KR20150034282A - Ni-based alloy having excellent hydrogen embrittlement resistance, and method for producing ni-based alloy material - Google Patents

Abstract

An object of the present invention is to provide a Ni-based alloy which has high strength and excellent hydrogen embrittlement characteristics even in a high-temperature and high-pressure environment, and which can be used particularly in a material for a cancer mono-thermal pressure vessel. The present invention is characterized by containing 30 to 40% of Fe, 14 to 16% of Cr, 1.2 to 1.7% of Ti, 1.1 to 1.5% of Al, 1.9 to 2.7% of Nb and 40 to 150 ppm of P by mass ratio , And the remainder being Ni and inevitable impurities.

Description

TECHNICAL FIELD The present invention relates to a Ni-based alloy material and a Ni-based alloy material excellent in hydrogen-

The present invention relates to a Ni-based alloy and a Ni-based alloy material excellent in hydrogen embrittlement resistance.

The mono-thermal method is known as a kind of a single crystal growth method, and the above-mentioned mono-thermal method is applied to, for example, growing a single crystal of gallium nitride which is a nitride semiconductor for a blue light-emitting diode.

Gallium nitride is expected to be used as an optical device such as a high-brightness LED or a semiconductor laser, or an electronic device used in an electric vehicle transistor, an amplifier for a cellular phone base station, and the like. For application to such a device, it is necessary to increase the size of the gallium nitride single crystal, and it is required to have a size of 2 inches or more to 6 inches or more, or even more.

Conventionally, the vapor phase growth method has been the mainstream for the growth of gallium nitride single crystals. However, in order to cope with the above-mentioned enlargement, mass production, or cost reduction of crystals, the mono-thermal method has been changed to grow crystals in high temperature and high pressure ammonia . Since the synthesis conditions in the ammonothermal method are almost 600 to 650 ° C and the pressure is 200 to 250 MPa, application of a Ni-Fe based alloy as a pressure vessel material having high strength under a high temperature environment has been attempted.

In the ammonothermal method, ammonia as a raw material is decomposed and a large amount of high-pressure hydrogen is generated because it is operated under high temperature and high pressure. Therefore, as the characteristics required for the pressure vessel material, those having excellent hydrogen embrittlement resistance at high temperature can be cited. Also, since it is used in a high temperature environment, creep characteristics are also required.

BACKGROUND ART [0002] Conventionally, various technologies relating to a Ni-Fe based alloy having high strength and excellent resistance to hydrogen embrittlement have been developed variously. For example, Patent Document 1 discloses a technique relating to an Fe-Ni based alloy which is used as a high-pressure hydrogen piping material for a hydrogen station and which is excellent in high strength and excellent resistance to hydrogen embrittlement. In this document, a piping material having a two-layer structure composed of an outer layer imparted with high strength by aging and an inner layer imparting hydrogen embrittlement resistance is proposed.

Patent Document 2 discloses a Ni-Fe alloy in which high strength and hydrogen embrittlement characteristics are exhibited by controlling the grain size of γ 'phase and the fraction of each precipitated phase.

Further, Patent Document 3 discloses a technique dealing with hydrogen embrittlement characteristics at a high temperature.

Japanese Patent Application Laid-Open No. 2010-174360 Japanese Patent Application Laid-Open No. 2009-68031 Japanese Patent Application Laid-Open No. H05-255788

However, in Patent Documents 1 and 2, it is unclear whether the temperature that is high in strength and excellent in hydrogen embrittlement resistance is room temperature and can guarantee such characteristics under high temperature and high pressure. Patent Document 3 deals with a high-Ni-base alloy having high strength and excellent resistance to hydrogen embrittlement which can be used at 200 to 500 ° C. However, as the alloy, the characteristics at 600 to 650 ° C, And there is no guarantee for the characteristics under high pressure.

As described above, conventional Ni-Fe based alloys having high strength and excellent resistance to hydrogen embrittlement can not guarantee such characteristics under the conditions to which the present invention is applied.

The present invention provides a method of producing a Ni-based alloy and a Ni-based alloy material having high strength and excellent hydrogen embrittlement resistance even at high temperature and high pressure such as 600 to 650 ° C and 200 to 250 MPa .

The present inventors have found out that by limiting the composition of a Ni-based alloy to a predetermined specific range, a Ni-based alloy having high strength and excellent hydrogen embrittlement resistance even at high temperature and high pressure can be obtained. That is, the gist of the present invention follows from the following <1> to <7>.

A steel plate comprising, as a mass ratio, 30 to 40% of Fe, 14 to 16% of Cr, 1.2 to 1.7% of Ti, 1.1 to 1.5% of Al, 1.9 to 2.7% of Nb and 40 to 150 ppm of P, And the remainder being Ni and inevitable impurities.

<2> The Ni-based alloy according to <1>, further containing at least one of Mg: not more than 0.01% and Zr: not more than 0.1% by mass ratio.

<3> In the above <1> or <2>, when each RA and RA _{H A} contraction in a tensile test in a hydrogen filling ratio and the hydrogen _{filling, EI = (RA A -RA H} ) / RA A &Lt; / RTI &gt; is less than or equal to 0.1 at 625 &lt; 0 &gt; C.

&Lt; 4 > A Ni-based alloy according to any one of < 1 > to < 3 >, wherein the creep rupture time at 700 DEG C and 333 MPa is 1,500 hours or more.

(5) The Ni-based alloy according to any one of (1) to (4), wherein the minimum creep rate at 700 ° C and 333 MPa is 1 × 10 ^-8 s ^-1 or less.

<6> The Ni-based alloy according to any one of <1> to <5>, wherein the Ni-based alloy is used in the material for the arm mono-thermal pressure vessel.

<7> The method for producing a Ni-based alloy material according to <1> or <2>, wherein the Ni-based alloy is subjected to a solution treatment and aging treatment is performed twice at a temperature of 825 to 855 ° C and a temperature of 710 to 740 ° C.

According to the present invention, it becomes possible to provide a Ni-based alloy having a good hydrogen embrittlement property at a high temperature of 600 ° C or higher and an excellent creep characteristic in a higher temperature region such as 700 ° C. Further, as an additional effect, by applying the Ni-based alloy to a pressure vessel material for a mono-thermal pressure, it becomes possible to manufacture a pressure vessel capable of coping with a higher temperature and a higher pressure environment. For example, The mass production, mass production, and low cost of the device will be greatly advanced.

Fig. 1 shows the relationship between the hydrogen embrittlement index and the P content of the inventive material and the comparative material.
Fig. 2 shows the relationship between creep stress and creep rupture time of the inventive material and comparative material.
3 shows the relationship between the creep test time and the creep speed of the inventive material and the comparative material.

Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to the following description, and can be appropriately modified and carried out without departing from the gist of the present invention.

Here, the terms "weight%", "weight ratio" and "weight ppm", "mass%", "mass ratio" and "mass ppm" have the same meanings, respectively.

The Ni-based alloy according to the present invention contains 30 to 40% of Fe, 14 to 16% of Cr, 1.2 to 1.7% of Ti, 1.1 to 1.5% of Al, 1.9 to 2.7% of Nb and P: To 150 ppm, and the balance being Ni and unavoidable impurities.

Further, it is more preferable to further contain at least one of Mg: not more than 0.01% and Zr: not more than 0.1%.

The reason why the alloy composition is determined will be described below. Hereinafter, the content of each element other than P is expressed in mass%, and P is expressed in mass ppm.

Fe: 30 to 40%

When Fe is contained in a large amount, the effect of reducing the cost of the alloy is effective. However, if Fe is contained excessively in addition to the Nb content, a Laves phase is generated, which causes deterioration of material characteristics such as increase in hydrogen embrittlement susceptibility. Therefore, the content of Fe is 30 to 40%. For the same reason, it is preferable to set the lower limit to 33% and the upper limit to 38%.

Cr: 14-16%

Cr is an element necessary for increasing the oxidation resistance, corrosion resistance and strength of an alloy. In addition, it combines with C to generate carbide, thereby increasing the high temperature strength. However, when the content is too large, destabilization of the matrix is caused, and the formation of harmful TCP phases such as σ phase and α-Cr is promoted and adversely affects ductility and toughness. Further, the sigma phase acts as a hydrogen accumulation site in the alloy, which may increase the susceptibility to hydrogen embrittlement. Therefore, the content of Cr is limited to 14 to 16%.

Ti: 1.2 to 1.7%

Ti mainly forms MC carbide to inhibit coarsening of crystal grains of the alloy, and also binds with Ni to precipitate a? 'Phase to contribute to precipitation strengthening of the alloy. However, if it is contained excessively, the stability of the? 'Phase at high temperature is lowered, and the? -Phase is formed, thereby deteriorating the strength, ductility, toughness and long- In addition, there is a fear that the hydrogen embrittlement susceptibility of the η-phase alloy acts as a hydrogen accumulation site. Therefore, the content of Ti is limited to the range of 1.2 to 1.7%.

Al: 1.1 to 1.5%

Al bonds with Ni to precipitate? 'Phase, which contributes to precipitation strengthening of the alloy. However, when the content is too large, the? 'Phase agglomerates and coarsens in the grain boundaries, not only significantly deteriorates the mechanical properties at high temperatures, but also lowers the hot workability. Therefore, the Al content is limited to 1.1 to 1.5%.

Nb: 1.9 to 2.7%

Nb is an element which stabilizes the? 'Phase and contributes to the increase in strength. However, if it is contained excessively, precipitation of the harmful η phase, σ phase and Laves phase is promoted, and the stability of the structure is markedly lowered, and the hydrogen embrittlement susceptibility is improved. Therefore, the content of Nb is limited to 1.9 to 2.7%.

P: 40 to 150 ppm

P is added because it is believed to have an effect of suppressing excessive accumulation of hydrogen in the grain boundaries by increasing the consistency of the grain boundaries and lowering the susceptibility to hydrogen embrittlement. In order to obtain the above effect, a P content of 40 ppm or more is required. Further, there is an effect that the creep rupture time is lengthened and the minimum creep speed is lowered. However, if it is contained excessively, P's grain boundary segregation becomes excessive, which in turn may lower the consistency of grain boundaries and may lose the effect of reducing the hydrogen embrittlement susceptibility. Therefore, the content of P is limited to 40 to 150 ppm. For the same reason, it is preferable to set the lower limit to 45 ppm and the upper limit to 140 ppm.

Mg: not more than 0.01%

Mg is mainly bound to S to form a sulfide, thereby enhancing hot workability. On the other hand, if the content is too large, the grain boundary will be brittle and the hot workability will deteriorate. Therefore, the content of Mg is preferably 0.01% or less. In order to sufficiently exhibit the above effect, the lower limit of the Mg content is more preferably 0.0005% or more.

Zr: not more than 0.1%

Zr is segregated in grain boundaries and contributes to improvement of high-temperature characteristics. However, if it is contained in excess, the hot workability of the alloy is lowered, so that the Zr is preferably 0.1% or less. In order to obtain the above effect, it is more preferable to contain 0.01% or more.

It is preferable that at least one of Mg and Zr is included in the above range, but it is more preferable that Mg and Zr are included together in terms of securing good hot workability.

The remainder of the Ni-based alloy according to the present invention is Ni and inevitable impurities.

Inevitable impurities are included in the alloy raw material from the beginning or are inevitable to be incorporated in the alloy solvent (solvent), and examples thereof include O, N, S and the like. The content of inevitable impurities in the entire Ni-based alloy is preferably as small as possible, and more preferably 50 ppm or less in terms of high purification of the alloy.

The Ni-based alloy of the present invention is excellent in hydrogen embrittlement resistance and can be preferably used as a material exposed to a hydrogen environment. Further, it is excellent in high-strength characteristics at high temperature and can be suitably used in a material for a cancer mono-thermal pressure vessel.

The Ni-based alloy of the present invention can be dissolved by a conventional method, and the method of the present invention is not particularly limited to the method of the solvent.

The Ni-based alloy of the present invention can be processed, for example, by forging or the like, and may be subjected to a solution treatment and a heat treatment (aging treatment) by aging.

The solution treatment can be carried out at, for example, 1040 to 1140 DEG C for 4 to 10 hours. The aging treatment is preferably carried out at least in two stages. For example, the aging treatment may be carried out twice at a temperature of 825 to 855 ° C and a temperature of 710 to 740 ° C. It is preferable that the aging treatment temperature is firstly carried out in the order of 825 to 855 DEG C (first stage) and then 710 to 740 DEG C (second stage). It is more preferable that the time of the aging treatment is 4 to 10 hours for the first step and 4 to 24 hours for the second step.

By adopting the conditions of the solution treatment and the aging treatment, a high tensile strength at room temperature and a high temperature of 600 DEG C or more can be ensured, respectively, and a Ni-based alloy material excellent in hydrogen embrittlement resistance can be obtained. The obtained tensile strength is preferably 1000 MPa or more at room temperature and 820 MPa or more at 625 占 폚.

If the temperature in the first stage of the aging treatment is lower than 825 ° C or above 855 ° C, the γ 'phase may not sufficiently grow and the tensile strength may not be secured.

If the temperature of the second stage of the aging treatment is less than 710 ° C, the M ₂₃ C ₆ type carbide excessively precipitates. If the temperature exceeds 740 ° C, the MC type carbide is coarsened. There is a risk of adverse effects.

When the shrinkage in the tensile test of the hydrogen-based filler and the non-hydrogen filler in the Ni-based alloy obtained above is RA _H and RA _A , respectively, the hydrogen embrittlement index EI defined as EI = (RA _A -RA _H ) / RA _A A Ni-based alloy capable of obtaining resistance to hydrogen embrittlement wherein the EI becomes 0.1 or less at 625 占 폚 is more preferable. Hydrogen filling simulates a hydrogen penetration of 50 ppm.

Further, among the Ni-based alloys obtained as described above, a Ni-based alloy capable of obtaining high-temperature creep characteristics in which the creep rupture time at 700 ° C and 333 MPa is 1,500 hours or more is more preferable.

Further, among the Ni-based alloys obtained above, Ni-based alloys capable of achieving high-temperature creep characteristics in which the minimum creep rate at 700 ° C and 333 MPa is 1 × 10 ^-8 s ^-1 or less are more preferable.

Further, the Ni-based alloy having the hydrogen embrittence index and the high-temperature creep property satisfies the above-mentioned composition conditions, and in particular, it can be obtained by containing P in an amount of 40 ppm or more.

The material using the Ni-based alloy according to the present invention can be used for a desired application in which hydrogen embrittlement resistance can be exhibited through plastic working, machining, and the like, and can be suitably used particularly in a material for a mono-thermal pressure vessel. As a result, for example, the size, mass production and cost reduction of the gallium nitride single crystal can be realized.

[Example]

Hereinafter, embodiments of the present invention will be described.

Solvent was obtained from the material of the round ingot of 50 kg by the vacuum induction melting method to obtain the composition shown in Table 1 and two kinds of inventive materials and two kinds of comparative materials, and they were forged into a plate shape.

The obtained forged plate was cut to an appropriate size, and subjected to a solution treatment at 1040 占 폚 for 4 hours and a two-step aging treatment at 840 占 폚 for 10 hours and then at 730 占 폚 for 24 hours, Comparative materials 1 and 2). Then, the test material was machined to obtain a tensile test piece and a creep test piece for evaluation of resistance to hydrogen embrittlement.

The hydrogen embrittlement characteristics were evaluated in the following order.

First, a specimen having a parallel portion of 10 mm and a length of 50 mm was held in an atmosphere of a temperature of 450 DEG C and a hydrogen pressure of 25 MPa for 72 hours, and hydrogen was filled. This hydrogen filling condition is set so as to simulate an amount of hydrogen of 50 ppm which is supposed to penetrate into the material in the actual ammonothermal method. A tensile test was conducted at 625 占 폚 using a hydrogen filler after hydrogen filling, and tensile strength and shrinkage were measured.

Tensile strength and shrinkage were similarly measured in a test piece (non-hydrogen filling material) that was not filled with hydrogen.

The hydrogen embrittlement resistance was evaluated by calculating the hydrogen embrittlement index EI defined by the following equation (1) by using the result of the tensile test at 625 占 폚 of the non-hydrogen filler.

The hydrogen embrittlement index EI = (RA _A -RA _H ) / RA _A ... (One)

Where RA _A is the contraction of the non-hydrogen filler, and RA _H is the contraction of the hydrogen filler.

The smaller the value of the hydrogen embrittlement index, the better the hydrogen embrittlement resistance.

The creep characteristics were evaluated by performing a creep rupture test and a creep speed test. In both tests, the test temperature was 700 ° C, and the test stress was 333 MPa and 275 MPa in the fracture test and 333 MPa in the speed test.

Table 2 shows tensile strength, shrinkage and hydrogen embrittlement index of hydrogen filler and non-hydrogen filler at 625 ° C. Also, the hydrogen embrittlement index of the inventive material P1 was negative, but in Table 2, it is expressed as 0.00 for the sake of convenience.

Fig. 1 is a graph showing the relationship between the temperatures of 625 deg. C at 625 deg. C of the inventive materials P1 and P2 (hereinafter sometimes referred to as "inventive material") and the comparative materials 1 and 2 (hereinafter collectively referred to as " The relationship between the hydrogen embrittlement index and the P content in the Ni-based alloy is shown.

It can be seen from Fig. 1 that the hydrogen embrittlement index of the inventive material is significantly smaller than that of the comparative material, and that the inventive material is very excellent in the resistance to hydrogen embrittlement at high temperatures. As shown in the hatched portion in Fig. 1, when the P content is 40 ppm or more, the hydrogen embrittlement index becomes 0.1 or less, and the hydrogen embrittlement susceptibility is reduced until the influence of hydrogen can be almost neglected. Thus, P enhances the coherence of grain boundaries, thereby suppressing excessive accumulation of hydrogen in the grain boundaries and reducing hydrogen embrittlement susceptibility. In order to improve the hydrogen embrittlement resistance by increasing the P content, Or more of the P content is required.

2 and 3 show creep rupture test results and creep rate test results, respectively. It can be seen from Fig. 2 that the breaking time of the inventive material exceeds the comparative material significantly, the breaking time at the test stress of 333 MPa is at least 10 times that of the comparative material 1, It was about 2000 hours in P2. 3, it was found that the minimum creep rate of the inventive material was at least 1/4 or less of that of the comparative material 2, and the value thereof was 1 × 10 ^-8 s ^-1 (3.6 × 10 ^-5 h ^-1 ) or less.

From the above, it is clear that the inventive material according to the present invention has excellent creep characteristics.

Although the present invention has been described based on the above embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and various changes and modifications can be made without departing from the spirit and scope of the present invention Are obvious to those skilled in the art.

The present application is based on Japanese Patent Application (Japanese Patent Application No. 2012-184966) filed on August 24, 2012, the content of which is incorporated herein by reference.

Claims (7)

And a balance of Fe and Ni in an amount of 30 to 40%, 14 to 16% of Cr, 1.2 to 1.7% of Ti, 1.1 to 1.5% of Al, 1.9 to 2.7% of Nb and 40 to 150 ppm of P, And Ni-based alloys which are inevitable impurities. The method according to claim 1,
Wherein the Ni-based alloy further contains at least one of Mg: not more than 0.01% and Zr: not more than 0.1%. 3. The method according to claim 1 or 2,
The hydrogen embritization index EI defined as EI = (RA _A -RA _H ) / RA _A , when the shrinkage in the tensile test of the hydrogen filler and the non-hydrogen filler is defined as RA _H and RA _A , respectively, Base alloy. 4. The method according to any one of claims 1 to 3,
A Ni-based alloy having a creep rupture time of 1,500 hours or more at 700 占 폚 and 333 MPa. 5. The method according to any one of claims 1 to 4,
And a minimum creep rate at 700 DEG C and 333 MPa is not more than 1 x 10 &lt; ^-8 &gt; s &lt; ^{-1 &} gt ;. 6. The method according to any one of claims 1 to 5,
Ammonium-based alloys used in ammonothermal pressure container materials. A method for producing a Ni-based alloy material as defined in any one of claims 1 to 3, wherein the Ni-base alloy is subjected to a solution treatment and subjected to aging treatment twice at a temperature of 825 to 855 占 폚 and a temperature of 710 to 740 占 폚.

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