JPS602653A - Production of precipitation hardening type nickel-base alloy - Google Patents

Abstract

PURPOSE:To obtain a titled nickel-base alloy which has various strength, ductility and toughness and is highly resistant to stress corrosion cracking and hydrogen cracking by specifying the selection of the component system for the Ni- base alloy and respective conditions for hot working, heat treatment and aging treatment. CONSTITUTION:An Ni-base alloy consisting of <=0.050% C, <=0.50% Si, <=2.0% Mn, 45-60% Ni, 18-27% Cr, <=0.40% Ti and >=1 kind of 2.5-5.5% Mo and <=11% W, <=0.30% Al, <=0.15% P, >=1 kind of 2.5-5.0% Nb and <=2.0% Ta, <=0.0050% S, <=0.030% N and the balance inevitable impurities and Fe is treated in the following way: The Ni-base alloy is subjected to hot working of >=50% reduction in area at 1,200-800 deg.C. The Ni-base alloy is then cooled at a cooling rate above air cooling after holding for 10min-5.0hr at 1,000-1,200 deg.C and is thereafter subjected to 1-2 times of an aging treatment for 1-200hr at 500- 750 deg.C, by which the titled Ni-base alloy having excellent resistance to stress corrosion cracking, etc. in environment contg. >=1 kind among H2S, CO2 and Cl<-> is obtd.

Description

Detailed Description of the Invention The present invention exhibits good stress corrosion cracking resistance and hydrogen cracking resistance in a corrosive environment, particularly in an environment containing one or more of hydrogen sulfide, carbon dioxide, and chloride ions. This invention relates to a method for producing high-strength, high-toughness nickel-based alloy materials.

Conventionally, full-bottom parts that require high strength and high corrosion resistance, such as structural materials for equipment in oil wells, chemical industries, geothermal power generation, etc., have been strengthened by (solid solution strengthening) + (cold working strengthening). In most cases, the strength of metal members with complicated or special shapes that cannot be subjected to cold working is difficult to increase using the conventional means described above.

On the other hand, a conventionally known means for increasing the strength that can be applied to members with special shapes is to add Ti and 81 or Nb to the alloy composition to increase the strength of Ni 3 (Ti, A
I> intermetallic compound (γ゛ phase) or Ni 3 Nb
This is to precipitate an intermetallic compound (γ'' phase).Already, there are Ni-based alloys such as Inconel-718 and Inconel-750 (trade name) that utilize such precipitation strengthening. Conventional alloys do not have sufficient corrosion resistance due to their low Cr and high Ti content.For example, Inconel-71
Grade 8 is a T' and γ'' precipitation-strengthened Ni-based alloy with the addition of Nb, Ti, and AI, and is mainly precipitation strengthened by the γ'' phase, but it cannot be said to have sufficient corrosion resistance because it contains a considerable amount of Ti.

By the way, materials that are used in environments containing one or more of hydrogen sulfide, carbon dioxide, and chlorine ions, such as oil wells, chemical industries, and geothermal power generation environments, have excellent strength and toughness. Corrosion resistance, that is, stress corrosion cracking resistance and hydrogen cracking resistance is required. For materials used as structural materials in such applications, it is desirable to increase the strength of materials that are relatively easy to form, such as plates or pipes, by cold working, but for materials such as valves, joints,
For items such as piping that have a special shape that cannot be cold worked, the strength must be increased by precipitation strengthening. However, according to the results of the research conducted by the present inventors, in conventional precipitation-strengthened alloys such as those described in 1, most of which are γ-precipitation-strengthened Ni-based alloys due to the addition of Ti and ^1, essentially It was found that the corrosion resistance was poor.

For example, as an alloy with good stress corrosion cracking resistance,
-203741 discloses Nh and T
Due to the composite addition of i (or AI), γ''-Ni 3 (Ti, 8l) and γ''-Ni
3 Two intermetallic compounds of Nb precipitate mainly, but Ti
Since the amount added is large, over-aging is likely to occur, and when an intermetallic compound of η-Ni3Ti is precipitated as an over-aging precipitation phase, corrosion resistance and
In particular, hydrogen cracking resistance deteriorates significantly. In order to improve this corrosion resistance, it is necessary to strictly limit the heat treatment conditions and aging treatment conditions.

Furthermore, a similar alloy described in JP-A-57-123948 is also known, but this also has poor corrosion resistance due to the addition of a large amount of Ti and even AI. Ti
As can be seen from the fact that a lower limit is set for the amount of addition of AI and Ni 3 (Ti, 'AI), that is, γ
It is intended to precipitate nine phases.

Here, the present inventors have developed a Ti-added γ” precipitation-strengthened N
i-base alloys inherently have poor corrosion resistance and lack stability; that is, Ti-added alloys in which γ'-Nt 3 Ti precipitates (the same is true for Ti and Nb composite additions).
As a result of further research, we found that the corrosion resistance of Ni-based alloys significantly deteriorated, and by selecting the composition of the Ni-based alloy and specifying the hot working, heat treatment, and aging treatment conditions, we were able to achieve various strengths, ductility, The present invention was completed based on the discovery that it is possible to obtain a material that has toughness and has excellent stress corrosion cracking resistance and hydrogen cracking resistance.

Here, the gist of the present invention is that C: 0.05
0% or less, Si: 0.50% or less, Mn: 2.
0% or less, Ni: 45-60%, Cr: 18-2
7%, Ti: 0.40% or less, Mo: 2.5
~5.5% and W: at least one type of 11% or less (however, 2.5%≦Mo+'A'A≦5.5%), 81: 6.30% or less, P: o, ots %below,
Nb 72.5-5.0% and Ta: at least one of 2.0% or less (however, 2.5%≦Nb+%T
a≦5.0%), S: o, ooso% or less, N: o, o3o% or less, the balance consisting of incidental impurities and Fe is reduced in area by 50% at 1200 to 800°C.
1000~1200"c after hot working
After holding for 5 hours from 10°C, cool at a rate faster than air cooling (however, between 9° and 500°C, cool at a cooling rate of 10°C/min or more), then at 500°C to 750°C for 1 hour to 20°C.
By performing aging treatment for 0 hours once or twice or more, γ has excellent stress corrosion cracking resistance and hydrogen cracking resistance in an environment containing one or more of hydrogen sulfide, carbon dioxide, and chlorine ions. ``This is a method for producing precipitation-strengthened nickel-based alloys.

Furthermore, in the present invention, the alloy may optionally include:
Cu: 2.0% or less and/or Co: 2.0%
It may also contain, or separately or simultaneously, the following: REM: 0.10% or less, Mg: 0.10
% or less, Ca: 0°10% or less and Y: 0.20
% or less of one type or two or more types.

That is, according to the present invention, the present invention provides a material containing one or more of hydrogen sulfide, carbon dioxide, and chloride ions, which has good stress corrosion cracking resistance and resistance in, for example, oil well, chemical industry, and geothermal power generation environments. In order to obtain high strength even when used in parts that have hydrogen cracking properties and cannot be subjected to cold working due to their special shape, such as valve bodies for oil wells, the new material has a higher Cr and Ti content than before. A γ" precipitation-strengthened Ni-based alloy that exhibits high strength and toughness with extremely good corrosion resistance by forming an alloy composition with a low Nb addition and applying it in combination with specific hot working and heat treatment. is obtained.

Therefore, according to one feature of the present invention, as a method for improving the corrosion resistance of conventional precipitation-strengthened Ni-based alloys, based on the above-mentioned knowledge, the amount of Ti added is suppressed compared to the conventional method, and the Ti phase is not (γ). ”-Ni 3 Nb, and specify the heat treatment conditions and aging conditions to obtain more effective precipitation strengthening.

The reason why the alloy composition and processing conditions are specified as described above in the present invention will be explained in more detail below.

1) Chemical composition Ni, this alloy has Ni3 in the austenite base.
The basic principle is that the intermetallic compound γ phase of Nb precipitates and strengthens with aging, and the balance of the amount of Cr and 〇 added increases the ductility and ductility of the σ, μ, P, Laves phases, etc.
Sufficient N to stabilize the austenite base so as not to form intermetallic compounds that are unfavorable for toughness and corrosion resistance.
i amount is necessary, and for that purpose Ni≧45%.

Moreover, if Ni exceeds 60%, the hydrogen cracking resistance will deteriorate significantly, so N460% is desirable, but preferably 50%
%≦Ni≦55%.

Cr improves corrosion resistance together with Mo. For this purpose, 18% or more is required, but if it exceeds 27%, hot workability decreases, and intermetallic compounds (σ, μ, P, Lave
s-phase, etc.) are more likely to be generated. Preferably Cr is 22
~27%.

MO% W, , , , , the coexistence with Cr particularly improves the pitting corrosion resistance. This effect is, for example, Mo2.5
% or more, but like Cr, adding a large amount tends to generate intermetallic compounds (σ, μ, P, Laves phases, etc.) that are unfavorable for ductility, toughness, and corrosion resistance. It is desirable to add The enemy is M
Although it exhibits the same effect as Mo, it is necessary to add twice the amount of Mo to obtain the same effect. Therefore, the required M
o amount may be replaced by at least one size. 11% saw
If added in excess of 1%, the above-mentioned intermetallic compounds are likely to be formed similarly to Mo, so it is limited to 11% or less.

Therefore, in the present invention, Mo: 2.5 to 5°5
% and W: At least one type of 11% or less (however, 2
．． 5%≦Mo+! 4W≦5.5%). Outside these ranges, corrosion resistance will not be improved sufficiently and ductility and toughness will deteriorate.

Ti, , , , If Ti exceeds 0.4%, Ni 3
Although it precipitates as Ti, it significantly deteriorates the corrosion resistance, so considering only the deoxidizing effect, the Ti content is set to 0.40% or less, preferably Ti: 0.20% or less.

Δ], , , , AI is most suitable as a deoxidizing agent for Ni-based alloys, and the deoxidizing effect improves as the amount added increases, but the effect is saturated when it exceeds 0.30%, so Al
The content should be 70.30% or less, preferably 0.15% or less.

Nb, Ta,..., T''-Ni3(Nb,
Ta) contributes to an increase in precipitation strength. The effect becomes remarkable when Nb+%Ta is 2.5% or more, but when 5.0%
%, hot workability decreases, and ductility, toughness,
Intermetallic compounds (f・μ・P) that are unfavorable for corrosion resistance
% Laves phase, etc.) are easily generated. however,
Nb: 72.5% to 5.0%, Ta: 2.0% or less. Outside these ranges, there is no effect on increasing strength, but rather the ductility and toughness deteriorate. In the case of Ta, the effect of adding it is approximately 1/2 that of Nb. Therefore, in the present invention, Nb: 2.5 to 5.0% and Ta: 2.0%
% or less of at least one of the following: 2.5%≦Nb”ATa≦5
．． Add within the range of 0%.

c,,,00. Precipitation strengthening is hindered, and 0.0
When it exceeds 50%, the amount of inclusions such as NbC and Tic increases, resulting in deterioration of ductility, toughness, and corrosion resistance. Preferably C≦0.0
20% T: Yes, but ductility and toughness are further improved at 50,010% C.

Sis Mn, Si, Mn is added as a deoxidizing agent and desulfurizing agent, but if St exceeds 0.50%, intermetallic compounds such as σ phase, which are unfavorable for ductility and toughness, are formed. Si: 0.5% or less to make the process easier. Considering weldability, 2.10% SiS is preferable. Furthermore, regarding Mn, it is similarly desirable that MnS be 2.0%, but preferably MnS2.80%.

p, s, 0. ,,p,s reduce hot workability due to grain boundary segregation and also deteriorate corrosion resistance, so P≦
0.015%, S≦0.0050%, preferably S≦
It shall be 0.0010%.

Since N increases the amount of inclusions and causes anisotropy in material properties, N≦0.030%, preferably N≦0.010%.

An appropriate amount of Fe' is required to promote precipitation strengthening depending on the balance with the amount of Ni added, and the remainder of the alloy composition is Fe, excluding incidental impurities. Preferably 3
．． 0%≦Fe≦25%.

Cu, Co,... is effective in improving corrosion resistance, but the effect is saturated when it exceeds 2.0%, so Cu, Go≦2
゜0%.

Hot workability is improved by adding small amounts of REM, Mg, Ca, Y, 0.10% and 0.0%, respectively.
If the upper limits of 10%, 0.10% and 0.20% are exceeded, on the contrary, low melting point compounds are likely to be produced, resulting in a decrease in processability.

In addition, B % Sns Zn, Pb, etc. do not affect the properties of the alloy of the present invention in @ amount, so up to 0.10% of each is allowed as impurities, but if the upper limit is exceeded, workability or corrosion resistance will deteriorate. to degrade.

2) Hot processing When Nb is added as in the present invention, low melting point compounds tend to be generated at grain boundaries during solidification, and it is necessary to limit the heating temperature and processing temperature range during hot processing. be. Grain boundary embrittlement is observed when the starting temperature of hot working exceeds 1200"C. On the other hand, when the finishing temperature exceeds 800"C
If it is less than that, it will be difficult to process. In the present invention, the temperature range is 1200 to 800°C, preferably 115°C.
Hot working is performed at 0 to 850°C.

Furthermore, Nb, Mo, etc. tend to cause macro segregation during solidification, and if such segregation remains in products, it becomes a factor in deterioration of toughness and corrosion resistance in thick-walled materials.

For this reason, the degree of hot working from the ingot to the product is set to 50% or more in area reduction rate to prevent macro segregation of Nb, Mo, etc.

2 3) Complete solution treatment is necessary to effectively precipitate γ''-Ni 3 Nb by heat treatment. Therefore, in the present invention, prior to aging, heat treatment is performed at 1000°C to 1200°C,
Preferably, the temperature is maintained at 1050 to 1150°C for 10 minutes to 5.0 hours, and then cooled at a cooling rate higher than air cooling. Especially 900℃
Since the brittle phase is likely to precipitate between 500° C. and 500° C., precipitation is suppressed by cooling at a cooling rate of 10° C./min or more.

4) Aging treatment The alloy obtained by the present invention has a γ”-
Since Ni 3 Nb is uniformly dispersed and precipitated within the grains, high strength, good ductility, toughness, and corrosion resistance are obtained. but,
If the aging temperature is less than 500°C and less than 1.0 hours, sufficient strength will not be obtained, whereas if the aging temperature exceeds 750°C, over-aging will occur, resulting in coarsening of γ''-Ni 3 Nb or δ-
Strength and toughness deteriorate due to the formation of Ni3Nb and intermetallic compounds such as σ phase. The maximum statute of limitations is 2
00 hours is sufficient.

In order to obtain stable strength, ductility, toughness, and corrosion resistance, it is desirable that only γ”-Ni 3 Nb be finely and uniformly dispersed and precipitated in the austenite matrix, but for this purpose aging treatment at 600°C to 700°C is necessary. is preferred.

3 Thus, according to the method of the present invention, the mechanical properties are 0.
．． 2% proof stress ≧63k [rf/mm (preferably ≧
77 kg f/,%), elongation ≧20%, aperture 130%
and impact value≧5kgf-m/cJ (preferably≧
10 kgf-m /cJ) and excellent corrosion resistance, that is, resistance to SCC and hydrogen embrittlement. The alloy according to the invention comprises Ni
3 High strength can be obtained by precipitation strengthening of the γ” phase, which is an intermetallic compound of Nb, so even products with special shapes such as oil country tubular valve bodies that cannot be strengthened by cold working etc. can be used in good condition. It is possible to manufacture products with excellent strength, toughness, and corrosion resistance.

Next, the present invention will be further explained based on examples. In this specification, "%" means "% by weight" unless otherwise specified.

Examples For each alloy having the chemical composition shown in Table 1 below,
Precipitation-strengthened nickel-based alloys were produced under the same hot working conditions, heat treatment conditions, and aging treatment conditions shown in Table 2.

The mechanical properties and corrosion resistance test results of the obtained alloy are also summarized in Table 2.

4 Tensile test with a diameter of 3.5 mm and a gauge distance of 20.0 mm.
This was done using a test rod. The impact value is based on the Charpy impact test, and is 5.0 m x 10 mm x
A test piece with a size of 55 mm and a 2.0 mm glue strip was used. The test temperature was 0°C.

Corrosion resistance for SCC is 25% NaC] -0.5%
CCH3C00H-15at l (2S5-1Oat
250 °C using a solution of Co2 (pH = 2)
I went there. Regarding hydrogen embrittlement, under NACE conditions (5%NaC+-0,5%CH3C00H-1atm+
The test was carried out at 25°C using a carbon steel coupling (RO, 25U) and a notched test piece.

In Table 2, "0" indicates the case where there was no cracking, and "X" indicates the case where the cracking occurred.

Comparative examples are Nos. 29 to 34, which are within the composition range of the alloy used in the method of the present invention, but outside the hot working, heat treatment, and aging treatment conditions, and the processing conditions are within the range. However, those with different alloy components are still 35-4
4. In the comparative examples, one or more of strength, ductility, toughness, and corrosion resistance are not good.

Nos. 45 to 56 are shown for comparison with the conventional precipitation-strengthened type 5 alloys with addition of Ti and AI obtained by the method of the present invention. Many of these conventional alloys have good strength, but their corrosion resistance has deteriorated due to their nature, and in order to improve such corrosion resistance, strength must be sacrificed. I can't get it.

The accompanying drawings are Nos. 1 to 14 in Tables 1 and 2.
The results of high-temperature torsion tests for alloys Nos. and Nos. 29-34 are summarized in a graph. In the figure, the white circle represents the twist value, and the white circle corner represents the torque at that time. It can be seen that when the test temperature exceeds 1200°C, the twist value decreases significantly. This is because in the case of the present invention, since a relatively large amount of Nb is added, low melting point compounds are generated at grain boundaries when processed at a high temperature exceeding 1200°C.

In this way, by limiting the range of alloy components and the conditions of hot working, heat treatment, and aging treatment as in the present invention, a high-strength, high-toughness material with outstanding corrosion resistance can be obtained.

6

[Brief explanation of drawings]

The accompanying drawing is a graph showing the high temperature torsion test results of the alloy obtained by the method of the present invention. I Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent Attorney Akira Hirose - Test Temperature ('C) 3 Hand-based Sales Authorization (Spontaneous) January 12, 1980 Kazuo Wakasugi, Commissioner of the Patent Office 1, Case Indication of 1982 Patent Application No. 109422 2 Name of invention Method for producing precipitation-strengthened nickel-based alloy 3 Relationship to the case of the person making the amendment Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Name (211) Sumitomo Metal Industries, Ltd. 4, Detailed Explanation of the Invention in the Agent's Specification, tltl 16, Contents of Amendment As shown in the appendix, the description in the following portion of the specification of the contents of the amendment is corrected as follows. X row Tamakami ■■ placement 酊” trial 9 尤 3 5-6 N+3 (Ti, AI) Ni3 (Ti,
A1) mainly composed of 6 Ni 3 Nh and 4 21 to 22 mainly composed of Ni 3 Nb, as well as A1 -Deletion-51 and A
I 2 That is, r° phase 7 14 Not γ° phase but 14 5 sec Stress corrosion cracking Hydrogen embrittlement Hydrogen cracking 15 6 3CC stress corrosion cracking test 8 Hydrogen embrittlement Hydrogen cracking test 20 WISCC stress corrosion cracking in "Corrosion resistance" in Table 2 Hydrogen embrittlement Hydrogen cracking resistance 21 5CC Stress corrosion cracking resistance Hydrogen embrittlement Hydrogen cracking resistance 22 3CC Stress corrosion cracking resistance W J〒4>Miscellaneous 11 nLu147) Placement 22 No. 2
"Corrosion resistance" column in the table Hydrogen embrittlement Hydrogen cracking resistance or higher 309-

Claims (1)

[Claims] (]) C40,050% or less, St: 0.50%
Below, Mn: 2.0% or less, Ni: 45-6
0%, Cr: 18-27%, Ti: 0.40
% or less, Mo: 2.5-5.5% and W: 11%
At least one of the following (however, 2.5%≦Mo+!
4W≦5.5%), ^1 F 0.30% or less, P: o, ots% or less, Nb: 2.5-5.0% and Ta: 2.0
% or less (however, 2.5%≦Nb+%
Ta≦5.0%), S: 0.0050% or less, N: o, o3o% or less, the balance is incidental impurities and Fe.
After the above hot working, 1 at 1000~1200℃
After holding for 0 minutes to 5 hours, cool at a cooling rate higher than air cooling (however, between 900 and 500°C, cool at a cooling rate of 10°C/min or higher), then at 500 to 750°C for 1 hour to 2 hours.
γ that has excellent stress corrosion cracking resistance and hydrogen cracking resistance in an environment containing one or more of hydrogen sulfide, carbon dioxide, and chloride ions, which is obtained by performing aging treatment for 00 hours once or twice or more. ``A method for producing a precipitation-strengthened nickel-based alloy.'' (2) Claim (1), wherein the alloy further contains Cu: 2.0% or less and/or Co: 2.0% or less. The method described. (3) The alloy further comprises one or two of REM: o, to% or less, Mg: 0.10% or less, Ca: 0.10% or less, and Y: 0.20% or less. A method according to claim (1) or (2) comprising the above.