JPS581043A - High strength alloy having superior stress corrosion cracking resistance for oil well pipe - Google Patents

Abstract

PURPOSE:To provide an alloy having improved stress corrosion cracking resistance for high strength oil well pipe under adverse environments by sepcifying the contents of Ni, Cr, Mn, Mo, W, etc. in steel and the relations among respective additive components. CONSTITUTION:An alloy consisting of <=0.1wt% C, <=1.0% Si, 3-20% Mn, <=0.030% P, <=0.005% S, <=0.5% solAl, >=1 kind of 20-60% Ni, 22.5-30% Cr, <8% Mo and <16% W and the balance Fe and unavoidable impurities. The alloy of the compsn. wherein the conditions >=70% Cr%+ 10Mo%+5W%, >= 25% 1/2Mn%+Ni%, and <8% 4%<=Mo%+1/2W% are satisfied. If necessary, Cu, Co, rare earth elements, Y, Mg, Ti, etc. are contained in this alloy. The alloy for oil well pipes having the high strength that withstands petroleum excavation in deep wells and severe working environments sufficiently and superior stress corrosion cracking resistance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an alloy that has high strength and excellent stress corrosion cracking resistance and is particularly suitable for use in the manufacture of oil country tubular goods where these properties are required.

In recent years, due to the deterioration of the energy situation, there has been a marked tendency for oil and natural gas wells to become deeper;
Some deep wells with a depth of 10,000 m or more have appeared.

Furthermore, due to similar circumstances, it is becoming increasingly difficult to extract oil and natural gas in a harsh corrosive environment containing humid hydrogen sulfide, as well as corrosive components such as carbon dioxide gas and chloride ions.

As oil and natural gas are drilled in such harsh environments, the oil country tubular goods used therein are required to have high strength and excellent corrosion resistance, especially resistance to stress corrosion cracking. .

As a general anti-corrosion measure for oil country tubular goods, it is known to introduce a corrosion suppressant called an inhibitor, but this method is often not effective for use in, for example, offshore oil wells.

From this point of view, consideration has recently begun to be given to the use of high-grade corrosion-resistant high-alloy steels such as stainless steel and Incoloy and Hastelloy (all trade names) for the production of oil country tubular goods. H2S
The details of the corrosion behavior of -C'02-Ct- in an oil well environment have not yet been fully elucidated, and the current situation is that it does not have the high strength required for oil country tubular goods for deep wells. .

Therefore, from the above-mentioned viewpoint, the present inventors have developed a material with high strength and excellent stress corrosion resistance that can sufficiently withstand oil drilling in deep wells and harsh corrosive environments, especially in H2S-CO2-Ct- oil well environments. As a result of research to obtain crackable oil country tubular goods, it was found that (a) The main type of corrosion in the H2S-CO2-C1- environment is stress corrosion cracking, and the stress corrosion cracking behavior in this case is as follows: The behavior is completely different from the general force in austenitic stainless steel. That is, while general stress corrosion cracking is deeply related to the presence of Ct-, in the oil well environment mentioned above, the influence of H2S is greater than that of Ct-.

(b) Steel pipes used for practical use as oil country tubular goods are generally subjected to cold working to improve their strength, and cold working significantly reduces the resistance to stress corrosion cracking.

(C) The elution rate (corrosion rate) of steel in the H2S-'CO2-CL- environment is determined by the alloying components Ni, Cr,
Mn, Mo.

Depending on the content of Mo and W, corrosion resistance is maintained by a surface film composed of these components, and these components increase the resistance to stress corrosion cracking.
It is 10 times more effective than TiCr, Mo is twice as effective as W, and even more effective than MnFiNi. Therefore, these components are Cr (fi + 10 Mo (4 + 5 W ( %)≧
70%.

4 Mn (Aya + Ni (@≧25%).

4chi≦MO＋　4　w　(chi)〈8chi.

Satisfy the conditional expression and reduce the N1 content to 20 to 60%.
, the Cr content is 22.5 to 30%, and the Mn content is 3 to 20%.It is a cold-worked material, especially in the oil well environment of H2S-Co2-C1-, which is extremely corrosive. It is possible to obtain a surface film that exhibits excellent resistance to stress corrosion cracking in a harsh environment of 200°C or less.

(a) As for Ni, it lasts only by its effect on the surface film, and it also has the effect of increasing stress corrosion cracking resistance structurally. .

(,) By containing N as an alloy component in the range of 0.05 to 0.3%, the alloy strength can be improved to a greater extent.

(f) 8 content as an unavoidable impurity is O, OOO
When it is reduced to less than '/', the hot workability of the alloy is significantly improved.

C) When the P content as an unavoidable impurity is reduced to 0.003% or less, the hydrogen cracking susceptibility is significantly reduced.

(h) Cu: 2% or less and CO as alloy components:
2- When one or two of the following are contained, corrosion resistance is further improved.

(1) Rare earth elements +0.10% or less as alloy components,
Y: 0.20 inch or less, Mg: 0.10 inch or less, T
By containing one or more of the following: 1:0.5% or less and Ca: 0.10% or less, the hot workability is further improved to 7.

The findings shown in (a) to (1) above were obtained.

Therefore, this invention was made based on the above findings, and includes C: 0.1% or less, Sl: 1.0% or less, Mn: 3 to 20%, P: 0.030%. below.

Preferably p:o for the purpose of further improving hydrogen cracking resistance.
, o03chi or less, S: 0.005% or less, preferably S:O,OOO' for the purpose of further improving hot workability.
7 inches or less, sot, A1: 0.5 inches or less, Ni:
20-60%.

Cr: Contains 22.5 to 30%, MO: less than 8% and W: less than 16%, and contains one or two of them,
Furthermore, if necessary, N: 0.05-0.3%,
Cu: 2% or less, Co: 2% or less, rare earth elements: 0.1
0- or less, y: o, +ao- or less), M8F IJ, 1
13 II onwards.

Contains one or more of Ti: 0.5% or less and Ca: 0.10% or less, with the remainder consisting of Fe and unavoidable impurities (the above weight %, the following Cr(@ +
10Mo (@-1-5w≧70%.

+ Mn (9g) + Ni (4≧25%.

4%≦MO++W(%)<8%.

The alloy satisfies the following conditional expression, has high strength and excellent resistance to stress corrosion cracking, and is particularly suitable for use in manufacturing oil country tubular goods which require these properties.

Next, the reason why the composition range of the alloy of the present invention is limited as described above will be explained.

(a) If the C content exceeds 0.10%, stress corrosion cracking tends to occur at grain boundaries, so the upper limit value was set to 0.10%.
It was decided that

(b) 5i Si is a necessary component as a deoxidizing component, but if its content exceeds 1.0%, hot workability will deteriorate, so the upper limit is set at 1.0%. Established.

(c) Mn In order to ensure the desired excellent stress corrosion cracking resistance, it is necessary to contain 3 or more, but if the content exceeds 20%, hot workability will deteriorate. Its content was determined to be 3 to 20 inches.

(a) p The P component as an unavoidable impurity has a content of 0.
If it exceeds 0.30%, the effect of increasing stress corrosion cracking susceptibility appears, so it is necessary to set the upper limit as o, o3o% to keep stress corrosion cracking susceptibility to a low state. Also, P
It has been found that as the content is reduced, the hydrogen cracking resistance is rapidly improved by filling 0.00.3 g, and from this point of view, When properties are required, the P content is preferably 0.0030% or less.

(e) S The S component as an unavoidable impurity has a content of O, O
If O exceeds 5%, it has the effect of deteriorating hot workability, so it is necessary to set the upper limit to 0.005% to prevent deterioration of hot workability. In this way, the S component has the effect of deteriorating hot workability when its content increases, but when its content is lowered to 7% O, OOO', on the contrary, hot workability deteriorates. If hot working under severe conditions is required, it is desirable to set the S content to 0.0007% or less, as this results in further improvement.

(f) AI M is effective as a deoxidizing component like Sl and Mn.
), sol, AQ content up to 0.5% does not impair the properties of the alloy, so the content was determined to be 0.5% or less in terms of SOM content.

(g) Ni Although the Ni component has the effect of improving the stress corrosion cracking resistance of the alloy, if its content is less than 20%, the desired excellent stress corrosion cracking resistance cannot be secured; %
Even if the content exceeds 20%, the effect of further improving stress corrosion cracking resistance does not appear, and taking economic efficiency into account, the content was set at 20% to 60%.

(h) Cr Cr components are Ni, Mn, Mo, and W
It is a component that significantly improves stress corrosion cracking resistance when coexisting with other components, but if its content is less than 22.54 (it does not improve hot workability, and on the contrary, In order to ensure stress corrosion cracking resistance, the content of MO and W must be increased accordingly, which would be economically disadvantageous, so the lower limit was set at 22.5%. If the content exceeds 30%, deterioration of hot workability cannot be avoided no matter how much the S content is reduced, so the upper limit was set at 30%.

(i) Mo and W As mentioned above, these components include Ni, Mn, C
Coexistence with r has an even effect of improving stress corrosion cracking resistance, but Mo: 8% or more and W: 1
Even if the H2 content is 6% or more, the environmental temperature is 200℃ or less.
In the corrosive environment of S-CO2-CL-, no further improvement effect was observed, and in consideration of economic efficiency, the respective contents were determined to be less than 8% for Mo and less than 16% for W. Also,
Regarding the content of Mo and W, the conditional expression: Mo(# 10 +
The reason for specifying W (%) is that the atoms/amount of W is about twice that of Mo, and the effect is about 10%, which makes them equal.If this value is less than 4%, the The desired stress corrosion cracking resistance cannot be obtained under the above-mentioned adverse environment, and on the other hand, even if this value is set to 8 or more, the above-mentioned structure will contain substantially unnecessary amounts of Mo and W. From this point of view, the value of MO(→++W) was determined to be less than 4% to 8%.

(j) N Since the N component has the effect of improving strength through solid solution strengthening, it is included as necessary when particularly high strength is required, but if the content is less than 0.05%, the desired strength cannot be achieved. No improvement effect can be obtained, and if the content exceeds 0.3%, melting and ingot making become difficult, so the content was set at 0.05 to 0.3%.

(→Cu and c.

These components have a uniform effect of improving the corrosion resistance of the alloy, and CO has a solid solution strengthening effect, so it is included as necessary especially when even better corrosion resistance is required. , If Cu exceeds 2%, hot workability deteriorates.On the other hand, even if Co exceeds 2%, no further improvement effect will appear, so the upper limit values are set respectively. Cu: 2% and Co: 2% were determined.

(4 rare earth elements, YlMg, T1., and Ca) These components have a uniform effect of further improving hot workability, so they may be included as necessary when hot working is performed under severe conditions. However, rare earth elements: 0 and 1, respectively.
0%, Y: 0.20%.

Mg: O, l 0%, Ti: 0.5%, and Ca:
Even if the content of O exceeds 10%, no improvement effect on hot workability is observed, and even a deterioration phenomenon appears.
% or less, Y: 0.20% or less, Mg: 0.10% or less, Ti: 0.5% or less, and Ca: 0.10%
It was determined as follows.

(') Cr(@+ l OMo(4+ 5 W (
%) Figure 1 shows the relationship between cr(@+ l OMo(1+ 5 W Yes, that is, cr.

Cr-Ni-Mn-Mo system, Cr-Ni with various contents of Ni, Mn, Mo, and W
- Mn-W series and Cr-Ni-Mn-Mo-W series steels are melted, cast, forged, and hot rolled to achieve plate thickness: '
I1m plate material, then this plate material, temperature: 1050
After being held at ℃ for 30 minutes and subjected to water-cooling solution treatment, cold working was applied at a processing rate of 30% for the purpose of improving strength, and the resulting steel plate was rolled perpendicularly to the rolling direction to a thickness of 2 mm Cut out test pieces in the order of width = 1011" x length = 75, and apply a tensile force equivalent to 0.2% proof stress to the test piece S using the three-point support beam jig shown in Figure 2. 10 atm H2S and 10 atm C under stress
20% Na saturated with H2S and CO2 with O2
A stress corrosion cracking test was conducted by immersing the test piece in a Ct solution (temperature: 200°C) for 1000 hours, and after the test, the presence or absence of cracking in the test piece was observed.

Based on these results, the inventors independently set a conditional expression: ' Cr (%) + l OMo (@+ 5 W
It has become clear that there is a relationship between +Mn (C%) and +Mn (# 10Ni (@) with respect to stress corrosion cracking resistance, as shown in Figure 1. In Figure 1, ○
The mark indicates no cracking, and the x mark indicates the cracking number. From the results shown in Figure 1, Cr(@ +
10Mo (%il + 5W .

In addition, in the alloy of this invention, B is included as an unavoidable impurity.
, Sn, Pb, and Zn each in a range of 0.1% or less does not impair the properties of the alloy of the present invention.

In addition, when producing the alloy oil country tubular goods of this invention, it is generally first melted in an electric furnace, then subjected to Ar-oxygen decarburization treatment (AOD), and then made into a steel ingot of about 2 tons. , heated to a temperature of 1050-1250℃ to make diameter: 1
Blooming into a 50g 1φ billet, then again 1050
After heating to a temperature of ~1250°C, the raw tube is formed by hot processing such as extrusion, and in this case, the hot working temperature is set to 1000°C or less where recrystallization does not proceed, and the wall thickness reduction rate is 30-30°C. Hot working under the above conditions is effective for increasing the strength of the tube material, and furthermore, the hot-rolled raw tube is subjected to solution treatment directly or at a temperature of 850 to 1150°C. In this state, cold working such as drawing is performed at a wall thickness reduction rate of 10 to 60 inches, preferably 20 to 40 inches. is obtained.

Next, the alloy of the present invention will be explained by comparing it with examples, comparative examples, and conventional examples.

In each of the examples, a molten metal having the composition shown in Table 1 was heated in a conventional electric furnace, an Ar-oxygen decarburization furnace (AOD furnace) for the purpose of desulfurization and N addition, and further dephosphorization as necessary. After melting using an electroslag melting furnace (ESR furnace) for the purpose of
Next, this ingot was hot forged at a temperature of 1200°C to form a billet with a diameter of 150 silk φ, and in this case, for the purpose of evaluating hot workability, it was observed whether or not cracks occurred in the billet. Subsequently, the billet was subjected to multi-hot extrusion to form a raw tube with a diameter of 601 gφ x wall thickness: 4 mm, and then cold worked by 22% by drawing to obtain a diameter: By setting the dimensions to 55 mtφ x wall thickness: 3.111, the alloy tube materials 1 to 29 of the present invention. Comparative alloy tube materials 1 to 6. and conventional alloy tube materials 1 to 4 were manufactured, respectively.

In addition, Comparative Alloy Tube Materials 1 to 6 all have compositions in which the content of one of the constituent components (indicated with an asterisk in Table 1) is outside the scope of the present invention. In addition, the conventional alloy tube material 1 has a composition corresponding to JIS-8US 316, 2 to JIS-8US 3108, 3 to Incoloy 800, and 4 to JIS SUS 329J1. be.

Next, the resulting alloy tube materials 1 to 29 of the present invention were prepared. Comparative alloy tube materials 1 to 6.・A test piece of length: 2011 was cut out from conventional alloy tube materials 1 to 4, and a portion corresponding to 60° was cut off along the length direction of the test piece. As shown in the front view, a bolt passes through the tube and is tightened with a nut to apply a tensile stress equivalent to 0.2% proof stress to the outer surface of the tube, and the H2S partial pressure is H2S - 10 atm CO2 - 20% N at 0.1 atm, 1 atm, and 15 atm
A stress corrosion cracking test was carried out by immersion in aC1 solution (liquid temperature: 200°C) for 1000 hours, and the presence or absence of stress corrosion cracking after the test was investigated. The results are shown in Table 2 together with the presence or absence of cracking during hot forging, the tensile test results, and the impact test results.

In Table 2, the marks Q indicate those with no cracks, while the marks X indicate those with cracks.

From the results shown in Table 2, comparative alloy tube materials 1 to 6 were inferior in at least one of the following properties: hot workability, stress corrosion cracking resistance, and strength.
The alloy tube materials 1 to 29 of the present invention all have excellent hot workability and stress corrosion cracking resistance, and also have high strength and good hot workability, but have relatively low strength. Conventional alloy pipe materials 1 to 4 with low stress resistance and inferior corrosion cracking resistance
It is clear that it has even better characteristics when compared to

As mentioned above, the alloy of the present invention has particularly high strength and excellent resistance to stress corrosion cracking, making it suitable for use in oil and natural gas extraction in harsh environments where these properties are required. It exhibits extremely excellent performance when used as oil country tubular goods and geothermal country tubular goods.

[Brief explanation of the drawing]

Figure 1 shows the stress corrosion cracking resistance of the alloy, 4Mn(1).
+ Ni ('l) and cr (1) + 10 Mo (
@ + 5 W (Figures 2 and 3 are diagrams showing the relationship with @, respectively, are diagrams showing aspects of stress corrosion cracking tests on plate-shaped and tubular specimens. Applicant: Sumitomo Metal Industries, Ltd. Agent Tomi 1) Kazufu 1 Cr (%) + IOMo (%) + 5 W (%) Continued from page 1 0 Inventor Hiroo Ikeda Sumitomo Metal Industries, Ltd., 1-3 Nishinagasu Hondori, Amagasaki City Inventor: Daiji Moroishi, 1-3 Nishinagasu Hondori, Amagasaki City, Sumitomo Metal Industries, Ltd., Central Technology Research Institute

Claims (1)

[Claims] (1) C: 0.1% or less, St: 1. o$ or less, Mu: 3-2'Ogb, P: O, 030% or less,
S: 0.005% or less. sot, M: O-516 or less, yi: 20~
60%, Cr: 22.5-30%, Mo:
It contains one or two of the following: less than 8% W and less than 16% W, with the balance consisting of Fe and unavoidable impurities (the above weight %), and. cr($ + 1 ova@ + 5 W <@≧10
blood. A high-strength oil country tubular alloy with excellent stress corrosion cracking resistance that satisfies the following conditions. C: 0.1qIj or less, Si: 1.0% or less, Mn: 3-2' OL P: 0.030% or less, S
: 0.005% or less. soL, AI Q, 5% or less, Ni: 20-60%,
Cr: 22.5 to 30%, Mo: less than 8% and W: less than 16%, one or two of them;
Furthermore, one of Cu: 2% or less and Co: 2% or less
It has a composition (weight% or more) containing one or two species, and the remainder consists of Fe and unavoidable impurities, and er(@ +
10 MO(91) + s w (@≧10chi. + Mrh(99+Ni61)≧25chi. 4chi≦Mo (equity) ++W (to) <8chi. Stress resistance characterized by satisfying the following conditions. High strength alloy for oil country tubular goods with excellent corrosion cracking resistance. -(3) C: 0.1g6 or less, Si: 1.09J
Below, Mn: 3 to 20 mm, P: (1030 mm or less,
S: 0.005% or less. BOl, ldl: 0.5% or less, N1: 20
~6096. Cr: Contains 22.5-30fi, M
o: less than 896 and W: less than 16-, and further contains rare earth elements: 0.10% or less, Y: O, 20% or less, Mg: O, 10% or less,
Ti: 0.5 S or less, Oyo UCa: 0.10
% or less, with the remainder consisting of Fe and unavoidable impurities (weight %), and cr (91) + I C + Mo (%)'-1-5W (
@≧′10%. +Mn(＠+N1(1525%. ) C: 0.1% or less, Si: 1.0% or less, M
n: 3-20%, p: 0.030 or less, S
:0. O05chi or less. sot, AQ: 0-5% or less, Ni: 20
~60%, Cr:22.5~30%, Mo+8
% and W: less than 16%, and further contains one or two of Cu: 2% or less and Co: 2% or less, and rare earth elements: 0.10% or less. . Y2 0.20% or less, Mg: 0.10% or less, 'l
Contains one or more of the following: i: 0.5% or less, and Ca: 0.10% or less, with the remainder consisting of Fe and unavoidable impurities (weight% or more) , and Cr (@+i 0MO(visit+5 W) (@≧70
%. +Mn (%') 10Ni (LE)≧25chi. A high-strength oil country tubular alloy with excellent stress corrosion cracking resistance that satisfies the following conditions: 4CH≦MO(%) 10+W (#<8%. (5) C: 0.1% or less , Si: 1.0
% or less, Mn: 3 to 20 inches, p: o, 030 inches or less, 3
: 0.005% or less. sot, kl: 0.5% or less, N: 0.05-0
．． 3chi, N1: 20-60%, Cr: 22.5-30
%, M. One or two of the following: less than 28% and W: less than 16%
A composition containing seeds, with the remainder consisting of Fe and unavoidable impurities (
or more weight%), and CrC + 10Mo (%)
+ 5 w (1270%. (6) C: 0.1% or less, Si: 1.0% or less,
Mn: 3-20%, p: 0.030% or less, S: 0
．． O05chi or less. sol, M: 0.5% or less, N: 0.0
5-0.3%, Ni: 20-60%, Cr: 2
Contains 2.5-30%, M. One or two of less than 28 inches and W: less than 16%
Contains seeds, and further contains C'u: 2% or less and CO: 2%
Contains one or two of the following 1, with the remaining 9 consisting of Fe and unavoidable impurities (weight%), and C, (@ + 10Mo (%) + 5 W (%) ≧ 7
0%. +Mn(@+Ni(@≧25%.4%≦Mo(a))++W(@<8ch.) A high-strength oil country pipe alloy with excellent stress corrosion cracking resistance. (- /) C: 0.1% or less, sl: 1.0% or less, Mn
: 3~20chi, P: 0.030% or less 3+0.00
Less than 5%. soLM: 0.5% or less, N: 0.05-0.
3%, N1: 20~60%, Cr: 22.5~
Contains 30.4 and M. Contains one or two of the following: less than 28% and W:, less than 16%, and further contains rare earth elements: 0.1.0%
Below, Y20, 20% or less, Mg: 0.1.0%
Containing one or more of Ti: 0.5% or less and Ca: 0.10% or less, the remainder having a composition (weight %) consisting of Fe and unavoidable impurities, Power)
Cr (%) + 10 MO (@+ 5 W (%)
)≧'i'o%. + Mn(@+N i@)≧25 rice cake. A high-strength oil country tubular alloy with excellent stress corrosion cracking resistance that satisfies the following conditions: 4CH≦Mo (%) + +W (%) (8%) (8) C: 0.1% Hereinafter, Si: 1.0% or less,
Mn: 3 to 20 inches, P: 0.030 inches or less, S: 0.
005% or less. sot, M: 0.5% or less, N: 0. O
j ~0.3%, Nl: 20~60%, C
r: Contains 22.5-30%, M. = less than 88% and W: Contains one or two of less than 16%, further contains one or two of Cu: 2% or less and CO: 2% or less, and rare earth element: 0.10
% or less, Y:, O,, 20% or less, Mg: 0
．． 10 Ti or less, Ti: 0.50% or less, and Ca
Cr(q6) + I O , Mo (%) + 5 w (
#≧70chi. + Mn (%) 10N1 (%)≧25-24chi≦Mo(
@+ + W (chi)〈8chi. A high-strength oil country tubular alloy with excellent stress corrosion cracking resistance that satisfies the following conditions.