CN114318123A - High-strength low-hardness low-cost 13Cr oil casing steel, oil casing and manufacturing method thereof - Google Patents
High-strength low-hardness low-cost 13Cr oil casing steel, oil casing and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses a high-strength low-hardness low-cost 13Cr oil casing steel, which comprises the following chemical elements in percentage by mass in addition to Fe and inevitable impurities: c is more than 0 and less than or equal to 0.04 percent, Si is more than 0 and less than or equal to 0.5 percent, Mn: 0.2-1.0%, Cr: 11-14%, Mo: 1-3%, Ni: 4-7%, Ti: 0.01-0.05%, N: 0.001-0.015%; and the chemical composition also satisfies: ti is more than or equal to (C + N), wherein C, Ti and N respectively represent the mass percentage content of corresponding elements. In addition, the invention also discloses a high-strength low-hardness low-cost 13Cr oil casing which is prepared from the high-strength low-hardness low-cost 13Cr oil casing steel. In addition, the invention also discloses a manufacturing method of the 13Cr oil casing pipe with high strength, low hardness and low cost. The 13Cr oil casing steel with high strength, low hardness and low cost can obtain high strength and low hardness on the premise of reducing cost.
Description
Technical Field
The invention relates to steel, an oil casing and a manufacturing method thereof, in particular to the steel for a 13Cr oil casing, the oil casing and the manufacturing method thereof.
Background
In recent years, with the increase of social energy demand and the progress of drilling and completion technologies, natural gas production is developing from conventional working conditions to 'three-super' (ultra-deep, ultra-high pressure, ultra-high temperature) working conditions. The 'three-super' gas well of the Tarim oil field gradually becomes an important growth point of the recoverable reserves of the oil and gas field in China due to the single-well output, and has important significance for guaranteeing the long-term stable gas supply of the western gas and the east gas.
However, it is noted that highly corrosive well flow media, particularly CO, are prevalent in "three super" gas wells of Tarim oil fields2The maximum partial pressure of gas reaches 4 MPa. So that it is resistant to CO2The corroded super 13Cr oil casing is widely applied to the 'three-super' of Tarim oil fields.
Therefore, the quality level of the super 13Cr oil casing pipe determines whether the high-temperature and high-pressure oil and gas wells can be developed smoothly, and is very important for developing the three-super (ultra-deep, ultra-high pressure and ultra-high temperature) oil and gas wells of the Tarim oil field in China.
The prior art has problems even though the super 13Cr oil casing pipe is available.
For example: chinese patent publication No. CN101397637A, published as 2009, 4.1.a, entitled "steel for oil casing pipe with high resistance to carbon dioxide and trace hydrogen sulfide corrosion by 13Cr and method for manufacturing same", discloses a steel for super 13Cr oil casing pipe and method for manufacturing same. According to the steel, Cu and Nb are added on the basis of Cr, Ni and Mo in a compounding manner, the hardness is higher after the steel reaches 110ksi after heat treatment, and stress corrosion cracking failure is easy to occur in an underground corrosion environment after an oil field is put into a well. The manufacturing method of the patent comprises electric furnace smelting, die casting, pipe blank forging, pipe blank annealing, pipe blank heating, perforation, hot rolling and heat treatment.
Another example is: chinese patent document CN102172626A, published as 2011, 9, month 7 and entitled "hot rolling production method of phi 48-89mm super 13Cr oil pipe", discloses a hot rolling production method of phi 48-89mm super 13Cr oil pipe. This patent does not relate to a specific method for manufacturing super 13Cr material and tube blank. The manufacturing method comprises the steps of selecting super 13Cr forged pipe blanks, heating the pipe blanks, perforating, continuously rolling, reheating and reducing tension.
For another example: chinese patent publication No. CN105855293A, published as 2016, 8, 17, entitled "method for producing super 13Cr oil pipe", discloses a method for producing super 13Cr oil pipe by hot rolling. However, the patent also does not relate to a specific super 13Cr material and a method for manufacturing a tube blank, wherein the super 13Cr material is selected to be used for forging the tube blank, and the tube blank is heated, punched, continuously rolled, reheated, tensioned and straightened, and packaged.
Analysis shows that the 13Cr oil casing obtained by the prior art has high hardness while the heat treatment reaches 110-grade steel high strength, and is easy to generate stress corrosion cracking failure in a downhole corrosion environment.
In addition, in order to meet the quality requirements of the three-super oil and gas well, ultrasonic flaw detection which is far higher than the flaw detection standard required by the API standard needs to be carried out on the super 13Cr oil casing. The super 13Cr oil casing produced by the method is subjected to ultrasonic flaw detection according to a flaw detection standard far higher than the API standard requirement, and the qualification rate is only 20-30%. Meanwhile, the above patents all adopt die-cast forged tube blanks, and the die-cast procedure has very low yield and very high cost of the forging procedure.
Based on the above, in order to solve the problems in the prior art, the invention expects to obtain the steel for the 13Cr oil casing with high strength, low hardness and low cost, the oil casing and the manufacturing method thereof, the cost of the pipe blank can be greatly reduced on the premise of ensuring the quality, the super 13Cr oil casing has low hardness while the heat treatment reaches the high strength of 110 steel grade, and the stress corrosion cracking failure is not easy to occur in the underground corrosion environment after the oil field is put into the well.
Disclosure of Invention
One of the purposes of the invention is to provide the high-strength low-hardness low-cost 13Cr oil casing steel, which can obtain high strength and low hardness through reasonable chemical component design on the premise of reducing cost, has the yield strength of 758-965 MPa, the tensile strength of not less than 793MPa and the hardness of not more than 28HRC, is not easy to generate stress corrosion cracking failure in an underground corrosion environment after an oil field is put into a well, and has good popularization prospect and application value.
In order to achieve the above object, the present invention provides a high-strength, low-hardness, low-cost 13Cr oil casing steel containing, in addition to Fe and inevitable impurities, the following chemical elements in mass percent:
0＜C≤0.04％，0＜Si≤0.5％，Mn：0.2～1.0％，Cr：11～14％，Mo：1～3％，Ni：4～7％，Ti：0.01～0.05％，N：0.001～0.015％；
and the chemical composition also satisfies: ti is more than or equal to (C + N), wherein C, Ti and N respectively represent the mass percentage content of corresponding elements.
Further, in the steel for the 13Cr oil casing pipe with high strength, low hardness and low cost, the steel comprises the following chemical elements in percentage by mass:
c is more than 0 and less than or equal to 0.04 percent, Si is more than 0 and less than or equal to 0.5 percent, Mn: 0.2-1.0%, Cr: 11-14%, Mo: 1-3%, Ni: 4-7%, Ti: 0.01-0.05%, N: 0.001-0.015%; the balance being Fe and other unavoidable impurities.
In the technical scheme of the invention, reasonable chemical component design is adopted, so that high strength and low hardness are obtained on the premise of reducing cost. The high-strength low-hardness low-cost 13Cr oil casing steel does not contain elements for improving the hardness, such as Cu, Nb and the like, a Ti element which is very beneficial to reducing the hardness of the steel is specially added, C, N elements for improving the hardness of the steel are controlled, and meanwhile, Ti is more than or equal to (C + N), wherein C, Ti and N respectively represent the mass percentage content of each corresponding element.
In the high-strength low-hardness low-cost 13Cr oil casing steel of the invention, the design principle of each chemical element is as follows:
c: in the high-strength low-hardness low-cost 13Cr oil casing steel, C is an austenite forming element, and the strength of the steel can be effectively improved by increasing the content of the C element in the steel. However, it should be noted that the content of C element in the steel is not so high that the corrosion resistance of the steel is lowered and the toughness is lowered when the content of C element in the steel is too high. Based on the above, in the high-strength low-hardness low-cost 13Cr oil casing steel, the mass percent of C element is controlled to be more than 0 and less than or equal to 0.04%.
Of course, in some preferred embodiments, the mass percentage of C element can be controlled to be 0 < C.ltoreq.0.03% for better practical effects.
Si: in the high-strength low-hardness low-cost 13Cr oil casing steel, Si is an important deoxidizer in the steel-making process and can play a role in deoxidation. However, it should be noted that the content of Si element in the steel should not be too high, and too high Si may adversely affect the toughness and corrosion resistance of the steel. Therefore, in the high-strength low-hardness low-cost 13Cr oil casing steel, the mass percent of Si element is controlled to be more than 0 and less than or equal to 0.5 percent.
Mn: in the 13Cr oil casing steel with high strength, low hardness and low cost, the Mn element can effectively improve the strength of steel. However, it should be noted that the Mn content in the steel should not be too high, and when the Mn content in the steel is too high, the toughness of the steel is lowered. Therefore, in the high-strength low-hardness low-cost 13Cr oil casing steel, the mass percent of Mn element is controlled to be 0.2-1.0%.
Of course, in some preferred embodiments, the mass percentage of the Mn element may be controlled between 0.3 and 0.5% for better practical effects.
Cr: in the high-strength low-hardness low-cost 13Cr oil casing steel of the present invention, Cr is an important element for improving corrosion resistance of stainless steel, and in order to obtain sufficient CO resistance of the obtained steel2The corrosion resistance of the steel needs to be at least 11 percent. Similarly, the content of Cr in steel should not be too high, and when the content of Cr in steel is too high, the risk of ferrite precipitation is increased, which adversely affects the rolling and corrosion resistance of the product. Therefore, in the high-strength low-hardness low-cost 13Cr oil casing steel, the mass percent of Cr element is controlled to be 11-14%.
Mo: in the high-strength low-hardness low-cost 13Cr oil casing steel, Mo is an element for improving the chlorine ion pitting corrosion resistance of stainless steel. In order to obtain sufficient CO resistance of the steel produced2The corrosion capability of the steel requires that the content of Mo element in the steel at least reaches 1 percent. Meanwhile, the content of Mo in the steel is not too high, and when the content of Mo in the steel is too high, more ferrite is formed, so that the rolling and corrosion resistance of the product are adversely affected. Therefore, in the high-strength low-hardness low-cost 13Cr oil casing steel, the mass percent of Mo element is controlled to be 1-3%.
Ni: in the high-strength low-hardness low-cost 13Cr oil casing steel of the present invention, Ni element not only expands the austenite region but also improves the corrosion resistance and toughness of the steel. In order for the Ni element to sufficiently exhibit the above excellent effects, the content of the Ni element in the steel is required to be at least 4% in the present invention. Meanwhile, the cost of the Ni element is high, and the excessive Ni is not suitable to be added into the steel in consideration of the production cost. Therefore, in the high-strength low-hardness low-cost 13Cr oil casing steel, the mass percent of Ni element is controlled to be 4-7%.
Of course, in some preferred embodiments, the mass percentage of the Ni element may be controlled between 4% and 6% for better implementation.
Ti: in the high-strength low-hardness low-cost 13Cr oil casing steel, Ti is a specially added element, and is very beneficial to reducing the hardness of high-strength steel, but the steel needs to be noted that when the content of Ti in the steel is too high, the steel has great influence on the steel-making continuous casting process. Therefore, in the high-strength low-hardness low-cost 13Cr oil casing steel, the mass percent of Ti element is controlled to be 0.01-0.05%.
N: in the high-strength low-hardness low-cost 13Cr oil casing steel, N is an element for improving the pitting corrosion resistance of stainless steel, and simultaneously N can be used as an austenite forming element to improve the martensite proportion of the steel, thereby effectively improving the strength of the material. Therefore, in the high-strength low-hardness low-cost 13Cr oil casing steel, the mass percent of the N element is controlled to be 0.001-0.015%.
In addition, it should be noted that, in the steel for high-strength low-hardness low-cost 13Cr oil casing according to the present invention, while controlling the mass percentages of the single chemical elements, the present invention also needs to control: ti is more than or equal to (C + N), wherein C, Ti and N respectively represent the mass percentage content of each corresponding element. The 13Cr oil casing steel meeting the requirements of chemical components of the invention has high strength, low hardness and low cost, can reach the high strength of 110 grade steel, and simultaneously has lower hardness.
Further, in the steel for high-strength low-hardness low-cost 13Cr oil casing pipes, the mass percentage of each chemical element meets at least one of the following conditions:
0＜C≤0.03％；
Mn：0.3～0.5％；
Ni：4～6％。
further, in the high-strength low-hardness low-cost 13Cr oil casing steel according to the present invention, among other unavoidable impurities: p is less than or equal to 0.020% and/or S is less than or equal to 0.005%.
In the above technical solution of the present invention, the P and S elements are impurity elements in the steel for high strength, low hardness and low cost 13Cr oil casing according to the present invention, and the CO resistance should be reduced as much as possible to obtain a steel with better performance and better quality when the technical conditions allow2Content of impurity elements in corroded oil casing.
Furthermore, in the high-strength low-hardness low-cost 13Cr oil casing steel, the microstructure of the steel is tempered martensite and inverted austenite, wherein the volume fraction of the inverted austenite is 2-8%.
Furthermore, in the high-strength low-hardness low-cost 13Cr oil casing steel, the yield strength is 758-965 MPa, the tensile strength is not less than 793MPa, and the hardness is not more than 28 HRC.
Correspondingly, the invention also aims to provide a high-strength low-hardness low-cost 13Cr oil casing, which not only has higher strength, but also has lower hardness, the yield strength is 758-965 MPa, the tensile strength is not less than 793MPa, the hardness is not more than 28HRC, and the oil casing can be effectively applied to the well descending operation of an oil field and has good popularization prospect and application value.
In order to achieve the purpose, the invention provides a high-strength low-hardness low-cost 13Cr oil casing which is made of the high-strength low-hardness low-cost 13Cr oil casing steel.
In addition, another object of the present invention is to provide a method for manufacturing the 13Cr oil casing with high strength, low hardness and low cost, which has a simple production process and low production cost, and can greatly reduce the production cost on the premise of ensuring the quality, and the 13Cr oil casing with high strength, low hardness and low cost obtained by the method has not only higher strength but also lower hardness, and is not easy to generate stress corrosion cracking failure in a downhole corrosion environment after an oil field is put into a well, and can be effectively applied to oil field well putting operation, and thus, the method has very important practical significance.
In order to achieve the above object, the present invention provides a method for manufacturing the 13Cr oil bushing with high strength, low hardness and low cost, comprising the steps of:
(1) smelting in an electric furnace;
(2) adopting bloom continuous casting and soft reduction processes;
(3) rolling a tube blank, peeling the tube blank, heating the tube blank and perforating; wherein the annealing process is not carried out after the tube blank is rolled and before the tube blank is peeled;
(4) cold rolling;
(5) and (3) heat treatment: and (6) quenching and tempering.
In the oil jacket pipe production process, a round pipe blank is used as a raw material. The round pipe blank can be produced by adopting a die casting mode, and can also be directly produced by adopting a continuous casting mode.
Heretofore, in the prior art, a pipe blank is generally forged after die casting after electric furnace smelting. The reason why the 13Cr oil sleeves are forged after die casting is that the 13Cr oil sleeves belong to stainless steel, and compared with carbon steel, the center segregation of the casting blank is serious, and the center segregation of the tube blank can be effectively improved by adopting a forging mode after die casting. If the continuous casting mode is adopted to directly produce the round tube blank, the center of the tube blank is easy to generate internal cracking in the continuous casting process because the center segregation of the casting blank is serious. Even if the continuous casting pipe blank is subsequently forged or rolled again to improve the compression ratio, the degree of the internal crack cannot be changed. The tube blank with the internal crack is used as a raw material to produce the tube, a large amount of internal surface defects of the tube can be caused in the subsequent perforation process, the yield is extremely low, and the cost is greatly increased.
In the above technical solution of the present invention, in the step (2) of the manufacturing method of the present invention, the tube blank is manufactured by adopting a manner of bloom continuous casting and soft reduction process. In the invention, a certain pressure is applied to the solidified tail end of the casting blank by a soft reduction process, so that the center segregation of the casting blank can be effectively improved, and the inner crack is not generated in the continuous casting process. The casting blank obtained by the technical means of the invention has better center segregation, does not need to adopt an expensive forging mode to improve the center segregation, and can roll the large square blank into the round tube blank only by adopting an economic rolling mode.
Accordingly, it has been studied that the yield from molten steel to billets in die casting is about 84 to 88%, and the yield from molten steel to billets in continuous casting is about 95 to 96%. Therefore, compared with the prior art, in the step (2) of the manufacturing method, the bloom continuous casting is adopted and the soft reduction process is matched, so that the cost of the tube blank can be greatly reduced on the premise of ensuring the quality.
In addition, in order to eliminate internal stress and prevent the tube blank from generating stress cracks, and meanwhile, in order to reduce the hardness and create conditions for peeling the subsequent tube blank, in the existing manufacturing process, the tube blank of the 13Cr oil sleeve is generally required to be annealed. The annealing process not only increases the cost, but also causes the tube blank to bend. The tube blank after annealing is further subjected to a straightening process, which further increases the cost.
In the invention, the specific chemical component proportion is adopted, in the step (3), the annealing process is not carried out after the tube blank is rolled and before the tube blank is peeled, the hardness of the tube blank is equivalent to or lower than that of the tube blank annealed by the prior art, the straightening process is not required, and the cost is further reduced compared with the prior art.
Therefore, the special chemical component proportion of the high-strength low-hardness low-cost 13Cr oil casing steel is adopted, and the cost of the 13Cr oil casing pipe blank can be greatly reduced on the premise of ensuring the quality by matching with the manufacturing method of 'electric furnace smelting-bloom continuous casting-light reduction-pipe blank rolling-pipe blank peeling'.
In addition, in the prior art, rolling is generally performed by hot rolling after piercing is completed, and unlike the operation in the prior art, rolling is performed by cold rolling in step (4) of the manufacturing method according to the present invention. Although the cost of the cold rolling process is higher than that of the hot rolling process, the flaw detection qualification rate of the cold rolled tube is quite high by ultrasonic flaw detection according to the flaw detection standard far higher than the API standard requirement, and the flaw detection qualification rate of the hot rolled tube is very low by flaw detection according to the same standard, so that the total production cost is higher than that of the cold rolled tube prepared by cold rolling.
Further, in the manufacturing method of the present invention, in the step (2), the reduction amount in the soft reduction process is 5 to 15 mm.
Further, in the manufacturing method of the present invention, in the step (5), when the quenching temperature is 880 to 960 ℃ and air quenching is adopted, the subsequent tempering temperature is controlled to be 570 to 595 ℃.
Further, in the manufacturing method of the present invention, in the step (5), when the quenching temperature is 880 to 960 ℃, and oil or water quenching is employed, the subsequent tempering temperature is controlled to 600 to 650 ℃.
Compared with the prior art, the high-strength low-hardness low-cost 13Cr oil casing steel, the oil casing and the manufacturing method thereof have the following advantages and beneficial effects:
the high-strength low-hardness low-cost 13Cr oil casing steel provided by the invention can obtain high-strength and low-hardness performances on the premise of reducing cost by reasonable chemical component design and combining with an optimization process, and is not easy to generate stress corrosion cracking failure in an underground corrosion environment after an oil field is put into a well. The high-strength low-hardness low-cost 13Cr oil casing steel is low in production cost, and not only has high strength, but also has low hardness.
The yield strength of the high-strength low-hardness low-cost 13Cr oil casing steel is 758-965 MPa, the tensile strength is not less than 793MPa, and the hardness is not more than 28 HRC. The high-strength low-hardness low-cost 13Cr oil casing pipe prepared from the high-strength low-hardness low-cost 13Cr oil casing pipe steel has very excellent mechanical properties while ensuring lower production cost, can be effectively applied to well lowering operation of an oil field, and has good popularization prospect and application value.
Correspondingly, the manufacturing method provided by the invention is simple in production process and low in production cost, and can greatly reduce the production cost on the premise of ensuring the quality, the high-strength low-hardness low-cost 13Cr oil casing obtained by the manufacturing method not only has higher strength, but also has lower hardness, is not easy to generate stress corrosion cracking failure in an underground corrosion environment after an oil field is put into a well, can be effectively applied to 'three-super' (ultra-deep, ultra-high pressure and ultra-high temperature) oil and gas wells, and has important significance for ensuring long-term stable gas supply of the West-east gas transportation.
Detailed Description
The steel for high strength, low hardness, and low cost 13Cr oil casing, the oil casing, and the method of manufacturing the same according to the present invention will be further explained and illustrated with reference to specific examples, which, however, should not be construed as unduly limiting the technical aspects of the present invention.
Examples 1 to 6 and comparative example 1
The high-strength low-hardness low-cost 13Cr oil casing of the embodiments 1 to 6 of the present invention is prepared by the following steps:
(1) electric furnace smelting was carried out according to the chemical composition shown in table 1.
(2) Adopting bloom continuous casting and soft reduction processes: the reduction amount of the soft reduction process is controlled to be 5-15 mm.
(3) Rolling a tube blank, peeling the tube blank, heating the tube blank and perforating; wherein the annealing process is not carried out after the rolling of the tube blank and before the peeling of the tube blank.
(4) And (5) cold rolling.
(5) And (3) heat treatment: quenching and tempering, wherein when the quenching temperature is 880-960 ℃, and air quenching is adopted, the subsequent tempering temperature is controlled to be 570-595 ℃; and when the quenching temperature is 880-960 ℃, and oil or water quenching is adopted, the subsequent tempering temperature is controlled to be 600-650 ℃.
It should be noted that the high-strength low-hardness low-cost 13Cr oil casings of examples 1 to 6 were all produced using the steel for high-strength low-hardness low-cost 13Cr oil casings according to the present invention. The chemical composition design and related processes of the high-strength low-hardness low-cost 13Cr oil casing steel adopted in the embodiments 1 to 6 meet the design specification requirements of the invention.
Accordingly, the oil jacket pipe of comparative example 1 is completely different from the process steps of examples 1 to 6 described above, and comparative example 1 is manufactured by a method generally used in the prior art using the process steps of "electric furnace smelting, die casting, pipe blank forging, pipe blank annealing, pipe blank peeling, pipe blank heating, piercing, hot rolling, heat treatment". It is to be noted that comparative example 1 employed die casting instead of continuous casting and did not perform a soft reduction process, as compared with examples 1 to 6; in addition, comparative example 1 annealing step was performed after rolling the tube blank and after peeling the tube blank; in addition, in comparative example 1, comparative example 1 was subjected to hot rolling instead of cold rolling after completion of piercing.
The comparative oil bushing of comparative example 1 was made of a comparative steel, and the chemical composition design and related processes of the comparative steel used in comparative example 1 had parameters that did not meet the design requirements of the present invention.
Table 1 shows the mass percentages of the chemical elements of the high strength, low hardness and low cost 13Cr oil casing steel of examples 1-6 and the comparative steel of comparative example 1.
TABLE 1 (wt%, balance Fe and unavoidable impurities other than P, S)
Note: in the above table, Ti is not less than (C + N) wherein C, Ti and N respectively represent the mass percentage of the corresponding elements. Wherein, "√" represents that the mass percent content of Ti element is not less than the sum of the mass percent contents of C and N elements.
Table 2 lists the specific process parameters for the high strength, low hardness, low cost 13Cr oil casings of examples 1-6 and the comparative oil casing of comparative example 1.
Table 2.
As can be seen from Table 2, compared with comparative example 1, the bloom continuous casting and soft reduction process adopted after the electric furnace smelting in examples 1 to 6 of the present invention can effectively improve the center segregation of the casting blank, and ensure that no inner crack is generated in the continuous casting process, so as to greatly reduce the cost of the tube blank on the premise of ensuring the quality.
The obtained high-strength low-hardness low-cost 13Cr oil casings of finished examples 1 to 6 and the comparative oil casing of comparative example 1 were sampled, respectively, and observation and relevant mechanical property detection were performed, and the obtained observation results and mechanical property detection results are listed in table 3. The specific test methods and means are as follows:
(1) and (3) tensile test: tensile specimens were cut longitudinally in the axial direction of the pipe as required by ASTM A370 standard according to API SPEC 5CRA standard and run at room temperaturePerforming a tensile test to measure the tensile strength (R)m) Yield strength (R)p0.2)。
(2) Hardness test: a hardness test ring was cut from one end of the pipe according to the API SPEC 5CRA standard to perform the Rockwell hardness test. Rockwell hardness testing is performed according to ASTM E18 using Rockwell scale C (HRC).
Table 3 shows the results of mechanical property measurements of the high strength, low hardness, low cost 13Cr oil casings of examples 1-6 and the comparative oil casing of comparative example 1.
Table 3.
As can be seen from Table 3, compared with the comparative oil casing of comparative example 1, the high-strength, low-hardness and low-cost 13Cr oil casings of examples 1-6 have excellent comprehensive mechanical properties, yield strengths of 758-965 MPa, tensile strengths of 793MPa or more and hardness of 28HRC or less.
Compared with comparative example 1, the high-strength low-hardness low-cost 13Cr oil casings of examples 1-6 according to the present invention have very low hardness while achieving high strength of 110 steel grade, and are not prone to stress corrosion cracking failure in a downhole corrosive environment after being run into a well in an oil field. The hardness of comparative example 1 is very high, reaching 31.5HRC, and stress corrosion cracking failure is easy to occur in a downhole corrosion environment after the oil field is put into the well.
Accordingly, in order to examine that the high-strength, low-hardness, and low-cost 13Cr oil casings of examples 1 to 6 according to the present invention had good quality, it was necessary to further perform ultrasonic testing on the 13Cr oil casings of examples 1 to 6 according to the present invention and the comparative oil casing of comparative example 1, respectively, and the test results were set forth in table 4.
The ultrasonic flaw detection test conditions were as follows: according to the API standard, the 13Cr oil casing pipe is subjected to ultrasonic flaw detection in an L2 grade groove depth of 5 percent t in the longitudinal direction and the transverse direction. In order to meet the quality requirement of the three-super oil-gas well, 6dB needs to be tightened on the basis of the API standard flaw detection requirement, namely the ultrasonic flaw detection standard is 5% t +6dB, so that the ultrasonic flaw detection qualified rate of each embodiment and comparative example is obtained.
Table 4 lists the ultrasonic flaw detection yields of the high strength, low hardness, low cost 13Cr oil casings of examples 1-6 and the comparative oil casing of comparative example 1.
Table 4.
As can be seen from table 4, compared with the comparative oil casing of comparative example 1, the steel for the 13Cr oil casing of examples 1 to 6 of the present invention has significantly better quality with high strength, low hardness and low cost, and the flaw detection yield can reach more than 95%, while the flaw detection yield of comparative example 1 is only 25%.
Further, the microstructures of examples 1 to 6 were observed, and it was found from the observation of the microstructures of examples 1 to 6 that the microstructures of the steels for high strength, low hardness and low cost 13Cr oil casings of examples 1 to 6 were tempered martensite + inverted austenite, wherein the volume fraction of the inverted austenite was 2% to 8%. Because the structure is mainly tempered martensite, the high strength of 110 steel grade can be still maintained, and simultaneously, a small amount of reverse austenite is used as a soft phase, so that the hardness level of the whole structure can be reduced.
In conclusion, the high-strength low-hardness low-cost 13Cr oil casing steel disclosed by the invention can ensure that the steel has low hardness while having high strength on the premise of reducing cost by reasonably designing chemical components and combining an optimization process, and is not easy to generate stress corrosion cracking failure in an underground corrosion environment after being put into a well in an oil field. The high-strength low-hardness low-cost 13Cr oil casing steel is low in production cost, and not only has high strength, but also has low hardness.
The yield strength of the high-strength low-hardness low-cost 13Cr oil casing steel is 758-965 MPa, the tensile strength is not less than 793MPa, and the hardness is not more than 28 HRC. The high-strength low-hardness low-cost 13Cr oil casing pipe prepared from the high-strength low-hardness low-cost 13Cr oil casing pipe steel has very excellent mechanical properties while ensuring lower production cost, can be effectively applied to well lowering operation of an oil field, and has good popularization prospect and application value.
Correspondingly, the manufacturing method provided by the invention is simple in production process and low in production cost, and can greatly reduce the production cost on the premise of ensuring the quality, the high-strength low-hardness low-cost 13Cr oil casing obtained by the manufacturing method not only has higher strength, but also has lower hardness, is not easy to generate stress corrosion cracking failure in an underground corrosion environment after an oil field is put into a well, can be effectively applied to 'three-super' (ultra-deep, ultra-high pressure and ultra-high temperature) oil and gas wells, and has important significance for ensuring long-term stable gas supply of the West-east gas transportation.
It should be noted that the combination of the features in the present application is not limited to the combination described in the claims of the present application or the combination described in the embodiments, and all the features described in the present application may be freely combined or combined in any manner unless contradicted by each other.
It should also be noted that the above-mentioned embodiments are only specific embodiments of the present invention. It is apparent that the present invention is not limited to the above embodiments and similar changes or modifications can be easily made by those skilled in the art from the disclosure of the present invention and shall fall within the scope of the present invention.
Claims (11)
1. The steel for the 13Cr oil casing pipe is characterized by comprising the following chemical elements in percentage by mass in addition to Fe and inevitable impurities:
0＜C≤0.04％，0＜Si≤0.5％，Mn：0.2～1.0％，Cr：11～14％，Mo：1～3％，Ni：4～7％，Ti：0.01～0.05％，N：0.001～0.015％；
and the chemical composition also satisfies: ti is more than or equal to (C + N), wherein C, Ti and N respectively represent the mass percentage content of corresponding elements.
2. The steel for high-strength low-hardness low-cost 13Cr oil casings as claimed in claim 1, wherein the steel comprises the following chemical elements in percentage by mass:
c is more than 0 and less than or equal to 0.04 percent, Si is more than 0 and less than or equal to 0.5 percent, Mn: 0.2-1.0%, Cr: 11-14%, Mo: 1-3%, Ni: 4-7%, Ti: 0.01-0.05%, N: 0.001-0.015%; the balance being Fe and unavoidable impurities.
3. The steel for high-strength low-hardness low-cost 13Cr oil casings according to claim 1 or 2, wherein the steel for high-strength low-hardness low-cost 13Cr oil casings has chemical elements in a mass percentage that satisfies at least one of the following:
0＜C≤0.03％；
Mn：0.3～0.5％；
Ni：4～6％。
4. the steel for high-strength low-hardness low-cost 13Cr oil casings according to claim 1 or 2, characterized in that, among other unavoidable impurities: p is less than or equal to 0.020% and/or S is less than or equal to 0.005%.
5. The steel for high-strength low-hardness low-cost 13Cr oil casings according to claim 1 or 2, characterized in that its microstructure is tempered martensite + inverted austenite, wherein the volume fraction of inverted austenite is 2% to 8%.
6. The steel for high-strength low-hardness low-cost 13Cr oil casings as claimed in claim 1 or 2, wherein the yield strength is 758-965 MPa, the tensile strength is not less than 793MPa, and the hardness is not more than 28 HRC.
7. A high-strength low-hardness low-cost 13Cr oil casing pipe, characterized by being produced using the steel for a high-strength low-hardness low-cost 13Cr oil casing pipe according to any one of claims 1 to 6.
8. The method of manufacturing a high strength, low hardness, low cost 13Cr oil casing according to claim 7, comprising the steps of:
(1) smelting in an electric furnace;
(2) adopting bloom continuous casting and soft reduction processes;
(3) rolling a tube blank, peeling the tube blank, heating the tube blank and perforating; wherein the annealing process is not carried out after the tube blank is rolled and before the tube blank is peeled;
(4) cold rolling;
(5) and (3) heat treatment: and (6) quenching and tempering.
9. The manufacturing method according to claim 8, wherein in the step (2), the reduction amount of the soft reduction process is 5 to 15 mm.
10. The manufacturing method according to claim 8 or 9, wherein in the step (5), when the quenching temperature is 880 to 960 ℃ and air quenching is employed, the subsequent tempering temperature is controlled to 570 to 595 ℃.
11. The manufacturing method according to claim 8 or 9, wherein in the step (5), when the quenching temperature is 880 to 960 ℃ and oil or water quenching is employed, the subsequent tempering temperature is controlled to 600 to 650 ℃.
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| JP2010242163A (en) * | 2009-04-06 | 2010-10-28 | Jfe Steel Corp | Method for manufacturing martensitic stainless steel seamless steel tube for oil well pipe |
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| JP2010242163A (en) * | 2009-04-06 | 2010-10-28 | Jfe Steel Corp | Method for manufacturing martensitic stainless steel seamless steel tube for oil well pipe |
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