CN115679199A - Steel for continuous speed pipe column, hot-rolled steel strip, steel pipe and manufacturing method thereof - Google Patents
Steel for continuous speed pipe column, hot-rolled steel strip, steel pipe and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses steel for a continuous speed pipe column, which contains Fe and inevitable impurities, and also contains the following chemical elements in percentage by mass: c:0.03-0.13%, si:0.05 to 0.30%, mn:0.86-2.20%, cr:0.10-0.60%, nb:0.030 to 0.065%, ti:0.008-0.025%, al:0.01-0.05%, ca:0.001-0.004%. In addition, the invention also discloses a hot-rolled steel strip made of the steel for the continuous velocity tubular column and a steel pipe made of the hot-rolled steel strip. In addition, the invention also discloses a manufacturing method of the hot-rolled steel strip and the steel pipe. The steel for the continuous speed pipe column effectively controls the alloy cost, and the prepared hot rolled steel strip has high safety and good corrosion resistance and is suitable for long-term service. The steel pipe made of the steel for the continuous velocity tubular column is convenient to operate, low in maintenance cost and beneficial to improving the operation efficiency, has more excellent corrosion resistance compared with the conventional low-carbon seamless velocity tubular column, and is more suitable for long-term service in the underground environment.
Description
Technical Field
The invention relates to a steel material and a manufacturing method thereof, in particular to a steel for a pipe column, a hot-rolled steel strip, a steel pipe and a manufacturing method thereof.
Background
The low-pressure low-permeability gas permeable well has wide distribution in China, the bottom hole pressure of the low-pressure low-permeability gas permeable well is low, the liquid carrying capacity of the gas well is weak, sufficient speed cannot be provided for discharging well liquid, liquid accumulation of different degrees easily occurs at the bottom hole of the low-pressure low-permeability gas permeable well, so that the gas production is reduced, the blowout of the gas well can be stopped in serious cases, and the pressure supply is large for stable production and maintenance.
In low pressure, low permeability gas permeable wells, it is often necessary to provide a velocity string in the well in order to ensure that the accumulated fluids at the bottom of the well can be drained to the surface. The speed pipe column is fixed in the well through a special hanger, and the available production surface area in the well can be reduced, so that the produced gas has enough energy to convey accumulated liquid to the ground, and further drainage gas production and yield increase and stable production are realized.
In the prior art, a conventional velocity string is a conventional oil pipe, is generally made of a common low-carbon seamless steel pipe, has a single length of about 10 meters basically, and is generally connected to a required length through a threaded joint.
In general, conventional velocity strings typically suffer from two problems:
(1) Poor safety: because the length of a single pipe column is short at the conventional speed, hundreds of threaded joints are needed to reach the underground depth of thousands of meters, and the falling risk of the pipe column is increased when one threaded joint is added; in addition, the speed pipe column needs to be in long-term contact with underground corrosive media, the conventional speed pipe column is made of ordinary low-carbon steel, and the threaded connection part is easy to accelerate corrosion, so that the whole corrosion resistance is poor, and leakage failure is easy to cause.
(2) The working efficiency is low: because the single length of conventional speed tubular column is short, need carry out threaded connection, consequently installation time is long, and the operating efficiency is low.
In view of the above, aiming at the defects of the velocity column in the prior art, the invention is expected to obtain a new steel for the continuous velocity column, which adopts a chemical element design different from the conventional velocity column steel, and can obtain better performance by matching and optimizing related manufacturing processes; the steel for the continuous velocity tubular column has high safety and good corrosion resistance, is suitable for long-term service, and can be effectively applied to the operation fields of drainage and gas production of oil and gas fields, well completion and the like.
The steel for the velocity pipe column is adopted and matched with a heating process to obtain the hot rolled steel strip, the prepared hot rolled steel strip can be welded into a steel pipe with the length of several kilometers through high-frequency induction welding, and the residual stress of the pipe body and the position of a welding line can be effectively reduced by stress relief heat treatment after welding. The steel pipe made of steel for the velocity string is connected in a non-threaded mode, the safety is high, the operation is convenient and fast, the maintenance cost is low, the operation efficiency can be improved, and the velocity string has more excellent corrosion resistance compared with a conventional low-carbon seamless velocity string and is more suitable for long-term service in the underground environment.
Disclosure of Invention
One of the objects of the present invention is to provide a steel for a continuous velocity string, which is different from the conventional velocity string steel in the component design concept, adopts a reasonable chemical component system design, and can effectively ensure the quality of steel materials by adopting a system mainly containing low C, medium and high Mn content and Cr-Nb-Ti. The low-C component design effectively reduces carbon segregation and central banded structures, and the medium-high Mn design can replace more traditional noble metals such as Ni and Mo to a certain extent, so that the alloy cost is reduced. The steel for the continuous velocity tubular column has low cost and excellent performance, can be used for preparing hot rolled steel strips and steel tubes, and can be effectively applied to the operation fields of drainage and gas production of oil and gas fields, well completion and the like.
In order to achieve the above object, the present invention provides a steel for a continuous velocity tubular column, which contains Fe and inevitable impurities, and further contains the following chemical elements in mass percent:
C：0.03-0.13％、Si：0.05-0.30％、Mn：0.86-2.20％、Cr：0.10-0.60％、Nb：0.030-0.065％、Ti：0.008-0.025％、Al：0.01-0.05％、Ca：0.001-0.004％。
further, in the steel for a continuous velocity tubular column of the present invention, the mass percentages of the chemical elements are:
c:0.03-0.13%, si:0.05 to 0.30%, mn:0.86-2.20%, cr:0.10-0.60%, nb:0.030 to 0.065%, ti:0.008-0.025%, al:0.01-0.05%, ca:0.001-0.004%, and the balance of Fe and other inevitable impurities.
In the steel for the continuous velocity tubular column, the low-C and medium-high Mn content and Cr-Nb-Ti are adopted as main component systems, the carbon segregation and the central banded structure are reduced through low-carbon component design, and the economical efficiency of the steel is improved on the premise of ensuring the mechanical property of the tubular product by improving the manganese to partially replace noble alloy elements such as Ni, mo and the like.
In the steel for a continuous velocity tubular column according to the present invention, the design principle of each chemical element is as follows:
c: in the steel for the continuous velocity tubular column, C is the most economic strengthening element, and the proper amount of C is added into the steel, so that the strength of the steel can be improved through interstitial solid solution strengthening. The improvement of the content of the C element in the steel can greatly improve the hardenability of the steel, reduce the addition of other precious alloys and further reduce the production cost, so that the content of the C element in the steel is not too low. However, it should be noted that the content of C element in steel should not be too high, and when the content of C element in steel is too high, not only ductility, toughness, weldability and corrosion resistance of steel are adversely affected, but also center segregation and banded structure are easily aggravated. Based on the above, in the steel for a continuous velocity tubular column according to the present invention, the mass percentage of the element C is controlled to be 0.03 to 0.13%.
Si: in the steel for a continuous velocity column according to the present invention, si is not only a solid solution strengthening element but also a deoxidizing element in the steel. However, it should be noted that the content of Si element in steel is not too high, and when the content of Si element in steel is too high, the surface quality and welding property of steel may be adversely affected, and if the content of Si exceeds 0.30%, the toughness of steel may be reduced. Based on this, in the steel for a continuous velocity tubular column according to the present invention, the Si element is controlled to be 0.05 to 0.30% by mass.
Mn: in the steel for a continuous velocity pipe column according to the present invention, mn element can improve the strength of the steel by solid solution strengthening, and Mn is the most dominant and economical strengthening element in the steel to compensate for the loss of strength due to the decrease of C content. In addition, the addition of a proper amount of Mn element in steel not only helps to obtain fine phase transition products, but also helps to control oxygen and sulfur in the steel-making process. If the content of Mn element in the steel is less than 0.86%, it may be difficult to obtain a target strength level; accordingly, the Mn element should not be added excessively, and excessive Mn will also aggravate center segregation, which is not favorable for the performance of the steel. Based on the above, in the steel for a continuous velocity tubular column according to the present invention, the mass percentage of Mn element is controlled to be 0.86 to 2.20%.
Cr: in the steel for the continuous velocity tubular column, the Cr element has a certain solid solution strengthening effect and can effectively improve the hardenability of the steel. Therefore, when the mass percent of Cr element in the steel is controlled to be 0.10% or more, the corrosion resistance of the steel can be effectively improved, and a compact protective layer is formed on the surface of the steel to play a role in protecting a matrix. However, it should be noted that the content of Cr element in steel should not be too high, and when the content of Cr element in steel is too high, the quality of weld joint is not good, and the defect of gray spot is easily formed. Based on the above, in the steel for a continuous velocity pipe column according to the present invention, the mass percentage of Cr element is controlled to be 0.10 to 0.60%.
Nb: in the steel for the continuous velocity tubular column, nb is an important element in low-carbon microalloy steel, and in the hot rolling process, the solid-dissolved Nb can be separated out through strain induction to form Nb carbonitride, the Nb carbonitride can pin grain boundaries to inhibit the growth of deformed austenite, and the deformed austenite is transformed into a fine product with high dislocation density through controlled rolling and controlled cooling. Further, after the steel strip is coiled, the solid-dissolved Nb is dispersed and precipitated in the matrix as second phase particles NbC, thereby functioning as precipitation strengthening. However, it should be noted that the content of Nb element in steel should not be too high, and too high content of Nb may cause slab crack easily, thereby affecting surface quality and deteriorating weldability of steel. Based on the above, in the steel for the continuous velocity tubular column, the mass percentage of the Nb element is controlled to be 0.030-0.065%.
Ti: in the steel for a continuous velocity tubular column according to the present invention, ti is not only a good deoxidizing and degassing agent but also an effective element for fixing nitrogen and carbon. Undissolved carbonitride of Ti element can prevent austenite grains from growing when steel is heated, and TiN and TiC precipitated during high-temperature austenite zone rough rolling can effectively inhibit the austenite grains from growing to refine the grains; in addition, ti can also improve the solid solubility of Nb and reduce the microcrack sensitivity of Nb-containing steel, and Ti is generally added with Nb in a compounding way, and in addition, precipitation in the welding process can also inhibit high-temperature crystal grains from growing so as to improve the welding performance of the material. Based on the above, in the steel for the continuous velocity tubular column, the mass percent of Ti element is controlled between 0.008 and 0.025%.
Al: in the steel for the continuous velocity tubular column, a proper amount of Al element can be added into the steel, the Al element can be used for steel grade deoxidation, and the addition of the proper amount of Al element into the steel is beneficial to grain refinement and the toughness of the steel is improved. However, it should be noted that the content of Al element in the steel is not excessively high, and when the content of Al element in the steel is more than 0.05%, coarse precipitates may be formed to deteriorate the toughness of the steel. Based on the above, in the steel for continuous velocity tubular column of the present invention, the mass percentage of Al element is controlled to be 0.01-0.05%.
Ca: in the steel for the continuous velocity column, a proper amount of Ca element can be added into the steel, ca treatment can be realized, the form of sulfide can be controlled through the Ca treatment, the anisotropy of a steel plate is improved, and the low-temperature toughness is improved. Based on this, in the steel for continuous velocity tubular column according to the present invention, the mass percentage of Ca element is controlled to be 0.001 to 0.004%.
Furthermore, the steel for the continuous velocity tubular column also contains at least one of Cu which is more than 0 and less than or equal to 0.4 percent, mo which is more than 0 and less than or equal to 0.2 percent and Ni which is more than 0 and less than or equal to 0.30 percent.
In the technical scheme of the invention, a proper amount of at least one of Cu element, ni element and Mo element can be added into the steel for the continuous velocity pipe column, and the performance of the steel can be further improved by adding the three elements.
Cu and Ni: in the steel for the continuous velocity tubular column, cu can improve the strength of steel through a solid solution strengthening effect and improve the atmospheric corrosion resistance of the steel, but the high content of Cu in the steel can cause hot cracking of the steel plate; the Ni element can effectively refine grains, can improve the hot brittleness easily caused by the Cu element in the steel, and is very beneficial to the toughness of the steel. Based on the above, in the steel for the continuous velocity tubular column, the mass percent of Cu element is controlled to be more than 0 and less than or equal to 0.4 percent, and the mass percent of Ni element is controlled to be more than 0 and less than or equal to 0.30 percent.
Mo: in the steel for the continuous velocity tubular column, mo is a strong hardenability element, can remarkably delay ferrite phase transformation, inhibit the formation of ferrite and pearlite, and can effectively promote bainite transformation to play a role in strengthening a matrix so as to obtain a finer structure. However, the content of Mo element in steel should not be too high, and when the content of Mo element in steel is too high, the plasticity of steel material is reduced. Based on the above, in the steel for the continuous velocity tubular column, the mass percent of Mo element is controlled to be more than 0 and less than or equal to 0.2 percent.
Further, in the steel for a continuous velocity column according to the present invention, P is not more than 0.015%, S is not more than 0.005%, and N is not more than 0.005%, among inevitable impurities.
In the technical scheme, the content of impurity elements such as P, S, N and the like needs to be strictly controlled. P, S and N are inevitable impurity elements in steel, and under the permission of technical conditions, in order to obtain the steel for the continuous speed tubular column with better performance and better quality, the content of the impurity elements in the steel is reduced as much as possible.
P, S and N are the main impurity elements in steel, P element is easy to cause cold brittleness of steel, S element is easy to cause hot brittleness, and the performance of steel is unstable, so the content of P, S in steel is reduced as much as possible; when the content of the impurity element N is too high, the high-concentration free N atoms are pinned with dislocation after aging, so that the yield strength of the material is obviously improved, and the toughness of the steel is damaged. Therefore, in the steel for the continuous velocity tubular column, the mass percent of P is controlled to be less than or equal to 0.015 percent, the mass percent of S is controlled to be less than or equal to 0.005 percent, and the mass percent of N is controlled to be less than or equal to 0.005 percent.
Further, in the steel for a continuous velocity pipe column according to the present invention, the microstructure is granular bainite + pearlite + ferrite, and the steel does not have a banded pearlite structure.
Further, in the steel for a continuous velocity column according to the present invention, the volume ratio of the granular bainite is not less than 80%.
Accordingly, another object of the present invention is to provide a hot rolled steel strip made of steel for continuous velocity tubular column, which can be rolled in a wide process range to obtain a hot rolled steel strip having good mechanical properties, which is excellent in properties, and which can be further made into a steel pipe.
In order to achieve the above object, the present invention provides a hot rolled steel strip made of the above steel for continuous velocity tubular column, having a yield strength of 450 to 550MPa, a tensile strength of 550 to 650MPa, and an elongation of 15% or more.
Accordingly, another object of the present invention is to provide a steel pipe which has excellent properties, can be used as a continuous velocity string in the fields of drainage, gas production, well completion and other operations in oil and gas fields, has no threaded connection, is high in safety, convenient to operate, low in maintenance cost, and beneficial to improving the operation efficiency, and is suitable for long-term service in the downhole environment.
In order to achieve the purpose, the invention provides a steel pipe made of the steel for the continuous velocity tubular column, wherein the yield strength is more than or equal to 550MPa, the tensile strength is more than or equal to 620MPa, and the elongation is more than or equal to 30%.
Accordingly, it is still another object of the present invention to provide a method of manufacturing the hot rolled steel strip, by which the hot rolled steel strip of the present invention can be efficiently manufactured, and the manufactured hot rolled steel strip has excellent properties, including a yield strength of 450 to 550MPa, a tensile strength of 550 to 650MPa, and an elongation of 15% or more.
In order to achieve the above object, the present invention provides the above method for manufacturing a hot rolled steel strip, comprising the steps of:
(1) Smelting, external refining and continuous casting;
(2) Hot rolling to obtain a hot rolled strip: controlling the heating temperature of the plate blank to be 1200-1300 ℃; the slab heat preservation time is 200-300min; controlling the finishing temperature to be 800-920 ℃; the coiling temperature is controlled to be 500-650 ℃.
In the manufacturing method of the hot rolled steel strip, in the step (1), the smelting process can be performed by conventional smelting methods such as electric furnace or converter smelting, and the external refining can be performed in the modes of RH vacuum degassing and LF desulphurization, so as to further refine the molten steel, wherein the RH vacuum degassing time can be controlled to be more than or equal to 3min. Correspondingly, after smelting is finished, in the subsequent continuous casting step, the superheat degree of continuous casting can be controlled to be 10-25 ℃, and the sedation time is controlled to be more than or equal to 6min.
Correspondingly, in the step (1) of the manufacturing method, a dynamic soft reduction technology and an electromagnetic stirring technology can be further adopted to improve the center segregation and the corrosion resistance.
In addition, in the step (2) of the method for manufacturing the hot-rolled steel strip, the slab is heated at a high temperature of 1200-1300 ℃ and is kept warm for a long time of 200-300min in the steel strip rolling stage, so that segregation can be further reduced, and the corrosion resistance and the performance uniformity of the steel can be improved.
Accordingly, in step (2) of the method for producing a hot-rolled steel strip according to the present invention, it is necessary to control the finish rolling temperature to 800 to 920 ℃ because: when the finishing rolling temperature is too high and exceeds 920 ℃, austenite grains are coarsened obviously, a steel belt easily generates a serious banded structure or mixed crystal structure, and the plasticity and the processing performance of the material are adversely affected; and if the finishing temperature is lower than 800 ℃, mixed crystals are easy to appear in the steel strip structure, and the performance is not favorable.
Further, in the present invention, the coiling temperature is controlled to be 500 to 650 ℃ because: when the coiling temperature is lower than 500 ℃, the proportion of bainite and other hard phase structures in the structure is obviously increased, even partial martensite structures may appear, the strength level and the fluctuation range of the steel strip are obviously increased, the performance stability and the plate shape are poor, and the subsequent pipe-making forming is not facilitated; if the coiling temperature exceeds 650 ℃, the strength is easy to be lower, a severe banded structure is easy to generate, the existence of the banded structure can enable the mechanical property of the metal to be anisotropic, the direction along the banded structure is obviously superior to the vertical direction, and the characteristic is easy to cause the hot rolled steel strip to be easy to break from the junction in the subsequent pipe making and forming process.
Further, in the method for manufacturing a hot-rolled steel strip according to the present invention, in the step (1), a degree of superheat of continuous casting is controlled to be 10 to 25 ℃, and/or a calm time is equal to or more than 6min.
Accordingly, another object of the present invention is to provide a method for manufacturing the above steel pipe, wherein the steel pipe manufactured by the method has excellent performance, and can be used as a continuous velocity string in the fields of drainage, gas production, well completion and other operations; the steel pipe is in non-threaded connection, high in safety, convenient to operate, low in maintenance cost, beneficial to improving the operation efficiency, suitable for long-term service in the underground environment, and good in popularization prospect and application value.
In order to achieve the above object, the present invention provides the above method for manufacturing a steel pipe, comprising the steps of:
(1) Smelting, external refining and continuous casting;
(2) Hot rolling to obtain a hot rolled strip: controlling the heating temperature of the plate blank to be 1200-1300 ℃; the slab heat preservation time is 200-300min; controlling the finishing temperature to be 800-920 ℃; controlling the coiling temperature to be 500-650 ℃;
(3) Acid washing;
(4) Manufacturing a pipe;
(5) Stress relief heat treatment is carried out on the pipe body and the welding seam at the temperature of 600-950 ℃;
(6) And (5) coiling to obtain a finished steel pipe.
In the above technical solution of the present invention, in the manufacturing process of manufacturing the steel pipe, the main process path may include: smelting → external refining → continuous casting → slab finishing → slab reheating → controlled rolling and controlled cooling → coiling → flattening → head and tail cutting → acid cleaning → edge cutting → oil coating → coiling → slitting and butting → shaping → high frequency induction welding → stress relief heat treatment → coiling.
It should be noted that, in the method for manufacturing the steel pipe of the present invention, the operations of step (1) and step (2) can be substantially combined with the method for manufacturing the hot rolled steel strip of the present invention, and the processes adopted by both methods are the same. That is, the hot-rolled steel strip according to the present invention may be further subjected to the above-described steps (3), (4), (5) and (6) to produce a finished steel pipe according to the present invention.
In step (3) of the method for producing a steel pipe according to the present invention, a steel strip having a good surface quality can be obtained by pickling. Wherein, in the step of pickling, the coiling temperature of pickling is preferably controlled to be less than or equal to 80 ℃, and the pickling temperature is 60-80 ℃; the pickling time is 40-100s.
Correspondingly, in the step (4) of the steel pipe manufacturing method, the steel strip can be longitudinally cut into the width required by the continuous oil pipe in the pipe manufacturing stage, then the butt joint of the steel strip is completed along the length direction in an end welding mode, and after the welded steel strip is bent and formed by a forming unit, the straight welding seam welding can be completed by utilizing high-frequency induction welding. After the welding is finished, stress relief heat treatment at 600-950 ℃ can be further carried out on the welding seam and the pipe body in the subsequent step (5), and the finished steel pipe can be obtained by coiling on a coiling block through a coiling machine after the heat treatment is finished.
Further, in the method for manufacturing a steel pipe according to the present invention, in the step (1), the degree of superheat of continuous casting is controlled to be 10 to 25 ℃, and/or the period of time of sedation is not less than 6min.
Further, in the method for manufacturing the steel pipe, the coiling temperature of acid washing is controlled to be less than or equal to 80 ℃ and the acid washing temperature is controlled to be 60-80 ℃ in the step (3); the pickling time is 40-100s.
Compared with the prior art, the steel, the hot rolled steel strip and the steel pipe for the continuous velocity tubular column and the manufacturing method thereof have the advantages and beneficial effects as follows:
the steel for the continuous velocity tubular column adopts a reasonable chemical composition system design, and can effectively ensure the quality of steel by adopting a system with low C content, medium and high Mn content and Cr-Nb-Ti as main components. The low-C component design effectively reduces carbon segregation and a central banded structure, and the medium-high Mn design can replace more traditional noble metals such as Ni, mo and the like to a certain extent, so that the alloy cost is reduced; in addition, the invention strictly controls the content of impurity elements such as P, S, N and the like, and can also adopt a dynamic soft reduction technology and an electromagnetic stirring technology in a matching way in the manufacturing process so as to improve the center segregation of steel.
In addition, by adopting the steel for the continuous velocity tubular column and matching with the optimized process design, the hot rolling can be carried out in a wider process range to obtain the hot rolled steel strip, and the prepared hot rolled steel strip has very excellent mechanical properties.
In addition, the steel pipe provided by the invention can be further prepared by adopting the hot rolled steel strip provided by the invention, has very excellent performance, has more excellent corrosion resistance compared with a conventional low-carbon seamless speed pipe column, is more suitable for a long-term service environment in a well, and can be used as a continuous speed pipe column to be applied to the operation fields of drainage and gas production of an oil and gas field, well completion and the like; the steel pipe is in non-threaded connection, high in safety, convenient to operate, low in maintenance cost, beneficial to improving the operation efficiency, and good in popularization prospect and application value.
Correspondingly, in the manufacturing method of the steel pipe, the technological parameters are optimally designed in the stage of obtaining the hot rolled steel strip by hot rolling, the slab is optimally controlled to be heated at the high temperature of 1200-1300 ℃ and subjected to long-time heat preservation for 200-300min, the segregation can be further reduced, and the corrosion resistance and the performance uniformity of the material are improved. In addition, in the subsequent pipe manufacturing process of the hot rolled steel strip, a single continuous speed pipe column with the length of thousands of meters can be realized through high-frequency induction welding, and post-welding stress relief heat treatment can be adopted to reduce the residual stress of the pipe body and the position of a welding line.
Drawings
FIG. 1 is a photograph of the microstructure of the hot-rolled steel strip of example 1-1 under a microscope of 500 times.
Detailed Description
The steel for continuous velocity tubular column, hot rolled steel strip, steel pipe and method for manufacturing the same according to the present invention will be further explained and illustrated with reference to the drawings and the specific examples, which, however, should not be construed to unduly limit the technical solution of the present invention.
Examples 1 to 6
Table 1 shows the mass percentages of the respective chemical elements in the steels for continuous velocity columns of examples 1 to 6.
TABLE 1 (wt%, balance Fe and unavoidable impurities other than P, S, N)
The steels for continuous velocity column according to examples 1-6 of the present invention can be manufactured into corresponding hot rolled steel strips, and examples 1-1 to 6-1 hereinafter represent hot rolled steel strips manufactured using the steels for continuous velocity column according to examples 1-6.
In the present invention, the hot rolled steel strips of examples 1-1 to 6-1 were produced by the following steps:
(1) Smelting, external refining and continuous casting are carried out according to the chemical composition design shown in the table 1: in the smelting step, an electric furnace and a converter are adopted for smelting, external refining is carried out for RH vacuum degassing and LF desulphurization, wherein the time of vacuum degassing is controlled to be more than or equal to 3min; in the continuous casting step, the superheat degree of continuous casting is controlled to be 10-25 ℃, and the sedation time is controlled to be more than or equal to 6min.
(2) Hot rolling to obtain a hot rolled strip: controlling the heating temperature of the plate blank to be 1200-1300 ℃; the slab heat preservation time is 200-300min; controlling the finishing temperature to be 800-920 ℃; the coiling temperature is controlled to be 500-650 ℃.
It should be noted that in the present invention, the chemical compositions and the relevant process parameters of the hot rolled steel strips of examples 1-1 to 6-1 all meet the design specification control requirements of the present invention.
Table 2 lists specific process parameters in the manufacturing method of the hot rolled steel strip of example 1-1 to example 6-1.
Table 2.
The hot rolled steel strips of examples 1-1 to 6-1 thus obtained were sampled to obtain samples, and the yield strength, elongation and the like of the hot rolled steel strips of each example were measured to obtain test data for evaluating mechanical properties thereof, respectively, and the results of the measurement of the mechanical properties are shown in table 3 below.
The relevant mechanical property tests were as follows:
and (3) tensile test: the yield strength, tensile strength and elongation at room temperature of the hot rolled steel strip samples of examples 1-1 to 6-1 were measured using a tensile tester under an ambient temperature environment in accordance with the method of GB/T228.1-2010.
Table 3 lists the relevant mechanical property parameters of the hot rolled steel strips of examples 1-1 to 6-1.
Table 3.
The hot rolled steel strips of the embodiments are observed, and the hot rolled steel strips of the embodiments with ferrite, pearlite and bainite as microstructure matrixes can be obtained by adopting the design components of the invention. As can be seen from Table 3, the hot rolled steel strips of examples 1-1 to 6-1 had a yield strength of 465 to 542MPa, a tensile strength of 558 to 645MPa and an elongation of 19% or more. The hot rolled steel strips of the embodiments have good plasticity, toughness and processability, and are very beneficial to the subsequent further pipe making process.
After the mechanical properties of the hot rolled steel strips of examples 1-1 to 6-1 were examined, the hot rolled steel strips of examples were reprocessed to produce steel pipes, respectively, and the steel pipes of examples produced correspondingly were shown in examples 1-2 to 6-2, respectively.
In the present invention, the steel pipes of examples 1-2 to 6-2 were all produced by the following steps:
(1) Smelting, external refining and continuous casting are carried out according to the chemical composition design shown in the table 1: in the smelting step, an electric furnace and a converter are adopted for smelting, external refining is carried out for RH vacuum degassing and LF desulphurization, wherein the time of vacuum degassing is controlled to be more than or equal to 3min; in the continuous casting step, the superheat degree of continuous casting is controlled to be 10-25 ℃, and the sedation time is controlled to be more than or equal to 6min.
(2) Hot rolling to obtain a hot rolled strip: controlling the heating temperature of the plate blank to be 1200-1300 ℃; the slab heat preservation time is 200-300min; controlling the finishing temperature to be 800-920 ℃; the coiling temperature is controlled to be 500-650 ℃.
(3) Acid washing: controlling the coiling temperature of pickling to be less than or equal to 80 ℃, and the pickling temperature to be 60-80 ℃; the pickling time is 40-100s.
(4) Pipe making: the steel strip is longitudinally cut into the width required by the coiled tubing, the end parts of the steel strip are obliquely cut into 45 degrees and then welded, and the steel strip is subjected to high-frequency induction welding after being bent and formed by a forming unit.
(5) And (3) performing stress relief heat treatment on the pipe body and the welding seam at 600-950 ℃.
(6) And (4) coiling to obtain a finished steel pipe.
It should be noted that the chemical compositions and related process parameters of the steel pipes of examples 1-2 to 6-2 all satisfy the design specification control requirements of the present invention, and the related process parameters of the steel pipes of examples 1-2 to 6-2 in step (1) and step (2) are completely the same as the process parameters listed in table 2. That is, the hot rolled steel strips of examples 1-1 to 6-1 according to the present invention may be further subjected to the above-described steps (3), (4), (5) and (6) to produce finished steel pipes of examples 1-2 to 6-2 according to the present invention.
In the invention, after the hot rolling is finished, the steel strip is pickled, and after the hot rolled steel strip is pickled and oiled, hot rolling oxide skin is removed, so that the hot rolled pickled steel strip with good surface quality is obtained, the thickness of the steel strip is 4mm, the width of the steel strip is 1.2m, and the whole roll weight is 18 tons.
Table 4 lists specific process parameters in the manufacturing methods of the steel pipes of examples 1-2 to 6-2.
Table 4.
The prepared steel pipes of examples 1-2 to 6-2 were sampled, respectively, and the yield strength, elongation, and other relevant properties of the steel pipes of each example were measured, thereby obtaining test data for evaluating the mechanical properties thereof, respectively, which are listed in table 5.
In the present invention, the mechanical properties of the steel pipes in the embodiments are also tested by the tensile test, and the relevant testing means of the tensile test are disclosed in the above contents of the present invention, and are not described herein again.
Table 5 lists the relevant mechanical properties parameters for the steel pipes of examples 1-2 to 6-2.
Table 5.
The steel pipes of the embodiments are observed, and the steel pipes of the embodiments with the microstructure matrix of ferrite, pearlite and bainite can be obtained by adopting the design components of the invention. As can be seen from Table 5, the hot rolled steel strips of examples 1-2 to 6-2 had yield strengths of 569 to 596MPa, tensile strengths of 652 to 683MPa, and elongations of 30 to 33%.
In addition, in order to further verify that the steel pipes for continuous velocity columns according to the present invention have excellent resistance to hydrogen sulfide corrosion, the steel pipes of examples 1-2 to 6-2 were further sampled and evaluated for wet hydrogen sulfide (H) in the examples using NACE TM0284-2016 Standard test method for evaluating hydrogen induced cracking resistance of steel for pipe and pressure vessel 2 S) Hydrogen Induced Cracking (HIC) resistance in environment, using standard sample and A solution (H) 2 Sodium chloride and acetic acid solution prepared with S-saturated deionized water) and soaking for 96 hours. As a result, it was found that no crack was observed in any of the steel pipe samples of examples.
In addition, the test pieces of steel pipes of examples 1-2 to 6-2 were subjected to sulfide stress corrosion cracking resistance test method for metallic materials in a pressurized S environment in accordance with NACE TM 0177-2016 StandardHydrogen sulfide stress corrosion cracking test, using NACE Standard tensile test method, stress loading is 72% of yield strength, solution A (H) after 720 hours 2 Sodium chloride and acetic acid solution in S-saturated deionized water) were soaked and no steel pipe sample of each example was found to be broken.
Therefore, the steel pipe made of the steel for the continuous speed pipe column has excellent hydrogen sulfide stress corrosion resistance, is suitable for long-term service in the underground environment, can be effectively applied to the operation fields of drainage and gas production of oil and gas fields, well completion and the like, and has good popularization prospect and application value.
FIG. 1 is a photograph of the microstructure of the hot-rolled steel strip of example 1-1 under a microscope of 500 times.
As shown in FIG. 1, in the present invention, the microstructure of the hot-rolled steel strip of example 1-1 was granular bainite + pearlite + ferrite, and the microstructure thereof did not have a band-like pearlite structure. Statistical analysis shows that the volume proportion of the granular bainite in the microstructure is more than or equal to 80 percent.
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.
In addition, it should 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 (13)
1. The steel for the continuous speed pipe column contains Fe and inevitable impurities, and is characterized by further containing the following chemical elements in percentage by mass:
C：0.03-0.13％、Si：0.05-0.30％、Mn：0.86-2.20％、Cr：0.10-0.60％、Nb：0.030-0.065％、Ti：0.008-0.025％、Al：0.01-0.05％、Ca：0.001-0.004％。
2. the steel for continuous velocity pipe column according to claim 1, wherein the steel comprises the following chemical elements in percentage by mass:
c:0.03-0.13%, si:0.05 to 0.30%, mn:0.86-2.20%, cr:0.10-0.60%, nb:0.030 to 0.065%, ti:0.008 to 0.025%, al:0.01-0.05%, ca:0.001-0.004%, and the balance of Fe and other inevitable impurities.
3. The steel for continuous velocity steel pipe string according to claim 1 or 2, further comprising at least one of 0 < Cu.ltoreq.0.4%, 0 < Mo.ltoreq.0.2%, and 0 < Ni.ltoreq.0.30%.
4. The steel for a continuous velocity column according to claim 1 or 2, wherein P is 0.015% or less, S is 0.005% or less, and N is 0.005% or less among unavoidable impurities.
5. The steel for continuous velocity steel pipes according to claim 1 or 2, wherein the microstructure is granular bainite + pearlite + ferrite, and the microstructure is free of banded pearlite.
6. The steel for a continuous velocity tubular column according to claim 5, wherein the granular bainite is 80% or more by volume.
7. A hot-rolled steel strip produced from the steel for continuous velocity tubular column according to any one of claims 1 to 6, characterized in that it has a yield strength of 450 to 550MPa, a tensile strength of 550 to 650MPa and an elongation of 15% or more.
8. A steel pipe made of steel for a continuous velocity string according to any one of claims 1 to 6, characterized in that it has a yield strength of 550MPa or more, a tensile strength of 620MPa or more and an elongation of 30% or more.
9. The method of making hot rolled steel strip as claimed in claim 7 comprising the steps of:
(1) Smelting, external refining and continuous casting;
(2) Hot rolling to obtain a hot rolled strip: controlling the heating temperature of the plate blank to be 1200-1300 ℃; the slab heat preservation time is 200-300min; controlling the finishing temperature to be 800-920 ℃; the coiling temperature is controlled to be 500-650 ℃.
10. The method of manufacturing a hot-rolled steel strip as claimed in claim 9, wherein in the step (1), the degree of superheat of the continuous casting is controlled to 10 to 25 ℃ and/or the calming time is 6min or more.
11. A method of manufacturing a steel pipe as defined in claim 8, comprising the steps of:
(1) Smelting, external refining and continuous casting;
(2) Hot rolling to obtain a hot rolled strip: controlling the heating temperature of the plate blank to be 1200-1300 ℃; the slab heat preservation time is 200-300min; controlling the finishing temperature to be 800-920 ℃; controlling the coiling temperature to be 500-650 ℃;
(3) Acid washing;
(4) Manufacturing a pipe;
(5) Stress relief heat treatment is carried out on the pipe body and the welding seam at the temperature of 600-950 ℃;
(6) And (5) coiling to obtain a finished steel pipe.
12. The method of manufacturing a steel pipe as defined in claim 11 wherein in the step (1), the degree of superheat of the continuous casting is controlled to 10-25 ℃ and/or the period of sedation is 6min or more.
13. The method of manufacturing a steel pipe as claimed in claim 11, wherein in the step (3), the coiling temperature of pickling is controlled to 80 ℃ or less, and the pickling temperature is controlled to 60 to 80 ℃; the pickling time is 40-100s.
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