JPS58221252A - Cold workable solid solution - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides nickel-chromium-molybdenum (N1-Cr
-Mo) alloy, and more particularly Ni-Cr-, which has a combination of sufficiently high yield strength and corrosion resistance to be suitable for use as tubular products in sour gas well environments.
Regarding Mo alloy.

BACKGROUND OF THE INVENTION As is well known to those skilled in the art, the problem of providing alloy tubing suitable for use in oil and gas wells is
For at least the last 30-40 years, it has been one of the few remaining. In recent years, demands for increased energy production have accentuated this problem, particularly with regard to natural gas production from sour wells.

A review of the literature suggests that from a historical point of view, and above all from economic considerations, low-alloy steels are primarily considered. However, due to the more aggressive environments encountered in recent years, more advanced high alloy materials such as alloy C-276
, MP-35N, alloy 625, titanium, etc., are attracting attention. Comparatively speaking, the cost of these latter materials is higher than alloy steel, but the enormous costs associated with catastrophe from tube defects make such materials commercially the best candidates for deep sour gas well production. It is said that

The acceptable requirements for sour gas well alloys are a direct result of the environment in which the alloy must be used. These environments are quite complex, and they require high corrosion resistance and high yield strength of the alloy.

Corrosive Environment of Natural Gas Wells Many different forms of corrosion are at play in natural gas production. These include (1) hydrogen sulfide stress cracking (H2SO) caused by in-situ generated H2S, (11) chloride stress corrosion cracking (C8CC), (lli) pitting corrosion, and general corrosion. Some of them, especially H
85C and cscc can also be considered self-destructive. Furthermore, 1.4 Xl02MPa (20,0009
si) or higher bottom hole pressure and approximately 232-260°C (approximately 4
The fact that operating temperatures of 50-500''F') may be encountered only serves to intensify the destruction caused by such a destructive environment.

1 Hydrogen sulfide stress cracking sour natural gas wells typically contain H2S, CO2, CI
(4 (methanes)), and underground brine.A typical analysis of natural gas is 35-45% H2S
.

It shows 8-12% CO3 and 45-55% CH4, as well as subsurface irrigation. Although H2S in the absence of water is considered relatively harmless, the presence of water causes H2S corrosion attack. At this time, hydrogen is released, which in turn infiltrates or diffuses into the pipe material, causing "hydrogen brittleness." This brittleness is accompanied by tensile stress and ultimately causes cracking.

Low alloy steels, especially high yield strength steels, exhibit a significant tendency to suffer from this type of defect. The use of specialized inhibitors is not a satisfactory panacea in deep wells.

11 Chloride Stress Corrosion Cracking Particularly in deep wells, the release of chloride ions causes defects, and this defect is called chloride stress corrosion cracking (CSCC). This corrosion cracking is due to a particularly difficult cause at higher working temperatures. Stainless steel clearly shows susceptibility to this type of defect.

111 Well Aging Another phenomenon encountered in deep sour gas wells is that the tubing can suffer property degradation over time during prolonged exposure to high temperatures, 250-300°C.

This tends to reduce the alloy's ability to resist crack growth and propagation.

1v Pitting Another possible source of defects is pitting that can occur due to chloride attack. Thin-walled tubing appears to present a disadvantage in this regard. No further need be added here other than to state that the test data presented below shows that alloys within the scope of the present invention have high pitting resistance.

■ General Corrosion General corrosion can be characterized as a loss of weight in the metal, reducing the ability of alloy materials to withstand such pressures and loads. This is also quite critical in deep wells. This is due to the requirement (or desire) to use "thin" walled tubing for clearance purposes and to maximize natural gas flow.

From the foregoing, the use in sour natural gas wells, especially deep sour wells (i.e. approximately 4,600 m (15,00 m)
Potential alloy candidates for use to depths greater than 0Ofset) must handle and withstand the most severe corrosive environments. At the same time, the alloy candidate must have a high yield strength, which is enhanced by the use of thin-walled tubing and resistance to tensile defects under high axial loads and a tendency to collapse and fracture. This enables high flow rates of natural gas.

However, alloys of the type that characterize this invention must be cold workable in order to produce the required strength. This alloy requires high levels of work hardening. In addition, “residual ductility” is a factor that should be considered.
However, it is also necessary that the level is at an acceptable level. This can be described as the amount of ductility remaining after cold working. A high degree of residual ductility is essential because of the considerable strains that are likely to be encountered in LeSour gas well tubes during service.

Other properties such as hot workability and assembleability are required. In terms of metallurgical structure, the presence of secondary phases should be avoided as they cause brittle defects.

In summary, what is needed is a high strength alloy that (1) is cold workable and (11) is characterized by the following: Ill high residual ductility, (1v) hot workability, and absence of harmful phases. Moreover, this alloy is sometimes used in sour gas wells (i'1~90 MPa (10,000
~13,000 pal) high pressure, approximately 232~2
Deep sour gas wells (approximately 4,600 m (approximately 1
(vl) at a depth exceeding 5,000 f@et
It exhibits high resistance to hydrogen sulfide stress cracking, (vt6 chloride stress corrosion cracking, -well aging, (IX) pitting corrosion, and (x) general corrosion.

Nl-Cr-Mo alloys of special and interrelated compositions to those described herein can be produced;
This alloy has 1030 RIIPa (150,000P
It is currently known to meet the above requirements with a yield strength well in excess of sl ).

Generally speaking and in accordance with the present invention, the alloys contemplated herein contain chromium and molybdenum in a total amount of about 4 to about 40% and up to about 20 cs of iron (with the exception of chromium and molybdenum). preferably not more than about 46%),
It contains up to about 0.06% carbon, up to about 1% each of titanium and aluminum, up to 1% silicon, and the substantial balance nickel.

In terms of other elements, many components are considered harmful, especially phosphorus, manganese and sulfur.

These elements should be kept as low as possible.

In this regard, manganese, if present,
Niobium is not required, most preferably not exceeding %. Test results show that it can exist as a negative role player.

There is no reason why it should exceed 0.5%. Copper is not required and can be kept at low levels. Cobalt, which can be present up to 25%, does not provide any significant benefit commensurate with the additional cost. For example, boron up to 0.1% and mlsch metal in amounts up to 0.1% are useful tempering additives.

In putting the invention into practice, care must be taken to achieve the proper compositional balance. Otherwise, early corrosion defects can easily occur or other problems can easily surface. In this connection,
Chromium levels should not be reduced below about 20% to obtain sufficient pitting resistance and H88C and CSCC resistance. If there is a benefit from molybdenum,
- Chromium does not need to exceed about 30 cm. In some cases, chromium can be reduced to 15%. However, this requires high levels of molybdenum, which is undesirable in terms of processing properties.

While molybdenum contributes significantly to obtaining resistance to the aforementioned forms of corrosion, it is also responsible for providing the highest degree of work hardening. If the working conditions of pressure and temperature imposed by the depth of the well are not harsh, perhaps about 5
A low amount of molybdenum of 7% to 8% is used while together with chromium at least 7-8% to ensure a high level of corrosion resistance.
It is advantageous to adopt a molybdenum content of %. In this regard, the sum of chromium and molybdenum is preferably about 3
Should be 3- or higher. However, when this total exceeds about 40 inches, problems other than corrosion-related effects are too easily experienced. For example, excessive levels of chromium and molybdenum can cause hot working problems (alloy brittleness) as shown below. Furthermore, 15
At molybdenum A-cents of 1 or more, the alloy tends to be less ductile. The amount of molybdenum is preferably kept between 8 and 12%.

Residual ductility is emphasized. Chromium and molybdenum are known to have a significant influence in this regard. Therefore, the following relationship should be accepted when determining the maximum residual ductility. Cr il (2 times the amount of Mo)
%Cr-2(%Mo)) should not be less than about 2 and should not be more than 12.

Iron is considered useful as shown by the NACE H2S test (described below). Iron also lowers alloy costs. According to the present invention, iron from 5 inches to 15-2
Preferably, it is present at levels as high as 0%. Excess iron can cause undesirable structural phases, especially at the upper end of the chromium to molybdenum range. To avoid secondary phases such as sigma, the sum of chromium, molybdenum, and iron should be kept below about 46 inches.

As other elements, aluminum and titanium can be used as tempering additives and also contribute to processability. Preferably, the alloys of the present invention contain about 0.05% to 0.3% of either or both of these components. Phosphorus and sulfur reduce the resistance to cracking of both the ) I28 and chloride types. As indicated hereinabove, these components should be kept at as low a level as possible. Troublesome problems also exist in manganese, particularly with respect to chloride stress corrosion cracking. Manganese is 0
．． Should be maintained at a level below 3 or 0.2 inches. Although silicon is not harmful to manganese, it is preferable not to exceed 0.5 inch in order to obtain an acceptable level of hydrogen stress cracking resistance.

Carbon, although virtually unavoidable, destroys ductility. Magnesium and zirconium can be used for grain refinement. Other than increased density and cost, tungsten does not appear to offer any particular advantages. Therefore, the carbon content is preferably about 0.03%
The magnesium and/or zirconium can be present in amounts up to 0.1% or more.

Regarding the manufacturing method, the alloy is manufactured at a temperature of approximately 1070-1180°C (approximately 1
950-2150'F), preferably about 1090-11
It can also be a solution annealed at 50°C (2000-2100"F) for 0.5-5 hours, such as 1-2 hours. Additionally, the alloy is cooled and then cold worked. Air cooling can be used.

Cold working on the order of about 40% or more
Approximately 1210 MPa (approximately 175.0001)si)
It usually gives a yield strength of the order of . A cold work range of 40% to 50% is generally satisfactory. Since the alloy is an annealed solution, the cold workable type here does not require the aid of an aging process. When high aluminum/titanium is not present, the alloy may not be able to age harden.

The following data is provided to give those skilled in the art a good overview of the nature of the invention.

A large number of alloys, namely fit and Asada's heat (approximately 4
51 tg) were prepared both within and outside the scope of this invention by induction melting using high purity charge materials. The ingot is hot rolled into, for example, a 1511111 thick sheet, and the annealed solution is then cold rolled to increase its strength and the amount of cold rolling is varied. Table 1 relates to alloys with major elemental changes, whereas Table 2 relates to alloys in which the major components are nominally Ni-25%-10% Mo* with minor elemental changes.

H2S stress corrosion test specimen is National Ansoeiation C
tested against the standard test solution adopted by the National Institute of Orrosion Engineers (NACE), a solution saturated with H2S gas and containing 5 g glacial acetic acid and 50 g NaCl in 945 g H20 (NACE 5pee, 8 standard TM
-01-77). This solution is used by oil and natural gas production equipment to test sensitivity to H2S gas at ambient temperatures.

The specimens are of varying yield strength, usually 100%.
, the oblong sample was loaded and bent at three points with a small electrical insulation test fixture that was stressed at . Cold rolled material was heated at 260-315°C for various times before testing.
The samples were oriented transversely from the cold-worked plate. (Note, special samples were first deformed in order to determine the load-strain characteristics.) The test samples were then loaded in the fixture to a predetermined deflection corresponding to the desired stress level. Several U-bend specimens were also tested. All samples were It was brought into contact with a small piece to form a Garno ζ-2 cut ring.

The yield strength (0.2% offset), applied stress level and H85C results are given in Table ■. As will be noted, a pair of samples were tested over a five week test period.

Additional results are reported in Table 111-A. These data include U-bend tests in NACE H2S solution. As you will see, the test period has been changed as shown.

Chloride stress corrosion cracking This test was conducted using a U-shaped bent sample.

The sample was loaded with Zelto made of alloy C-276 and the test
It was carried out in a hydrogen sulfide saturated solution containing 5% NaCl, 0.5% acetic acid and 1 g/l elemental sulfur.

Various temperatures are used as shown in Table 1, with higher temperatures representing, of course, more harsh environments. This test was performed by Vaughn
and Greer (Paper No., to SPE 924
1980.5ociety of P@troleum
Engineers). The results are given in Tables ■ and Tables NA.

Pitting Corrosion Test In this case, the ferric chloride test was adopted. The entire sample was immersed in a 5% ferric chloride solution for approximately 50" (72 hours) (see ASTM 5 standard Part 1 for details).
0, see S@ationG). Good correlation between pitting behavior in ferric chloride and observations in other environments closely similar to the sour gas well environment has been reported in the literature.

Electrochemical tests were performed at pH 10.0 adjusted to pH 2 with hydrochloric acid.
00 ppm (NaCl) solution at +50'C.

Scans were performed at 61 Jyf/hr to characterize pitting resistance. The current density during the scan advance at +0.6 certs for a standard calomel electrode was used as a measure of pitting behavior (P, ElMorris and R,C.

Corrosion by 5earberry, Vo
1, 28.1972, p. 444). Data are reported in Table ■.

Work Hardening and Residual Ductility The rate of work hardening is important because the alloys of this invention must be cold worked to the desired strength.

Therefore, the true strain behavior of a number of alloys has been determined by tensile tests in which the load and sample diameter are determined periodically until cracking (see Table ■).

To characterize the “residual ductility” we use,
1241 MPa (180 kai
) subtracts the strain that causes the alloy to work harden. Therefore, the reported value (Table ■) is 1241 MPa (180
It is a measure of the ductility remaining after work hardening to a yield strength of 0.1 kml).

Alloys M, N, O and P all cracked during hot working and could not be tested. It is noted that the molybdenum and/or sum of chromium and molybdenum were at high levels. As mentioned earlier, this only leads to hot working problems.

(19) Table 1 A 14,7 9,8 6,2 . 023 0,16
B 14,7 9,9 10,7. 021 0,1
0c 9.9 9.7 11.0. 035 0,1
5D I5,0 4.8 11.1. 035 0.
09E 14.2 16,0 10,3. 069
0.15F 26.7 11.0 0. 020 0
, 18G 18,7 2.8 16,9 . 001
0.11H18,87,916,8,0070,11J
27,8 9,8 0. 011 0.06K
24,7 10.1. 034 0.25L 1
4.9 9,7 10.4. 031 0.11M
19,8 20.3 11,4. 024 0.1 ON
24.7 20.7 10.3. 023 0,1
00 21.1 25.5 10.8. 035 0,
09P 26,5 15.7 11.9. 018
0,161 19.4 10,1 10,8 . 032
0,092 19.4 14°1 9,5. 031
0,143 23.8 9.8 9.4. 034
0.164 29.1 8,3 9,6. 070 0
．． 175 18.7 14,5 13,9 . 003
0.096 28.0 10.3 16.0. 005
0,087 25.7 9,8 0. 030 0.
17(2(1) 304- TI Others 0.10 - 0.10 0.09 - 0.10 0.23 0.07 1.9Cb O0123,0Cb Oll 3.ICb Oool 2.ICb 1.40 3.ICb O,092,7Cu O105 0,05 0,04 0,10 0,10 0,08 0,07 0,08 0,09 0,06 0,10 Table 1 S 24,6 10,0 9,1 0. ()5 0j
)5T 24,7 9.6 10,1 0,05 0
,06U 23,8 10,7 10.3 (1,
(13(1, (18V 24.9 10,0 10.
I n, (16(1,05W 24.9 10,0
10.1 11.06 0,0510 24.7 9
,6 10.1 (1,(+5 041611 24
．． 3 9,4 10.5 fl, 11 (1,09
1224,39,410,50,110,091323
,010,710,30,050,0B14 24.9
10,0 10,1 0. r16 0. +1515
24.8 10.1 10,1 0,06 0,06I
P1 24,8 10.1 10,1 0,06 0.
t) 617 24.9 10,3 10.1 Fl,
15 0,1818 24.9 10.3 10.1
0,35 0,342] 23,4 9.6 10.
0 (1,080,052224,610,69,9
0,120,122324,610,69,9n,12
0.12C Others, 005. 2281 + , 53Mn, 120
−． 820. 016P, 025 0,45Mn, 025 0,95Mn, 005-, 005-. 067-1027. 012Mg, 027. 012Mg→-, 08Zr, 020
．． 007P, 025 0.20Mn, 010 0,2381. 010 1.1081. 007-. 007-8007-1021-. 021 3,3W, 003. 018P, 003. 018P +, 024B (21) Table ■ F = One or both fail in 5 weeks or less t Yield strength Applied stress level W
147 1014 100
P(22) 305-- Table 1l-A U-shaped bending outer surface fiber stress Time to defect Alloy (
ksi) (MPa) (Sun) F 176
1213 21,21S 175
1207 63+, 63+T 191
1317 63+, 63-1-U
190 1310 63+, 63
+V 177 1220 63+,
63+W 173 1193 63
+, 63+1 172 1186
63-+-, 63+2 196 1351
21, 213 192 1324
21, 63+7 163 1124
21, 638 167 1151
63+, 63+9 186 1
282 63+, 63+10 19
1 1317 63+, 63+13
187 1289 63+, 63+
16 173 1193, 21.
2117 179 1234 63
+, 63+18 167 1151
63+ 63+ Table V Ferric chloride weight loss A after 15 days at 2O4°C
Excellent B Excellent C not allowed 1,175 D Kei -〇Good R not allowed 1,836 71 O V O,707 0 1 out of 2 0.477 3 0.365 6 Good 90.812 To 111 40 50 160.353 2.100 2, 500 6, 400 s, oo.

40 B, 000 1.080 20 85 (6) A general examination of the data shows that alloys within the scope of the invention behave quite well. Alloys currently being considered for deep sour gas well tubing, particularly alloy C-273,
It is understood that MP-35-N and 625 will all break fairly quickly.

For example, in the NACEH2S U-bend test, such alloys crack in a period of 1 to 2 weeks.

The NACE H28 test has shown that many alloys survive stress levels on the order of 1200 MPa. Additionally, alloys within the scope of the present invention were tested for chloride at 288°C (500°C).
It can be seen that commercially available materials fail rapidly in this test. These results are considered to be very significant.

Table ■ Work hardening behavior, tensile strength of 0,4 A 180 1241 B 184 1269 C1681158 D 155 10691
177 12206 154
1062 Table ■ Residual ductility, true strain until collapse minus 1241 MPa (180 ksi) B
0.43 C0036 D O,61' 0 0.38 RO,79 10,41 110,75 120,89 130,93 A number of alloys outside the invention have poor performance after cold working in terms of residual dullness. It shows good ductility. Alloy alloys are such alloys. Alloy 1 has a critical composition.

Furthermore, it does not satisfy the relationship that %Cr-2 (%Mo) is equal to or exceeds 2 and does not exceed 12. Alloy 1 would not be recommended for sour gas wells, although there are a number of alloys within the scope of this invention that are characterized by a sufficiently satisfactory combination of properties, including residual ductility. Alloys 11,12 and 13 are excellent.

Four similar weight castings were prepared to see what problems would occur if commercially sized ingots were made. 20.3 Lll with thermal top for heat dissipation
l X 20.3 Lllll X 35.6 countries (8"
Manufactured as a 300 lb P heat cast in a 8" x 14" sand mold. Casting has a cross-sectional area of 0.0
On the order of 93 m2 (1 sguare feet), it is close to the solidification that occurs during the in-pit. The nominal chemical composition of the ingot is shown in Table ■.

Table ■ 24 25 10 1.0 Remainder However, large amounts of secondary phases were observed in other alloys. Sheets from all four castings were 2.5-1.3α (1-0.5 inch) thick and tested at 1150°C (2100°C) without any signs of cracking.
'P) was successfully hot rolled. Secondary phase portions were not seen in the hot rolled alloys and were still seen in polyacids in alloys XXY and 2. Thus, the chemical composition of the latter alloy was in excess of Cr+Mo+F. This total cap should be maintained at a level not exceeding about 46.

While the present invention is primarily utilized for deep sour gas wells,
It can also be used in a variety of different applications requiring a material that combines high strength with high corrosion resistance. Such applications include intermediate natural gas wells, deep sour oil wells, water and marine environments, purifiers, chemical plant equipment (tubing, pipes, etc.), aircraft and space applications. Finished manufacturing forms include forgings, bars, extrusions, and sheets. Other structural shapes include fasteners, valves, bins, shafts and rotors.

Applicant's agent Kiyoshi Inomata

Claims (1)

[Claims] 1. (lHjtf: hydrogen stress cracking, (11) chloride stress corrosion cracking, (Ill) JL corrosion or pitting, and (lv
) Characterized by a high degree of resistance to general corrosion,
Furthermore, (v) high yield strength exceeding 1030 MPa, (V
l) good residual ductility, υ1) resistance to well aging, and l/ii9 giving good hot workability and O
X) Cold-workable solid solution nickel-chromium-molybdenum alloys characterized by the ability to avoid the presence of harmful amounts of secondary phases, containing 4 to 30% chromium, 8 to 12
molybdenum (however, the total of chromium and molybdenum is 29-40%, and the amount of chromium minus twice the amount of molybdenum is 2-12%), iron (however, 5-15%) (the sum of molybdenum and iron does not exceed 46%), at least one member from the group aluminum and titanium (0.05 to 0.5 (1))
000%, up to 0.05% carbon, up to 0.5% niobium if present, up to 0.5% silicon, up to 0.2% manganese, and the substantial balance nickel. A solid solution alloy characterized by: 2. Characterized by a high degree of resistance to (1) hydrogen sulfide stress cracking, (11) chloride stress corrosion cracking, (+++) pitting/pitting corrosion, and (lv) general corrosion;
V) high yield strength exceeding 1030 MPa, (vi) good residual ductility, ←11) resistance to well aging, and Gll+- giving good hot workability and (lX)
A cold-workable solid solution nickel-chromium-molybdenum alloy characterized by the ability to avoid the presence of harmful secondary phases, comprising ~30% chromium and 8-12% molybdenum (with the exception of chromium The total of and molybdenum is 2
9 to 40%, and the amount of chromium minus twice the amount of molybdenum is 2 to 12%), 5 to 15 inches of iron (however, the total of chromium, molybdenum, and iron does not exceed 46 inches) ,
At least one kind of 0 from aluminum and titanium
．． 0.5% to 0.5%, carbon up to 0.05%, niobium up to 0.5(2)% if present, silicon up to 0.5%, manganese up to 0.2%, and substantially Damage tubing for use in sour gas well environments made from the above solid solution alloys containing a balance of nickel. 3. An alloy according to claim 1 characterized by 23-27% chromium and 8-12% molybdenum. 4.Claim 1 in which carbon does not exceed 0.03%
Alloys listed in section. 5. The alloy according to claim 1, wherein the total content of chromium and molybdenum is 31 to 38%. 6, the tube bud is exposed to a deep sour gas well environment at a depth of at least 4600 m, bottom well temperature greater than 300 °C, and pressure greater than 69 MPa and H2S. A pipe according to claim 2, which is in contact with a corrosive environment containing CO2, CH4 and underground brine. 7.15-30% chromium, 7-15.96 molybdenum, l' □ (However, the total of chromium and molybdenum is 29-40%
), up to 20% iron, up to 0.1% carbon, up to 1% each aluminum, titanium, and silicon, 0.
Manganese up to 3%, boron at 0.1%*, 0.1%
A high-strength, corrosion-resistant nickel-chromium-molybdenum alloy consisting of up to 100% of Mitshu metal, up to 600% of cobalt, and the substantial balance nickel.