JP6925037B2 - Rust resistant low thermal expansion alloy - Google Patents

Description

The present invention relates to a low thermal expansion alloy, and more particularly to a low thermal expansion alloy having excellent rust resistance.

Thermally stable Invar alloys are widely used as component materials for electronics, semiconductor-related equipment, laser processing machines, and ultra-precision processing equipment.

Electronic components such as shadow masks for color receivers and IC lead frames manufactured using Invar alloy are subjected to extremely fine processing, blackened, and commercialized. In this microfabrication, a photoresist is applied to a thin plate of an Invar alloy, subjected to photosensitization and development, and selectively etched using the resist pattern as a mask.

When Invar alloy is used as a material for electronic parts, in addition to the good adhesion and etching properties of the photoresist, the etching maker causes rust on the surface of the thin plate during the period until the etching process is started. It is required that it does not change.

Patent Document 1 discloses a low thermal expansion alloy thin plate for electronic parts, which is suitable as a material for electronic parts and has excellent rust resistance. The low thermal expansion alloy thin plate of Patent Document 1 is characterized by containing Ni: 30 to 52 mass%, Cu: 0.01 to 0.1 mass%, and S: 10 to 20 mass ppm.

JP-A-2002-327249

The coefficient of thermal expansion of the Invar alloy disclosed in the patent document is not yet sufficient for recent demands.

An object of the present invention is to provide a low thermal expansion alloy having a further low coefficient of thermal expansion at room temperature and excellent rust resistance.

The present inventors have diligently studied a method for obtaining a low thermal expansion alloy having a low coefficient of thermal expansion and further excellent in rust resistance. As a result, it was found that rusting can be significantly reduced while suppressing an increase in the coefficient of thermal expansion by replacing a part of Co generally added to the Invar alloy with Cu.

The present invention has been made based on the above findings, and the gist thereof is as follows.

(1) In terms of mass%, C: 0 to 0.04%, Si: 0.15 to 0.35%, Mn: 0.25 to 0.45%, Cu: 1.5 to 3.0%, Ni A low thermal expansion alloy containing 31.0 to 34.0% and Co: 2.5 to 4.5%, the balance of which is Fe and unavoidable impurities.

(2) The low thermal expansion alloy according to (1) above, wherein the average coefficient of thermal expansion at 25 to 100 ° C. is 2.0 × 10 ^{-6 / ° C. or less.}

According to the present invention, it is possible to obtain a low thermal expansion alloy having a low coefficient of thermal expansion and further having excellent rust resistance.

It is a figure which shows the appearance after the immersion test in an Example.

Hereinafter, the present invention will be described in detail. Hereinafter, "%" regarding the component composition shall represent "mass%" unless otherwise specified. First, the component composition of the casting of the present invention will be described.

Ni is an essential element that lowers the coefficient of thermal expansion. If the amount of Ni is too large or too small, the coefficient of thermal expansion will not be sufficiently small. In order to sufficiently reduce the coefficient of thermal expansion, the amount of Ni is set in the range of 31.0 to 34.0%, preferably 32.0 to 32.8%.

Co contributes to a decrease in the coefficient of thermal expansion in combination with Ni. In order to obtain a desired coefficient of thermal expansion, the range of Co is 2.5 to 4.5%, preferably 3.2 to 3.8%.

Cu is an element that finely controls the form of sulfide formed by S contained as an impurity and improves rust resistance. In the low thermal expansion alloy of the present invention, the rust resistance is significantly increased by replacing a part of Co of the generally known superinvar alloy with Cu. In order to obtain this effect, the amount of Cu is set to 1.5% or more. On the other hand, if the amount of Cu is too large, the coefficient of thermal expansion increases, so the amount of Cu is set to 3.0% or less.

C dissolves in austenite and contributes to an increase in strength. As the C content increases, the coefficient of thermal expansion increases. Further, the ductility is lowered and casting cracks are likely to occur. Therefore, the content is set to 0.04% or less, preferably 0.01% or less. In the low thermal expansion alloy of the present invention, C is not an essential element and the content may be 0.

Si is an element that is effective as a deoxidizing material and enhances rust resistance. In order to obtain this effect, the amount of Si is 0.15% or more. Since the coefficient of thermal expansion increases when the amount of Si exceeds 0.35%, the amount of Si is set to 0.35% or less, preferably 0.30% or less.

Mn is added as a deoxidizing material. It also contributes to the improvement of strength by strengthening the solid solution. In order to obtain this effect, the amount of Mn is set to 0.20% or more. On the other hand, Mn is also an element that forms sulfide and inhibits rust resistance. The amount of Mn is set to 0.45% or less in order to suppress a decrease in rust resistance.

The rest of the composition is Fe and unavoidable impurities. The unavoidable impurities refer to those that are unavoidably mixed from the raw materials, the manufacturing environment, etc. when the steel having the component composition specified in the present invention is industrially manufactured. Specifically, P, N, S, O, Ca and the like of 0.02% or less can be mentioned.

By producing an alloy having the above chemical components by a known casting method, a low thermal expansion alloy having excellent rust resistance can be obtained.

The mold used for producing the low thermal expansion alloy of the present invention, the apparatus for injecting molten steel into the mold, and the injection method are not particularly limited, and known apparatus and methods may be used. Steel parts can be obtained by directly processing the produced cast alloy by cutting or the like, or by processing after forging.

The obtained cast alloy is subjected to solution treatment directly or after forging. In the solution treatment, the alloy is heated to 600 to 1000 ° C., preferably 750 to 850 ° C., held for 0.5 to 5 hr, and then rapidly cooled. The cooling rate is preferably 10 ° C./min or higher, more preferably 100 ° C./min or higher. Due to the solution formation, the precipitates precipitated during casting are solid-solved, and the ductility and toughness are improved.

After the solution treatment, if necessary, a known heat treatment such as stress relief annealing, which is held at 300 to 350 ° C. for 1 to 5 hours and then air-cooled, may be performed.

The low thermal expansion alloy of the present invention has excellent rust resistance. This effect can be confirmed, for example, by the number of rusts obtained by the wet test.

[Example 1]
Test materials used are the low thermal expansion alloy of the present invention having the component composition of alloy number 1 in Table 1, the conventional super Invar alloy containing 32.5% Ni and 5.2% Co, and stainless steel (SUS 403). Then, a cut having a width of 0.5 mm was made on the surface, and the surface was immersed in tap water for 1 month.

FIG. 1 shows the appearance after one month has passed. (A) is a low thermal expansion alloy of the present invention, (b) is a conventional super Invar alloy, and (c) is SUS 403. In the conventional Super Invar alloy, rust was observed in a wide range around the cut, but it was confirmed that the low thermal expansion alloy of the present invention suppressed rust as in SUS 403.

[Example 2]
Using a high-frequency melting furnace, Y blocks and ingots adjusted to have the component compositions shown in Table 1 were melted. After that, the Y block was subjected to solution treatment and used as a casting, and the ingot was subjected to hot forging and solution treatment to obtain a rust confirmation test piece and a thermal expansion coefficient measurement test piece, respectively.

In the rust confirmation test, a 35 x 25 x 10 mm thick test piece polished with emery paper is held in a constant temperature bath kept at a temperature of 80 ° C. and a humidity of 100% for 40 minutes, then taken out, and when the surface dries, it is put back in the constant temperature bath. The return was repeated 10 times, and the number of rusts appearing on the surface at that time was defined as the number of rusts, and when the number was 30 or less, it was judged to have rust resistance.

For the measurement of the coefficient of thermal expansion, the coefficient of thermal expansion was maintained at 830 ° C. for 2 hours, solution treatment with an average cooling rate of 200 ° C./min was performed, and after holding for 5 hours at 350 ° C., air-cooled stress relief annealing was performed to obtain an average coefficient of thermal expansion of 25 to 100 ° C. It was measured.

The alloy of the present invention had a coefficient of thermal expansion of 2 × 10 ^-6 / ° C. or less and a number of rusts of 30 or less. No characteristics were obtained.

Claims (2)

By mass%
C: 0-0.04%,
Si: 0.15-0.35%,
Mn: 0.25 to 0.45%,
Cu: 1.5-3.0%,
Ni: 31.0 to 34.0%, and Co: 2.5 to 4.5%
A low thermal expansion alloy containing Fe and the balance being Fe and unavoidable impurities. The low thermal expansion alloy according to claim 1, wherein the average coefficient of thermal expansion at 25 to 100 ° C. is 2.0 × 10 ^{-6 / ° C. or less.}

Images