CN118241025A - Production method of 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing pipe - Google Patents
Production method of 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing pipe Download PDFInfo
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Abstract
The invention relates to a production method of a 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing pipe, which comprises the following steps of: after reducing the diameter by tension, adopting twice quenching and once tempering heat treatment; the first quenching adopts on-line quenching or off-line quenching, and the second quenching adopts off-line quenching; in the first quenching, the online quenching temperature is not lower than 825 ℃, and the offline quenching temperature is 825-855 ℃; in the second quenching, the quenching temperature is 825-855 ℃; tempering is carried out after two times of quenching, and the tempering temperature is 540-640 ℃. The invention aims to produce the ultra-high strength seamless pipe with the yield strength not lower than 160ksi and excellent low-temperature toughness, and the oil casing has better low-temperature toughness, lower ductile-brittle transition temperature and higher mechanical strength, and meets the requirements of low-temperature resistance, high strength and high toughness of the oil casing in the process of exploiting an oil field at low temperature.
Description
Technical Field
The invention relates to the technical field of manufacturing of ultra-high strength low temperature resistant structural steel, in particular to a production method of a 160 ksi-grade high-strength and high-toughness low temperature resistant nonstandard oil sleeve.
Background
Oil and natural gas are energy struts for social development, china is in a high-speed development period, and the increase of the oil and natural gas exploration and exploitation activities are brought about by the increase of energy demands and price. The oil well pipe is one of the necessary equipment in petroleum and natural gas development engineering and is a special material. Typically, 20% -30% of the cost of a well is the cost of an oil well pipe. In the total amount of steel for petroleum industry, the oil well pipe accounts for 40%, and the oil well pipe accounts for more than 90%. The oil sleeve has huge amount of oil sleeve and wide market prospect.
At present, shallow oil and gas resources easy to be adopted are gradually exhausted, the depth of an oil and gas well is promoted to be gradually increased, the well depth is accelerated year by year, and the exploitation of the oil and gas field is increasingly frequent to high-altitude, polar, deep and deep sea areas. After the well depth is increased, the pressure in the well is continuously increased, the geological environment is more severe, and the stressed state of the oil casing is more complex and severe. The oil-gas field is located remotely, especially the oil well pipe operated in extremely cold environment needs to bear high-strength load of hundreds or thousands of atmospheres, and brittle fracture in low-temperature environment, service condition and rigor are avoided. Service conditions such as large well depth, extremely low temperature and the like provide a severe problem of toughness matching for the oil well pipe.
The highest Q125 steel grade of the prior API oil casing can not meet the requirements, and the safe operation of deep wells and ultra-deep wells is urgently required to be provided with the high-toughness oil and gas exploitation steel with the grade of 160ksi or more. Along with the increase of the strength, the existing seamless pipe with the strength exceeding the Q125 steel grade has various problems in composition or preparation process, and although the yield strength of the existing product can reach 160ksi requirements, the technical schemes still have the defects of high content of added alloy elements, complex production process, poor toughness matching and the like, and are difficult to meet the development requirements of low-temperature oil wells. At present, the use environment of low-temperature/ultralow-temperature oil well pipes developed in Russian and French is below-60 ℃, and the development of various oil well pipe materials for low-temperature and ultralow-temperature environments has not been developed in China. Therefore, development of a key low-temperature resistant material for development equipment of environmental oil and gas resources such as polar regions is needed.
The invention document No. CN200910070052.5 discloses a steel pipe with strength of 1034-1172MPa and ductile-brittle transition temperature of-40 to-80 ℃ and transverse impact energy of 50-80J and longitudinal impact energy of 80-120J. In the aspect of component design, 0.01 to 0.85 percent of W element and 0.001 to 0.005 percent of B element are added, and the obvious difference is achieved compared with the scheme that W, B elements are not added. In the production process, the quenching furnace heating temperature is 860-920 ℃, the heat preservation time is 45-70min, the tempering furnace heating temperature is 600-650 ℃, the heat preservation time is 60-90min, and the temperature is obviously different from the quenching furnace heating temperature of the quenching furnace of the invention below 860 ℃, the heat preservation time is below 45min and the tempering heat preservation time is below 50 min.
The invention document CN201810234656.8 discloses a low-temperature-resistant high-toughness oil sleeve and a manufacturing method thereof, wherein the yield strength of the steel pipe is more than or equal to 965MPa, the ductile-brittle transition temperature is between minus 60 ℃ and minus 100 ℃, and the transverse impact energy is more than or equal to 100J and the longitudinal impact energy is more than or equal to 120J. In the aspect of component design, a low-carbon strategy is adopted, and only 0.08 to 0.14 percent of C element is added, so that the obvious difference is achieved between the low-carbon strategy and the addition of not less than 0.15 percent of C element. In the production process, the austenitizing temperature is controlled at 900-930 ℃ and the tempering heat preservation time is 50-80min during heat treatment, and the austenitizing temperature is obviously different from the heating temperature of the quenching furnace of the invention below 860 ℃ and the tempering heat preservation time below 50 min.
In summary, in the prior art, some component systems are medium carbon systems, which have a high ductile-brittle transition temperature and a low toughness at this temperature; some of the alloy contains higher Ni element, so that the cost is higher; the process temperature is high, and the production process cost is high. The invention adopts the traditional solid round billet to produce 160 ksi-grade seamless pipe products by properly improving Mn content and strictly controlling Cu and Ni element content ranges, and overcomes the defects of the prior art scheme. Through reasonable component design and preparation process optimization matching, a brand new technical scheme is provided for material selection in the field of ultra-high strength and toughness seamless pipes.
Disclosure of Invention
The invention aims to provide a production method of a 160 ksi-grade high-toughness low-temperature-resistant nonstandard oil casing pipe, which is used for producing an ultrahigh-strength seamless pipe with yield strength not lower than 160ksi and excellent low-temperature toughness, wherein the oil casing pipe has better low-temperature toughness, lower ductile-brittle transition temperature and higher mechanical strength, and meets the requirements of low-temperature-resistant high-strength high-toughness performance of the oil casing pipe in the process of low-temperature exploitation of oil fields.
In order to achieve the above purpose, the invention adopts the following technical scheme:
The invention relates to a seamless pipe with yield strength not lower than 160ksi grade and a manufacturing method thereof, which comprises the processes of steelmaking, refining, casting, rolling, cooling and heat treatment, can meet the material selection requirement in the field of high-strength seamless pipes which are allowed to be supplied in a quenched and tempered state, and is suitable for producing seamless pipe products such as deep wells, ultra-deep well oil pipes, oil casings, pipe hoops and the like used in cold environments.
A production method of a 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing pipe comprises the following process paths: steel billet smelting and continuous casting, steel pipe rolling and tempering, and specifically comprises the following steps:
1) Smelting and continuously casting steel billets: molten iron is smelted by an electric furnace, sent into an LF furnace for refining, fed with Al wires, and subjected to vacuum treatment by a VD furnace and then continuously cast into round tube blanks.
2) Rolling a steel pipe: the round tube blank is heated to 1100-1200 ℃ (T 1), the total time length of the round tube blank in the furnace is not more than 4h (T 1), the temperature before perforation is 1080-1180 ℃ (T 2), the temperature before oblique rolling is 980-1100 ℃ (T 3), and the temperature before tension reducing is 850-920 ℃ (T 4).
3) Quenching and tempering: after reducing the diameter by tension, adopting twice quenching and once tempering heat treatment; the quenching medium is water or oil or any other cooling medium with equivalent cooling strength, and the first quenching temperature can be higher than, equal to or lower than the second quenching temperature; in the first quenching, online quenching or offline quenching can be adopted, and the online quenching is performed after the tension reducing; offline quenching is adopted for the second quenching; when in first quenching, the online quenching temperature is not lower than 825 ℃ (T 5), the offline quenching temperature is 825-855 ℃ (T 6), and the first offline quenching austenite heat preservation time is T 2-1; in the second quenching, the quenching temperature is 825-855 ℃ (T 7), and the second off-line quenching austenite heat preservation time is T 2-2; the same quenching temperature and holding time are recommended for both quenching.
The austenitizing heat preservation time of single off-line quenching is calculated according to t X (1-2) min/mm, wherein t is the wall thickness of the steel pipe, the unit mm, the calculated time is less than 15min, and the heat preservation is performed according to 15 min.
Tempering after finishing the quenching twice; when tempering, the tempering temperature is 540-640 ℃ (T 8), the tempering heat preservation time (T 3) is calculated according to t× (1-3) min/mm, wherein T is the wall thickness of the steel pipe, the calculated time is less than 15min, the heat preservation is performed according to 15min, and the calculated time is more than 50min, and the heat preservation is performed according to 50 min.
The oil sleeve comprises the following chemical components in percentage by weight of ：C 0.21％～0.29％、Si 0.05％～0.35％、Mn 0.65％～0.95％、Cr 0.65％～0.95％、Mo 0.65％～0.95％、V 0.02％～0.12％、Nb≤0.05％、Ni 0.65％～0.95％、Al≤0.05％、Ti≤0.05％、N≤0.005％、P≤0.015％、S≤0.005％, and the balance of Fe and unavoidable impurity elements.
The main alloying elements of the invention are as follows:
Carbon C: c is the main element next to Fe in steel, and directly affects the strength, plasticity, toughness and other properties of the steel. C has obvious effect on improving the strength of steel through solid solution strengthening and precipitation strengthening, but improving the content of C has negative effect on the plasticity and toughness of the steel. For this purpose, the C content is set to 0.21 to 0.29%.
Silicon Si: si is an important reducing agent and deoxidizer in the steelmaking process, and can be dissolved in ferrite and austenite to improve the hardness and strength of steel. By increasing the Si content, the precipitation tendency of Fe 3 C can be reduced. The Si content is too high, which obviously reduces the plasticity and toughness of the steel. For this purpose, the Si content is set to a range of 0.05 to 0.35%.
Manganese Mn: mn can improve the hardenability of steel, and is beneficial to the strength of steel; can eliminate the influence of S (sulfur) and improve the hot workability of steel. Because Mn is relatively cheap and can be infinitely dissolved with Fe, the strength of the steel is improved, and meanwhile, the influence on plasticity is relatively small. Therefore, mn is widely used as a strengthening element in steel. The excessive Mn content can aggravate the segregation of the continuous casting billet, increase the band-shaped structure grade of the steel pipe, and deteriorate the structure uniformity, and is unfavorable for the plasticity and the low-temperature toughness of the steel pipe. For this purpose, the Mn content is set to 0.65 to 0.95%.
Chromium Cr: cr can increase the hardenability of steel and has a secondary hardening effect, and can improve the strength, hardness and wear resistance of steel without embrittling the steel, but can reduce elongation and reduction of area. Cr has the main function of improving hardenability in a quenching and tempering structure, so that the steel has good comprehensive mechanical properties after quenching and tempering. If Cr is excessively added, cr-containing carbide is precipitated and aggregated at the prior austenite grain boundary in the tempering process to grow up, and the low-temperature toughness of the steel pipe is seriously damaged. The Cr content range is selected to be 0.65-0.95%.
Molybdenum Mo: mo has similar effects, and the addition amount is not excessively high because of the high price. Mo tends to form M2C carbides, which are finer in size and have higher thermal stability than Cr. In addition, by adding Mo element, precipitation of V element can be effectively promoted, and the precipitation strengthening effect of V can be improved. The Mo content range selected by the invention is 0.65-0.95%.
Vanadium V: v and C, N, O have a very strong affinity with which the corresponding stable compounds are formed. V exists mainly in the form of carbide in steel, and has the functions of refining structure and crystal grains, improving strength and toughness and reducing overheat sensitivity. Vanadium can increase the tempering stability of quenched steel and produce a secondary hardening effect; the main purpose of quenched and tempered steel is to improve the strength of the steel. The V content range is selected to be 0.02-0.12%.
Titanium Ti, nitrogen N: ti and C, N, O have extremely strong affinity, and form corresponding stable compounds with the Ti and C, N, O, which are one of the most main solid N elements. The precipitated phase containing Ti has strong binding force, is stable and not easy to decompose, can prevent the grain growth tendency of steel at high temperature and improve the welding performance of the steel. The N and the S are fixed by Ti, which is beneficial to improving the strength and the plasticity of the steel. Increasing the Ti content, the Ti-containing precipitate phase coarsens, adversely affecting performance. The Ti in the invention has the core function of fixing N, and avoiding the combination of N and V from affecting the cooperative precipitation of V and Mo. The invention selects Ti content not higher than 0.05% and N content not higher than 0.005%.
Niobium Nb: nb is one of the most main microalloying elements, and is partially dissolved into solid solution to play a role in solid solution strengthening; when the carbide, nitride and oxide particles exist, the tempering stability of the steel can be improved, and the secondary hardening effect is realized. The trace Nb can improve the strength of the steel without affecting the plasticity or toughness of the steel. The impact toughness of the steel can be improved and the brittle transition temperature of the steel can be reduced due to the effect of grain refinement. In the rolling process, the solid solution Nb obviously improves the recrystallization temperature of the steel, and can finish the rolling process of the steel in a higher temperature range, thereby reducing the internal stress of the steel pipe. The Nb content is not higher than 0.05%.
Nickel Ni: ni has the effect of stabilizing austenite and improving hardenability. The strength, toughness and corrosion resistance can be improved by adding a certain amount of Ni into the steel, and the ductile-brittle transition temperature can be reduced. Ni-containing steels are generally not prone to overheating, so that they can prevent grain growth at high temperatures and still maintain a fine grain structure. However, considering the cost, the invention selects the Ni content range of 0.65-0.95%.
Aluminum Al: al is added to steel as a deoxidizer or alloying element, and aluminum has a much stronger deoxidizing ability than silicon and manganese. The main function of aluminum in steel is to refine grains and fix nitrogen in the steel, so that the impact toughness of the steel is obviously improved, and the cold embrittlement tendency and the aging tendency are reduced; the aluminum can also improve the corrosion resistance of the steel, and particularly has better effect when being matched with elements such as molybdenum, copper, silicon, chromium and the like; the disadvantage of aluminum is that it affects the hot workability, weldability and machinability of the steel. The content range of Al is not higher than 0.05%.
Phosphorus P: p is carried into the steel by the ore and S is similarly one of the deleterious elements. P can increase the strength and hardness of steel, but causes a significant decrease in plasticity and impact toughness. Particularly, at low temperature, it makes the steel become significantly brittle, and the higher the P content, the greater the cold brittleness. Dep to a lower level can significantly increase steelmaking costs. The P content range is not higher than 0.015%.
Sulfur S: s is derived from ore and fuel coke in steelmaking, is one of the most common harmful elements in steel, and is unfavorable for ductility, toughness, weldability and corrosion resistance of the steel. If S is present in the steel in the form of FeS, it can also be thermally embrittled during hot working. The S content range is not higher than 0.005%.
The main reasons for the control range of the manufacturing process parameters are as follows:
The invention adopts the compound precipitation strengthening of Cr, mo, V, nb, ti and other elements, controls the heating temperature of the continuous casting round tube blank between 1100 ℃ and 1200 ℃, ensures that the total duration of the furnace is not more than 4 hours, ensures that the precipitation phase of the alloy element is fully dissolved back into austenite, fully plays the beneficial effects of inhibiting recrystallization, solid solution strengthening, precipitation strengthening, refining grains and the like in the subsequent process, and prepares the components and the temperature for obtaining the final tissue structure. Below the selected temperature and time range, the solid solution will be insufficient, affecting the final steel pipe strength; above the selected time and temperature range, the original austenite grains of the continuous casting slab are easy to be too coarse, which is not beneficial to the control of the toughness of the steel pipe.
The steel pipe can be directly quenched on line after rolling, or quenched after offline reheating. The production process is properly controlled, so that the temperature of the reduced pipe meets the quenching requirement, the direct on-line quenching is easy to realize, the energy is saved, the production cost is reduced, the reheating process is reduced, the production efficiency is improved, and the economic benefit is remarkable.
After the accelerated cooling of the steel pipe is finished, tempering heat treatment is carried out, the tempering heat preservation temperature is higher than 640 ℃, the strength of the steel pipe is obviously reduced, and the final toughness of the steel pipe is not matched; but below 540 ℃, the quenching structure is insufficiently tempered, and the low-temperature toughness is low. Tempering and heat preserving time is excessively long and exceeds 50min, so that the strength is poor; the tempering and heat preserving time is too short and is lower than 15min, and the toughness is insufficient. Proper tempering temperature, tempering heat preservation time and control of the contents of Mo, V and Ti which are key alloying elements ensure that the beneficial precipitated phase is fully precipitated and has small size, and the size of the precipitated phase of more than 90 percent is not more than 20nm. Therefore, the method achieves the characteristics of good toughness matching and good performance stability under a wider hardening and tempering process window.
The yield strength R t0.7 is more than or equal to 1100MPa, the tensile strength R m is more than or equal to 1200MPa, the elongation A is more than or equal to 15%, and the transverse and longitudinal Charpy impact A kv at-60 ℃ is not lower than 150J and 180J respectively.
Compared with the prior art, the invention has the beneficial effects that:
1) The rolling temperature and the deformation amount are not required to be controlled in the steel pipe rolling process, the quenching temperature is only required to be met before the tension reducing, and the high-temperature rolling is matched with the direct on-line quenching, so that secondary heating is not required, the energy is saved, and the production efficiency is improved; by adopting the off-line quenching process, the steel pipe is subjected to re-austenitizing, and the toughening matching effect can be further improved.
2) The adoption of two times of quenching is favorable for obtaining fine austenite grains, and the adverse effect of the coarse pearlite structure obtained by air cooling after hot rolling on toughness is thoroughly eliminated; the adoption of twice tempering and the guarantee of unchanged total tempering time can promote the increase of the quantity of precipitated phases and inhibit the growth of the precipitated phases.
3) Mo is adopted instead of N element to promote effective precipitation of V element. Compared with V (C, N), the (Mo, V) C has higher thermal stability and more spherical shape, and can realize more stable obdurability matching effect in a wider heat treatment process parameter range.
4) The yield strength R t0.7 of the steel pipe manufactured by the invention is more than or equal to 1100MPa, the tensile strength R m is more than or equal to 1200MPa, the elongation A is more than or equal to 15%, and the transverse and longitudinal Charpy impact A kv at-60 ℃ is respectively not lower than 150J and 180J.
Detailed Description
The technical scheme of the present invention will be clearly and completely described in the following in connection with examples. The following examples are given to illustrate the present invention in detail, but are merely a general description of the present invention and are not intended to limit the present invention.
Table 1 shows the chemical composition of the steel according to the example of the invention; tables 2 and 3 show the rolling and heat treatment process parameters and mechanical properties of the steels according to the examples of the present invention.
TABLE 1 chemical composition wt% of the steel pipes according to the examples of the present invention
Note that: * Representative levels are calculated in ppm.
TABLE 2 Rolling and quenching Process parameters of the Steel pipe according to the embodiment of the invention
TABLE 3 tempering process parameters and mechanical properties of the inventive example steel pipes
As can be seen from the data in tables 1,2 and 3, the technical scheme adopted by the invention is that the yield strength of the prepared steel pipe is more than or equal to 1110MPa, the tensile strength is more than or equal to 1200MPa, the elongation is more than or equal to 15%, and the transverse and longitudinal Charpy impact energies at minus 60 ℃ are respectively not lower than 150J and 180J, so that the steel pipe has excellent toughness matching.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (7)
1. A production method of a 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing pipe comprises the following process paths: the steel billet smelting and continuous casting, steel pipe rolling and tempering are characterized in that the tempering process comprises the following steps:
After reducing the diameter by tension, adopting twice quenching and once tempering heat treatment; the first quenching adopts on-line quenching or off-line quenching, and the second quenching adopts off-line quenching; in the first quenching, the online quenching temperature is not lower than 825 ℃, and the offline quenching temperature is 825-855 ℃; in the second quenching, the quenching temperature is 825-855 ℃; tempering is carried out after two times of quenching, and the tempering temperature is 540-640 ℃.
2. The method for producing 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing pipe according to claim 1, wherein the billet smelting and continuous casting procedures comprise: molten iron is smelted by an electric furnace, sent into an LF furnace for refining, fed with Al wires, and subjected to vacuum treatment by a VD furnace and then continuously cast into round tube blanks.
3. The method for producing 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing pipe according to claim 1, wherein the steel pipe rolling process comprises the following steps: the round tube blank is heated to 1100-1200 ℃, the total time length of the round tube blank in the furnace is not more than 4 hours, the temperature before perforation is 1080-1180 ℃, the temperature before oblique rolling is 980-1100 ℃, and the temperature before tension reducing is 850-920 ℃.
4. The method for producing 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing pipe according to claim 1, wherein in the quenching process, the single off-line quenching austenitizing heat preservation time is as follows: t× (1-2) min/mm, wherein: t is the wall thickness of the steel pipe, and the unit is mm; the calculation time is less than 15min, and the temperature is kept for 15 min.
5. The method for producing 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing pipe according to claim 1, wherein the tempering and heat-preserving time is as follows: t is calculated by (1-3) min/mm, wherein t is the wall thickness of the steel pipe and is expressed in mm; keeping the temperature for 15min when the calculation time is less than 15min, and keeping the temperature for 50min when the calculation time is more than 50 min.
6. An oil casing prepared by the method for producing 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing according to any one of claims 1 to 5, wherein the oil casing comprises the following chemical components in percentage by weight, wherein the balance is ：C 0.21％～0.29％、Si 0.05％～0.35％、Mn 0.65％～0.95％、Cr 0.65％～0.95％、Mo 0.65％～0.95％、V 0.02％～0.12％、Nb≤0.05％、Ni 0.65％～0.95％、Al≤0.05％、Ti≤0.05％、N≤0.005％、P≤0.015％、S≤0.005％, of Fe and unavoidable impurity elements.
7. The oil casing prepared by the production method of 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing according to claim 6, wherein the yield strength R t0.7 is more than or equal to 1100MPa, the tensile strength R m is more than or equal to 1200MPa, the elongation A is more than or equal to 15%, and the transverse and longitudinal Charpy impact A kv at-60 ℃ is respectively not lower than 150J and 180J.
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| CN202410338153.0A CN118241025A (en) | 2024-03-25 | 2024-03-25 | Production method of 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing pipe |
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| CN202410338153.0A CN118241025A (en) | 2024-03-25 | 2024-03-25 | Production method of 160 ksi-grade high-strength and high-toughness low-temperature-resistant nonstandard oil casing pipe |
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