JPH07331369A - Chronium-nickel-aluminum alloy for ultrahigh temperature use - Google Patents

Abstract

PURPOSE:To obtain a Cr-Ni-Al alloy for ultrahigh temp. use, increased in adhesion of oxide scale and excellent in high temp. oxidation resistance and workability by specifying a composition consisting of C, Si, Mn, S, Al, Cr, and Ni. CONSTITUTION:This alloy has a composition consisting of, by weight, <=0.1% C, <=1.0% Si, 0.2-3.0% Mn, <=0.01% S, 10-15% Al, 18-40% Cr, and the balance Ni with inevitable impurities and further containing, if necessary, one or more kinds among 0.1-20% Fe, 0.1-5% Co, and 0.1-5% Cu, further 0.1-5% Ti qnd/or 0.1-5% V, further 1-10% W and/or 0.5-5% Mo, further <=0.25% of one or more kinds among 0.01-0.25% Y, 0.01-0.25% La, and 0.01-0.25% Ce, and further 0.001-0.02% Mg. This alloy has superior adhesion of an oxide film composed of Al2O3 and has excellent oxidation resistance even at an ultrahigh temp. of about 1000 deg.C or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Cr-Ni-Al alloy which is excellent in oxidation resistance, particularly in adhesion to oxide scales, has good workability, and is widely applicable for ultrahigh temperatures.

[0002]

2. Description of the Related Art Heat-resistant steel is an alloy steel that exhibits appropriate strength, oxidation and high-temperature corrosion resistance even when used in various high-temperature environments, and is classified into many steel types depending on various conditions such as temperature and atmosphere. ing. All of these heat-resistant steels have a high Cr content.
The oxidation resistance and high temperature corrosion resistance are improved by forming a protective scale of Cr ₂ O ₃ on the surface of the surface.

However, when these heat-resistant steels are used in an environment of ultra-high temperature exceeding 1000 ° C., the protective property of the scale composed of Cr ₂ O ₃ (hereinafter referred to as “oxide film”) is gradually lost. However, high Al steels have been applied, which form an oxide film consisting of Al ₂ O _{3 with} superior protection at ultra-high temperatures on the surface. For example, SUH2 for home appliances kitchen appliances
Both 1 (19Cr-3Al) and 20Cr-5Al steel for automobile metal carriers are heat-resistant steels in which an oxide film made of Al ₂ O ₃ is used as a protective oxide film to achieve high Al. The oxidation resistance is improved by increasing the Al content, but the workability is significantly reduced due to the formation of the oxide film.

Therefore, as an attempt to prevent such deterioration in workability, Japanese Patent Laid-Open No. 1-108316 discloses C: 0.
03% or less (hereinafter, "%" means "% by weight" unless otherwise specified), C
r: 16.0 to 26.0%, Al: 2.0 to 6.0%, the balance of Fe and unavoidable impurities Fe-Cr-Al alloy is hot-rolled to finish plate thickness: 3.5 mm or less, and then by quenching, A method for producing an Fe-Cr-Al-based alloy material having excellent toughness is disclosed in JP-A-1-47816. C: 0.2% or less, Si: 2.0% or less, Mn: 2.0% or less, Ni: 15 ~ 35%,
Cr: 12 to 25%, Al: 2.0% or more (preferably 6% or less), the balance Fe and unavoidable impurities are heated to 1150 ℃ or more, and 900 ℃
Thus, there have been proposed methods for finishing hot rolling and immediately followed by rapid cooling to 600 ° C or less.

As can be seen from these proposals, in a forged alloy, it is possible to add Al up to 5 to 6% at most, and if the Al addition amount is further increased, for example, a high alloy used for gas turbines can be obtained. It can only be manufactured as a cast alloy, such as an Al-Ni based alloy.

[0006] In recent years, it has been required to further improve the oxidation resistance of products whose operating environment represented by alloy foils for automobile metal carriers is more severe. From the viewpoint, it is impossible to raise the Al content further.

Therefore, for example, in Japanese Patent Laid-Open No. 1-11946, C: 0.03% or less, Si: 1.0% or less, Cr: 13-27.
%, Al: 3.5-8%, Zr: C content of 8 times or more
Fe-Cr-Al based alloys having excellent oxidation resistance have been proposed, which contain 0.30% or less, balance Fe and unavoidable impurities, and further contain rare earth elements other than Ce: 0.05% or more and 0.20% or less.
This Fe-Cr-Al alloy is mainly intended to be applied to a metal carrier used for a catalyst for purifying automobile exhaust gas, and an appropriate amount of a rare earth element other than Ce which deteriorates hot workability and oxidation resistance. By adding it, the adhesion of the oxide film made of Al ₂ O ₃ is improved, and the oxidation resistance is further assisted.

Further, in Japanese Patent Laid-Open No. 194942/1989, high Al content which is a metal carrier material used for a catalyst for purifying automobile exhaust gas is disclosed.
In order to further improve the oxidation resistance by increasing the Al surface of the contained stainless steel foil, in the cooling process of the stainless steel foil formed by rapid solidification, press Al or Al alloy foil on at least one surface A metal carrier material having a different layer has been proposed. However, since the metal carrier material according to this proposal increases the number of manufacturing steps and the manufacturing cost, it is desired to improve the oxidation resistance by increasing the Al content of the base material itself.

On the other hand, an attempt to improve the workability of a high Al steel having an Al content of 15 to 26% has been made at the laboratory level, but the Cr--Ni--Al alloy and the Fe--Ni--Al alloy have been used. Alloy, Co-
Ni-Al alloys and Cu-Ni-Al alloys are used in the (β + γ) two-phase region (Metallugical Transactions A vo
l.22A Feb (1991) P441-446).

[0010]

Generally, high Al materials are excellent in oxidation resistance, so at first glance, such Cr-Ni-
It is also considered that the oxidation resistance of the Al-based (β + γ) two-phase alloy is also improved by increasing the Al content. However, the reason why the oxidation resistance is excellent due to the high Al content is that a stable oxide film made of Al ₂ O ₃ is formed on the surface, and the amount of Al necessary for forming this oxide film is Fe- There is a great difference between binary systems such as Al or Ni-Al and ternary systems such as Cr-Ni-Al.
Further, the oxidation resistance is greatly influenced by the amounts of other trace additive elements. Therefore, in the development of a Cr-Ni-Al (β + γ) two-phase alloy, it is necessary to perform both component design that accurately reflects the operating environment and determination of its oxidation resistance.

Further, the oxide film formed of Al ₂ O ₃ is Cr ₂ O ₃
The thermal expansion coefficient is smaller than that of the base material, as in the case of the oxide film made of, so that a large stress occurs due to the difference in the thermal expansion coefficient between the base material and the oxide film peels off. It may deteriorate. Therefore, the current situation is that a Cr-Ni-Al (β + γ) two-phase alloy has not been put to practical use.

The object of the present invention is to improve the workability.
Since the Cr-Ni-Al (β + γ) two-phase alloy is applied to high temperature members, it has excellent adhesion to the oxide film made of Al ₂ O ₃ and has excellent oxidation resistance even when used at ultrahigh temperatures of 1000 ° C or higher. And is widely applicable as an alloy for ultra-high temperature
It is to provide a (β + γ) two-phase alloy.

[0013]

Means for Solving the Problems The inventors of the present invention have made various studies to solve the above problems, and have obtained the knowledge of the contents listed below to complete the present invention. It is necessary to add 10% or more Al in order to secure sufficient oxidation resistance even at a use temperature of 1000 ° C. or higher in a Cr-Ni-Al (β + γ) two-phase alloy system.

In a harsh environment where heating and cooling are repeated, abnormal oxidation occurs due to peeling of the oxide film, but by adding an appropriate amount of Mn, Al ₂ O ₃ having excellent adhesion can be obtained.
An oxide film composed of is formed, and abnormal oxidation does not occur even under the above-mentioned environment.

[0015] This is because, Mn, in the initial stage of the oxidation to affinity greater the O ₂ promotes the generation of the oxide film consisting of a stable Al ₂ O ₃ on the surface as a getter material for O _2, the The Mn oxide generated in the step forms a solid solution into the oxide film after it is formed to enhance the plastic deformability of the oxide film, thereby increasing the stress between the base metal and the oxide film made of Al ₂ O ₃ , that is, repeating The stress caused by the difference in the coefficient of thermal expansion between the oxide film and the base metal, which is considered as one of the causes of the peeling of the oxide film under the environment, is relaxed and the adhesion of the oxide film made of Al ₂ O ₃ is improved. This is because

Further, the concentration of S at the oxide film / metal interface is also considered to be one of the causes of impairing the adhesion, but Mn also has a function of fixing S as MnS, so that Mn is 0.2 to
It was found that the addition of 3.0 wt% can dramatically improve the adhesion of the Al ₂ O ₃ coating by the synergistic effect of stress relaxation and S fixation without impairing other properties of the Cr-Ni-Al alloy of the present invention. .

The gist of the present invention is as follows.
C: 0.1% or less, Si: 1.0% or less, Mn: 0.2% or more 3.0
% Or less, S: 0.01% or less, Al: 10% or more and 15% or less, Cr:
It is a Cr-Ni-Al alloy for ultrahigh temperatures, which is excellent in the adhesion of an oxide film, characterized by being an alloy consisting of 18% or more and 40% or less, the balance being Ni and unavoidable impurities.

In the present invention, in order to stabilize the γ phase and improve workability, Fe: 0.1% or more and 20% or less, Co: 0.1% or more and 5% or less, and Cu: 0.1% or more 5
It is desirable to contain one or two or more selected from the group consisting of% or less.

In the present invention, in order to precipitate the γ'phase (Ni ₃ Al) to enhance the high temperature strength, Ti: 0.1% or more and 5% or less, and V: 0.1% or more and 5% or less. It is desirable to contain one or two selected from the following.

In the present invention, in order to strengthen the matrix and increase the high temperature strength, 1 selected from the group consisting of W: 1% or more and 10% or less, and Mo: 0.5% or more and 5% or less.
It is desirable to contain one or two species.

In the present invention, the formation of an internal oxide
In order to improve the adhesion of the oxide film made of Al ₂ O ₃ ,
Furthermore, Y: 0.01% to 0.25%, La: 0.01% to 0.
It is desirable to contain 25% or less and Ce: 0.01% or more and 0.25% or less in total, and 0.25% or less in total of one kind or two or more kinds selected from the group consisting of.

In the present invention, in order to fix S and improve the hot workability and the adhesion of the oxide film, it is preferable that the content of Mg is 0.001% or more and 0.02% or less.

[0023]

The operation of the present invention will be described in detail below. First, the reason for limiting the composition of the Fe—Ni—Al alloy for ultrahigh temperature according to the present invention as described above will be explained.

C: 0.1% or less C is an element that is unavoidably contained in steel.
If the content exceeds 1%, ductility and toughness decrease. Therefore, in the present invention, the C content is limited to 0.1% or less.

Si: 1.0% or less In the case of the ultra-high temperature Fe-Ni-Al alloy according to the present invention, Si is 1.
If the content exceeds 0%, workability deteriorates. Therefore, in the present invention, the Si content is limited to 1.0% or less even when Si is used as a deoxidizing agent.

Mn: 0.2% or more and 3.0% or less In the Cr-Ni-Al alloy for ultrahigh temperature according to the present invention, when the Mn content is 0.2% or more, the adhesion of the oxide film made of Al ₂ O _{3 can} be improved. It is effective and also stabilizes the (β + γ) 2 phase structure to improve workability, but if it exceeds 3.0%, the oxidation resistance is deteriorated. Therefore, in the present invention, the Mn content is 0.
Limited to 2% or more and 3.0% or less. Preferably 0.7-2.5
%, More preferably 0.7 to 2.0%.

S: 0.01% or less When S is contained in excess of 0.01%, it segregates at the interface between the oxide film and the base material and impairs the adhesion of the oxide film. Therefore, in the present invention, the S content is limited to 0.01% or less.

Al: 10% or more and 15% or less Al is added in an amount of 10% or more to form an oxide film made of Al ₂ O ₃ to enhance oxidation resistance, and further, together with Ni and Fe, (β + γ) 2 Maintains the phase structure and improves workability. However, if it exceeds 15%, the workability deteriorates. Therefore,
In the present invention, the amount of Al added is limited to 10% or more and 15% or less. It is preferably 10 to 14%.

Cr: 18% or more and 40% or less Cr stabilizes the (β + γ) 2 phase structure and develops oxidation resistance together with Al, so 18% or more is added. Stability is lost and workability deteriorates. Therefore, in the present invention, the Cr addition amount is limited to 18% or more and 40% or less.

Compositions other than the above are Ni and inevitable impurities. Although the Ni content does not have to be 50% or more, it is the highest content among the elements constituting the Cr-Ni-Al alloy for ultrahigh temperature according to the present invention. It is preferably 18 to 35%, more preferably 20 to 33%.

The Cr-Ni-Al alloy for ultrahigh temperature according to the present invention may further contain the elements listed below as optional additional elements. Hereinafter, these optional additional elements will be described.

Fe: 0.1% or more and 20% or less, Co: 0.1% or more
5% or less and Cu: 0.1% or more and 5% or less
Any one element or two or more elements selected from the above stabilizes the γ phase and improves the workability. Therefore, in the Cr-Ni-Al alloy for ultrahigh temperature according to the present invention, the content is 0.1%.
If added more than 20% in the case of Fe and more than 5% in the case of Co or Cu, the phase stability is impaired and the workability deteriorates. Therefore, when adding one or more of Fe, Co and Cu, Fe: 0.1% to 20%, Co: 0.1%
5% or less and Cu: 0.1% or more and 5% or less, respectively.

Ti: 0.1% to 5%, and V: 0.1
% Or more and 5% or less selected from the group consisting of one or two of these elements, if both are contained in an amount of 0.1% or more, the high temperature strength is enhanced due to the precipitation of the γ'phase. The chemical conversion decreases. Therefore, when adding Ti and / or V, Ti: 0.1% or more and 5% or less and V: 0.1% or more and 5% or less are limited.

W: 1% or more and 10% or less, and Mo: 0.5%
One or two of these elements selected from the group consisting of 5% or less are strengthened with a proper amount to enhance the high temperature strength, but if added excessively, the phase stability is impaired and the workability is deteriorated. . Therefore, when W and / or Mo is added, W is limited to 1% or more and 10% or less and Mo: 0.5% or more and 5% or less.

Y: 0.01% or more and 0.25% or less, La: 0.01% or less
Upper 0.25% or less and Ce: 0.01% or more and 0.25% or less
0.25% or less in total of 1 or 2 or more selected from the group
When these elements are contained in appropriate amounts, the adhesion of the oxide film made of Al ₂ O ₃ is improved by the formation of internal oxides. The effect of improving sex is saturated. Therefore, when one or more of Y, La and Ce are added, Y: 0.01% or more and 0.25% or less, La: 0.01% or more and 0.
25% or less, Ce: 0.01% or more and 0.25% or less, in total
Limited to 0.25% or less.

Mg: 0.001% or more and 0.02% or less By containing 0.001% or more of Mg, it is possible to fix S and improve the hot workability and the adhesion of the oxide film made of Al ₂ O _3. . However, if over 0.02% is added, a low melting point compound with Ni is formed and the workability deteriorates. Therefore, when adding Mg, the content is limited to 0.001% or more and 0.02% or less.

The Cr-Ni-Al alloy for ultrahigh temperature according to the present invention having the above composition is excellent in oxidation resistance, particularly in the adhesiveness of the oxide film made of Al ₂ O _3, and has good workability. Widely applicable as a forged alloy for ultra-high temperature
(β + γ) Two-phase ultrahigh temperature Cr-Ni-Al alloy. Further, the present invention will be described in detail with reference to examples, but this is an example of the present invention and the present invention is not limited thereto.

[0038]

[Example] 17 kg of various alloys having the compositions shown in Tables 1 and 2
A slab having a thickness of 25 mm and a width of 100 mm was formed by vacuum melting and hot forging in a temperature range of 1200 to 1300 ° C., and then hot rolling was performed at a finishing temperature of 1200 ° C. to a plate thickness of 3 mm. After that, cold rolling and annealing (1200 ° C. × 5 minutes) were performed multiple times to manufacture a metal foil having a thickness of 0.5 mm.

[0039]

[Table 1]

[0040]

[Table 2]

These metal foils are heated in the atmosphere heated to 1200 ° C. for 30 minutes and then cooled at room temperature for 30 minutes.
Repeated oxidation test was conducted by repeating this cycle for 200 cycles. Tables 1 and 2 also show the evaluation results of hot workability and the results of repeated oxidation tests.

The hot workability was evaluated by visually observing the outer surface of the slab after hot forging, and ⊚ when there was no crack, and ◯ when slight crack occurred but hot rolling was possible. When hot rolling was not possible due to significant cracking, it was evaluated as x.

The results of the repeated oxidation test showed the increase in oxidation calculated from the change in weight before and after the test, and the oxidation resistance was evaluated. That is, if the adhesion of the oxide film made of Al ₂ O ₃ is insufficient, the oxide film repeats peeling during cooling and the weight decreases, but if the adhesion is excellent, it corresponds to the formation of an oxide film made of Al ₂ O _3. Shows a slight weight gain.

Further, the high temperature strength test was carried out by a high temperature tensile test at 1150 ° C. Table 1 and Table 2 show the results of these tests together. From Tables 1 and 2, the inventive examples (Sample No. 1 to Sample No. 54) have excellent hot workability and show only a slight increase in oxidation amount, and an oxide film formed of Al ₂ O ₃ on the surface. It can be seen that has excellent adhesiveness and has excellent oxidation resistance.

Particularly, sample No. 2, sample No. 4, sample No. 7, sample No. 8, sample No. 13, sample No. 16, sample No. 17, sample N
o.19, sample No. 20, sample No. 26 to sample No. 31, sample No. 35 to sample No. 38, and sample No. 40, 41, 45
~ 47, 50, 51, 53 are Fe: 0.1% or more and 20% or less, Co: 0.1% or more and 5% or less, and Cu: 0.1% or more 5 respectively.
%, The γ phase is stabilized and the workability can be improved because one or more selected from the group consisting of 10% or less is contained.

Sample No. 9, Sample No. 10, Sample No. 16, Sample
No.17, Sample No.20 to Sample No.24, Sample No.26 to Sample No.30, and further Sample No.32 to Sample No.40,
42, 47, 48, 50, 52, 53 each contain one or two selected from the group consisting of Ti: 0.1% or more and 5% or less, and V: 0.1% or more and 5% or less, It was possible to increase the high temperature strength by precipitating the γ'phase.

Sample No. 11, Sample No. 12, Sample No. 18, Sample No. 21, Sample No. 23, Sample No. 25, Sample No. 27, Sample N
o.29, sample No. 31 to sample No. 35, and further sample No.
37 to Sample Nos. 40, 43, 45, 48, 49, 51 to 53 are W: 1% to 10% and Mo: 0.5% to 5 respectively.
Since it contains one or two selected from the group consisting of 10% or less, it was possible to strengthen the base and increase the high temperature strength.

Sample No. 13 to Sample No. 15, Sample No. 19
, Sample No.22, Sample No.24, Sample No.25, Sample No.28
, Sample No.30, Sample No.31, Sample No.33, Sample No.34
, And Sample No. 36 to Sample No. 40, 44, 46, 49
To 53 are Y: 0.01% or more and 0.25% or less, La: 0.
0.1% or more and 0.25% or less, and Ce: 0.01% or more and 0.25% or less.
Since it contains 25% or less, the formation of internal oxides causes Al ₂ O ₃
It was possible to improve the adhesion of the oxide film made of.

Sample No. 16, Sample No. 22 and Sample No. 3
Since Nos. 5 and 41 to 54 each contained Mg: 0.001% or more and 0.02% or less, S could be fixed and the hot workability and the adhesion of the oxide film could be improved. On the other hand, in sample No. 55, the Al content was below the lower limit of the range of the present invention, and the oxide film was not stable and was peeled off.

In sample No. 56, the Mn content exceeded the upper limit of the range of the present invention, so the hot workability was deteriorated. sample
In No. 57, the Al content was above the upper limit of the range of the present invention, so the hot workability was deteriorated.

In sample No. 58, the Al content was above the upper limit of the range of the present invention, so the hot workability was deteriorated. sample
In No. 59, the S content exceeded the upper limit of the range of the present invention, so the hot workability was deteriorated.

[0052]

As described in detail above, according to the present invention, a Cr-Ni-Al alloy excellent in workability and high temperature oxidation resistance can be provided and can be widely applied as a member for high temperature environment. In particular, the oxide film made of Al ₂ O ₃ has excellent adhesion and is suitable for use in a severe environment where heating and cooling are repeated.

Claims (6)

[Claims] 1. By weight%, C: 0.1% or less, Si: 1.0%
Below, Mn: 0.2-3.0%, S: 0.01% or less, Al: 10-15
%, Cr: 18-40%, balance Ni and unavoidable impurities, Cr-Ni-Al alloy for super high temperature with excellent scale adhesion. 2. Further, Fe: 0.1 to 20% by weight, C
The Cr-Ni-Al alloy for ultrahigh temperatures according to claim 1, containing one or more selected from the group consisting of o: 0.1 to 5% and Cu: 0.1 to 5%. 3. The ultrahigh temperature product according to claim 1 or 2, further comprising one or two selected from the group consisting of Ti: 0.1 to 5% and V: 0.1 to 5% by weight. Cr-Ni
-Al alloy. 4. Further, one or two selected from the group consisting of W: 1 to 10% and Mo: 0.5 to 5% by weight.
The Cr-Ni-Al alloy for ultra-high temperature according to any one of claims 1 to 3, further comprising a seed. 5. Further, in% by weight, Y: 0.01 to 0.25%,
The ultrahigh temperature according to any one of claims 1 to 4, containing one or more selected from the group consisting of La: 0.01 to 0.25% and Ce: 0.01 to 0.25% in total of 0.25% or less. Cr-Ni-Al alloy for use. 6. Further, in% by weight, Mg: 0.001 to 0.02%
A Cr-Ni-Al alloy for ultrahigh temperatures according to any one of claims 1 to 5, further comprising: