JPH0372698B2 - - Google Patents

Description

[Detailed description of the invention]

This invention has high strength and excellent corrosion resistance, especially excellent stress corrosion cracking resistance, and is suitable for use in oil country tubular goods used in oil and natural gas extraction under severe conditions where these properties are required. This relates to alloys suitable for. In recent years, there has been a marked trend toward deeper oil and gas wells, and in addition, the oil and gas produced contain wet hydrogen sulfide (H ₂ S), carbon dioxide gas (CO ₂ ), and chlorine ions (Cl 2 ). ^- ) and other corrosive components are increasingly included. As the well depth increases in this way, the pressure of the crude oil and gas produced, as well as the earth pressure of the formation, increases, and the tensile load due to the own weight of the oil country tubular goods used also increases. The oil country tubular goods used for this are not only required to have high strength to withstand these forces, but also to be able to withstand H ₂ S, CO ₂ ,
_This is an excellent response ^since stress corrosion cracking is the main cause of corrosion in oil and gas well environments _containing corrosive components such ^as It is required to have resistance to force corrosion cracking. On the other hand, a common method for preventing corrosion of oil country tubular goods is to inject a corrosion inhibitor called an inhibitor into the oil country tubular goods, but this method is not effective when oil and gas wells are located offshore. It is often not possible to utilize it, and sufficient results cannot be expected. Furthermore, a method of coating oil country tubular goods with a protective film may be used, but in this case as well, sufficient corrosion prevention results cannot be expected. In view of these circumstances, attempts have recently been made to use stainless steel, high-grade materials such as Incoloy and Hastelloy (both trade names) in the production of oil country tubular goods, but among these materials, Incoloy in particular and Hastelloy are both expensive.
Not only are they expensive because they contain a large amount of Ni, but the details of the corrosion behavior of both materials in the H ₂ S−CO ₂ −Cl ^-oil well environment have not yet been fully elucidated. Moreover, it does not have the high strength required for oil country tubular goods for deep wells. Therefore, from the above-mentioned point of view, the present inventors have investigated the problem of deep wells and severe corrosive environments, especially H ₂ S-CO ₂
-Cl ^-As a result of research to obtain a material for oil country tubular goods that has high strength and excellent stress corrosion cracking resistance that can withstand oil and natural gas extraction in an oil well environment, (a) H ₂ S- The main type of corrosion in the CO ₂ −Cl ^-oil well environment is stress corrosion cracking, but the behavior of stress corrosion cracking in this case is completely different from that of general stress corrosion cracking in austenitic stainless steel. thing. In other words, whereas general stress corrosion cracking is deeply related to the presence of Cl ^- , in the H ₂ S−CO ₂ −Cl ^- oil well environment, not only Cl ^- but also H ₂ The influence of S is large. (b) Steel pipes used for practical use as oil country tubular goods are generally subjected to cold working to improve their strength, but cold working significantly reduces the resistance to stress corrosion cracking mentioned above. (c) H ₂ S−CO ₂ −Cl ^- The leaching rate (corrosion rate) of steel in an oil well environment is
Depending on the content of Mn, corrosion resistance is maintained by a surface film made of these components, and these components also increase resistance to stress corrosion cracking. effective and also
Mo has the same effect as Cr, and W has the same effect as Cr.
1/2Mn (%) + Ni (%): 18% or more, Cr (%) + Mo (%) + 1/2W (%): 20% or more, Mo (%) + 1 /2W (%): less than 1.5 to 4.0%, and satisfies the following, Mn: 3.0 to 15.0%, Cr:
Contains less than 18.0 to 22.5%, Ni: 15.0 to 40.0%,
Furthermore, if one or both of Mo: less than 4.0% and W: less than 8.0% is contained, H ₂ S-
CO ₂ −Cl ^−H ₂ S− under oil well environment, especially below 150℃
A surface film that exhibits excellent resistance to stress corrosion cracking in a CO ₂ −Cl ⁻ oil well environment can be obtained. (d) The Ni component not only acts on the surface film, but also has the effect of increasing stress corrosion cracking resistance structurally. (e) Including 0.1 to 0.4% N as an alloy component further improves the alloy strength. (f) When 0.05 to 3.0% of Co is contained as an alloy component, the alloy becomes further solid solution strengthened and work strengthened, and the stress corrosion cracking resistance also improves. (g) Including 0.05 to 3.0% Cu as an alloy component further improves the strength and corrosion resistance of the alloy. (h) Rare earth elements as alloy components: 0.001 to 0.10%,
Y: 0.001-0.20%, Mg: 0.001-0.10%, Ca:
When one or two of Ti: 0.001 to 0.10% and Ti: 0.005 to 0.50% are contained, the hot workability of the alloy is further improved. The findings shown in (a) to (h) above were obtained. Therefore, this invention was made based on the above knowledge, and includes C: 0.1% or less, Si:
1.0% or less, Mn: 3.0-15.0%, P: 0.030% or less,
S: 0.010% or less, sol.Al: 0.5% or less, Cr: 18.0
~Less than 22.5%, Ni: 15.0~40.0%, N: 0.1~0.4%
Contains one or two of Mo: less than 4.0% and W: less than 8.0%, and further contains Co: 0.05 to 3.0%, Cu: 0.05 to 3.0%, rare earth element: 0.001-0.10%, Y: 0.001-0.20%,
Mg: 0.001~0.10%, Ca: 0.001~0.10%, and
Ti: Contains one or more of 0.005 to 0.50%, and 1/2Mn (%) + Ni (%): 18% or more, Cr (%) + Mo (%) + 1/2W (%) : 20% or more, Mo (%) + 1/2 W (%): 1.5 to less than 4.0%, with the remainder consisting of Fe and other unavoidable impurities (weight % or more) with stress corrosion cracking resistance. This is an excellent high-strength alloy for oil country tubular goods. Next, the reason why the composition range of the alloy of the present invention is limited as described above will be explained. (a) CC If the C component exceeds 0.1%, stress corrosion cracking tends to occur at grain boundaries, so the upper limit of its content was set at 0.1%. (b) Si The Si component is a necessary component as a deoxidizing component, but if its content exceeds 1.0%, hot workability and ductility will deteriorate, so the upper limit is set at 1.0%. Ta. (c) Mn As mentioned above, the Mn component not only improves stress corrosion cracking resistance when coexisting with Ni, Cr, Mo, and W, but also promotes strength improvement by cold working, and also promotes solid solution of N. However, if the content is less than 3.0%, the desired effect will not be obtained, while if the content exceeds 15.0%, hot workability will deteriorate. The content was set at 3.0-15.0%. (d) P The P component has the effect of increasing susceptibility to stress corrosion cracking, and this effect increases as its content increases.
Since it appears significantly when it exceeds 0.030%, the upper limit was set at 0.030%. (e) S The S component has the effect of deteriorating the hot workability of the alloy, and this effect occurs when its content is 0.010
%, the upper limit of the content was set at 0.010%. (f) sol.Al Al, like Si, is an effective component as a deoxidizing component, and even if it is included up to 0.5% in sol.Al content, it will not impair the alloy properties in any way. The upper limit was set at 0.5% for sol.Al. (g) Cr The Cr component has the effect of significantly improving stress corrosion cracking resistance when coexisting with Mn, Ni, Mo, and W components, but if its content is less than 18.0%, the desired excellent stress resistance is not achieved. Corrosion cracking resistance cannot be ensured, and even if the content exceeds 22.5%,
In H ₂ S−CO ₂ −Cl ⁻ oil well environments at temperatures below 150°C, further improvement effects may not appear and hot workability may deteriorate, so the content should be kept at less than 18.0 to 22.5%. Established. (h) Ni The Ni component has the effect of improving the stress corrosion cracking resistance of the alloy, but if its content is less than 15.0%, the desired excellent stress corrosion cracking resistance cannot be secured, and the structure On the other hand, even if the content exceeds 40.0%, there will be no further improvement in stress corrosion cracking resistance. was set at 15.0% to 40.0%. (i) N The N component has the effect of improving the alloy structure and strengthening it by forming a solid solution in the base material, but if its content is less than 0.1%, the desired effect cannot be obtained. On the other hand, if it exceeds 0.4%, it becomes difficult to melt the alloy and make ingots, so the content was set at 0.1 to 0.4%. (j) Mo and W As mentioned above, these components include Mn, Cr,
There is a uniform effect of improving stress corrosion cracking resistance in coexistence with Ni and Ni, but each
Even if Mo: 4.0% or more and W: 8.0% or more are contained, further improvement effects will not appear, especially in the H ₂ S−CO ₂ −Cl ⁻ oil well environment below 150°C. , its content Mo: 4.0
% and W: less than 8.0%, respectively. (k) Co The Co component not only strengthens the base material by forming a solid solution therein, but also promotes work strengthening and improves the stress corrosion cracking resistance of the alloy. It is contained as needed when required, but if the content is less than 0.05%, the desired effect of improving the above-mentioned function cannot be obtained. However, since Co is expensive, its content was set at 0.05 to 3.0% in consideration of economic efficiency. (l) Cu The Cu component has the effect of improving the strength and corrosion resistance of the alloy, so it is included as necessary when these properties are particularly required.
If the content is less than 0.05%, the desired effect of improving the above action will not appear, while if the content exceeds 3.0%, the hot workability of the alloy will deteriorate. %. (m) Rare earth elements, Y, Mg, Ca, and Ti These components have the effect of improving hot workability, so they are included when hot working is required under particularly severe conditions. However, the content of rare earth elements: less than 0.001%,
Y: less than 0.001%, Mg: less than 0.001%, Ca:
When less than 0.001% and Ti: less than 0.005%, the desired hot workability improvement effect cannot be obtained; on the other hand, rare earth elements: 0.10%, Y: 0.20%, Mg: 0.10%,
If the content exceeds Ca: 0.10% and Ti: 0.50%, the hot workability improvement effect of Setsukuri will tend to deteriorate.
The content of each rare earth element: 0.001~
0.10%, Y: 0.001~0.20%, Mg: 0.001~0.10
%, Ca: 0.001~0.10%, and Ti: 0.005~
It was set at 0.50%. (n) 1/2Mn (%) + Ni (%) and Cr (%) + Mo (%) + 1/2W (%) Figure 1 shows the results under a severe corrosive environment, namely H ₂ S
-CO ₂ -Cl ^- Regarding stress corrosion cracking resistance in an environment equivalent to an oil well environment, Cr (%) + Mo (%) +
It shows the relationship between 1/2W (%) and 1/2Mn (%)+Ni (%). Namely, Mn, Cr, Ni,
Fe− with various Mo and W contents
Mn-Cr-Ni-Mo system, Fe-Mn-Cr-Ni-W
and Fe-Mn-Cr-Ni-Mo-W alloys are melted, cast, forged and hot-rolled to form a hot-rolled sheet with a thickness of 12 mm. After holding the temperature at 1075℃ for 30 minutes and applying water-cooling solution treatment, cold working was performed at a processing rate of 25% for the purpose of improving strength. Right angle, thickness: 2mm x
A test piece of width: 10 mm x length: 75 mm was cut out, and the yield strength (0.2
% proof stress), 5% NaCl solution saturated with H ₂ S at 5 atm pressure and CO ₂ at 10 atm pressure (temperature: 150 °C)
A stress corrosion cracking test of 960 hours of immersion in
After the test, the presence or absence of cracks in the test piece was observed. Based on these results, 1/2Mn (%) + Ni (%) and Cr (%) + Mo (%) + 1/2W (%
), the results shown in Figure 1 regarding stress corrosion cracking were obtained. In FIG. 1, ◯ marks indicate no cracks, and × marks indicate cracks. From the results shown in Figure 1, Cr
When the value of (%) + Mo (%) + 1/2W (%) is less than 20% and the value of 1/2Mn (%) + Ni (%) is less than 18%, the desired stress corrosion cracking resistance can be obtained. It is clear that this cannot be done. From the above results, in order to ensure excellent stress corrosion cracking resistance, Cr
(%) + Mo (%) + 1/2 W (%): 20% or more, 1/2 Mn (%) + Ni (%): 18% or more. (o) Mo (%) + 1/2W (%) The content of Mo and W is specified as Mo (%) + 1/2W (%) because the atomic weight of W is about twice that of Mo, and the effect If this value is less than 1.5%, the desired stress corrosion cracking resistance cannot be secured; on the other hand, if this value is 4.0% or more, Mo and W containing Even if Mo is used, the effect of further improving stress corrosion cracking resistance will not appear as described above, and the content of Mo and W will be substantially unnecessary, causing high costs and being uneconomical. (%)+
The value of 1/2W (%) was set at 1.5 to less than 4.0%. Note that even if the alloy of the present invention contains B, Sn, Pb, and Zn as other unavoidable impurities in a range of 0.05% or less, the properties of the alloy of the present invention will not be impaired in any way. In addition, when manufacturing oil country tubular goods from the alloy of this invention, first a normal electric furnace, an argon-oxygen decarburization furnace (AOD furnace), an electroslag melting furnace (ESR
After melting molten steel with a predetermined composition using a furnace, etc., and making it into a steel ingot weighing approximately 2 tons, 1050
When soaked at a temperature of ~1250℃, diameter: 150~
Blooming into a billet of 300mmφ, followed by 1050~
It is heated to a temperature of 1250℃ and made into a tube material by hot working, but in order to add strength, the wall thickness decrease rate is 30% or more in the temperature range below 1000℃, where recrystallization does not occur. It is preferable to hot-work the material into a tube material under the following conditions. The resulting tubing can be either as-hot-worked or 850-1150
The pipe material is put into practical use after being solution-treated at a temperature of °C and then subjected to cold working with a wall thickness reduction rate of 5 to 70%, preferably 10 to 50%. Yield strength (0.2% yield strength): It has a high strength of 70 Kgf/mm ² or more, and has excellent stress corrosion cracking resistance as well as ductility and toughness. Next, the alloy of the present invention will be explained using examples and comparing with comparative examples. Example After preparing molten steel having the composition shown in Table 1 by a normal melting method, it was made into a steel ingot,
This steel ingot was soaked at a temperature of 1050 to 1200°C and then hot forged to form a billet. At this time, it was observed whether or not cracks occurred in the billet for the purpose of evaluating hot workability. Then, after boring the billet
The tube is heated to a temperature of 1050 to 1200℃ and hot extruded to form a tube, and in order to add strength to this tube, it is either in the hot-processed state or 1050 to 1000℃.
The alloy of the present invention having an outer diameter of 60.3 mmφ and a wall thickness of 5 mm was obtained by cold drawing at the wall thickness reduction rate shown in Table 1 while solution-treated at a temperature of 1125°C. Tube materials 1-52, comparative alloy tube materials 1-10, and conventional alloy tube materials 1-4 were manufactured, respectively. In addition, all of Comparative Alloy Tube Materials 1 to 10 have a composition in which the content of one of the constituent components or the conditional formula (indicated with an asterisk in Table 1) is outside the scope of the present invention. The conventional alloy tube material 1 is made of SUS316, and the conventional alloy tube material 2 is made of SUS310S.
The conventional alloy tube material 3 has a composition corresponding to SUS329J1, and the conventional alloy tube material 4 has a composition corresponding to Incoloy 800. Next, a test piece with a length of 20 mm was cut out from each of the various pipe materials obtained as a result, and from this test piece, a part corresponding to a central angle of 60° was cut along the length direction, and the test piece in this state was cut out. As shown in the front view in Figure 3, a bolt is passed through the tube and tightened with a nut to apply a tensile stress equivalent to the yield strength (0.2% yield strength) to the outer surface of the tube, and the test specimen S in this state is and H ₂ S at 0.1 atm, 1 atm, and
3 containing CO ₂ at 10 atm.
Seed _H2S -5% NaCl solution containing _CO2 (solution temperature: 150
A stress corrosion cracking test was carried out by immersing the specimens in a 960-hour bath (°C), and the presence or absence of stress corrosion cracking after the test was observed. These results are shown in Table 2 along with the presence or absence of cracking during hot forging, yield strength (0.2% yield strength), and elongation. In addition, in Table 2, ○ marks indicate no cracks.

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[Table] In the case, the x mark indicates the case where cracking occurred. From the results shown in Table 2, comparative alloy tube materials 1 to
No. 10 is inferior in at least one of hot workability, stress corrosion cracking resistance, and strength, while alloy tube materials 1 to 52 of the present invention are
Both have high strength and ductility, as well as excellent hot workability and stress corrosion cracking resistance, particularly under severe corrosion conditions of 10 atm H ₂ S - 10 atm CO ₂ -5%.
There was no cracking even in the NaCl solution, and it is clear that the pipe materials have even better properties than conventional alloy tube materials 1 to 4, which have relatively poor stress corrosion cracking resistance. As mentioned above, the alloy of the present invention has particularly high strength and excellent stress corrosion cracking resistance, so it can be used 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 drawings] Figure 1 shows the relationship between 1/2 Mn (%) + Ni (%) and Cr (%) + Mo (%) + 1/2 W (%) regarding the stress corrosion cracking resistance of alloys. The figures shown, FIG. 2 and FIG. 3 are front views showing aspects of stress corrosion cracking tests using plate-like and tubular test pieces, respectively.

Claims (1)

[Claims] 1 C: 0.1% or less, Si: 1.0% or less, Mn: 3.0 to 15.0%, P: 0.030% or less, S: 0.010% or less, sol.Al: 0.5% or less, Cr: 18.0 to Contains less than 22.5%, Ni: 15.0 to 40.0%, N: 0.1 to 0.4%, Mo: less than 4.0%, W: less than 8.0%, Contains one or two of the following, and 1 /2Mn (%) + Ni (%): 18% or more, Cr (%) + Mo (%) + 1/2W (%): 20% or more, Mo (%) + 1/2W (%): 1.5 to less than 4.0%, A high-strength alloy for oil country tubular goods with excellent corrosion resistance that satisfies the above requirements and has a composition (at least % by weight) consisting of Fe and other unavoidable impurities. 2 C: 0.1% or less, Si: 1.0% or less, Mn: 3.0 to 15.0%, P: 0.030% or less, S: 0.010% or less, sol.Al: 0.5% or less, Cr: 18.0 to less than 22.5%, Ni: Contains 15.0 to 40.0%, N: 0.1 to 0.4%, Mo: less than 4.0%, W: less than 8.0%, one or two of the following, and further Co: 0.05 to 3.0%. Contains, and 1/2Mn (%) + Ni (%): 18% or more, Cr (%) + Mo (%) + 1/2W (%): 20% or more, Mo (%) + 1/2W (%): A high-strength alloy for oil country tubular goods with excellent corrosion resistance, which satisfies the following: 1.5 to less than 4.0%, and has a composition (at least % by weight) of Fe and other unavoidable impurities. 3 C: 0.1% or less, Si: 1.0% or less, Mn: 3.0 to 15.0%, P: 0.030% or less, S: 0.010% or less, sol.Al: 0.5% or less, Cr: 18.0 to less than 22.5%, Ni: Contains 15.0 to 40.0%, N: 0.1 to 0.4%, Mo: less than 4.0%, W: less than 8.0%, one or two of the following, Cu: 0.05 to 3.0%, and 1/2Mn (%) + Ni (%): 18% or more, Cr (%) + Mo (%) + 1/2W (%): 20% or more, Mo (%) + 1/2W (%) : A high-strength alloy for oil country tubular goods with excellent corrosion resistance, which satisfies the following: 1.5% to less than 4.0%, with the remainder consisting of Fe and other unavoidable impurities (at least % by weight). 4 C: 0.1% or less, Si: 1.0% or less, Mn: 3.0 to 15.0%, P: 0.030% or less, S: 0.010% or less, sol.Al: 0.5% or less, Cr: 18.0 to less than 22.5%, Ni: Contains 15.0 to 40.0%, N: 0.1 to 0.4%, Mo: less than 4.0%, W: less than 8.0%, one or two of the following, and rare earth elements: 0.001 to 0.10%. , Y: 0.001-0.20%, Mg: 0.001-0.10%, Ca: 0.001-0.10%, Ti: 0.005-0.50%, contains one or more of the following, and 1/2 Mn (% ) + Ni (%): 18% or more, Cr (%) + Mo (%) + 1/2W (%): 20% or more, Mo (%) + 1/2W (%): 1.5 to less than 4.0%, A high-strength alloy for oil country tubular goods with excellent corrosion resistance, characterized by having a composition (at least % by weight) of Fe and other unavoidable impurities. 5 C: 0.1% or less, Si: 1.0% or less, Mn: 3.0 to 15.0%, P: 0.030% or less, S: 0.010% or less, sol.Al: 0.5% or less, Cr: 18.0 to less than 22.5%, Ni: Contains 15.0 to 40.0%, N: 0.1 to 0.4%, Mo: less than 4.0%, W: less than 8.0%, one or two of the following, furthermore, Co: 0.05 to 3.0%, Contains Cu: 0.05 to 3.0%, and 1/2Mn (%) + Ni (%): 18% or more, Cr (%) + Mo (%) + 1/2W (%): 20% or more, Mo (%) ) + 1/2W (%): 1.5 to less than 4.0%, a high strength alloy for oil country tubular goods with excellent corrosion resistance, characterized by having a composition (by weight %) with the remainder consisting of Fe and other unavoidable impurities. . 6 C: 0.1% or less, Si: 1.0% or less, Mn: 3.0 to 15.0%, P: 0.030% or less, S: 0.010% or less, sol.Al: 0.5% or less, Cr: 18.0 to less than 22.5%, Ni: Contains 15.0 to 40.0%, N: 0.1 to 0.4%, Mo: less than 4.0%, W: less than 8.0%, one or two of the following, and rare earth elements: 0.001 to 0.10%. , Y: 0.001-0.20%, Mg: 0.001-0.10%, Ca: 0.001-0.10%, Ti: 0.005-0.50%, and Co: 0.05-3.0%. , and 1/2Mn (%) + Ni (%): 18% or more, Cr (%) + Mo (%) + 1/2W (%): 20% or more, Mo (%) + 1/2W (%): 1.5 ~ A high-strength alloy for oil country tubular goods with excellent corrosion resistance, which satisfies the following: less than 4.0%, with the remainder consisting of Fe and other unavoidable impurities (at least 4.0% by weight). 7 C: 0.1% or less, Si: 1.0% or less, Mn: 3.0 to 15.0%, P: 0.030% or less, S: 0.010% or less, sol.Al: 0.5% or less, Cr: 18.0 to less than 22.5%, Ni: Contains 15.0 to 40.0%, N: 0.1 to 0.4%, Mo: less than 4.0%, W: less than 8.0%, one or two of the following, and rare earth elements: 0.001 to 0.10%. , Y: 0.001-0.20%, Mg: 0.001-0.10%, Ca: 0.001-0.10%, Ti: 0.005-0.50%, and Cu: 0.05-3.0%. , and 1/2Mn (%) + Ni (%): 18% or more, Cr (%) + Mo (%) + 1/2W (%): 20% or more, Mo (%) + 1/2W (%): 1.5 ~ A high-strength alloy for oil country tubular goods with excellent corrosion resistance, which satisfies the following: less than 4.0%, with the remainder consisting of Fe and other unavoidable impurities (at least 4.0% by weight). 8 C: 0.1% or less, Si: 1.0% or less, Mn: 3.0 to 15.0%, P: 0.030% or less, S: 0.010% or less, sol.Al: 0.5% or less, Cr: 18.0 to less than 22.5%, Ni: Contains 15.0 to 40.0%, N: 0.1 to 0.4%, Mo: less than 4.0%, W: less than 8.0%, contains one or two of the following, and rare earth elements: 0.001 to 0.10%. , Y: 0.001-0.20%, Mg: 0.001-0.10%, Ca: 0.001-0.10%, Ti: 0.005-0.50%, and one or more of the following, Co: 0.05-3.0%, Cu: 0.05 ~3.0%, and 1/2Mn (%) + Ni (%): 18% or more, Cr (%) + Mo (%) + 1/2W (%): 20% or more, Mo (%) + 1/2 2W (%): 1.5 to less than 4.0% A high-strength alloy for oil country tubular goods with excellent corrosion resistance, characterized by having a composition (by weight) with the remainder consisting of Fe and other unavoidable impurities.