CN115433870B - Low-cost quenched and tempered steel for continuous oil pipe, hot rolled steel strip, steel pipe and manufacturing method thereof - Google Patents

Low-cost quenched and tempered steel for continuous oil pipe, hot rolled steel strip, steel pipe and manufacturing method thereof Download PDF

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CN115433870B
CN115433870B CN202110613116.2A CN202110613116A CN115433870B CN 115433870 B CN115433870 B CN 115433870B CN 202110613116 A CN202110613116 A CN 202110613116A CN 115433870 B CN115433870 B CN 115433870B
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steel
quenched
tempered
continuous oil
cost
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CN115433870A (en
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张豪臻
章传国
沈建兰
孙磊磊
王金涛
王明
梅峰
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Baoshan Iron and Steel Co Ltd
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Baoshan Iron and Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
    • E21B17/20—Flexible or articulated drilling pipes, e.g. flexible or articulated rods, pipes or cables
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

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Abstract

The invention discloses a low-cost quenched and tempered steel for continuous oil pipes, which contains the following chemical elements in percentage by mass except Fe and unavoidable impurities: c:0.18-0.32%, si:0.05-0.30%, mn:0.90-2.50%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, cr:0.10-0.50%, ti:0.008-0.025%, cu:0.10-0.40%, ni:0.05-0.30%, B:0.002-0.005%, ca:0.001-0.004%, al:0.01-0.05%, N is more than 0 and less than or equal to 0.007%. The invention also discloses a hot rolled steel strip prepared from the quenched and tempered continuous oil pipe steel and a steel pipe prepared from 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 low-cost quenched and tempered steel for the continuous oil pipe effectively controls the alloy cost, and the prepared hot rolled steel strip has lower strength and better shaping, toughness and processability.

Description

Low-cost quenched and tempered steel for continuous oil pipe, hot rolled steel strip, steel pipe and manufacturing method thereof
Technical Field
The present invention relates to a metal material and a method for producing the same, and more particularly, to a steel, a steel strip, a steel pipe for a hardened and tempered continuous oil pipe and a method for producing the same.
Background
Quenched and tempered Coiled Tubing (CT) is tubing that is a continuous tube without joints, also known as Coiled tubing, coiled tubing or Coiled tubing, that is made by miter-joint of several lengths of steel strip, welded by roll forming, as opposed to conventional threaded tubing. The coiled tubing has outstanding advantages in oilfield operation, has been rapidly developed in recent decades, is widely applied to the working processes of oil and gas field well repair, well drilling, well completion, well logging and the like, and is known as a universal working machine.
In the current coiled tubing application, the conventional low-carbon alloy steel pipe is still mainly used, the conventional CT90 structure is ferrite, pearlite and bainite, the CT110 structure is bainite and a small amount of ferrite, the CT90 and the CT110 are the most widely used steel grade, and the production difficulty of the CT130 with higher strength is high.
In the industrial production process, with the improvement of the steel grade of the low-carbon alloy steel pipe, more alloy elements are generally required to be added, which can lead to the great increase of alloy cost and bring great pressure to the manufacturing stability and equipment capacity load of each process of steel strip rolling, pipe making and the like.
In addition, conventional coiled tubing generally only carries out simple stress relief annealing after tubing, the structure of the welding seam and the tube body have larger difference, the welding part has larger residual stress and is more easily corroded, and along with the improvement of the strength grade of the coiled tubing, the fatigue life of the welding seam also has a descending trend relative to the tube body, and the field failure also occurs in many cases. Therefore, how to further improve the performance of coiled tubing to cope with complex well conditions while controlling alloy costs is a current trend of coiled tubing products.
Based on the above, the invention is expected to obtain the steel, the hot rolled steel strip, the steel tube and the manufacturing method for the low-cost quenched and tempered continuous oil tube, the invention aims at the difficulty in improving the strength of the conventional continuous oil tube, the alloy design different from the conventional continuous oil tube is adopted, the hot rolled and pickled steel strip for the continuous oil tube with lower strength and excellent surface quality can be obtained through rolling and pickling, the prepared steel strip is subjected to heat treatment after the tube is manufactured, the continuous oil tube is subjected to online quenching and tempering by adding a special heat treatment system, the adjustable continuous oil tube can be obtained through the adjustment of the heat treatment process, the prepared continuous oil tube strength covers CT90 steel grade and CT110 steel grade, the maximum strength of the prepared continuous oil tube can reach CT130 steel grade, and compared with the conventional TMCP state continuous oil tube, the structure property uniformity of a tube body and a welding line is improved, and the excellent fatigue life and corrosion resistance are realized.
Disclosure of Invention
One of the purposes of the invention is to provide a low-cost quenched and tempered steel for continuous oil pipe, which adopts a component design thought different from that of a conventional continuous oil pipe, and effectively controls alloy cost while improving steel strength by adopting a chemical component design taking carbon and manganese reinforcement as main materials and multiple microalloy as auxiliary materials. The low-cost quenched and tempered steel for the continuous oil pipe has low cost and excellent performance, can be used for preparing hot rolled steel strips and steel pipes, is effectively applied to the operation fields of oil and gas field drilling, well repair, well completion and the like, and has very good popularization prospect and application value.
In order to achieve the above object, the present invention provides a low-cost quenched and tempered steel for continuous oil pipe, which contains Fe and unavoidable impurities and which further contains the following chemical elements in mass percent:
C：0.18-0.32％、Si：0.05-0.30％、Mn：0.90-2.50％、P≤0.015％、S≤0.005％、Cr：0.10-0.50％、Ti：0.008-0.025％、Cu：0.10-0.40％、Ni：0.05-0.30％、B：0.002-0.005％、Ca：0.001-0.004％、Al：0.01-0.05％、0＜N≤0.007％。
further, in the low-cost quenched and tempered steel for continuous oil pipe, the mass percentages of the chemical elements are as follows:
c:0.18-0.32%, si:0.05-0.30%, mn:0.90-2.50%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, cr:0.10-0.50%, ti:0.008-0.025%, cu:0.10-0.40%, ni:0.05-0.30, B:0.002-0.005%, ca:0.001-0.004%, al:0.01-0.05%, N is more than 0 and less than or equal to 0.007%, and the balance is Fe and other unavoidable impurities.
In the low-cost quenched and tempered steel for continuous oil pipes, C, mn is adopted as a main component system, and a certain amount of B element is added to increase the hardenability of the steel, so that the steel has higher strength after pipe making and heat treatment.
Of course, in some preferred embodiments, proper amounts of Nb and Mo elements can be added into the steel, and the tempering resistance can be reduced by reducing the Cr and Mo contents so as to achieve lower hardness requirements after heat treatment; in addition, in some preferred embodiments, trace Ti and Nb elements can be added to achieve the effect of grain refinement.
In the low-cost quenched and tempered steel for continuous oil pipe of the present invention, the design principle of each chemical element is as follows:
c: in the low-cost quenched and tempered steel for continuous oil pipe, C is the most economical strengthening element, and the strength of the steel can be improved by adding a proper amount of C element into the steel and carrying out interstitial solid solution strengthening. The quenching degree of the steel can be greatly improved by improving the content of the C element in the steel, the addition amount of other noble alloys is reduced, the production cost is further reduced, and the yield ratio of the steel is reduced, so that the content of the C element in the steel is not excessively low. However, it should be noted that the content of C element in the steel is not too high, and when the content of C element in the steel is too high, the ductility, toughness and weldability of the steel are adversely affected. Based on the above, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of the element C is controlled to be 0.18 to 0.32%.
Of course, in some preferred embodiments, the mass percentage of the element C may be controlled between 0.20% and 0.30% for better implementation.
Si: in the low-cost quenched and tempered steel for continuous oil pipe 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 Si element content in the steel is not too high, and when the Si element content in the steel is too high, it may deteriorate the welding performance of the steel, and it may be easy to cause scale produced in the hot rolling process to be difficult to remove, thereby affecting the surface quality, and if the Si content exceeds 0.30%, the toughness of the steel may be reduced, and tempering brittleness may be easily promoted. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of Si element is controlled to be 0.05 to 0.30%.
Of course, in some preferred embodiments, the mass percentage of Si element may be controlled to be between 0.05 and 0.22% for better implementation.
Mn: in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, mn element can increase the strength of steel by solid solution strengthening, which is the most main and economical strengthening element in steel to compensate for the loss of strength due to the decrease of C content. In addition, mn is also an element for enlarging a gamma phase region, which can lower the gamma-to-alpha phase transition temperature of steel, help to obtain a fine phase transition product, can improve toughness of steel, and also helps control oxygen and sulfur in a steelmaking process. Therefore, in order to ensure the beneficial effect of the Mn element, a desired strength level is obtained, and the Mn element content in the steel is not preferably less than 0.90%. However, when the Mn element content in steel increases, segregation tends to be serious, and embrittlement components are easily formed during heat treatment, so that fatigue life and corrosion resistance of the coiled tubing are reduced. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of Mn element is controlled to be 0.90 to 2.50%.
Of course, in some preferred embodiments, the mass percentage of Mn element may be controlled to be between 1.20 and 1.80% in order to obtain a more preferable implementation effect.
P, S: in the steel for the low-cost quenched and tempered continuous oil pipe, P and S are unavoidable impurity elements in the steel, and when the content of the P element in the steel is too high, the steel is easy to be cold and crisp; when the S content in the steel is too high, the steel is easy to cause thermal embrittlement, so that the performance of the steel is unstable, and the content of phosphorus and sulfur in the steel is reduced as much as possible under the condition of allowable technical conditions. Based on the above, in the low-cost quenched and tempered steel for continuous oil pipe, the mass percentage of P is controlled to be less than or equal to 0.015%, and the mass percentage of S is controlled to be less than or equal to 0.005%.
Cr: in the low-cost quenched and tempered steel for continuous oil pipe, cr element can improve the hardenability of the steel and has a certain solid solution strengthening effect. Therefore, when the mass percentage 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 can be formed on the surface of the steel to play a role in protecting a matrix. However, it should be noted that the Cr element content in the steel is not too high, and when the Cr element content in the steel is too high, the tempering brittleness of the steel is promoted, the quality of the weld is not good, and the gray spot defect is easily formed. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of Cr element is controlled to be 0.10 to 0.50%.
Ti: in the low-cost quenched and tempered steel for continuous oil pipe of the present invention, ti is an effective element for good deoxidizing and degassing agent and nitrogen and carbon fixation. The undissolved carbonitride of Ti can prevent the growth of austenite grains when the steel is heated, and the TiN and TiC separated out during rough rolling in a high-temperature austenite region can effectively inhibit the growth of austenite grains so as to refine the grains, and in addition, the TiN and TiC separated out during welding can inhibit the growth of high Wen Jingli so as to improve the welding performance. In addition, the addition of a proper amount of Ti element to the steel is also advantageous in reducing the temper brittleness of the steel. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of Ti element is controlled to be 0.008 to 0.025%.
Cu: in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, a proper amount of Cu element may be added to the steel to improve the strength of the steel by solid solution strengthening. In addition, the addition of a proper amount of Cu element in the steel can also obviously improve the atmospheric corrosion resistance of the steel. However, it should be noted that the Cu content in the steel is not too high, and when the Cu content in the steel is high, the hot workability of the steel is adversely affected. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of Cu element is controlled to be 0.10 to 0.40%.
Ni: in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, a proper amount of Ni element may be added to the steel to increase the strength of the steel by solid solution strengthening. The Ni element can effectively refine grains and improve the hot brittleness which is easy to be caused by Cu element in steel, and is very beneficial to the toughness of the steel. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of Ni element is controlled to be 0.05 to 0.30%.
B: in the steel for the low-cost quenched and tempered continuous oil pipe, the main function of B in the steel is to increase the hardenability of the steel, so that the performance of the quenched and tempered material after quenching and tempering can be effectively improved, and the uniformity of the performance in the thickness direction can be improved. In addition, the steel can be added with a proper amount of B element to replace other noble metal elements to a certain extent, so that the production cost is reduced. However, it should be noted that the content of B element in the steel is not excessively high, and when the content of B element in the steel exceeds 0.005%, the hardenability of the steel tends to decrease instead, and the B element tends to promote temper embrittlement. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of the B element is controlled to be 0.002 to 0.005%.
Of course, in some preferred embodiments, the mass percentage of the B element may be controlled between 0.0025 and 0.0045% for better implementation.
Ca: in the low-cost quenched and tempered steel for continuous oil pipe of the present invention, a proper amount of Ca element is added to realize Ca treatment, and the form of sulfide can be controlled by Ca treatment, so that the anisotropy of the steel sheet can be improved and the low-temperature toughness of the steel sheet can be improved. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of Ca element is controlled to be 0.001 to 0.004%.
Al: in the low-cost quenched and tempered steel for continuous oil pipe, al is an element added into the steel for deoxidization, and proper amount of Al is added to facilitate grain refinement and improve the toughness of the steel. 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, thereby impairing the toughness of the steel. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of Al element is controlled to be 0.01 to 0.05%.
N: in the low-cost quenched and tempered steel for continuous oil pipe, proper amount of N element is added to form high-melting point TiN particles, so that the effect of inhibiting coarsening of slab grains in the reheating process is achieved, and the toughness of the steel is improved. However, it should be noted that the N element content in the steel is not too high, and when the N element content in the steel is too high, the high concentration of free N atoms after aging causes pinning dislocation, which leads to a significant increase in the yield strength of the steel, but also causes a loss of toughness of the material. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of N element is controlled to be 0 < N.ltoreq.0.007%.
Therefore, when the steel for the low-cost quenched and tempered continuous oil pipe is designed in chemical composition, the composition and the process design thought different from those of a conventional continuous oil pipe are adopted, and the strength and the toughness of the material are ensured by taking micro alloys such as carbon and manganese reinforcement as main materials and Ti as auxiliary materials; the tempering brittleness and tempering resistance are weakened through low Cr and Mo, so that the material has better toughness and low hardness after pipe making and final heat treatment; by adding a proper amount of B element to partially replace Cr and Mo, the steel is ensured to have good hardenability, the uniformity of the performance after heat treatment is improved, and the alloy cost is effectively reduced.
Further, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, each chemical element thereofThe mass percentage content satisfies: 75.5-0.094X150+6.66 (C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15). Ltoreq.22; and/or P (Si+Mn). Times.10 4 And the content of each element in the formula is less than or equal to 150, and the values before the mass percentage of the corresponding element are shown.
Further, in the low-cost quenched and tempered steel for continuous oil pipe, the mass percentage of each chemical element is as follows: 75.5-0.094X150+6.66 (C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15). Ltoreq.20; and/or P (Si+Mn). Times.10 4 And less than or equal to 130, wherein each element represents a numerical value before the mass percent of the corresponding element.
In the above technical scheme of the present invention, after the steel for low-cost quenched and tempered continuous oil pipe is smelted, cast and hot rolled to obtain a hot rolled steel strip, the hot rolled steel strip may be further subjected to steps such as pickling, pipe making, heat treatment and coiling to obtain a corresponding steel pipe. Wherein after the pipe is manufactured, quenching and tempering treatment are needed in the subsequent heat treatment step, and the theoretical value of the hardness of the material after high-temperature tempering is HRC cal In order to ensure that the quenched and tempered material meets the upper hardness limit requirement of CT90, the invention can further control C, mn, cr, mo, V, ni, cu elements to meet the requirements of the following components while controlling the mass percentage of single chemical elements: HRC (high-resolution imaging) cal (temperature t=650) =75.5-0.094x650+6.66 (c+mn/6+ (cr+mo+v)/5+ (ni+cu)/15). Ltoreq.22; of course, in some preferred embodiments, it may be preferable to control the HRC cal (temperature T=650). Ltoreq.20. Each chemical element in the formula is substituted into the numerical value before the mass percentage of the chemical element.
In addition, it should be noted that the P element is easily segregated at grain boundaries after heat treatment, and the intergranular cohesion is weakened, and both Mn and Si promote segregation of the P element, thereby increasing embrittlement. Therefore, the invention can preferably control the P, si and Mn elements in the steel to satisfy the following conditions while controlling the mass percentage of single chemical elements: p (Si+Mn). Times.10 4 Less than or equal to 150, preferably P (Si+Mn). Times.10 4 130 or less to improve toughness after heat treatment and reduce stress corrosion sensitivity. Each of the above chemicalThe elements are substituted into the numerical values before the mass percentage of the chemical elements.
Further, the low-cost quenched and tempered steel for continuous oil pipe according to the present invention further contains at least one of 0 < Nb.ltoreq.0.02% and 0 < Mo.ltoreq.0.02%.
Further, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, 0 < Nb.ltoreq.0.015%.
In the technical scheme of the invention, a proper amount of Nb element and/or Mo element can be added into the low-cost quenched and tempered steel for continuous oil pipe, and the performance of the steel can be further improved by adding the two elements.
Nb: in the steel for the low-cost quenched and tempered continuous oil pipe, nb is one of important elements of low-carbon microalloyed steel, nb in solid solution in the hot rolling process can be subjected to strain-induced precipitation to form Nb carbonitride, pinning grain boundaries inhibit growth of deformed austenite, and the deformed austenite can be transformed into a fine product with high dislocation density through controlled rolling and controlled cooling. After the steel strip is coiled, the solid-solution Nb is dispersed and precipitated in the matrix by the second phase particles NbC, thereby playing a role of precipitation strengthening. It should be noted that in the present invention, the Nb element content in the steel is not excessively high, nb is not a main reinforcing element, the addition of a large amount of Nb element to the steel results in an increase in tempering resistance of the steel, and the slab is liable to crack, thereby affecting the surface quality, and in addition, the excessive Nb element content in the steel deteriorates the weldability of the steel. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of Nb element can be controlled to be 0 < Nb.ltoreq.0.02%.
Of course, in some preferred embodiments, the mass percentage of Nb element may be controlled to be 0 < Nb.ltoreq.0.015% for better implementation.
Mo: in the low-cost quenched and tempered steel for continuous oil pipes, mo is a strong quenching element, so that ferrite transformation can be remarkably delayed, ferrite and pearlite can be effectively inhibited from forming, bainite transformation can be promoted, a matrix can be strengthened, and a finer structure can be obtained. In addition, mo can also overcome the tempering brittleness in the heat treatment process, and further has the effect of improving the heat treatment performance and the fatigue performance. It should be noted that in high-strength low-alloy steels, the Mo element content in the steel is not excessively high, and as the Mo element content in the steel increases, the plasticity of the steel decreases and the tempering resistance increases. Based on this, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of Mo element can be controlled to 0 < mo.ltoreq.0.02%.
Further, in the low-cost quenched and tempered steel for continuous oil pipe according to the present invention, the mass percentage of each chemical element satisfies at least one of the following:
C：0.20-0.30％；
Si：0.05-0.22％；
Mn：1.20-1.80％；
B：0.0025-0.0045％；
Cu：0.10-0.30％；
Ni：0.05-0.25％。
Accordingly, another object of the present invention is to provide a hot rolled steel strip for a low-cost quenched and tempered continuous oil pipe, which can be rolled in a wide process range to obtain a hot rolled steel strip for a low-strength continuous oil pipe, and which has a low yield ratio and good plastic workability, and can ensure smooth progress of a subsequent forming and welding process, and effectively reduce equipment loss.
It should be noted that, unlike the prior art which pursues high strength steel, the low-cost quenched and tempered steel strip for continuous oil pipe according to the present invention can be rolled in a wide process range to obtain a low-cost quenched and tempered steel strip for continuous oil pipe with relatively low strength, and the low-strength hot rolled steel strip can provide good workability and dimensional accuracy for the subsequent pipe manufacturing process, thereby ensuring smooth progress of the forming and welding process in the subsequent pipe manufacturing process and reducing equipment loss.
In order to achieve the above object, the present invention provides a hot rolled steel strip produced from the low-cost quenched and tempered steel for continuous oil pipe, wherein the microstructure matrix is ferrite + pearlite + bainite.
Further, in the hot rolled steel strip of the invention, the yield strength is 400-500MPa, the tensile strength is 550-650MPa, and the elongation is more than or equal to 24%.
Accordingly, it is still another object of the present invention to provide a steel pipe having ultra-high strength covering the currently most widely used CT90 and CT110 steel grades, up to the CT130 steel grade, which improves the structural uniformity of the pipe body and weld joint, and has excellent fatigue life and corrosion resistance, compared to conventional TMCP state coiled tubing.
In order to achieve the above purpose, the invention provides a steel pipe prepared from the hot rolled steel strip, wherein the microstructure matrix is tempered sorbite and bainite, and the phase proportion of tempered sorbite is more than or equal to 65%.
Accordingly, another object of the present invention is to provide a method for manufacturing the hot rolled steel strip, wherein the hot rolled steel strip manufactured by the method has low strength, high elongation, good plate shape, surface quality and dimensional accuracy, good plasticity, toughness and workability, and can ensure the smooth proceeding of the subsequent pipe forming and welding process, and effectively reduce the equipment loss.
In order to achieve the above object, the present invention provides a method for manufacturing a hot rolled steel strip, comprising the steps of:
(1) Smelting and continuous casting;
(2) And (3) hot rolling: controlling the heating temperature of the plate blank to be 1130-1280 ℃; the heat preservation time coefficient of the plate blank is 1.5-2.0min/mm; controlling the final rolling temperature to be 800-920 ℃; the coiling temperature is controlled to be 500-650 ℃.
In the method for manufacturing the hot rolled steel strip, in the step (1), conventional smelting methods such as electric furnace smelting or converter smelting can be adopted in the smelting process, and external refining can be carried out in a mode of RH vacuum degassing and LF desulfurization, so that molten steel is refined, wherein the 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.
In addition, in the step (2) of the method for manufacturing a hot rolled steel strip according to the present invention, it is necessary to control the slab heating temperature to 1130 to 1280 ℃ and the slab heat-retaining time coefficient to 1.5 to 2.0min/mm because: according to the invention, less Nb and Ti elements are added in the chemical composition design, and the solid solution strengthening effect of the invention has less contribution to the final strength of the steel strip, so that the slab can be heated at a lower heating temperature, on one hand, the energy consumption cost of a heating furnace can be reduced, and on the other hand, the iron scale on the surface of the slab can be reduced, thereby reducing the iron scale on the surface of the hot rolled steel strip and reducing the defects caused by residual iron scale in the subsequent processing. It should be noted, however, that the slab heating temperature is also not too low to impose a significant load on the rolling plant.
Accordingly, in the step (2) of the method for manufacturing a hot rolled steel strip according to the present invention, it is necessary to control the finishing temperature to 800 to 920 ℃, because: when the finishing temperature is too high and exceeds 920 ℃, austenite grains are coarsened obviously, and the steel strip is easy to generate serious banded structures or mixed crystal structures, so that the plasticity and the processing performance of the material are adversely affected; if the finish rolling temperature is lower than 800 ℃, the finish rolling temperature of the edge portion of the steel strip may be lower than Ar3, and the edge portion structure performance is very easy to be abnormal.
In addition, in the present invention, the winding temperature is controlled to be between 500 and 650 ℃ because: when the coiling temperature is lower than 500 ℃, the proportion of hard phase structures such as bainite in the structure is obviously increased, even partial martensite structures can appear, the strength level and fluctuation range of the steel strip are obviously increased, the performance stability and the shape are poor, and the subsequent pipe forming is not facilitated; if the coiling temperature exceeds 650 ℃, the strength is easy to be lower, a serious banded structure is easy to be generated, the existence of the banded structure can lead the mechanical property of the metal to be anisotropic, the direction of the banded structure is obviously better than the vertical direction, and the banded structure is easy to break from the junction in the tube making and forming process.
Further, in the method for manufacturing a hot rolled steel strip according to the present invention, in the step (1), the degree of superheat of continuous casting is controlled to 10 to 25 ℃, and/or the sedation time is not less than 6 minutes.
Accordingly, another object of the present invention is to provide a method for manufacturing the steel pipe, wherein the steel pipe manufactured by the method has ultra-high strength, the strength covers the most widely used CT90 and CT110, and the highest strength can reach the CT130 steel grade, and compared with the conventional TMCP state coiled tubing, the method improves the uniformity of the structural properties of the pipe body and the welding seam, and has excellent fatigue life and corrosion resistance.
In order to achieve the above object, the present invention provides a method for manufacturing the steel pipe, comprising the steps of:
(1) Smelting and continuous casting;
(2) Hot rolling to obtain a hot rolled steel strip: controlling the heating temperature of the plate blank to be 1130-1280 ℃; the heat preservation time coefficient of the plate blank is 1.5-2.0min/mm; controlling the final rolling temperature to be 800-920 ℃; the coiling temperature is controlled to be 500-650 ℃;
(3) Acid washing;
(4) Making a tube;
(5) Heat treatment, which comprises three steps of preheating, induction quenching and tempering, wherein in the induction quenching step, the quenching temperature is controlled to be higher than Ac3 temperature, and the cooling speed is 30-80 ℃/s; wherein in the tempering step, the tempering temperature is controlled to be 500-650 ℃, and cooling is performed after tempering;
(6) And (5) coiling.
In the technical scheme of the invention, in the manufacturing process for manufacturing the steel pipe, the heat treatment process in the step (5) is optimized and improved in a related manner, so that the steel pipe with high strength and capability of meeting the requirements of underground operation of more deep wells and long horizontal sections can be obtained.
In the prior art, the weld joint of the conventional continuous oil pipe has great difference with the structural performance of the pipe body, and the fatigue performance of the weld joint is in a descending trend relative to the pipe body along with the rising of the strength, so that the fatigue performance becomes a bottleneck for limiting the overall performance of the high-strength continuous oil pipe. The conventional coiled tubing is usually subjected to simple stress relief annealing only after welding, and the manufacturing method of the steel tube optimizes the heat treatment process, adopts a plurality of heat treatment processes of the whole tube in the heat treatment step, can greatly reduce the structural performance difference between the welding line and the tube body, and reduces the adverse effect of the welding line on the overall performance, thereby improving the strength, simultaneously obtaining good fatigue life and corrosion resistance, and improving the service life of the coiled tubing.
According to the invention, through the heat treatment process of the whole pipe, the influence of the difference of the steel belt performance on the performance of the final coiled tubing finished product is reduced, the residual stress of the pipe body and the welding seam position in the pipe making process is weakened, and the reliability of the coiled tubing is improved.
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 pickling step, the winding temperature is controlled to be less than or equal to 75 ℃, the pickling temperature is controlled to be between 60 and 75 ℃, and the pickling time is controlled to be 45 to 100 seconds.
Correspondingly, in the step (4) of the steel pipe manufacturing method, the steel belt can be longitudinally cut into the required width of the continuous oil pipe in the pipe manufacturing stage, then the butt joint of the steel belt is finished in the length direction in an end welding mode, after the welded steel belt is bent and molded by a molding unit, the welding of a straight welding seam can be finished by utilizing high-frequency induction welding, the required outer diameter size of the connecting pipe is obtained through sizing treatment, and at the moment, the continuous oil pipe still maintains TMCP state tissues.
In the step (5) of the steel pipe manufacturing method of the present invention, in the heat treatment step, the whole pipe heat treatment of the coiled tubing includes three steps of preheating, induction hardening and tempering. In the induction quenching step, the pipe body can be heated to a temperature above Ac3 (the final temperature of ferrite to austenite in the heating process) through an induction heating furnace and kept for a sufficient time, so that the ferrite or carbide is effectively ensured to be completely decomposed and the whole pipe body is uniformly transparent to heat. And (3) spraying and cooling after heating, adjusting the water flow pressure and speed according to the product size specification and the ambient temperature, and controlling the cooling speed to be 30-80 ℃/s so as to ensure that the whole pipe wall finishes tissue transformation in a short time.
Accordingly, in the tempering step of the present invention, the tube body may be rapidly heated to 500-650 ℃ by an induction heating furnace for tempering. This is because: excessive tempering temperatures can cause portions of the martensite to transform to higher austenite, which tends to transform to a brittle phase, thereby reducing the toughness and fatigue life of the tube. On the other hand, if the tempering temperature is lower than 500 ℃, the dislocation quenched structure recovery is not completed, and the toughness and fatigue life of the tube are also greatly reduced. Therefore, the tempering temperature needs to be controlled between 500-650 ℃.
In addition, in the step (6) of the method for manufacturing a steel pipe according to the present invention, a coiling operation is required, and after the heat treatment step in the step (5), the heat treated steel pipe can be coiled on a reel by a coiling machine to obtain a coiled tubing finished product, wherein the final microstructure of the prepared finished coiled tubing is mainly tempered sorbite, and the rest is bainite and other tissues. The weld joint and the base metal of the finished coiled tubing are uniformly refined in structure, and the finished coiled tubing has high strength, good plasticity and toughness.
Further, in the method for manufacturing a steel pipe according to the present invention, in the preheating step in the step (5), the pipe is heated in three stages, the first stage is heated to 450 to 500 ℃, the second stage is heated to 650 to 700 ℃, and the third stage is heated to 800 to 850 ℃.
In the technical scheme, before the induction quenching operation, a preheating step is arranged, the pipe body can be subjected to three-section heating through a preheating zone, the first section is heated to 450-500 ℃, the second section is heated to 650-700 ℃, the third section is heated to 800-850 ℃, through the step heating preheating, the temperature distribution along the pipe body along the section can be homogenized, the problem of size deformation can be reduced, relatively fine and uniform austenite grains can be obtained, and the austenitizing heating uniformity is improved.
Further, in the method for producing a steel pipe according to the present invention, in the step (5), water spray cooling is performed after tempering is completed and air cooling is performed to 150 ℃.
Compared with the prior art, the low-cost quenched and tempered steel for continuous oil pipes, the hot rolled steel strip, the steel pipe and the manufacturing method thereof have the following advantages:
the steel for the low-cost quenched and tempered continuous oil pipe adopts a composition design thought different from that of a conventional quenched and tempered continuous oil pipe through reasonable chemical composition system design, and effectively controls alloy cost through chemical composition design taking carbon and manganese reinforcement as main materials and multiple microalloys as auxiliary materials.
Compared with the conventional components, the invention reduces the content of Mo and Cr elements in the design to reduce the hardness after tempering; correspondingly, the invention also ensures the hardenability of the material by adding a proper amount of B element; the invention ensures the corrosion resistance of the steel by adding a proper amount of Cr, cu and Ni elements. In the low-cost quenched and tempered steel for continuous oil pipe, V element is not added in the steel, and Nb and Ti with lower content are adopted, so that the production cost is reduced while the performance of the steel is ensured.
In addition, the invention also adopts a low-sulfur design to ensure that the developed steel has good impact toughness and fatigue resistance; the steel for the quenched and tempered continuous oil pipe is also controlled to be added with Si element with lower content so as to remove iron scales in the rolling process and improve the surface quality.
The steel for the quenched and tempered continuous oil pipe can be rolled in a wider process range to obtain a hot rolled steel strip by adopting the optimized process design, and the prepared hot rolled steel strip has the advantages of lower strength, higher elongation, good plate shape, surface quality and dimensional accuracy, good plasticity, toughness and processability, can ensure the smooth proceeding of the subsequent pipe forming and welding process, and effectively reduces equipment loss.
In addition, the hot rolled steel strip can be further used for preparing the steel pipe provided by the invention, has ultrahigh strength, the strength of the steel pipe covers the most widely applied CT90 and CT110, the highest steel grade can reach CT130, and compared with a conventional TMCP state continuous oil pipe, the steel pipe improves the uniformity of the structural properties of a pipe body and a welding seam, and has excellent fatigue life and corrosion resistance.
Correspondingly, in the manufacturing method of the steel pipe, a special heat treatment process is adopted to carry out on-line whole-pipe heat treatment on the steel pipe, and the high-strength continuous oil pipe with adjustable performance can be obtained by adjusting the heat treatment process, wherein the strength of the continuous oil pipe can reach the CT130 steel grade at the highest while meeting the CT90 and CT110 steel grades, and the method can be effectively applied to the operation fields of oil-gas field drilling, well repair, well completion and the like, and can meet the underground operation demands of more deep wells and long horizontal sections.
It should be noted that according to the components and the process designed by the invention, the hot rolled steel strips with the same component can be matched with different heat treatment processes to manufacture continuous oil pipes with different strength grades, thereby simplifying the purchasing and warehouse preparation processes and improving the production management efficiency.
Detailed Description
The low-cost quenched and tempered steel for continuous oil pipe, 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 specific examples, but the explanation and illustration should not be construed as unduly limiting the technical scheme of the present invention.
Examples 1 to 6
Tables 1-1 and 1-2 list the mass percentages of each chemical element in the low-cost quenched and tempered steel for continuous oil pipes of examples 1-6.
Table 1-1 (wt.%), balance Fe and other unavoidable impurities
Tables 1-2.
Numbering device 75.5-0.094×650+6.66(C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15) P(Si+Mn)×10 4
Example 1 19 80
Example 2 19 56
Example 3 18 113
Example 4 19 83
Example 5 18 141
Example 6 17 53
Note that: in the above table, "75.5-0.094X150+6.66 (C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15)" and "P (Si+Mn). Times.10 ] 4 Each element in the formula of the' represents a numerical value before the mass percent of the corresponding element.
The low-cost quenched and tempered steel for continuous oil pipe according to examples 1 to 6 of the present invention can be used to produce a corresponding hot rolled steel strip, and examples 1 to 6 to 1 hereinafter represent hot rolled steel strips produced by using the quenched and tempered steel for continuous oil pipe of examples 1 to 6.
In the present invention, the hot rolled steel strip of each of examples 1-1 to 6-1 was produced by the following steps:
(1) Smelting and continuous casting: in the smelting step, adopting an electric furnace and a converter for smelting, and carrying out RH vacuum degassing and LF desulfurization by external refining, wherein the time of controlling the vacuum degassing is 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) And (3) hot rolling: controlling the heating temperature of the plate blank to be 1130-1280 ℃; the heat preservation time coefficient of the plate blank is 1.5-2.0min/mm; controlling the final rolling temperature to be 800-920 ℃; the coiling temperature is controlled to be 500-650 ℃.
In the present invention, the chemical compositions and the related process parameters of the hot rolled steel strips of examples 1-1 to 6-1 meet the control requirements of the design specifications of the present invention.
Table 2 sets forth specific process parameters in the manufacturing methods of hot rolled steel strips of examples 1-1 to 6-1.
Table 2.
The hot rolled steel strips of examples 1-1 to 6-1 were sampled to obtain samples, and the hot rolled steel strips of each example were tested for the relevant properties such as yield strength and elongation, respectively, to obtain test data for evaluating the mechanical properties thereof, and the relevant mechanical properties were tested as shown in the following Table 3.
Table 3 sets forth the relevant mechanical properties of the hot rolled steel strips of examples 1-1 to 6-1.
Table 3.
As can be seen from the observation of the hot rolled steel strip of each example, the hot rolled steel strip of each example with a microstructure matrix of ferrite, pearlite and bainite can be obtained by the rolling process according to the design composition of the present invention. As can be seen from a combination of tables 2 and 3, the hot rolled steel strips of examples 1-1 to 6-1 all have yield strengths of 405-497MPa, tensile strengths of 560-650MPa, and elongation of 24% or more. The hot rolled steel strip of each embodiment has lower strength and higher elongation, has good plate shape, surface quality and dimensional accuracy, has good plasticity, toughness and processability, and is very beneficial to the subsequent pipe making process.
After the mechanical properties of the hot rolled steel strips of examples 1-1 to 6-1 were detected, the hot rolled steel strips of each example may be reworked to produce steel pipes, respectively, and the produced example steel pipes are shown in examples 1-2 to 6-2, respectively.
In the present invention, the steel pipes of examples 1-2 to 6-2 were each produced by the following steps:
(1) Smelting and continuous casting: in the smelting step, adopting an electric furnace and a converter for smelting, and carrying out RH vacuum degassing and LF desulfurization by external refining, wherein the time of controlling the vacuum degassing is more than or equal to 3min; wherein in the continuous casting step, the superheat degree of continuous casting is controlled to be 10-25 ℃, and the sedation time is more than or equal to 6min.
(2) Hot rolling to obtain a hot rolled steel strip: controlling the heating temperature of the plate blank to be 1130-1280 ℃; the heat preservation time coefficient of the plate blank is 1.5-2.0min/mm; controlling the final rolling temperature to be 800-920 ℃; the coiling temperature is controlled to be 500-650 ℃.
(3) Acid washing: controlling the coiling temperature to 70 ℃, controlling the pickling temperature to 65 ℃ and the pickling time to 80s, wherein the thickness of the obtained steel strip is less than or equal to 7mm;
(4) And (3) pipe manufacturing: the steel strip is longitudinally cut into the required width of the quenched and tempered continuous oil pipe, the butt joint of the steel strip is completed in the length direction in an end welding mode, after the welded steel strip is subjected to bending molding by a molding unit, the welding of a straight weld joint is completed by utilizing high-frequency induction welding, the required outside diameter of the continuous oil pipe is obtained through sizing treatment, and the quenched and tempered continuous oil pipe still maintains TMCP state tissues at the moment.
(5) The heat treatment comprises three steps of preheating, induction quenching and tempering, wherein in the preheating step, the pipe body can be heated in three sections, the first section is heated to 450-500 ℃, the second section is heated to 650-700 ℃, and the third section is heated to 800-850 ℃; wherein in the induction quenching step, the quenching temperature is controlled to be higher than Ac3 temperature, and the cooling speed is 30-80 ℃/s; in the tempering step, the tempering temperature is controlled to be 500-650 ℃, and water spray cooling can be performed after the tempering is finished and the air cooling is performed to below 150 ℃;
(6) And (5) coiling.
It should be noted that the chemical components and the related process parameters of the steel pipes of examples 1-2 to 6-2 all meet the design specification control requirements of the present invention, and the process parameters of the steel pipes of examples 1-2 to 6-2 in step (1) and step (2) are identical to those listed in table 2.
In the invention, the steel strip is required to be pickled after the hot rolling operation is finished, in the pickling step of the step (3), the winding temperature of each embodiment is controlled to be 70 ℃, the pickling temperature is controlled to be 65 ℃, the pickling time is controlled to be 80 seconds, and after the hot rolled steel strip is pickled and oiled, hot rolled oxide skin is removed, so that the hot rolled pickled steel strip with good surface quality is obtained, the thickness of the hot rolled pickled steel strip is 3.96mm, the width of the hot rolled steel strip is 1.2m, and the total coil weight is more than or equal to 16 tons. Accordingly, in the pipe manufacturing stage, a coiled tubing with an outer diameter of 38.1mm can be obtained through sizing treatment, and then the coiled tubing enters a heat treatment process.
Table 4 shows specific process parameters in the above-described manufacturing methods for the steel pipes of examples 1-2 to 6-2.
Table 4.
The steel pipes of examples 1-2 to 6-2 were sampled and tested for the yield strength, elongation and the like of the steel pipes of each example, respectively, to thereby obtain test data for evaluating the mechanical properties thereof, respectively, and the test data for the related mechanical properties are shown in Table 5.
Table 5 lists the relevant mechanical properties parameters for the steel pipes of examples 1-2 to 6-2.
Table 5.
As can be seen by referring to the mechanical properties of the hot rolled steel strip and the steel pipe shown in tables 3 and 5, the hot rolled steel strip of example 1-1 and the hot rolled steel strip of example 3-1 can reach CT90 grade after quenching and tempering at 650 ℃; the hot rolled steel strip of example 4-1 and the hot rolled steel strip of example 6-1 can reach CT110 steel grade after quenching and tempering at 580 ℃; the hot rolled steel strip of example 2-1 and the hot rolled steel strip of example 5-1 can reach CT130 steel grade after quenching and tempering at 500 ℃.
Therefore, in the process of manufacturing the steel pipes of the embodiments 1-2 to 6-2, the tensile property and hardness of the steel pipes can meet the requirements of CT90-CT130 steel grade by controlling different heat treatment processes, the properties of coiled tubing obtained by heat treatment of steel belts with different strengths at the same temperature after pipe manufacture are similar, and the hardness difference among base materials, welding seams and heat affected zones is obviously smaller.
Therefore, according to the chemical composition design of the steel for the low-cost quenched and tempered continuous oil pipe, rolling can be performed in a wider process interval, and the low-strength hot rolled steel strip with the yield strength of 400-500MPa, the tensile strength of 550-650MPa and the elongation of more than or equal to 24% can be effectively prepared.
Correspondingly, the manufactured hot rolled steel strip is subjected to acid washing, pipe forming and welding, and then is subjected to special online heat treatment, so that the structural uniformity of the continuous oil pipe can be effectively improved, the fatigue life and the corrosion resistance of the continuous oil pipe are improved, the high-strength continuous oil pipe with the structure mainly comprising tempered sorbite and bainite is finally obtained, and the performance of the continuous oil pipe can cover the CT90-CT130 steel grade through the adjustment of components and processes.
From the above, it can be seen that the low-cost quenched and tempered coiled tubing of the present invention has various advantages over conventional coiled tubing by performing on-line heat treatment on the whole tubing after tubing. On one hand, the coiled tubing products with different steel grades can be obtained by adopting the same raw materials and adjusting the heat treatment process, so that the purchasing and warehouse preparation processes are simplified, and the production management efficiency is improved. On the other hand, the steel can replace CT90 and CT110 steel grades which are most widely applied at present after pipe making, the highest strength can reach CT130 steel grade, and the underground operation requirements of different depths can be met.
In addition, in the manufacturing method of the steel pipe, the structural property uniformity, the fatigue life and the corrosion resistance of the continuous oil pipe are improved, the reliability and the service life of the continuous oil pipe are improved, the failure risk is reduced, and the operation efficiency of an oil well is improved by optimizing the design heat treatment process. Therefore, the high-strength coiled tubing designed and manufactured by adopting the technical scheme of the invention has the advantages besides higher strength, accords with the development trend of the coiled tubing, can be effectively applied to the operation fields of oil and gas field drilling, well repair, well completion and the like, can meet the underground operation requirements of more deep wells and long horizontal sections, and has better market application prospect.
It should be noted that the combination of the technical features in the present invention is not limited to the combination described in the claims or the combination described in the specific embodiments, and all the technical features described in the present invention may be freely combined or combined in any manner unless contradiction occurs between them.
In addition, it should be noted that the above-listed 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 will be apparent to those skilled in the art from the present disclosure, and it is intended to be within the scope of the present invention.

Claims (12)

1. The steel for the low-cost quenched and tempered continuous oil pipe is characterized by comprising the following chemical elements in percentage by mass:
c:0.18-0.32%, si:0.05-0.30%, mn:0.90-2.50%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, cr:0.10-0.50%, ti:0.008-0.025%, cu:0.10-0.40%, ni:0.05-0.30%, B:0.002-0.005%, ca:0.001-0.004%, al:0.01-0.05%, N is more than 0 and less than or equal to 0.007%, and the balance is Fe and other unavoidable impurities;
the mass percentages of the chemical elements are as follows: 75.5-0.094X150+6.66 (C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15). Ltoreq.22; p (Si+Mn). Times.10 4 Not more than 150, wherein each element represents a corresponding elementNumerical values before the mass percent of the element;
the yield strength of the hot rolled steel strip prepared from the low-cost quenched and tempered continuous oil pipe steel is 400-500MPa, the tensile strength is 550-650MPa, and the elongation is more than or equal to 24%; the tensile property and the hardness of the steel pipe prepared from the low-cost quenched and tempered continuous oil pipe steel meet the requirements of CT90-CT130 steel grade.
2. The low-cost quenched and tempered steel for continuous oil pipe as claimed in claim 1, wherein the contents of each chemical element in mass percent are as follows: 75.5-0.094X150+6.66 (C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15). Ltoreq.20; and/or
P(Si+Mn)×10 4 And less than or equal to 130, wherein each element represents a numerical value before the mass percent of the corresponding element.
3. The low-cost quenched and tempered steel for continuous oil use as claimed in claim 1, further comprising at least one of 0 < Nb.ltoreq.0.02% and 0 < Mo.ltoreq.0.02%.
4. The low-cost quenched and tempered steel for continuous oil pipe as claimed in claim 3, wherein 0 < Nb.ltoreq.0.015%.
5. The low-cost quenched and tempered steel for continuous oil pipe as claimed in claim 1, wherein the contents of each chemical element in mass% satisfy at least one of the following:
C：0.20-0.30％；
Si：0.05-0.22％；
Mn：1.20-1.80％；
B：0.0025-0.0045％；
Cu：0.10-0.30％；
Ni：0.05-0.25％。
6. A hot rolled steel strip produced using the low cost temper continuous oil tube steel as claimed in any one of claims 1 to 5, wherein the microstructure matrix is ferrite + pearlite + bainite.
7. The hot rolled steel strip as claimed in claim 6 having a yield strength between 400 and 500MPa, a tensile strength between 550 and 650MPa and an elongation of greater than or equal to 24%.
8. A steel pipe produced from the hot rolled steel strip as claimed in any one of claims 6 or 7 wherein the microstructure matrix is tempered sorbite + bainite and wherein the phase proportion of tempered sorbite is equal to or greater than 65%.
9. A method of manufacturing hot rolled steel strip as claimed in claim 6 or claim 7 comprising the steps of:
(1) Smelting and continuous casting;
(2) And (3) hot rolling: controlling the heating temperature of the plate blank to be 1130-1280 ℃; the heat preservation time coefficient of the plate blank is 1.5-2.0min/mm; controlling the final rolling temperature to be 800-920 ℃; the coiling temperature is controlled to be 500-650 ℃.
10. The method of producing hot rolled steel strip as claimed in claim 9 wherein in step (1), the degree of superheat in continuous casting is controlled to 10 to 25 ℃ and/or the sedation time is not less than 6 minutes.
11. A method of manufacturing a steel pipe according to claim 8, comprising the steps of:
(1) Smelting and continuous casting;
(2) Hot rolling to obtain a hot rolled steel strip: controlling the heating temperature of the plate blank to be 1130-1280 ℃; the heat preservation time coefficient of the plate blank is 1.5-2.0min/mm; controlling the final rolling temperature to be 800-920 ℃; the coiling temperature is controlled to be 500-650 ℃;
(3) Acid washing;
(4) Making a tube;
(5) Heat treatment, which comprises three steps of preheating, induction quenching and tempering, wherein in the induction quenching step, the quenching temperature is controlled to be higher than Ac3 temperature, and the cooling speed is 30-80 ℃/s; wherein in the tempering step, the tempering temperature is controlled to be 500-650 ℃, and cooling is performed after tempering; wherein in the preheating step, the pipe body is heated in three sections, the first section is heated to 450-500 ℃, the second section is heated to 650-700 ℃, and the third section is heated to 800-850 ℃;
(6) And (5) coiling.
12. The method of producing a steel pipe according to claim 11, wherein in step (5), water spray cooling is performed after tempering is completed and air cooling is performed to 150 ℃.
CN202110613116.2A 2021-06-02 2021-06-02 Low-cost quenched and tempered steel for continuous oil pipe, hot rolled steel strip, steel pipe and manufacturing method thereof Active CN115433870B (en)

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CN101634001A (en) * 2008-07-24 2010-01-27 宝山钢铁股份有限公司 CT90-class steel for continuous oil pipe and method for manufacturing same
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CN104046918A (en) * 2013-03-14 2014-09-17 特纳瑞斯盘管有限公司 High Performance Material For Coiled Tubing Applications And The Method Of Producing The Same
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CN111441000A (en) * 2020-03-30 2020-07-24 江阴兴澄特种钢铁有限公司 690 MPa-yield-strength low-yield-ratio high-strength steel plate and manufacturing method thereof

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CN101353765A (en) * 2007-07-23 2009-01-28 宝山钢铁股份有限公司 Steel for CT80 grade coiled tubing, and manufacturing method and use thereof
CN101634001A (en) * 2008-07-24 2010-01-27 宝山钢铁股份有限公司 CT90-class steel for continuous oil pipe and method for manufacturing same
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