JPS58204145A - Anticorrosive nickel base alloy - 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 This invention relates to a nickel-based alloy with excellent corrosion resistance under corrosive conditions and excellent hot and cold workability, particularly suitable for use in highly corrosive sour gas wells. It is something.

Many of the alloys used commercially in applications requiring good corrosion resistance are nickel-based alloys. Such snails generally contain relatively large amounts of chromium and molybdenum, and usually contain a large amount of chromium and molybdenum.

Contains amounts of iron, copper or cobalt. For example, Alloy 0-276 is a well-known corrosion-resistant nickel-based alloy used in a variety of corrosive applications with a nominal composition of approximately 15.5% chromium, approximately 15.5% molybdenum, and approximately 15% tungsten. 8.5%, about 6% iron, about 2% cobalt II, and the balance nickel. Known corrosion resistant alloys are Alloy B-2, Alloy 625, and 718; Alloy B-
The nominal composition of 2 is approximately 28% molybdenum, approximately 1% chromium,
Approximately 2% iron, approximately 1% cobalt, and the balance nickel.
Alloy 625 contains about 21.5% chromium 211, about 9% molybdenum, about 4% iron, about 3.6% 1 niop, and the balance nickel, and alloy 718 contains about 19% chromium, about 8% molybdenum, about iron. 19%, about 5.1% niobium and the balance nickel.

Perhaps one of the most severe corrosive atmospheres for corrosion-resistant nickel-based alloys is found during the operation of deep sour gas wells, during which the casing, piping, and pond well components are exposed to high concentrations of high temperature under high temperature and pressure conditions. Under the action of moist hydrogen sulfide, brine and II.carbon dioxide.

Traditionally, the industry has relied on commercially available corrosion-resistant nickel-based alloys, such as those described above, developed for less severe pond applications. However, these alloys are subject to the harsh conditions found during the operation of sour gas wells).
However, it was not completely satisfactory. Although certain alloys have been developed that have high corrosion resistance, such alloys have high cobalt contents and therefore are significantly more expensive.

In the present invention, changing from oxidizing conditions to reducing conditions
・Outstanding corrosion resistance over a wide range of corrosive conditions
A nickel-based alloy has been found that exhibits particularly good performance in tests designed to mimic the extremely harsh corrosive atmospheres found during operation of deep sour gas wells. Furthermore, the alloy of the present invention has excellent thermal and cold workability and has a relatively low content of expensive alloying elements.

In the present invention, these and other advantageous properties are achieved by ensuring that chromium, molybdenum, and tungsten are closely balanced within the following weight percentages: Chromium from about 27 to 88 Molybdenum from about 8 to 12 Tungsten This is achieved in 5-karat gold.

A nickel-based alloy with such a strict balance of chromium, molybdenum, and tungsten is alloy σ-276.
, Alloy B-2, Alloy 718, and Alloy 625 exhibit superior corrosion resistance in a variety of solutions when compared to commercially available corrosion resistant alloys. Furthermore, based on the cost of the metals contained in the alloy, the alloy of the present invention is less expensive than some other commercially available nickel-based alloys that have poor corrosion resistance. The alloy of the present invention can easily be hot-flipped (1.

Because it can be machined, it can be formed into various desired shapes.
In addition, since it exhibits excellent cold workability, high strength can be imparted to the finished soup by cold working.

In practicing the present invention, the alloy is primarily t.

Chromium approximately 27-88%, molybdenum approximately 8-12%, tungsten approximately O-4%, iron approximately 1.5% or less, cobalt approximately 1
Less than 2%, about 0. 15% or less, aluminum A, l
1.5% or less of titanium, 2% or less of niobium, and the balance nickel.

A favorable result is obtained. Here, "consisting of" means that the alloy contains incidental impurities in addition to the listed elements, and that the alloy has new basic properties, particularly the corrosion resistance of the alloy. This means that other unspecified elements are added to the alloy that do not have a negative effect.

Chromium is an essential element in the alloy of the present invention.

The reason for this is that chromium contributes to increased corrosion resistance. Testing has shown that corrosion resistance is optimal when chromium is about 81% of the composition. 5 chromium is about 38%
When the amount increases, both hot workability and corrosion resistance deteriorate. Further, if the chromium content is less than about 27%, corrosion resistance deteriorates.

The presence of molybdenum provides excellent pitting resistance.

The optimum molybdenum content of about 10% is Ill in the test solution.
Shows the lowest corrosion rate. As the molybdenum content decreases below about 8%, pitting and crevice corrosion increases significantly.

The same thing happens when molybdenum increases above about 1z%, and hot and cold workability is further significantly reduced.

Tungsten is not normally included in commercial alloys developed for corrosion resistance. Although this element is commonly used in applications where increased strength, particularly at elevated temperatures, is of primary interest, it is generally not considered to have a beneficial effect on corrosion resistance and is not used. However, in the alloys of the present invention, the presence of tungsten was found to significantly increase corrosion resistance. Corrosion tests showed that the corrosion rate was significantly faster in the absence of tungsten, and that the corrosion rate was significantly faster when the tungsten content was greater than about 4% (Ikegata's material).
It was shown that the alloy corroded at a faster rate in some solutions and the alloy became more difficult to hot work. The optimum tungsten content at a 10% molybdenum level is about 2%, but replacing some or all of the tungsten with additional molybdenum (1) shows good corrosion resistance in some test media (Table 1). , alloy y).

The alloys of the present invention also typically contain carbon at levels below about 0.15%, either as an impurity associated with tf or as an additive for the purpose of forming stable carbides. The 14° carbon level is preferably maintained at a level below a maximum of about 0.08 weight percent F1, most preferably about 0.04 weight percent.

1 Cobalt and nickel are generally considered to be interchangeable;
impart similar properties to alloys. 2...Tests have shown that replacing a portion of the nickel content with cobalt does not adversely affect the corrosion resistance and processability properties of the alloy. Therefore, if required, add approximately 12% cobalt to the alloy.
It can be contained at a level as low as 1. However, cobalt...

Due to the current high prices, replacing Kotsukel with cobalt is not economically attractive.

Aluminum can be present in small amounts to act as an oxygen scavenger. The aluminum is preferably about 1.5% by weight, most preferably about 0.25%, =I+.
Present in amounts up to % by weight.

Also, small amounts of titanium and niobium can be present to act as carbide forming agents. These elements are preferably included at a level of about 1.5% titanium or less and about 2% niobium or less, most preferably at a level of about 0.415% or less. However, it has been found that addition of these elements in significantly higher amounts has an adverse effect on hot workability.

In addition, the alloy of the present invention contains small amounts of impurities as impurities in the raw materials used, or as previously known! It can be included as an intentional addition to improve certain properties such as... For example, the 6° test, which can optionally contain small proportions of magnesium, cerium, lanthanum, yttrium or mitschmetal to contribute to the 7]0 workability, can contain about 6° magnesium without significant loss of corrosion resistance. Preferably about 0% boron to contribute to high temperature strength and toughness has been shown to be acceptable up to 0.10%, preferably 0.07%.
．． It can be added up to 0.005%. Tantalum can be present at levels up to about 2% without adversely affecting corrosion resistance or Ill or JJD processability, but the presence of tantalum at this level does not positively affect these properties of the alloy. was not observed to give.

Similarly, vanadium is up to about 1%, and zircon is about 0.11%.
It can be present up to %.

Large amounts of iron reduce the corrosion resistance of the alloy. Iron is about 1.5%
Levels up to and including this are acceptable, but above this level corrosion resistance is quite significantly reduced. Copper, manganese and silicon are acceptable if present in small amounts or as impurities; however, these elements may be may reduce the corrosion resistance of the alloy, or reduce the workability, or reduce the corrosion resistance and workability of the alloy.

I understand. For example, the corrosion resistance of the alloy is significantly worse when copper is present at a level of about 1.5% or higher, or when manganese is present at a level of about 2% or higher.

The invention will be described with reference to the following examples. These ten examples illustrate a number of specific alloy compositions of the alloy of the present invention and compare its corrosion resistance to other known corrosion resistant nickel-based alloys. These examples are provided to aid in understanding the invention and are not intended to limit the invention.

Example 1 Heat of several inventive alloy compositions
), and the chemical compositions of these alloys are shown in Table 1. Alloy A
Indicated as ~M. The percentages given in Table 1 are weight percentages of the total alloy composition and represent the nominal 2..composition, ie, one portion of each element weighed to melt.

Cold-worked and annealed specimens of various alloys with a surface area of approximately Φ square inches (25.8 cm2) were prepared and weighed.
Corrosion test in various test solutions and then.

These samples were dried, reweighed, and the weight loss was determined in grams, which was converted to M/year (mil 7 years).

Test 1 is a standard test method that uses a ferric chloride solution to measure pitting and split cracking resistance.

The specimens were placed in a 10 wt% ferric chloride solution at 50°C.
; Soaked for 72 hours. This test method is similar to ASTM Standard Test Method G48-76, but the ASTM test uses 6% ferric chloride by weight. In Test 2, the sample was immersed in a boiling jQ% sodium chloride-5% ferric chloride aqueous solution for 24 hours. Test 3 is a standard test method for detecting susceptibility to intergranular attack in 11-wrought nickel-rich chromium-containing alloys (ASTM Test Method G□ 28-72). In this test, the sample is boiled with ferric sulfate.
It was immersed in 50% @ acid aqueous solution for 24 hours. ! In the test prefecture, samples were immersed in boiling 65% nitric acid for 24 hours.

For comparison, several commercially available corrosion-resistant alloys (alloy B-
2, Alloy 0-276, Alloy 18, and 1625)
were tested in the same manner and the test results 1 of these are also shown in Table 1.

These tests show that, with very few exceptions, the alloy of the present invention has the following properties when compared with the commercially available No. 1 corrosion-resistant alloy mentioned above:
It can be seen that excellent corrosion resistance was exhibited under the above test conditions F.

Example 2 Two of the alloys of Example 1 were cold reduced in cross-sectional area by 70% in a roll mill. A sample of alloy 0-276 was similarly reduced. These alloys were then tested in test solutions. The test results are shown in Table 2 below.

Table 2 These tests show that the alloys of the present invention are resistant to corrosion in the test solutions when compared to cold reduction conditions. It can be clearly seen that the properties are significantly superior to Alloy 0-276.

Example 8 Test specimens of two types of alloys of the invention (Alloy N and Alloy O) were used in a corrosive sour gas well in an oil field.

Corrosion tests designed to evaluate performance in a hydrogen sulfide atmosphere (Tests A, B and C) and in a simulated scrubber atmosphere (Test D) were conducted.

Alloys N and 0 had the following nominal chemical composition = Or
81%, MO10%, W2%, NbO, 40%,;1
゜Ti 0.25%, A/ 0.25%, S max 0.0
01%, 1re maximum 0.10%, Qu maximum 0.10%,
OO, 04%, S max 0.015%, 00 max 0.25
%, S maximum 0.015%, Ta maximum 0.10%, zrS
Maximum 010%, In maximum 0.10%, ■ Maximum 0.01%
, 'Si up to 0025%, Remaining W, Nl-o 1'' For comparison, specimens of alloy 0-276 were evaluated under similar conditions. All eight materials had 260% Si after unidirectional cold working.
Tested under 500'F aged and non-aged conditions.

The mechanical properties of the test pieces of the eight alloys are shown in Table 84 below.

Table 8 0.2% Offset Proof Strength Tensile Strength Elongation 5 (k
si) (ksi) (%) Alloy A (uninvented) Cold working 128.4 155.1
17.6 Alloy 0 (Invention) Cold working 1'14゜0 156.6
15.8 Alloy 0-276 (control) Cold worked 168.8 208.7
1? , 5 1. These eight materials were tested in the following four atmospheres: A- Shoe Compound Stress Crack NAOE Solution 24″C
B-Hydrogen embrittlement NAOE solution 246C
(Stay Iruka way) 〇-Hydrogen embrittlement 5%) [, SOj+AS
24”C (i=z5mVm”) D-Weight loss due to corrosion [Green Death Boiling point (G
reen Death month (7%H, SO,, 8%Hat.

1%Feel 1%OuO/81 I All embrittlement tests were conducted using 111 with stress applied at three points.
．． 125M (4,875 inches) x 6.85
tnm (0.25F inch)
, 094 inch) beam specimen was used. Non-aged materials were stressed to 80-100% of the yield strength of each material. 0260"C aged samples for 5 hours were stressed to 100% of the yield strength of each material. 2. - In the weight loss test, 15Q, 8 mm (2 inches) x 15.
875 VM (0,625 inch) x 1.5879
m (0,062515 inch) test specimens were used. Test A-0 was conducted for 28 days. In the test, two test pieces were
4 hours, 72 hours and 168 hours.

Inspected and weighed at the end.

Test A NAOE solution (5% Nap/+0
．． 5%01 (,0OOH, saturated with 100% H2S gas)
The beam specimens, which had been stressed to 80-100% of their yield strength, were placed in a NAGE solution for 28 days. All specimens showed no visible signs of corrosion and were recovered undamaged.

Test B-24''. 6 water 8 brittle in ON A OE solution.

Steel couples were attached to beam specimens stressed to 80-100% of yield strength and placed in NAOK solution for 28 days. All beams were recovered without any damage.

Test C - 5% H2So4+1 rtui/at 24°C
A nickel-chromium wire was spot welded to the end of the beam 5, which was stressed to 80 to 100% of the arsenite yield strength. Next, the beam specimen was placed in the test solution and a current of 25 mvm was passed to generate hydrogen at the cathode.
Alloy 0-276 aged under stress was found to fail at the end of 18 days. 100 resistance 10 strength
Alloy 0-276 under unaged conditions stressed to 2
It was rejected after one day. The specimens of alloys N and 0 are 2
It was recovered undamaged at the end of the 8 day test.

Sample *D-r Green Death” solution (boiling 11i1e 1
% H, So.

A test piece of each material for the weight loss test due to corrosion in +8% H (3/+1% yect + x% Our/8) was weighed, the crack was made small, and the sample was placed in "Green Death" solution for 2. I put it in. The specimens were cleaned and reweighed after 24 hours, 72 hours and 168 hours. The specimens of alloys N and O are
As shown in Table 4, alloy 0-27 suffers from heavy compaction due to corrosion.
It was significantly smaller than the test piece No. 6.

Table 4 Corrosion rate battle/year (Mill 7 years) 24 hours 72 hours 168 hours Alloy N0069X10-'2 (0,27) 0088X
10-”(0,15) 1.78X10-”(0,7)
Alloy 0 0.25 tt (Q, 11
0.76 tt (0,a)0.51 //
(0,21 alloy 0-276 (control) l.14/
/ (0,45) 0.81 p (0,82)
1.07/l (0°) These tests demonstrate that the performance of the alloy of the present invention in a simulated oil field hydrogen sulfide atmosphere is superior to that of alloy Q-276 and squid, and It is shown that the corrosion resistance of the invention alloy □ under simulated scrubber atmosphere ("green death") test conditions is clearly superior to alloy 0-276.

Example 4 A series of tests were conducted to examine the effects of varying the amounts of chromium, molybdenum, tungsten, copper, and iron on corrosion resistance. The base alloy composition (Heat 867) was as follows: Or 81%, MOlo %, W2
%, GO, 2%, 'I'i 0.25%
, A4 0.25%, Nb O, 40%, balance Nlo
For each case of the elements nichrome, molybdenum, tungsten, copper and iron, the heat was prepared by varying the bond of that element and keeping all other specified elements constant. δ1 specimens were prepared as in Example 1. It was prepared and tested in the same manner as in Example 1 under the conditions of Test #2 and Test #8. The test results are shown in Table 5.

Claims (1)

[Scope of Claims] L A nickel-based alloy having excellent hot and cold cutting properties and excellent corrosion resistance in various atmospheres including the atmosphere of deep sour gas wells, wherein the alloy contains about 27% chromium. ~38%, Molybdenum approx. 8-1
2% and about 0-4+% tungsten. The alloy of claim 1, wherein λ chromium is present at a level of about 81% and molybdenum is present at a level of about lθ%. +5 Alloy according to claim 2, wherein tungsten is present at a level of about 2%. Table: Nickel-based alloys with excellent hot and cold workability and excellent corrosion resistance in a variety of atmospheres, including the atmosphere of deep sour gas wells, mainly contain about 27 to 88% chromium and about 8 to 1% molybdenum.
2%, tungsten about 0-4%, iron about 1.5% or less, cobalt about 12% or less, carbon about 0.15% or less, aluminum about 1.5% or more, titanium about 1.5% or less, A corrosion-resistant nickel-based alloy comprising about 2% or more of niobium and the balance nickel. 6. The alloy of claim 4 wherein tungsten is present at a level of about 2%. & Molybdenum is present at a level of about 10%) Alloy O I of Claim 5 The alloy of Claim 4 containing O% tungsten and about 12% molybdenum. & Mainly about 81% chromium, about 101% molybdenum.
%, Tungsten approx. 2%, Iron approx. 1.5% or less, Cobalt approx. 4% or less, Carbon approx. O, OS% or more F1 Aluminum approx.
, 25% or less, titanium approximately 0.40% or more F, niobium approximately 0.
The alloy according to item 4 in the range of requirements #1-m, comprising 40% or less of nickel and the remainder S. −・