%, The coefficient of thermal expansion increases.

Therefore, the Mn content is 0.15 to 0.4.
Limited to the range of wt.%. (4) Ti: more than 2 to 4 wt.% Ti is converted into N by precipitation aging heat treatment after solution heat treatment.
It is an important element for improving the Young's modulus of the material of the present invention by precipitating and distributing the i-Ti intermetallic compound finely and uniformly inside and outside the crystal grains. However, Ti is C
It is also consumed in the generation of TiC due to the bonding with the Ti. Therefore,
If the Ti content is 2 wt.% Or less, the above effect cannot be sufficiently exhibited. On the other hand, if the Ti content exceeds 4 wt.%, The Curie point shifts extremely to a low temperature side, and the thermal expansion coefficient increases.

Therefore, the content of Ti is limited to the range of more than 2 to 4 wt.%. (5) Al: 1 wt.% Or less Al coexists with Ti, thereby precipitating and distributing the intermetallic compound of Ni- (Ti, Al) finely and uniformly inside and outside the crystal grains by precipitation aging heat treatment. It is an important element for improving the Young's modulus. However, when the Al content exceeds 1 wt.%, The Curie point shifts to a lower temperature side, and the thermal expansion coefficient increases. In addition, Al ₂ O ₃
A large amount of inclusions is formed, and the casting workability is deteriorated.

Therefore, the Al content is limited to 1 wt.% Or less. (6) Ni: 30.7-43.0 wt.% Ni is Ni- (Ti, Al) by precipitation aging heat treatment.
Is finely and uniformly precipitated and distributed inside and outside the crystal grains to improve the Young's modulus after aging. However, when the content is less than 30.7 wt.%, The thermal expansion coefficient sharply increases due to martensite transformation, and the thermal expansion coefficient cannot be suppressed to 4 × 10 ⁻⁶ / ° C. or less. On the other hand, if the Ni content exceeds 43.0 wt.%, The coefficient of thermal expansion increases due to a decrease in spontaneous volume magnetostriction. Therefore, N
The i content must be in the range of 30.7-43.0 wt.%.

Further, the most important feature of the present invention is
In order to prevent the coefficient of thermal expansion from increasing even if the Young's modulus is improved by adding Ti or Al, an operation of replacing a part of the Ni content with the addition of Co is performed. In order to exert the effect of replacing Co with Ni, the Ni content and the Co content must be set between the above formula (1): 37.7 ≦ Ni +
0.8 × Co ≦ 43 must be satisfied.

(7) Co: 14 wt.% Or less In the present invention, Co plays a particularly important role, and by partially replacing Ni with Co, the thermal expansion coefficient can be effectively reduced. In particular, the coefficient of thermal expansion reaches a minimum level near normal temperature when the Co content is 14w.
It is the case of t.% or less. A particularly preferred range is where Co is in the range of 2.0 to 10 wt.%.

In the present invention, by replacing a part of Ni with Co, even if Ti or Al is added to improve the Young's modulus, the coefficient of thermal expansion does not increase.
The coefficient of thermal expansion can be effectively reduced. N above
In order to exert the substitution effect of Co on i,
The content must satisfy the following relationship with the Ni content.

(8) 37.7 ≦ Ni + 0.8 × Co ≦ 43 As described above, Ni has an effect of improving the Young's modulus and
o has the effect of reducing the coefficient of thermal expansion. However, in order to effectively reduce the coefficient of thermal expansion, it is necessary to limit the Ni and Co contents within a certain range.

FIG. 1 shows the effect of Ni and Co on the coefficient of thermal expansion α.
The test result about the influence with a content rate is shown. In the figure, the region of the Ni and Co contents indicated by the hatched portions is a preferable region where the thermal expansion coefficient α ≦ 4 × 10 ⁻⁶ / ° C. is obtained.

On the other hand, Ni + 0.8 × Co> 4
In the region A, which is 3, a large amount of Ni and Co is contained, and the spontaneous volume magnetostriction is reduced, so that the coefficient of thermal expansion α is 4 × 1.
It rapidly increased from 0 ^-6 / ° C.

In the region B where Ni + 0.8 × Co <37.7, the martensitic transformation start temperature sharply rises, so that the coefficient of thermal expansion α was larger than 4 × 10 ⁻⁶ / ° C.

Areas A and B outside the shaded area
In the region C excluding the above, the amount of Ni that provides the spontaneous volume magnetostriction enough to effectively reduce the coefficient of thermal expansion near room temperature is not secured, and in part, martensitic transformation occurs. The coefficient α became larger than 4 × 10 ⁻⁶ / ° C.

The reasons for limiting the basic component composition are as described above. In the present invention, for the purpose of further improving the Young's modulus of the material, one or more of V, W, Nb and Mo are further added to the above-mentioned component composition, and for the purpose of improving machinability. , S, Pb, Ca and Se, one or more of them are added in required amounts, respectively, to obtain a more desirable material. Next, the reasons for limiting the composition of these selected components will be described.

(9) One, two or more of V, W, Nb and Mo are 1 wt.% Or less in total. V, W, Nb and Mo all combine with free C to form a carbide. And contributes effectively to the improvement of the Young's modulus. However, if their total content exceeds 1 wt.%, The coefficient of thermal expansion increases, so the content is limited to 1 wt.% Or less.

(10) Of S, Pb, Ca and Se, 1
0.5 wt.% Or less in total of two or more species S, Pb, Ca and Se are all useful elements for improving the machinability of the material, and are effective when added alone or in combination. Is done. However, if the total content exceeds 0.5 wt.%, Hot workability and castability are impaired. Therefore, they limit the total content to 0.5 wt.% Or less.

[0035]

Next, the present invention will be described in more detail with reference to examples. 30k having various component compositions shown in Table 1
g of molten metal was melted in a high frequency induction furnace and cast. The diameter of the ingot is 65 mm.

[0036]

[Table 1]

Steel type N having a component composition within the scope of the present invention
Of the ingots of o.1 to 14, steel types No.1 to 9 have the basic component composition, steel type No.10 added a selective element for improving Young's modulus, and steel type No.11 improved machinability. With the addition of selected elements for
Numeral 14 is an element to which both a selective element for improving Young's modulus and a selective element for improving machinability are added.

On the other hand, among the steel types Nos. 15 to 26 having a component composition outside the scope of the present invention, the steel types Nos. 25 and 26 are so-called invar alloys and superinvar alloys as conventional steels, respectively.

The following tests were performed using the above ingots. In addition, all the test pieces prepared using the ingots of steel types Nos. 1 to 14 are tests for members of ultra-precision equipment within the scope of the present invention.
Called 14. On the other hand, the test pieces prepared using ingots of steel types Nos. 15 to 26 are all tests for members of ultra-precision equipment outside the scope of the present invention, and are called Examples 1 to 12, respectively. .

Each ingot having a diameter of 65 mm was placed in 1050
Hot forging at a temperature within the range of
It was processed into a round bar of mm. However, Example 14 and Comparative Example 1
Only the ingot of 0 was directly cut into a round bar having a diameter of 13 mm without hot forging the ingot.

Next, after cutting the above-mentioned round bar into a predetermined length, a solution treatment at 1100 ° C. × 1 hr was performed.
An aging treatment of 00 ° C. × 4 hr was performed. From the test materials thus prepared, a Young's modulus measurement test piece, a thermal expansion coefficient measurement test piece, a hardness test piece, and a tensile test piece were produced. However, since the round bars of Comparative Examples 11 and 12 (Invar alloy and Super Invar alloy) do not contain Ti and Al for the purpose of precipitation strengthening, the test pieces were prepared without performing the solution treatment and the aging treatment. did.

The Young's modulus was measured by an ultrasonic pulse method using a test piece having a diameter of 21 mm × 10 mm. The coefficient of thermal expansion used a test piece of 8 mmφ × 50 mm length,
The temperature was measured between 0 and 100 ° C. at a heating rate of 1 ° C./min. Table 2 shows the test results.

[0043]

[Table 2]

The test results for the examples within the scope of the present invention are all good. Examples 1 to 9 are alloy steels composed of basic components. In each case, the coefficient of thermal expansion was as low as 4 × 10 ⁻⁶ / ° C. or less, and the Young's modulus was as large as 16500 kgf / mm ^2, and all achieved the targets.

Example 10 aimed at a material having a higher Young's modulus than the alloy steel of the basic component.
The total amount of W, Nb and Mo is added within the scope of the present invention. The thermal expansion coefficient achieves the target value of 4 × 10 ⁻⁶ / ° C. or less, and the Young's modulus is more excellent at 18800 kgf / mm ² .

Example 11 aimed at a material having more excellent machinability than the alloy steel of the basic component.
Is added within the scope of the present invention. The thermal expansion coefficient achieves the target value of 4 × 10 ⁻⁶ / ° C. or less, and the tool life is more excellent at 340 sec.

In Examples 12 to 14, the group consisting of V, W, Nb and Mo, as well as S, P, were aimed at a material having both higher Young's modulus and machinability than the alloy steel of the basic component.
b, the components of both groups of the group consisting of Ca and Se, respectively
It is added within the scope of the present invention. In each of the examples, the coefficient of thermal expansion was set to a target value of 4 × 10 ⁻⁶ / ° C.
Example 1 which achieves the following and is an alloy steel as a basic component
The Young's modulus and machinability are significantly improved as compared with Nos. To 7. Incidentally, the cast product (Example 14) is also a forged product (Example 12).
And 13) have good thermal expansion coefficient, Young's modulus and machinability.

In contrast, comparisons outside the scope of the present invention
All examples show targets for thermal expansion coefficient or Young's modulus.
Has not been achieved. Comparative Example 1 was Ni + 0.8 × Co
The value is smaller than the lower limit of the range of the present invention.
Belongs to, the martensitic transformation occurs and the thermal expansion coefficient
9.6 × 10 ^-6/ ° C, and in Comparative Example 2
i + 0.8 × Co value is larger than the upper limit of the range of the present invention.
And belongs to the region A, so that the spontaneous volume magnetostriction decreases,
Thermal expansion coefficient around normal temperature is 5.7 × 10^-6/ ℃ and large value
showed that. On the other hand, in Comparative Example 3, the Ni + 0.8 × Co value was
Within the scope of the present invention, 37.7-43,
Ni content is 30.01 wt.%, Which is lower than the range of the present invention.
And belongs to the region C, the thermal expansion coefficient is 8.8 × 10
^-6/ ° C, which is larger than the target upper limit.

In Comparative Example 4, since the C content was too high than the upper limit of the present invention and the martensitic transformation occurred at -40 ° C. or higher, the thermal expansion coefficient was 7.6 × 10 ⁻⁶ / ° C., which is the target upper limit. It cannot be larger than the value.

In Comparative Examples 5 and 6, both Ni + 0.8
Since the value of × Co is larger than the range of the present invention, the thermal expansion coefficients are 4.5 × 10 ⁻⁶ / ° C. and 4.6 × 10 ^{−6, respectively.}
/ ° C, which is larger than the target upper limit.

Comparative Example 7 shows that Co content and Ni + 0.8
Since the values of × Co are all higher than the range of the present invention, the coefficient of thermal expansion is 4.2 × 10 ⁻⁶ / ° C., which is slightly larger than the target upper limit.

In Comparative Example 8, the content of W + Mo was higher than that of the present invention.
Limit of 1.0 wt.%, And the Al content of the present invention
Because it is higher than the upper limit, the Young's modulus is 16100kg
f / mm ^Two Good enough, but the coefficient of thermal expansion is
5.3 × 10^-6/ ° C and not higher than the target upper limit
You.

In Comparative Example 9, the V + Nb content was higher than the upper limit of 1 wt.
Although it is sufficiently larger than 0 kgf / mm ² and good, the thermal expansion coefficient is 5.8 × 10 ⁻⁶ / ° C., which is larger than the target upper limit and cannot be achieved.

In Comparative Example 10, a test material having a cast structure was subjected to aging heat treatment to precipitate and strengthen it. Since the Ti content is higher than the upper limit of 4 wt.% Of the present invention, the Young's modulus is sufficiently larger than the target value of 16100 kgf / mm ² and is good.
The thermal expansion coefficient is 6.8 × 10 ⁻⁶ / ° C., which is larger than the target upper limit and cannot be achieved. Since the total content of S, Pb, Ca and Se is 0.77 wt.%, The machinability is good and the tool life is long. However, castability was poor.

In each of Comparative Examples 11 and 12, since neither Al nor Ti was contained, the aging heat treatment was not performed. Both have small thermal expansion coefficients and are excellent, but have a small Young's modulus of 14000 kgf / mm ² and a target value of 16100 kgf / mm ^2.
mm ² has not been achieved.

In Example 15, a sensor column was manufactured by casting molten steel having a composition of steel type No. 19 in Table 1 using a 500 kg high frequency induction furnace. When the Young's modulus of the product itself was measured, it was 17,400 kgf / mm ² .

[0057]

As described above, according to the present invention,
An alloy steel having not only a small coefficient of thermal expansion but also a large Young's modulus can be obtained, and a member of an ultra-precision device using the same can be provided. Therefore, since the above-mentioned equipment members are excellent in rigidity as well as thermal shape stability, they can be reduced in weight, and there is no need to change the strength design of the building accommodating the equipment members or the loading equipment. It is possible to provide such a member of ultra-precision equipment, and an industrially useful effect is obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing test results on the effects of Ni and Co contents on thermal expansion coefficient α.

Continued on the front page (72) Inventor Yoshinobu Saito 23, Nishigaoka, Murata-machi, Shibata-gun, Miyagi Prefecture Tohoku Special Steel Co., Ltd.

Claims (4)

[Claims] 1. C: 0.1 wt.% Or less, Si: 0.1 to 0.4 wt.%, Mn: 0.15 to 0.4 wt.%, Ti: more than 2 to 4 wt.%, Al: 1 wt.% % Or less, Ni: 30.7 to 43.0 wt.%, And Co: 14 wt.% Or less, and the content of Ni and Co is expressed by the following formula (1): 37.7 ≦ Ni + 0. 8 × Co ≦ 43 satisfies (1), has a component composition consisting of the balance of Fe and inevitable impurities, and -40 An alloy steel having a thermal expansion coefficient in a temperature range of 4 ° C. to 100 ° C. of 4 × 10 ⁻⁶ / ° C. or less and a Young's modulus of 16100 kgf / mm ² or more and having excellent thermal shape stability and rigidity. Ultra-precision equipment components used. 2. The alloy steel further comprises one or more components selected from the group consisting of V, W, Nb and Mo in a total of 1 wt.% Or less, A member of an ultra-precision device using the alloy steel having excellent thermal shape stability and rigidity according to claim 1. 3. The alloy steel further comprises one or more components selected from the group consisting of S, Pb, Ca and Se in a total amount of 0.5 wt.% Or less. Do
A member of an ultra-precision device using the alloy steel having excellent thermal shape stability and rigidity according to claim 1. 4. The alloy steel further comprises one or more components selected from the group consisting of V, W, Nb and Mo in a total of 1 wt.% Or less, and S, Pb, Ca and 2. The composition according to claim 1, wherein one or more components selected from the group consisting of Se are contained in a total of 0.5 wt.% Or less.
A member of an ultra-precision device using an alloy steel having excellent thermal shape stability and rigidity as described above.