JPH0711405A - Production of ni-base alloy having intergranular fracture resistance - Google Patents

Abstract

PURPOSE:To produce an Ni-base alloy excellent in intergranular fracture resis tance under a sour gas environment by subjecting an alloy, having a specific composition consisting of Cr, W, Nb, Fe, and Ni, to specified heat treatment and plastic working, respectively, and precipitating a WC type carbide. CONSTITUTION:An alloy, having a composition consisting of, by weight, 14.0-20.0% Cr, 10.0-25.0% W, 4.0-7.0% Nb, 2.0-10.0% Fe, and 50.0-60.0% Ni, is heated and held at 1000-1300 deg.C for 1-200hr. This alloy is subjected to plastic working at 900-1300 deg.C at =10% reduction of area once or more and then held at 900-1250 deg.C for 1min-100hr. Subsequently, the alloy is cooled down to successive aging temp. (600-800 deg.C) at a cooling velocity between furnace cooling and air cooling velocities and held at 600-800 deg.C for 1-200hr to undergo aging treatment for alloy. By this method, a WC type carbide of <=40mum can be precipitated in the grain boundary of the alloy, and the highly corrosion resistant Ni-base alloy for oil well member, having high strength and excellent in stress corrosion cracking resistance and hydrogen cracking resistance in a sour gas environment containing S as simple substance, can be obtained.

Description

Detailed Description of the Invention

[0001]

The present invention relates to sour gas (H ₂ S-CO ₂
-Cl ^-) environment, used in particular sulfur (S) in an environment where is mixed as a single, good stress corrosion cracking resistance and having a hydrogen cracking resistance, oil well member (in particular, wellhead, anti bottom member) The present invention relates to a method for producing a Ni-based alloy having high corrosion resistance.

[0002]

2. Description of the Related Art In recent years, there has been a demand for deeper oil wells and wells under sour gas environments, and Ni-based alloys having high strength and high corrosion resistance have been applied to such applications. Since the corrosion resistance performance of these Ni-based alloys is generally improved especially by the contents of Cr, Mo, W, etc., the alloy component system suitable for the target corrosive environment is selected in consideration of them.

[0003] For further strength, 0.2% proof stress (RT) at 77kgf / mm ² or more, or often 91kgf / mm ² or more high strength is required. Therefore, tubular members such as tubing, casing, and liner are strengthened by cold working against these alloy component systems, while at the same time, they have a special shape or thick mouth hole, bottom part that is difficult to cold work. For materials, etc., high strength is achieved by utilizing precipitation hardening of intermetallic compounds such as γ'or γ ".

[0004] In the recent oil well development, traditional sour gas _{(H 2 S-CO 2 -Cl} -) not only to further sulfur
It is strongly desired to develop a material having good stress corrosion cracking resistance and hydrogen cracking resistance even in an environment in which (S) is mixed as a simple substance, and several new corrosion resistant materials have been proposed (for example, JP-A-63-137133).

However, the demand for deeper wells has further advanced, and there has been an increasing need for a material capable of stably obtaining a high strength of 91 kgf / mm ² or more at a 0.2% proof stress (room temperature). In addition to the conventional corrosion resistance test by long-term immersion,
With the introduction of a corrosion test in which a tensile test is performed at a constant strain rate in a corrosive solution, a new demand has emerged for a material that satisfies not only static corrosion resistance but also dynamic performance at the same time.

However, the conventional alloys cannot always stably obtain the performances satisfying both of them, and as a typical characteristic thereof, particularly in the case of a high-strength material, intergranular fracture occurs and environmental embrittlement occurs.

[0007]

[SUMMARY OF THE INVENTION The present invention, a corrosive environment, in particular sour gas _{(H 2 S-CO 2 -Cl} -) even in an environment where any sulfur (S) is mixed as a single in the environment, high strength
(0.2% proof stress (room temperature)> 91 kgf / mm ² ), and good resistance to stress corrosion cracking and hydrogen cracking
An object of the present invention is to provide a method for producing a highly corrosion-resistant Ni-based alloy used for (particularly, anti-mouth and anti-bottom members).

[0008]

DISCLOSURE OF THE INVENTION As a result of a detailed study of the correspondence between the corrosion resistance performance in such a corrosive environment, the alloy component system, and the microstructure, the inventors of the present invention have found that in the case of a high strength material, Corrosion is intergranular destruction type,
This grain boundary fracture is mainly composed of M ₆ C (M: Mo, but some Cr, Fe
It was clarified that the intergranular precipitation of () type carbide was involved.

That is, the grain boundary precipitation of M ₆ C type carbide deteriorates the corrosion resistance performance of the Ni-based alloy in the environment by the following two points: (1) M ₆ C type carbide has a lower corrosion resistance than that in the alloy matrix. A lot of Mo
As a result, the Mo concentration depletion region is formed around the carbide due to diffusion. The portion having a low Mo concentration has less corrosion resistance in the environment than other portions, and promotes local corrosion.

(2) M ₆ C type carbide has a non-coherent interface with the alloy matrix, and when internal stress such as external stress or residual stress is applied, discontinuity of deformation occurs at that portion and stress concentrates. This causes intergranular fracture at the incoherent interface and promotes stress corrosion cracking (SCC). In particular, it significantly accelerates dynamic corrosion and degrades the corrosion performance of the material.

As a result of conducting research based on the above findings, grain boundary fracture is suppressed even in the environment by selecting a predetermined alloy component system and precipitating WC type carbide instead of M ₆ C type carbide. It was clarified that a material showing good corrosion resistance could be obtained.

That is, since Mo is not contained in the WC carbide, a depletion region of Mo concentration cannot be formed around it. In addition, the local corrosion resistance of W is significantly improved in the environment, and even if a W-concentration damaged region is formed around the WC type carbide, it does not cause the local corrosion in the environment as described above. There was found.

Further, until now, W has the same action as Mo, and its effect has been considered to be about 1/2 due to the difference in atomic weight. However, W is added in this environment by selecting an appropriate alloy component system. It was revealed that it functions specifically and shows extremely good corrosion resistance. It also has the effect of promoting the precipitation of the γ "phase (mainly Ni ₃ Nb) that contributes to precipitation hardening, and has the advantage that high strength can be easily obtained.

That is, the present invention has been completed on the basis of such knowledge, and the gist of the present invention is Cr: 14.0 to 20.0%, W: 10.0 to 25.0%, Nb: 4.0 to 7.0
%, Fe: 2.0 to 10.0%, Ni: 50.0 to 60.0%, or at least one selected from the following at least one group: Ti: 0.5 to 2.0%, Ca: 0.0010 to 0.010%, and / or Mg: 0.0010.
~ 0.010%, Zr: 0.010 ~ 0.50%, Hf: 0.10 ~ 1.0%, Ta: 0.10 ~
At least one alloy selected from the group consisting of 1.0% is heated and held in the temperature range of 1000 to 1300 ° C for 1 to 200 hours to homogenize it, and then in the temperature range of 900 to 1300 ° C. After the first plastic working with a cross-section reduction rate of 10% or more once or twice or more,
Hold for 1 minute to 100 hours in the temperature range of 0 to 1250 ℃, then cool to the aging temperature (600 ℃ to 800 ℃) at the cooling rate from furnace cooling to air cooling and hold at 600 to 800 ℃ for 1 to 200 hours. It is characterized by precipitating WC-type carbides at the grain boundary parts by aging treatment, and has excellent intergranular fracture resistance in sour gas environments and excellent stress corrosion cracking resistance and hydrogen cracking resistance. This is a method for producing a Ni-based alloy.

According to another embodiment, the first solution heat treatment is applied to 98
0 to 1050 ° C for 1 minute to 20 hours, then second hot plastic working at 900 to 1050 ° C with a cross-section reduction rate of 20% or more, and further as second solution heat treatment at 900 to 1050 ° C for 1 minute to You may keep it for 100 hours. The subsequent cooling and aging treatment are the same as in the above case. A fine structure with an average grain size of 40 μm or less is obtained.

According to still another embodiment, the first solution heat treatment is performed at 900 to 980 ° C. for 20 to 100 hours, and then the second hot plastic working is performed at 900 to 1050 ° C. and the cross-section reduction rate is 20% or more. Processing may be performed. The second solution heat treatment is 900 ~
Perform at 1050 ℃ for 1 minute to 100 hours. The subsequent cooling and aging treatments are the same as those described above. A fine structure having an average crystal grain size of 20 μm or less is obtained.

In a specific embodiment for producing a thick tube of Ni-base alloy by the method according to the present invention, first, an alloy having the same composition as described above is subjected to a homogenizing treatment, and then 90
A round bar-shaped billet is produced by hot plastic working in the temperature range of 0 to 1300 ℃, and after punching in the center, plastic deformation with a cross-section reduction rate of 20% or more is added in the range of 1000 to 1200 ℃.
Hold for 1 minute to 100 hours in the temperature range of to 1050 ℃, and then cool to the aging temperature (600 ℃ to 800 ℃) at the cooling rate from furnace cooling to air cooling, then hold at 600 to 800 ℃ for 1 to 200 hours By aging treatment to precipitate WC-type carbides at the grain boundaries, which has excellent intergranular fracture resistance in sour gas environments and excellent stress corrosion cracking resistance and hydrogen cracking resistance. This is a method for manufacturing a thick tube of Ni-based alloy.

Thus, according to the present invention, in a corrosive environment,
Especially sour gas ^{_{(H 2 S -CO 2 -Cl -}} ) sulfur even in the environment
Even in an environment where (S) is mixed as a single substance, high strength (0.2
% Yield strength (room temperature)> 91kgf / mm ² ) and good resistance to stress corrosion cracking and hydrogen cracking. can get.

[0019]

Next, the reason why the Ni-based alloy component composition is limited as described above in the present invention will be explained.

Cr: Cr is, together with W, Ni, Fe, etc., γ ', γ "
It constitutes an austenite matrix for the precipitation hardening of phases. In the conventional sour gas environment, it was said to be particularly effective in corrosion resistance at high temperatures, but in such an environment, it contributes to the formation of a corrosion resistant film in balance with W, Ni and the like. For this, Cr ≧
14.0% is necessary, but Cr ≤ 20.0 from the viewpoint of structural stability
%.

It has been generally considered that W: W has the same function as that of Mo. However, by precipitating WC type carbides, grain boundary fracture is suppressed in the environment and good corrosion resistance performance is obtained. It was revealed that It also has the effect of promoting the precipitation of the γ "phase (mainly Ni ₃ Nb) that contributes to precipitation hardening, and has the advantage that high strength can be easily obtained. In this environment, the local corrosion resistance is significantly improved. The effect becomes remarkable when W ≧ 10.0%, but W ≦ 25.0% because W addition deteriorates hot workability.
And

Nb: Nb is the γ ″ −N that controls the strength of the alloy system.
It is necessary for the precipitation of i ₃ Nb (DO ₂₂ type ordered structure). Nb ≥ to obtain the prescribed strength (0.2% proof stress: room temperature) ≥ 91 kgf / mm ^2.
4.0% is required, but Nb ≤ 7.0% because a large amount of addition precipitates an undesirable second phase such as Laves phase formation.

Fe: Fe is an essential element for improving the precipitation hardening ability of the γ ', γ "phases. For that purpose, Fe ≥ 2.0% is necessary, but in consideration of the balance with the addition amount of other components. Fe Fe ≦
10.0%.

Ni: Ni is an essential element for precipitation hardening of the γ ', γ "phases, but also plays an important role in strengthening the corrosion resistant coating in the environment. Therefore, the balance of the alloy according to the present invention is substantially the same. Is Ni, that is, Ni ≧ 50%, and Ni from the viewpoint of balance with other components and hydrogen cracking resistance.
≦ 60% In the present invention, if desired, various other alloying elements may be contained.

Since Ti: Ti precipitates a γ'phase that deteriorates the corrosion performance when added in a large amount, it should be avoided to add more than necessary in the conventional alloy. However, the γ'phase promotes the precipitation hardening of the γ "phase and thus contributes to the increase in strength. Furthermore, in this alloy system, the grain boundary precipitation of WC improves the corrosion resistance, so it may be added positively. For this purpose, Ti ≥ 0.5% is required, but it is not necessary to add a large amount and Ti ≤ 2.0%.

Ca, Mg: Ca and Mg may be added as needed in order to improve hot workability, and particularly when thick material is required to be processed, its positive addition is desired. . Ca:
The effect is exhibited by adding one or two of 0.0010 to 0.010% and Mg: 0.0010 to 0.0100%.

Zr, Hf, Ta: Zr, Hf, Ta are added as needed to improve the machinability, and especially when it is necessary to process thick materials. Zr: 0.010 ~ 0.50
%, Hf: 0.10 to 1.0%, and Ta: 0.10 to 1.0%, the effect is exhibited by the addition of at least one selected from the group.

In the present invention, C, Si, Mn, P, S, N and B, which are usually contained in Ni-based alloys as unavoidable impurities, are used.
Although not specified, 0.07% and 0.30 respectively
%, 2.0%, 0.020%, 0.010%, 0.050%, 0.050%
Up to may be included. Also, Al may be contained up to about 0.30% as a deoxidizing agent. Next, the reason for limiting the manufacturing process in the present invention will be described.

[Melting Step] In the present invention, the melting step is not particularly limited as long as an alloy that is as clean as possible and has macrosegregation as small as possible is obtained, but generally, for example, vacuum After primary melting by induction melting, either as it is or ESR (El
ectro-Slag Remelting) or VAR (Vacuum Arc Remelti)
(ng) and then secondly melted to make an ingot.

In the present invention, the basic point of vacuum induction melting is to improve the cleanliness of the alloy, and if the oxygen content can be suppressed to several hundreds ppm (≦ 0.020%) or less, it is melted in an atmospheric furnace. Even if the primary ingot is used, the performance is not significantly deteriorated. In addition, the secondary dissolution of VAR and ESR is aimed at reducing macrosegregation of the ingot, and if the primary ingot cools sufficiently quickly and segregation is not significant, these secondary dissolutions may not be necessary. .

[Homogenization Treatment] Prior to hot plastic working of the obtained ingot, homogenization treatment is carried out in order to prevent micro-segregation and homogenize the structure to prevent cracks during working. In the alloy of the present invention, an intermetallic compound of Laves phase based on Cr ₂ Nb type is formed along with the concentrated segregation of Nb, W, Cr, etc. along with the microsegregation during solidification. Since this phase is extremely brittle and becomes a starting point of cracks during hot plastic deformation, it is necessary to diffuse and disappear by heat treatment.

For that purpose, it is desirable to perform heat treatment for a long time at a temperature as high as possible just below the melting point at which the diffusion rate of alloying elements such as Nb and W is large, but on the other hand, heat treatment at such a high temperature is a portion free from microsegregation. In order to cause the coarsening of the crystal grains of, it may rather adversely affect the workability, and heat treatment at a high temperature for a long time significantly increases the manufacturing cost, so considering the economic efficiency, The temperature was 1000 to 1300 ° C. and the time was 1 to 200 hours.

[First Hot Plastic Working] The hot plastic working conditions are heating temperature, working temperature range,
It is determined by the processing speed (strain rate) and the processing amount (strain amount). In the present invention, as the processing method of the solid product, three types, that is, normal forging (press and hammer type), high speed forging (four-sided hammer) and extrusion press, are selected as the basics.

First, in normal forging, it has the effect of eliminating the nonuniformity of the solidification structure and promoting the equiaxing of the crystal grains. For that purpose, it is necessary to deform by 10% or more in terms of cross-section reduction rate.
The heating temperature may be the same as the previous heat treatment, but the processing temperature does not exceed the melting point (≤1300 ° C) to prevent melt cracking,
In addition, it is necessary to set the temperature to 900 ° C or higher, which has good high-temperature deformability.
The processing (strain) speed is a deformation speed by a so-called press hammer and is about 1 to 10 ^-3 (1 / sec). At lower speeds, the temperature of the material drops significantly, and at higher speeds, the ductility of the material becomes insufficient.

Extrusion presses work more than normal forgings
(Strain) Although the speed is high, the material is subjected to compressive stress, so there is no work cracking that occurs during forging except for melt cracking. The heating temperature and processing temperature range may be the same as forging,
It has the advantage that the amount of processing (strain) can be extremely large.

Since high-speed forging has a higher processing (strain) speed than ordinary forging and is deformed from four directions,
Similar to the extrusion process, it has the advantage that work cracking of the material is less likely to occur. Furthermore, the greatest feature is that the temperature of the material does not drop due to heat generation during processing, so it also has the same effect as so-called constant temperature forging.

[First Solution Heat Treatment] After hot working, the temperature is kept at 900 ° C. or higher and 1050 ° C. or lower for 1 minute to 100 hours prior to cooling. In order to effectively precipitate the strengthening phase γ "mainly composed of Ni ₃ Nb by the subsequent aging treatment, the
The purpose is to form a solid solution and to precipitate the δ phase, which is a stable phase of the γ "phase, as a pretreatment for refining the crystal grain size during the second hot plastic working. When performing hot plastic working, it can be divided into the following two types: (i) 980 to 1050 ℃ × 1 minute to 20 hours (Nb solution treatment) (ii) 900 to 980 ℃ × 20 to 100 hours ( δ phase precipitation treatment).

[Second Hot-Plastic Working] In the present invention, after the above-mentioned first hot-plastic working, and further, if necessary, the above-mentioned first solution heat treatment, Reduction rate
20% or more plastic working is performed. You may perform by the operation similar to 1st hot plastic working.

In particular, by setting the heating temperature to 980 ° C. or higher and 1050 ° C. or higher and holding time of 1 minute to 20 hours, dynamic recrystallization is promoted within the range where the crystal grains are not coarsened, and fine crystal grains (average A crystal grain size ≦ 40 μm) is obtained.

On the other hand, before the high speed forging, by heating and holding in the temperature range of 900 to 980 ° C. for 20 to 100 hours, a large amount of δ phase mainly composed of Ni ₃ Nb was finely precipitated on the grain boundary / twin crystal interface. Then, high-speed forging allows superplastic deformation to be realized and ultra-fine grains (average grain size ≤ 20 μm) can be obtained.

The hot working in this case may be performed in the same manner as the above hot working, but the cross-section reduction rate is set to 20% or more. By combining it with the second solution heat treatment described later, it is possible to further refine the structure.

[Second Solution Heat Treatment] After the second hot plastic working, the solution heat treatment of heating at 900 to 1050 ° C. for 1 minute to 100 hours is performed. This is performed for the same purpose as the above-mentioned first solution heat treatment, and in this case, the upper limit of the heating temperature is 1050 ° C. at which the crystal grains are not coarsened.

[Cooling Treatment] After the solution heat treatment,
Continue cooling to the aging temperature (600 to 800 ° C) at the cooling rate from furnace cooling to air cooling. This is to promote the precipitation of WC type carbides, and the cooling rate is not limited to that extent.

[Aging treatment] The greatest feature of the present invention is
After the above solution treatment, without cooling to room temperature once
It is to precipitate WC carbides at grain boundaries. For effective precipitation, in addition to the above processing method, immediately after solution treatment, the aging temperature required for precipitation of γ "-Ni ₃ Nb (DO ₂₂ type ordered structure) from 600 to 800 ℃ from furnace cooling to air cooling Cool at the cooling rate of, and hold in that temperature range for 1 to 200 hours.

This aging treatment may be performed once or twice or more at different temperatures. However, it is necessary to avoid that the material is rapidly cooled to a temperature lower than the aging temperature before the aging after the solution treatment.

Thus, according to the present invention, it is possible to obtain a Ni-base alloy exhibiting an excellent intergranular fracture resistance that has not been seen in the past. Next, the function and effect of the present invention will be described more specifically with reference to Examples.

[0047]

EXAMPLES 150 kg of each alloy having the chemical composition shown in Table 1
Alternatively, in the 3 ton vacuum induction melting furnace,
The VAR was re-melted into a round ingot with a diameter of 150 mm, and the latter was re-melted into a round ingot with a diameter of 360 mm and 500 mm by ESR and VAR, respectively.

A representative example of the method for producing the test material is shown below.
The test conditions are also shown below. The test results are shown in Table 2. The abbreviation VIM stands for Vacuum Inducti
on Melting, VAR is Vacuum Arc Remelting.

Manufacturing method 1 VIM (150kg) → VAR (150φ) → homogenization treatment (1200 ° C × 24h)
→ (AC) → Hot forging (1120 ℃ × 4h heating, 1120 ~ 900 ℃ 75
(up to φ) → solution heat treatment (1040 ℃ × 2h) → (FC) → aging (7
00 ℃ × 8h → FC → 620 ℃ × 8h, AC).

Manufacturing method 2 (Example of repeating homogenizing treatment and plastic working twice) VIM (3 ton) → VAR (500φ) → homogenizing heat treatment (1200 ℃ × 24
h) → (AC) → hot forging (1160 ℃ × 8h heating, 1160 ~ 900 ℃
(Up to 450φ) → homogenization heat treatment (1200 ° C x 48h) → (AC) → hot forging (1160 ° C x 4h heating, 1160 to 900 ° C up to 200φ)
→ Solution heat treatment (1080 ℃ × 4h) → (FC) → Aging (700 ℃ × 8h)
→ FC → 620 ℃ × 8h, AC).

Manufacturing method 3 (Example of repeating homogenizing treatment and plastic working 3 times) VIM (3 ton) → VAR (500φ) → homogenizing heat treatment (1200 ℃ × 24
h) → (AC) → hot forging (1160 ℃ × 8h heating, 1160 ~ 900 ℃
(Up to 450φ) → homogenization heat treatment (1200 ° C x 48h) → (AC) → hot forging (1160 ° C x 4h heating, 1160 to 900 ° C up to 300φ)
→ Homogenization heat treatment (1200 ℃ × 24h) → (AC) → Upset forging (1160
℃ × 4h heating, 1160 ~ 900 ℃ to 450φ) → hot forging
(Heating at 1160 ℃ x 4h, up to 200φ at 1160 to 900 ℃) → (AC)
→ Solution heat treatment (1080 ℃ × 4h) → (FC) → Aging (700 ℃ × 8h)
→ FC → 620 ℃ × 8h, AC).

Manufacturing method 4 (as plastic working, after drilling,
Example of expanding and extruding holes) VIM (3 ton) → ESR (360φ) → homogenizing heat treatment (1200 ℃ × 24
h) → (AC) → hot forging (1120 ℃ × 4h heating, 1120 ~ 900 ℃
Up to 300φ → Machining of holes (outer diameter 300φ, inner diameter 60
φ) → Hot hole expansion processing (1120 ℃ heating, outer diameter 300 φ, inner diameter
154φ) → Hot extrusion (1120 ° C heating, outer diameter 200φ, inner diameter 150φ) → solution heat treatment (1040 ° C × 2h) (FC) → aging (700 ° C × 8h → FC → 620 ° C × 8h , AC).

Manufacturing method 5 (example of repeating plastic working and solution heat treatment) VIM (3 ton) → VAR (500φ) → homogenizing heat treatment (1120 ℃ × 24
h) → (AC) → hot forging (1160 ℃ × 8h heating, 1160 ~ 900 ℃
(Up to 450φ) → Homogenization heat treatment (1200 ℃ × 48h) → (AC) → Hot forging (1160 ℃ × 4h heating, 1160〜900 ℃ up to 300φ)
→ Solution heat treatment (1000 ℃ × 8h) → (AC) → High speed forging (1000
Up to 200φ at 900 ℃) → Solution heat treatment (1000 ℃ × 1h)
→ (AC) → Aging (700 ℃ × 8h → FC → 620 ℃ × 8h, AC).

Manufacturing method 6 (example in which plastic working and solution treatment are repeated to perform the first solution treatment at a low temperature for a long time) VIM (3 ton) → VAR (500φ) → homogenization heat treatment (1120 ° C × 24
h) → (AC) → hot forging (1160 ℃ × 8h heating, 1160 ~ 900 ℃
(Up to 450φ) → Homogenization heat treatment (1200 ℃ × 48h) → (AC) → Hot forging (1160 ℃ × 4h heating, 1160〜900 ℃ up to 300φ)
→ Solution heat treatment (950 ℃ × 20h) → (AC) → High speed forging (1000〜
(Up to 200φ at 900 ℃) → solution heat treatment (1000 ℃ × 1h) (A
C) → Aging (700 ° C × 8h → FC → 620 ° C × 8h, AC).

[Each test condition] 1. Tensile test Temperature: Room temperature Test piece: 6.0 mm φ × GL = 30 mm Strain rate: 1.0 × 10 ⁻³ s ⁻¹ Test item: 0.2% yield strength, elongation, drawing.

2. Dynamic stress corrosion cracking test Solution: Atmospheric 25% NaCl-1.5g / lS 7atmH ₂ S -20atmCO ₂ Temperature: 250 ° C Specimen: 4.0 mmφ × GL = 20mm Strain rate: 1.0 × 10 ^-6 s ^-1 Test item: Breaking time, diaphragm (evaluated by the ratio with the value in the atmosphere).

3. Hydrogen cracking test NACE condition: 5% NaCl-0.5% CH ₃ COOH 1 atmH ₂ S, 25 ° C Specimen: 2t × 10w × 75 l (mm) −R0.25U Notched carbon steel coupling Additional stress : 1.0 σy Immersion time: 1000h As shown in Table 2, in the present invention, the predetermined strength, that is, 0.2
Excellent stress corrosion cracking resistance and hydrogen cracking resistance of 91 kgf / mm ² or more at% proof stress (room temperature) were obtained.

[0058]

[Table 1]

[0059]

[Table 2]

Next, FIG. 1 is a graph showing the relationship between the heat treatment temperature and the dynamic stress corrosion cracking resistance of the alloy produced from the alloy No. 1 in Table 1 by the production method 1. In the figure
Indicates good corrosion resistance, and ● indicates poor. Similarly, during forging,
The relationship between the cross-section reduction rate and the dynamic stress corrosion cracking resistance is shown in a graph in FIG. In the figure, ○ indicates good corrosion resistance and ● indicates poor corrosion resistance.

Further, the test results of the hot ductility of Alloy No. 1 are shown in the graph of FIG. In this case, 1200 ℃ × 24h
After air-cooling, the temperature was raised to each test temperature and held for 5 minutes, and then tensile deformation was applied at a strain rate of 1 (1 / sec), and the drawing value at that time was obtained to evaluate the high temperature ductility. Precipitates obtained by the manufacturing method 1 for alloy No. 1 are collectively shown in Table 3 below.

[0062]

[Table 3]

Next, FIG. 4 is a graph showing the relationship between the cross-sectional reduction rate, the heating temperature, and the average grain size obtained when high speed forging is performed by the No. 5 alloy manufacturing method 5. FIG. 5 is a graph showing the relationship between the heat treatment conditions before high-speed forging and the average crystal grain obtained after forging according to the manufacturing method 6 of No. 6 alloy.

[0064]

As is evident from the foregoing description, according to the present invention, the sour gas _{(H 2 S-CO 2 -Cl} -) environment, especially sulfur (S) and good stress corrosion cracking resistance in an environment in which is mixed as a single A highly corrosion-resistant Ni-based alloy having hydrogen cracking resistance and used for oil well members (particularly, anti-throat and anti-bottom members) can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between heat treatment conditions and dynamic stress corrosion cracking resistance.

FIG. 2 is a graph showing the relationship between the rate of reduction in cross section during forging and dynamic stress corrosion cracking resistance.

FIG. 3 is a graph showing the test results for hot ductility.

FIG. 4 is a graph showing the relationship between thermomechanical treatment conditions and average crystal grain size.

FIG. 5 is a graph showing the relationship between thermomechanical processing conditions and average crystal grain size.

Claims (6)

[Claims] 1. In weight%, Cr: 14.0 to 20.0%, W: 10.0 to 25.0%, Nb: 4.0 to 7.0.
%, Fe: 2.0 to 10.0%, Ni: 50.0 to 60.0%, an alloy with a composition of 1 to 1 at a temperature range of 1000 to 1300 ° C.
After heating and holding for 200 hours, plastic working with a cross-section reduction rate of 10% or more is performed once or twice or more in the temperature range of 900 to 1300 ° C, and after holding in the temperature range of 900 to 1250 ° C for 1 minute to 100 hours, Aging treatment is performed by cooling at a cooling rate from furnace cooling to air cooling up to the subsequent aging temperature (600 to 800 ° C) and holding at 600 ° C to 800 ° C for 1 to 200 hours to precipitate WC type carbides at grain boundaries. A method for producing a Ni-based alloy having excellent intergranular fracture resistance in a sour gas environment, characterized by: 2. The alloy of the composition according to claim 1,
After heating and holding in the temperature range of 00 ℃ for 1 to 200 hours, 900 to 1300
Cross-section reduction rate of 10% or more in the temperature range of ℃ 1 or 2 times or more, and then hold at 980-1050 ℃ for 1 minute-20 hours, then cross-section reduction rate of 20% in 900-1050 ℃ range After the above plastic working, it is held at a temperature range of 900 to 1050 ℃ for 1 minute to 100 hours, and then the aging temperature (600 ℃ to 800 ℃) continues.
Aging treatment by cooling at a cooling rate from furnace cooling to air cooling and holding at 600 to 800 ° C for 1 to 200 hours to precipitate WC type carbides with an average grain size of 40 μm or less at the grain boundary part. And a method for producing a Ni-based alloy having excellent intergranular fracture resistance in a sour gas environment. 3. The alloy of the composition according to claim 1,
After heating and holding in the temperature range of 00 ℃ for 1 to 200 hours, 900 to 1300
In the temperature range of ℃, plastic deformation with a cross-section reduction rate of 10% or more is performed once or twice or more, and after heating and holding at 900 to 980 ℃ for 20 to 100 hours, cross-section reduction rate of 20% in the range of 900 to 1050 ℃. After the plastic working described above is added and the temperature range of 900 to 1050 ℃ is maintained for 1 minute to 100 hours, the aging temperature (600 ℃ to 800 ℃)
℃) at a cooling rate from furnace cooling to air cooling 600-800
Excellent grain boundary fracture resistance in sour gas environments characterized by precipitating WC type carbides with an average grain size of 20 μm or less at grain boundaries by holding at 1 ℃ for 1 to 200 hours For producing a Ni-based alloy having heat resistance. 4. The alloy having the above composition further has Ti: 0.5 to 2.
A method according to any of claims 1 to 3, comprising 0%. 5. The alloy having the above composition further has Ca: 0.0010 to
The method according to any one of claims 1 to 4, comprising 0.010% and / or Mg: 0.0010 to 0.010%. 6. The alloy of the above composition further has Zr: 0.010 to
The method according to any one of claims 1 to 5, comprising at least one selected from the group consisting of 0.50%, Hf: 0.10 to 1.0%, and Ta: 0.10 to 1.0%.